Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

59 files changed, 30398 insertions, 0 deletions

diff --git a/third_party/rust/bindgen/.cargo-checksum.json b/third_party/rust/bindgen/.cargo-checksum.json
new file mode 100644
index 0000000000..24fa58273e
--- /dev/null
+++ b/third_party/rust/bindgen/.cargo-checksum.json
@@ -0,0 +1 @@
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diff --git a/third_party/rust/bindgen/Cargo.toml b/third_party/rust/bindgen/Cargo.toml
new file mode 100644
index 0000000000..c4f5f568ae
--- /dev/null
+++ b/third_party/rust/bindgen/Cargo.toml
@@ -0,0 +1,151 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+rust-version = "1.60.0"
+name = "bindgen"
+version = "0.69.4"
+authors = [
+    "Jyun-Yan You <jyyou.tw@gmail.com>",
+    "Emilio Cobos Álvarez <emilio@crisal.io>",
+    "Nick Fitzgerald <fitzgen@gmail.com>",
+    "The Servo project developers",
+]
+build = "build.rs"
+description = "Automatically generates Rust FFI bindings to C and C++ libraries."
+homepage = "https://rust-lang.github.io/rust-bindgen/"
+documentation = "https://docs.rs/bindgen"
+readme = "README.md"
+keywords = [
+    "bindings",
+    "ffi",
+    "code-generation",
+]
+categories = [
+    "external-ffi-bindings",
+    "development-tools::ffi",
+]
+license = "BSD-3-Clause"
+repository = "https://github.com/rust-lang/rust-bindgen"
+
+[package.metadata.docs.rs]
+features = ["experimental"]
+
+[package.metadata.release]
+pre-release-hook = [
+    "../node_modules/doctoc/doctoc.js",
+    "../CHANGELOG.md",
+]
+release = true
+
+[[package.metadata.release.pre-release-replacements]]
+file = "../CHANGELOG.md"
+replace = """
+# Unreleased
+## Added
+## Changed
+## Removed
+## Fixed
+## Security
+
+# {{version}} ({{date}})"""
+search = "# Unreleased"
+
+[lib]
+name = "bindgen"
+path = "lib.rs"
+
+[dependencies.annotate-snippets]
+version = "0.9.1"
+features = ["color"]
+optional = true
+
+[dependencies.bitflags]
+version = "2.2.1"
+
+[dependencies.cexpr]
+version = "0.6"
+
+[dependencies.clang-sys]
+version = "1"
+features = ["clang_6_0"]
+
+[dependencies.itertools]
+version = ">=0.10,<0.13"
+default-features = false
+
+[dependencies.lazy_static]
+version = "1"
+
+[dependencies.lazycell]
+version = "1"
+
+[dependencies.log]
+version = "0.4"
+optional = true
+
+[dependencies.prettyplease]
+version = "0.2.7"
+features = ["verbatim"]
+optional = true
+
+[dependencies.proc-macro2]
+version = "1"
+default-features = false
+
+[dependencies.quote]
+version = "1"
+default-features = false
+
+[dependencies.regex]
+version = "1.5.1"
+features = [
+    "std",
+    "unicode-perl",
+]
+default-features = false
+
+[dependencies.rustc-hash]
+version = "1.0.1"
+
+[dependencies.shlex]
+version = "1"
+
+[dependencies.syn]
+version = "2.0"
+features = [
+    "full",
+    "extra-traits",
+    "visit-mut",
+]
+
+[dependencies.which]
+version = "4.2.1"
+optional = true
+default-features = false
+
+[features]
+__cli = []
+__testing_only_extra_assertions = []
+__testing_only_libclang_16 = []
+__testing_only_libclang_9 = []
+default = [
+    "logging",
+    "prettyplease",
+    "runtime",
+    "which-rustfmt",
+]
+experimental = ["dep:annotate-snippets"]
+logging = ["dep:log"]
+runtime = ["clang-sys/runtime"]
+static = ["clang-sys/static"]
+which-rustfmt = ["dep:which"]
diff --git a/third_party/rust/bindgen/LICENSE b/third_party/rust/bindgen/LICENSE
new file mode 100644
index 0000000000..62f55f45a1
--- /dev/null
+++ b/third_party/rust/bindgen/LICENSE
@@ -0,0 +1,29 @@
+BSD 3-Clause License
+
+Copyright (c) 2013, Jyun-Yan You
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+* Neither the name of the copyright holder nor the names of its
+  contributors may be used to endorse or promote products derived from
+  this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/third_party/rust/bindgen/README.md b/third_party/rust/bindgen/README.md
new file mode 100644
index 0000000000..620ad0ab94
--- /dev/null
+++ b/third_party/rust/bindgen/README.md
@@ -0,0 +1,89 @@
+[![crates.io](https://img.shields.io/crates/v/bindgen.svg)](https://crates.io/crates/bindgen)
+[![docs.rs](https://docs.rs/bindgen/badge.svg)](https://docs.rs/bindgen/)
+
+# `bindgen`
+
+**`bindgen` automatically generates Rust FFI bindings to C (and some C++) libraries.**
+
+For example, given the C header `doggo.h`:
+
+```c
+typedef struct Doggo {
+    int many;
+    char wow;
+} Doggo;
+
+void eleven_out_of_ten_majestic_af(Doggo* pupper);
+```
+
+`bindgen` produces Rust FFI code allowing you to call into the `doggo` library's
+functions and use its types:
+
+```rust
+/* automatically generated by rust-bindgen 0.99.9 */
+
+#[repr(C)]
+pub struct Doggo {
+    pub many: ::std::os::raw::c_int,
+    pub wow: ::std::os::raw::c_char,
+}
+
+extern "C" {
+    pub fn eleven_out_of_ten_majestic_af(pupper: *mut Doggo);
+}
+```
+
+## Users Guide
+
+[📚 Read the `bindgen` users guide here! 📚](https://rust-lang.github.io/rust-bindgen)
+
+## MSRV
+
+The `bindgen` minimum supported Rust version is **1.60.0**.
+
+The `bindgen-cli` minimum supported Rust version is **1.64.0**.
+
+No MSRV bump policy has been established yet, so MSRV may increase in any release.
+
+The MSRV is the minimum Rust version that can be used to *compile* each crate. However, `bindgen` and `bindgen-cli` can generate bindings that are compatible with Rust versions below the current MSRV.
+
+Most of the time, the `bindgen-cli` crate will have a more recent MSRV than `bindgen` as crates such as `clap` require it. 
+
+## API Reference
+
+[API reference documentation is on docs.rs](https://docs.rs/bindgen)
+
+## Environment Variables
+
+In addition to the [library API](https://docs.rs/bindgen) and [executable command-line API][bindgen-cmdline],
+`bindgen` can be controlled through environment variables.
+
+End-users should set these environment variables to modify `bindgen`'s behavior without modifying the source code of direct consumers of `bindgen`.
+
+- `BINDGEN_EXTRA_CLANG_ARGS`: extra arguments to pass to `clang`
+    - Arguments are whitespace-separated
+    - Use shell-style quoting to pass through whitespace
+    - Examples:
+        - Specify alternate sysroot: `--sysroot=/path/to/sysroot`
+        - Add include search path with spaces: `-I"/path/with spaces"`
+- `BINDGEN_EXTRA_CLANG_ARGS_<TARGET>`: similar to `BINDGEN_EXTRA_CLANG_ARGS`,
+   but used to set per-target arguments to pass to clang. Useful to set system include
+   directories in a target-specific way in cross-compilation environments with multiple targets.
+   Has precedence over `BINDGEN_EXTRA_CLANG_ARGS`.
+
+Additionally, `bindgen` uses `libclang` to parse C and C++ header files.
+To modify how `bindgen` searches for `libclang`, see the [`clang-sys` documentation][clang-sys-env].
+For more details on how `bindgen` uses `libclang`, see the [`bindgen` users guide][bindgen-book-clang].
+
+## Releases
+
+We don't follow a specific release calendar, but if you need a release please
+file an issue requesting that (ping `@emilio` for increased effectiveness).
+
+## Contributing
+
+[See `CONTRIBUTING.md` for hacking on `bindgen`!](./CONTRIBUTING.md)
+
+[bindgen-cmdline]: https://rust-lang.github.io/rust-bindgen/command-line-usage.html
+[clang-sys-env]: https://github.com/KyleMayes/clang-sys#environment-variables
+[bindgen-book-clang]: https://rust-lang.github.io/rust-bindgen/requirements.html#clang
diff --git a/third_party/rust/bindgen/build.rs b/third_party/rust/bindgen/build.rs
new file mode 100644
index 0000000000..8407ceae8f
--- /dev/null
+++ b/third_party/rust/bindgen/build.rs
@@ -0,0 +1,29 @@
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+fn main() {
+    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
+
+    let mut dst =
+        File::create(Path::new(&out_dir).join("host-target.txt")).unwrap();
+    dst.write_all(env::var("TARGET").unwrap().as_bytes())
+        .unwrap();
+
+    // On behalf of clang_sys, rebuild ourselves if important configuration
+    // variables change, to ensure that bindings get rebuilt if the
+    // underlying libclang changes.
+    println!("cargo:rerun-if-env-changed=LLVM_CONFIG_PATH");
+    println!("cargo:rerun-if-env-changed=LIBCLANG_PATH");
+    println!("cargo:rerun-if-env-changed=LIBCLANG_STATIC_PATH");
+    println!("cargo:rerun-if-env-changed=BINDGEN_EXTRA_CLANG_ARGS");
+    println!(
+        "cargo:rerun-if-env-changed=BINDGEN_EXTRA_CLANG_ARGS_{}",
+        std::env::var("TARGET").unwrap()
+    );
+    println!(
+        "cargo:rerun-if-env-changed=BINDGEN_EXTRA_CLANG_ARGS_{}",
+        std::env::var("TARGET").unwrap().replace('-', "_")
+    );
+}
diff --git a/third_party/rust/bindgen/callbacks.rs b/third_party/rust/bindgen/callbacks.rs
new file mode 100644
index 0000000000..c22ba975dd
--- /dev/null
+++ b/third_party/rust/bindgen/callbacks.rs
@@ -0,0 +1,213 @@
+//! A public API for more fine-grained customization of bindgen behavior.
+
+pub use crate::ir::analysis::DeriveTrait;
+pub use crate::ir::derive::CanDerive as ImplementsTrait;
+pub use crate::ir::enum_ty::{EnumVariantCustomBehavior, EnumVariantValue};
+pub use crate::ir::int::IntKind;
+use std::fmt;
+
+/// An enum to allow ignoring parsing of macros.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum MacroParsingBehavior {
+    /// Ignore the macro, generating no code for it, or anything that depends on
+    /// it.
+    Ignore,
+    /// The default behavior bindgen would have otherwise.
+    Default,
+}
+
+impl Default for MacroParsingBehavior {
+    fn default() -> Self {
+        MacroParsingBehavior::Default
+    }
+}
+
+/// A trait to allow configuring different kinds of types in different
+/// situations.
+pub trait ParseCallbacks: fmt::Debug {
+    #[cfg(feature = "__cli")]
+    #[doc(hidden)]
+    fn cli_args(&self) -> Vec<String> {
+        vec![]
+    }
+
+    /// This function will be run on every macro that is identified.
+    fn will_parse_macro(&self, _name: &str) -> MacroParsingBehavior {
+        MacroParsingBehavior::Default
+    }
+
+    /// This function will run for every extern variable and function. The returned value determines
+    /// the name visible in the bindings.
+    fn generated_name_override(
+        &self,
+        _item_info: ItemInfo<'_>,
+    ) -> Option<String> {
+        None
+    }
+
+    /// This function will run for every extern variable and function. The returned value determines
+    /// the link name in the bindings.
+    fn generated_link_name_override(
+        &self,
+        _item_info: ItemInfo<'_>,
+    ) -> Option<String> {
+        None
+    }
+
+    /// The integer kind an integer macro should have, given a name and the
+    /// value of that macro, or `None` if you want the default to be chosen.
+    fn int_macro(&self, _name: &str, _value: i64) -> Option<IntKind> {
+        None
+    }
+
+    /// This will be run on every string macro. The callback cannot influence the further
+    /// treatment of the macro, but may use the value to generate additional code or configuration.
+    fn str_macro(&self, _name: &str, _value: &[u8]) {}
+
+    /// This will be run on every function-like macro. The callback cannot
+    /// influence the further treatment of the macro, but may use the value to
+    /// generate additional code or configuration.
+    ///
+    /// The first parameter represents the name and argument list (including the
+    /// parentheses) of the function-like macro. The second parameter represents
+    /// the expansion of the macro as a sequence of tokens.
+    fn func_macro(&self, _name: &str, _value: &[&[u8]]) {}
+
+    /// This function should return whether, given an enum variant
+    /// name, and value, this enum variant will forcibly be a constant.
+    fn enum_variant_behavior(
+        &self,
+        _enum_name: Option<&str>,
+        _original_variant_name: &str,
+        _variant_value: EnumVariantValue,
+    ) -> Option<EnumVariantCustomBehavior> {
+        None
+    }
+
+    /// Allows to rename an enum variant, replacing `_original_variant_name`.
+    fn enum_variant_name(
+        &self,
+        _enum_name: Option<&str>,
+        _original_variant_name: &str,
+        _variant_value: EnumVariantValue,
+    ) -> Option<String> {
+        None
+    }
+
+    /// Allows to rename an item, replacing `_original_item_name`.
+    fn item_name(&self, _original_item_name: &str) -> Option<String> {
+        None
+    }
+
+    /// This will be called on every header filename passed to (`Builder::header`)[`crate::Builder::header`].
+    fn header_file(&self, _filename: &str) {}
+
+    /// This will be called on every file inclusion, with the full path of the included file.
+    fn include_file(&self, _filename: &str) {}
+
+    /// This will be called every time `bindgen` reads an environment variable whether it has any
+    /// content or not.
+    fn read_env_var(&self, _key: &str) {}
+
+    /// This will be called to determine whether a particular blocklisted type
+    /// implements a trait or not. This will be used to implement traits on
+    /// other types containing the blocklisted type.
+    ///
+    /// * `None`: use the default behavior
+    /// * `Some(ImplementsTrait::Yes)`: `_name` implements `_derive_trait`
+    /// * `Some(ImplementsTrait::Manually)`: any type including `_name` can't
+    ///   derive `_derive_trait` but can implemented it manually
+    /// * `Some(ImplementsTrait::No)`: `_name` doesn't implement `_derive_trait`
+    fn blocklisted_type_implements_trait(
+        &self,
+        _name: &str,
+        _derive_trait: DeriveTrait,
+    ) -> Option<ImplementsTrait> {
+        None
+    }
+
+    /// Provide a list of custom derive attributes.
+    ///
+    /// If no additional attributes are wanted, this function should return an
+    /// empty `Vec`.
+    fn add_derives(&self, _info: &DeriveInfo<'_>) -> Vec<String> {
+        vec![]
+    }
+
+    /// Process a source code comment.
+    fn process_comment(&self, _comment: &str) -> Option<String> {
+        None
+    }
+
+    /// Potentially override the visibility of a composite type field.
+    ///
+    /// Caution: This allows overriding standard C++ visibility inferred by
+    /// `respect_cxx_access_specs`.
+    fn field_visibility(
+        &self,
+        _info: FieldInfo<'_>,
+    ) -> Option<crate::FieldVisibilityKind> {
+        None
+    }
+
+    /// Process a function name that as exactly one `va_list` argument
+    /// to be wrapped as a variadic function with the wrapped static function
+    /// feature.
+    ///
+    /// The returned string is new function name.
+    #[cfg(feature = "experimental")]
+    fn wrap_as_variadic_fn(&self, _name: &str) -> Option<String> {
+        None
+    }
+}
+
+/// Relevant information about a type to which new derive attributes will be added using
+/// [`ParseCallbacks::add_derives`].
+#[derive(Debug)]
+#[non_exhaustive]
+pub struct DeriveInfo<'a> {
+    /// The name of the type.
+    pub name: &'a str,
+    /// The kind of the type.
+    pub kind: TypeKind,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// The kind of the current type.
+pub enum TypeKind {
+    /// The type is a Rust `struct`.
+    Struct,
+    /// The type is a Rust `enum`.
+    Enum,
+    /// The type is a Rust `union`.
+    Union,
+}
+
+/// A struct providing information about the item being passed to [`ParseCallbacks::generated_name_override`].
+#[non_exhaustive]
+pub struct ItemInfo<'a> {
+    /// The name of the item
+    pub name: &'a str,
+    /// The kind of item
+    pub kind: ItemKind,
+}
+
+/// An enum indicating the kind of item for an ItemInfo.
+#[non_exhaustive]
+pub enum ItemKind {
+    /// A Function
+    Function,
+    /// A Variable
+    Var,
+}
+
+/// Relevant information about a field for which visibility can be determined using
+/// [`ParseCallbacks::field_visibility`].
+#[derive(Debug)]
+#[non_exhaustive]
+pub struct FieldInfo<'a> {
+    /// The name of the type.
+    pub type_name: &'a str,
+    /// The name of the field.
+    pub field_name: &'a str,
+}
diff --git a/third_party/rust/bindgen/clang.rs b/third_party/rust/bindgen/clang.rs
new file mode 100644
index 0000000000..4a4ed89d69
--- /dev/null
+++ b/third_party/rust/bindgen/clang.rs
@@ -0,0 +1,2347 @@
+//! A higher level Clang API built on top of the generated bindings in the
+//! `clang_sys` module.
+
+#![allow(non_upper_case_globals, dead_code)]
+#![deny(clippy::missing_docs_in_private_items)]
+
+use crate::ir::context::BindgenContext;
+use clang_sys::*;
+use std::cmp;
+
+use std::ffi::{CStr, CString};
+use std::fmt;
+use std::hash::Hash;
+use std::hash::Hasher;
+use std::os::raw::{c_char, c_int, c_longlong, c_uint, c_ulong, c_ulonglong};
+use std::{mem, ptr, slice};
+
+/// Type representing a clang attribute.
+///
+/// Values of this type can be used to check for different attributes using the `has_attrs`
+/// function.
+pub(crate) struct Attribute {
+    name: &'static [u8],
+    kind: Option<CXCursorKind>,
+    token_kind: CXTokenKind,
+}
+
+impl Attribute {
+    /// A `warn_unused_result` attribute.
+    pub(crate) const MUST_USE: Self = Self {
+        name: b"warn_unused_result",
+        // FIXME(emilio): clang-sys doesn't expose `CXCursor_WarnUnusedResultAttr` (from clang 9).
+        kind: Some(440),
+        token_kind: CXToken_Identifier,
+    };
+
+    /// A `_Noreturn` attribute.
+    pub(crate) const NO_RETURN: Self = Self {
+        name: b"_Noreturn",
+        kind: None,
+        token_kind: CXToken_Keyword,
+    };
+
+    /// A `[[noreturn]]` attribute.
+    pub(crate) const NO_RETURN_CPP: Self = Self {
+        name: b"noreturn",
+        kind: None,
+        token_kind: CXToken_Identifier,
+    };
+}
+
+/// A cursor into the Clang AST, pointing to an AST node.
+///
+/// We call the AST node pointed to by the cursor the cursor's "referent".
+#[derive(Copy, Clone)]
+pub(crate) struct Cursor {
+    x: CXCursor,
+}
+
+impl fmt::Debug for Cursor {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            fmt,
+            "Cursor({} kind: {}, loc: {}, usr: {:?})",
+            self.spelling(),
+            kind_to_str(self.kind()),
+            self.location(),
+            self.usr()
+        )
+    }
+}
+
+impl Cursor {
+    /// Get the Unified Symbol Resolution for this cursor's referent, if
+    /// available.
+    ///
+    /// The USR can be used to compare entities across translation units.
+    pub(crate) fn usr(&self) -> Option<String> {
+        let s = unsafe { cxstring_into_string(clang_getCursorUSR(self.x)) };
+        if s.is_empty() {
+            None
+        } else {
+            Some(s)
+        }
+    }
+
+    /// Is this cursor's referent a declaration?
+    pub(crate) fn is_declaration(&self) -> bool {
+        unsafe { clang_isDeclaration(self.kind()) != 0 }
+    }
+
+    /// Is this cursor's referent an anonymous record or so?
+    pub(crate) fn is_anonymous(&self) -> bool {
+        unsafe { clang_Cursor_isAnonymous(self.x) != 0 }
+    }
+
+    /// Get this cursor's referent's spelling.
+    pub(crate) fn spelling(&self) -> String {
+        unsafe { cxstring_into_string(clang_getCursorSpelling(self.x)) }
+    }
+
+    /// Get this cursor's referent's display name.
+    ///
+    /// This is not necessarily a valid identifier. It includes extra
+    /// information, such as parameters for a function, etc.
+    pub(crate) fn display_name(&self) -> String {
+        unsafe { cxstring_into_string(clang_getCursorDisplayName(self.x)) }
+    }
+
+    /// Get the mangled name of this cursor's referent.
+    pub(crate) fn mangling(&self) -> String {
+        unsafe { cxstring_into_string(clang_Cursor_getMangling(self.x)) }
+    }
+
+    /// Gets the C++ manglings for this cursor, or an error if the manglings
+    /// are not available.
+    pub(crate) fn cxx_manglings(&self) -> Result<Vec<String>, ()> {
+        use clang_sys::*;
+        unsafe {
+            let manglings = clang_Cursor_getCXXManglings(self.x);
+            if manglings.is_null() {
+                return Err(());
+            }
+            let count = (*manglings).Count as usize;
+
+            let mut result = Vec::with_capacity(count);
+            for i in 0..count {
+                let string_ptr = (*manglings).Strings.add(i);
+                result.push(cxstring_to_string_leaky(*string_ptr));
+            }
+            clang_disposeStringSet(manglings);
+            Ok(result)
+        }
+    }
+
+    /// Returns whether the cursor refers to a built-in definition.
+    pub(crate) fn is_builtin(&self) -> bool {
+        let (file, _, _, _) = self.location().location();
+        file.name().is_none()
+    }
+
+    /// Get the `Cursor` for this cursor's referent's lexical parent.
+    ///
+    /// The lexical parent is the parent of the definition. The semantic parent
+    /// is the parent of the declaration. Generally, the lexical parent doesn't
+    /// have any effect on semantics, while the semantic parent does.
+    ///
+    /// In the following snippet, the `Foo` class would be the semantic parent
+    /// of the out-of-line `method` definition, while the lexical parent is the
+    /// translation unit.
+    ///
+    /// ```c++
+    /// class Foo {
+    ///     void method();
+    /// };
+    ///
+    /// void Foo::method() { /* ... */ }
+    /// ```
+    pub(crate) fn lexical_parent(&self) -> Cursor {
+        unsafe {
+            Cursor {
+                x: clang_getCursorLexicalParent(self.x),
+            }
+        }
+    }
+
+    /// Get the referent's semantic parent, if one is available.
+    ///
+    /// See documentation for `lexical_parent` for details on semantic vs
+    /// lexical parents.
+    pub(crate) fn fallible_semantic_parent(&self) -> Option<Cursor> {
+        let sp = unsafe {
+            Cursor {
+                x: clang_getCursorSemanticParent(self.x),
+            }
+        };
+        if sp == *self || !sp.is_valid() {
+            return None;
+        }
+        Some(sp)
+    }
+
+    /// Get the referent's semantic parent.
+    ///
+    /// See documentation for `lexical_parent` for details on semantic vs
+    /// lexical parents.
+    pub(crate) fn semantic_parent(&self) -> Cursor {
+        self.fallible_semantic_parent().unwrap()
+    }
+
+    /// Return the number of template arguments used by this cursor's referent,
+    /// if the referent is either a template instantiation. Returns `None`
+    /// otherwise.
+    ///
+    /// NOTE: This may not return `Some` for partial template specializations,
+    /// see #193 and #194.
+    pub(crate) fn num_template_args(&self) -> Option<u32> {
+        // XXX: `clang_Type_getNumTemplateArguments` is sort of reliable, while
+        // `clang_Cursor_getNumTemplateArguments` is totally unreliable.
+        // Therefore, try former first, and only fallback to the latter if we
+        // have to.
+        self.cur_type()
+            .num_template_args()
+            .or_else(|| {
+                let n: c_int =
+                    unsafe { clang_Cursor_getNumTemplateArguments(self.x) };
+
+                if n >= 0 {
+                    Some(n as u32)
+                } else {
+                    debug_assert_eq!(n, -1);
+                    None
+                }
+            })
+            .or_else(|| {
+                let canonical = self.canonical();
+                if canonical != *self {
+                    canonical.num_template_args()
+                } else {
+                    None
+                }
+            })
+    }
+
+    /// Get a cursor pointing to this referent's containing translation unit.
+    ///
+    /// Note that we shouldn't create a `TranslationUnit` struct here, because
+    /// bindgen assumes there will only be one of them alive at a time, and
+    /// disposes it on drop. That can change if this would be required, but I
+    /// think we can survive fine without it.
+    pub(crate) fn translation_unit(&self) -> Cursor {
+        assert!(self.is_valid());
+        unsafe {
+            let tu = clang_Cursor_getTranslationUnit(self.x);
+            let cursor = Cursor {
+                x: clang_getTranslationUnitCursor(tu),
+            };
+            assert!(cursor.is_valid());
+            cursor
+        }
+    }
+
+    /// Is the referent a top level construct?
+    pub(crate) fn is_toplevel(&self) -> bool {
+        let mut semantic_parent = self.fallible_semantic_parent();
+
+        while semantic_parent.is_some() &&
+            (semantic_parent.unwrap().kind() == CXCursor_Namespace ||
+                semantic_parent.unwrap().kind() ==
+                    CXCursor_NamespaceAlias ||
+                semantic_parent.unwrap().kind() == CXCursor_NamespaceRef)
+        {
+            semantic_parent =
+                semantic_parent.unwrap().fallible_semantic_parent();
+        }
+
+        let tu = self.translation_unit();
+        // Yes, this can happen with, e.g., macro definitions.
+        semantic_parent == tu.fallible_semantic_parent()
+    }
+
+    /// There are a few kinds of types that we need to treat specially, mainly
+    /// not tracking the type declaration but the location of the cursor, given
+    /// clang doesn't expose a proper declaration for these types.
+    pub(crate) fn is_template_like(&self) -> bool {
+        matches!(
+            self.kind(),
+            CXCursor_ClassTemplate |
+                CXCursor_ClassTemplatePartialSpecialization |
+                CXCursor_TypeAliasTemplateDecl
+        )
+    }
+
+    /// Is this Cursor pointing to a function-like macro definition?
+    pub(crate) fn is_macro_function_like(&self) -> bool {
+        unsafe { clang_Cursor_isMacroFunctionLike(self.x) != 0 }
+    }
+
+    /// Get the kind of referent this cursor is pointing to.
+    pub(crate) fn kind(&self) -> CXCursorKind {
+        self.x.kind
+    }
+
+    /// Returns true if the cursor is a definition
+    pub(crate) fn is_definition(&self) -> bool {
+        unsafe { clang_isCursorDefinition(self.x) != 0 }
+    }
+
+    /// Is the referent a template specialization?
+    pub(crate) fn is_template_specialization(&self) -> bool {
+        self.specialized().is_some()
+    }
+
+    /// Is the referent a fully specialized template specialization without any
+    /// remaining free template arguments?
+    pub(crate) fn is_fully_specialized_template(&self) -> bool {
+        self.is_template_specialization() &&
+            self.kind() != CXCursor_ClassTemplatePartialSpecialization &&
+            self.num_template_args().unwrap_or(0) > 0
+    }
+
+    /// Is the referent a template specialization that still has remaining free
+    /// template arguments?
+    pub(crate) fn is_in_non_fully_specialized_template(&self) -> bool {
+        if self.is_toplevel() {
+            return false;
+        }
+
+        let parent = self.semantic_parent();
+        if parent.is_fully_specialized_template() {
+            return false;
+        }
+
+        if !parent.is_template_like() {
+            return parent.is_in_non_fully_specialized_template();
+        }
+
+        true
+    }
+
+    /// Is the referent any kind of template parameter?
+    pub(crate) fn is_template_parameter(&self) -> bool {
+        matches!(
+            self.kind(),
+            CXCursor_TemplateTemplateParameter |
+                CXCursor_TemplateTypeParameter |
+                CXCursor_NonTypeTemplateParameter
+        )
+    }
+
+    /// Does the referent's type or value depend on a template parameter?
+    pub(crate) fn is_dependent_on_template_parameter(&self) -> bool {
+        fn visitor(
+            found_template_parameter: &mut bool,
+            cur: Cursor,
+        ) -> CXChildVisitResult {
+            // If we found a template parameter, it is dependent.
+            if cur.is_template_parameter() {
+                *found_template_parameter = true;
+                return CXChildVisit_Break;
+            }
+
+            // Get the referent and traverse it as well.
+            if let Some(referenced) = cur.referenced() {
+                if referenced.is_template_parameter() {
+                    *found_template_parameter = true;
+                    return CXChildVisit_Break;
+                }
+
+                referenced
+                    .visit(|next| visitor(found_template_parameter, next));
+                if *found_template_parameter {
+                    return CXChildVisit_Break;
+                }
+            }
+
+            // Continue traversing the AST at the original cursor.
+            CXChildVisit_Recurse
+        }
+
+        if self.is_template_parameter() {
+            return true;
+        }
+
+        let mut found_template_parameter = false;
+        self.visit(|next| visitor(&mut found_template_parameter, next));
+
+        found_template_parameter
+    }
+
+    /// Is this cursor pointing a valid referent?
+    pub(crate) fn is_valid(&self) -> bool {
+        unsafe { clang_isInvalid(self.kind()) == 0 }
+    }
+
+    /// Get the source location for the referent.
+    pub(crate) fn location(&self) -> SourceLocation {
+        unsafe {
+            SourceLocation {
+                x: clang_getCursorLocation(self.x),
+            }
+        }
+    }
+
+    /// Get the source location range for the referent.
+    pub(crate) fn extent(&self) -> CXSourceRange {
+        unsafe { clang_getCursorExtent(self.x) }
+    }
+
+    /// Get the raw declaration comment for this referent, if one exists.
+    pub(crate) fn raw_comment(&self) -> Option<String> {
+        let s = unsafe {
+            cxstring_into_string(clang_Cursor_getRawCommentText(self.x))
+        };
+        if s.is_empty() {
+            None
+        } else {
+            Some(s)
+        }
+    }
+
+    /// Get the referent's parsed comment.
+    pub(crate) fn comment(&self) -> Comment {
+        unsafe {
+            Comment {
+                x: clang_Cursor_getParsedComment(self.x),
+            }
+        }
+    }
+
+    /// Get the referent's type.
+    pub(crate) fn cur_type(&self) -> Type {
+        unsafe {
+            Type {
+                x: clang_getCursorType(self.x),
+            }
+        }
+    }
+
+    /// Given that this cursor's referent is a reference to another type, or is
+    /// a declaration, get the cursor pointing to the referenced type or type of
+    /// the declared thing.
+    pub(crate) fn definition(&self) -> Option<Cursor> {
+        unsafe {
+            let ret = Cursor {
+                x: clang_getCursorDefinition(self.x),
+            };
+
+            if ret.is_valid() && ret.kind() != CXCursor_NoDeclFound {
+                Some(ret)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Given that this cursor's referent is reference type, get the cursor
+    /// pointing to the referenced type.
+    pub(crate) fn referenced(&self) -> Option<Cursor> {
+        unsafe {
+            let ret = Cursor {
+                x: clang_getCursorReferenced(self.x),
+            };
+
+            if ret.is_valid() {
+                Some(ret)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Get the canonical cursor for this referent.
+    ///
+    /// Many types can be declared multiple times before finally being properly
+    /// defined. This method allows us to get the canonical cursor for the
+    /// referent type.
+    pub(crate) fn canonical(&self) -> Cursor {
+        unsafe {
+            Cursor {
+                x: clang_getCanonicalCursor(self.x),
+            }
+        }
+    }
+
+    /// Given that this cursor points to either a template specialization or a
+    /// template instantiation, get a cursor pointing to the template definition
+    /// that is being specialized.
+    pub(crate) fn specialized(&self) -> Option<Cursor> {
+        unsafe {
+            let ret = Cursor {
+                x: clang_getSpecializedCursorTemplate(self.x),
+            };
+            if ret.is_valid() {
+                Some(ret)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Assuming that this cursor's referent is a template declaration, get the
+    /// kind of cursor that would be generated for its specializations.
+    pub(crate) fn template_kind(&self) -> CXCursorKind {
+        unsafe { clang_getTemplateCursorKind(self.x) }
+    }
+
+    /// Traverse this cursor's referent and its children.
+    ///
+    /// Call the given function on each AST node traversed.
+    pub(crate) fn visit<Visitor>(&self, mut visitor: Visitor)
+    where
+        Visitor: FnMut(Cursor) -> CXChildVisitResult,
+    {
+        let data = &mut visitor as *mut Visitor;
+        unsafe {
+            clang_visitChildren(self.x, visit_children::<Visitor>, data.cast());
+        }
+    }
+
+    /// Traverse all of this cursor's children, sorted by where they appear in source code.
+    ///
+    /// Call the given function on each AST node traversed.
+    pub(crate) fn visit_sorted<Visitor>(
+        &self,
+        ctx: &mut BindgenContext,
+        mut visitor: Visitor,
+    ) where
+        Visitor: FnMut(&mut BindgenContext, Cursor),
+    {
+        // FIXME(#2556): The current source order stuff doesn't account well for different levels
+        // of includes, or includes that show up at the same byte offset because they are passed in
+        // via CLI.
+        const SOURCE_ORDER_ENABLED: bool = false;
+        if !SOURCE_ORDER_ENABLED {
+            return self.visit(|c| {
+                visitor(ctx, c);
+                CXChildVisit_Continue
+            });
+        }
+
+        let mut children = self.collect_children();
+        for child in &children {
+            if child.kind() == CXCursor_InclusionDirective {
+                if let Some(included_file) = child.get_included_file_name() {
+                    let location = child.location();
+                    let (source_file, _, _, offset) = location.location();
+
+                    if let Some(source_file) = source_file.name() {
+                        ctx.add_include(source_file, included_file, offset);
+                    }
+                }
+            }
+        }
+        children
+            .sort_by(|child1, child2| child1.cmp_by_source_order(child2, ctx));
+        for child in children {
+            visitor(ctx, child);
+        }
+    }
+
+    /// Compare source order of two cursors, considering `#include` directives.
+    ///
+    /// Built-in items provided by the compiler (which don't have a source file),
+    /// are sorted first. Remaining files are sorted by their position in the source file.
+    /// If the items' source files differ, they are sorted by the position of the first
+    /// `#include` for their source file. If no source files are included, `None` is returned.
+    fn cmp_by_source_order(
+        &self,
+        other: &Self,
+        ctx: &BindgenContext,
+    ) -> cmp::Ordering {
+        let (file, _, _, offset) = self.location().location();
+        let (other_file, _, _, other_offset) = other.location().location();
+
+        let (file, other_file) = match (file.name(), other_file.name()) {
+            (Some(file), Some(other_file)) => (file, other_file),
+            // Built-in definitions should come first.
+            (Some(_), None) => return cmp::Ordering::Greater,
+            (None, Some(_)) => return cmp::Ordering::Less,
+            (None, None) => return cmp::Ordering::Equal,
+        };
+
+        if file == other_file {
+            // Both items are in the same source file, compare by byte offset.
+            return offset.cmp(&other_offset);
+        }
+
+        let include_location = ctx.included_file_location(&file);
+        let other_include_location = ctx.included_file_location(&other_file);
+        match (include_location, other_include_location) {
+            (Some((file2, offset2)), _) if file2 == other_file => {
+                offset2.cmp(&other_offset)
+            }
+            (Some(_), None) => cmp::Ordering::Greater,
+            (_, Some((other_file2, other_offset2))) if file == other_file2 => {
+                offset.cmp(&other_offset2)
+            }
+            (None, Some(_)) => cmp::Ordering::Less,
+            (Some((file2, offset2)), Some((other_file2, other_offset2))) => {
+                if file2 == other_file2 {
+                    offset2.cmp(&other_offset2)
+                } else {
+                    cmp::Ordering::Equal
+                }
+            }
+            (None, None) => cmp::Ordering::Equal,
+        }
+    }
+
+    /// Collect all of this cursor's children into a vec and return them.
+    pub(crate) fn collect_children(&self) -> Vec<Cursor> {
+        let mut children = vec![];
+        self.visit(|c| {
+            children.push(c);
+            CXChildVisit_Continue
+        });
+        children
+    }
+
+    /// Does this cursor have any children?
+    pub(crate) fn has_children(&self) -> bool {
+        let mut has_children = false;
+        self.visit(|_| {
+            has_children = true;
+            CXChildVisit_Break
+        });
+        has_children
+    }
+
+    /// Does this cursor have at least `n` children?
+    pub(crate) fn has_at_least_num_children(&self, n: usize) -> bool {
+        assert!(n > 0);
+        let mut num_left = n;
+        self.visit(|_| {
+            num_left -= 1;
+            if num_left == 0 {
+                CXChildVisit_Break
+            } else {
+                CXChildVisit_Continue
+            }
+        });
+        num_left == 0
+    }
+
+    /// Returns whether the given location contains a cursor with the given
+    /// kind in the first level of nesting underneath (doesn't look
+    /// recursively).
+    pub(crate) fn contains_cursor(&self, kind: CXCursorKind) -> bool {
+        let mut found = false;
+
+        self.visit(|c| {
+            if c.kind() == kind {
+                found = true;
+                CXChildVisit_Break
+            } else {
+                CXChildVisit_Continue
+            }
+        });
+
+        found
+    }
+
+    /// Is the referent an inlined function?
+    pub(crate) fn is_inlined_function(&self) -> bool {
+        unsafe { clang_Cursor_isFunctionInlined(self.x) != 0 }
+    }
+
+    /// Is the referent a defaulted function?
+    pub(crate) fn is_defaulted_function(&self) -> bool {
+        unsafe { clang_CXXMethod_isDefaulted(self.x) != 0 }
+    }
+
+    /// Is the referent a deleted function?
+    pub(crate) fn is_deleted_function(&self) -> bool {
+        // Unfortunately, libclang doesn't yet have an API for checking if a
+        // member function is deleted, but the following should be a good
+        // enough approximation.
+        // Deleted functions are implicitly inline according to paragraph 4 of
+        // [dcl.fct.def.delete] in the C++ standard. Normal inline functions
+        // have a definition in the same translation unit, so if this is an
+        // inline function without a definition, and it's not a defaulted
+        // function, we can reasonably safely conclude that it's a deleted
+        // function.
+        self.is_inlined_function() &&
+            self.definition().is_none() &&
+            !self.is_defaulted_function()
+    }
+
+    /// Is the referent a bit field declaration?
+    pub(crate) fn is_bit_field(&self) -> bool {
+        unsafe { clang_Cursor_isBitField(self.x) != 0 }
+    }
+
+    /// Get a cursor to the bit field's width expression, or `None` if it's not
+    /// a bit field.
+    pub(crate) fn bit_width_expr(&self) -> Option<Cursor> {
+        if !self.is_bit_field() {
+            return None;
+        }
+
+        let mut result = None;
+        self.visit(|cur| {
+            // The first child may or may not be a TypeRef, depending on whether
+            // the field's type is builtin. Skip it.
+            if cur.kind() == CXCursor_TypeRef {
+                return CXChildVisit_Continue;
+            }
+
+            // The next expression or literal is the bit width.
+            result = Some(cur);
+
+            CXChildVisit_Break
+        });
+
+        result
+    }
+
+    /// Get the width of this cursor's referent bit field, or `None` if the
+    /// referent is not a bit field or if the width could not be evaluated.
+    pub(crate) fn bit_width(&self) -> Option<u32> {
+        // It is not safe to check the bit width without ensuring it doesn't
+        // depend on a template parameter. See
+        // https://github.com/rust-lang/rust-bindgen/issues/2239
+        if self.bit_width_expr()?.is_dependent_on_template_parameter() {
+            return None;
+        }
+
+        unsafe {
+            let w = clang_getFieldDeclBitWidth(self.x);
+            if w == -1 {
+                None
+            } else {
+                Some(w as u32)
+            }
+        }
+    }
+
+    /// Get the integer representation type used to hold this cursor's referent
+    /// enum type.
+    pub(crate) fn enum_type(&self) -> Option<Type> {
+        unsafe {
+            let t = Type {
+                x: clang_getEnumDeclIntegerType(self.x),
+            };
+            if t.is_valid() {
+                Some(t)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Get the boolean constant value for this cursor's enum variant referent.
+    ///
+    /// Returns None if the cursor's referent is not an enum variant.
+    pub(crate) fn enum_val_boolean(&self) -> Option<bool> {
+        unsafe {
+            if self.kind() == CXCursor_EnumConstantDecl {
+                Some(clang_getEnumConstantDeclValue(self.x) != 0)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Get the signed constant value for this cursor's enum variant referent.
+    ///
+    /// Returns None if the cursor's referent is not an enum variant.
+    pub(crate) fn enum_val_signed(&self) -> Option<i64> {
+        unsafe {
+            if self.kind() == CXCursor_EnumConstantDecl {
+                #[allow(clippy::unnecessary_cast)]
+                Some(clang_getEnumConstantDeclValue(self.x) as i64)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Get the unsigned constant value for this cursor's enum variant referent.
+    ///
+    /// Returns None if the cursor's referent is not an enum variant.
+    pub(crate) fn enum_val_unsigned(&self) -> Option<u64> {
+        unsafe {
+            if self.kind() == CXCursor_EnumConstantDecl {
+                #[allow(clippy::unnecessary_cast)]
+                Some(clang_getEnumConstantDeclUnsignedValue(self.x) as u64)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Does this cursor have the given attributes?
+    pub(crate) fn has_attrs<const N: usize>(
+        &self,
+        attrs: &[Attribute; N],
+    ) -> [bool; N] {
+        let mut found_attrs = [false; N];
+        let mut found_count = 0;
+
+        self.visit(|cur| {
+            let kind = cur.kind();
+            for (idx, attr) in attrs.iter().enumerate() {
+                let found_attr = &mut found_attrs[idx];
+                if !*found_attr {
+                    // `attr.name` and` attr.token_kind` are checked against unexposed attributes only.
+                    if attr.kind.map_or(false, |k| k == kind) ||
+                        (kind == CXCursor_UnexposedAttr &&
+                            cur.tokens().iter().any(|t| {
+                                t.kind == attr.token_kind &&
+                                    t.spelling() == attr.name
+                            }))
+                    {
+                        *found_attr = true;
+                        found_count += 1;
+
+                        if found_count == N {
+                            return CXChildVisit_Break;
+                        }
+                    }
+                }
+            }
+
+            CXChildVisit_Continue
+        });
+
+        found_attrs
+    }
+
+    /// Given that this cursor's referent is a `typedef`, get the `Type` that is
+    /// being aliased.
+    pub(crate) fn typedef_type(&self) -> Option<Type> {
+        let inner = Type {
+            x: unsafe { clang_getTypedefDeclUnderlyingType(self.x) },
+        };
+
+        if inner.is_valid() {
+            Some(inner)
+        } else {
+            None
+        }
+    }
+
+    /// Get the linkage kind for this cursor's referent.
+    ///
+    /// This only applies to functions and variables.
+    pub(crate) fn linkage(&self) -> CXLinkageKind {
+        unsafe { clang_getCursorLinkage(self.x) }
+    }
+
+    /// Get the visibility of this cursor's referent.
+    pub(crate) fn visibility(&self) -> CXVisibilityKind {
+        unsafe { clang_getCursorVisibility(self.x) }
+    }
+
+    /// Given that this cursor's referent is a function, return cursors to its
+    /// parameters.
+    ///
+    /// Returns None if the cursor's referent is not a function/method call or
+    /// declaration.
+    pub(crate) fn args(&self) -> Option<Vec<Cursor>> {
+        // match self.kind() {
+        // CXCursor_FunctionDecl |
+        // CXCursor_CXXMethod => {
+        self.num_args().ok().map(|num| {
+            (0..num)
+                .map(|i| Cursor {
+                    x: unsafe { clang_Cursor_getArgument(self.x, i as c_uint) },
+                })
+                .collect()
+        })
+    }
+
+    /// Given that this cursor's referent is a function/method call or
+    /// declaration, return the number of arguments it takes.
+    ///
+    /// Returns Err if the cursor's referent is not a function/method call or
+    /// declaration.
+    pub(crate) fn num_args(&self) -> Result<u32, ()> {
+        unsafe {
+            let w = clang_Cursor_getNumArguments(self.x);
+            if w == -1 {
+                Err(())
+            } else {
+                Ok(w as u32)
+            }
+        }
+    }
+
+    /// Get the access specifier for this cursor's referent.
+    pub(crate) fn access_specifier(&self) -> CX_CXXAccessSpecifier {
+        unsafe { clang_getCXXAccessSpecifier(self.x) }
+    }
+
+    /// Is the cursor's referrent publically accessible in C++?
+    ///
+    /// Returns true if self.access_specifier() is `CX_CXXPublic` or
+    /// `CX_CXXInvalidAccessSpecifier`.
+    pub(crate) fn public_accessible(&self) -> bool {
+        let access = self.access_specifier();
+        access == CX_CXXPublic || access == CX_CXXInvalidAccessSpecifier
+    }
+
+    /// Is this cursor's referent a field declaration that is marked as
+    /// `mutable`?
+    pub(crate) fn is_mutable_field(&self) -> bool {
+        unsafe { clang_CXXField_isMutable(self.x) != 0 }
+    }
+
+    /// Get the offset of the field represented by the Cursor.
+    pub(crate) fn offset_of_field(&self) -> Result<usize, LayoutError> {
+        let offset = unsafe { clang_Cursor_getOffsetOfField(self.x) };
+
+        if offset < 0 {
+            Err(LayoutError::from(offset as i32))
+        } else {
+            Ok(offset as usize)
+        }
+    }
+
+    /// Is this cursor's referent a member function that is declared `static`?
+    pub(crate) fn method_is_static(&self) -> bool {
+        unsafe { clang_CXXMethod_isStatic(self.x) != 0 }
+    }
+
+    /// Is this cursor's referent a member function that is declared `const`?
+    pub(crate) fn method_is_const(&self) -> bool {
+        unsafe { clang_CXXMethod_isConst(self.x) != 0 }
+    }
+
+    /// Is this cursor's referent a member function that is virtual?
+    pub(crate) fn method_is_virtual(&self) -> bool {
+        unsafe { clang_CXXMethod_isVirtual(self.x) != 0 }
+    }
+
+    /// Is this cursor's referent a member function that is pure virtual?
+    pub(crate) fn method_is_pure_virtual(&self) -> bool {
+        unsafe { clang_CXXMethod_isPureVirtual(self.x) != 0 }
+    }
+
+    /// Is this cursor's referent a struct or class with virtual members?
+    pub(crate) fn is_virtual_base(&self) -> bool {
+        unsafe { clang_isVirtualBase(self.x) != 0 }
+    }
+
+    /// Try to evaluate this cursor.
+    pub(crate) fn evaluate(&self) -> Option<EvalResult> {
+        EvalResult::new(*self)
+    }
+
+    /// Return the result type for this cursor
+    pub(crate) fn ret_type(&self) -> Option<Type> {
+        let rt = Type {
+            x: unsafe { clang_getCursorResultType(self.x) },
+        };
+        if rt.is_valid() {
+            Some(rt)
+        } else {
+            None
+        }
+    }
+
+    /// Gets the tokens that correspond to that cursor.
+    pub(crate) fn tokens(&self) -> RawTokens {
+        RawTokens::new(self)
+    }
+
+    /// Gets the tokens that correspond to that cursor as  `cexpr` tokens.
+    pub(crate) fn cexpr_tokens(self) -> Vec<cexpr::token::Token> {
+        self.tokens()
+            .iter()
+            .filter_map(|token| token.as_cexpr_token())
+            .collect()
+    }
+
+    /// Obtain the real path name of a cursor of InclusionDirective kind.
+    ///
+    /// Returns None if the cursor does not include a file, otherwise the file's full name
+    pub(crate) fn get_included_file_name(&self) -> Option<String> {
+        let file = unsafe { clang_sys::clang_getIncludedFile(self.x) };
+        if file.is_null() {
+            None
+        } else {
+            Some(unsafe {
+                cxstring_into_string(clang_sys::clang_getFileName(file))
+            })
+        }
+    }
+}
+
+/// A struct that owns the tokenizer result from a given cursor.
+pub(crate) struct RawTokens<'a> {
+    cursor: &'a Cursor,
+    tu: CXTranslationUnit,
+    tokens: *mut CXToken,
+    token_count: c_uint,
+}
+
+impl<'a> RawTokens<'a> {
+    fn new(cursor: &'a Cursor) -> Self {
+        let mut tokens = ptr::null_mut();
+        let mut token_count = 0;
+        let range = cursor.extent();
+        let tu = unsafe { clang_Cursor_getTranslationUnit(cursor.x) };
+        unsafe { clang_tokenize(tu, range, &mut tokens, &mut token_count) };
+        Self {
+            cursor,
+            tu,
+            tokens,
+            token_count,
+        }
+    }
+
+    fn as_slice(&self) -> &[CXToken] {
+        if self.tokens.is_null() {
+            return &[];
+        }
+        unsafe { slice::from_raw_parts(self.tokens, self.token_count as usize) }
+    }
+
+    /// Get an iterator over these tokens.
+    pub(crate) fn iter(&self) -> ClangTokenIterator {
+        ClangTokenIterator {
+            tu: self.tu,
+            raw: self.as_slice().iter(),
+        }
+    }
+}
+
+impl<'a> Drop for RawTokens<'a> {
+    fn drop(&mut self) {
+        if !self.tokens.is_null() {
+            unsafe {
+                clang_disposeTokens(
+                    self.tu,
+                    self.tokens,
+                    self.token_count as c_uint,
+                );
+            }
+        }
+    }
+}
+
+/// A raw clang token, that exposes only kind, spelling, and extent. This is a
+/// slightly more convenient version of `CXToken` which owns the spelling
+/// string and extent.
+#[derive(Debug)]
+pub(crate) struct ClangToken {
+    spelling: CXString,
+    /// The extent of the token. This is the same as the relevant member from
+    /// `CXToken`.
+    pub(crate) extent: CXSourceRange,
+    /// The kind of the token. This is the same as the relevant member from
+    /// `CXToken`.
+    pub(crate) kind: CXTokenKind,
+}
+
+impl ClangToken {
+    /// Get the token spelling, without being converted to utf-8.
+    pub(crate) fn spelling(&self) -> &[u8] {
+        let c_str = unsafe {
+            CStr::from_ptr(clang_getCString(self.spelling) as *const _)
+        };
+        c_str.to_bytes()
+    }
+
+    /// Converts a ClangToken to a `cexpr` token if possible.
+    pub(crate) fn as_cexpr_token(&self) -> Option<cexpr::token::Token> {
+        use cexpr::token;
+
+        let kind = match self.kind {
+            CXToken_Punctuation => token::Kind::Punctuation,
+            CXToken_Literal => token::Kind::Literal,
+            CXToken_Identifier => token::Kind::Identifier,
+            CXToken_Keyword => token::Kind::Keyword,
+            // NB: cexpr is not too happy about comments inside
+            // expressions, so we strip them down here.
+            CXToken_Comment => return None,
+            _ => {
+                warn!("Found unexpected token kind: {:?}", self);
+                return None;
+            }
+        };
+
+        Some(token::Token {
+            kind,
+            raw: self.spelling().to_vec().into_boxed_slice(),
+        })
+    }
+}
+
+impl Drop for ClangToken {
+    fn drop(&mut self) {
+        unsafe { clang_disposeString(self.spelling) }
+    }
+}
+
+/// An iterator over a set of Tokens.
+pub(crate) struct ClangTokenIterator<'a> {
+    tu: CXTranslationUnit,
+    raw: slice::Iter<'a, CXToken>,
+}
+
+impl<'a> Iterator for ClangTokenIterator<'a> {
+    type Item = ClangToken;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let raw = self.raw.next()?;
+        unsafe {
+            let kind = clang_getTokenKind(*raw);
+            let spelling = clang_getTokenSpelling(self.tu, *raw);
+            let extent = clang_getTokenExtent(self.tu, *raw);
+            Some(ClangToken {
+                kind,
+                extent,
+                spelling,
+            })
+        }
+    }
+}
+
+/// Checks whether the name looks like an identifier, i.e. is alphanumeric
+/// (including '_') and does not start with a digit.
+pub(crate) fn is_valid_identifier(name: &str) -> bool {
+    let mut chars = name.chars();
+    let first_valid = chars
+        .next()
+        .map(|c| c.is_alphabetic() || c == '_')
+        .unwrap_or(false);
+
+    first_valid && chars.all(|c| c.is_alphanumeric() || c == '_')
+}
+
+extern "C" fn visit_children<Visitor>(
+    cur: CXCursor,
+    _parent: CXCursor,
+    data: CXClientData,
+) -> CXChildVisitResult
+where
+    Visitor: FnMut(Cursor) -> CXChildVisitResult,
+{
+    let func: &mut Visitor = unsafe { &mut *(data as *mut Visitor) };
+    let child = Cursor { x: cur };
+
+    (*func)(child)
+}
+
+impl PartialEq for Cursor {
+    fn eq(&self, other: &Cursor) -> bool {
+        unsafe { clang_equalCursors(self.x, other.x) == 1 }
+    }
+}
+
+impl Eq for Cursor {}
+
+impl Hash for Cursor {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        unsafe { clang_hashCursor(self.x) }.hash(state)
+    }
+}
+
+/// The type of a node in clang's AST.
+#[derive(Clone, Copy)]
+pub(crate) struct Type {
+    x: CXType,
+}
+
+impl PartialEq for Type {
+    fn eq(&self, other: &Self) -> bool {
+        unsafe { clang_equalTypes(self.x, other.x) != 0 }
+    }
+}
+
+impl Eq for Type {}
+
+impl fmt::Debug for Type {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            fmt,
+            "Type({}, kind: {}, cconv: {}, decl: {:?}, canon: {:?})",
+            self.spelling(),
+            type_to_str(self.kind()),
+            self.call_conv(),
+            self.declaration(),
+            self.declaration().canonical()
+        )
+    }
+}
+
+/// An error about the layout of a struct, class, or type.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub(crate) enum LayoutError {
+    /// Asked for the layout of an invalid type.
+    Invalid,
+    /// Asked for the layout of an incomplete type.
+    Incomplete,
+    /// Asked for the layout of a dependent type.
+    Dependent,
+    /// Asked for the layout of a type that does not have constant size.
+    NotConstantSize,
+    /// Asked for the layout of a field in a type that does not have such a
+    /// field.
+    InvalidFieldName,
+    /// An unknown layout error.
+    Unknown,
+}
+
+impl ::std::convert::From<i32> for LayoutError {
+    fn from(val: i32) -> Self {
+        use self::LayoutError::*;
+
+        match val {
+            CXTypeLayoutError_Invalid => Invalid,
+            CXTypeLayoutError_Incomplete => Incomplete,
+            CXTypeLayoutError_Dependent => Dependent,
+            CXTypeLayoutError_NotConstantSize => NotConstantSize,
+            CXTypeLayoutError_InvalidFieldName => InvalidFieldName,
+            _ => Unknown,
+        }
+    }
+}
+
+impl Type {
+    /// Get this type's kind.
+    pub(crate) fn kind(&self) -> CXTypeKind {
+        self.x.kind
+    }
+
+    /// Get a cursor pointing to this type's declaration.
+    pub(crate) fn declaration(&self) -> Cursor {
+        unsafe {
+            Cursor {
+                x: clang_getTypeDeclaration(self.x),
+            }
+        }
+    }
+
+    /// Get the canonical declaration of this type, if it is available.
+    pub(crate) fn canonical_declaration(
+        &self,
+        location: Option<&Cursor>,
+    ) -> Option<CanonicalTypeDeclaration> {
+        let mut declaration = self.declaration();
+        if !declaration.is_valid() {
+            if let Some(location) = location {
+                let mut location = *location;
+                if let Some(referenced) = location.referenced() {
+                    location = referenced;
+                }
+                if location.is_template_like() {
+                    declaration = location;
+                }
+            }
+        }
+
+        let canonical = declaration.canonical();
+        if canonical.is_valid() && canonical.kind() != CXCursor_NoDeclFound {
+            Some(CanonicalTypeDeclaration(*self, canonical))
+        } else {
+            None
+        }
+    }
+
+    /// Get a raw display name for this type.
+    pub(crate) fn spelling(&self) -> String {
+        let s = unsafe { cxstring_into_string(clang_getTypeSpelling(self.x)) };
+        // Clang 5.0 introduced changes in the spelling API so it returned the
+        // full qualified name. Let's undo that here.
+        if s.split("::").all(is_valid_identifier) {
+            if let Some(s) = s.split("::").last() {
+                return s.to_owned();
+            }
+        }
+
+        s
+    }
+
+    /// Is this type const qualified?
+    pub(crate) fn is_const(&self) -> bool {
+        unsafe { clang_isConstQualifiedType(self.x) != 0 }
+    }
+
+    #[inline]
+    fn is_non_deductible_auto_type(&self) -> bool {
+        debug_assert_eq!(self.kind(), CXType_Auto);
+        self.canonical_type() == *self
+    }
+
+    #[inline]
+    fn clang_size_of(&self, ctx: &BindgenContext) -> c_longlong {
+        match self.kind() {
+            // Work-around https://bugs.llvm.org/show_bug.cgi?id=40975
+            CXType_RValueReference | CXType_LValueReference => {
+                ctx.target_pointer_size() as c_longlong
+            }
+            // Work-around https://bugs.llvm.org/show_bug.cgi?id=40813
+            CXType_Auto if self.is_non_deductible_auto_type() => -6,
+            _ => unsafe { clang_Type_getSizeOf(self.x) },
+        }
+    }
+
+    #[inline]
+    fn clang_align_of(&self, ctx: &BindgenContext) -> c_longlong {
+        match self.kind() {
+            // Work-around https://bugs.llvm.org/show_bug.cgi?id=40975
+            CXType_RValueReference | CXType_LValueReference => {
+                ctx.target_pointer_size() as c_longlong
+            }
+            // Work-around https://bugs.llvm.org/show_bug.cgi?id=40813
+            CXType_Auto if self.is_non_deductible_auto_type() => -6,
+            _ => unsafe { clang_Type_getAlignOf(self.x) },
+        }
+    }
+
+    /// What is the size of this type? Paper over invalid types by returning `0`
+    /// for them.
+    pub(crate) fn size(&self, ctx: &BindgenContext) -> usize {
+        let val = self.clang_size_of(ctx);
+        if val < 0 {
+            0
+        } else {
+            val as usize
+        }
+    }
+
+    /// What is the size of this type?
+    pub(crate) fn fallible_size(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Result<usize, LayoutError> {
+        let val = self.clang_size_of(ctx);
+        if val < 0 {
+            Err(LayoutError::from(val as i32))
+        } else {
+            Ok(val as usize)
+        }
+    }
+
+    /// What is the alignment of this type? Paper over invalid types by
+    /// returning `0`.
+    pub(crate) fn align(&self, ctx: &BindgenContext) -> usize {
+        let val = self.clang_align_of(ctx);
+        if val < 0 {
+            0
+        } else {
+            val as usize
+        }
+    }
+
+    /// What is the alignment of this type?
+    pub(crate) fn fallible_align(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Result<usize, LayoutError> {
+        let val = self.clang_align_of(ctx);
+        if val < 0 {
+            Err(LayoutError::from(val as i32))
+        } else {
+            Ok(val as usize)
+        }
+    }
+
+    /// Get the layout for this type, or an error describing why it does not
+    /// have a valid layout.
+    pub(crate) fn fallible_layout(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Result<crate::ir::layout::Layout, LayoutError> {
+        use crate::ir::layout::Layout;
+        let size = self.fallible_size(ctx)?;
+        let align = self.fallible_align(ctx)?;
+        Ok(Layout::new(size, align))
+    }
+
+    /// Get the number of template arguments this type has, or `None` if it is
+    /// not some kind of template.
+    pub(crate) fn num_template_args(&self) -> Option<u32> {
+        let n = unsafe { clang_Type_getNumTemplateArguments(self.x) };
+        if n >= 0 {
+            Some(n as u32)
+        } else {
+            debug_assert_eq!(n, -1);
+            None
+        }
+    }
+
+    /// If this type is a class template specialization, return its
+    /// template arguments. Otherwise, return None.
+    pub(crate) fn template_args(&self) -> Option<TypeTemplateArgIterator> {
+        self.num_template_args().map(|n| TypeTemplateArgIterator {
+            x: self.x,
+            length: n,
+            index: 0,
+        })
+    }
+
+    /// Given that this type is a function prototype, return the types of its parameters.
+    ///
+    /// Returns None if the type is not a function prototype.
+    pub(crate) fn args(&self) -> Option<Vec<Type>> {
+        self.num_args().ok().map(|num| {
+            (0..num)
+                .map(|i| Type {
+                    x: unsafe { clang_getArgType(self.x, i as c_uint) },
+                })
+                .collect()
+        })
+    }
+
+    /// Given that this type is a function prototype, return the number of arguments it takes.
+    ///
+    /// Returns Err if the type is not a function prototype.
+    pub(crate) fn num_args(&self) -> Result<u32, ()> {
+        unsafe {
+            let w = clang_getNumArgTypes(self.x);
+            if w == -1 {
+                Err(())
+            } else {
+                Ok(w as u32)
+            }
+        }
+    }
+
+    /// Given that this type is a pointer type, return the type that it points
+    /// to.
+    pub(crate) fn pointee_type(&self) -> Option<Type> {
+        match self.kind() {
+            CXType_Pointer |
+            CXType_RValueReference |
+            CXType_LValueReference |
+            CXType_MemberPointer |
+            CXType_BlockPointer |
+            CXType_ObjCObjectPointer => {
+                let ret = Type {
+                    x: unsafe { clang_getPointeeType(self.x) },
+                };
+                debug_assert!(ret.is_valid());
+                Some(ret)
+            }
+            _ => None,
+        }
+    }
+
+    /// Given that this type is an array, vector, or complex type, return the
+    /// type of its elements.
+    pub(crate) fn elem_type(&self) -> Option<Type> {
+        let current_type = Type {
+            x: unsafe { clang_getElementType(self.x) },
+        };
+        if current_type.is_valid() {
+            Some(current_type)
+        } else {
+            None
+        }
+    }
+
+    /// Given that this type is an array or vector type, return its number of
+    /// elements.
+    pub(crate) fn num_elements(&self) -> Option<usize> {
+        let num_elements_returned = unsafe { clang_getNumElements(self.x) };
+        if num_elements_returned != -1 {
+            Some(num_elements_returned as usize)
+        } else {
+            None
+        }
+    }
+
+    /// Get the canonical version of this type. This sees through `typedef`s and
+    /// aliases to get the underlying, canonical type.
+    pub(crate) fn canonical_type(&self) -> Type {
+        unsafe {
+            Type {
+                x: clang_getCanonicalType(self.x),
+            }
+        }
+    }
+
+    /// Is this type a variadic function type?
+    pub(crate) fn is_variadic(&self) -> bool {
+        unsafe { clang_isFunctionTypeVariadic(self.x) != 0 }
+    }
+
+    /// Given that this type is a function type, get the type of its return
+    /// value.
+    pub(crate) fn ret_type(&self) -> Option<Type> {
+        let rt = Type {
+            x: unsafe { clang_getResultType(self.x) },
+        };
+        if rt.is_valid() {
+            Some(rt)
+        } else {
+            None
+        }
+    }
+
+    /// Given that this type is a function type, get its calling convention. If
+    /// this is not a function type, `CXCallingConv_Invalid` is returned.
+    pub(crate) fn call_conv(&self) -> CXCallingConv {
+        unsafe { clang_getFunctionTypeCallingConv(self.x) }
+    }
+
+    /// For elaborated types (types which use `class`, `struct`, or `union` to
+    /// disambiguate types from local bindings), get the underlying type.
+    pub(crate) fn named(&self) -> Type {
+        unsafe {
+            Type {
+                x: clang_Type_getNamedType(self.x),
+            }
+        }
+    }
+
+    /// Is this a valid type?
+    pub(crate) fn is_valid(&self) -> bool {
+        self.kind() != CXType_Invalid
+    }
+
+    /// Is this a valid and exposed type?
+    pub(crate) fn is_valid_and_exposed(&self) -> bool {
+        self.is_valid() && self.kind() != CXType_Unexposed
+    }
+
+    /// Is this type a fully instantiated template?
+    pub(crate) fn is_fully_instantiated_template(&self) -> bool {
+        // Yep, the spelling of this containing type-parameter is extremely
+        // nasty... But can happen in <type_traits>. Unfortunately I couldn't
+        // reduce it enough :(
+        self.template_args().map_or(false, |args| args.len() > 0) &&
+            !matches!(
+                self.declaration().kind(),
+                CXCursor_ClassTemplatePartialSpecialization |
+                    CXCursor_TypeAliasTemplateDecl |
+                    CXCursor_TemplateTemplateParameter
+            )
+    }
+
+    /// Is this type an associated template type? Eg `T::Associated` in
+    /// this example:
+    ///
+    /// ```c++
+    /// template <typename T>
+    /// class Foo {
+    ///     typename T::Associated member;
+    /// };
+    /// ```
+    pub(crate) fn is_associated_type(&self) -> bool {
+        // This is terrible :(
+        fn hacky_parse_associated_type<S: AsRef<str>>(spelling: S) -> bool {
+            lazy_static! {
+                static ref ASSOC_TYPE_RE: regex::Regex = regex::Regex::new(
+                    r"typename type\-parameter\-\d+\-\d+::.+"
+                )
+                .unwrap();
+            }
+            ASSOC_TYPE_RE.is_match(spelling.as_ref())
+        }
+
+        self.kind() == CXType_Unexposed &&
+            (hacky_parse_associated_type(self.spelling()) ||
+                hacky_parse_associated_type(
+                    self.canonical_type().spelling(),
+                ))
+    }
+}
+
+/// The `CanonicalTypeDeclaration` type exists as proof-by-construction that its
+/// cursor is the canonical declaration for its type. If you have a
+/// `CanonicalTypeDeclaration` instance, you know for sure that the type and
+/// cursor match up in a canonical declaration relationship, and it simply
+/// cannot be otherwise.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) struct CanonicalTypeDeclaration(Type, Cursor);
+
+impl CanonicalTypeDeclaration {
+    /// Get the type.
+    pub(crate) fn ty(&self) -> &Type {
+        &self.0
+    }
+
+    /// Get the type's canonical declaration cursor.
+    pub(crate) fn cursor(&self) -> &Cursor {
+        &self.1
+    }
+}
+
+/// An iterator for a type's template arguments.
+pub(crate) struct TypeTemplateArgIterator {
+    x: CXType,
+    length: u32,
+    index: u32,
+}
+
+impl Iterator for TypeTemplateArgIterator {
+    type Item = Type;
+    fn next(&mut self) -> Option<Type> {
+        if self.index < self.length {
+            let idx = self.index as c_uint;
+            self.index += 1;
+            Some(Type {
+                x: unsafe { clang_Type_getTemplateArgumentAsType(self.x, idx) },
+            })
+        } else {
+            None
+        }
+    }
+}
+
+impl ExactSizeIterator for TypeTemplateArgIterator {
+    fn len(&self) -> usize {
+        assert!(self.index <= self.length);
+        (self.length - self.index) as usize
+    }
+}
+
+/// A `SourceLocation` is a file, line, column, and byte offset location for
+/// some source text.
+pub(crate) struct SourceLocation {
+    x: CXSourceLocation,
+}
+
+impl SourceLocation {
+    /// Get the (file, line, column, byte offset) tuple for this source
+    /// location.
+    pub(crate) fn location(&self) -> (File, usize, usize, usize) {
+        unsafe {
+            let mut file = mem::zeroed();
+            let mut line = 0;
+            let mut col = 0;
+            let mut off = 0;
+            clang_getSpellingLocation(
+                self.x, &mut file, &mut line, &mut col, &mut off,
+            );
+            (File { x: file }, line as usize, col as usize, off as usize)
+        }
+    }
+}
+
+impl fmt::Display for SourceLocation {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let (file, line, col, _) = self.location();
+        if let Some(name) = file.name() {
+            write!(f, "{}:{}:{}", name, line, col)
+        } else {
+            "builtin definitions".fmt(f)
+        }
+    }
+}
+
+impl fmt::Debug for SourceLocation {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self)
+    }
+}
+
+/// A comment in the source text.
+///
+/// Comments are sort of parsed by Clang, and have a tree structure.
+pub(crate) struct Comment {
+    x: CXComment,
+}
+
+impl Comment {
+    /// What kind of comment is this?
+    pub(crate) fn kind(&self) -> CXCommentKind {
+        unsafe { clang_Comment_getKind(self.x) }
+    }
+
+    /// Get this comment's children comment
+    pub(crate) fn get_children(&self) -> CommentChildrenIterator {
+        CommentChildrenIterator {
+            parent: self.x,
+            length: unsafe { clang_Comment_getNumChildren(self.x) },
+            index: 0,
+        }
+    }
+
+    /// Given that this comment is the start or end of an HTML tag, get its tag
+    /// name.
+    pub(crate) fn get_tag_name(&self) -> String {
+        unsafe { cxstring_into_string(clang_HTMLTagComment_getTagName(self.x)) }
+    }
+
+    /// Given that this comment is an HTML start tag, get its attributes.
+    pub(crate) fn get_tag_attrs(&self) -> CommentAttributesIterator {
+        CommentAttributesIterator {
+            x: self.x,
+            length: unsafe { clang_HTMLStartTag_getNumAttrs(self.x) },
+            index: 0,
+        }
+    }
+}
+
+/// An iterator for a comment's children
+pub(crate) struct CommentChildrenIterator {
+    parent: CXComment,
+    length: c_uint,
+    index: c_uint,
+}
+
+impl Iterator for CommentChildrenIterator {
+    type Item = Comment;
+    fn next(&mut self) -> Option<Comment> {
+        if self.index < self.length {
+            let idx = self.index;
+            self.index += 1;
+            Some(Comment {
+                x: unsafe { clang_Comment_getChild(self.parent, idx) },
+            })
+        } else {
+            None
+        }
+    }
+}
+
+/// An HTML start tag comment attribute
+pub(crate) struct CommentAttribute {
+    /// HTML start tag attribute name
+    pub(crate) name: String,
+    /// HTML start tag attribute value
+    pub(crate) value: String,
+}
+
+/// An iterator for a comment's attributes
+pub(crate) struct CommentAttributesIterator {
+    x: CXComment,
+    length: c_uint,
+    index: c_uint,
+}
+
+impl Iterator for CommentAttributesIterator {
+    type Item = CommentAttribute;
+    fn next(&mut self) -> Option<CommentAttribute> {
+        if self.index < self.length {
+            let idx = self.index;
+            self.index += 1;
+            Some(CommentAttribute {
+                name: unsafe {
+                    cxstring_into_string(clang_HTMLStartTag_getAttrName(
+                        self.x, idx,
+                    ))
+                },
+                value: unsafe {
+                    cxstring_into_string(clang_HTMLStartTag_getAttrValue(
+                        self.x, idx,
+                    ))
+                },
+            })
+        } else {
+            None
+        }
+    }
+}
+
+/// A source file.
+pub(crate) struct File {
+    x: CXFile,
+}
+
+impl File {
+    /// Get the name of this source file.
+    pub(crate) fn name(&self) -> Option<String> {
+        if self.x.is_null() {
+            return None;
+        }
+        Some(unsafe { cxstring_into_string(clang_getFileName(self.x)) })
+    }
+}
+
+fn cxstring_to_string_leaky(s: CXString) -> String {
+    if s.data.is_null() {
+        return "".to_owned();
+    }
+    let c_str = unsafe { CStr::from_ptr(clang_getCString(s) as *const _) };
+    c_str.to_string_lossy().into_owned()
+}
+
+fn cxstring_into_string(s: CXString) -> String {
+    let ret = cxstring_to_string_leaky(s);
+    unsafe { clang_disposeString(s) };
+    ret
+}
+
+/// An `Index` is an environment for a set of translation units that will
+/// typically end up linked together in one final binary.
+pub(crate) struct Index {
+    x: CXIndex,
+}
+
+impl Index {
+    /// Construct a new `Index`.
+    ///
+    /// The `pch` parameter controls whether declarations in pre-compiled
+    /// headers are included when enumerating a translation unit's "locals".
+    ///
+    /// The `diag` parameter controls whether debugging diagnostics are enabled.
+    pub(crate) fn new(pch: bool, diag: bool) -> Index {
+        unsafe {
+            Index {
+                x: clang_createIndex(pch as c_int, diag as c_int),
+            }
+        }
+    }
+}
+
+impl fmt::Debug for Index {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "Index {{ }}")
+    }
+}
+
+impl Drop for Index {
+    fn drop(&mut self) {
+        unsafe {
+            clang_disposeIndex(self.x);
+        }
+    }
+}
+
+/// A translation unit (or "compilation unit").
+pub(crate) struct TranslationUnit {
+    x: CXTranslationUnit,
+}
+
+impl fmt::Debug for TranslationUnit {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "TranslationUnit {{ }}")
+    }
+}
+
+impl TranslationUnit {
+    /// Parse a source file into a translation unit.
+    pub(crate) fn parse(
+        ix: &Index,
+        file: &str,
+        cmd_args: &[Box<str>],
+        unsaved: &[UnsavedFile],
+        opts: CXTranslationUnit_Flags,
+    ) -> Option<TranslationUnit> {
+        let fname = CString::new(file).unwrap();
+        let _c_args: Vec<CString> = cmd_args
+            .iter()
+            .map(|s| CString::new(s.as_bytes()).unwrap())
+            .collect();
+        let c_args: Vec<*const c_char> =
+            _c_args.iter().map(|s| s.as_ptr()).collect();
+        let mut c_unsaved: Vec<CXUnsavedFile> =
+            unsaved.iter().map(|f| f.x).collect();
+        let tu = unsafe {
+            clang_parseTranslationUnit(
+                ix.x,
+                fname.as_ptr(),
+                c_args.as_ptr(),
+                c_args.len() as c_int,
+                c_unsaved.as_mut_ptr(),
+                c_unsaved.len() as c_uint,
+                opts,
+            )
+        };
+        if tu.is_null() {
+            None
+        } else {
+            Some(TranslationUnit { x: tu })
+        }
+    }
+
+    /// Get the Clang diagnostic information associated with this translation
+    /// unit.
+    pub(crate) fn diags(&self) -> Vec<Diagnostic> {
+        unsafe {
+            let num = clang_getNumDiagnostics(self.x) as usize;
+            let mut diags = vec![];
+            for i in 0..num {
+                diags.push(Diagnostic {
+                    x: clang_getDiagnostic(self.x, i as c_uint),
+                });
+            }
+            diags
+        }
+    }
+
+    /// Get a cursor pointing to the root of this translation unit's AST.
+    pub(crate) fn cursor(&self) -> Cursor {
+        unsafe {
+            Cursor {
+                x: clang_getTranslationUnitCursor(self.x),
+            }
+        }
+    }
+
+    /// Is this the null translation unit?
+    pub(crate) fn is_null(&self) -> bool {
+        self.x.is_null()
+    }
+}
+
+impl Drop for TranslationUnit {
+    fn drop(&mut self) {
+        unsafe {
+            clang_disposeTranslationUnit(self.x);
+        }
+    }
+}
+
+/// A diagnostic message generated while parsing a translation unit.
+pub(crate) struct Diagnostic {
+    x: CXDiagnostic,
+}
+
+impl Diagnostic {
+    /// Format this diagnostic message as a string, using the given option bit
+    /// flags.
+    pub(crate) fn format(&self) -> String {
+        unsafe {
+            let opts = clang_defaultDiagnosticDisplayOptions();
+            cxstring_into_string(clang_formatDiagnostic(self.x, opts))
+        }
+    }
+
+    /// What is the severity of this diagnostic message?
+    pub(crate) fn severity(&self) -> CXDiagnosticSeverity {
+        unsafe { clang_getDiagnosticSeverity(self.x) }
+    }
+}
+
+impl Drop for Diagnostic {
+    /// Destroy this diagnostic message.
+    fn drop(&mut self) {
+        unsafe {
+            clang_disposeDiagnostic(self.x);
+        }
+    }
+}
+
+/// A file which has not been saved to disk.
+pub(crate) struct UnsavedFile {
+    x: CXUnsavedFile,
+    /// The name of the unsaved file. Kept here to avoid leaving dangling pointers in
+    /// `CXUnsavedFile`.
+    pub(crate) name: CString,
+    contents: CString,
+}
+
+impl UnsavedFile {
+    /// Construct a new unsaved file with the given `name` and `contents`.
+    pub(crate) fn new(name: &str, contents: &str) -> UnsavedFile {
+        let name = CString::new(name.as_bytes()).unwrap();
+        let contents = CString::new(contents.as_bytes()).unwrap();
+        let x = CXUnsavedFile {
+            Filename: name.as_ptr(),
+            Contents: contents.as_ptr(),
+            Length: contents.as_bytes().len() as c_ulong,
+        };
+        UnsavedFile { x, name, contents }
+    }
+}
+
+impl fmt::Debug for UnsavedFile {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            fmt,
+            "UnsavedFile(name: {:?}, contents: {:?})",
+            self.name, self.contents
+        )
+    }
+}
+
+/// Convert a cursor kind into a static string.
+pub(crate) fn kind_to_str(x: CXCursorKind) -> String {
+    unsafe { cxstring_into_string(clang_getCursorKindSpelling(x)) }
+}
+
+/// Convert a type kind to a static string.
+pub(crate) fn type_to_str(x: CXTypeKind) -> String {
+    unsafe { cxstring_into_string(clang_getTypeKindSpelling(x)) }
+}
+
+/// Dump the Clang AST to stdout for debugging purposes.
+pub(crate) fn ast_dump(c: &Cursor, depth: isize) -> CXChildVisitResult {
+    fn print_indent<S: AsRef<str>>(depth: isize, s: S) {
+        for _ in 0..depth {
+            print!("    ");
+        }
+        println!("{}", s.as_ref());
+    }
+
+    fn print_cursor<S: AsRef<str>>(depth: isize, prefix: S, c: &Cursor) {
+        let prefix = prefix.as_ref();
+        print_indent(
+            depth,
+            format!(" {}kind = {}", prefix, kind_to_str(c.kind())),
+        );
+        print_indent(
+            depth,
+            format!(" {}spelling = \"{}\"", prefix, c.spelling()),
+        );
+        print_indent(depth, format!(" {}location = {}", prefix, c.location()));
+        print_indent(
+            depth,
+            format!(" {}is-definition? {}", prefix, c.is_definition()),
+        );
+        print_indent(
+            depth,
+            format!(" {}is-declaration? {}", prefix, c.is_declaration()),
+        );
+        print_indent(
+            depth,
+            format!(
+                " {}is-inlined-function? {}",
+                prefix,
+                c.is_inlined_function()
+            ),
+        );
+
+        let templ_kind = c.template_kind();
+        if templ_kind != CXCursor_NoDeclFound {
+            print_indent(
+                depth,
+                format!(
+                    " {}template-kind = {}",
+                    prefix,
+                    kind_to_str(templ_kind)
+                ),
+            );
+        }
+        if let Some(usr) = c.usr() {
+            print_indent(depth, format!(" {}usr = \"{}\"", prefix, usr));
+        }
+        if let Ok(num) = c.num_args() {
+            print_indent(depth, format!(" {}number-of-args = {}", prefix, num));
+        }
+        if let Some(num) = c.num_template_args() {
+            print_indent(
+                depth,
+                format!(" {}number-of-template-args = {}", prefix, num),
+            );
+        }
+
+        if c.is_bit_field() {
+            let width = match c.bit_width() {
+                Some(w) => w.to_string(),
+                None => "<unevaluable>".to_string(),
+            };
+            print_indent(depth, format!(" {}bit-width = {}", prefix, width));
+        }
+
+        if let Some(ty) = c.enum_type() {
+            print_indent(
+                depth,
+                format!(" {}enum-type = {}", prefix, type_to_str(ty.kind())),
+            );
+        }
+        if let Some(val) = c.enum_val_signed() {
+            print_indent(depth, format!(" {}enum-val = {}", prefix, val));
+        }
+        if let Some(ty) = c.typedef_type() {
+            print_indent(
+                depth,
+                format!(" {}typedef-type = {}", prefix, type_to_str(ty.kind())),
+            );
+        }
+        if let Some(ty) = c.ret_type() {
+            print_indent(
+                depth,
+                format!(" {}ret-type = {}", prefix, type_to_str(ty.kind())),
+            );
+        }
+
+        if let Some(refd) = c.referenced() {
+            if refd != *c {
+                println!();
+                print_cursor(
+                    depth,
+                    String::from(prefix) + "referenced.",
+                    &refd,
+                );
+            }
+        }
+
+        let canonical = c.canonical();
+        if canonical != *c {
+            println!();
+            print_cursor(
+                depth,
+                String::from(prefix) + "canonical.",
+                &canonical,
+            );
+        }
+
+        if let Some(specialized) = c.specialized() {
+            if specialized != *c {
+                println!();
+                print_cursor(
+                    depth,
+                    String::from(prefix) + "specialized.",
+                    &specialized,
+                );
+            }
+        }
+
+        if let Some(parent) = c.fallible_semantic_parent() {
+            println!();
+            print_cursor(
+                depth,
+                String::from(prefix) + "semantic-parent.",
+                &parent,
+            );
+        }
+    }
+
+    fn print_type<S: AsRef<str>>(depth: isize, prefix: S, ty: &Type) {
+        let prefix = prefix.as_ref();
+
+        let kind = ty.kind();
+        print_indent(depth, format!(" {}kind = {}", prefix, type_to_str(kind)));
+        if kind == CXType_Invalid {
+            return;
+        }
+
+        print_indent(depth, format!(" {}cconv = {}", prefix, ty.call_conv()));
+
+        print_indent(
+            depth,
+            format!(" {}spelling = \"{}\"", prefix, ty.spelling()),
+        );
+        let num_template_args =
+            unsafe { clang_Type_getNumTemplateArguments(ty.x) };
+        if num_template_args >= 0 {
+            print_indent(
+                depth,
+                format!(
+                    " {}number-of-template-args = {}",
+                    prefix, num_template_args
+                ),
+            );
+        }
+        if let Some(num) = ty.num_elements() {
+            print_indent(
+                depth,
+                format!(" {}number-of-elements = {}", prefix, num),
+            );
+        }
+        print_indent(
+            depth,
+            format!(" {}is-variadic? {}", prefix, ty.is_variadic()),
+        );
+
+        let canonical = ty.canonical_type();
+        if canonical != *ty {
+            println!();
+            print_type(depth, String::from(prefix) + "canonical.", &canonical);
+        }
+
+        if let Some(pointee) = ty.pointee_type() {
+            if pointee != *ty {
+                println!();
+                print_type(depth, String::from(prefix) + "pointee.", &pointee);
+            }
+        }
+
+        if let Some(elem) = ty.elem_type() {
+            if elem != *ty {
+                println!();
+                print_type(depth, String::from(prefix) + "elements.", &elem);
+            }
+        }
+
+        if let Some(ret) = ty.ret_type() {
+            if ret != *ty {
+                println!();
+                print_type(depth, String::from(prefix) + "return.", &ret);
+            }
+        }
+
+        let named = ty.named();
+        if named != *ty && named.is_valid() {
+            println!();
+            print_type(depth, String::from(prefix) + "named.", &named);
+        }
+    }
+
+    print_indent(depth, "(");
+    print_cursor(depth, "", c);
+
+    println!();
+    let ty = c.cur_type();
+    print_type(depth, "type.", &ty);
+
+    let declaration = ty.declaration();
+    if declaration != *c && declaration.kind() != CXCursor_NoDeclFound {
+        println!();
+        print_cursor(depth, "type.declaration.", &declaration);
+    }
+
+    // Recurse.
+    let mut found_children = false;
+    c.visit(|s| {
+        if !found_children {
+            println!();
+            found_children = true;
+        }
+        ast_dump(&s, depth + 1)
+    });
+
+    print_indent(depth, ")");
+
+    CXChildVisit_Continue
+}
+
+/// Try to extract the clang version to a string
+pub(crate) fn extract_clang_version() -> String {
+    unsafe { cxstring_into_string(clang_getClangVersion()) }
+}
+
+/// A wrapper for the result of evaluating an expression.
+#[derive(Debug)]
+pub(crate) struct EvalResult {
+    x: CXEvalResult,
+    ty: Type,
+}
+
+impl EvalResult {
+    /// Evaluate `cursor` and return the result.
+    pub(crate) fn new(cursor: Cursor) -> Option<Self> {
+        // Work around https://bugs.llvm.org/show_bug.cgi?id=42532, see:
+        //  * https://github.com/rust-lang/rust-bindgen/issues/283
+        //  * https://github.com/rust-lang/rust-bindgen/issues/1590
+        {
+            let mut found_cant_eval = false;
+            cursor.visit(|c| {
+                if c.kind() == CXCursor_TypeRef &&
+                    c.cur_type().canonical_type().kind() == CXType_Unexposed
+                {
+                    found_cant_eval = true;
+                    return CXChildVisit_Break;
+                }
+
+                CXChildVisit_Recurse
+            });
+
+            if found_cant_eval {
+                return None;
+            }
+        }
+        Some(EvalResult {
+            x: unsafe { clang_Cursor_Evaluate(cursor.x) },
+            ty: cursor.cur_type().canonical_type(),
+        })
+    }
+
+    fn kind(&self) -> CXEvalResultKind {
+        unsafe { clang_EvalResult_getKind(self.x) }
+    }
+
+    /// Try to get back the result as a double.
+    pub(crate) fn as_double(&self) -> Option<f64> {
+        match self.kind() {
+            CXEval_Float => {
+                Some(unsafe { clang_EvalResult_getAsDouble(self.x) })
+            }
+            _ => None,
+        }
+    }
+
+    /// Try to get back the result as an integer.
+    pub(crate) fn as_int(&self) -> Option<i64> {
+        if self.kind() != CXEval_Int {
+            return None;
+        }
+
+        if unsafe { clang_EvalResult_isUnsignedInt(self.x) } != 0 {
+            let value = unsafe { clang_EvalResult_getAsUnsigned(self.x) };
+            if value > i64::max_value() as c_ulonglong {
+                return None;
+            }
+
+            return Some(value as i64);
+        }
+
+        let value = unsafe { clang_EvalResult_getAsLongLong(self.x) };
+        if value > i64::max_value() as c_longlong {
+            return None;
+        }
+        if value < i64::min_value() as c_longlong {
+            return None;
+        }
+        #[allow(clippy::unnecessary_cast)]
+        Some(value as i64)
+    }
+
+    /// Evaluates the expression as a literal string, that may or may not be
+    /// valid utf-8.
+    pub(crate) fn as_literal_string(&self) -> Option<Vec<u8>> {
+        if self.kind() != CXEval_StrLiteral {
+            return None;
+        }
+
+        let char_ty = self.ty.pointee_type().or_else(|| self.ty.elem_type())?;
+        match char_ty.kind() {
+            CXType_Char_S | CXType_SChar | CXType_Char_U | CXType_UChar => {
+                let ret = unsafe {
+                    CStr::from_ptr(clang_EvalResult_getAsStr(self.x))
+                };
+                Some(ret.to_bytes().to_vec())
+            }
+            // FIXME: Support generating these.
+            CXType_Char16 => None,
+            CXType_Char32 => None,
+            CXType_WChar => None,
+            _ => None,
+        }
+    }
+}
+
+impl Drop for EvalResult {
+    fn drop(&mut self) {
+        unsafe { clang_EvalResult_dispose(self.x) };
+    }
+}
+/// ABI kinds as defined in
+/// <https://github.com/llvm/llvm-project/blob/ddf1de20a3f7db3bca1ef6ba7e6cbb90aac5fd2d/clang/include/clang/Basic/TargetCXXABI.def>
+#[derive(Debug, Eq, PartialEq, Copy, Clone)]
+pub(crate) enum ABIKind {
+    /// All the regular targets like Linux, Mac, WASM, etc. implement the Itanium ABI
+    GenericItanium,
+    /// The ABI used when compiling for the MSVC target
+    Microsoft,
+}
+
+/// Target information obtained from libclang.
+#[derive(Debug)]
+pub(crate) struct TargetInfo {
+    /// The target triple.
+    pub(crate) triple: String,
+    /// The width of the pointer _in bits_.
+    pub(crate) pointer_width: usize,
+    /// The ABI of the target
+    pub(crate) abi: ABIKind,
+}
+
+impl TargetInfo {
+    /// Tries to obtain target information from libclang.
+    pub(crate) fn new(tu: &TranslationUnit) -> Self {
+        let triple;
+        let pointer_width;
+        unsafe {
+            let ti = clang_getTranslationUnitTargetInfo(tu.x);
+            triple = cxstring_into_string(clang_TargetInfo_getTriple(ti));
+            pointer_width = clang_TargetInfo_getPointerWidth(ti);
+            clang_TargetInfo_dispose(ti);
+        }
+        assert!(pointer_width > 0);
+        assert_eq!(pointer_width % 8, 0);
+
+        let abi = if triple.contains("msvc") {
+            ABIKind::Microsoft
+        } else {
+            ABIKind::GenericItanium
+        };
+
+        TargetInfo {
+            triple,
+            pointer_width: pointer_width as usize,
+            abi,
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/bitfield_unit.rs b/third_party/rust/bindgen/codegen/bitfield_unit.rs
new file mode 100644
index 0000000000..73ec2bd629
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/bitfield_unit.rs
@@ -0,0 +1,102 @@
+#[repr(C)]
+#[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub struct __BindgenBitfieldUnit<Storage> {
+    storage: Storage,
+}
+
+impl<Storage> __BindgenBitfieldUnit<Storage> {
+    #[inline]
+    pub const fn new(storage: Storage) -> Self {
+        Self { storage }
+    }
+}
+
+impl<Storage> __BindgenBitfieldUnit<Storage>
+where
+    Storage: AsRef<[u8]> + AsMut<[u8]>,
+{
+    #[inline]
+    pub fn get_bit(&self, index: usize) -> bool {
+        debug_assert!(index / 8 < self.storage.as_ref().len());
+
+        let byte_index = index / 8;
+        let byte = self.storage.as_ref()[byte_index];
+
+        let bit_index = if cfg!(target_endian = "big") {
+            7 - (index % 8)
+        } else {
+            index % 8
+        };
+
+        let mask = 1 << bit_index;
+
+        byte & mask == mask
+    }
+
+    #[inline]
+    pub fn set_bit(&mut self, index: usize, val: bool) {
+        debug_assert!(index / 8 < self.storage.as_ref().len());
+
+        let byte_index = index / 8;
+        let byte = &mut self.storage.as_mut()[byte_index];
+
+        let bit_index = if cfg!(target_endian = "big") {
+            7 - (index % 8)
+        } else {
+            index % 8
+        };
+
+        let mask = 1 << bit_index;
+        if val {
+            *byte |= mask;
+        } else {
+            *byte &= !mask;
+        }
+    }
+
+    #[inline]
+    pub fn get(&self, bit_offset: usize, bit_width: u8) -> u64 {
+        debug_assert!(bit_width <= 64);
+        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
+        debug_assert!(
+            (bit_offset + (bit_width as usize)) / 8 <=
+                self.storage.as_ref().len()
+        );
+
+        let mut val = 0;
+
+        for i in 0..(bit_width as usize) {
+            if self.get_bit(i + bit_offset) {
+                let index = if cfg!(target_endian = "big") {
+                    bit_width as usize - 1 - i
+                } else {
+                    i
+                };
+                val |= 1 << index;
+            }
+        }
+
+        val
+    }
+
+    #[inline]
+    pub fn set(&mut self, bit_offset: usize, bit_width: u8, val: u64) {
+        debug_assert!(bit_width <= 64);
+        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
+        debug_assert!(
+            (bit_offset + (bit_width as usize)) / 8 <=
+                self.storage.as_ref().len()
+        );
+
+        for i in 0..(bit_width as usize) {
+            let mask = 1 << i;
+            let val_bit_is_set = val & mask == mask;
+            let index = if cfg!(target_endian = "big") {
+                bit_width as usize - 1 - i
+            } else {
+                i
+            };
+            self.set_bit(index + bit_offset, val_bit_is_set);
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/bitfield_unit_tests.rs b/third_party/rust/bindgen/codegen/bitfield_unit_tests.rs
new file mode 100644
index 0000000000..e143e4ea78
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/bitfield_unit_tests.rs
@@ -0,0 +1,260 @@
+//! Tests for `__BindgenBitfieldUnit`.
+//!
+//! Note that bit-fields are allocated right to left (least to most significant
+//! bits).
+//!
+//! From the x86 PS ABI:
+//!
+//! ```c
+//! struct {
+//!     int j : 5;
+//!     int k : 6;
+//!     int m : 7;
+//! };
+//! ```
+//!
+//! ```ignore
+//! +------------------------------------------------------------+
+//! |                     |              |            |          |
+//! |       padding       |       m      |     k      |    j     |
+//! |31                 18|17          11|10         5|4        0|
+//! +------------------------------------------------------------+
+//! ```
+
+use super::bitfield_unit::__BindgenBitfieldUnit;
+
+#[test]
+fn bitfield_unit_get_bit() {
+    let unit = __BindgenBitfieldUnit::<[u8; 2]>::new([0b10011101, 0b00011101]);
+
+    let mut bits = vec![];
+    for i in 0..16 {
+        bits.push(unit.get_bit(i));
+    }
+
+    println!();
+    println!("bits = {:?}", bits);
+    assert_eq!(
+        bits,
+        &[
+            // 0b10011101
+            true, false, true, true, true, false, false, true,
+            // 0b00011101
+            true, false, true, true, true, false, false, false
+        ]
+    );
+}
+
+#[test]
+fn bitfield_unit_set_bit() {
+    let mut unit =
+        __BindgenBitfieldUnit::<[u8; 2]>::new([0b00000000, 0b00000000]);
+
+    for i in 0..16 {
+        if i % 3 == 0 {
+            unit.set_bit(i, true);
+        }
+    }
+
+    for i in 0..16 {
+        assert_eq!(unit.get_bit(i), i % 3 == 0);
+    }
+
+    let mut unit =
+        __BindgenBitfieldUnit::<[u8; 2]>::new([0b11111111, 0b11111111]);
+
+    for i in 0..16 {
+        if i % 3 == 0 {
+            unit.set_bit(i, false);
+        }
+    }
+
+    for i in 0..16 {
+        assert_eq!(unit.get_bit(i), i % 3 != 0);
+    }
+}
+
+macro_rules! bitfield_unit_get {
+    (
+        $(
+            With $storage:expr , then get($start:expr, $len:expr) is $expected:expr;
+        )*
+    ) => {
+        #[test]
+        fn bitfield_unit_get() {
+            $({
+                let expected = $expected;
+                let unit = __BindgenBitfieldUnit::<_>::new($storage);
+                let actual = unit.get($start, $len);
+
+                println!();
+                println!("expected = {:064b}", expected);
+                println!("actual   = {:064b}", actual);
+
+                assert_eq!(expected, actual);
+            })*
+        }
+   }
+}
+
+bitfield_unit_get! {
+    // Let's just exhaustively test getting the bits from a single byte, since
+    // there are few enough combinations...
+
+    With [0b11100010], then get(0, 1) is 0;
+    With [0b11100010], then get(1, 1) is 1;
+    With [0b11100010], then get(2, 1) is 0;
+    With [0b11100010], then get(3, 1) is 0;
+    With [0b11100010], then get(4, 1) is 0;
+    With [0b11100010], then get(5, 1) is 1;
+    With [0b11100010], then get(6, 1) is 1;
+    With [0b11100010], then get(7, 1) is 1;
+
+    With [0b11100010], then get(0, 2) is 0b10;
+    With [0b11100010], then get(1, 2) is 0b01;
+    With [0b11100010], then get(2, 2) is 0b00;
+    With [0b11100010], then get(3, 2) is 0b00;
+    With [0b11100010], then get(4, 2) is 0b10;
+    With [0b11100010], then get(5, 2) is 0b11;
+    With [0b11100010], then get(6, 2) is 0b11;
+
+    With [0b11100010], then get(0, 3) is 0b010;
+    With [0b11100010], then get(1, 3) is 0b001;
+    With [0b11100010], then get(2, 3) is 0b000;
+    With [0b11100010], then get(3, 3) is 0b100;
+    With [0b11100010], then get(4, 3) is 0b110;
+    With [0b11100010], then get(5, 3) is 0b111;
+
+    With [0b11100010], then get(0, 4) is 0b0010;
+    With [0b11100010], then get(1, 4) is 0b0001;
+    With [0b11100010], then get(2, 4) is 0b1000;
+    With [0b11100010], then get(3, 4) is 0b1100;
+    With [0b11100010], then get(4, 4) is 0b1110;
+
+    With [0b11100010], then get(0, 5) is 0b00010;
+    With [0b11100010], then get(1, 5) is 0b10001;
+    With [0b11100010], then get(2, 5) is 0b11000;
+    With [0b11100010], then get(3, 5) is 0b11100;
+
+    With [0b11100010], then get(0, 6) is 0b100010;
+    With [0b11100010], then get(1, 6) is 0b110001;
+    With [0b11100010], then get(2, 6) is 0b111000;
+
+    With [0b11100010], then get(0, 7) is 0b1100010;
+    With [0b11100010], then get(1, 7) is 0b1110001;
+
+    With [0b11100010], then get(0, 8) is 0b11100010;
+
+    // OK. Now let's test getting bits from across byte boundaries.
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(0, 16) is 0b1111111101010101;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(1, 16) is 0b0111111110101010;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(2, 16) is 0b0011111111010101;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(3, 16) is 0b0001111111101010;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(4, 16) is 0b0000111111110101;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(5, 16) is 0b0000011111111010;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(6, 16) is 0b0000001111111101;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(7, 16) is 0b0000000111111110;
+
+    With [0b01010101, 0b11111111, 0b00000000, 0b11111111],
+    then get(8, 16) is 0b0000000011111111;
+}
+
+macro_rules! bitfield_unit_set {
+    (
+        $(
+            set($start:expr, $len:expr, $val:expr) is $expected:expr;
+        )*
+    ) => {
+        #[test]
+        fn bitfield_unit_set() {
+            $(
+                let mut unit = __BindgenBitfieldUnit::<[u8; 4]>::new([0, 0, 0, 0]);
+                unit.set($start, $len, $val);
+                let actual = unit.get(0, 32);
+
+                println!();
+                println!("set({}, {}, {:032b}", $start, $len, $val);
+                println!("expected = {:064b}", $expected);
+                println!("actual   = {:064b}", actual);
+
+                assert_eq!($expected, actual);
+            )*
+        }
+    }
+}
+
+bitfield_unit_set! {
+    // Once again, let's exhaustively test single byte combinations.
+
+    set(0, 1, 0b11111111) is 0b00000001;
+    set(1, 1, 0b11111111) is 0b00000010;
+    set(2, 1, 0b11111111) is 0b00000100;
+    set(3, 1, 0b11111111) is 0b00001000;
+    set(4, 1, 0b11111111) is 0b00010000;
+    set(5, 1, 0b11111111) is 0b00100000;
+    set(6, 1, 0b11111111) is 0b01000000;
+    set(7, 1, 0b11111111) is 0b10000000;
+
+    set(0, 2, 0b11111111) is 0b00000011;
+    set(1, 2, 0b11111111) is 0b00000110;
+    set(2, 2, 0b11111111) is 0b00001100;
+    set(3, 2, 0b11111111) is 0b00011000;
+    set(4, 2, 0b11111111) is 0b00110000;
+    set(5, 2, 0b11111111) is 0b01100000;
+    set(6, 2, 0b11111111) is 0b11000000;
+
+    set(0, 3, 0b11111111) is 0b00000111;
+    set(1, 3, 0b11111111) is 0b00001110;
+    set(2, 3, 0b11111111) is 0b00011100;
+    set(3, 3, 0b11111111) is 0b00111000;
+    set(4, 3, 0b11111111) is 0b01110000;
+    set(5, 3, 0b11111111) is 0b11100000;
+
+    set(0, 4, 0b11111111) is 0b00001111;
+    set(1, 4, 0b11111111) is 0b00011110;
+    set(2, 4, 0b11111111) is 0b00111100;
+    set(3, 4, 0b11111111) is 0b01111000;
+    set(4, 4, 0b11111111) is 0b11110000;
+
+    set(0, 5, 0b11111111) is 0b00011111;
+    set(1, 5, 0b11111111) is 0b00111110;
+    set(2, 5, 0b11111111) is 0b01111100;
+    set(3, 5, 0b11111111) is 0b11111000;
+
+    set(0, 6, 0b11111111) is 0b00111111;
+    set(1, 6, 0b11111111) is 0b01111110;
+    set(2, 6, 0b11111111) is 0b11111100;
+
+    set(0, 7, 0b11111111) is 0b01111111;
+    set(1, 7, 0b11111111) is 0b11111110;
+
+    set(0, 8, 0b11111111) is 0b11111111;
+
+    // And, now let's cross byte boundaries.
+
+    set(0, 16, 0b1111111111111111) is 0b00000000000000001111111111111111;
+    set(1, 16, 0b1111111111111111) is 0b00000000000000011111111111111110;
+    set(2, 16, 0b1111111111111111) is 0b00000000000000111111111111111100;
+    set(3, 16, 0b1111111111111111) is 0b00000000000001111111111111111000;
+    set(4, 16, 0b1111111111111111) is 0b00000000000011111111111111110000;
+    set(5, 16, 0b1111111111111111) is 0b00000000000111111111111111100000;
+    set(6, 16, 0b1111111111111111) is 0b00000000001111111111111111000000;
+    set(7, 16, 0b1111111111111111) is 0b00000000011111111111111110000000;
+    set(8, 16, 0b1111111111111111) is 0b00000000111111111111111100000000;
+}
diff --git a/third_party/rust/bindgen/codegen/dyngen.rs b/third_party/rust/bindgen/codegen/dyngen.rs
new file mode 100644
index 0000000000..c067fada0e
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/dyngen.rs
@@ -0,0 +1,201 @@
+use crate::codegen;
+use crate::ir::context::BindgenContext;
+use crate::ir::function::ClangAbi;
+use proc_macro2::Ident;
+
+/// Used to build the output tokens for dynamic bindings.
+#[derive(Default)]
+pub(crate) struct DynamicItems {
+    /// Tracks the tokens that will appears inside the library struct -- e.g.:
+    /// ```ignore
+    /// struct Lib {
+    ///    __library: ::libloading::Library,
+    ///    pub x: Result<unsafe extern ..., ::libloading::Error>, // <- tracks these
+    ///    ...
+    /// }
+    /// ```
+    struct_members: Vec<proc_macro2::TokenStream>,
+
+    /// Tracks the tokens that will appear inside the library struct's implementation, e.g.:
+    ///
+    /// ```ignore
+    /// impl Lib {
+    ///     ...
+    ///     pub unsafe fn foo(&self, ...) { // <- tracks these
+    ///         ...
+    ///     }
+    /// }
+    /// ```
+    struct_implementation: Vec<proc_macro2::TokenStream>,
+
+    /// Tracks the initialization of the fields inside the `::new` constructor of the library
+    /// struct, e.g.:
+    /// ```ignore
+    /// impl Lib {
+    ///
+    ///     pub unsafe fn new<P>(path: P) -> Result<Self, ::libloading::Error>
+    ///     where
+    ///         P: AsRef<::std::ffi::OsStr>,
+    ///     {
+    ///         ...
+    ///         let foo = __library.get(...) ...; // <- tracks these
+    ///         ...
+    ///     }
+    ///
+    ///     ...
+    /// }
+    /// ```
+    constructor_inits: Vec<proc_macro2::TokenStream>,
+
+    /// Tracks the information that is passed to the library struct at the end of the `::new`
+    /// constructor, e.g.:
+    /// ```ignore
+    /// impl LibFoo {
+    ///     pub unsafe fn new<P>(path: P) -> Result<Self, ::libloading::Error>
+    ///     where
+    ///         P: AsRef<::std::ffi::OsStr>,
+    ///     {
+    ///         ...
+    ///         Ok(LibFoo {
+    ///             __library: __library,
+    ///             foo,
+    ///             bar, // <- tracks these
+    ///             ...
+    ///         })
+    ///     }
+    /// }
+    /// ```
+    init_fields: Vec<proc_macro2::TokenStream>,
+}
+
+impl DynamicItems {
+    pub(crate) fn new() -> Self {
+        Self::default()
+    }
+
+    pub(crate) fn get_tokens(
+        &self,
+        lib_ident: Ident,
+        ctx: &BindgenContext,
+    ) -> proc_macro2::TokenStream {
+        let struct_members = &self.struct_members;
+        let constructor_inits = &self.constructor_inits;
+        let init_fields = &self.init_fields;
+        let struct_implementation = &self.struct_implementation;
+
+        let from_library = if ctx.options().wrap_unsafe_ops {
+            quote!(unsafe { Self::from_library(library) })
+        } else {
+            quote!(Self::from_library(library))
+        };
+
+        quote! {
+            extern crate libloading;
+
+            pub struct #lib_ident {
+                __library: ::libloading::Library,
+                #(#struct_members)*
+            }
+
+            impl #lib_ident {
+                pub unsafe fn new<P>(
+                    path: P
+                ) -> Result<Self, ::libloading::Error>
+                where P: AsRef<::std::ffi::OsStr> {
+                    let library = ::libloading::Library::new(path)?;
+                    #from_library
+                }
+
+                pub unsafe fn from_library<L>(
+                    library: L
+                ) -> Result<Self, ::libloading::Error>
+                where L: Into<::libloading::Library> {
+                    let __library = library.into();
+                    #( #constructor_inits )*
+                    Ok(#lib_ident {
+                        __library,
+                        #( #init_fields ),*
+                    })
+                }
+
+                #( #struct_implementation )*
+            }
+        }
+    }
+
+    #[allow(clippy::too_many_arguments)]
+    pub(crate) fn push(
+        &mut self,
+        ident: Ident,
+        abi: ClangAbi,
+        is_variadic: bool,
+        is_required: bool,
+        args: Vec<proc_macro2::TokenStream>,
+        args_identifiers: Vec<proc_macro2::TokenStream>,
+        ret: proc_macro2::TokenStream,
+        ret_ty: proc_macro2::TokenStream,
+        attributes: Vec<proc_macro2::TokenStream>,
+        ctx: &BindgenContext,
+    ) {
+        if !is_variadic {
+            assert_eq!(args.len(), args_identifiers.len());
+        }
+
+        let signature = quote! { unsafe extern #abi fn ( #( #args),* ) #ret };
+        let member = if is_required {
+            signature
+        } else {
+            quote! { Result<#signature, ::libloading::Error> }
+        };
+
+        self.struct_members.push(quote! {
+            pub #ident: #member,
+        });
+
+        // N.B: If the signature was required, it won't be wrapped in a Result<...>
+        //      and we can simply call it directly.
+        let fn_ = if is_required {
+            quote! { self.#ident }
+        } else {
+            quote! { self.#ident.as_ref().expect("Expected function, got error.") }
+        };
+        let call_body = if ctx.options().wrap_unsafe_ops {
+            quote!(unsafe { (#fn_)(#( #args_identifiers ),*) })
+        } else {
+            quote!((#fn_)(#( #args_identifiers ),*) )
+        };
+
+        // We can't implement variadic functions from C easily, so we allow to
+        // access the function pointer so that the user can call it just fine.
+        if !is_variadic {
+            self.struct_implementation.push(quote! {
+                #(#attributes)*
+                pub unsafe fn #ident ( &self, #( #args ),* ) #ret_ty {
+                    #call_body
+                }
+            });
+        }
+
+        // N.B: Unwrap the signature upon construction if it is required to be resolved.
+        let ident_str = codegen::helpers::ast_ty::cstr_expr(ident.to_string());
+        let library_get = if ctx.options().wrap_unsafe_ops {
+            quote!(unsafe { __library.get(#ident_str) })
+        } else {
+            quote!(__library.get(#ident_str))
+        };
+
+        self.constructor_inits.push(if is_required {
+            quote! {
+                let #ident = #library_get.map(|sym| *sym)?;
+            }
+        } else {
+            quote! {
+                let #ident = #library_get.map(|sym| *sym);
+            }
+        });
+
+        self.init_fields.push(quote! {
+            #ident
+        });
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/error.rs b/third_party/rust/bindgen/codegen/error.rs
new file mode 100644
index 0000000000..82e921d771
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/error.rs
@@ -0,0 +1,53 @@
+use std::error;
+use std::fmt;
+
+/// Errors that can occur during code generation.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) enum Error {
+    /// Tried to generate an opaque blob for a type that did not have a layout.
+    NoLayoutForOpaqueBlob,
+
+    /// Tried to instantiate an opaque template definition, or a template
+    /// definition that is too difficult for us to understand (like a partial
+    /// template specialization).
+    InstantiationOfOpaqueType,
+
+    /// Function ABI is not supported.
+    UnsupportedAbi(&'static str),
+
+    /// The pointer type size does not match the target's pointer size.
+    InvalidPointerSize {
+        ty_name: String,
+        ty_size: usize,
+        ptr_size: usize,
+    },
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::NoLayoutForOpaqueBlob => {
+                "Tried to generate an opaque blob, but had no layout.".fmt(f)
+            }
+            Error::InstantiationOfOpaqueType => {
+                "Instantiation of opaque template type or partial template specialization."
+                    .fmt(f)
+            }
+            Error::UnsupportedAbi(abi) => {
+                 write!(
+                    f,
+                    "{} ABI is not supported by the configured Rust target.",
+                    abi
+                )
+            }
+            Error::InvalidPointerSize { ty_name, ty_size, ptr_size } => {
+                write!(f, "The {} pointer type has size {} but the current target's pointer size is {}.", ty_name, ty_size, ptr_size)
+            }
+        }
+    }
+}
+
+impl error::Error for Error {}
+
+/// A `Result` of `T` or an error of `bindgen::codegen::error::Error`.
+pub(crate) type Result<T> = ::std::result::Result<T, Error>;
diff --git a/third_party/rust/bindgen/codegen/helpers.rs b/third_party/rust/bindgen/codegen/helpers.rs
new file mode 100644
index 0000000000..48bfe56dde
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/helpers.rs
@@ -0,0 +1,355 @@
+//! Helpers for code generation that don't need macro expansion.
+
+use crate::ir::context::BindgenContext;
+use crate::ir::layout::Layout;
+
+pub(crate) mod attributes {
+    use proc_macro2::{Ident, Span, TokenStream};
+    use std::{borrow::Cow, str::FromStr};
+
+    pub(crate) fn repr(which: &str) -> TokenStream {
+        let which = Ident::new(which, Span::call_site());
+        quote! {
+            #[repr( #which )]
+        }
+    }
+
+    pub(crate) fn repr_list(which_ones: &[&str]) -> TokenStream {
+        let which_ones = which_ones
+            .iter()
+            .cloned()
+            .map(|one| TokenStream::from_str(one).expect("repr to be valid"));
+        quote! {
+            #[repr( #( #which_ones ),* )]
+        }
+    }
+
+    pub(crate) fn derives(which_ones: &[&str]) -> TokenStream {
+        let which_ones = which_ones
+            .iter()
+            .cloned()
+            .map(|one| TokenStream::from_str(one).expect("derive to be valid"));
+        quote! {
+            #[derive( #( #which_ones ),* )]
+        }
+    }
+
+    pub(crate) fn inline() -> TokenStream {
+        quote! {
+            #[inline]
+        }
+    }
+
+    pub(crate) fn must_use() -> TokenStream {
+        quote! {
+            #[must_use]
+        }
+    }
+
+    pub(crate) fn non_exhaustive() -> TokenStream {
+        quote! {
+            #[non_exhaustive]
+        }
+    }
+
+    pub(crate) fn doc(comment: String) -> TokenStream {
+        if comment.is_empty() {
+            quote!()
+        } else {
+            quote!(#[doc = #comment])
+        }
+    }
+
+    pub(crate) fn link_name<const MANGLE: bool>(name: &str) -> TokenStream {
+        // LLVM mangles the name by default but it's already mangled.
+        // Prefixing the name with \u{1} should tell LLVM to not mangle it.
+        let name: Cow<'_, str> = if MANGLE {
+            name.into()
+        } else {
+            format!("\u{1}{}", name).into()
+        };
+
+        quote! {
+            #[link_name = #name]
+        }
+    }
+}
+
+/// Generates a proper type for a field or type with a given `Layout`, that is,
+/// a type with the correct size and alignment restrictions.
+pub(crate) fn blob(ctx: &BindgenContext, layout: Layout) -> syn::Type {
+    let opaque = layout.opaque();
+
+    // FIXME(emilio, #412): We fall back to byte alignment, but there are
+    // some things that legitimately are more than 8-byte aligned.
+    //
+    // Eventually we should be able to `unwrap` here, but...
+    let ty = match opaque.known_rust_type_for_array(ctx) {
+        Some(ty) => ty,
+        None => {
+            warn!("Found unknown alignment on code generation!");
+            syn::parse_quote! { u8 }
+        }
+    };
+
+    let data_len = opaque.array_size(ctx).unwrap_or(layout.size);
+
+    if data_len == 1 {
+        ty
+    } else {
+        syn::parse_quote! { [ #ty ; #data_len ] }
+    }
+}
+
+/// Integer type of the same size as the given `Layout`.
+pub(crate) fn integer_type(
+    ctx: &BindgenContext,
+    layout: Layout,
+) -> Option<syn::Type> {
+    Layout::known_type_for_size(ctx, layout.size)
+}
+
+/// Generates a bitfield allocation unit type for a type with the given `Layout`.
+pub(crate) fn bitfield_unit(ctx: &BindgenContext, layout: Layout) -> syn::Type {
+    let size = layout.size;
+    let ty = syn::parse_quote! { __BindgenBitfieldUnit<[u8; #size]> };
+
+    if ctx.options().enable_cxx_namespaces {
+        return syn::parse_quote! { root::#ty };
+    }
+
+    ty
+}
+
+pub(crate) mod ast_ty {
+    use crate::ir::context::BindgenContext;
+    use crate::ir::function::FunctionSig;
+    use crate::ir::layout::Layout;
+    use crate::ir::ty::{FloatKind, IntKind};
+    use proc_macro2::{self, TokenStream};
+    use std::str::FromStr;
+
+    pub(crate) fn c_void(ctx: &BindgenContext) -> syn::Type {
+        // ctypes_prefix takes precedence
+        match ctx.options().ctypes_prefix {
+            Some(ref prefix) => {
+                let prefix = TokenStream::from_str(prefix.as_str()).unwrap();
+                syn::parse_quote! { #prefix::c_void }
+            }
+            None => {
+                if ctx.options().use_core &&
+                    ctx.options().rust_features.core_ffi_c_void
+                {
+                    syn::parse_quote! { ::core::ffi::c_void }
+                } else {
+                    syn::parse_quote! { ::std::os::raw::c_void }
+                }
+            }
+        }
+    }
+
+    pub(crate) fn raw_type(ctx: &BindgenContext, name: &str) -> syn::Type {
+        let ident = ctx.rust_ident_raw(name);
+        match ctx.options().ctypes_prefix {
+            Some(ref prefix) => {
+                let prefix = TokenStream::from_str(prefix.as_str()).unwrap();
+                syn::parse_quote! { #prefix::#ident }
+            }
+            None => {
+                if ctx.options().use_core &&
+                    ctx.options().rust_features().core_ffi_c
+                {
+                    syn::parse_quote! { ::core::ffi::#ident }
+                } else {
+                    syn::parse_quote! { ::std::os::raw::#ident }
+                }
+            }
+        }
+    }
+
+    pub(crate) fn int_kind_rust_type(
+        ctx: &BindgenContext,
+        ik: IntKind,
+        layout: Option<Layout>,
+    ) -> syn::Type {
+        match ik {
+            IntKind::Bool => syn::parse_quote! { bool },
+            IntKind::Char { .. } => raw_type(ctx, "c_char"),
+            IntKind::SChar => raw_type(ctx, "c_schar"),
+            IntKind::UChar => raw_type(ctx, "c_uchar"),
+            IntKind::Short => raw_type(ctx, "c_short"),
+            IntKind::UShort => raw_type(ctx, "c_ushort"),
+            IntKind::Int => raw_type(ctx, "c_int"),
+            IntKind::UInt => raw_type(ctx, "c_uint"),
+            IntKind::Long => raw_type(ctx, "c_long"),
+            IntKind::ULong => raw_type(ctx, "c_ulong"),
+            IntKind::LongLong => raw_type(ctx, "c_longlong"),
+            IntKind::ULongLong => raw_type(ctx, "c_ulonglong"),
+            IntKind::WChar => {
+                let layout =
+                    layout.expect("Couldn't compute wchar_t's layout?");
+                Layout::known_type_for_size(ctx, layout.size)
+                    .expect("Non-representable wchar_t?")
+            }
+
+            IntKind::I8 => syn::parse_quote! { i8 },
+            IntKind::U8 => syn::parse_quote! { u8 },
+            IntKind::I16 => syn::parse_quote! { i16 },
+            IntKind::U16 => syn::parse_quote! { u16 },
+            IntKind::I32 => syn::parse_quote! { i32 },
+            IntKind::U32 => syn::parse_quote! { u32 },
+            IntKind::I64 => syn::parse_quote! { i64 },
+            IntKind::U64 => syn::parse_quote! { u64 },
+            IntKind::Custom { name, .. } => {
+                syn::parse_str(name).expect("Invalid integer type.")
+            }
+            IntKind::U128 => {
+                if ctx.options().rust_features.i128_and_u128 {
+                    syn::parse_quote! { u128 }
+                } else {
+                    // Best effort thing, but wrong alignment
+                    // unfortunately.
+                    syn::parse_quote! { [u64; 2] }
+                }
+            }
+            IntKind::I128 => {
+                if ctx.options().rust_features.i128_and_u128 {
+                    syn::parse_quote! { i128 }
+                } else {
+                    syn::parse_quote! { [u64; 2] }
+                }
+            }
+        }
+    }
+
+    pub(crate) fn float_kind_rust_type(
+        ctx: &BindgenContext,
+        fk: FloatKind,
+        layout: Option<Layout>,
+    ) -> syn::Type {
+        // TODO: we probably should take the type layout into account more
+        // often?
+        //
+        // Also, maybe this one shouldn't be the default?
+        match (fk, ctx.options().convert_floats) {
+            (FloatKind::Float16, _) => {
+                // TODO: do f16 when rust lands it
+                ctx.generated_bindgen_float16();
+                if ctx.options().enable_cxx_namespaces {
+                    syn::parse_quote! { root::__BindgenFloat16 }
+                } else {
+                    syn::parse_quote! { __BindgenFloat16 }
+                }
+            }
+            (FloatKind::Float, true) => syn::parse_quote! { f32 },
+            (FloatKind::Double, true) => syn::parse_quote! { f64 },
+            (FloatKind::Float, false) => raw_type(ctx, "c_float"),
+            (FloatKind::Double, false) => raw_type(ctx, "c_double"),
+            (FloatKind::LongDouble, _) => {
+                match layout {
+                    Some(layout) => {
+                        match layout.size {
+                            4 => syn::parse_quote! { f32 },
+                            8 => syn::parse_quote! { f64 },
+                            // TODO(emilio): If rust ever gains f128 we should
+                            // use it here and below.
+                            _ => super::integer_type(ctx, layout)
+                                .unwrap_or(syn::parse_quote! { f64 }),
+                        }
+                    }
+                    None => {
+                        debug_assert!(
+                            false,
+                            "How didn't we know the layout for a primitive type?"
+                        );
+                        syn::parse_quote! { f64 }
+                    }
+                }
+            }
+            (FloatKind::Float128, _) => {
+                if ctx.options().rust_features.i128_and_u128 {
+                    syn::parse_quote! { u128 }
+                } else {
+                    syn::parse_quote! { [u64; 2] }
+                }
+            }
+        }
+    }
+
+    pub(crate) fn int_expr(val: i64) -> TokenStream {
+        // Don't use quote! { #val } because that adds the type suffix.
+        let val = proc_macro2::Literal::i64_unsuffixed(val);
+        quote!(#val)
+    }
+
+    pub(crate) fn uint_expr(val: u64) -> TokenStream {
+        // Don't use quote! { #val } because that adds the type suffix.
+        let val = proc_macro2::Literal::u64_unsuffixed(val);
+        quote!(#val)
+    }
+
+    pub(crate) fn cstr_expr(mut string: String) -> TokenStream {
+        string.push('\0');
+        let b = proc_macro2::Literal::byte_string(string.as_bytes());
+        quote! {
+            #b
+        }
+    }
+
+    pub(crate) fn float_expr(
+        ctx: &BindgenContext,
+        f: f64,
+    ) -> Result<TokenStream, ()> {
+        if f.is_finite() {
+            let val = proc_macro2::Literal::f64_unsuffixed(f);
+
+            return Ok(quote!(#val));
+        }
+
+        let prefix = ctx.trait_prefix();
+
+        if f.is_nan() {
+            return Ok(quote! {
+                ::#prefix::f64::NAN
+            });
+        }
+
+        if f.is_infinite() {
+            return Ok(if f.is_sign_positive() {
+                quote! {
+                    ::#prefix::f64::INFINITY
+                }
+            } else {
+                quote! {
+                    ::#prefix::f64::NEG_INFINITY
+                }
+            });
+        }
+
+        warn!("Unknown non-finite float number: {:?}", f);
+        Err(())
+    }
+
+    pub(crate) fn arguments_from_signature(
+        signature: &FunctionSig,
+        ctx: &BindgenContext,
+    ) -> Vec<TokenStream> {
+        let mut unnamed_arguments = 0;
+        signature
+            .argument_types()
+            .iter()
+            .map(|&(ref name, _ty)| match *name {
+                Some(ref name) => {
+                    let name = ctx.rust_ident(name);
+                    quote! { #name }
+                }
+                None => {
+                    unnamed_arguments += 1;
+                    let name =
+                        ctx.rust_ident(format!("arg{}", unnamed_arguments));
+                    quote! { #name }
+                }
+            })
+            .collect()
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/impl_debug.rs b/third_party/rust/bindgen/codegen/impl_debug.rs
new file mode 100644
index 0000000000..67ec214ee8
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/impl_debug.rs
@@ -0,0 +1,245 @@
+use crate::ir::comp::{BitfieldUnit, CompKind, Field, FieldData, FieldMethods};
+use crate::ir::context::BindgenContext;
+use crate::ir::item::{HasTypeParamInArray, IsOpaque, Item, ItemCanonicalName};
+use crate::ir::ty::{TypeKind, RUST_DERIVE_IN_ARRAY_LIMIT};
+
+pub(crate) fn gen_debug_impl(
+    ctx: &BindgenContext,
+    fields: &[Field],
+    item: &Item,
+    kind: CompKind,
+) -> proc_macro2::TokenStream {
+    let struct_name = item.canonical_name(ctx);
+    let mut format_string = format!("{} {{{{ ", struct_name);
+    let mut tokens = vec![];
+
+    if item.is_opaque(ctx, &()) {
+        format_string.push_str("opaque");
+    } else {
+        match kind {
+            CompKind::Union => {
+                format_string.push_str("union");
+            }
+            CompKind::Struct => {
+                let processed_fields = fields.iter().filter_map(|f| match f {
+                    Field::DataMember(ref fd) => fd.impl_debug(ctx, ()),
+                    Field::Bitfields(ref bu) => bu.impl_debug(ctx, ()),
+                });
+
+                for (i, (fstring, toks)) in processed_fields.enumerate() {
+                    if i > 0 {
+                        format_string.push_str(", ");
+                    }
+                    tokens.extend(toks);
+                    format_string.push_str(&fstring);
+                }
+            }
+        }
+    }
+
+    format_string.push_str(" }}");
+    tokens.insert(0, quote! { #format_string });
+
+    let prefix = ctx.trait_prefix();
+
+    quote! {
+        fn fmt(&self, f: &mut ::#prefix::fmt::Formatter<'_>) -> ::#prefix ::fmt::Result {
+            write!(f, #( #tokens ),*)
+        }
+    }
+}
+
+/// A trait for the things which we can codegen tokens that contribute towards a
+/// generated `impl Debug`.
+pub(crate) trait ImplDebug<'a> {
+    /// Any extra parameter required by this a particular `ImplDebug` implementation.
+    type Extra;
+
+    /// Generate a format string snippet to be included in the larger `impl Debug`
+    /// format string, and the code to get the format string's interpolation values.
+    fn impl_debug(
+        &self,
+        ctx: &BindgenContext,
+        extra: Self::Extra,
+    ) -> Option<(String, Vec<proc_macro2::TokenStream>)>;
+}
+
+impl<'a> ImplDebug<'a> for FieldData {
+    type Extra = ();
+
+    fn impl_debug(
+        &self,
+        ctx: &BindgenContext,
+        _: Self::Extra,
+    ) -> Option<(String, Vec<proc_macro2::TokenStream>)> {
+        if let Some(name) = self.name() {
+            ctx.resolve_item(self.ty()).impl_debug(ctx, name)
+        } else {
+            None
+        }
+    }
+}
+
+impl<'a> ImplDebug<'a> for BitfieldUnit {
+    type Extra = ();
+
+    fn impl_debug(
+        &self,
+        ctx: &BindgenContext,
+        _: Self::Extra,
+    ) -> Option<(String, Vec<proc_macro2::TokenStream>)> {
+        let mut format_string = String::new();
+        let mut tokens = vec![];
+        for (i, bitfield) in self.bitfields().iter().enumerate() {
+            if i > 0 {
+                format_string.push_str(", ");
+            }
+
+            if let Some(bitfield_name) = bitfield.name() {
+                format_string.push_str(&format!("{} : {{:?}}", bitfield_name));
+                let getter_name = bitfield.getter_name();
+                let name_ident = ctx.rust_ident_raw(getter_name);
+                tokens.push(quote! {
+                    self.#name_ident ()
+                });
+            }
+        }
+
+        Some((format_string, tokens))
+    }
+}
+
+impl<'a> ImplDebug<'a> for Item {
+    type Extra = &'a str;
+
+    fn impl_debug(
+        &self,
+        ctx: &BindgenContext,
+        name: &str,
+    ) -> Option<(String, Vec<proc_macro2::TokenStream>)> {
+        let name_ident = ctx.rust_ident(name);
+
+        // We don't know if blocklisted items `impl Debug` or not, so we can't
+        // add them to the format string we're building up.
+        if !ctx.allowlisted_items().contains(&self.id()) {
+            return None;
+        }
+
+        let ty = match self.as_type() {
+            Some(ty) => ty,
+            None => {
+                return None;
+            }
+        };
+
+        fn debug_print(
+            name: &str,
+            name_ident: proc_macro2::TokenStream,
+        ) -> Option<(String, Vec<proc_macro2::TokenStream>)> {
+            Some((
+                format!("{}: {{:?}}", name),
+                vec![quote! {
+                    self.#name_ident
+                }],
+            ))
+        }
+
+        match *ty.kind() {
+            // Handle the simple cases.
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Int(..) |
+            TypeKind::Float(..) |
+            TypeKind::Complex(..) |
+            TypeKind::Function(..) |
+            TypeKind::Enum(..) |
+            TypeKind::Reference(..) |
+            TypeKind::UnresolvedTypeRef(..) |
+            TypeKind::ObjCInterface(..) |
+            TypeKind::ObjCId |
+            TypeKind::Comp(..) |
+            TypeKind::ObjCSel => debug_print(name, quote! { #name_ident }),
+
+            TypeKind::TemplateInstantiation(ref inst) => {
+                if inst.is_opaque(ctx, self) {
+                    Some((format!("{}: opaque", name), vec![]))
+                } else {
+                    debug_print(name, quote! { #name_ident })
+                }
+            }
+
+            // The generic is not required to implement Debug, so we can not debug print that type
+            TypeKind::TypeParam => {
+                Some((format!("{}: Non-debuggable generic", name), vec![]))
+            }
+
+            TypeKind::Array(_, len) => {
+                // Generics are not required to implement Debug
+                if self.has_type_param_in_array(ctx) {
+                    Some((
+                        format!("{}: Array with length {}", name, len),
+                        vec![],
+                    ))
+                } else if len < RUST_DERIVE_IN_ARRAY_LIMIT ||
+                    ctx.options().rust_features().larger_arrays
+                {
+                    // The simple case
+                    debug_print(name, quote! { #name_ident })
+                } else if ctx.options().use_core {
+                    // There is no String in core; reducing field visibility to avoid breaking
+                    // no_std setups.
+                    Some((format!("{}: [...]", name), vec![]))
+                } else {
+                    // Let's implement our own print function
+                    Some((
+                        format!("{}: [{{}}]", name),
+                        vec![quote! {
+                            self.#name_ident
+                                .iter()
+                                .enumerate()
+                                .map(|(i, v)| format!("{}{:?}", if i > 0 { ", " } else { "" }, v))
+                                .collect::<String>()
+                        }],
+                    ))
+                }
+            }
+            TypeKind::Vector(_, len) => {
+                if ctx.options().use_core {
+                    // There is no format! in core; reducing field visibility to avoid breaking
+                    // no_std setups.
+                    Some((format!("{}(...)", name), vec![]))
+                } else {
+                    let self_ids = 0..len;
+                    Some((
+                        format!("{}({{}})", name),
+                        vec![quote! {
+                            #(format!("{:?}", self.#self_ids)),*
+                        }],
+                    ))
+                }
+            }
+
+            TypeKind::ResolvedTypeRef(t) |
+            TypeKind::TemplateAlias(t, _) |
+            TypeKind::Alias(t) |
+            TypeKind::BlockPointer(t) => {
+                // We follow the aliases
+                ctx.resolve_item(t).impl_debug(ctx, name)
+            }
+
+            TypeKind::Pointer(inner) => {
+                let inner_type = ctx.resolve_type(inner).canonical_type(ctx);
+                match *inner_type.kind() {
+                    TypeKind::Function(ref sig)
+                        if !sig.function_pointers_can_derive() =>
+                    {
+                        Some((format!("{}: FunctionPointer", name), vec![]))
+                    }
+                    _ => debug_print(name, quote! { #name_ident }),
+                }
+            }
+
+            TypeKind::Opaque => None,
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/impl_partialeq.rs b/third_party/rust/bindgen/codegen/impl_partialeq.rs
new file mode 100644
index 0000000000..42fabf6ad0
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/impl_partialeq.rs
@@ -0,0 +1,142 @@
+use crate::ir::comp::{CompInfo, CompKind, Field, FieldMethods};
+use crate::ir::context::BindgenContext;
+use crate::ir::item::{IsOpaque, Item};
+use crate::ir::ty::{TypeKind, RUST_DERIVE_IN_ARRAY_LIMIT};
+
+/// Generate a manual implementation of `PartialEq` trait for the
+/// specified compound type.
+pub(crate) fn gen_partialeq_impl(
+    ctx: &BindgenContext,
+    comp_info: &CompInfo,
+    item: &Item,
+    ty_for_impl: &proc_macro2::TokenStream,
+) -> Option<proc_macro2::TokenStream> {
+    let mut tokens = vec![];
+
+    if item.is_opaque(ctx, &()) {
+        tokens.push(quote! {
+            &self._bindgen_opaque_blob[..] == &other._bindgen_opaque_blob[..]
+        });
+    } else if comp_info.kind() == CompKind::Union {
+        assert!(!ctx.options().untagged_union);
+        tokens.push(quote! {
+            &self.bindgen_union_field[..] == &other.bindgen_union_field[..]
+        });
+    } else {
+        for base in comp_info.base_members().iter() {
+            if !base.requires_storage(ctx) {
+                continue;
+            }
+
+            let ty_item = ctx.resolve_item(base.ty);
+            let field_name = &base.field_name;
+
+            if ty_item.is_opaque(ctx, &()) {
+                let field_name = ctx.rust_ident(field_name);
+                tokens.push(quote! {
+                    &self. #field_name [..] == &other. #field_name [..]
+                });
+            } else {
+                tokens.push(gen_field(ctx, ty_item, field_name));
+            }
+        }
+
+        for field in comp_info.fields() {
+            match *field {
+                Field::DataMember(ref fd) => {
+                    let ty_item = ctx.resolve_item(fd.ty());
+                    let name = fd.name().unwrap();
+                    tokens.push(gen_field(ctx, ty_item, name));
+                }
+                Field::Bitfields(ref bu) => {
+                    for bitfield in bu.bitfields() {
+                        if bitfield.name().is_some() {
+                            let getter_name = bitfield.getter_name();
+                            let name_ident = ctx.rust_ident_raw(getter_name);
+                            tokens.push(quote! {
+                                self.#name_ident () == other.#name_ident ()
+                            });
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    Some(quote! {
+        fn eq(&self, other: & #ty_for_impl) -> bool {
+            #( #tokens )&&*
+        }
+    })
+}
+
+fn gen_field(
+    ctx: &BindgenContext,
+    ty_item: &Item,
+    name: &str,
+) -> proc_macro2::TokenStream {
+    fn quote_equals(
+        name_ident: proc_macro2::Ident,
+    ) -> proc_macro2::TokenStream {
+        quote! { self.#name_ident == other.#name_ident }
+    }
+
+    let name_ident = ctx.rust_ident(name);
+    let ty = ty_item.expect_type();
+
+    match *ty.kind() {
+        TypeKind::Void |
+        TypeKind::NullPtr |
+        TypeKind::Int(..) |
+        TypeKind::Complex(..) |
+        TypeKind::Float(..) |
+        TypeKind::Enum(..) |
+        TypeKind::TypeParam |
+        TypeKind::UnresolvedTypeRef(..) |
+        TypeKind::Reference(..) |
+        TypeKind::ObjCInterface(..) |
+        TypeKind::ObjCId |
+        TypeKind::ObjCSel |
+        TypeKind::Comp(..) |
+        TypeKind::Pointer(_) |
+        TypeKind::Function(..) |
+        TypeKind::Opaque => quote_equals(name_ident),
+
+        TypeKind::TemplateInstantiation(ref inst) => {
+            if inst.is_opaque(ctx, ty_item) {
+                quote! {
+                    &self. #name_ident [..] == &other. #name_ident [..]
+                }
+            } else {
+                quote_equals(name_ident)
+            }
+        }
+
+        TypeKind::Array(_, len) => {
+            if len <= RUST_DERIVE_IN_ARRAY_LIMIT ||
+                ctx.options().rust_features().larger_arrays
+            {
+                quote_equals(name_ident)
+            } else {
+                quote! {
+                    &self. #name_ident [..] == &other. #name_ident [..]
+                }
+            }
+        }
+        TypeKind::Vector(_, len) => {
+            let self_ids = 0..len;
+            let other_ids = 0..len;
+            quote! {
+                #(self.#self_ids == other.#other_ids &&)* true
+            }
+        }
+
+        TypeKind::ResolvedTypeRef(t) |
+        TypeKind::TemplateAlias(t, _) |
+        TypeKind::Alias(t) |
+        TypeKind::BlockPointer(t) => {
+            let inner_item = ctx.resolve_item(t);
+            gen_field(ctx, inner_item, name)
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/mod.rs b/third_party/rust/bindgen/codegen/mod.rs
new file mode 100644
index 0000000000..dd1486df74
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/mod.rs
@@ -0,0 +1,5473 @@
+mod dyngen;
+pub(crate) mod error;
+
+mod helpers;
+mod impl_debug;
+mod impl_partialeq;
+mod postprocessing;
+mod serialize;
+pub(crate) mod struct_layout;
+
+#[cfg(test)]
+#[allow(warnings)]
+pub(crate) mod bitfield_unit;
+#[cfg(all(test, target_endian = "little"))]
+mod bitfield_unit_tests;
+
+use self::dyngen::DynamicItems;
+use self::helpers::attributes;
+use self::struct_layout::StructLayoutTracker;
+
+use super::BindgenOptions;
+
+use crate::callbacks::{DeriveInfo, FieldInfo, TypeKind as DeriveTypeKind};
+use crate::codegen::error::Error;
+use crate::ir::analysis::{HasVtable, Sizedness};
+use crate::ir::annotations::{
+    Annotations, FieldAccessorKind, FieldVisibilityKind,
+};
+use crate::ir::comp::{
+    Bitfield, BitfieldUnit, CompInfo, CompKind, Field, FieldData, FieldMethods,
+    Method, MethodKind,
+};
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::derive::{
+    CanDerive, CanDeriveCopy, CanDeriveDebug, CanDeriveDefault, CanDeriveEq,
+    CanDeriveHash, CanDeriveOrd, CanDerivePartialEq, CanDerivePartialOrd,
+};
+use crate::ir::dot;
+use crate::ir::enum_ty::{Enum, EnumVariant, EnumVariantValue};
+use crate::ir::function::{
+    ClangAbi, Function, FunctionKind, FunctionSig, Linkage,
+};
+use crate::ir::int::IntKind;
+use crate::ir::item::{IsOpaque, Item, ItemCanonicalName, ItemCanonicalPath};
+use crate::ir::item_kind::ItemKind;
+use crate::ir::layout::Layout;
+use crate::ir::module::Module;
+use crate::ir::objc::{ObjCInterface, ObjCMethod};
+use crate::ir::template::{
+    AsTemplateParam, TemplateInstantiation, TemplateParameters,
+};
+use crate::ir::ty::{Type, TypeKind};
+use crate::ir::var::Var;
+
+use proc_macro2::{self, Ident, Span};
+use quote::TokenStreamExt;
+
+use crate::{Entry, HashMap, HashSet};
+use std::borrow::Cow;
+use std::cell::Cell;
+use std::collections::VecDeque;
+use std::ffi::CStr;
+use std::fmt::{self, Write};
+use std::ops;
+use std::str::{self, FromStr};
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum CodegenError {
+    Serialize { msg: String, loc: String },
+    Io(String),
+}
+
+impl From<std::io::Error> for CodegenError {
+    fn from(err: std::io::Error) -> Self {
+        Self::Io(err.to_string())
+    }
+}
+
+impl fmt::Display for CodegenError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Serialize { msg, loc } => {
+                write!(f, "serialization error at {}: {}", loc, msg)
+            }
+            Self::Io(err) => err.fmt(f),
+        }
+    }
+}
+
+// Name of type defined in constified enum module
+pub(crate) static CONSTIFIED_ENUM_MODULE_REPR_NAME: &str = "Type";
+
+fn top_level_path(
+    ctx: &BindgenContext,
+    item: &Item,
+) -> Vec<proc_macro2::TokenStream> {
+    let mut path = vec![quote! { self }];
+
+    if ctx.options().enable_cxx_namespaces {
+        for _ in 0..item.codegen_depth(ctx) {
+            path.push(quote! { super });
+        }
+    }
+
+    path
+}
+
+fn root_import(
+    ctx: &BindgenContext,
+    module: &Item,
+) -> proc_macro2::TokenStream {
+    assert!(ctx.options().enable_cxx_namespaces, "Somebody messed it up");
+    assert!(module.is_module());
+
+    let mut path = top_level_path(ctx, module);
+
+    let root = ctx.root_module().canonical_name(ctx);
+    let root_ident = ctx.rust_ident(root);
+    path.push(quote! { #root_ident });
+
+    let mut tokens = quote! {};
+    tokens.append_separated(path, quote!(::));
+
+    quote! {
+        #[allow(unused_imports)]
+        use #tokens ;
+    }
+}
+
+bitflags! {
+    #[derive(Copy, Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+    struct DerivableTraits: u16 {
+        const DEBUG       = 1 << 0;
+        const DEFAULT     = 1 << 1;
+        const COPY        = 1 << 2;
+        const CLONE       = 1 << 3;
+        const HASH        = 1 << 4;
+        const PARTIAL_ORD = 1 << 5;
+        const ORD         = 1 << 6;
+        const PARTIAL_EQ  = 1 << 7;
+        const EQ          = 1 << 8;
+    }
+}
+
+fn derives_of_item(
+    item: &Item,
+    ctx: &BindgenContext,
+    packed: bool,
+) -> DerivableTraits {
+    let mut derivable_traits = DerivableTraits::empty();
+
+    let all_template_params = item.all_template_params(ctx);
+
+    if item.can_derive_copy(ctx) && !item.annotations().disallow_copy() {
+        derivable_traits |= DerivableTraits::COPY;
+
+        if ctx.options().rust_features().builtin_clone_impls ||
+            !all_template_params.is_empty()
+        {
+            // FIXME: This requires extra logic if you have a big array in a
+            // templated struct. The reason for this is that the magic:
+            //     fn clone(&self) -> Self { *self }
+            // doesn't work for templates.
+            //
+            // It's not hard to fix though.
+            derivable_traits |= DerivableTraits::CLONE;
+        }
+    } else if packed {
+        // If the struct or union is packed, deriving from Copy is required for
+        // deriving from any other trait.
+        return derivable_traits;
+    }
+
+    if item.can_derive_debug(ctx) && !item.annotations().disallow_debug() {
+        derivable_traits |= DerivableTraits::DEBUG;
+    }
+
+    if item.can_derive_default(ctx) && !item.annotations().disallow_default() {
+        derivable_traits |= DerivableTraits::DEFAULT;
+    }
+
+    if item.can_derive_hash(ctx) {
+        derivable_traits |= DerivableTraits::HASH;
+    }
+
+    if item.can_derive_partialord(ctx) {
+        derivable_traits |= DerivableTraits::PARTIAL_ORD;
+    }
+
+    if item.can_derive_ord(ctx) {
+        derivable_traits |= DerivableTraits::ORD;
+    }
+
+    if item.can_derive_partialeq(ctx) {
+        derivable_traits |= DerivableTraits::PARTIAL_EQ;
+    }
+
+    if item.can_derive_eq(ctx) {
+        derivable_traits |= DerivableTraits::EQ;
+    }
+
+    derivable_traits
+}
+
+impl From<DerivableTraits> for Vec<&'static str> {
+    fn from(derivable_traits: DerivableTraits) -> Vec<&'static str> {
+        [
+            (DerivableTraits::DEBUG, "Debug"),
+            (DerivableTraits::DEFAULT, "Default"),
+            (DerivableTraits::COPY, "Copy"),
+            (DerivableTraits::CLONE, "Clone"),
+            (DerivableTraits::HASH, "Hash"),
+            (DerivableTraits::PARTIAL_ORD, "PartialOrd"),
+            (DerivableTraits::ORD, "Ord"),
+            (DerivableTraits::PARTIAL_EQ, "PartialEq"),
+            (DerivableTraits::EQ, "Eq"),
+        ]
+        .iter()
+        .filter_map(|&(flag, derive)| {
+            Some(derive).filter(|_| derivable_traits.contains(flag))
+        })
+        .collect()
+    }
+}
+
+struct WrapAsVariadic {
+    new_name: String,
+    idx_of_va_list_arg: usize,
+}
+
+struct CodegenResult<'a> {
+    items: Vec<proc_macro2::TokenStream>,
+    dynamic_items: DynamicItems,
+
+    /// A monotonic counter used to add stable unique ID's to stuff that doesn't
+    /// need to be referenced by anything.
+    codegen_id: &'a Cell<usize>,
+
+    /// Whether a bindgen union has been generated at least once.
+    saw_bindgen_union: bool,
+
+    /// Whether an incomplete array has been generated at least once.
+    saw_incomplete_array: bool,
+
+    /// Whether Objective C types have been seen at least once.
+    saw_objc: bool,
+
+    /// Whether Apple block types have been seen at least once.
+    saw_block: bool,
+
+    /// Whether a bitfield allocation unit has been seen at least once.
+    saw_bitfield_unit: bool,
+
+    items_seen: HashSet<ItemId>,
+    /// The set of generated function/var names, needed because in C/C++ is
+    /// legal to do something like:
+    ///
+    /// ```c++
+    /// extern "C" {
+    ///   void foo();
+    ///   extern int bar;
+    /// }
+    ///
+    /// extern "C" {
+    ///   void foo();
+    ///   extern int bar;
+    /// }
+    /// ```
+    ///
+    /// Being these two different declarations.
+    functions_seen: HashSet<String>,
+    vars_seen: HashSet<String>,
+
+    /// Used for making bindings to overloaded functions. Maps from a canonical
+    /// function name to the number of overloads we have already codegen'd for
+    /// that name. This lets us give each overload a unique suffix.
+    overload_counters: HashMap<String, u32>,
+
+    /// List of items to serialize. With optionally the argument for the wrap as
+    /// variadic transformation to be applied.
+    items_to_serialize: Vec<(ItemId, Option<WrapAsVariadic>)>,
+}
+
+impl<'a> CodegenResult<'a> {
+    fn new(codegen_id: &'a Cell<usize>) -> Self {
+        CodegenResult {
+            items: vec![],
+            dynamic_items: DynamicItems::new(),
+            saw_bindgen_union: false,
+            saw_incomplete_array: false,
+            saw_objc: false,
+            saw_block: false,
+            saw_bitfield_unit: false,
+            codegen_id,
+            items_seen: Default::default(),
+            functions_seen: Default::default(),
+            vars_seen: Default::default(),
+            overload_counters: Default::default(),
+            items_to_serialize: Default::default(),
+        }
+    }
+
+    fn dynamic_items(&mut self) -> &mut DynamicItems {
+        &mut self.dynamic_items
+    }
+
+    fn saw_bindgen_union(&mut self) {
+        self.saw_bindgen_union = true;
+    }
+
+    fn saw_incomplete_array(&mut self) {
+        self.saw_incomplete_array = true;
+    }
+
+    fn saw_objc(&mut self) {
+        self.saw_objc = true;
+    }
+
+    fn saw_block(&mut self) {
+        self.saw_block = true;
+    }
+
+    fn saw_bitfield_unit(&mut self) {
+        self.saw_bitfield_unit = true;
+    }
+
+    fn seen<Id: Into<ItemId>>(&self, item: Id) -> bool {
+        self.items_seen.contains(&item.into())
+    }
+
+    fn set_seen<Id: Into<ItemId>>(&mut self, item: Id) {
+        self.items_seen.insert(item.into());
+    }
+
+    fn seen_function(&self, name: &str) -> bool {
+        self.functions_seen.contains(name)
+    }
+
+    fn saw_function(&mut self, name: &str) {
+        self.functions_seen.insert(name.into());
+    }
+
+    /// Get the overload number for the given function name. Increments the
+    /// counter internally so the next time we ask for the overload for this
+    /// name, we get the incremented value, and so on.
+    fn overload_number(&mut self, name: &str) -> u32 {
+        let counter = self.overload_counters.entry(name.into()).or_insert(0);
+        let number = *counter;
+        *counter += 1;
+        number
+    }
+
+    fn seen_var(&self, name: &str) -> bool {
+        self.vars_seen.contains(name)
+    }
+
+    fn saw_var(&mut self, name: &str) {
+        self.vars_seen.insert(name.into());
+    }
+
+    fn inner<F>(&mut self, cb: F) -> Vec<proc_macro2::TokenStream>
+    where
+        F: FnOnce(&mut Self),
+    {
+        let mut new = Self::new(self.codegen_id);
+
+        cb(&mut new);
+
+        self.saw_incomplete_array |= new.saw_incomplete_array;
+        self.saw_objc |= new.saw_objc;
+        self.saw_block |= new.saw_block;
+        self.saw_bitfield_unit |= new.saw_bitfield_unit;
+        self.saw_bindgen_union |= new.saw_bindgen_union;
+
+        new.items
+    }
+}
+
+impl<'a> ops::Deref for CodegenResult<'a> {
+    type Target = Vec<proc_macro2::TokenStream>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.items
+    }
+}
+
+impl<'a> ops::DerefMut for CodegenResult<'a> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.items
+    }
+}
+
+/// A trait to convert a rust type into a pointer, optionally const, to the same
+/// type.
+trait ToPtr {
+    fn to_ptr(self, is_const: bool) -> syn::Type;
+}
+
+impl ToPtr for syn::Type {
+    fn to_ptr(self, is_const: bool) -> syn::Type {
+        if is_const {
+            syn::parse_quote! { *const #self }
+        } else {
+            syn::parse_quote! { *mut #self }
+        }
+    }
+}
+
+/// An extension trait for `syn::Type` that lets us append any implicit
+/// template parameters that exist for some type, if necessary.
+trait WithImplicitTemplateParams {
+    fn with_implicit_template_params(
+        self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> Self;
+}
+
+impl WithImplicitTemplateParams for syn::Type {
+    fn with_implicit_template_params(
+        self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> Self {
+        let item = item.id().into_resolver().through_type_refs().resolve(ctx);
+
+        let params = match *item.expect_type().kind() {
+            TypeKind::UnresolvedTypeRef(..) => {
+                unreachable!("already resolved unresolved type refs")
+            }
+            TypeKind::ResolvedTypeRef(..) => {
+                unreachable!("we resolved item through type refs")
+            }
+            // None of these types ever have implicit template parameters.
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Pointer(..) |
+            TypeKind::Reference(..) |
+            TypeKind::Int(..) |
+            TypeKind::Float(..) |
+            TypeKind::Complex(..) |
+            TypeKind::Array(..) |
+            TypeKind::TypeParam |
+            TypeKind::Opaque |
+            TypeKind::Function(..) |
+            TypeKind::Enum(..) |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel |
+            TypeKind::TemplateInstantiation(..) => None,
+            _ => {
+                let params = item.used_template_params(ctx);
+                if params.is_empty() {
+                    None
+                } else {
+                    Some(params.into_iter().map(|p| {
+                        p.try_to_rust_ty(ctx, &()).expect(
+                            "template params cannot fail to be a rust type",
+                        )
+                    }))
+                }
+            }
+        };
+
+        if let Some(params) = params {
+            syn::parse_quote! { #self<#(#params),*> }
+        } else {
+            self
+        }
+    }
+}
+
+trait CodeGenerator {
+    /// Extra information from the caller.
+    type Extra;
+
+    /// Extra information returned to the caller.
+    type Return;
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        extra: &Self::Extra,
+    ) -> Self::Return;
+}
+
+impl Item {
+    fn process_before_codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult,
+    ) -> bool {
+        if !self.is_enabled_for_codegen(ctx) {
+            return false;
+        }
+
+        if self.is_blocklisted(ctx) || result.seen(self.id()) {
+            debug!(
+                "<Item as CodeGenerator>::process_before_codegen: Ignoring hidden or seen: \
+                 self = {:?}",
+                self
+            );
+            return false;
+        }
+
+        if !ctx.codegen_items().contains(&self.id()) {
+            // TODO(emilio, #453): Figure out what to do when this happens
+            // legitimately, we could track the opaque stuff and disable the
+            // assertion there I guess.
+            warn!("Found non-allowlisted item in code generation: {:?}", self);
+        }
+
+        result.set_seen(self.id());
+        true
+    }
+}
+
+impl CodeGenerator for Item {
+    type Extra = ();
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        _extra: &(),
+    ) {
+        debug!("<Item as CodeGenerator>::codegen: self = {:?}", self);
+        if !self.process_before_codegen(ctx, result) {
+            return;
+        }
+
+        match *self.kind() {
+            ItemKind::Module(ref module) => {
+                module.codegen(ctx, result, self);
+            }
+            ItemKind::Function(ref fun) => {
+                fun.codegen(ctx, result, self);
+            }
+            ItemKind::Var(ref var) => {
+                var.codegen(ctx, result, self);
+            }
+            ItemKind::Type(ref ty) => {
+                ty.codegen(ctx, result, self);
+            }
+        }
+    }
+}
+
+impl CodeGenerator for Module {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        debug!("<Module as CodeGenerator>::codegen: item = {:?}", item);
+
+        let codegen_self = |result: &mut CodegenResult,
+                            found_any: &mut bool| {
+            for child in self.children() {
+                if ctx.codegen_items().contains(child) {
+                    *found_any = true;
+                    ctx.resolve_item(*child).codegen(ctx, result, &());
+                }
+            }
+
+            if item.id() == ctx.root_module() {
+                if result.saw_block {
+                    utils::prepend_block_header(ctx, &mut *result);
+                }
+                if result.saw_bindgen_union {
+                    utils::prepend_union_types(ctx, &mut *result);
+                }
+                if result.saw_incomplete_array {
+                    utils::prepend_incomplete_array_types(ctx, &mut *result);
+                }
+                if ctx.need_bindgen_float16_type() {
+                    utils::prepend_float16_type(&mut *result);
+                }
+                if ctx.need_bindgen_complex_type() {
+                    utils::prepend_complex_type(&mut *result);
+                }
+                if result.saw_objc {
+                    utils::prepend_objc_header(ctx, &mut *result);
+                }
+                if result.saw_bitfield_unit {
+                    utils::prepend_bitfield_unit_type(ctx, &mut *result);
+                }
+            }
+        };
+
+        if !ctx.options().enable_cxx_namespaces ||
+            (self.is_inline() &&
+                !ctx.options().conservative_inline_namespaces)
+        {
+            codegen_self(result, &mut false);
+            return;
+        }
+
+        let mut found_any = false;
+        let inner_items = result.inner(|result| {
+            result.push(root_import(ctx, item));
+
+            let path = item
+                .namespace_aware_canonical_path(ctx)
+                .join("::")
+                .into_boxed_str();
+            if let Some(raw_lines) = ctx.options().module_lines.get(&path) {
+                for raw_line in raw_lines {
+                    found_any = true;
+                    result.push(
+                        proc_macro2::TokenStream::from_str(raw_line).unwrap(),
+                    );
+                }
+            }
+
+            codegen_self(result, &mut found_any);
+        });
+
+        // Don't bother creating an empty module.
+        if !found_any {
+            return;
+        }
+
+        let name = item.canonical_name(ctx);
+        let ident = ctx.rust_ident(name);
+        result.push(if item.id() == ctx.root_module() {
+            quote! {
+                #[allow(non_snake_case, non_camel_case_types, non_upper_case_globals)]
+                pub mod #ident {
+                    #( #inner_items )*
+                }
+            }
+        } else {
+            quote! {
+                pub mod #ident {
+                    #( #inner_items )*
+                }
+            }
+        });
+    }
+}
+
+impl CodeGenerator for Var {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        use crate::ir::var::VarType;
+        debug!("<Var as CodeGenerator>::codegen: item = {:?}", item);
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+
+        let canonical_name = item.canonical_name(ctx);
+
+        if result.seen_var(&canonical_name) {
+            return;
+        }
+        result.saw_var(&canonical_name);
+
+        let canonical_ident = ctx.rust_ident(&canonical_name);
+
+        // We can't generate bindings to static variables of templates. The
+        // number of actual variables for a single declaration are open ended
+        // and we don't know what instantiations do or don't exist.
+        if !item.all_template_params(ctx).is_empty() {
+            return;
+        }
+
+        let mut attrs = vec![];
+        if let Some(comment) = item.comment(ctx) {
+            attrs.push(attributes::doc(comment));
+        }
+
+        let var_ty = self.ty();
+        let ty = var_ty.to_rust_ty_or_opaque(ctx, &());
+
+        if let Some(val) = self.val() {
+            match *val {
+                VarType::Bool(val) => {
+                    result.push(quote! {
+                        #(#attrs)*
+                        pub const #canonical_ident : #ty = #val ;
+                    });
+                }
+                VarType::Int(val) => {
+                    let int_kind = var_ty
+                        .into_resolver()
+                        .through_type_aliases()
+                        .through_type_refs()
+                        .resolve(ctx)
+                        .expect_type()
+                        .as_integer()
+                        .unwrap();
+                    let val = if int_kind.is_signed() {
+                        helpers::ast_ty::int_expr(val)
+                    } else {
+                        helpers::ast_ty::uint_expr(val as _)
+                    };
+                    result.push(quote! {
+                        #(#attrs)*
+                        pub const #canonical_ident : #ty = #val ;
+                    });
+                }
+                VarType::String(ref bytes) => {
+                    let prefix = ctx.trait_prefix();
+
+                    let options = ctx.options();
+                    let rust_features = options.rust_features;
+
+                    let mut cstr_bytes = bytes.clone();
+                    cstr_bytes.push(0);
+                    let len = proc_macro2::Literal::usize_unsuffixed(
+                        cstr_bytes.len(),
+                    );
+
+                    // TODO: Here we ignore the type we just made up, probably
+                    // we should refactor how the variable type and ty ID work.
+                    let array_ty = quote! { [u8; #len] };
+                    let cstr_ty = quote! { ::#prefix::ffi::CStr };
+
+                    let bytes = proc_macro2::Literal::byte_string(&cstr_bytes);
+
+                    if options.generate_cstr &&
+                        rust_features.const_cstr &&
+                        CStr::from_bytes_with_nul(&cstr_bytes).is_ok()
+                    {
+                        result.push(quote! {
+                            #(#attrs)*
+                            #[allow(unsafe_code)]
+                            pub const #canonical_ident: &#cstr_ty = unsafe {
+                                #cstr_ty::from_bytes_with_nul_unchecked(#bytes)
+                            };
+                        });
+                    } else {
+                        let lifetime = if rust_features.static_lifetime_elision
+                        {
+                            None
+                        } else {
+                            Some(quote! { 'static })
+                        }
+                        .into_iter();
+
+                        result.push(quote! {
+                            #(#attrs)*
+                            pub const #canonical_ident: &#(#lifetime )*#array_ty = #bytes ;
+                        });
+                    }
+                }
+                VarType::Float(f) => {
+                    if let Ok(expr) = helpers::ast_ty::float_expr(ctx, f) {
+                        result.push(quote! {
+                            #(#attrs)*
+                            pub const #canonical_ident : #ty = #expr ;
+                        });
+                    }
+                }
+                VarType::Char(c) => {
+                    result.push(quote! {
+                        #(#attrs)*
+                        pub const #canonical_ident : #ty = #c ;
+                    });
+                }
+            }
+        } else {
+            // If necessary, apply a `#[link_name]` attribute
+            if let Some(link_name) = self.link_name() {
+                attrs.push(attributes::link_name::<false>(link_name));
+            } else {
+                let link_name =
+                    self.mangled_name().unwrap_or_else(|| self.name());
+                if !utils::names_will_be_identical_after_mangling(
+                    &canonical_name,
+                    link_name,
+                    None,
+                ) {
+                    attrs.push(attributes::link_name::<false>(link_name));
+                }
+            }
+
+            let maybe_mut = if self.is_const() {
+                quote! {}
+            } else {
+                quote! { mut }
+            };
+
+            let tokens = quote!(
+                extern "C" {
+                    #(#attrs)*
+                    pub static #maybe_mut #canonical_ident: #ty;
+                }
+            );
+
+            result.push(tokens);
+        }
+    }
+}
+
+impl CodeGenerator for Type {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        debug!("<Type as CodeGenerator>::codegen: item = {:?}", item);
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+
+        match *self.kind() {
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Int(..) |
+            TypeKind::Float(..) |
+            TypeKind::Complex(..) |
+            TypeKind::Array(..) |
+            TypeKind::Vector(..) |
+            TypeKind::Pointer(..) |
+            TypeKind::Reference(..) |
+            TypeKind::Function(..) |
+            TypeKind::ResolvedTypeRef(..) |
+            TypeKind::Opaque |
+            TypeKind::TypeParam => {
+                // These items don't need code generation, they only need to be
+                // converted to rust types in fields, arguments, and such.
+                // NOTE(emilio): If you add to this list, make sure to also add
+                // it to BindgenContext::compute_allowlisted_and_codegen_items.
+            }
+            TypeKind::TemplateInstantiation(ref inst) => {
+                inst.codegen(ctx, result, item)
+            }
+            TypeKind::BlockPointer(inner) => {
+                if !ctx.options().generate_block {
+                    return;
+                }
+
+                let inner_item =
+                    inner.into_resolver().through_type_refs().resolve(ctx);
+                let name = item.canonical_name(ctx);
+
+                let inner_rust_type = {
+                    if let TypeKind::Function(fnsig) =
+                        inner_item.kind().expect_type().kind()
+                    {
+                        utils::fnsig_block(ctx, fnsig)
+                    } else {
+                        panic!("invalid block typedef: {:?}", inner_item)
+                    }
+                };
+
+                let rust_name = ctx.rust_ident(name);
+
+                let mut tokens = if let Some(comment) = item.comment(ctx) {
+                    attributes::doc(comment)
+                } else {
+                    quote! {}
+                };
+
+                tokens.append_all(quote! {
+                    pub type #rust_name = #inner_rust_type ;
+                });
+
+                result.push(tokens);
+                result.saw_block();
+            }
+            TypeKind::Comp(ref ci) => ci.codegen(ctx, result, item),
+            TypeKind::TemplateAlias(inner, _) | TypeKind::Alias(inner) => {
+                let inner_item =
+                    inner.into_resolver().through_type_refs().resolve(ctx);
+                let name = item.canonical_name(ctx);
+                let path = item.canonical_path(ctx);
+
+                {
+                    let through_type_aliases = inner
+                        .into_resolver()
+                        .through_type_refs()
+                        .through_type_aliases()
+                        .resolve(ctx);
+
+                    // Try to catch the common pattern:
+                    //
+                    // typedef struct foo { ... } foo;
+                    //
+                    // here, and also other more complex cases like #946.
+                    if through_type_aliases.canonical_path(ctx) == path {
+                        return;
+                    }
+                }
+
+                // If this is a known named type, disallow generating anything
+                // for it too. If size_t -> usize conversions are enabled, we
+                // need to check that these conversions are permissible, but
+                // nothing needs to be generated, still.
+                let spelling = self.name().expect("Unnamed alias?");
+                if utils::type_from_named(ctx, spelling).is_some() {
+                    if let "size_t" | "ssize_t" = spelling {
+                        let layout = inner_item
+                            .kind()
+                            .expect_type()
+                            .layout(ctx)
+                            .expect("No layout?");
+                        assert_eq!(
+                            layout.size,
+                            ctx.target_pointer_size(),
+                            "Target platform requires `--no-size_t-is-usize`. The size of `{}` ({}) does not match the target pointer size ({})",
+                            spelling,
+                            layout.size,
+                            ctx.target_pointer_size(),
+                            );
+                        assert_eq!(
+                            layout.align,
+                            ctx.target_pointer_size(),
+                            "Target platform requires `--no-size_t-is-usize`. The alignment of `{}` ({}) does not match the target pointer size ({})",
+                            spelling,
+                            layout.align,
+                            ctx.target_pointer_size(),
+                        );
+                    }
+                    return;
+                }
+
+                let mut outer_params = item.used_template_params(ctx);
+
+                let is_opaque = item.is_opaque(ctx, &());
+                let inner_rust_type = if is_opaque {
+                    outer_params = vec![];
+                    self.to_opaque(ctx, item)
+                } else {
+                    // Its possible that we have better layout information than
+                    // the inner type does, so fall back to an opaque blob based
+                    // on our layout if converting the inner item fails.
+                    inner_item
+                        .try_to_rust_ty_or_opaque(ctx, &())
+                        .unwrap_or_else(|_| self.to_opaque(ctx, item))
+                        .with_implicit_template_params(ctx, inner_item)
+                };
+
+                {
+                    // FIXME(emilio): This is a workaround to avoid generating
+                    // incorrect type aliases because of types that we haven't
+                    // been able to resolve (because, eg, they depend on a
+                    // template parameter).
+                    //
+                    // It's kind of a shame not generating them even when they
+                    // could be referenced, but we already do the same for items
+                    // with invalid template parameters, and at least this way
+                    // they can be replaced, instead of generating plain invalid
+                    // code.
+                    let inner_canon_type =
+                        inner_item.expect_type().canonical_type(ctx);
+                    if inner_canon_type.is_invalid_type_param() {
+                        warn!(
+                            "Item contained invalid named type, skipping: \
+                             {:?}, {:?}",
+                            item, inner_item
+                        );
+                        return;
+                    }
+                }
+
+                let rust_name = ctx.rust_ident(&name);
+
+                let mut tokens = if let Some(comment) = item.comment(ctx) {
+                    attributes::doc(comment)
+                } else {
+                    quote! {}
+                };
+
+                let alias_style = if ctx.options().type_alias.matches(&name) {
+                    AliasVariation::TypeAlias
+                } else if ctx.options().new_type_alias.matches(&name) {
+                    AliasVariation::NewType
+                } else if ctx.options().new_type_alias_deref.matches(&name) {
+                    AliasVariation::NewTypeDeref
+                } else {
+                    ctx.options().default_alias_style
+                };
+
+                // We prefer using `pub use` over `pub type` because of:
+                // https://github.com/rust-lang/rust/issues/26264
+                if matches!(inner_rust_type, syn::Type::Path(_)) &&
+                    outer_params.is_empty() &&
+                    !is_opaque &&
+                    alias_style == AliasVariation::TypeAlias &&
+                    inner_item.expect_type().canonical_type(ctx).is_enum()
+                {
+                    tokens.append_all(quote! {
+                        pub use
+                    });
+                    let path = top_level_path(ctx, item);
+                    tokens.append_separated(path, quote!(::));
+                    tokens.append_all(quote! {
+                        :: #inner_rust_type  as #rust_name ;
+                    });
+                    result.push(tokens);
+                    return;
+                }
+
+                tokens.append_all(match alias_style {
+                    AliasVariation::TypeAlias => quote! {
+                        pub type #rust_name
+                    },
+                    AliasVariation::NewType | AliasVariation::NewTypeDeref => {
+                        assert!(
+                            ctx.options().rust_features().repr_transparent,
+                            "repr_transparent feature is required to use {:?}",
+                            alias_style
+                        );
+
+                        let mut attributes =
+                            vec![attributes::repr("transparent")];
+                        let packed = false; // Types can't be packed in Rust.
+                        let derivable_traits =
+                            derives_of_item(item, ctx, packed);
+                        if !derivable_traits.is_empty() {
+                            let derives: Vec<_> = derivable_traits.into();
+                            attributes.push(attributes::derives(&derives))
+                        }
+
+                        quote! {
+                            #( #attributes )*
+                            pub struct #rust_name
+                        }
+                    }
+                });
+
+                let params: Vec<_> = outer_params
+                    .into_iter()
+                    .filter_map(|p| p.as_template_param(ctx, &()))
+                    .collect();
+                if params
+                    .iter()
+                    .any(|p| ctx.resolve_type(*p).is_invalid_type_param())
+                {
+                    warn!(
+                        "Item contained invalid template \
+                         parameter: {:?}",
+                        item
+                    );
+                    return;
+                }
+                let params: Vec<_> = params
+                    .iter()
+                    .map(|p| {
+                        p.try_to_rust_ty(ctx, &()).expect(
+                            "type parameters can always convert to rust ty OK",
+                        )
+                    })
+                    .collect();
+
+                if !params.is_empty() {
+                    tokens.append_all(quote! {
+                        < #( #params ),* >
+                    });
+                }
+
+                let access_spec =
+                    access_specifier(ctx.options().default_visibility);
+                tokens.append_all(match alias_style {
+                    AliasVariation::TypeAlias => quote! {
+                        = #inner_rust_type ;
+                    },
+                    AliasVariation::NewType | AliasVariation::NewTypeDeref => {
+                        quote! {
+                            (#access_spec #inner_rust_type) ;
+                        }
+                    }
+                });
+
+                if alias_style == AliasVariation::NewTypeDeref {
+                    let prefix = ctx.trait_prefix();
+                    tokens.append_all(quote! {
+                        impl ::#prefix::ops::Deref for #rust_name {
+                            type Target = #inner_rust_type;
+                            #[inline]
+                            fn deref(&self) -> &Self::Target {
+                                &self.0
+                            }
+                        }
+                        impl ::#prefix::ops::DerefMut for #rust_name {
+                            #[inline]
+                            fn deref_mut(&mut self) -> &mut Self::Target {
+                                &mut self.0
+                            }
+                        }
+                    });
+                }
+
+                result.push(tokens);
+            }
+            TypeKind::Enum(ref ei) => ei.codegen(ctx, result, item),
+            TypeKind::ObjCId | TypeKind::ObjCSel => {
+                result.saw_objc();
+            }
+            TypeKind::ObjCInterface(ref interface) => {
+                interface.codegen(ctx, result, item)
+            }
+            ref u @ TypeKind::UnresolvedTypeRef(..) => {
+                unreachable!("Should have been resolved after parsing {:?}!", u)
+            }
+        }
+    }
+}
+
+struct Vtable<'a> {
+    item_id: ItemId,
+    /// A reference to the originating compound object.
+    #[allow(dead_code)]
+    comp_info: &'a CompInfo,
+}
+
+impl<'a> Vtable<'a> {
+    fn new(item_id: ItemId, comp_info: &'a CompInfo) -> Self {
+        Vtable { item_id, comp_info }
+    }
+}
+
+impl<'a> CodeGenerator for Vtable<'a> {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        assert_eq!(item.id(), self.item_id);
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+        let name = ctx.rust_ident(self.canonical_name(ctx));
+
+        // For now, we will only generate vtables for classes that:
+        // - do not inherit from others (compilers merge VTable from primary parent class).
+        // - do not contain a virtual destructor (requires ordering; platforms generate different vtables).
+        if ctx.options().vtable_generation &&
+            self.comp_info.base_members().is_empty() &&
+            self.comp_info.destructor().is_none()
+        {
+            let class_ident = ctx.rust_ident(self.item_id.canonical_name(ctx));
+
+            let methods = self
+                .comp_info
+                .methods()
+                .iter()
+                .filter_map(|m| {
+                    if !m.is_virtual() {
+                        return None;
+                    }
+
+                    let function_item = ctx.resolve_item(m.signature());
+                    let function = function_item.expect_function();
+                    let signature_item = ctx.resolve_item(function.signature());
+                    let signature = match signature_item.expect_type().kind() {
+                        TypeKind::Function(ref sig) => sig,
+                        _ => panic!("Function signature type mismatch"),
+                    };
+
+                    // FIXME: Is there a canonical name without the class prepended?
+                    let function_name = function_item.canonical_name(ctx);
+
+                    // FIXME: Need to account for overloading with times_seen (separately from regular function path).
+                    let function_name = ctx.rust_ident(function_name);
+                    let mut args = utils::fnsig_arguments(ctx, signature);
+                    let ret = utils::fnsig_return_ty(ctx, signature);
+
+                    args[0] = if m.is_const() {
+                        quote! { this: *const #class_ident }
+                    } else {
+                        quote! { this: *mut #class_ident }
+                    };
+
+                    Some(quote! {
+                        pub #function_name : unsafe extern "C" fn( #( #args ),* ) #ret
+                    })
+                })
+                .collect::<Vec<_>>();
+
+            result.push(quote! {
+                #[repr(C)]
+                pub struct #name {
+                    #( #methods ),*
+                }
+            })
+        } else {
+            // For the cases we don't support, simply generate an empty struct.
+            let void = helpers::ast_ty::c_void(ctx);
+
+            result.push(quote! {
+                #[repr(C)]
+                pub struct #name ( #void );
+            });
+        }
+    }
+}
+
+impl<'a> ItemCanonicalName for Vtable<'a> {
+    fn canonical_name(&self, ctx: &BindgenContext) -> String {
+        format!("{}__bindgen_vtable", self.item_id.canonical_name(ctx))
+    }
+}
+
+impl<'a> TryToRustTy for Vtable<'a> {
+    type Extra = ();
+
+    fn try_to_rust_ty(
+        &self,
+        ctx: &BindgenContext,
+        _: &(),
+    ) -> error::Result<syn::Type> {
+        let name = ctx.rust_ident(self.canonical_name(ctx));
+        Ok(syn::parse_quote! { #name })
+    }
+}
+
+impl CodeGenerator for TemplateInstantiation {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+
+        // Although uses of instantiations don't need code generation, and are
+        // just converted to rust types in fields, vars, etc, we take this
+        // opportunity to generate tests for their layout here. If the
+        // instantiation is opaque, then its presumably because we don't
+        // properly understand it (maybe because of specializations), and so we
+        // shouldn't emit layout tests either.
+        if !ctx.options().layout_tests || self.is_opaque(ctx, item) {
+            return;
+        }
+
+        // If there are any unbound type parameters, then we can't generate a
+        // layout test because we aren't dealing with a concrete type with a
+        // concrete size and alignment.
+        if ctx.uses_any_template_parameters(item.id()) {
+            return;
+        }
+
+        let layout = item.kind().expect_type().layout(ctx);
+
+        if let Some(layout) = layout {
+            let size = layout.size;
+            let align = layout.align;
+
+            let name = item.full_disambiguated_name(ctx);
+            let mut fn_name =
+                format!("__bindgen_test_layout_{}_instantiation", name);
+            let times_seen = result.overload_number(&fn_name);
+            if times_seen > 0 {
+                write!(&mut fn_name, "_{}", times_seen).unwrap();
+            }
+
+            let fn_name = ctx.rust_ident_raw(fn_name);
+
+            let prefix = ctx.trait_prefix();
+            let ident = item.to_rust_ty_or_opaque(ctx, &());
+            let size_of_expr = quote! {
+                ::#prefix::mem::size_of::<#ident>()
+            };
+            let align_of_expr = quote! {
+                ::#prefix::mem::align_of::<#ident>()
+            };
+
+            let item = quote! {
+                #[test]
+                fn #fn_name() {
+                    assert_eq!(#size_of_expr, #size,
+                               concat!("Size of template specialization: ",
+                                       stringify!(#ident)));
+                    assert_eq!(#align_of_expr, #align,
+                               concat!("Alignment of template specialization: ",
+                                       stringify!(#ident)));
+                }
+            };
+
+            result.push(item);
+        }
+    }
+}
+
+/// Trait for implementing the code generation of a struct or union field.
+trait FieldCodegen<'a> {
+    type Extra;
+
+    #[allow(clippy::too_many_arguments)]
+    fn codegen<F, M>(
+        &self,
+        ctx: &BindgenContext,
+        visibility_kind: FieldVisibilityKind,
+        accessor_kind: FieldAccessorKind,
+        parent: &CompInfo,
+        parent_item: &Item,
+        result: &mut CodegenResult,
+        struct_layout: &mut StructLayoutTracker,
+        fields: &mut F,
+        methods: &mut M,
+        extra: Self::Extra,
+    ) where
+        F: Extend<proc_macro2::TokenStream>,
+        M: Extend<proc_macro2::TokenStream>;
+}
+
+impl<'a> FieldCodegen<'a> for Field {
+    type Extra = ();
+
+    fn codegen<F, M>(
+        &self,
+        ctx: &BindgenContext,
+        visibility_kind: FieldVisibilityKind,
+        accessor_kind: FieldAccessorKind,
+        parent: &CompInfo,
+        parent_item: &Item,
+        result: &mut CodegenResult,
+        struct_layout: &mut StructLayoutTracker,
+        fields: &mut F,
+        methods: &mut M,
+        _: (),
+    ) where
+        F: Extend<proc_macro2::TokenStream>,
+        M: Extend<proc_macro2::TokenStream>,
+    {
+        match *self {
+            Field::DataMember(ref data) => {
+                data.codegen(
+                    ctx,
+                    visibility_kind,
+                    accessor_kind,
+                    parent,
+                    parent_item,
+                    result,
+                    struct_layout,
+                    fields,
+                    methods,
+                    (),
+                );
+            }
+            Field::Bitfields(ref unit) => {
+                unit.codegen(
+                    ctx,
+                    visibility_kind,
+                    accessor_kind,
+                    parent,
+                    parent_item,
+                    result,
+                    struct_layout,
+                    fields,
+                    methods,
+                    (),
+                );
+            }
+        }
+    }
+}
+
+fn wrap_union_field_if_needed(
+    ctx: &BindgenContext,
+    struct_layout: &StructLayoutTracker,
+    ty: syn::Type,
+    result: &mut CodegenResult,
+) -> syn::Type {
+    if struct_layout.is_rust_union() {
+        if struct_layout.can_copy_union_fields() {
+            ty
+        } else {
+            let prefix = ctx.trait_prefix();
+            syn::parse_quote! { ::#prefix::mem::ManuallyDrop<#ty> }
+        }
+    } else {
+        result.saw_bindgen_union();
+        if ctx.options().enable_cxx_namespaces {
+            syn::parse_quote! { root::__BindgenUnionField<#ty> }
+        } else {
+            syn::parse_quote! { __BindgenUnionField<#ty> }
+        }
+    }
+}
+
+impl<'a> FieldCodegen<'a> for FieldData {
+    type Extra = ();
+
+    fn codegen<F, M>(
+        &self,
+        ctx: &BindgenContext,
+        parent_visibility_kind: FieldVisibilityKind,
+        accessor_kind: FieldAccessorKind,
+        parent: &CompInfo,
+        parent_item: &Item,
+        result: &mut CodegenResult,
+        struct_layout: &mut StructLayoutTracker,
+        fields: &mut F,
+        methods: &mut M,
+        _: (),
+    ) where
+        F: Extend<proc_macro2::TokenStream>,
+        M: Extend<proc_macro2::TokenStream>,
+    {
+        // Bitfields are handled by `FieldCodegen` implementations for
+        // `BitfieldUnit` and `Bitfield`.
+        assert!(self.bitfield_width().is_none());
+
+        let field_item =
+            self.ty().into_resolver().through_type_refs().resolve(ctx);
+        let field_ty = field_item.expect_type();
+        let ty = self
+            .ty()
+            .to_rust_ty_or_opaque(ctx, &())
+            .with_implicit_template_params(ctx, field_item);
+
+        // NB: If supported, we use proper `union` types.
+        let ty = if parent.is_union() {
+            wrap_union_field_if_needed(ctx, struct_layout, ty, result)
+        } else if let Some(item) = field_ty.is_incomplete_array(ctx) {
+            result.saw_incomplete_array();
+
+            let inner = item.to_rust_ty_or_opaque(ctx, &());
+
+            if ctx.options().enable_cxx_namespaces {
+                syn::parse_quote! { root::__IncompleteArrayField<#inner> }
+            } else {
+                syn::parse_quote! { __IncompleteArrayField<#inner> }
+            }
+        } else {
+            ty
+        };
+
+        let mut field = quote! {};
+        if ctx.options().generate_comments {
+            if let Some(raw_comment) = self.comment() {
+                let comment = ctx.options().process_comment(raw_comment);
+                field = attributes::doc(comment);
+            }
+        }
+
+        let field_name = self
+            .name()
+            .map(|name| ctx.rust_mangle(name).into_owned())
+            .expect("Each field should have a name in codegen!");
+        let field_name = field_name.as_str();
+        let field_ident = ctx.rust_ident_raw(field_name);
+
+        if let Some(padding_field) =
+            struct_layout.saw_field(field_name, field_ty, self.offset())
+        {
+            fields.extend(Some(padding_field));
+        }
+
+        let visibility = compute_visibility(
+            ctx,
+            self.is_public(),
+            ctx.options().last_callback(|cb| {
+                cb.field_visibility(FieldInfo {
+                    type_name: &parent_item.canonical_name(ctx),
+                    field_name,
+                })
+            }),
+            self.annotations(),
+            parent_visibility_kind,
+        );
+        let accessor_kind =
+            self.annotations().accessor_kind().unwrap_or(accessor_kind);
+
+        match visibility {
+            FieldVisibilityKind::Private => {
+                field.append_all(quote! {
+                    #field_ident : #ty ,
+                });
+            }
+            FieldVisibilityKind::PublicCrate => {
+                field.append_all(quote! {
+                    pub(crate) #field_ident : #ty ,
+                });
+            }
+            FieldVisibilityKind::Public => {
+                field.append_all(quote! {
+                    pub #field_ident : #ty ,
+                });
+            }
+        }
+
+        fields.extend(Some(field));
+
+        // TODO: Factor the following code out, please!
+        if accessor_kind == FieldAccessorKind::None {
+            return;
+        }
+
+        let getter_name = ctx.rust_ident_raw(format!("get_{}", field_name));
+        let mutable_getter_name =
+            ctx.rust_ident_raw(format!("get_{}_mut", field_name));
+
+        methods.extend(Some(match accessor_kind {
+            FieldAccessorKind::None => unreachable!(),
+            FieldAccessorKind::Regular => {
+                quote! {
+                    #[inline]
+                    pub fn #getter_name(&self) -> & #ty {
+                        &self.#field_ident
+                    }
+
+                    #[inline]
+                    pub fn #mutable_getter_name(&mut self) -> &mut #ty {
+                        &mut self.#field_ident
+                    }
+                }
+            }
+            FieldAccessorKind::Unsafe => {
+                quote! {
+                    #[inline]
+                    pub unsafe fn #getter_name(&self) -> & #ty {
+                        &self.#field_ident
+                    }
+
+                    #[inline]
+                    pub unsafe fn #mutable_getter_name(&mut self) -> &mut #ty {
+                        &mut self.#field_ident
+                    }
+                }
+            }
+            FieldAccessorKind::Immutable => {
+                quote! {
+                    #[inline]
+                    pub fn #getter_name(&self) -> & #ty {
+                        &self.#field_ident
+                    }
+                }
+            }
+        }));
+    }
+}
+
+impl BitfieldUnit {
+    /// Get the constructor name for this bitfield unit.
+    fn ctor_name(&self) -> proc_macro2::TokenStream {
+        let ctor_name = Ident::new(
+            &format!("new_bitfield_{}", self.nth()),
+            Span::call_site(),
+        );
+        quote! {
+            #ctor_name
+        }
+    }
+}
+
+impl Bitfield {
+    /// Extend an under construction bitfield unit constructor with this
+    /// bitfield. This sets the relevant bits on the `__bindgen_bitfield_unit`
+    /// variable that's being constructed.
+    fn extend_ctor_impl(
+        &self,
+        ctx: &BindgenContext,
+        param_name: proc_macro2::TokenStream,
+        mut ctor_impl: proc_macro2::TokenStream,
+    ) -> proc_macro2::TokenStream {
+        let bitfield_ty = ctx.resolve_type(self.ty());
+        let bitfield_ty_layout = bitfield_ty
+            .layout(ctx)
+            .expect("Bitfield without layout? Gah!");
+        let bitfield_int_ty = helpers::integer_type(ctx, bitfield_ty_layout)
+            .expect(
+                "Should already have verified that the bitfield is \
+                 representable as an int",
+            );
+
+        let offset = self.offset_into_unit();
+        let width = self.width() as u8;
+        let prefix = ctx.trait_prefix();
+
+        ctor_impl.append_all(quote! {
+            __bindgen_bitfield_unit.set(
+                #offset,
+                #width,
+                {
+                    let #param_name: #bitfield_int_ty = unsafe {
+                        ::#prefix::mem::transmute(#param_name)
+                    };
+                    #param_name as u64
+                }
+            );
+        });
+
+        ctor_impl
+    }
+}
+
+fn access_specifier(
+    visibility: FieldVisibilityKind,
+) -> proc_macro2::TokenStream {
+    match visibility {
+        FieldVisibilityKind::Private => quote! {},
+        FieldVisibilityKind::PublicCrate => quote! { pub(crate) },
+        FieldVisibilityKind::Public => quote! { pub },
+    }
+}
+
+/// Compute a fields or structs visibility based on multiple conditions.
+/// 1. If the element was declared public, and we respect such CXX accesses specs
+/// (context option) => By default Public, but this can be overruled by an `annotation`.
+///
+/// 2. If the element was declared private, and we respect such CXX accesses specs
+/// (context option) => By default Private, but this can be overruled by an `annotation`.
+///
+/// 3. If we do not respect visibility modifiers, the result depends on the `annotation`,
+/// if any, or the passed `default_kind`.
+///
+fn compute_visibility(
+    ctx: &BindgenContext,
+    is_declared_public: bool,
+    callback_override: Option<FieldVisibilityKind>,
+    annotations: &Annotations,
+    default_kind: FieldVisibilityKind,
+) -> FieldVisibilityKind {
+    callback_override
+        .or_else(|| annotations.visibility_kind())
+        .unwrap_or_else(|| {
+            match (is_declared_public, ctx.options().respect_cxx_access_specs) {
+                (true, true) => {
+                    // declared as public, cxx specs are respected
+                    FieldVisibilityKind::Public
+                }
+                (false, true) => {
+                    // declared as private, cxx specs are respected
+                    FieldVisibilityKind::Private
+                }
+                (_, false) => {
+                    // cxx specs are not respected, declaration does not matter.
+                    default_kind
+                }
+            }
+        })
+}
+
+impl<'a> FieldCodegen<'a> for BitfieldUnit {
+    type Extra = ();
+
+    fn codegen<F, M>(
+        &self,
+        ctx: &BindgenContext,
+        visibility_kind: FieldVisibilityKind,
+        accessor_kind: FieldAccessorKind,
+        parent: &CompInfo,
+        parent_item: &Item,
+        result: &mut CodegenResult,
+        struct_layout: &mut StructLayoutTracker,
+        fields: &mut F,
+        methods: &mut M,
+        _: (),
+    ) where
+        F: Extend<proc_macro2::TokenStream>,
+        M: Extend<proc_macro2::TokenStream>,
+    {
+        use crate::ir::ty::RUST_DERIVE_IN_ARRAY_LIMIT;
+
+        result.saw_bitfield_unit();
+
+        let layout = self.layout();
+        let unit_field_ty = helpers::bitfield_unit(ctx, layout);
+        let field_ty = {
+            let unit_field_ty = unit_field_ty.clone();
+            if parent.is_union() {
+                wrap_union_field_if_needed(
+                    ctx,
+                    struct_layout,
+                    unit_field_ty,
+                    result,
+                )
+            } else {
+                unit_field_ty
+            }
+        };
+
+        {
+            let align_field_name = format!("_bitfield_align_{}", self.nth());
+            let align_field_ident = ctx.rust_ident(align_field_name);
+            let align_ty = match self.layout().align {
+                n if n >= 8 => quote! { u64 },
+                4 => quote! { u32 },
+                2 => quote! { u16 },
+                _ => quote! { u8  },
+            };
+            let access_spec = access_specifier(visibility_kind);
+            let align_field = quote! {
+                #access_spec #align_field_ident: [#align_ty; 0],
+            };
+            fields.extend(Some(align_field));
+        }
+
+        let unit_field_name = format!("_bitfield_{}", self.nth());
+        let unit_field_ident = ctx.rust_ident(&unit_field_name);
+
+        let ctor_name = self.ctor_name();
+        let mut ctor_params = vec![];
+        let mut ctor_impl = quote! {};
+
+        // We cannot generate any constructor if the underlying storage can't
+        // implement AsRef<[u8]> / AsMut<[u8]> / etc, or can't derive Default.
+        //
+        // We don't check `larger_arrays` here because Default does still have
+        // the 32 items limitation.
+        let mut generate_ctor = layout.size <= RUST_DERIVE_IN_ARRAY_LIMIT;
+
+        let mut unit_visibility = visibility_kind;
+        for bf in self.bitfields() {
+            // Codegen not allowed for anonymous bitfields
+            if bf.name().is_none() {
+                continue;
+            }
+
+            if layout.size > RUST_DERIVE_IN_ARRAY_LIMIT &&
+                !ctx.options().rust_features().larger_arrays
+            {
+                continue;
+            }
+
+            let mut bitfield_representable_as_int = true;
+            let mut bitfield_visibility = visibility_kind;
+            bf.codegen(
+                ctx,
+                visibility_kind,
+                accessor_kind,
+                parent,
+                parent_item,
+                result,
+                struct_layout,
+                fields,
+                methods,
+                (
+                    &unit_field_name,
+                    &mut bitfield_representable_as_int,
+                    &mut bitfield_visibility,
+                ),
+            );
+            if bitfield_visibility < unit_visibility {
+                unit_visibility = bitfield_visibility;
+            }
+
+            // Generating a constructor requires the bitfield to be representable as an integer.
+            if !bitfield_representable_as_int {
+                generate_ctor = false;
+                continue;
+            }
+
+            let param_name = bitfield_getter_name(ctx, bf);
+            let bitfield_ty_item = ctx.resolve_item(bf.ty());
+            let bitfield_ty = bitfield_ty_item.expect_type();
+            let bitfield_ty =
+                bitfield_ty.to_rust_ty_or_opaque(ctx, bitfield_ty_item);
+
+            ctor_params.push(quote! {
+                #param_name : #bitfield_ty
+            });
+            ctor_impl = bf.extend_ctor_impl(ctx, param_name, ctor_impl);
+        }
+
+        let access_spec = access_specifier(unit_visibility);
+
+        let field = quote! {
+            #access_spec #unit_field_ident : #field_ty ,
+        };
+        fields.extend(Some(field));
+
+        if generate_ctor {
+            methods.extend(Some(quote! {
+                #[inline]
+                #access_spec fn #ctor_name ( #( #ctor_params ),* ) -> #unit_field_ty {
+                    let mut __bindgen_bitfield_unit: #unit_field_ty = Default::default();
+                    #ctor_impl
+                    __bindgen_bitfield_unit
+                }
+            }));
+        }
+
+        struct_layout.saw_bitfield_unit(layout);
+    }
+}
+
+fn bitfield_getter_name(
+    ctx: &BindgenContext,
+    bitfield: &Bitfield,
+) -> proc_macro2::TokenStream {
+    let name = bitfield.getter_name();
+    let name = ctx.rust_ident_raw(name);
+    quote! { #name }
+}
+
+fn bitfield_setter_name(
+    ctx: &BindgenContext,
+    bitfield: &Bitfield,
+) -> proc_macro2::TokenStream {
+    let setter = bitfield.setter_name();
+    let setter = ctx.rust_ident_raw(setter);
+    quote! { #setter }
+}
+
+impl<'a> FieldCodegen<'a> for Bitfield {
+    type Extra = (&'a str, &'a mut bool, &'a mut FieldVisibilityKind);
+
+    fn codegen<F, M>(
+        &self,
+        ctx: &BindgenContext,
+        visibility_kind: FieldVisibilityKind,
+        _accessor_kind: FieldAccessorKind,
+        parent: &CompInfo,
+        parent_item: &Item,
+        _result: &mut CodegenResult,
+        struct_layout: &mut StructLayoutTracker,
+        _fields: &mut F,
+        methods: &mut M,
+        (unit_field_name, bitfield_representable_as_int, bitfield_visibility): (
+            &'a str,
+            &mut bool,
+            &'a mut FieldVisibilityKind,
+        ),
+    ) where
+        F: Extend<proc_macro2::TokenStream>,
+        M: Extend<proc_macro2::TokenStream>,
+    {
+        let prefix = ctx.trait_prefix();
+        let getter_name = bitfield_getter_name(ctx, self);
+        let setter_name = bitfield_setter_name(ctx, self);
+        let unit_field_ident = Ident::new(unit_field_name, Span::call_site());
+
+        let bitfield_ty_item = ctx.resolve_item(self.ty());
+        let bitfield_ty = bitfield_ty_item.expect_type();
+
+        let bitfield_ty_layout = bitfield_ty
+            .layout(ctx)
+            .expect("Bitfield without layout? Gah!");
+        let bitfield_int_ty =
+            match helpers::integer_type(ctx, bitfield_ty_layout) {
+                Some(int_ty) => {
+                    *bitfield_representable_as_int = true;
+                    int_ty
+                }
+                None => {
+                    *bitfield_representable_as_int = false;
+                    return;
+                }
+            };
+
+        let bitfield_ty =
+            bitfield_ty.to_rust_ty_or_opaque(ctx, bitfield_ty_item);
+
+        let offset = self.offset_into_unit();
+        let width = self.width() as u8;
+
+        let override_visibility = self.name().and_then(|field_name| {
+            ctx.options().last_callback(|cb| {
+                cb.field_visibility(FieldInfo {
+                    type_name: &parent_item.canonical_name(ctx),
+                    field_name,
+                })
+            })
+        });
+        *bitfield_visibility = compute_visibility(
+            ctx,
+            self.is_public(),
+            override_visibility,
+            self.annotations(),
+            visibility_kind,
+        );
+        let access_spec = access_specifier(*bitfield_visibility);
+
+        if parent.is_union() && !struct_layout.is_rust_union() {
+            methods.extend(Some(quote! {
+                #[inline]
+                #access_spec fn #getter_name(&self) -> #bitfield_ty {
+                    unsafe {
+                        ::#prefix::mem::transmute(
+                            self.#unit_field_ident.as_ref().get(#offset, #width)
+                                as #bitfield_int_ty
+                        )
+                    }
+                }
+
+                #[inline]
+                #access_spec fn #setter_name(&mut self, val: #bitfield_ty) {
+                    unsafe {
+                        let val: #bitfield_int_ty = ::#prefix::mem::transmute(val);
+                        self.#unit_field_ident.as_mut().set(
+                            #offset,
+                            #width,
+                            val as u64
+                        )
+                    }
+                }
+            }));
+        } else {
+            methods.extend(Some(quote! {
+                #[inline]
+                #access_spec fn #getter_name(&self) -> #bitfield_ty {
+                    unsafe {
+                        ::#prefix::mem::transmute(
+                            self.#unit_field_ident.get(#offset, #width)
+                                as #bitfield_int_ty
+                        )
+                    }
+                }
+
+                #[inline]
+                #access_spec fn #setter_name(&mut self, val: #bitfield_ty) {
+                    unsafe {
+                        let val: #bitfield_int_ty = ::#prefix::mem::transmute(val);
+                        self.#unit_field_ident.set(
+                            #offset,
+                            #width,
+                            val as u64
+                        )
+                    }
+                }
+            }));
+        }
+    }
+}
+
+impl CodeGenerator for CompInfo {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        debug!("<CompInfo as CodeGenerator>::codegen: item = {:?}", item);
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+
+        // Don't output classes with template parameters that aren't types, and
+        // also don't output template specializations, neither total or partial.
+        if self.has_non_type_template_params() {
+            return;
+        }
+
+        let ty = item.expect_type();
+        let layout = ty.layout(ctx);
+        let mut packed = self.is_packed(ctx, layout.as_ref());
+
+        let canonical_name = item.canonical_name(ctx);
+        let canonical_ident = ctx.rust_ident(&canonical_name);
+
+        // Generate the vtable from the method list if appropriate.
+        //
+        // TODO: I don't know how this could play with virtual methods that are
+        // not in the list of methods found by us, we'll see. Also, could the
+        // order of the vtable pointers vary?
+        //
+        // FIXME: Once we generate proper vtables, we need to codegen the
+        // vtable, but *not* generate a field for it in the case that
+        // HasVtable::has_vtable_ptr is false but HasVtable::has_vtable is true.
+        //
+        // Also, we need to generate the vtable in such a way it "inherits" from
+        // the parent too.
+        let is_opaque = item.is_opaque(ctx, &());
+        let mut fields = vec![];
+        let visibility = item
+            .annotations()
+            .visibility_kind()
+            .unwrap_or(ctx.options().default_visibility);
+        let mut struct_layout = StructLayoutTracker::new(
+            ctx,
+            self,
+            ty,
+            &canonical_name,
+            visibility,
+            packed,
+        );
+
+        if !is_opaque {
+            if item.has_vtable_ptr(ctx) {
+                let vtable = Vtable::new(item.id(), self);
+                vtable.codegen(ctx, result, item);
+
+                let vtable_type = vtable
+                    .try_to_rust_ty(ctx, &())
+                    .expect("vtable to Rust type conversion is infallible")
+                    .to_ptr(true);
+
+                fields.push(quote! {
+                    pub vtable_: #vtable_type ,
+                });
+
+                struct_layout.saw_vtable();
+            }
+
+            for base in self.base_members() {
+                if !base.requires_storage(ctx) {
+                    continue;
+                }
+
+                let inner_item = ctx.resolve_item(base.ty);
+                let inner = inner_item
+                    .to_rust_ty_or_opaque(ctx, &())
+                    .with_implicit_template_params(ctx, inner_item);
+                let field_name = ctx.rust_ident(&base.field_name);
+
+                struct_layout.saw_base(inner_item.expect_type());
+
+                let visibility = match (
+                    base.is_public(),
+                    ctx.options().respect_cxx_access_specs,
+                ) {
+                    (true, true) => FieldVisibilityKind::Public,
+                    (false, true) => FieldVisibilityKind::Private,
+                    _ => ctx.options().default_visibility,
+                };
+
+                let access_spec = access_specifier(visibility);
+                fields.push(quote! {
+                    #access_spec #field_name: #inner,
+                });
+            }
+        }
+
+        let mut methods = vec![];
+        if !is_opaque {
+            let struct_accessor_kind = item
+                .annotations()
+                .accessor_kind()
+                .unwrap_or(FieldAccessorKind::None);
+            for field in self.fields() {
+                field.codegen(
+                    ctx,
+                    visibility,
+                    struct_accessor_kind,
+                    self,
+                    item,
+                    result,
+                    &mut struct_layout,
+                    &mut fields,
+                    &mut methods,
+                    (),
+                );
+            }
+            // Check whether an explicit padding field is needed
+            // at the end.
+            if let Some(comp_layout) = layout {
+                fields.extend(
+                    struct_layout
+                        .add_tail_padding(&canonical_name, comp_layout),
+                );
+            }
+        }
+
+        if is_opaque {
+            // Opaque item should not have generated methods, fields.
+            debug_assert!(fields.is_empty());
+            debug_assert!(methods.is_empty());
+        }
+
+        let is_union = self.kind() == CompKind::Union;
+        let layout = item.kind().expect_type().layout(ctx);
+        let zero_sized = item.is_zero_sized(ctx);
+        let forward_decl = self.is_forward_declaration();
+
+        let mut explicit_align = None;
+
+        // C++ requires every struct to be addressable, so what C++ compilers do
+        // is making the struct 1-byte sized.
+        //
+        // This is apparently not the case for C, see:
+        // https://github.com/rust-lang/rust-bindgen/issues/551
+        //
+        // Just get the layout, and assume C++ if not.
+        //
+        // NOTE: This check is conveniently here to avoid the dummy fields we
+        // may add for unused template parameters.
+        if !forward_decl && zero_sized {
+            let has_address = if is_opaque {
+                // Generate the address field if it's an opaque type and
+                // couldn't determine the layout of the blob.
+                layout.is_none()
+            } else {
+                layout.map_or(true, |l| l.size != 0)
+            };
+
+            if has_address {
+                let layout = Layout::new(1, 1);
+                let ty = helpers::blob(ctx, Layout::new(1, 1));
+                struct_layout.saw_field_with_layout(
+                    "_address",
+                    layout,
+                    /* offset = */ Some(0),
+                );
+                fields.push(quote! {
+                    pub _address: #ty,
+                });
+            }
+        }
+
+        if is_opaque {
+            match layout {
+                Some(l) => {
+                    explicit_align = Some(l.align);
+
+                    let ty = helpers::blob(ctx, l);
+                    fields.push(quote! {
+                        pub _bindgen_opaque_blob: #ty ,
+                    });
+                }
+                None => {
+                    warn!("Opaque type without layout! Expect dragons!");
+                }
+            }
+        } else if !is_union && !zero_sized {
+            if let Some(padding_field) =
+                layout.and_then(|layout| struct_layout.pad_struct(layout))
+            {
+                fields.push(padding_field);
+            }
+
+            if let Some(layout) = layout {
+                if struct_layout.requires_explicit_align(layout) {
+                    if layout.align == 1 {
+                        packed = true;
+                    } else {
+                        explicit_align = Some(layout.align);
+                        if !ctx.options().rust_features.repr_align {
+                            let ty = helpers::blob(
+                                ctx,
+                                Layout::new(0, layout.align),
+                            );
+                            fields.push(quote! {
+                                pub __bindgen_align: #ty ,
+                            });
+                        }
+                    }
+                }
+            }
+        } else if is_union && !forward_decl {
+            // TODO(emilio): It'd be nice to unify this with the struct path
+            // above somehow.
+            let layout = layout.expect("Unable to get layout information?");
+            if struct_layout.requires_explicit_align(layout) {
+                explicit_align = Some(layout.align);
+            }
+
+            if !struct_layout.is_rust_union() {
+                let ty = helpers::blob(ctx, layout);
+                fields.push(quote! {
+                    pub bindgen_union_field: #ty ,
+                })
+            }
+        }
+
+        if forward_decl {
+            fields.push(quote! {
+                _unused: [u8; 0],
+            });
+        }
+
+        let mut generic_param_names = vec![];
+
+        for (idx, ty) in item.used_template_params(ctx).iter().enumerate() {
+            let param = ctx.resolve_type(*ty);
+            let name = param.name().unwrap();
+            let ident = ctx.rust_ident(name);
+            generic_param_names.push(ident.clone());
+
+            let prefix = ctx.trait_prefix();
+            let field_name = ctx.rust_ident(format!("_phantom_{}", idx));
+            fields.push(quote! {
+                pub #field_name : ::#prefix::marker::PhantomData<
+                    ::#prefix::cell::UnsafeCell<#ident>
+                > ,
+            });
+        }
+
+        let generics = if !generic_param_names.is_empty() {
+            let generic_param_names = generic_param_names.clone();
+            quote! {
+                < #( #generic_param_names ),* >
+            }
+        } else {
+            quote! {}
+        };
+
+        let mut attributes = vec![];
+        let mut needs_clone_impl = false;
+        let mut needs_default_impl = false;
+        let mut needs_debug_impl = false;
+        let mut needs_partialeq_impl = false;
+        if let Some(comment) = item.comment(ctx) {
+            attributes.push(attributes::doc(comment));
+        }
+
+        // if a type has both a "packed" attribute and an "align(N)" attribute, then check if the
+        // "packed" attr is redundant, and do not include it if so.
+        if packed &&
+            !is_opaque &&
+            !(explicit_align.is_some() &&
+                self.already_packed(ctx).unwrap_or(false))
+        {
+            let n = layout.map_or(1, |l| l.align);
+            assert!(ctx.options().rust_features().repr_packed_n || n == 1);
+            let packed_repr = if n == 1 {
+                "packed".to_string()
+            } else {
+                format!("packed({})", n)
+            };
+            attributes.push(attributes::repr_list(&["C", &packed_repr]));
+        } else {
+            attributes.push(attributes::repr("C"));
+        }
+
+        if ctx.options().rust_features().repr_align {
+            if let Some(explicit) = explicit_align {
+                // Ensure that the struct has the correct alignment even in
+                // presence of alignas.
+                let explicit = helpers::ast_ty::int_expr(explicit as i64);
+                attributes.push(quote! {
+                    #[repr(align(#explicit))]
+                });
+            }
+        }
+
+        let derivable_traits = derives_of_item(item, ctx, packed);
+        if !derivable_traits.contains(DerivableTraits::DEBUG) {
+            needs_debug_impl = ctx.options().derive_debug &&
+                ctx.options().impl_debug &&
+                !ctx.no_debug_by_name(item) &&
+                !item.annotations().disallow_debug();
+        }
+
+        if !derivable_traits.contains(DerivableTraits::DEFAULT) {
+            needs_default_impl = ctx.options().derive_default &&
+                !self.is_forward_declaration() &&
+                !ctx.no_default_by_name(item) &&
+                !item.annotations().disallow_default();
+        }
+
+        let all_template_params = item.all_template_params(ctx);
+
+        if derivable_traits.contains(DerivableTraits::COPY) &&
+            !derivable_traits.contains(DerivableTraits::CLONE)
+        {
+            needs_clone_impl = true;
+        }
+
+        if !derivable_traits.contains(DerivableTraits::PARTIAL_EQ) {
+            needs_partialeq_impl = ctx.options().derive_partialeq &&
+                ctx.options().impl_partialeq &&
+                ctx.lookup_can_derive_partialeq_or_partialord(item.id()) ==
+                    CanDerive::Manually;
+        }
+
+        let mut derives: Vec<_> = derivable_traits.into();
+        derives.extend(item.annotations().derives().iter().map(String::as_str));
+
+        let is_rust_union = is_union && struct_layout.is_rust_union();
+
+        // The custom derives callback may return a list of derive attributes;
+        // add them to the end of the list.
+        let custom_derives = ctx.options().all_callbacks(|cb| {
+            cb.add_derives(&DeriveInfo {
+                name: &canonical_name,
+                kind: if is_rust_union {
+                    DeriveTypeKind::Union
+                } else {
+                    DeriveTypeKind::Struct
+                },
+            })
+        });
+        // In most cases this will be a no-op, since custom_derives will be empty.
+        derives.extend(custom_derives.iter().map(|s| s.as_str()));
+
+        if !derives.is_empty() {
+            attributes.push(attributes::derives(&derives))
+        }
+
+        if item.must_use(ctx) {
+            attributes.push(attributes::must_use());
+        }
+
+        let mut tokens = if is_rust_union {
+            quote! {
+                #( #attributes )*
+                pub union #canonical_ident
+            }
+        } else {
+            quote! {
+                #( #attributes )*
+                pub struct #canonical_ident
+            }
+        };
+
+        tokens.append_all(quote! {
+            #generics {
+                #( #fields )*
+            }
+        });
+        result.push(tokens);
+
+        // Generate the inner types and all that stuff.
+        //
+        // TODO: In the future we might want to be smart, and use nested
+        // modules, and whatnot.
+        for ty in self.inner_types() {
+            let child_item = ctx.resolve_item(*ty);
+            // assert_eq!(child_item.parent_id(), item.id());
+            child_item.codegen(ctx, result, &());
+        }
+
+        // NOTE: Some unexposed attributes (like alignment attributes) may
+        // affect layout, so we're bad and pray to the gods for avoid sending
+        // all the tests to shit when parsing things like max_align_t.
+        if self.found_unknown_attr() {
+            warn!(
+                "Type {} has an unknown attribute that may affect layout",
+                canonical_ident
+            );
+        }
+
+        if all_template_params.is_empty() {
+            if !is_opaque {
+                for var in self.inner_vars() {
+                    ctx.resolve_item(*var).codegen(ctx, result, &());
+                }
+            }
+
+            if ctx.options().layout_tests && !self.is_forward_declaration() {
+                if let Some(layout) = layout {
+                    let fn_name =
+                        format!("bindgen_test_layout_{}", canonical_ident);
+                    let fn_name = ctx.rust_ident_raw(fn_name);
+                    let prefix = ctx.trait_prefix();
+                    let size_of_expr = quote! {
+                        ::#prefix::mem::size_of::<#canonical_ident>()
+                    };
+                    let align_of_expr = quote! {
+                        ::#prefix::mem::align_of::<#canonical_ident>()
+                    };
+                    let size = layout.size;
+                    let align = layout.align;
+
+                    let check_struct_align = if align >
+                        ctx.target_pointer_size() &&
+                        !ctx.options().rust_features().repr_align
+                    {
+                        None
+                    } else {
+                        Some(quote! {
+                            assert_eq!(#align_of_expr,
+                                   #align,
+                                   concat!("Alignment of ", stringify!(#canonical_ident)));
+
+                        })
+                    };
+
+                    let should_skip_field_offset_checks = is_opaque;
+
+                    let check_field_offset = if should_skip_field_offset_checks
+                    {
+                        vec![]
+                    } else {
+                        self.fields()
+                            .iter()
+                            .filter_map(|field| match *field {
+                                Field::DataMember(ref f) if f.name().is_some() => Some(f),
+                                _ => None,
+                            })
+                            .flat_map(|field| {
+                                let name = field.name().unwrap();
+                                field.offset().map(|offset| {
+                                    let field_offset = offset / 8;
+                                    let field_name = ctx.rust_ident(name);
+                                    quote! {
+                                        assert_eq!(
+                                            unsafe {
+                                                ::#prefix::ptr::addr_of!((*ptr).#field_name) as usize - ptr as usize
+                                            },
+                                            #field_offset,
+                                            concat!("Offset of field: ", stringify!(#canonical_ident), "::", stringify!(#field_name))
+                                        );
+                                    }
+                                })
+                            })
+                            .collect()
+                    };
+
+                    let uninit_decl = if !check_field_offset.is_empty() {
+                        // FIXME: When MSRV >= 1.59.0, we can use
+                        // > const PTR: *const #canonical_ident = ::#prefix::mem::MaybeUninit::uninit().as_ptr();
+                        Some(quote! {
+                            // Use a shared MaybeUninit so that rustc with
+                            // opt-level=0 doesn't take too much stack space,
+                            // see #2218.
+                            const UNINIT: ::#prefix::mem::MaybeUninit<#canonical_ident> = ::#prefix::mem::MaybeUninit::uninit();
+                            let ptr = UNINIT.as_ptr();
+                        })
+                    } else {
+                        None
+                    };
+
+                    let item = quote! {
+                        #[test]
+                        fn #fn_name() {
+                            #uninit_decl
+                            assert_eq!(#size_of_expr,
+                                       #size,
+                                       concat!("Size of: ", stringify!(#canonical_ident)));
+                            #check_struct_align
+                            #( #check_field_offset )*
+                        }
+                    };
+                    result.push(item);
+                }
+            }
+
+            let mut method_names = Default::default();
+            if ctx.options().codegen_config.methods() {
+                for method in self.methods() {
+                    assert!(method.kind() != MethodKind::Constructor);
+                    method.codegen_method(
+                        ctx,
+                        &mut methods,
+                        &mut method_names,
+                        result,
+                        self,
+                    );
+                }
+            }
+
+            if ctx.options().codegen_config.constructors() {
+                for sig in self.constructors() {
+                    Method::new(
+                        MethodKind::Constructor,
+                        *sig,
+                        /* const */
+                        false,
+                    )
+                    .codegen_method(
+                        ctx,
+                        &mut methods,
+                        &mut method_names,
+                        result,
+                        self,
+                    );
+                }
+            }
+
+            if ctx.options().codegen_config.destructors() {
+                if let Some((kind, destructor)) = self.destructor() {
+                    debug_assert!(kind.is_destructor());
+                    Method::new(kind, destructor, false).codegen_method(
+                        ctx,
+                        &mut methods,
+                        &mut method_names,
+                        result,
+                        self,
+                    );
+                }
+            }
+        }
+
+        // NB: We can't use to_rust_ty here since for opaque types this tries to
+        // use the specialization knowledge to generate a blob field.
+        let ty_for_impl = quote! {
+            #canonical_ident #generics
+        };
+
+        if needs_clone_impl {
+            result.push(quote! {
+                impl #generics Clone for #ty_for_impl {
+                    fn clone(&self) -> Self { *self }
+                }
+            });
+        }
+
+        if needs_default_impl {
+            let prefix = ctx.trait_prefix();
+            let body = if ctx.options().rust_features().maybe_uninit {
+                quote! {
+                    let mut s = ::#prefix::mem::MaybeUninit::<Self>::uninit();
+                    unsafe {
+                        ::#prefix::ptr::write_bytes(s.as_mut_ptr(), 0, 1);
+                        s.assume_init()
+                    }
+                }
+            } else {
+                quote! {
+                    unsafe {
+                        let mut s: Self = ::#prefix::mem::uninitialized();
+                        ::#prefix::ptr::write_bytes(&mut s, 0, 1);
+                        s
+                    }
+                }
+            };
+            // Note we use `ptr::write_bytes()` instead of `mem::zeroed()` because the latter does
+            // not necessarily ensure padding bytes are zeroed. Some C libraries are sensitive to
+            // non-zero padding bytes, especially when forwards/backwards compatability is
+            // involved.
+            result.push(quote! {
+                impl #generics Default for #ty_for_impl {
+                    fn default() -> Self {
+                        #body
+                    }
+                }
+            });
+        }
+
+        if needs_debug_impl {
+            let impl_ = impl_debug::gen_debug_impl(
+                ctx,
+                self.fields(),
+                item,
+                self.kind(),
+            );
+
+            let prefix = ctx.trait_prefix();
+
+            result.push(quote! {
+                impl #generics ::#prefix::fmt::Debug for #ty_for_impl {
+                    #impl_
+                }
+            });
+        }
+
+        if needs_partialeq_impl {
+            if let Some(impl_) = impl_partialeq::gen_partialeq_impl(
+                ctx,
+                self,
+                item,
+                &ty_for_impl,
+            ) {
+                let partialeq_bounds = if !generic_param_names.is_empty() {
+                    let bounds = generic_param_names.iter().map(|t| {
+                        quote! { #t: PartialEq }
+                    });
+                    quote! { where #( #bounds ),* }
+                } else {
+                    quote! {}
+                };
+
+                let prefix = ctx.trait_prefix();
+                result.push(quote! {
+                    impl #generics ::#prefix::cmp::PartialEq for #ty_for_impl #partialeq_bounds {
+                        #impl_
+                    }
+                });
+            }
+        }
+
+        if !methods.is_empty() {
+            result.push(quote! {
+                impl #generics #ty_for_impl {
+                    #( #methods )*
+                }
+            });
+        }
+    }
+}
+
+impl Method {
+    fn codegen_method(
+        &self,
+        ctx: &BindgenContext,
+        methods: &mut Vec<proc_macro2::TokenStream>,
+        method_names: &mut HashSet<String>,
+        result: &mut CodegenResult<'_>,
+        _parent: &CompInfo,
+    ) {
+        assert!({
+            let cc = &ctx.options().codegen_config;
+            match self.kind() {
+                MethodKind::Constructor => cc.constructors(),
+                MethodKind::Destructor => cc.destructors(),
+                MethodKind::VirtualDestructor { .. } => cc.destructors(),
+                MethodKind::Static |
+                MethodKind::Normal |
+                MethodKind::Virtual { .. } => cc.methods(),
+            }
+        });
+
+        // TODO(emilio): We could generate final stuff at least.
+        if self.is_virtual() {
+            return; // FIXME
+        }
+
+        // First of all, output the actual function.
+        let function_item = ctx.resolve_item(self.signature());
+        if !function_item.process_before_codegen(ctx, result) {
+            return;
+        }
+        let function = function_item.expect_function();
+        let times_seen = function.codegen(ctx, result, function_item);
+        let times_seen = match times_seen {
+            Some(seen) => seen,
+            None => return,
+        };
+        let signature_item = ctx.resolve_item(function.signature());
+        let mut name = match self.kind() {
+            MethodKind::Constructor => "new".into(),
+            MethodKind::Destructor => "destruct".into(),
+            _ => function.name().to_owned(),
+        };
+
+        let signature = match *signature_item.expect_type().kind() {
+            TypeKind::Function(ref sig) => sig,
+            _ => panic!("How in the world?"),
+        };
+
+        let supported_abi = signature.abi(ctx, Some(&*name)).is_ok();
+        if !supported_abi {
+            return;
+        }
+
+        // Do not generate variadic methods, since rust does not allow
+        // implementing them, and we don't do a good job at it anyway.
+        if signature.is_variadic() {
+            return;
+        }
+
+        if method_names.contains(&name) {
+            let mut count = 1;
+            let mut new_name;
+
+            while {
+                new_name = format!("{}{}", name, count);
+                method_names.contains(&new_name)
+            } {
+                count += 1;
+            }
+
+            name = new_name;
+        }
+
+        method_names.insert(name.clone());
+
+        let mut function_name = function_item.canonical_name(ctx);
+        if times_seen > 0 {
+            write!(&mut function_name, "{}", times_seen).unwrap();
+        }
+        let function_name = ctx.rust_ident(function_name);
+        let mut args = utils::fnsig_arguments(ctx, signature);
+        let mut ret = utils::fnsig_return_ty(ctx, signature);
+
+        if !self.is_static() && !self.is_constructor() {
+            args[0] = if self.is_const() {
+                quote! { &self }
+            } else {
+                quote! { &mut self }
+            };
+        }
+
+        // If it's a constructor, we always return `Self`, and we inject the
+        // "this" parameter, so there's no need to ask the user for it.
+        //
+        // Note that constructors in Clang are represented as functions with
+        // return-type = void.
+        if self.is_constructor() {
+            args.remove(0);
+            ret = quote! { -> Self };
+        }
+
+        let mut exprs =
+            helpers::ast_ty::arguments_from_signature(signature, ctx);
+
+        let mut stmts = vec![];
+
+        // If it's a constructor, we need to insert an extra parameter with a
+        // variable called `__bindgen_tmp` we're going to create.
+        if self.is_constructor() {
+            let prefix = ctx.trait_prefix();
+            let tmp_variable_decl = if ctx
+                .options()
+                .rust_features()
+                .maybe_uninit
+            {
+                exprs[0] = quote! {
+                    __bindgen_tmp.as_mut_ptr()
+                };
+                quote! {
+                    let mut __bindgen_tmp = ::#prefix::mem::MaybeUninit::uninit()
+                }
+            } else {
+                exprs[0] = quote! {
+                    &mut __bindgen_tmp
+                };
+                quote! {
+                    let mut __bindgen_tmp = ::#prefix::mem::uninitialized()
+                }
+            };
+            stmts.push(tmp_variable_decl);
+        } else if !self.is_static() {
+            assert!(!exprs.is_empty());
+            exprs[0] = quote! {
+                self
+            };
+        };
+
+        let call = quote! {
+            #function_name (#( #exprs ),* )
+        };
+
+        stmts.push(call);
+
+        if self.is_constructor() {
+            stmts.push(if ctx.options().rust_features().maybe_uninit {
+                quote! {
+                    __bindgen_tmp.assume_init()
+                }
+            } else {
+                quote! {
+                    __bindgen_tmp
+                }
+            })
+        }
+
+        let block = ctx.wrap_unsafe_ops(quote! ( #( #stmts );*));
+
+        let mut attrs = vec![attributes::inline()];
+
+        if signature.must_use() &&
+            ctx.options().rust_features().must_use_function
+        {
+            attrs.push(attributes::must_use());
+        }
+
+        let name = ctx.rust_ident(&name);
+        methods.push(quote! {
+            #(#attrs)*
+            pub unsafe fn #name ( #( #args ),* ) #ret {
+                #block
+            }
+        });
+    }
+}
+
+/// A helper type that represents different enum variations.
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum EnumVariation {
+    /// The code for this enum will use a Rust enum. Note that creating this in unsafe code
+    /// (including FFI) with an invalid value will invoke undefined behaviour, whether or not
+    /// its marked as non_exhaustive.
+    Rust {
+        /// Indicates whether the generated struct should be `#[non_exhaustive]`
+        non_exhaustive: bool,
+    },
+    /// The code for this enum will use a newtype
+    NewType {
+        /// Indicates whether the newtype will have bitwise operators
+        is_bitfield: bool,
+        /// Indicates whether the variants will be represented as global constants
+        is_global: bool,
+    },
+    /// The code for this enum will use consts
+    Consts,
+    /// The code for this enum will use a module containing consts
+    ModuleConsts,
+}
+
+impl EnumVariation {
+    fn is_rust(&self) -> bool {
+        matches!(*self, EnumVariation::Rust { .. })
+    }
+
+    /// Both the `Const` and `ModuleConsts` variants will cause this to return
+    /// true.
+    fn is_const(&self) -> bool {
+        matches!(*self, EnumVariation::Consts | EnumVariation::ModuleConsts)
+    }
+}
+
+impl Default for EnumVariation {
+    fn default() -> EnumVariation {
+        EnumVariation::Consts
+    }
+}
+
+impl fmt::Display for EnumVariation {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = match self {
+            Self::Rust {
+                non_exhaustive: false,
+            } => "rust",
+            Self::Rust {
+                non_exhaustive: true,
+            } => "rust_non_exhaustive",
+            Self::NewType {
+                is_bitfield: true, ..
+            } => "bitfield",
+            Self::NewType {
+                is_bitfield: false,
+                is_global,
+            } => {
+                if *is_global {
+                    "newtype_global"
+                } else {
+                    "newtype"
+                }
+            }
+            Self::Consts => "consts",
+            Self::ModuleConsts => "moduleconsts",
+        };
+        s.fmt(f)
+    }
+}
+
+impl std::str::FromStr for EnumVariation {
+    type Err = std::io::Error;
+
+    /// Create a `EnumVariation` from a string.
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "rust" => Ok(EnumVariation::Rust {
+                non_exhaustive: false,
+            }),
+            "rust_non_exhaustive" => Ok(EnumVariation::Rust {
+                non_exhaustive: true,
+            }),
+            "bitfield" => Ok(EnumVariation::NewType {
+                is_bitfield: true,
+                is_global: false,
+            }),
+            "consts" => Ok(EnumVariation::Consts),
+            "moduleconsts" => Ok(EnumVariation::ModuleConsts),
+            "newtype" => Ok(EnumVariation::NewType {
+                is_bitfield: false,
+                is_global: false,
+            }),
+            "newtype_global" => Ok(EnumVariation::NewType {
+                is_bitfield: false,
+                is_global: true,
+            }),
+            _ => Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                concat!(
+                    "Got an invalid EnumVariation. Accepted values ",
+                    "are 'rust', 'rust_non_exhaustive', 'bitfield', 'consts',",
+                    "'moduleconsts', 'newtype' and 'newtype_global'."
+                ),
+            )),
+        }
+    }
+}
+
+/// A helper type to construct different enum variations.
+enum EnumBuilder<'a> {
+    Rust {
+        attrs: Vec<proc_macro2::TokenStream>,
+        ident: Ident,
+        tokens: proc_macro2::TokenStream,
+        emitted_any_variants: bool,
+    },
+    NewType {
+        canonical_name: &'a str,
+        tokens: proc_macro2::TokenStream,
+        is_bitfield: bool,
+        is_global: bool,
+    },
+    Consts {
+        variants: Vec<proc_macro2::TokenStream>,
+    },
+    ModuleConsts {
+        module_name: &'a str,
+        module_items: Vec<proc_macro2::TokenStream>,
+    },
+}
+
+impl<'a> EnumBuilder<'a> {
+    /// Returns true if the builder is for a rustified enum.
+    fn is_rust_enum(&self) -> bool {
+        matches!(*self, EnumBuilder::Rust { .. })
+    }
+
+    /// Create a new enum given an item builder, a canonical name, a name for
+    /// the representation, and which variation it should be generated as.
+    fn new(
+        name: &'a str,
+        mut attrs: Vec<proc_macro2::TokenStream>,
+        repr: syn::Type,
+        enum_variation: EnumVariation,
+        has_typedef: bool,
+    ) -> Self {
+        let ident = Ident::new(name, Span::call_site());
+
+        match enum_variation {
+            EnumVariation::NewType {
+                is_bitfield,
+                is_global,
+            } => EnumBuilder::NewType {
+                canonical_name: name,
+                tokens: quote! {
+                    #( #attrs )*
+                    pub struct #ident (pub #repr);
+                },
+                is_bitfield,
+                is_global,
+            },
+
+            EnumVariation::Rust { .. } => {
+                // `repr` is guaranteed to be Rustified in Enum::codegen
+                attrs.insert(0, quote! { #[repr( #repr )] });
+                let tokens = quote!();
+                EnumBuilder::Rust {
+                    attrs,
+                    ident,
+                    tokens,
+                    emitted_any_variants: false,
+                }
+            }
+
+            EnumVariation::Consts => {
+                let mut variants = Vec::new();
+
+                if !has_typedef {
+                    variants.push(quote! {
+                        #( #attrs )*
+                        pub type #ident = #repr;
+                    });
+                }
+
+                EnumBuilder::Consts { variants }
+            }
+
+            EnumVariation::ModuleConsts => {
+                let ident = Ident::new(
+                    CONSTIFIED_ENUM_MODULE_REPR_NAME,
+                    Span::call_site(),
+                );
+                let type_definition = quote! {
+                    #( #attrs )*
+                    pub type #ident = #repr;
+                };
+
+                EnumBuilder::ModuleConsts {
+                    module_name: name,
+                    module_items: vec![type_definition],
+                }
+            }
+        }
+    }
+
+    /// Add a variant to this enum.
+    fn with_variant(
+        self,
+        ctx: &BindgenContext,
+        variant: &EnumVariant,
+        mangling_prefix: Option<&str>,
+        rust_ty: syn::Type,
+        result: &mut CodegenResult<'_>,
+        is_ty_named: bool,
+    ) -> Self {
+        let variant_name = ctx.rust_mangle(variant.name());
+        let is_rust_enum = self.is_rust_enum();
+        let expr = match variant.val() {
+            EnumVariantValue::Boolean(v) if is_rust_enum => {
+                helpers::ast_ty::uint_expr(v as u64)
+            }
+            EnumVariantValue::Boolean(v) => quote!(#v),
+            EnumVariantValue::Signed(v) => helpers::ast_ty::int_expr(v),
+            EnumVariantValue::Unsigned(v) => helpers::ast_ty::uint_expr(v),
+        };
+
+        let mut doc = quote! {};
+        if ctx.options().generate_comments {
+            if let Some(raw_comment) = variant.comment() {
+                let comment = ctx.options().process_comment(raw_comment);
+                doc = attributes::doc(comment);
+            }
+        }
+
+        match self {
+            EnumBuilder::Rust {
+                attrs,
+                ident,
+                tokens,
+                emitted_any_variants: _,
+            } => {
+                let name = ctx.rust_ident(variant_name);
+                EnumBuilder::Rust {
+                    attrs,
+                    ident,
+                    tokens: quote! {
+                        #tokens
+                        #doc
+                        #name = #expr,
+                    },
+                    emitted_any_variants: true,
+                }
+            }
+
+            EnumBuilder::NewType {
+                canonical_name,
+                is_global,
+                ..
+            } => {
+                if ctx.options().rust_features().associated_const &&
+                    is_ty_named &&
+                    !is_global
+                {
+                    let enum_ident = ctx.rust_ident(canonical_name);
+                    let variant_ident = ctx.rust_ident(variant_name);
+
+                    result.push(quote! {
+                        impl #enum_ident {
+                            #doc
+                            pub const #variant_ident : #rust_ty = #rust_ty ( #expr );
+                        }
+                    });
+                } else {
+                    let ident = ctx.rust_ident(match mangling_prefix {
+                        Some(prefix) => {
+                            Cow::Owned(format!("{}_{}", prefix, variant_name))
+                        }
+                        None => variant_name,
+                    });
+                    result.push(quote! {
+                        #doc
+                        pub const #ident : #rust_ty = #rust_ty ( #expr );
+                    });
+                }
+
+                self
+            }
+
+            EnumBuilder::Consts { .. } => {
+                let constant_name = match mangling_prefix {
+                    Some(prefix) => {
+                        Cow::Owned(format!("{}_{}", prefix, variant_name))
+                    }
+                    None => variant_name,
+                };
+
+                let ident = ctx.rust_ident(constant_name);
+                result.push(quote! {
+                    #doc
+                    pub const #ident : #rust_ty = #expr ;
+                });
+
+                self
+            }
+            EnumBuilder::ModuleConsts {
+                module_name,
+                mut module_items,
+            } => {
+                let name = ctx.rust_ident(variant_name);
+                let ty = ctx.rust_ident(CONSTIFIED_ENUM_MODULE_REPR_NAME);
+                module_items.push(quote! {
+                    #doc
+                    pub const #name : #ty = #expr ;
+                });
+
+                EnumBuilder::ModuleConsts {
+                    module_name,
+                    module_items,
+                }
+            }
+        }
+    }
+
+    fn build(
+        self,
+        ctx: &BindgenContext,
+        rust_ty: syn::Type,
+        result: &mut CodegenResult<'_>,
+    ) -> proc_macro2::TokenStream {
+        match self {
+            EnumBuilder::Rust {
+                attrs,
+                ident,
+                tokens,
+                emitted_any_variants,
+                ..
+            } => {
+                let variants = if !emitted_any_variants {
+                    quote!(__bindgen_cannot_repr_c_on_empty_enum = 0)
+                } else {
+                    tokens
+                };
+
+                quote! {
+                    #( #attrs )*
+                    pub enum #ident {
+                        #variants
+                    }
+                }
+            }
+            EnumBuilder::NewType {
+                canonical_name,
+                tokens,
+                is_bitfield,
+                ..
+            } => {
+                if !is_bitfield {
+                    return tokens;
+                }
+
+                let rust_ty_name = ctx.rust_ident_raw(canonical_name);
+                let prefix = ctx.trait_prefix();
+
+                result.push(quote! {
+                    impl ::#prefix::ops::BitOr<#rust_ty> for #rust_ty {
+                        type Output = Self;
+
+                        #[inline]
+                        fn bitor(self, other: Self) -> Self {
+                            #rust_ty_name(self.0 | other.0)
+                        }
+                    }
+                });
+
+                result.push(quote! {
+                    impl ::#prefix::ops::BitOrAssign for #rust_ty {
+                        #[inline]
+                        fn bitor_assign(&mut self, rhs: #rust_ty) {
+                            self.0 |= rhs.0;
+                        }
+                    }
+                });
+
+                result.push(quote! {
+                    impl ::#prefix::ops::BitAnd<#rust_ty> for #rust_ty {
+                        type Output = Self;
+
+                        #[inline]
+                        fn bitand(self, other: Self) -> Self {
+                            #rust_ty_name(self.0 & other.0)
+                        }
+                    }
+                });
+
+                result.push(quote! {
+                    impl ::#prefix::ops::BitAndAssign for #rust_ty {
+                        #[inline]
+                        fn bitand_assign(&mut self, rhs: #rust_ty) {
+                            self.0 &= rhs.0;
+                        }
+                    }
+                });
+
+                tokens
+            }
+            EnumBuilder::Consts { variants, .. } => quote! { #( #variants )* },
+            EnumBuilder::ModuleConsts {
+                module_items,
+                module_name,
+                ..
+            } => {
+                let ident = ctx.rust_ident(module_name);
+                quote! {
+                    pub mod #ident {
+                        #( #module_items )*
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl CodeGenerator for Enum {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        debug!("<Enum as CodeGenerator>::codegen: item = {:?}", item);
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+
+        let name = item.canonical_name(ctx);
+        let ident = ctx.rust_ident(&name);
+        let enum_ty = item.expect_type();
+        let layout = enum_ty.layout(ctx);
+        let variation = self.computed_enum_variation(ctx, item);
+
+        let repr_translated;
+        let repr = match self.repr().map(|repr| ctx.resolve_type(repr)) {
+            Some(repr)
+                if !ctx.options().translate_enum_integer_types &&
+                    !variation.is_rust() =>
+            {
+                repr
+            }
+            repr => {
+                // An enum's integer type is translated to a native Rust
+                // integer type in 3 cases:
+                // * the enum is Rustified and we need a translated type for
+                //   the repr attribute
+                // * the representation couldn't be determined from the C source
+                // * it was explicitly requested as a bindgen option
+
+                let kind = match repr {
+                    Some(repr) => match *repr.canonical_type(ctx).kind() {
+                        TypeKind::Int(int_kind) => int_kind,
+                        _ => panic!("Unexpected type as enum repr"),
+                    },
+                    None => {
+                        warn!(
+                            "Guessing type of enum! Forward declarations of enums \
+                             shouldn't be legal!"
+                        );
+                        IntKind::Int
+                    }
+                };
+
+                let signed = kind.is_signed();
+                let size = layout
+                    .map(|l| l.size)
+                    .or_else(|| kind.known_size())
+                    .unwrap_or(0);
+
+                let translated = match (signed, size) {
+                    (true, 1) => IntKind::I8,
+                    (false, 1) => IntKind::U8,
+                    (true, 2) => IntKind::I16,
+                    (false, 2) => IntKind::U16,
+                    (true, 4) => IntKind::I32,
+                    (false, 4) => IntKind::U32,
+                    (true, 8) => IntKind::I64,
+                    (false, 8) => IntKind::U64,
+                    _ => {
+                        warn!(
+                            "invalid enum decl: signed: {}, size: {}",
+                            signed, size
+                        );
+                        IntKind::I32
+                    }
+                };
+
+                repr_translated =
+                    Type::new(None, None, TypeKind::Int(translated), false);
+                &repr_translated
+            }
+        };
+
+        let mut attrs = vec![];
+
+        // TODO(emilio): Delegate this to the builders?
+        match variation {
+            EnumVariation::Rust { non_exhaustive } => {
+                if non_exhaustive &&
+                    ctx.options().rust_features().non_exhaustive
+                {
+                    attrs.push(attributes::non_exhaustive());
+                } else if non_exhaustive &&
+                    !ctx.options().rust_features().non_exhaustive
+                {
+                    panic!("The rust target you're using doesn't seem to support non_exhaustive enums");
+                }
+            }
+            EnumVariation::NewType { .. } => {
+                if ctx.options().rust_features.repr_transparent {
+                    attrs.push(attributes::repr("transparent"));
+                } else {
+                    attrs.push(attributes::repr("C"));
+                }
+            }
+            _ => {}
+        };
+
+        if let Some(comment) = item.comment(ctx) {
+            attrs.push(attributes::doc(comment));
+        }
+
+        if item.must_use(ctx) {
+            attrs.push(attributes::must_use());
+        }
+
+        if !variation.is_const() {
+            let packed = false; // Enums can't be packed in Rust.
+            let mut derives = derives_of_item(item, ctx, packed);
+            // For backwards compat, enums always derive
+            // Clone/Eq/PartialEq/Hash, even if we don't generate those by
+            // default.
+            derives.insert(
+                DerivableTraits::CLONE |
+                    DerivableTraits::HASH |
+                    DerivableTraits::PARTIAL_EQ |
+                    DerivableTraits::EQ,
+            );
+            let mut derives: Vec<_> = derives.into();
+            for derive in item.annotations().derives().iter() {
+                if !derives.contains(&derive.as_str()) {
+                    derives.push(derive);
+                }
+            }
+
+            // The custom derives callback may return a list of derive attributes;
+            // add them to the end of the list.
+            let custom_derives = ctx.options().all_callbacks(|cb| {
+                cb.add_derives(&DeriveInfo {
+                    name: &name,
+                    kind: DeriveTypeKind::Enum,
+                })
+            });
+            // In most cases this will be a no-op, since custom_derives will be empty.
+            derives.extend(custom_derives.iter().map(|s| s.as_str()));
+
+            attrs.push(attributes::derives(&derives));
+        }
+
+        fn add_constant(
+            ctx: &BindgenContext,
+            enum_: &Type,
+            // Only to avoid recomputing every time.
+            enum_canonical_name: &Ident,
+            // May be the same as "variant" if it's because the
+            // enum is unnamed and we still haven't seen the
+            // value.
+            variant_name: &Ident,
+            referenced_name: &Ident,
+            enum_rust_ty: syn::Type,
+            result: &mut CodegenResult<'_>,
+        ) {
+            let constant_name = if enum_.name().is_some() {
+                if ctx.options().prepend_enum_name {
+                    format!("{}_{}", enum_canonical_name, variant_name)
+                } else {
+                    format!("{}", variant_name)
+                }
+            } else {
+                format!("{}", variant_name)
+            };
+            let constant_name = ctx.rust_ident(constant_name);
+
+            result.push(quote! {
+                pub const #constant_name : #enum_rust_ty =
+                    #enum_canonical_name :: #referenced_name ;
+            });
+        }
+
+        let repr = repr.to_rust_ty_or_opaque(ctx, item);
+        let has_typedef = ctx.is_enum_typedef_combo(item.id());
+
+        let mut builder =
+            EnumBuilder::new(&name, attrs, repr, variation, has_typedef);
+
+        // A map where we keep a value -> variant relation.
+        let mut seen_values = HashMap::<_, Ident>::default();
+        let enum_rust_ty = item.to_rust_ty_or_opaque(ctx, &());
+        let is_toplevel = item.is_toplevel(ctx);
+
+        // Used to mangle the constants we generate in the unnamed-enum case.
+        let parent_canonical_name = if is_toplevel {
+            None
+        } else {
+            Some(item.parent_id().canonical_name(ctx))
+        };
+
+        let constant_mangling_prefix = if ctx.options().prepend_enum_name {
+            if enum_ty.name().is_none() {
+                parent_canonical_name.as_deref()
+            } else {
+                Some(&*name)
+            }
+        } else {
+            None
+        };
+
+        // NB: We defer the creation of constified variants, in case we find
+        // another variant with the same value (which is the common thing to
+        // do).
+        let mut constified_variants = VecDeque::new();
+
+        let mut iter = self.variants().iter().peekable();
+        while let Some(variant) =
+            iter.next().or_else(|| constified_variants.pop_front())
+        {
+            if variant.hidden() {
+                continue;
+            }
+
+            if variant.force_constification() && iter.peek().is_some() {
+                constified_variants.push_back(variant);
+                continue;
+            }
+
+            match seen_values.entry(variant.val()) {
+                Entry::Occupied(ref entry) => {
+                    if variation.is_rust() {
+                        let variant_name = ctx.rust_mangle(variant.name());
+                        let mangled_name =
+                            if is_toplevel || enum_ty.name().is_some() {
+                                variant_name
+                            } else {
+                                let parent_name =
+                                    parent_canonical_name.as_ref().unwrap();
+
+                                Cow::Owned(format!(
+                                    "{}_{}",
+                                    parent_name, variant_name
+                                ))
+                            };
+
+                        let existing_variant_name = entry.get();
+                        // Use associated constants for named enums.
+                        if enum_ty.name().is_some() &&
+                            ctx.options().rust_features().associated_const
+                        {
+                            let enum_canonical_name = &ident;
+                            let variant_name =
+                                ctx.rust_ident_raw(&*mangled_name);
+                            result.push(quote! {
+                                impl #enum_rust_ty {
+                                    pub const #variant_name : #enum_rust_ty =
+                                        #enum_canonical_name :: #existing_variant_name ;
+                                }
+                            });
+                        } else {
+                            add_constant(
+                                ctx,
+                                enum_ty,
+                                &ident,
+                                &Ident::new(&mangled_name, Span::call_site()),
+                                existing_variant_name,
+                                enum_rust_ty.clone(),
+                                result,
+                            );
+                        }
+                    } else {
+                        builder = builder.with_variant(
+                            ctx,
+                            variant,
+                            constant_mangling_prefix,
+                            enum_rust_ty.clone(),
+                            result,
+                            enum_ty.name().is_some(),
+                        );
+                    }
+                }
+                Entry::Vacant(entry) => {
+                    builder = builder.with_variant(
+                        ctx,
+                        variant,
+                        constant_mangling_prefix,
+                        enum_rust_ty.clone(),
+                        result,
+                        enum_ty.name().is_some(),
+                    );
+
+                    let variant_name = ctx.rust_ident(variant.name());
+
+                    // If it's an unnamed enum, or constification is enforced,
+                    // we also generate a constant so it can be properly
+                    // accessed.
+                    if (variation.is_rust() && enum_ty.name().is_none()) ||
+                        variant.force_constification()
+                    {
+                        let mangled_name = if is_toplevel {
+                            variant_name.clone()
+                        } else {
+                            let parent_name =
+                                parent_canonical_name.as_ref().unwrap();
+
+                            Ident::new(
+                                &format!("{}_{}", parent_name, variant_name),
+                                Span::call_site(),
+                            )
+                        };
+
+                        add_constant(
+                            ctx,
+                            enum_ty,
+                            &ident,
+                            &mangled_name,
+                            &variant_name,
+                            enum_rust_ty.clone(),
+                            result,
+                        );
+                    }
+
+                    entry.insert(variant_name);
+                }
+            }
+        }
+
+        let item = builder.build(ctx, enum_rust_ty, result);
+        result.push(item);
+    }
+}
+
+/// Enum for the default type of macro constants.
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum MacroTypeVariation {
+    /// Use i32 or i64
+    Signed,
+    /// Use u32 or u64
+    Unsigned,
+}
+
+impl fmt::Display for MacroTypeVariation {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = match self {
+            Self::Signed => "signed",
+            Self::Unsigned => "unsigned",
+        };
+        s.fmt(f)
+    }
+}
+
+impl Default for MacroTypeVariation {
+    fn default() -> MacroTypeVariation {
+        MacroTypeVariation::Unsigned
+    }
+}
+
+impl std::str::FromStr for MacroTypeVariation {
+    type Err = std::io::Error;
+
+    /// Create a `MacroTypeVariation` from a string.
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "signed" => Ok(MacroTypeVariation::Signed),
+            "unsigned" => Ok(MacroTypeVariation::Unsigned),
+            _ => Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                concat!(
+                    "Got an invalid MacroTypeVariation. Accepted values ",
+                    "are 'signed' and 'unsigned'"
+                ),
+            )),
+        }
+    }
+}
+
+/// Enum for how aliases should be translated.
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum AliasVariation {
+    /// Convert to regular Rust alias
+    TypeAlias,
+    /// Create a new type by wrapping the old type in a struct and using #[repr(transparent)]
+    NewType,
+    /// Same as NewStruct but also impl Deref to be able to use the methods of the wrapped type
+    NewTypeDeref,
+}
+
+impl fmt::Display for AliasVariation {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = match self {
+            Self::TypeAlias => "type_alias",
+            Self::NewType => "new_type",
+            Self::NewTypeDeref => "new_type_deref",
+        };
+
+        s.fmt(f)
+    }
+}
+
+impl Default for AliasVariation {
+    fn default() -> AliasVariation {
+        AliasVariation::TypeAlias
+    }
+}
+
+impl std::str::FromStr for AliasVariation {
+    type Err = std::io::Error;
+
+    /// Create an `AliasVariation` from a string.
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "type_alias" => Ok(AliasVariation::TypeAlias),
+            "new_type" => Ok(AliasVariation::NewType),
+            "new_type_deref" => Ok(AliasVariation::NewTypeDeref),
+            _ => Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                concat!(
+                    "Got an invalid AliasVariation. Accepted values ",
+                    "are 'type_alias', 'new_type', and 'new_type_deref'"
+                ),
+            )),
+        }
+    }
+}
+
+/// Enum for how non-`Copy` `union`s should be translated.
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum NonCopyUnionStyle {
+    /// Wrap members in a type generated by `bindgen`.
+    BindgenWrapper,
+    /// Wrap members in [`::core::mem::ManuallyDrop`].
+    ///
+    /// Note: `ManuallyDrop` was stabilized in Rust 1.20.0, do not use it if your
+    /// MSRV is lower.
+    ManuallyDrop,
+}
+
+impl fmt::Display for NonCopyUnionStyle {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = match self {
+            Self::BindgenWrapper => "bindgen_wrapper",
+            Self::ManuallyDrop => "manually_drop",
+        };
+
+        s.fmt(f)
+    }
+}
+
+impl Default for NonCopyUnionStyle {
+    fn default() -> Self {
+        Self::BindgenWrapper
+    }
+}
+
+impl std::str::FromStr for NonCopyUnionStyle {
+    type Err = std::io::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "bindgen_wrapper" => Ok(Self::BindgenWrapper),
+            "manually_drop" => Ok(Self::ManuallyDrop),
+            _ => Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                concat!(
+                    "Got an invalid NonCopyUnionStyle. Accepted values ",
+                    "are 'bindgen_wrapper' and 'manually_drop'"
+                ),
+            )),
+        }
+    }
+}
+
+/// Fallible conversion to an opaque blob.
+///
+/// Implementors of this trait should provide the `try_get_layout` method to
+/// fallibly get this thing's layout, which the provided `try_to_opaque` trait
+/// method will use to convert the `Layout` into an opaque blob Rust type.
+pub(crate) trait TryToOpaque {
+    type Extra;
+
+    /// Get the layout for this thing, if one is available.
+    fn try_get_layout(
+        &self,
+        ctx: &BindgenContext,
+        extra: &Self::Extra,
+    ) -> error::Result<Layout>;
+
+    /// Do not override this provided trait method.
+    fn try_to_opaque(
+        &self,
+        ctx: &BindgenContext,
+        extra: &Self::Extra,
+    ) -> error::Result<syn::Type> {
+        self.try_get_layout(ctx, extra)
+            .map(|layout| helpers::blob(ctx, layout))
+    }
+}
+
+/// Infallible conversion of an IR thing to an opaque blob.
+///
+/// The resulting layout is best effort, and is unfortunately not guaranteed to
+/// be correct. When all else fails, we fall back to a single byte layout as a
+/// last resort, because C++ does not permit zero-sized types. See the note in
+/// the `ToRustTyOrOpaque` doc comment about fallible versus infallible traits
+/// and when each is appropriate.
+///
+/// Don't implement this directly. Instead implement `TryToOpaque`, and then
+/// leverage the blanket impl for this trait.
+pub(crate) trait ToOpaque: TryToOpaque {
+    fn get_layout(&self, ctx: &BindgenContext, extra: &Self::Extra) -> Layout {
+        self.try_get_layout(ctx, extra)
+            .unwrap_or_else(|_| Layout::for_size(ctx, 1))
+    }
+
+    fn to_opaque(
+        &self,
+        ctx: &BindgenContext,
+        extra: &Self::Extra,
+    ) -> syn::Type {
+        let layout = self.get_layout(ctx, extra);
+        helpers::blob(ctx, layout)
+    }
+}
+
+impl<T> ToOpaque for T where T: TryToOpaque {}
+
+/// Fallible conversion from an IR thing to an *equivalent* Rust type.
+///
+/// If the C/C++ construct represented by the IR thing cannot (currently) be
+/// represented in Rust (for example, instantiations of templates with
+/// const-value generic parameters) then the impl should return an `Err`. It
+/// should *not* attempt to return an opaque blob with the correct size and
+/// alignment. That is the responsibility of the `TryToOpaque` trait.
+pub(crate) trait TryToRustTy {
+    type Extra;
+
+    fn try_to_rust_ty(
+        &self,
+        ctx: &BindgenContext,
+        extra: &Self::Extra,
+    ) -> error::Result<syn::Type>;
+}
+
+/// Fallible conversion to a Rust type or an opaque blob with the correct size
+/// and alignment.
+///
+/// Don't implement this directly. Instead implement `TryToRustTy` and
+/// `TryToOpaque`, and then leverage the blanket impl for this trait below.
+pub(crate) trait TryToRustTyOrOpaque: TryToRustTy + TryToOpaque {
+    type Extra;
+
+    fn try_to_rust_ty_or_opaque(
+        &self,
+        ctx: &BindgenContext,
+        extra: &<Self as TryToRustTyOrOpaque>::Extra,
+    ) -> error::Result<syn::Type>;
+}
+
+impl<E, T> TryToRustTyOrOpaque for T
+where
+    T: TryToRustTy<Extra = E> + TryToOpaque<Extra = E>,
+{
+    type Extra = E;
+
+    fn try_to_rust_ty_or_opaque(
+        &self,
+        ctx: &BindgenContext,
+        extra: &E,
+    ) -> error::Result<syn::Type> {
+        self.try_to_rust_ty(ctx, extra).or_else(|_| {
+            if let Ok(layout) = self.try_get_layout(ctx, extra) {
+                Ok(helpers::blob(ctx, layout))
+            } else {
+                Err(error::Error::NoLayoutForOpaqueBlob)
+            }
+        })
+    }
+}
+
+/// Infallible conversion to a Rust type, or an opaque blob with a best effort
+/// of correct size and alignment.
+///
+/// Don't implement this directly. Instead implement `TryToRustTy` and
+/// `TryToOpaque`, and then leverage the blanket impl for this trait below.
+///
+/// ### Fallible vs. Infallible Conversions to Rust Types
+///
+/// When should one use this infallible `ToRustTyOrOpaque` trait versus the
+/// fallible `TryTo{RustTy, Opaque, RustTyOrOpaque}` triats? All fallible trait
+/// implementations that need to convert another thing into a Rust type or
+/// opaque blob in a nested manner should also use fallible trait methods and
+/// propagate failure up the stack. Only infallible functions and methods like
+/// CodeGenerator implementations should use the infallible
+/// `ToRustTyOrOpaque`. The further out we push error recovery, the more likely
+/// we are to get a usable `Layout` even if we can't generate an equivalent Rust
+/// type for a C++ construct.
+pub(crate) trait ToRustTyOrOpaque: TryToRustTy + ToOpaque {
+    type Extra;
+
+    fn to_rust_ty_or_opaque(
+        &self,
+        ctx: &BindgenContext,
+        extra: &<Self as ToRustTyOrOpaque>::Extra,
+    ) -> syn::Type;
+}
+
+impl<E, T> ToRustTyOrOpaque for T
+where
+    T: TryToRustTy<Extra = E> + ToOpaque<Extra = E>,
+{
+    type Extra = E;
+
+    fn to_rust_ty_or_opaque(
+        &self,
+        ctx: &BindgenContext,
+        extra: &E,
+    ) -> syn::Type {
+        self.try_to_rust_ty(ctx, extra)
+            .unwrap_or_else(|_| self.to_opaque(ctx, extra))
+    }
+}
+
+impl<T> TryToOpaque for T
+where
+    T: Copy + Into<ItemId>,
+{
+    type Extra = ();
+
+    fn try_get_layout(
+        &self,
+        ctx: &BindgenContext,
+        _: &(),
+    ) -> error::Result<Layout> {
+        ctx.resolve_item((*self).into()).try_get_layout(ctx, &())
+    }
+}
+
+impl<T> TryToRustTy for T
+where
+    T: Copy + Into<ItemId>,
+{
+    type Extra = ();
+
+    fn try_to_rust_ty(
+        &self,
+        ctx: &BindgenContext,
+        _: &(),
+    ) -> error::Result<syn::Type> {
+        ctx.resolve_item((*self).into()).try_to_rust_ty(ctx, &())
+    }
+}
+
+impl TryToOpaque for Item {
+    type Extra = ();
+
+    fn try_get_layout(
+        &self,
+        ctx: &BindgenContext,
+        _: &(),
+    ) -> error::Result<Layout> {
+        self.kind().expect_type().try_get_layout(ctx, self)
+    }
+}
+
+impl TryToRustTy for Item {
+    type Extra = ();
+
+    fn try_to_rust_ty(
+        &self,
+        ctx: &BindgenContext,
+        _: &(),
+    ) -> error::Result<syn::Type> {
+        self.kind().expect_type().try_to_rust_ty(ctx, self)
+    }
+}
+
+impl TryToOpaque for Type {
+    type Extra = Item;
+
+    fn try_get_layout(
+        &self,
+        ctx: &BindgenContext,
+        _: &Item,
+    ) -> error::Result<Layout> {
+        self.layout(ctx).ok_or(error::Error::NoLayoutForOpaqueBlob)
+    }
+}
+
+impl TryToRustTy for Type {
+    type Extra = Item;
+
+    fn try_to_rust_ty(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> error::Result<syn::Type> {
+        use self::helpers::ast_ty::*;
+
+        match *self.kind() {
+            TypeKind::Void => Ok(c_void(ctx)),
+            // TODO: we should do something smart with nullptr, or maybe *const
+            // c_void is enough?
+            TypeKind::NullPtr => Ok(c_void(ctx).to_ptr(true)),
+            TypeKind::Int(ik) => {
+                Ok(int_kind_rust_type(ctx, ik, self.layout(ctx)))
+            }
+            TypeKind::Float(fk) => {
+                Ok(float_kind_rust_type(ctx, fk, self.layout(ctx)))
+            }
+            TypeKind::Complex(fk) => {
+                let float_path =
+                    float_kind_rust_type(ctx, fk, self.layout(ctx));
+
+                ctx.generated_bindgen_complex();
+                Ok(if ctx.options().enable_cxx_namespaces {
+                    syn::parse_quote! { root::__BindgenComplex<#float_path> }
+                } else {
+                    syn::parse_quote! { __BindgenComplex<#float_path> }
+                })
+            }
+            TypeKind::Function(ref signature) => {
+                // We can't rely on the sizeof(Option<NonZero<_>>) ==
+                // sizeof(NonZero<_>) optimization with opaque blobs (because
+                // they aren't NonZero), so don't *ever* use an or_opaque
+                // variant here.
+                let ty = signature.try_to_rust_ty(ctx, item)?;
+
+                let prefix = ctx.trait_prefix();
+                Ok(syn::parse_quote! { ::#prefix::option::Option<#ty> })
+            }
+            TypeKind::Array(item, len) | TypeKind::Vector(item, len) => {
+                let ty = item.try_to_rust_ty(ctx, &())?;
+                Ok(syn::parse_quote! { [ #ty ; #len ] })
+            }
+            TypeKind::Enum(..) => {
+                let path = item.namespace_aware_canonical_path(ctx);
+                let path = proc_macro2::TokenStream::from_str(&path.join("::"))
+                    .unwrap();
+                Ok(syn::parse_quote!(#path))
+            }
+            TypeKind::TemplateInstantiation(ref inst) => {
+                inst.try_to_rust_ty(ctx, item)
+            }
+            TypeKind::ResolvedTypeRef(inner) => inner.try_to_rust_ty(ctx, &()),
+            TypeKind::TemplateAlias(..) |
+            TypeKind::Alias(..) |
+            TypeKind::BlockPointer(..) => {
+                if self.is_block_pointer() && !ctx.options().generate_block {
+                    let void = c_void(ctx);
+                    return Ok(void.to_ptr(/* is_const = */ false));
+                }
+
+                if item.is_opaque(ctx, &()) &&
+                    item.used_template_params(ctx)
+                        .into_iter()
+                        .any(|param| param.is_template_param(ctx, &()))
+                {
+                    self.try_to_opaque(ctx, item)
+                } else if let Some(ty) = self
+                    .name()
+                    .and_then(|name| utils::type_from_named(ctx, name))
+                {
+                    Ok(ty)
+                } else {
+                    utils::build_path(item, ctx)
+                }
+            }
+            TypeKind::Comp(ref info) => {
+                let template_params = item.all_template_params(ctx);
+                if info.has_non_type_template_params() ||
+                    (item.is_opaque(ctx, &()) && !template_params.is_empty())
+                {
+                    return self.try_to_opaque(ctx, item);
+                }
+
+                utils::build_path(item, ctx)
+            }
+            TypeKind::Opaque => self.try_to_opaque(ctx, item),
+            TypeKind::Pointer(inner) | TypeKind::Reference(inner) => {
+                // Check that this type has the same size as the target's pointer type.
+                let size = self.get_layout(ctx, item).size;
+                if size != ctx.target_pointer_size() {
+                    return Err(Error::InvalidPointerSize {
+                        ty_name: self.name().unwrap_or("unknown").into(),
+                        ty_size: size,
+                        ptr_size: ctx.target_pointer_size(),
+                    });
+                }
+
+                let is_const = ctx.resolve_type(inner).is_const();
+
+                let inner =
+                    inner.into_resolver().through_type_refs().resolve(ctx);
+                let inner_ty = inner.expect_type();
+
+                let is_objc_pointer =
+                    matches!(inner_ty.kind(), TypeKind::ObjCInterface(..));
+
+                // Regardless if we can properly represent the inner type, we
+                // should always generate a proper pointer here, so use
+                // infallible conversion of the inner type.
+                let ty = inner
+                    .to_rust_ty_or_opaque(ctx, &())
+                    .with_implicit_template_params(ctx, inner);
+
+                // Avoid the first function pointer level, since it's already
+                // represented in Rust.
+                if inner_ty.canonical_type(ctx).is_function() || is_objc_pointer
+                {
+                    Ok(ty)
+                } else {
+                    Ok(ty.to_ptr(is_const))
+                }
+            }
+            TypeKind::TypeParam => {
+                let name = item.canonical_name(ctx);
+                let ident = ctx.rust_ident(name);
+                Ok(syn::parse_quote! { #ident })
+            }
+            TypeKind::ObjCSel => Ok(syn::parse_quote! { objc::runtime::Sel }),
+            TypeKind::ObjCId => Ok(syn::parse_quote! { id }),
+            TypeKind::ObjCInterface(ref interface) => {
+                let name = ctx.rust_ident(interface.name());
+                Ok(syn::parse_quote! { #name })
+            }
+            ref u @ TypeKind::UnresolvedTypeRef(..) => {
+                unreachable!("Should have been resolved after parsing {:?}!", u)
+            }
+        }
+    }
+}
+
+impl TryToOpaque for TemplateInstantiation {
+    type Extra = Item;
+
+    fn try_get_layout(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> error::Result<Layout> {
+        item.expect_type()
+            .layout(ctx)
+            .ok_or(error::Error::NoLayoutForOpaqueBlob)
+    }
+}
+
+impl TryToRustTy for TemplateInstantiation {
+    type Extra = Item;
+
+    fn try_to_rust_ty(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> error::Result<syn::Type> {
+        if self.is_opaque(ctx, item) {
+            return Err(error::Error::InstantiationOfOpaqueType);
+        }
+
+        let def = self
+            .template_definition()
+            .into_resolver()
+            .through_type_refs()
+            .resolve(ctx);
+
+        let mut ty = quote! {};
+        let def_path = def.namespace_aware_canonical_path(ctx);
+        ty.append_separated(
+            def_path.into_iter().map(|p| ctx.rust_ident(p)),
+            quote!(::),
+        );
+
+        let def_params = def.self_template_params(ctx);
+        if def_params.is_empty() {
+            // This can happen if we generated an opaque type for a partial
+            // template specialization, and we've hit an instantiation of
+            // that partial specialization.
+            extra_assert!(def.is_opaque(ctx, &()));
+            return Err(error::Error::InstantiationOfOpaqueType);
+        }
+
+        // TODO: If the definition type is a template class/struct
+        // definition's member template definition, it could rely on
+        // generic template parameters from its outer template
+        // class/struct. When we emit bindings for it, it could require
+        // *more* type arguments than we have here, and we will need to
+        // reconstruct them somehow. We don't have any means of doing
+        // that reconstruction at this time.
+
+        let template_args = self
+            .template_arguments()
+            .iter()
+            .zip(def_params.iter())
+            // Only pass type arguments for the type parameters that
+            // the def uses.
+            .filter(|&(_, param)| ctx.uses_template_parameter(def.id(), *param))
+            .map(|(arg, _)| {
+                let arg = arg.into_resolver().through_type_refs().resolve(ctx);
+                let ty = arg
+                    .try_to_rust_ty(ctx, &())?
+                    .with_implicit_template_params(ctx, arg);
+                Ok(ty)
+            })
+            .collect::<error::Result<Vec<_>>>()?;
+
+        Ok(if template_args.is_empty() {
+            syn::parse_quote! { #ty }
+        } else {
+            syn::parse_quote! { #ty<#(#template_args),*> }
+        })
+    }
+}
+
+impl TryToRustTy for FunctionSig {
+    type Extra = Item;
+
+    fn try_to_rust_ty(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> error::Result<syn::Type> {
+        // TODO: we might want to consider ignoring the reference return value.
+        let ret = utils::fnsig_return_ty(ctx, self);
+        let arguments = utils::fnsig_arguments(ctx, self);
+
+        match self.abi(ctx, None) {
+            Ok(abi) => Ok(
+                syn::parse_quote! { unsafe extern #abi fn ( #( #arguments ),* ) #ret },
+            ),
+            Err(err) => {
+                if matches!(err, error::Error::UnsupportedAbi(_)) {
+                    unsupported_abi_diagnostic(
+                        self.name(),
+                        self.is_variadic(),
+                        item.location(),
+                        ctx,
+                        &err,
+                    );
+                }
+
+                Err(err)
+            }
+        }
+    }
+}
+
+impl CodeGenerator for Function {
+    type Extra = Item;
+
+    /// If we've actually generated the symbol, the number of times we've seen
+    /// it.
+    type Return = Option<u32>;
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) -> Self::Return {
+        debug!("<Function as CodeGenerator>::codegen: item = {:?}", item);
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+
+        let is_internal = matches!(self.linkage(), Linkage::Internal);
+
+        let signature_item = ctx.resolve_item(self.signature());
+        let signature = signature_item.kind().expect_type().canonical_type(ctx);
+        let signature = match *signature.kind() {
+            TypeKind::Function(ref sig) => sig,
+            _ => panic!("Signature kind is not a Function: {:?}", signature),
+        };
+
+        if is_internal {
+            if !ctx.options().wrap_static_fns {
+                // We cannot do anything with internal functions if we are not wrapping them so
+                // just avoid generating anything for them.
+                return None;
+            }
+
+            if signature.is_variadic() {
+                // We cannot generate wrappers for variadic static functions so we avoid
+                // generating any code for them.
+                variadic_fn_diagnostic(self.name(), item.location(), ctx);
+                return None;
+            }
+        }
+
+        // Pure virtual methods have no actual symbol, so we can't generate
+        // something meaningful for them.
+        let is_dynamic_function = match self.kind() {
+            FunctionKind::Method(ref method_kind)
+                if method_kind.is_pure_virtual() =>
+            {
+                return None;
+            }
+            FunctionKind::Function => {
+                ctx.options().dynamic_library_name.is_some()
+            }
+            _ => false,
+        };
+
+        // Similar to static member variables in a class template, we can't
+        // generate bindings to template functions, because the set of
+        // instantiations is open ended and we have no way of knowing which
+        // monomorphizations actually exist.
+        if !item.all_template_params(ctx).is_empty() {
+            return None;
+        }
+
+        let name = self.name();
+        let mut canonical_name = item.canonical_name(ctx);
+        let mangled_name = self.mangled_name();
+
+        {
+            let seen_symbol_name = mangled_name.unwrap_or(&canonical_name);
+
+            // TODO: Maybe warn here if there's a type/argument mismatch, or
+            // something?
+            if result.seen_function(seen_symbol_name) {
+                return None;
+            }
+            result.saw_function(seen_symbol_name);
+        }
+
+        let mut attributes = vec![];
+
+        if ctx.options().rust_features().must_use_function {
+            let must_use = signature.must_use() || {
+                let ret_ty = signature
+                    .return_type()
+                    .into_resolver()
+                    .through_type_refs()
+                    .resolve(ctx);
+                ret_ty.must_use(ctx)
+            };
+
+            if must_use {
+                attributes.push(attributes::must_use());
+            }
+        }
+
+        if let Some(comment) = item.comment(ctx) {
+            attributes.push(attributes::doc(comment));
+        }
+
+        let abi = match signature.abi(ctx, Some(name)) {
+            Err(err) => {
+                if matches!(err, error::Error::UnsupportedAbi(_)) {
+                    unsupported_abi_diagnostic(
+                        name,
+                        signature.is_variadic(),
+                        item.location(),
+                        ctx,
+                        &err,
+                    );
+                }
+
+                return None;
+            }
+            Ok(ClangAbi::Unknown(unknown_abi)) => {
+                panic!(
+                    "Invalid or unknown abi {:?} for function {:?} ({:?})",
+                    unknown_abi, canonical_name, self
+                );
+            }
+            Ok(abi) => abi,
+        };
+
+        // Handle overloaded functions by giving each overload its own unique
+        // suffix.
+        let times_seen = result.overload_number(&canonical_name);
+        if times_seen > 0 {
+            write!(&mut canonical_name, "{}", times_seen).unwrap();
+        }
+
+        let mut has_link_name_attr = false;
+        if let Some(link_name) = self.link_name() {
+            attributes.push(attributes::link_name::<false>(link_name));
+            has_link_name_attr = true;
+        } else {
+            let link_name = mangled_name.unwrap_or(name);
+            if !is_dynamic_function &&
+                !utils::names_will_be_identical_after_mangling(
+                    &canonical_name,
+                    link_name,
+                    Some(abi),
+                )
+            {
+                attributes.push(attributes::link_name::<false>(link_name));
+                has_link_name_attr = true;
+            }
+        }
+
+        // Unfortunately this can't piggyback on the `attributes` list because
+        // the #[link(wasm_import_module)] needs to happen before the `extern
+        // "C"` block. It doesn't get picked up properly otherwise
+        let wasm_link_attribute =
+            ctx.options().wasm_import_module_name.as_ref().map(|name| {
+                quote! { #[link(wasm_import_module = #name)] }
+            });
+
+        let should_wrap =
+            is_internal && ctx.options().wrap_static_fns && !has_link_name_attr;
+
+        if should_wrap {
+            let name = canonical_name.clone() + ctx.wrap_static_fns_suffix();
+            attributes.push(attributes::link_name::<true>(&name));
+        }
+
+        let wrap_as_variadic = if should_wrap && !signature.is_variadic() {
+            utils::wrap_as_variadic_fn(ctx, signature, name)
+        } else {
+            None
+        };
+
+        let (ident, args) = if let Some(WrapAsVariadic {
+            idx_of_va_list_arg,
+            new_name,
+        }) = &wrap_as_variadic
+        {
+            (
+                new_name,
+                utils::fnsig_arguments_iter(
+                    ctx,
+                    // Prune argument at index (idx_of_va_list_arg)
+                    signature.argument_types().iter().enumerate().filter_map(
+                        |(idx, t)| {
+                            if idx == *idx_of_va_list_arg {
+                                None
+                            } else {
+                                Some(t)
+                            }
+                        },
+                    ),
+                    // and replace it by a `...` (variadic symbol and the end of the signature)
+                    true,
+                ),
+            )
+        } else {
+            (&canonical_name, utils::fnsig_arguments(ctx, signature))
+        };
+        let ret = utils::fnsig_return_ty(ctx, signature);
+
+        let ident = ctx.rust_ident(ident);
+        let tokens = quote! {
+            #wasm_link_attribute
+            extern #abi {
+                #(#attributes)*
+                pub fn #ident ( #( #args ),* ) #ret;
+            }
+        };
+
+        // Add the item to the serialization list if necessary
+        if should_wrap {
+            result
+                .items_to_serialize
+                .push((item.id(), wrap_as_variadic));
+        }
+
+        // If we're doing dynamic binding generation, add to the dynamic items.
+        if is_dynamic_function {
+            let args_identifiers =
+                utils::fnsig_argument_identifiers(ctx, signature);
+            let ret_ty = utils::fnsig_return_ty(ctx, signature);
+            result.dynamic_items().push(
+                ident,
+                abi,
+                signature.is_variadic(),
+                ctx.options().dynamic_link_require_all,
+                args,
+                args_identifiers,
+                ret,
+                ret_ty,
+                attributes,
+                ctx,
+            );
+        } else {
+            result.push(tokens);
+        }
+        Some(times_seen)
+    }
+}
+
+#[cfg_attr(not(feature = "experimental"), allow(unused_variables))]
+fn unsupported_abi_diagnostic(
+    fn_name: &str,
+    variadic: bool,
+    location: Option<&crate::clang::SourceLocation>,
+    ctx: &BindgenContext,
+    error: &error::Error,
+) {
+    warn!(
+        "Skipping {}function `{}` because the {}",
+        if variadic { "variadic " } else { "" },
+        fn_name,
+        error
+    );
+
+    #[cfg(feature = "experimental")]
+    if ctx.options().emit_diagnostics {
+        use crate::diagnostics::{get_line, Diagnostic, Level, Slice};
+
+        let mut diag = Diagnostic::default();
+        diag.with_title(
+            format!(
+                "Skipping {}function `{}` because the {}",
+                if variadic { "variadic " } else { "" },
+                fn_name,
+                error
+            ),
+            Level::Warn,
+        )
+        .add_annotation(
+            "No code will be generated for this function.",
+            Level::Warn,
+        )
+        .add_annotation(
+            format!(
+                "The configured Rust version is {}.",
+                ctx.options().rust_target
+            ),
+            Level::Note,
+        );
+
+        if let Some(loc) = location {
+            let (file, line, col, _) = loc.location();
+
+            if let Some(filename) = file.name() {
+                if let Ok(Some(source)) = get_line(&filename, line) {
+                    let mut slice = Slice::default();
+                    slice
+                        .with_source(source)
+                        .with_location(filename, line, col);
+                    diag.add_slice(slice);
+                }
+            }
+        }
+
+        diag.display()
+    }
+}
+
+fn variadic_fn_diagnostic(
+    fn_name: &str,
+    _location: Option<&crate::clang::SourceLocation>,
+    _ctx: &BindgenContext,
+) {
+    warn!(
+        "Cannot generate wrapper for the static variadic function `{}`.",
+        fn_name,
+    );
+
+    #[cfg(feature = "experimental")]
+    if _ctx.options().emit_diagnostics {
+        use crate::diagnostics::{get_line, Diagnostic, Level, Slice};
+
+        let mut diag = Diagnostic::default();
+
+        diag.with_title(format!("Cannot generate wrapper for the static function `{}`.", fn_name), Level::Warn)
+            .add_annotation("The `--wrap-static-fns` feature does not support variadic functions.", Level::Note)
+            .add_annotation("No code will be generated for this function.", Level::Note);
+
+        if let Some(loc) = _location {
+            let (file, line, col, _) = loc.location();
+
+            if let Some(filename) = file.name() {
+                if let Ok(Some(source)) = get_line(&filename, line) {
+                    let mut slice = Slice::default();
+                    slice
+                        .with_source(source)
+                        .with_location(filename, line, col);
+                    diag.add_slice(slice);
+                }
+            }
+        }
+
+        diag.display()
+    }
+}
+
+fn objc_method_codegen(
+    ctx: &BindgenContext,
+    method: &ObjCMethod,
+    methods: &mut Vec<proc_macro2::TokenStream>,
+    class_name: Option<&str>,
+    rust_class_name: &str,
+    prefix: &str,
+) {
+    // This would ideally resolve the method into an Item, and use
+    // Item::process_before_codegen; however, ObjC methods are not currently
+    // made into function items.
+    let name = format!("{}::{}{}", rust_class_name, prefix, method.rust_name());
+    if ctx.options().blocklisted_items.matches(name) {
+        return;
+    }
+
+    let signature = method.signature();
+    let fn_args = utils::fnsig_arguments(ctx, signature);
+    let fn_ret = utils::fnsig_return_ty(ctx, signature);
+
+    let sig = if method.is_class_method() {
+        quote! {
+            ( #( #fn_args ),* ) #fn_ret
+        }
+    } else {
+        let self_arr = [quote! { &self }];
+        let args = self_arr.iter().chain(fn_args.iter());
+        quote! {
+            ( #( #args ),* ) #fn_ret
+        }
+    };
+
+    let methods_and_args = method.format_method_call(&fn_args);
+
+    let body = {
+        let body = if method.is_class_method() {
+            let class_name = ctx.rust_ident(
+                class_name
+                    .expect("Generating a class method without class name?"),
+            );
+            quote!(msg_send!(class!(#class_name), #methods_and_args))
+        } else {
+            quote!(msg_send!(*self, #methods_and_args))
+        };
+
+        ctx.wrap_unsafe_ops(body)
+    };
+
+    let method_name =
+        ctx.rust_ident(format!("{}{}", prefix, method.rust_name()));
+
+    methods.push(quote! {
+        unsafe fn #method_name #sig where <Self as std::ops::Deref>::Target: objc::Message + Sized {
+            #body
+        }
+    });
+}
+
+impl CodeGenerator for ObjCInterface {
+    type Extra = Item;
+    type Return = ();
+
+    fn codegen(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut CodegenResult<'_>,
+        item: &Item,
+    ) {
+        debug_assert!(item.is_enabled_for_codegen(ctx));
+
+        let mut impl_items = vec![];
+        let rust_class_name = item.path_for_allowlisting(ctx)[1..].join("::");
+
+        for method in self.methods() {
+            objc_method_codegen(
+                ctx,
+                method,
+                &mut impl_items,
+                None,
+                &rust_class_name,
+                "",
+            );
+        }
+
+        for class_method in self.class_methods() {
+            let ambiquity = self
+                .methods()
+                .iter()
+                .map(|m| m.rust_name())
+                .any(|x| x == class_method.rust_name());
+            let prefix = if ambiquity { "class_" } else { "" };
+            objc_method_codegen(
+                ctx,
+                class_method,
+                &mut impl_items,
+                Some(self.name()),
+                &rust_class_name,
+                prefix,
+            );
+        }
+
+        let trait_name = ctx.rust_ident(self.rust_name());
+        let trait_constraints = quote! {
+            Sized + std::ops::Deref
+        };
+        let trait_block = if self.is_template() {
+            let template_names: Vec<Ident> = self
+                .template_names
+                .iter()
+                .map(|g| ctx.rust_ident(g))
+                .collect();
+
+            quote! {
+                pub trait #trait_name <#(#template_names:'static),*> : #trait_constraints {
+                    #( #impl_items )*
+                }
+            }
+        } else {
+            quote! {
+                pub trait #trait_name : #trait_constraints {
+                    #( #impl_items )*
+                }
+            }
+        };
+
+        let class_name = ctx.rust_ident(self.name());
+        if !self.is_category() && !self.is_protocol() {
+            let struct_block = quote! {
+                #[repr(transparent)]
+                #[derive(Debug, Copy, Clone)]
+                pub struct #class_name(pub id);
+                impl std::ops::Deref for #class_name {
+                    type Target = objc::runtime::Object;
+                    fn deref(&self) -> &Self::Target {
+                        unsafe {
+                            &*self.0
+                        }
+                    }
+                }
+                unsafe impl objc::Message for #class_name { }
+                impl #class_name {
+                    pub fn alloc() -> Self {
+                        Self(unsafe {
+                            msg_send!(class!(#class_name), alloc)
+                        })
+                    }
+                }
+            };
+            result.push(struct_block);
+            let mut protocol_set: HashSet<ItemId> = Default::default();
+            for protocol_id in self.conforms_to.iter() {
+                protocol_set.insert(*protocol_id);
+                let protocol_name = ctx.rust_ident(
+                    ctx.resolve_type(protocol_id.expect_type_id(ctx))
+                        .name()
+                        .unwrap(),
+                );
+                let impl_trait = quote! {
+                    impl #protocol_name for #class_name { }
+                };
+                result.push(impl_trait);
+            }
+            let mut parent_class = self.parent_class;
+            while let Some(parent_id) = parent_class {
+                let parent = parent_id
+                    .expect_type_id(ctx)
+                    .into_resolver()
+                    .through_type_refs()
+                    .resolve(ctx)
+                    .expect_type()
+                    .kind();
+
+                let parent = match parent {
+                    TypeKind::ObjCInterface(ref parent) => parent,
+                    _ => break,
+                };
+                parent_class = parent.parent_class;
+
+                let parent_name = ctx.rust_ident(parent.rust_name());
+                let impl_trait = if parent.is_template() {
+                    let template_names: Vec<Ident> = parent
+                        .template_names
+                        .iter()
+                        .map(|g| ctx.rust_ident(g))
+                        .collect();
+                    quote! {
+                        impl <#(#template_names :'static),*> #parent_name <#(#template_names),*> for #class_name {
+                        }
+                    }
+                } else {
+                    quote! {
+                        impl #parent_name for #class_name { }
+                    }
+                };
+                result.push(impl_trait);
+                for protocol_id in parent.conforms_to.iter() {
+                    if protocol_set.insert(*protocol_id) {
+                        let protocol_name = ctx.rust_ident(
+                            ctx.resolve_type(protocol_id.expect_type_id(ctx))
+                                .name()
+                                .unwrap(),
+                        );
+                        let impl_trait = quote! {
+                            impl #protocol_name for #class_name { }
+                        };
+                        result.push(impl_trait);
+                    }
+                }
+                if !parent.is_template() {
+                    let parent_struct_name = parent.name();
+                    let child_struct_name = self.name();
+                    let parent_struct = ctx.rust_ident(parent_struct_name);
+                    let from_block = quote! {
+                        impl From<#class_name> for #parent_struct {
+                            fn from(child: #class_name) -> #parent_struct {
+                                #parent_struct(child.0)
+                            }
+                        }
+                    };
+                    result.push(from_block);
+
+                    let error_msg = format!(
+                        "This {} cannot be downcasted to {}",
+                        parent_struct_name, child_struct_name
+                    );
+                    let try_into_block = quote! {
+                        impl std::convert::TryFrom<#parent_struct> for #class_name {
+                            type Error = &'static str;
+                            fn try_from(parent: #parent_struct) -> Result<#class_name, Self::Error> {
+                                let is_kind_of : bool = unsafe { msg_send!(parent, isKindOfClass:class!(#class_name))};
+                                if is_kind_of {
+                                    Ok(#class_name(parent.0))
+                                } else {
+                                    Err(#error_msg)
+                                }
+                            }
+                        }
+                    };
+                    result.push(try_into_block);
+                }
+            }
+        }
+
+        if !self.is_protocol() {
+            let impl_block = if self.is_template() {
+                let template_names: Vec<Ident> = self
+                    .template_names
+                    .iter()
+                    .map(|g| ctx.rust_ident(g))
+                    .collect();
+                quote! {
+                    impl <#(#template_names :'static),*> #trait_name <#(#template_names),*> for #class_name {
+                    }
+                }
+            } else {
+                quote! {
+                    impl #trait_name for #class_name {
+                    }
+                }
+            };
+            result.push(impl_block);
+        }
+
+        result.push(trait_block);
+        result.saw_objc();
+    }
+}
+
+pub(crate) fn codegen(
+    context: BindgenContext,
+) -> Result<(proc_macro2::TokenStream, BindgenOptions), CodegenError> {
+    context.gen(|context| {
+        let _t = context.timer("codegen");
+        let counter = Cell::new(0);
+        let mut result = CodegenResult::new(&counter);
+
+        debug!("codegen: {:?}", context.options());
+
+        if context.options().emit_ir {
+            let codegen_items = context.codegen_items();
+            for (id, item) in context.items() {
+                if codegen_items.contains(&id) {
+                    println!("ir: {:?} = {:#?}", id, item);
+                }
+            }
+        }
+
+        if let Some(path) = context.options().emit_ir_graphviz.as_ref() {
+            match dot::write_dot_file(context, path) {
+                Ok(()) => info!(
+                    "Your dot file was generated successfully into: {}",
+                    path
+                ),
+                Err(e) => warn!("{}", e),
+            }
+        }
+
+        if let Some(spec) = context.options().depfile.as_ref() {
+            match spec.write(context.deps()) {
+                Ok(()) => info!(
+                    "Your depfile was generated successfully into: {}",
+                    spec.depfile_path.display()
+                ),
+                Err(e) => warn!("{}", e),
+            }
+        }
+
+        context.resolve_item(context.root_module()).codegen(
+            context,
+            &mut result,
+            &(),
+        );
+
+        if let Some(ref lib_name) = context.options().dynamic_library_name {
+            let lib_ident = context.rust_ident(lib_name);
+            let dynamic_items_tokens =
+                result.dynamic_items().get_tokens(lib_ident, context);
+            result.push(dynamic_items_tokens);
+        }
+
+        utils::serialize_items(&result, context)?;
+
+        Ok(postprocessing::postprocessing(
+            result.items,
+            context.options(),
+        ))
+    })
+}
+
+pub(crate) mod utils {
+    use super::serialize::CSerialize;
+    use super::{error, CodegenError, CodegenResult, ToRustTyOrOpaque};
+    use crate::ir::context::BindgenContext;
+    use crate::ir::context::TypeId;
+    use crate::ir::function::{Abi, ClangAbi, FunctionSig};
+    use crate::ir::item::{Item, ItemCanonicalPath};
+    use crate::ir::ty::TypeKind;
+    use crate::{args_are_cpp, file_is_cpp};
+    use std::borrow::Cow;
+    use std::io::Write;
+    use std::mem;
+    use std::path::PathBuf;
+    use std::str::FromStr;
+
+    pub(super) fn serialize_items(
+        result: &CodegenResult,
+        context: &BindgenContext,
+    ) -> Result<(), CodegenError> {
+        if result.items_to_serialize.is_empty() {
+            return Ok(());
+        }
+
+        let path = context
+            .options()
+            .wrap_static_fns_path
+            .as_ref()
+            .map(PathBuf::from)
+            .unwrap_or_else(|| {
+                std::env::temp_dir().join("bindgen").join("extern")
+            });
+
+        let dir = path.parent().unwrap();
+
+        if !dir.exists() {
+            std::fs::create_dir_all(dir)?;
+        }
+
+        let is_cpp = args_are_cpp(&context.options().clang_args) ||
+            context
+                .options()
+                .input_headers
+                .iter()
+                .any(|h| file_is_cpp(h));
+
+        let source_path = path.with_extension(if is_cpp { "cpp" } else { "c" });
+
+        let mut code = Vec::new();
+
+        if !context.options().input_headers.is_empty() {
+            for header in &context.options().input_headers {
+                writeln!(code, "#include \"{}\"", header)?;
+            }
+
+            writeln!(code)?;
+        }
+
+        if !context.options().input_header_contents.is_empty() {
+            for (name, contents) in &context.options().input_header_contents {
+                writeln!(code, "// {}\n{}", name, contents)?;
+            }
+
+            writeln!(code)?;
+        }
+
+        writeln!(code, "// Static wrappers\n")?;
+
+        for (id, wrap_as_variadic) in &result.items_to_serialize {
+            let item = context.resolve_item(*id);
+            item.serialize(context, wrap_as_variadic, &mut vec![], &mut code)?;
+        }
+
+        std::fs::write(source_path, code)?;
+
+        Ok(())
+    }
+
+    pub(super) fn wrap_as_variadic_fn(
+        ctx: &BindgenContext,
+        signature: &FunctionSig,
+        name: &str,
+    ) -> Option<super::WrapAsVariadic> {
+        // Fast path, exclude because:
+        //  - with 0 args: no va_list possible, so no point searching for one
+        //  - with 1 args: cannot have a `va_list` and another arg (required by va_start)
+        if signature.argument_types().len() <= 1 {
+            return None;
+        }
+
+        let mut it = signature.argument_types().iter().enumerate().filter_map(
+            |(idx, (_name, mut type_id))| {
+                // Hand rolled visitor that checks for the presence of `va_list`
+                loop {
+                    let ty = ctx.resolve_type(type_id);
+                    if Some("__builtin_va_list") == ty.name() {
+                        return Some(idx);
+                    }
+                    match ty.kind() {
+                        TypeKind::Alias(type_id_alias) => {
+                            type_id = *type_id_alias
+                        }
+                        TypeKind::ResolvedTypeRef(type_id_typedef) => {
+                            type_id = *type_id_typedef
+                        }
+                        _ => break,
+                    }
+                }
+                None
+            },
+        );
+
+        // Return THE idx (by checking that there is no idx after)
+        // This is done since we cannot handle multiple `va_list`
+        it.next().filter(|_| it.next().is_none()).and_then(|idx| {
+            // Call the `wrap_as_variadic_fn` callback
+            #[cfg(feature = "experimental")]
+            {
+                ctx.options()
+                    .last_callback(|c| c.wrap_as_variadic_fn(name))
+                    .map(|new_name| super::WrapAsVariadic {
+                        new_name,
+                        idx_of_va_list_arg: idx,
+                    })
+            }
+            #[cfg(not(feature = "experimental"))]
+            {
+                let _ = name;
+                let _ = idx;
+                None
+            }
+        })
+    }
+
+    pub(crate) fn prepend_bitfield_unit_type(
+        ctx: &BindgenContext,
+        result: &mut Vec<proc_macro2::TokenStream>,
+    ) {
+        let bitfield_unit_src = include_str!("./bitfield_unit.rs");
+        let bitfield_unit_src = if ctx.options().rust_features().min_const_fn {
+            Cow::Borrowed(bitfield_unit_src)
+        } else {
+            Cow::Owned(bitfield_unit_src.replace("const fn ", "fn "))
+        };
+        let bitfield_unit_type =
+            proc_macro2::TokenStream::from_str(&bitfield_unit_src).unwrap();
+        let bitfield_unit_type = quote!(#bitfield_unit_type);
+
+        let items = vec![bitfield_unit_type];
+        let old_items = mem::replace(result, items);
+        result.extend(old_items);
+    }
+
+    pub(crate) fn prepend_objc_header(
+        ctx: &BindgenContext,
+        result: &mut Vec<proc_macro2::TokenStream>,
+    ) {
+        let use_objc = if ctx.options().objc_extern_crate {
+            quote! {
+                #[macro_use]
+                extern crate objc;
+            }
+        } else {
+            quote! {
+                use objc::{self, msg_send, sel, sel_impl, class};
+            }
+        };
+
+        let id_type = quote! {
+            #[allow(non_camel_case_types)]
+            pub type id = *mut objc::runtime::Object;
+        };
+
+        let items = vec![use_objc, id_type];
+        let old_items = mem::replace(result, items);
+        result.extend(old_items);
+    }
+
+    pub(crate) fn prepend_block_header(
+        ctx: &BindgenContext,
+        result: &mut Vec<proc_macro2::TokenStream>,
+    ) {
+        let use_block = if ctx.options().block_extern_crate {
+            quote! {
+                extern crate block;
+            }
+        } else {
+            quote! {
+                use block;
+            }
+        };
+
+        let items = vec![use_block];
+        let old_items = mem::replace(result, items);
+        result.extend(old_items);
+    }
+
+    pub(crate) fn prepend_union_types(
+        ctx: &BindgenContext,
+        result: &mut Vec<proc_macro2::TokenStream>,
+    ) {
+        let prefix = ctx.trait_prefix();
+
+        // If the target supports `const fn`, declare eligible functions
+        // as `const fn` else just `fn`.
+        let const_fn = if ctx.options().rust_features().min_const_fn {
+            quote! { const fn }
+        } else {
+            quote! { fn }
+        };
+
+        // TODO(emilio): The fmt::Debug impl could be way nicer with
+        // std::intrinsics::type_name, but...
+        let union_field_decl = quote! {
+            #[repr(C)]
+            pub struct __BindgenUnionField<T>(::#prefix::marker::PhantomData<T>);
+        };
+
+        let transmute =
+            ctx.wrap_unsafe_ops(quote!(::#prefix::mem::transmute(self)));
+
+        let union_field_impl = quote! {
+            impl<T> __BindgenUnionField<T> {
+                #[inline]
+                pub #const_fn new() -> Self {
+                    __BindgenUnionField(::#prefix::marker::PhantomData)
+                }
+
+                #[inline]
+                pub unsafe fn as_ref(&self) -> &T {
+                    #transmute
+                }
+
+                #[inline]
+                pub unsafe fn as_mut(&mut self) -> &mut T {
+                    #transmute
+                }
+            }
+        };
+
+        let union_field_default_impl = quote! {
+            impl<T> ::#prefix::default::Default for __BindgenUnionField<T> {
+                #[inline]
+                fn default() -> Self {
+                    Self::new()
+                }
+            }
+        };
+
+        let union_field_clone_impl = quote! {
+            impl<T> ::#prefix::clone::Clone for __BindgenUnionField<T> {
+                #[inline]
+                fn clone(&self) -> Self {
+                    *self
+                }
+            }
+        };
+
+        let union_field_copy_impl = quote! {
+            impl<T> ::#prefix::marker::Copy for __BindgenUnionField<T> {}
+        };
+
+        let union_field_debug_impl = quote! {
+            impl<T> ::#prefix::fmt::Debug for __BindgenUnionField<T> {
+                fn fmt(&self, fmt: &mut ::#prefix::fmt::Formatter<'_>)
+                       -> ::#prefix::fmt::Result {
+                    fmt.write_str("__BindgenUnionField")
+                }
+            }
+        };
+
+        // The actual memory of the filed will be hashed, so that's why these
+        // field doesn't do anything with the hash.
+        let union_field_hash_impl = quote! {
+            impl<T> ::#prefix::hash::Hash for __BindgenUnionField<T> {
+                fn hash<H: ::#prefix::hash::Hasher>(&self, _state: &mut H) {
+                }
+            }
+        };
+
+        let union_field_partialeq_impl = quote! {
+            impl<T> ::#prefix::cmp::PartialEq for __BindgenUnionField<T> {
+               fn eq(&self, _other: &__BindgenUnionField<T>) -> bool {
+                   true
+               }
+           }
+        };
+
+        let union_field_eq_impl = quote! {
+           impl<T> ::#prefix::cmp::Eq for __BindgenUnionField<T> {
+           }
+        };
+
+        let items = vec![
+            union_field_decl,
+            union_field_impl,
+            union_field_default_impl,
+            union_field_clone_impl,
+            union_field_copy_impl,
+            union_field_debug_impl,
+            union_field_hash_impl,
+            union_field_partialeq_impl,
+            union_field_eq_impl,
+        ];
+
+        let old_items = mem::replace(result, items);
+        result.extend(old_items);
+    }
+
+    pub(crate) fn prepend_incomplete_array_types(
+        ctx: &BindgenContext,
+        result: &mut Vec<proc_macro2::TokenStream>,
+    ) {
+        let prefix = ctx.trait_prefix();
+
+        // If the target supports `const fn`, declare eligible functions
+        // as `const fn` else just `fn`.
+        let const_fn = if ctx.options().rust_features().min_const_fn {
+            quote! { const fn }
+        } else {
+            quote! { fn }
+        };
+
+        let incomplete_array_decl = quote! {
+            #[repr(C)]
+            #[derive(Default)]
+            pub struct __IncompleteArrayField<T>(
+                ::#prefix::marker::PhantomData<T>, [T; 0]);
+        };
+
+        let from_raw_parts = ctx.wrap_unsafe_ops(quote! (
+            ::#prefix::slice::from_raw_parts(self.as_ptr(), len)
+        ));
+        let from_raw_parts_mut = ctx.wrap_unsafe_ops(quote! (
+            ::#prefix::slice::from_raw_parts_mut(self.as_mut_ptr(), len)
+        ));
+
+        let incomplete_array_impl = quote! {
+            impl<T> __IncompleteArrayField<T> {
+                #[inline]
+                pub #const_fn new() -> Self {
+                    __IncompleteArrayField(::#prefix::marker::PhantomData, [])
+                }
+
+                #[inline]
+                pub fn as_ptr(&self) -> *const T {
+                    self as *const _ as *const T
+                }
+
+                #[inline]
+                pub fn as_mut_ptr(&mut self) -> *mut T {
+                    self as *mut _ as *mut T
+                }
+
+                #[inline]
+                pub unsafe fn as_slice(&self, len: usize) -> &[T] {
+                    #from_raw_parts
+                }
+
+                #[inline]
+                pub unsafe fn as_mut_slice(&mut self, len: usize) -> &mut [T] {
+                    #from_raw_parts_mut
+                }
+            }
+        };
+
+        let incomplete_array_debug_impl = quote! {
+            impl<T> ::#prefix::fmt::Debug for __IncompleteArrayField<T> {
+                fn fmt(&self, fmt: &mut ::#prefix::fmt::Formatter<'_>)
+                       -> ::#prefix::fmt::Result {
+                    fmt.write_str("__IncompleteArrayField")
+                }
+            }
+        };
+
+        let items = vec![
+            incomplete_array_decl,
+            incomplete_array_impl,
+            incomplete_array_debug_impl,
+        ];
+
+        let old_items = mem::replace(result, items);
+        result.extend(old_items);
+    }
+
+    pub(crate) fn prepend_float16_type(
+        result: &mut Vec<proc_macro2::TokenStream>,
+    ) {
+        let float16_type = quote! {
+            #[derive(PartialEq, Copy, Clone, Hash, Debug, Default)]
+            #[repr(transparent)]
+            pub struct __BindgenFloat16(pub u16);
+        };
+
+        let items = vec![float16_type];
+        let old_items = mem::replace(result, items);
+        result.extend(old_items);
+    }
+
+    pub(crate) fn prepend_complex_type(
+        result: &mut Vec<proc_macro2::TokenStream>,
+    ) {
+        let complex_type = quote! {
+            #[derive(PartialEq, Copy, Clone, Hash, Debug, Default)]
+            #[repr(C)]
+            pub struct __BindgenComplex<T> {
+                pub re: T,
+                pub im: T
+            }
+        };
+
+        let items = vec![complex_type];
+        let old_items = mem::replace(result, items);
+        result.extend(old_items);
+    }
+
+    pub(crate) fn build_path(
+        item: &Item,
+        ctx: &BindgenContext,
+    ) -> error::Result<syn::Type> {
+        let path = item.namespace_aware_canonical_path(ctx);
+        let tokens =
+            proc_macro2::TokenStream::from_str(&path.join("::")).unwrap();
+
+        Ok(syn::parse_quote! { #tokens })
+    }
+
+    fn primitive_ty(ctx: &BindgenContext, name: &str) -> syn::Type {
+        let ident = ctx.rust_ident_raw(name);
+        syn::parse_quote! { #ident }
+    }
+
+    pub(crate) fn type_from_named(
+        ctx: &BindgenContext,
+        name: &str,
+    ) -> Option<syn::Type> {
+        // FIXME: We could use the inner item to check this is really a
+        // primitive type but, who the heck overrides these anyway?
+        Some(match name {
+            "int8_t" => primitive_ty(ctx, "i8"),
+            "uint8_t" => primitive_ty(ctx, "u8"),
+            "int16_t" => primitive_ty(ctx, "i16"),
+            "uint16_t" => primitive_ty(ctx, "u16"),
+            "int32_t" => primitive_ty(ctx, "i32"),
+            "uint32_t" => primitive_ty(ctx, "u32"),
+            "int64_t" => primitive_ty(ctx, "i64"),
+            "uint64_t" => primitive_ty(ctx, "u64"),
+
+            "size_t" if ctx.options().size_t_is_usize => {
+                primitive_ty(ctx, "usize")
+            }
+            "uintptr_t" => primitive_ty(ctx, "usize"),
+
+            "ssize_t" if ctx.options().size_t_is_usize => {
+                primitive_ty(ctx, "isize")
+            }
+            "intptr_t" | "ptrdiff_t" => primitive_ty(ctx, "isize"),
+            _ => return None,
+        })
+    }
+
+    fn fnsig_return_ty_internal(
+        ctx: &BindgenContext,
+        sig: &FunctionSig,
+    ) -> syn::Type {
+        if sig.is_divergent() {
+            return syn::parse_quote! { ! };
+        }
+
+        let canonical_type_kind = sig
+            .return_type()
+            .into_resolver()
+            .through_type_refs()
+            .through_type_aliases()
+            .resolve(ctx)
+            .kind()
+            .expect_type()
+            .kind();
+
+        match canonical_type_kind {
+            TypeKind::Void => syn::parse_quote! { () },
+            _ => sig.return_type().to_rust_ty_or_opaque(ctx, &()),
+        }
+    }
+
+    pub(crate) fn fnsig_return_ty(
+        ctx: &BindgenContext,
+        sig: &FunctionSig,
+    ) -> proc_macro2::TokenStream {
+        match fnsig_return_ty_internal(ctx, sig) {
+            syn::Type::Tuple(syn::TypeTuple { elems, .. })
+                if elems.is_empty() =>
+            {
+                quote! {}
+            }
+            ty => quote! { -> #ty },
+        }
+    }
+
+    pub(crate) fn fnsig_argument_type(
+        ctx: &BindgenContext,
+        ty: &TypeId,
+    ) -> syn::Type {
+        use super::ToPtr;
+
+        let arg_item = ctx.resolve_item(ty);
+        let arg_ty = arg_item.kind().expect_type();
+
+        // From the C90 standard[1]:
+        //
+        //     A declaration of a parameter as "array of type" shall be
+        //     adjusted to "qualified pointer to type", where the type
+        //     qualifiers (if any) are those specified within the [ and ] of
+        //     the array type derivation.
+        //
+        // [1]: http://c0x.coding-guidelines.com/6.7.5.3.html
+        match *arg_ty.canonical_type(ctx).kind() {
+            TypeKind::Array(t, _) => {
+                let stream = if ctx.options().array_pointers_in_arguments {
+                    arg_ty.to_rust_ty_or_opaque(ctx, arg_item)
+                } else {
+                    t.to_rust_ty_or_opaque(ctx, &())
+                };
+                stream.to_ptr(ctx.resolve_type(t).is_const())
+            }
+            TypeKind::Pointer(inner) => {
+                let inner = ctx.resolve_item(inner);
+                let inner_ty = inner.expect_type();
+                if let TypeKind::ObjCInterface(ref interface) =
+                    *inner_ty.canonical_type(ctx).kind()
+                {
+                    let name = ctx.rust_ident(interface.name());
+                    syn::parse_quote! { #name }
+                } else {
+                    arg_item.to_rust_ty_or_opaque(ctx, &())
+                }
+            }
+            _ => arg_item.to_rust_ty_or_opaque(ctx, &()),
+        }
+    }
+
+    pub(crate) fn fnsig_arguments_iter<
+        'a,
+        I: Iterator<Item = &'a (Option<String>, crate::ir::context::TypeId)>,
+    >(
+        ctx: &BindgenContext,
+        args_iter: I,
+        is_variadic: bool,
+    ) -> Vec<proc_macro2::TokenStream> {
+        let mut unnamed_arguments = 0;
+        let mut args = args_iter
+            .map(|(name, ty)| {
+                let arg_ty = fnsig_argument_type(ctx, ty);
+
+                let arg_name = match *name {
+                    Some(ref name) => ctx.rust_mangle(name).into_owned(),
+                    None => {
+                        unnamed_arguments += 1;
+                        format!("arg{}", unnamed_arguments)
+                    }
+                };
+
+                assert!(!arg_name.is_empty());
+                let arg_name = ctx.rust_ident(arg_name);
+
+                quote! {
+                    #arg_name : #arg_ty
+                }
+            })
+            .collect::<Vec<_>>();
+
+        if is_variadic {
+            args.push(quote! { ... })
+        }
+
+        args
+    }
+
+    pub(crate) fn fnsig_arguments(
+        ctx: &BindgenContext,
+        sig: &FunctionSig,
+    ) -> Vec<proc_macro2::TokenStream> {
+        fnsig_arguments_iter(
+            ctx,
+            sig.argument_types().iter(),
+            sig.is_variadic(),
+        )
+    }
+
+    pub(crate) fn fnsig_argument_identifiers(
+        ctx: &BindgenContext,
+        sig: &FunctionSig,
+    ) -> Vec<proc_macro2::TokenStream> {
+        let mut unnamed_arguments = 0;
+        let args = sig
+            .argument_types()
+            .iter()
+            .map(|&(ref name, _ty)| {
+                let arg_name = match *name {
+                    Some(ref name) => ctx.rust_mangle(name).into_owned(),
+                    None => {
+                        unnamed_arguments += 1;
+                        format!("arg{}", unnamed_arguments)
+                    }
+                };
+
+                assert!(!arg_name.is_empty());
+                let arg_name = ctx.rust_ident(arg_name);
+
+                quote! {
+                    #arg_name
+                }
+            })
+            .collect::<Vec<_>>();
+
+        args
+    }
+
+    pub(crate) fn fnsig_block(
+        ctx: &BindgenContext,
+        sig: &FunctionSig,
+    ) -> proc_macro2::TokenStream {
+        let args = sig.argument_types().iter().map(|&(_, ty)| {
+            let arg_item = ctx.resolve_item(ty);
+
+            arg_item.to_rust_ty_or_opaque(ctx, &())
+        });
+
+        let ret_ty = fnsig_return_ty_internal(ctx, sig);
+        quote! {
+            *const ::block::Block<(#(#args,)*), #ret_ty>
+        }
+    }
+
+    // Returns true if `canonical_name` will end up as `mangled_name` at the
+    // machine code level, i.e. after LLVM has applied any target specific
+    // mangling.
+    pub(crate) fn names_will_be_identical_after_mangling(
+        canonical_name: &str,
+        mangled_name: &str,
+        call_conv: Option<ClangAbi>,
+    ) -> bool {
+        // If the mangled name and the canonical name are the same then no
+        // mangling can have happened between the two versions.
+        if canonical_name == mangled_name {
+            return true;
+        }
+
+        // Working with &[u8] makes indexing simpler than with &str
+        let canonical_name = canonical_name.as_bytes();
+        let mangled_name = mangled_name.as_bytes();
+
+        let (mangling_prefix, expect_suffix) = match call_conv {
+            Some(ClangAbi::Known(Abi::C)) |
+            // None is the case for global variables
+            None => {
+                (b'_', false)
+            }
+            Some(ClangAbi::Known(Abi::Stdcall)) => (b'_', true),
+            Some(ClangAbi::Known(Abi::Fastcall)) => (b'@', true),
+
+            // This is something we don't recognize, stay on the safe side
+            // by emitting the `#[link_name]` attribute
+            Some(_) => return false,
+        };
+
+        // Check that the mangled name is long enough to at least contain the
+        // canonical name plus the expected prefix.
+        if mangled_name.len() < canonical_name.len() + 1 {
+            return false;
+        }
+
+        // Return if the mangled name does not start with the prefix expected
+        // for the given calling convention.
+        if mangled_name[0] != mangling_prefix {
+            return false;
+        }
+
+        // Check that the mangled name contains the canonical name after the
+        // prefix
+        if &mangled_name[1..canonical_name.len() + 1] != canonical_name {
+            return false;
+        }
+
+        // If the given calling convention also prescribes a suffix, check that
+        // it exists too
+        if expect_suffix {
+            let suffix = &mangled_name[canonical_name.len() + 1..];
+
+            // The shortest suffix is "@0"
+            if suffix.len() < 2 {
+                return false;
+            }
+
+            // Check that the suffix starts with '@' and is all ASCII decimals
+            // after that.
+            if suffix[0] != b'@' || !suffix[1..].iter().all(u8::is_ascii_digit)
+            {
+                return false;
+            }
+        } else if mangled_name.len() != canonical_name.len() + 1 {
+            // If we don't expect a prefix but there is one, we need the
+            // #[link_name] attribute
+            return false;
+        }
+
+        true
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/postprocessing/merge_extern_blocks.rs b/third_party/rust/bindgen/codegen/postprocessing/merge_extern_blocks.rs
new file mode 100644
index 0000000000..10fa0ec80b
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/postprocessing/merge_extern_blocks.rs
@@ -0,0 +1,72 @@
+use syn::{
+    visit_mut::{visit_file_mut, visit_item_mod_mut, VisitMut},
+    File, Item, ItemForeignMod, ItemMod,
+};
+
+pub(super) fn merge_extern_blocks(file: &mut File) {
+    Visitor.visit_file_mut(file)
+}
+
+struct Visitor;
+
+impl VisitMut for Visitor {
+    fn visit_file_mut(&mut self, file: &mut File) {
+        visit_items(&mut file.items);
+        visit_file_mut(self, file)
+    }
+
+    fn visit_item_mod_mut(&mut self, item_mod: &mut ItemMod) {
+        if let Some((_, ref mut items)) = item_mod.content {
+            visit_items(items);
+        }
+        visit_item_mod_mut(self, item_mod)
+    }
+}
+
+fn visit_items(items: &mut Vec<Item>) {
+    // Keep all the extern blocks in a different `Vec` for faster search.
+    let mut extern_blocks = Vec::<ItemForeignMod>::new();
+
+    for item in std::mem::take(items) {
+        if let Item::ForeignMod(ItemForeignMod {
+            attrs,
+            abi,
+            brace_token,
+            unsafety,
+            items: extern_block_items,
+        }) = item
+        {
+            let mut exists = false;
+            for extern_block in &mut extern_blocks {
+                // Check if there is a extern block with the same ABI and
+                // attributes.
+                if extern_block.attrs == attrs && extern_block.abi == abi {
+                    // Merge the items of the two blocks.
+                    extern_block.items.extend_from_slice(&extern_block_items);
+                    exists = true;
+                    break;
+                }
+            }
+            // If no existing extern block had the same ABI and attributes, store
+            // it.
+            if !exists {
+                extern_blocks.push(ItemForeignMod {
+                    attrs,
+                    abi,
+                    brace_token,
+                    unsafety,
+                    items: extern_block_items,
+                });
+            }
+        } else {
+            // If the item is not an extern block, we don't have to do anything and just
+            // push it back.
+            items.push(item);
+        }
+    }
+
+    // Move all the extern blocks alongside the rest of the items.
+    for extern_block in extern_blocks {
+        items.push(Item::ForeignMod(extern_block));
+    }
+}
diff --git a/third_party/rust/bindgen/codegen/postprocessing/mod.rs b/third_party/rust/bindgen/codegen/postprocessing/mod.rs
new file mode 100644
index 0000000000..9641698521
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/postprocessing/mod.rs
@@ -0,0 +1,57 @@
+use proc_macro2::TokenStream;
+use quote::ToTokens;
+use syn::{parse2, File};
+
+use crate::BindgenOptions;
+
+mod merge_extern_blocks;
+mod sort_semantically;
+
+use merge_extern_blocks::merge_extern_blocks;
+use sort_semantically::sort_semantically;
+
+struct PostProcessingPass {
+    should_run: fn(&BindgenOptions) -> bool,
+    run: fn(&mut File),
+}
+
+// TODO: This can be a const fn when mutable references are allowed in const
+// context.
+macro_rules! pass {
+    ($pass:ident) => {
+        PostProcessingPass {
+            should_run: |options| options.$pass,
+            run: |file| $pass(file),
+        }
+    };
+}
+
+const PASSES: &[PostProcessingPass] =
+    &[pass!(merge_extern_blocks), pass!(sort_semantically)];
+
+pub(crate) fn postprocessing(
+    items: Vec<TokenStream>,
+    options: &BindgenOptions,
+) -> TokenStream {
+    let items = items.into_iter().collect();
+    let require_syn = PASSES.iter().any(|pass| (pass.should_run)(options));
+
+    if !require_syn {
+        return items;
+    }
+
+    // This syn business is a hack, for now. This means that we are re-parsing already
+    // generated code using `syn` (as opposed to `quote`) because `syn` provides us more
+    // control over the elements.
+    // The `unwrap` here is deliberate because bindgen should generate valid rust items at all
+    // times.
+    let mut file = parse2::<File>(items).unwrap();
+
+    for pass in PASSES {
+        if (pass.should_run)(options) {
+            (pass.run)(&mut file);
+        }
+    }
+
+    file.into_token_stream()
+}
diff --git a/third_party/rust/bindgen/codegen/postprocessing/sort_semantically.rs b/third_party/rust/bindgen/codegen/postprocessing/sort_semantically.rs
new file mode 100644
index 0000000000..be94ce69c5
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/postprocessing/sort_semantically.rs
@@ -0,0 +1,46 @@
+use syn::{
+    visit_mut::{visit_file_mut, visit_item_mod_mut, VisitMut},
+    File, Item, ItemMod,
+};
+
+pub(super) fn sort_semantically(file: &mut File) {
+    Visitor.visit_file_mut(file)
+}
+
+struct Visitor;
+
+impl VisitMut for Visitor {
+    fn visit_file_mut(&mut self, file: &mut File) {
+        visit_items(&mut file.items);
+        visit_file_mut(self, file)
+    }
+
+    fn visit_item_mod_mut(&mut self, item_mod: &mut ItemMod) {
+        if let Some((_, ref mut items)) = item_mod.content {
+            visit_items(items);
+        }
+        visit_item_mod_mut(self, item_mod)
+    }
+}
+
+fn visit_items(items: &mut [Item]) {
+    items.sort_by_key(|item| match item {
+        Item::Type(_) => 0,
+        Item::Struct(_) => 1,
+        Item::Const(_) => 2,
+        Item::Fn(_) => 3,
+        Item::Enum(_) => 4,
+        Item::Union(_) => 5,
+        Item::Static(_) => 6,
+        Item::Trait(_) => 7,
+        Item::TraitAlias(_) => 8,
+        Item::Impl(_) => 9,
+        Item::Mod(_) => 10,
+        Item::Use(_) => 11,
+        Item::Verbatim(_) => 12,
+        Item::ExternCrate(_) => 13,
+        Item::ForeignMod(_) => 14,
+        Item::Macro(_) => 15,
+        _ => 18,
+    });
+}
diff --git a/third_party/rust/bindgen/codegen/serialize.rs b/third_party/rust/bindgen/codegen/serialize.rs
new file mode 100644
index 0000000000..9765a8bdf2
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/serialize.rs
@@ -0,0 +1,444 @@
+use std::io::Write;
+
+use crate::callbacks::IntKind;
+
+use crate::ir::comp::CompKind;
+use crate::ir::context::{BindgenContext, TypeId};
+use crate::ir::function::{Function, FunctionKind};
+use crate::ir::item::Item;
+use crate::ir::item::ItemCanonicalName;
+use crate::ir::item_kind::ItemKind;
+use crate::ir::ty::{FloatKind, Type, TypeKind};
+
+use super::{CodegenError, WrapAsVariadic};
+
+fn get_loc(item: &Item) -> String {
+    item.location()
+        .map(|x| x.to_string())
+        .unwrap_or_else(|| "unknown".to_owned())
+}
+
+pub(super) trait CSerialize<'a> {
+    type Extra;
+
+    fn serialize<W: Write>(
+        &self,
+        ctx: &BindgenContext,
+        extra: Self::Extra,
+        stack: &mut Vec<String>,
+        writer: &mut W,
+    ) -> Result<(), CodegenError>;
+}
+
+impl<'a> CSerialize<'a> for Item {
+    type Extra = &'a Option<WrapAsVariadic>;
+
+    fn serialize<W: Write>(
+        &self,
+        ctx: &BindgenContext,
+        extra: Self::Extra,
+        stack: &mut Vec<String>,
+        writer: &mut W,
+    ) -> Result<(), CodegenError> {
+        match self.kind() {
+            ItemKind::Function(func) => {
+                func.serialize(ctx, (self, extra), stack, writer)
+            }
+            kind => Err(CodegenError::Serialize {
+                msg: format!("Cannot serialize item kind {:?}", kind),
+                loc: get_loc(self),
+            }),
+        }
+    }
+}
+
+impl<'a> CSerialize<'a> for Function {
+    type Extra = (&'a Item, &'a Option<WrapAsVariadic>);
+
+    fn serialize<W: Write>(
+        &self,
+        ctx: &BindgenContext,
+        (item, wrap_as_variadic): Self::Extra,
+        stack: &mut Vec<String>,
+        writer: &mut W,
+    ) -> Result<(), CodegenError> {
+        if self.kind() != FunctionKind::Function {
+            return Err(CodegenError::Serialize {
+                msg: format!(
+                    "Cannot serialize function kind {:?}",
+                    self.kind(),
+                ),
+                loc: get_loc(item),
+            });
+        }
+
+        let signature = match ctx.resolve_type(self.signature()).kind() {
+            TypeKind::Function(signature) => signature,
+            _ => unreachable!(),
+        };
+
+        assert!(!signature.is_variadic());
+
+        let name = self.name();
+
+        // Function argoments stored as `(name, type_id)` tuples.
+        let args = {
+            let mut count = 0;
+
+            let idx_to_prune = wrap_as_variadic.as_ref().map(
+                |WrapAsVariadic {
+                     idx_of_va_list_arg, ..
+                 }| *idx_of_va_list_arg,
+            );
+
+            signature
+                .argument_types()
+                .iter()
+                .cloned()
+                .enumerate()
+                .filter_map(|(idx, (opt_name, type_id))| {
+                    if Some(idx) == idx_to_prune {
+                        None
+                    } else {
+                        Some((
+                            opt_name.unwrap_or_else(|| {
+                                let name = format!("arg_{}", count);
+                                count += 1;
+                                name
+                            }),
+                            type_id,
+                        ))
+                    }
+                })
+                .collect::<Vec<_>>()
+        };
+
+        // The name used for the wrapper self.
+        let wrap_name = format!("{}{}", name, ctx.wrap_static_fns_suffix());
+
+        // The function's return type
+        let (ret_item, ret_ty) = {
+            let type_id = signature.return_type();
+            let ret_item = ctx.resolve_item(type_id);
+            let ret_ty = ret_item.expect_type();
+
+            // Write `ret_ty`.
+            ret_ty.serialize(ctx, ret_item, stack, writer)?;
+
+            (ret_item, ret_ty)
+        };
+
+        const INDENT: &str = "    ";
+
+        // Write `wrap_name(args`.
+        write!(writer, " {}(", wrap_name)?;
+        serialize_args(&args, ctx, writer)?;
+
+        if wrap_as_variadic.is_none() {
+            // Write `) { name(` if the function returns void and `) { return name(` if it does not.
+            if ret_ty.is_void() {
+                write!(writer, ") {{ {}(", name)?;
+            } else {
+                write!(writer, ") {{ return {}(", name)?;
+            }
+        } else {
+            // Write `, ...) {`
+            writeln!(writer, ", ...) {{")?;
+
+            // Declare the return type `RET_TY ret;` if their is a need to do so
+            if !ret_ty.is_void() {
+                write!(writer, "{INDENT}")?;
+                ret_ty.serialize(ctx, ret_item, stack, writer)?;
+                writeln!(writer, " ret;")?;
+            }
+
+            // Setup va_list
+            writeln!(writer, "{INDENT}va_list ap;\n")?;
+            writeln!(
+                writer,
+                "{INDENT}va_start(ap, {});",
+                args.last().unwrap().0
+            )?;
+
+            write!(writer, "{INDENT}")?;
+            // Write `ret = name(` or `name(` depending if the function returns something
+            if !ret_ty.is_void() {
+                write!(writer, "ret = ")?;
+            }
+            write!(writer, "{}(", name)?;
+        }
+
+        // Get the arguments names and insert at the right place if necessary `ap`
+        let mut args: Vec<_> = args.into_iter().map(|(name, _)| name).collect();
+        if let Some(WrapAsVariadic {
+            idx_of_va_list_arg, ..
+        }) = wrap_as_variadic
+        {
+            args.insert(*idx_of_va_list_arg, "ap".to_owned());
+        }
+
+        // Write `arg_names);`.
+        serialize_sep(", ", args.iter(), ctx, writer, |name, _, buf| {
+            write!(buf, "{}", name).map_err(From::from)
+        })?;
+        #[rustfmt::skip]
+        write!(writer, ");{}", if wrap_as_variadic.is_none() { " " } else { "\n" })?;
+
+        if wrap_as_variadic.is_some() {
+            // End va_list and return the result if their is one
+            writeln!(writer, "{INDENT}va_end(ap);")?;
+            if !ret_ty.is_void() {
+                writeln!(writer, "{INDENT}return ret;")?;
+            }
+        }
+
+        writeln!(writer, "}}")?;
+
+        Ok(())
+    }
+}
+
+impl<'a> CSerialize<'a> for TypeId {
+    type Extra = ();
+
+    fn serialize<W: Write>(
+        &self,
+        ctx: &BindgenContext,
+        (): Self::Extra,
+        stack: &mut Vec<String>,
+        writer: &mut W,
+    ) -> Result<(), CodegenError> {
+        let item = ctx.resolve_item(*self);
+        item.expect_type().serialize(ctx, item, stack, writer)
+    }
+}
+
+impl<'a> CSerialize<'a> for Type {
+    type Extra = &'a Item;
+
+    fn serialize<W: Write>(
+        &self,
+        ctx: &BindgenContext,
+        item: Self::Extra,
+        stack: &mut Vec<String>,
+        writer: &mut W,
+    ) -> Result<(), CodegenError> {
+        match self.kind() {
+            TypeKind::Void => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+                write!(writer, "void")?
+            }
+            TypeKind::NullPtr => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+                write!(writer, "nullptr_t")?
+            }
+            TypeKind::Int(int_kind) => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+                match int_kind {
+                    IntKind::Bool => write!(writer, "bool")?,
+                    IntKind::SChar => write!(writer, "signed char")?,
+                    IntKind::UChar => write!(writer, "unsigned char")?,
+                    IntKind::WChar => write!(writer, "wchar_t")?,
+                    IntKind::Short => write!(writer, "short")?,
+                    IntKind::UShort => write!(writer, "unsigned short")?,
+                    IntKind::Int => write!(writer, "int")?,
+                    IntKind::UInt => write!(writer, "unsigned int")?,
+                    IntKind::Long => write!(writer, "long")?,
+                    IntKind::ULong => write!(writer, "unsigned long")?,
+                    IntKind::LongLong => write!(writer, "long long")?,
+                    IntKind::ULongLong => write!(writer, "unsigned long long")?,
+                    IntKind::Char { .. } => write!(writer, "char")?,
+                    int_kind => {
+                        return Err(CodegenError::Serialize {
+                            msg: format!(
+                                "Cannot serialize integer kind {:?}",
+                                int_kind
+                            ),
+                            loc: get_loc(item),
+                        })
+                    }
+                }
+            }
+            TypeKind::Float(float_kind) => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+                match float_kind {
+                    FloatKind::Float16 => write!(writer, "_Float16")?,
+                    FloatKind::Float => write!(writer, "float")?,
+                    FloatKind::Double => write!(writer, "double")?,
+                    FloatKind::LongDouble => write!(writer, "long double")?,
+                    FloatKind::Float128 => write!(writer, "__float128")?,
+                }
+            }
+            TypeKind::Complex(float_kind) => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+                match float_kind {
+                    FloatKind::Float16 => write!(writer, "_Float16 complex")?,
+                    FloatKind::Float => write!(writer, "float complex")?,
+                    FloatKind::Double => write!(writer, "double complex")?,
+                    FloatKind::LongDouble => {
+                        write!(writer, "long double complex")?
+                    }
+                    FloatKind::Float128 => write!(writer, "__complex128")?,
+                }
+            }
+            TypeKind::Alias(type_id) => {
+                if let Some(name) = self.name() {
+                    if self.is_const() {
+                        write!(writer, "const {}", name)?;
+                    } else {
+                        write!(writer, "{}", name)?;
+                    }
+                } else {
+                    type_id.serialize(ctx, (), stack, writer)?;
+                }
+            }
+            TypeKind::Array(type_id, length) => {
+                type_id.serialize(ctx, (), stack, writer)?;
+                write!(writer, " [{}]", length)?
+            }
+            TypeKind::Function(signature) => {
+                if self.is_const() {
+                    stack.push("const ".to_string());
+                }
+
+                signature.return_type().serialize(
+                    ctx,
+                    (),
+                    &mut vec![],
+                    writer,
+                )?;
+
+                write!(writer, " (")?;
+                while let Some(item) = stack.pop() {
+                    write!(writer, "{}", item)?;
+                }
+                write!(writer, ")")?;
+
+                let args = signature.argument_types();
+                if args.is_empty() {
+                    write!(writer, " (void)")?;
+                } else {
+                    write!(writer, " (")?;
+                    serialize_sep(
+                        ", ",
+                        args.iter(),
+                        ctx,
+                        writer,
+                        |(name, type_id), ctx, buf| {
+                            let mut stack = vec![];
+                            if let Some(name) = name {
+                                stack.push(name.clone());
+                            }
+                            type_id.serialize(ctx, (), &mut stack, buf)
+                        },
+                    )?;
+                    write!(writer, ")")?
+                }
+            }
+            TypeKind::ResolvedTypeRef(type_id) => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+                type_id.serialize(ctx, (), stack, writer)?
+            }
+            TypeKind::Pointer(type_id) => {
+                if self.is_const() {
+                    stack.push("*const ".to_owned());
+                } else {
+                    stack.push("*".to_owned());
+                }
+                type_id.serialize(ctx, (), stack, writer)?
+            }
+            TypeKind::Comp(comp_info) => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+
+                let name = item.canonical_name(ctx);
+
+                match comp_info.kind() {
+                    CompKind::Struct => write!(writer, "struct {}", name)?,
+                    CompKind::Union => write!(writer, "union {}", name)?,
+                };
+            }
+            TypeKind::Enum(_enum_ty) => {
+                if self.is_const() {
+                    write!(writer, "const ")?;
+                }
+
+                let name = item.canonical_name(ctx);
+                write!(writer, "enum {}", name)?;
+            }
+            ty => {
+                return Err(CodegenError::Serialize {
+                    msg: format!("Cannot serialize type kind {:?}", ty),
+                    loc: get_loc(item),
+                })
+            }
+        };
+
+        if !stack.is_empty() {
+            write!(writer, " ")?;
+            while let Some(item) = stack.pop() {
+                write!(writer, "{}", item)?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+fn serialize_args<W: Write>(
+    args: &[(String, TypeId)],
+    ctx: &BindgenContext,
+    writer: &mut W,
+) -> Result<(), CodegenError> {
+    if args.is_empty() {
+        write!(writer, "void")?;
+    } else {
+        serialize_sep(
+            ", ",
+            args.iter(),
+            ctx,
+            writer,
+            |(name, type_id), ctx, buf| {
+                type_id.serialize(ctx, (), &mut vec![name.clone()], buf)
+            },
+        )?;
+    }
+
+    Ok(())
+}
+
+fn serialize_sep<
+    W: Write,
+    F: FnMut(I::Item, &BindgenContext, &mut W) -> Result<(), CodegenError>,
+    I: Iterator,
+>(
+    sep: &str,
+    mut iter: I,
+    ctx: &BindgenContext,
+    buf: &mut W,
+    mut f: F,
+) -> Result<(), CodegenError> {
+    if let Some(item) = iter.next() {
+        f(item, ctx, buf)?;
+        let sep = sep.as_bytes();
+        for item in iter {
+            buf.write_all(sep)?;
+            f(item, ctx, buf)?;
+        }
+    }
+
+    Ok(())
+}
diff --git a/third_party/rust/bindgen/codegen/struct_layout.rs b/third_party/rust/bindgen/codegen/struct_layout.rs
new file mode 100644
index 0000000000..f4596a1992
--- /dev/null
+++ b/third_party/rust/bindgen/codegen/struct_layout.rs
@@ -0,0 +1,451 @@
+//! Helpers for code generation that need struct layout
+
+use super::helpers;
+
+use crate::ir::comp::CompInfo;
+use crate::ir::context::BindgenContext;
+use crate::ir::layout::Layout;
+use crate::ir::ty::{Type, TypeKind};
+use crate::FieldVisibilityKind;
+use proc_macro2::{self, Ident, Span};
+use std::cmp;
+
+const MAX_GUARANTEED_ALIGN: usize = 8;
+
+/// Trace the layout of struct.
+#[derive(Debug)]
+pub(crate) struct StructLayoutTracker<'a> {
+    name: &'a str,
+    ctx: &'a BindgenContext,
+    comp: &'a CompInfo,
+    is_packed: bool,
+    known_type_layout: Option<Layout>,
+    is_rust_union: bool,
+    can_copy_union_fields: bool,
+    latest_offset: usize,
+    padding_count: usize,
+    latest_field_layout: Option<Layout>,
+    max_field_align: usize,
+    last_field_was_bitfield: bool,
+    visibility: FieldVisibilityKind,
+}
+
+/// Returns a size aligned to a given value.
+pub(crate) fn align_to(size: usize, align: usize) -> usize {
+    if align == 0 {
+        return size;
+    }
+
+    let rem = size % align;
+    if rem == 0 {
+        return size;
+    }
+
+    size + align - rem
+}
+
+/// Returns the lower power of two byte count that can hold at most n bits.
+pub(crate) fn bytes_from_bits_pow2(mut n: usize) -> usize {
+    if n == 0 {
+        return 0;
+    }
+
+    if n <= 8 {
+        return 1;
+    }
+
+    if !n.is_power_of_two() {
+        n = n.next_power_of_two();
+    }
+
+    n / 8
+}
+
+#[test]
+fn test_align_to() {
+    assert_eq!(align_to(1, 1), 1);
+    assert_eq!(align_to(1, 2), 2);
+    assert_eq!(align_to(1, 4), 4);
+    assert_eq!(align_to(5, 1), 5);
+    assert_eq!(align_to(17, 4), 20);
+}
+
+#[test]
+fn test_bytes_from_bits_pow2() {
+    assert_eq!(bytes_from_bits_pow2(0), 0);
+    for i in 1..9 {
+        assert_eq!(bytes_from_bits_pow2(i), 1);
+    }
+    for i in 9..17 {
+        assert_eq!(bytes_from_bits_pow2(i), 2);
+    }
+    for i in 17..33 {
+        assert_eq!(bytes_from_bits_pow2(i), 4);
+    }
+}
+
+impl<'a> StructLayoutTracker<'a> {
+    pub(crate) fn new(
+        ctx: &'a BindgenContext,
+        comp: &'a CompInfo,
+        ty: &'a Type,
+        name: &'a str,
+        visibility: FieldVisibilityKind,
+        is_packed: bool,
+    ) -> Self {
+        let known_type_layout = ty.layout(ctx);
+        let (is_rust_union, can_copy_union_fields) =
+            comp.is_rust_union(ctx, known_type_layout.as_ref(), name);
+        StructLayoutTracker {
+            name,
+            ctx,
+            comp,
+            visibility,
+            is_packed,
+            known_type_layout,
+            is_rust_union,
+            can_copy_union_fields,
+            latest_offset: 0,
+            padding_count: 0,
+            latest_field_layout: None,
+            max_field_align: 0,
+            last_field_was_bitfield: false,
+        }
+    }
+
+    pub(crate) fn can_copy_union_fields(&self) -> bool {
+        self.can_copy_union_fields
+    }
+
+    pub(crate) fn is_rust_union(&self) -> bool {
+        self.is_rust_union
+    }
+
+    pub(crate) fn saw_vtable(&mut self) {
+        debug!("saw vtable for {}", self.name);
+
+        let ptr_size = self.ctx.target_pointer_size();
+        self.latest_offset += ptr_size;
+        self.latest_field_layout = Some(Layout::new(ptr_size, ptr_size));
+        self.max_field_align = ptr_size;
+    }
+
+    pub(crate) fn saw_base(&mut self, base_ty: &Type) {
+        debug!("saw base for {}", self.name);
+        if let Some(layout) = base_ty.layout(self.ctx) {
+            self.align_to_latest_field(layout);
+
+            self.latest_offset += self.padding_bytes(layout) + layout.size;
+            self.latest_field_layout = Some(layout);
+            self.max_field_align = cmp::max(self.max_field_align, layout.align);
+        }
+    }
+
+    pub(crate) fn saw_bitfield_unit(&mut self, layout: Layout) {
+        debug!("saw bitfield unit for {}: {:?}", self.name, layout);
+
+        self.align_to_latest_field(layout);
+
+        self.latest_offset += layout.size;
+
+        debug!(
+            "Offset: <bitfield>: {} -> {}",
+            self.latest_offset - layout.size,
+            self.latest_offset
+        );
+
+        self.latest_field_layout = Some(layout);
+        self.last_field_was_bitfield = true;
+        self.max_field_align = cmp::max(self.max_field_align, layout.align);
+    }
+
+    /// Returns a padding field if necessary for a given new field _before_
+    /// adding that field.
+    pub(crate) fn saw_field(
+        &mut self,
+        field_name: &str,
+        field_ty: &Type,
+        field_offset: Option<usize>,
+    ) -> Option<proc_macro2::TokenStream> {
+        let mut field_layout = field_ty.layout(self.ctx)?;
+
+        if let TypeKind::Array(inner, len) =
+            *field_ty.canonical_type(self.ctx).kind()
+        {
+            // FIXME(emilio): As an _ultra_ hack, we correct the layout returned
+            // by arrays of structs that have a bigger alignment than what we
+            // can support.
+            //
+            // This means that the structs in the array are super-unsafe to
+            // access, since they won't be properly aligned, but there's not too
+            // much we can do about it.
+            if let Some(layout) = self.ctx.resolve_type(inner).layout(self.ctx)
+            {
+                if layout.align > MAX_GUARANTEED_ALIGN {
+                    field_layout.size =
+                        align_to(layout.size, layout.align) * len;
+                    field_layout.align = MAX_GUARANTEED_ALIGN;
+                }
+            }
+        }
+        self.saw_field_with_layout(field_name, field_layout, field_offset)
+    }
+
+    pub(crate) fn saw_field_with_layout(
+        &mut self,
+        field_name: &str,
+        field_layout: Layout,
+        field_offset: Option<usize>,
+    ) -> Option<proc_macro2::TokenStream> {
+        let will_merge_with_bitfield = self.align_to_latest_field(field_layout);
+
+        let is_union = self.comp.is_union();
+        let padding_bytes = match field_offset {
+            Some(offset) if offset / 8 > self.latest_offset => {
+                offset / 8 - self.latest_offset
+            }
+            _ => {
+                if will_merge_with_bitfield ||
+                    field_layout.align == 0 ||
+                    is_union
+                {
+                    0
+                } else if !self.is_packed {
+                    self.padding_bytes(field_layout)
+                } else if let Some(mut l) = self.known_type_layout {
+                    if field_layout.align < l.align {
+                        l.align = field_layout.align;
+                    }
+                    self.padding_bytes(l)
+                } else {
+                    0
+                }
+            }
+        };
+
+        self.latest_offset += padding_bytes;
+
+        let padding_layout = if self.is_packed || is_union {
+            None
+        } else {
+            let force_padding = self.ctx.options().force_explicit_padding;
+
+            // Otherwise the padding is useless.
+            let need_padding = force_padding ||
+                padding_bytes >= field_layout.align ||
+                field_layout.align > MAX_GUARANTEED_ALIGN;
+
+            debug!(
+                "Offset: <padding>: {} -> {}",
+                self.latest_offset - padding_bytes,
+                self.latest_offset
+            );
+
+            debug!(
+                "align field {} to {}/{} with {} padding bytes {:?}",
+                field_name,
+                self.latest_offset,
+                field_offset.unwrap_or(0) / 8,
+                padding_bytes,
+                field_layout
+            );
+
+            let padding_align = if force_padding {
+                1
+            } else {
+                cmp::min(field_layout.align, MAX_GUARANTEED_ALIGN)
+            };
+
+            if need_padding && padding_bytes != 0 {
+                Some(Layout::new(padding_bytes, padding_align))
+            } else {
+                None
+            }
+        };
+
+        self.latest_offset += field_layout.size;
+        self.latest_field_layout = Some(field_layout);
+        self.max_field_align =
+            cmp::max(self.max_field_align, field_layout.align);
+        self.last_field_was_bitfield = false;
+
+        debug!(
+            "Offset: {}: {} -> {}",
+            field_name,
+            self.latest_offset - field_layout.size,
+            self.latest_offset
+        );
+
+        padding_layout.map(|layout| self.padding_field(layout))
+    }
+
+    pub(crate) fn add_tail_padding(
+        &mut self,
+        comp_name: &str,
+        comp_layout: Layout,
+    ) -> Option<proc_macro2::TokenStream> {
+        // Only emit an padding field at the end of a struct if the
+        // user configures explicit padding.
+        if !self.ctx.options().force_explicit_padding {
+            return None;
+        }
+
+        // Padding doesn't make sense for rust unions.
+        if self.is_rust_union {
+            return None;
+        }
+
+        if self.latest_offset == comp_layout.size {
+            // This struct does not contain tail padding.
+            return None;
+        }
+
+        trace!(
+            "need a tail padding field for {}: offset {} -> size {}",
+            comp_name,
+            self.latest_offset,
+            comp_layout.size
+        );
+        let size = comp_layout.size - self.latest_offset;
+        Some(self.padding_field(Layout::new(size, 0)))
+    }
+
+    pub(crate) fn pad_struct(
+        &mut self,
+        layout: Layout,
+    ) -> Option<proc_macro2::TokenStream> {
+        debug!(
+            "pad_struct:\n\tself = {:#?}\n\tlayout = {:#?}",
+            self, layout
+        );
+
+        if layout.size < self.latest_offset {
+            warn!(
+                "Calculated wrong layout for {}, too more {} bytes",
+                self.name,
+                self.latest_offset - layout.size
+            );
+            return None;
+        }
+
+        let padding_bytes = layout.size - self.latest_offset;
+        if padding_bytes == 0 {
+            return None;
+        }
+
+        let repr_align = self.ctx.options().rust_features().repr_align;
+
+        // We always pad to get to the correct size if the struct is one of
+        // those we can't align properly.
+        //
+        // Note that if the last field we saw was a bitfield, we may need to pad
+        // regardless, because bitfields don't respect alignment as strictly as
+        // other fields.
+        if padding_bytes >= layout.align ||
+            (self.last_field_was_bitfield &&
+                padding_bytes >= self.latest_field_layout.unwrap().align) ||
+            (!repr_align && layout.align > MAX_GUARANTEED_ALIGN)
+        {
+            let layout = if self.is_packed {
+                Layout::new(padding_bytes, 1)
+            } else if self.last_field_was_bitfield ||
+                layout.align > MAX_GUARANTEED_ALIGN
+            {
+                // We've already given up on alignment here.
+                Layout::for_size(self.ctx, padding_bytes)
+            } else {
+                Layout::new(padding_bytes, layout.align)
+            };
+
+            debug!("pad bytes to struct {}, {:?}", self.name, layout);
+
+            Some(self.padding_field(layout))
+        } else {
+            None
+        }
+    }
+
+    pub(crate) fn requires_explicit_align(&self, layout: Layout) -> bool {
+        let repr_align = self.ctx.options().rust_features().repr_align;
+
+        // Always force explicit repr(align) for stuff more than 16-byte aligned
+        // to work-around https://github.com/rust-lang/rust/issues/54341.
+        //
+        // Worst-case this just generates redundant alignment attributes.
+        if repr_align && self.max_field_align >= 16 {
+            return true;
+        }
+
+        if self.max_field_align >= layout.align {
+            return false;
+        }
+
+        // We can only generate up-to a 8-bytes of alignment unless we support
+        // repr(align).
+        repr_align || layout.align <= MAX_GUARANTEED_ALIGN
+    }
+
+    fn padding_bytes(&self, layout: Layout) -> usize {
+        align_to(self.latest_offset, layout.align) - self.latest_offset
+    }
+
+    fn padding_field(&mut self, layout: Layout) -> proc_macro2::TokenStream {
+        let ty = helpers::blob(self.ctx, layout);
+        let padding_count = self.padding_count;
+
+        self.padding_count += 1;
+
+        let padding_field_name = Ident::new(
+            &format!("__bindgen_padding_{}", padding_count),
+            Span::call_site(),
+        );
+
+        self.max_field_align = cmp::max(self.max_field_align, layout.align);
+
+        let vis = super::access_specifier(self.visibility);
+
+        quote! {
+            #vis #padding_field_name : #ty ,
+        }
+    }
+
+    /// Returns whether the new field is known to merge with a bitfield.
+    ///
+    /// This is just to avoid doing the same check also in pad_field.
+    fn align_to_latest_field(&mut self, new_field_layout: Layout) -> bool {
+        if self.is_packed {
+            // Skip to align fields when packed.
+            return false;
+        }
+
+        let layout = match self.latest_field_layout {
+            Some(l) => l,
+            None => return false,
+        };
+
+        // If it was, we may or may not need to align, depending on what the
+        // current field alignment and the bitfield size and alignment are.
+        debug!(
+            "align_to_bitfield? {}: {:?} {:?}",
+            self.last_field_was_bitfield, layout, new_field_layout
+        );
+
+        // Avoid divide-by-zero errors if align is 0.
+        let align = cmp::max(1, layout.align);
+
+        if self.last_field_was_bitfield &&
+            new_field_layout.align <= layout.size % align &&
+            new_field_layout.size <= layout.size % align
+        {
+            // The new field will be coalesced into some of the remaining bits.
+            //
+            // FIXME(emilio): I think this may not catch everything?
+            debug!("Will merge with bitfield");
+            return true;
+        }
+
+        // Else, just align the obvious way.
+        self.latest_offset += self.padding_bytes(layout);
+        false
+    }
+}
diff --git a/third_party/rust/bindgen/deps.rs b/third_party/rust/bindgen/deps.rs
new file mode 100644
index 0000000000..be31f92896
--- /dev/null
+++ b/third_party/rust/bindgen/deps.rs
@@ -0,0 +1,61 @@
+/// Generating build depfiles from parsed bindings.
+use std::{collections::BTreeSet, path::PathBuf};
+
+#[derive(Clone, Debug)]
+pub(crate) struct DepfileSpec {
+    pub output_module: String,
+    pub depfile_path: PathBuf,
+}
+
+impl DepfileSpec {
+    pub fn write(&self, deps: &BTreeSet<Box<str>>) -> std::io::Result<()> {
+        std::fs::write(&self.depfile_path, self.to_string(deps))
+    }
+
+    fn to_string(&self, deps: &BTreeSet<Box<str>>) -> String {
+        // Transforms a string by escaping spaces and backslashes.
+        let escape = |s: &str| s.replace('\\', "\\\\").replace(' ', "\\ ");
+
+        let mut buf = format!("{}:", escape(&self.output_module));
+        for file in deps {
+            buf = format!("{} {}", buf, escape(file));
+        }
+        buf
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn escaping_depfile() {
+        let spec = DepfileSpec {
+            output_module: "Mod Name".to_owned(),
+            depfile_path: PathBuf::new(),
+        };
+
+        let deps: BTreeSet<_> = vec![
+            r"/absolute/path".into(),
+            r"C:\win\absolute\path".into(),
+            r"../relative/path".into(),
+            r"..\win\relative\path".into(),
+            r"../path/with spaces/in/it".into(),
+            r"..\win\path\with spaces\in\it".into(),
+            r"path\with/mixed\separators".into(),
+        ]
+        .into_iter()
+        .collect();
+        assert_eq!(
+            spec.to_string(&deps),
+            "Mod\\ Name: \
+            ../path/with\\ spaces/in/it \
+            ../relative/path \
+            ..\\\\win\\\\path\\\\with\\ spaces\\\\in\\\\it \
+            ..\\\\win\\\\relative\\\\path \
+            /absolute/path \
+            C:\\\\win\\\\absolute\\\\path \
+            path\\\\with/mixed\\\\separators"
+        );
+    }
+}
diff --git a/third_party/rust/bindgen/diagnostics.rs b/third_party/rust/bindgen/diagnostics.rs
new file mode 100644
index 0000000000..f765afe970
--- /dev/null
+++ b/third_party/rust/bindgen/diagnostics.rs
@@ -0,0 +1,189 @@
+//! Types and function used to emit pretty diagnostics for `bindgen`.
+//!
+//! The entry point of this module is the [`Diagnostic`] type.
+
+use std::fmt::Write;
+use std::io::{self, BufRead, BufReader};
+use std::{borrow::Cow, fs::File};
+
+use annotate_snippets::{
+    display_list::{DisplayList, FormatOptions},
+    snippet::{Annotation, Slice as ExtSlice, Snippet},
+};
+
+use annotate_snippets::snippet::AnnotationType;
+
+#[derive(Clone, Copy, Debug)]
+pub(crate) enum Level {
+    Error,
+    Warn,
+    Info,
+    Note,
+    Help,
+}
+
+impl From<Level> for AnnotationType {
+    fn from(level: Level) -> Self {
+        match level {
+            Level::Error => Self::Error,
+            Level::Warn => Self::Warning,
+            Level::Info => Self::Info,
+            Level::Note => Self::Note,
+            Level::Help => Self::Help,
+        }
+    }
+}
+
+/// A `bindgen` diagnostic.
+#[derive(Default)]
+pub(crate) struct Diagnostic<'a> {
+    title: Option<(Cow<'a, str>, Level)>,
+    slices: Vec<Slice<'a>>,
+    footer: Vec<(Cow<'a, str>, Level)>,
+}
+
+impl<'a> Diagnostic<'a> {
+    /// Add a title to the diagnostic and set its type.
+    pub(crate) fn with_title(
+        &mut self,
+        title: impl Into<Cow<'a, str>>,
+        level: Level,
+    ) -> &mut Self {
+        self.title = Some((title.into(), level));
+        self
+    }
+
+    /// Add a slice of source code to the diagnostic.
+    pub(crate) fn add_slice(&mut self, slice: Slice<'a>) -> &mut Self {
+        self.slices.push(slice);
+        self
+    }
+
+    /// Add a footer annotation to the diagnostic. This annotation will have its own type.
+    pub(crate) fn add_annotation(
+        &mut self,
+        msg: impl Into<Cow<'a, str>>,
+        level: Level,
+    ) -> &mut Self {
+        self.footer.push((msg.into(), level));
+        self
+    }
+
+    /// Print this diagnostic.
+    ///
+    /// The diagnostic is printed using `cargo:warning` if `bindgen` is being invoked by a build
+    /// script or using `eprintln` otherwise.
+    pub(crate) fn display(&self) {
+        std::thread_local! {
+            static INVOKED_BY_BUILD_SCRIPT: bool =  std::env::var_os("CARGO_CFG_TARGET_ARCH").is_some();
+        }
+
+        let mut title = None;
+        let mut footer = vec![];
+        let mut slices = vec![];
+        if let Some((msg, level)) = &self.title {
+            title = Some(Annotation {
+                id: Some("bindgen"),
+                label: Some(msg.as_ref()),
+                annotation_type: (*level).into(),
+            })
+        }
+
+        for (msg, level) in &self.footer {
+            footer.push(Annotation {
+                id: None,
+                label: Some(msg.as_ref()),
+                annotation_type: (*level).into(),
+            });
+        }
+
+        // add additional info that this is generated by bindgen
+        // so as to not confuse with rustc warnings
+        footer.push(Annotation {
+            id: None,
+            label: Some("This diagnostic was generated by bindgen."),
+            annotation_type: AnnotationType::Info,
+        });
+
+        for slice in &self.slices {
+            if let Some(source) = &slice.source {
+                slices.push(ExtSlice {
+                    source: source.as_ref(),
+                    line_start: slice.line.unwrap_or_default(),
+                    origin: slice.filename.as_deref(),
+                    annotations: vec![],
+                    fold: false,
+                })
+            }
+        }
+
+        let snippet = Snippet {
+            title,
+            footer,
+            slices,
+            opt: FormatOptions {
+                color: true,
+                ..Default::default()
+            },
+        };
+        let dl = DisplayList::from(snippet);
+
+        if INVOKED_BY_BUILD_SCRIPT.with(Clone::clone) {
+            // This is just a hack which hides the `warning:` added by cargo at the beginning of
+            // every line. This should be fine as our diagnostics already have a colorful title.
+            // FIXME (pvdrz): Could it be that this doesn't work in other languages?
+            let hide_warning = "\r        \r";
+            let string = dl.to_string();
+            for line in string.lines() {
+                println!("cargo:warning={}{}", hide_warning, line);
+            }
+        } else {
+            eprintln!("{}\n", dl);
+        }
+    }
+}
+
+/// A slice of source code.
+#[derive(Default)]
+pub(crate) struct Slice<'a> {
+    source: Option<Cow<'a, str>>,
+    filename: Option<String>,
+    line: Option<usize>,
+}
+
+impl<'a> Slice<'a> {
+    /// Set the source code.
+    pub(crate) fn with_source(
+        &mut self,
+        source: impl Into<Cow<'a, str>>,
+    ) -> &mut Self {
+        self.source = Some(source.into());
+        self
+    }
+
+    /// Set the file, line and column.
+    pub(crate) fn with_location(
+        &mut self,
+        mut name: String,
+        line: usize,
+        col: usize,
+    ) -> &mut Self {
+        write!(name, ":{}:{}", line, col)
+            .expect("Writing to a string cannot fail");
+        self.filename = Some(name);
+        self.line = Some(line);
+        self
+    }
+}
+
+pub(crate) fn get_line(
+    filename: &str,
+    line: usize,
+) -> io::Result<Option<String>> {
+    let file = BufReader::new(File::open(filename)?);
+    if let Some(line) = file.lines().nth(line.wrapping_sub(1)) {
+        return line.map(Some);
+    }
+
+    Ok(None)
+}
diff --git a/third_party/rust/bindgen/extra_assertions.rs b/third_party/rust/bindgen/extra_assertions.rs
new file mode 100644
index 0000000000..fbddad7825
--- /dev/null
+++ b/third_party/rust/bindgen/extra_assertions.rs
@@ -0,0 +1,17 @@
+//! Macros for defining extra assertions that should only be checked in testing
+//! and/or CI when the `__testing_only_extra_assertions` feature is enabled.
+
+/// Simple macro that forwards to assert! when using
+/// __testing_only_extra_assertions.
+macro_rules! extra_assert {
+    ( $cond:expr ) => {
+        if cfg!(feature = "__testing_only_extra_assertions") {
+            assert!($cond);
+        }
+    };
+    ( $cond:expr , $( $arg:tt )+ ) => {
+        if cfg!(feature = "__testing_only_extra_assertions") {
+            assert!($cond, $( $arg )* )
+        }
+    };
+}
diff --git a/third_party/rust/bindgen/features.rs b/third_party/rust/bindgen/features.rs
new file mode 100644
index 0000000000..e5e2068053
--- /dev/null
+++ b/third_party/rust/bindgen/features.rs
@@ -0,0 +1,296 @@
+//! Contains code for selecting features
+
+#![deny(unused_extern_crates)]
+#![deny(clippy::missing_docs_in_private_items)]
+#![allow(deprecated)]
+
+use std::cmp::Ordering;
+use std::io;
+use std::str::FromStr;
+
+/// This macro defines the [`RustTarget`] and [`RustFeatures`] types.
+macro_rules! define_rust_targets {
+    (
+        Nightly => {$($nightly_feature:ident $(: #$issue:literal)?),* $(,)?} $(,)?
+        $(
+            $(#[$attrs:meta])*
+            $variant:ident($minor:literal) => {$($feature:ident $(: #$pull:literal)?),* $(,)?},
+        )*
+        $(,)?
+    ) => {
+        /// Represents the version of the Rust language to target.
+        ///
+        /// To support a beta release, use the corresponding stable release.
+        ///
+        /// This enum will have more variants added as necessary.
+        #[allow(non_camel_case_types)]
+        #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+        pub enum RustTarget {
+            /// Rust Nightly
+            $(#[doc = concat!(
+                "- [`", stringify!($nightly_feature), "`]",
+                "(", $("https://github.com/rust-lang/rust/pull/", stringify!($issue),)* ")",
+            )])*
+            Nightly,
+            $(
+                #[doc = concat!("Rust 1.", stringify!($minor))]
+                $(#[doc = concat!(
+                    "- [`", stringify!($feature), "`]",
+                    "(", $("https://github.com/rust-lang/rust/pull/", stringify!($pull),)* ")",
+                )])*
+                $(#[$attrs])*
+                $variant,
+            )*
+        }
+
+        impl RustTarget {
+            fn minor(self) -> Option<u64> {
+                match self {
+                    $( Self::$variant => Some($minor),)*
+                    Self::Nightly => None
+                }
+            }
+
+            const fn stable_releases() -> [(Self, u64); [$($minor,)*].len()] {
+                [$((Self::$variant, $minor),)*]
+            }
+        }
+
+        #[cfg(feature = "__cli")]
+        /// Strings of allowed `RustTarget` values
+        pub const RUST_TARGET_STRINGS: &[&str] = &[$(concat!("1.", stringify!($minor)),)*];
+
+        #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+        pub(crate) struct RustFeatures {
+            $($(pub(crate) $feature: bool,)*)*
+            $(pub(crate) $nightly_feature: bool,)*
+        }
+
+        impl From<RustTarget> for RustFeatures {
+            fn from(target: RustTarget) -> Self {
+                if target == RustTarget::Nightly {
+                    return Self {
+                        $($($feature: true,)*)*
+                        $($nightly_feature: true,)*
+                    };
+                }
+
+                let mut features = Self {
+                    $($($feature: false,)*)*
+                    $($nightly_feature: false,)*
+                };
+
+                $(if target >= RustTarget::$variant {
+                    $(features.$feature = true;)*
+                })*
+
+                features
+            }
+        }
+    };
+}
+
+// NOTE: When adding or removing features here, make sure to add the stabilization PR
+// number for the feature if it has been stabilized or the tracking issue number if the feature is
+// not stable.
+define_rust_targets! {
+    Nightly => {
+        vectorcall_abi,
+    },
+    Stable_1_73(73) => { thiscall_abi: #42202 },
+    Stable_1_71(71) => { c_unwind_abi: #106075 },
+    Stable_1_68(68) => { abi_efiapi: #105795 },
+    Stable_1_64(64) => { core_ffi_c: #94503 },
+    Stable_1_59(59) => { const_cstr: #54745 },
+    Stable_1_47(47) => { larger_arrays: #74060 },
+    Stable_1_40(40) => { non_exhaustive: #44109 },
+    Stable_1_36(36) => { maybe_uninit: #60445 },
+    Stable_1_33(33) => { repr_packed_n: #57049 },
+    #[deprecated]
+    Stable_1_30(30) => {
+        core_ffi_c_void: #53910,
+        min_const_fn: #54835,
+    },
+    #[deprecated]
+    Stable_1_28(28) => { repr_transparent: #51562 },
+    #[deprecated]
+    Stable_1_27(27) => { must_use_function: #48925 },
+    #[deprecated]
+    Stable_1_26(26) => { i128_and_u128: #49101 },
+    #[deprecated]
+    Stable_1_25(25) => { repr_align: #47006 },
+    #[deprecated]
+    Stable_1_21(21) => { builtin_clone_impls: #43690 },
+    #[deprecated]
+    Stable_1_20(20) => { associated_const: #42809 },
+    #[deprecated]
+    Stable_1_19(19) => { untagged_union: #42068 },
+    #[deprecated]
+    Stable_1_17(17) => { static_lifetime_elision: #39265 },
+    #[deprecated]
+    Stable_1_0(0) => {},
+}
+
+/// Latest stable release of Rust
+pub const LATEST_STABLE_RUST: RustTarget = {
+    // FIXME: replace all this code by
+    // ```
+    // RustTarget::stable_releases()
+    //     .into_iter()
+    //     .max_by_key(|(_, m)| m)
+    //     .map(|(t, _)| t)
+    //     .unwrap_or(RustTarget::Nightly)
+    // ```
+    // once those operations can be used in constants.
+    let targets = RustTarget::stable_releases();
+
+    let mut i = 0;
+    let mut latest_target = None;
+    let mut latest_minor = 0;
+
+    while i < targets.len() {
+        let (target, minor) = targets[i];
+
+        if latest_minor < minor {
+            latest_minor = minor;
+            latest_target = Some(target);
+        }
+
+        i += 1;
+    }
+
+    match latest_target {
+        Some(target) => target,
+        None => unreachable!(),
+    }
+};
+
+impl Default for RustTarget {
+    fn default() -> Self {
+        LATEST_STABLE_RUST
+    }
+}
+
+impl PartialOrd for RustTarget {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for RustTarget {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self.minor(), other.minor()) {
+            (Some(a), Some(b)) => a.cmp(&b),
+            (Some(_), None) => Ordering::Less,
+            (None, Some(_)) => Ordering::Greater,
+            (None, None) => Ordering::Equal,
+        }
+    }
+}
+
+impl FromStr for RustTarget {
+    type Err = io::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if s == "nightly" {
+            return Ok(Self::Nightly);
+        }
+
+        if let Some(("1", str_minor)) = s.split_once('.') {
+            if let Ok(minor) = str_minor.parse::<u64>() {
+                for (target, target_minor) in Self::stable_releases() {
+                    if minor == target_minor {
+                        return Ok(target);
+                    }
+                }
+            }
+        }
+
+        Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            "Got an invalid Rust target. Accepted values are of the form \"1.71\" or \"nightly\"."
+        ))
+    }
+}
+
+impl std::fmt::Display for RustTarget {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self.minor() {
+            Some(minor) => write!(f, "1.{}", minor),
+            None => "nightly".fmt(f),
+        }
+    }
+}
+
+impl Default for RustFeatures {
+    fn default() -> Self {
+        RustTarget::default().into()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #![allow(unused_imports)]
+    use super::*;
+
+    #[test]
+    fn target_features() {
+        let f_1_0 = RustFeatures::from(RustTarget::Stable_1_0);
+        assert!(
+            !f_1_0.static_lifetime_elision &&
+                !f_1_0.core_ffi_c_void &&
+                !f_1_0.untagged_union &&
+                !f_1_0.associated_const &&
+                !f_1_0.builtin_clone_impls &&
+                !f_1_0.repr_align &&
+                !f_1_0.thiscall_abi &&
+                !f_1_0.vectorcall_abi
+        );
+        let f_1_21 = RustFeatures::from(RustTarget::Stable_1_21);
+        assert!(
+            f_1_21.static_lifetime_elision &&
+                !f_1_21.core_ffi_c_void &&
+                f_1_21.untagged_union &&
+                f_1_21.associated_const &&
+                f_1_21.builtin_clone_impls &&
+                !f_1_21.repr_align &&
+                !f_1_21.thiscall_abi &&
+                !f_1_21.vectorcall_abi
+        );
+        let features = RustFeatures::from(RustTarget::Stable_1_71);
+        assert!(
+            features.c_unwind_abi &&
+                features.abi_efiapi &&
+                !features.thiscall_abi
+        );
+        let f_nightly = RustFeatures::from(RustTarget::Nightly);
+        assert!(
+            f_nightly.static_lifetime_elision &&
+                f_nightly.core_ffi_c_void &&
+                f_nightly.untagged_union &&
+                f_nightly.associated_const &&
+                f_nightly.builtin_clone_impls &&
+                f_nightly.maybe_uninit &&
+                f_nightly.repr_align &&
+                f_nightly.thiscall_abi &&
+                f_nightly.vectorcall_abi
+        );
+    }
+
+    fn test_target(target_str: &str, target: RustTarget) {
+        let target_string = target.to_string();
+        assert_eq!(target_str, target_string);
+        assert_eq!(target, RustTarget::from_str(target_str).unwrap());
+    }
+
+    #[test]
+    fn str_to_target() {
+        test_target("1.0", RustTarget::Stable_1_0);
+        test_target("1.17", RustTarget::Stable_1_17);
+        test_target("1.19", RustTarget::Stable_1_19);
+        test_target("1.21", RustTarget::Stable_1_21);
+        test_target("1.25", RustTarget::Stable_1_25);
+        test_target("1.71", RustTarget::Stable_1_71);
+        test_target("nightly", RustTarget::Nightly);
+    }
+}
diff --git a/third_party/rust/bindgen/ir/analysis/derive.rs b/third_party/rust/bindgen/ir/analysis/derive.rs
new file mode 100644
index 0000000000..d8d29ed9a8
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/derive.rs
@@ -0,0 +1,732 @@
+//! Determining which types for which we cannot emit `#[derive(Trait)]`.
+
+use std::fmt;
+
+use super::{generate_dependencies, ConstrainResult, MonotoneFramework};
+use crate::ir::analysis::has_vtable::HasVtable;
+use crate::ir::comp::CompKind;
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::derive::CanDerive;
+use crate::ir::function::FunctionSig;
+use crate::ir::item::{IsOpaque, Item};
+use crate::ir::layout::Layout;
+use crate::ir::template::TemplateParameters;
+use crate::ir::traversal::{EdgeKind, Trace};
+use crate::ir::ty::RUST_DERIVE_IN_ARRAY_LIMIT;
+use crate::ir::ty::{Type, TypeKind};
+use crate::{Entry, HashMap, HashSet};
+
+/// Which trait to consider when doing the `CannotDerive` analysis.
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+pub enum DeriveTrait {
+    /// The `Copy` trait.
+    Copy,
+    /// The `Debug` trait.
+    Debug,
+    /// The `Default` trait.
+    Default,
+    /// The `Hash` trait.
+    Hash,
+    /// The `PartialEq` and `PartialOrd` traits.
+    PartialEqOrPartialOrd,
+}
+
+/// An analysis that finds for each IR item whether a trait cannot be derived.
+///
+/// We use the monotone constraint function `cannot_derive`, defined as follows
+/// for type T:
+///
+/// * If T is Opaque and the layout of the type is known, get this layout as an
+///   opaquetype and check whether it can derive using trivial checks.
+///
+/// * If T is Array, a trait cannot be derived if the array is incomplete,
+///   if the length of the array is larger than the limit (unless the trait
+///   allows it), or the trait cannot be derived for the type of data the array
+///   contains.
+///
+/// * If T is Vector, a trait cannot be derived if the trait cannot be derived
+///   for the type of data the vector contains.
+///
+/// * If T is a type alias, a templated alias or an indirection to another type,
+///   the trait cannot be derived if the trait cannot be derived for type T
+///   refers to.
+///
+/// * If T is a compound type, the trait cannot be derived if the trait cannot
+///   be derived for any of its base members or fields.
+///
+/// * If T is an instantiation of an abstract template definition, the trait
+///   cannot be derived if any of the template arguments or template definition
+///   cannot derive the trait.
+///
+/// * For all other (simple) types, compiler and standard library limitations
+///   dictate whether the trait is implemented.
+#[derive(Debug, Clone)]
+pub(crate) struct CannotDerive<'ctx> {
+    ctx: &'ctx BindgenContext,
+
+    derive_trait: DeriveTrait,
+
+    // The incremental result of this analysis's computation.
+    // Contains information whether particular item can derive `derive_trait`
+    can_derive: HashMap<ItemId, CanDerive>,
+
+    // Dependencies saying that if a key ItemId has been inserted into the
+    // `cannot_derive_partialeq_or_partialord` set, then each of the ids
+    // in Vec<ItemId> need to be considered again.
+    //
+    // This is a subset of the natural IR graph with reversed edges, where we
+    // only include the edges from the IR graph that can affect whether a type
+    // can derive `derive_trait`.
+    dependencies: HashMap<ItemId, Vec<ItemId>>,
+}
+
+type EdgePredicate = fn(EdgeKind) -> bool;
+
+fn consider_edge_default(kind: EdgeKind) -> bool {
+    match kind {
+        // These are the only edges that can affect whether a type can derive
+        EdgeKind::BaseMember |
+        EdgeKind::Field |
+        EdgeKind::TypeReference |
+        EdgeKind::VarType |
+        EdgeKind::TemplateArgument |
+        EdgeKind::TemplateDeclaration |
+        EdgeKind::TemplateParameterDefinition => true,
+
+        EdgeKind::Constructor |
+        EdgeKind::Destructor |
+        EdgeKind::FunctionReturn |
+        EdgeKind::FunctionParameter |
+        EdgeKind::InnerType |
+        EdgeKind::InnerVar |
+        EdgeKind::Method |
+        EdgeKind::Generic => false,
+    }
+}
+
+impl<'ctx> CannotDerive<'ctx> {
+    fn insert<Id: Into<ItemId>>(
+        &mut self,
+        id: Id,
+        can_derive: CanDerive,
+    ) -> ConstrainResult {
+        let id = id.into();
+        trace!(
+            "inserting {:?} can_derive<{}>={:?}",
+            id,
+            self.derive_trait,
+            can_derive
+        );
+
+        if let CanDerive::Yes = can_derive {
+            return ConstrainResult::Same;
+        }
+
+        match self.can_derive.entry(id) {
+            Entry::Occupied(mut entry) => {
+                if *entry.get() < can_derive {
+                    entry.insert(can_derive);
+                    ConstrainResult::Changed
+                } else {
+                    ConstrainResult::Same
+                }
+            }
+            Entry::Vacant(entry) => {
+                entry.insert(can_derive);
+                ConstrainResult::Changed
+            }
+        }
+    }
+
+    fn constrain_type(&mut self, item: &Item, ty: &Type) -> CanDerive {
+        if !self.ctx.allowlisted_items().contains(&item.id()) {
+            let can_derive = self
+                .ctx
+                .blocklisted_type_implements_trait(item, self.derive_trait);
+            match can_derive {
+                CanDerive::Yes => trace!(
+                    "    blocklisted type explicitly implements {}",
+                    self.derive_trait
+                ),
+                CanDerive::Manually => trace!(
+                    "    blocklisted type requires manual implementation of {}",
+                    self.derive_trait
+                ),
+                CanDerive::No => trace!(
+                    "    cannot derive {} for blocklisted type",
+                    self.derive_trait
+                ),
+            }
+            return can_derive;
+        }
+
+        if self.derive_trait.not_by_name(self.ctx, item) {
+            trace!(
+                "    cannot derive {} for explicitly excluded type",
+                self.derive_trait
+            );
+            return CanDerive::No;
+        }
+
+        trace!("ty: {:?}", ty);
+        if item.is_opaque(self.ctx, &()) {
+            if !self.derive_trait.can_derive_union() &&
+                ty.is_union() &&
+                self.ctx.options().untagged_union
+            {
+                trace!(
+                    "    cannot derive {} for Rust unions",
+                    self.derive_trait
+                );
+                return CanDerive::No;
+            }
+
+            let layout_can_derive =
+                ty.layout(self.ctx).map_or(CanDerive::Yes, |l| {
+                    l.opaque().array_size_within_derive_limit(self.ctx)
+                });
+
+            match layout_can_derive {
+                CanDerive::Yes => {
+                    trace!(
+                        "    we can trivially derive {} for the layout",
+                        self.derive_trait
+                    );
+                }
+                _ => {
+                    trace!(
+                        "    we cannot derive {} for the layout",
+                        self.derive_trait
+                    );
+                }
+            };
+            return layout_can_derive;
+        }
+
+        match *ty.kind() {
+            // Handle the simple cases. These can derive traits without further
+            // information.
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Int(..) |
+            TypeKind::Complex(..) |
+            TypeKind::Float(..) |
+            TypeKind::Enum(..) |
+            TypeKind::TypeParam |
+            TypeKind::UnresolvedTypeRef(..) |
+            TypeKind::Reference(..) |
+            TypeKind::ObjCInterface(..) |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel => {
+                return self.derive_trait.can_derive_simple(ty.kind());
+            }
+            TypeKind::Pointer(inner) => {
+                let inner_type =
+                    self.ctx.resolve_type(inner).canonical_type(self.ctx);
+                if let TypeKind::Function(ref sig) = *inner_type.kind() {
+                    self.derive_trait.can_derive_fnptr(sig)
+                } else {
+                    self.derive_trait.can_derive_pointer()
+                }
+            }
+            TypeKind::Function(ref sig) => {
+                self.derive_trait.can_derive_fnptr(sig)
+            }
+
+            // Complex cases need more information
+            TypeKind::Array(t, len) => {
+                let inner_type =
+                    self.can_derive.get(&t.into()).cloned().unwrap_or_default();
+                if inner_type != CanDerive::Yes {
+                    trace!(
+                        "    arrays of T for which we cannot derive {} \
+                         also cannot derive {}",
+                        self.derive_trait,
+                        self.derive_trait
+                    );
+                    return CanDerive::No;
+                }
+
+                if len == 0 && !self.derive_trait.can_derive_incomplete_array()
+                {
+                    trace!(
+                        "    cannot derive {} for incomplete arrays",
+                        self.derive_trait
+                    );
+                    return CanDerive::No;
+                }
+
+                if self.derive_trait.can_derive_large_array(self.ctx) {
+                    trace!("    array can derive {}", self.derive_trait);
+                    return CanDerive::Yes;
+                }
+
+                if len > RUST_DERIVE_IN_ARRAY_LIMIT {
+                    trace!(
+                        "    array is too large to derive {}, but it may be implemented", self.derive_trait
+                    );
+                    return CanDerive::Manually;
+                }
+                trace!(
+                    "    array is small enough to derive {}",
+                    self.derive_trait
+                );
+                CanDerive::Yes
+            }
+            TypeKind::Vector(t, len) => {
+                let inner_type =
+                    self.can_derive.get(&t.into()).cloned().unwrap_or_default();
+                if inner_type != CanDerive::Yes {
+                    trace!(
+                        "    vectors of T for which we cannot derive {} \
+                         also cannot derive {}",
+                        self.derive_trait,
+                        self.derive_trait
+                    );
+                    return CanDerive::No;
+                }
+                assert_ne!(len, 0, "vectors cannot have zero length");
+                self.derive_trait.can_derive_vector()
+            }
+
+            TypeKind::Comp(ref info) => {
+                assert!(
+                    !info.has_non_type_template_params(),
+                    "The early ty.is_opaque check should have handled this case"
+                );
+
+                if !self.derive_trait.can_derive_compound_forward_decl() &&
+                    info.is_forward_declaration()
+                {
+                    trace!(
+                        "    cannot derive {} for forward decls",
+                        self.derive_trait
+                    );
+                    return CanDerive::No;
+                }
+
+                // NOTE: Take into account that while unions in C and C++ are copied by
+                // default, the may have an explicit destructor in C++, so we can't
+                // defer this check just for the union case.
+                if !self.derive_trait.can_derive_compound_with_destructor() &&
+                    self.ctx.lookup_has_destructor(
+                        item.id().expect_type_id(self.ctx),
+                    )
+                {
+                    trace!(
+                        "    comp has destructor which cannot derive {}",
+                        self.derive_trait
+                    );
+                    return CanDerive::No;
+                }
+
+                if info.kind() == CompKind::Union {
+                    if self.derive_trait.can_derive_union() {
+                        if self.ctx.options().untagged_union &&
+                           // https://github.com/rust-lang/rust/issues/36640
+                           (!info.self_template_params(self.ctx).is_empty() ||
+                            !item.all_template_params(self.ctx).is_empty())
+                        {
+                            trace!(
+                                "    cannot derive {} for Rust union because issue 36640", self.derive_trait
+                            );
+                            return CanDerive::No;
+                        }
+                    // fall through to be same as non-union handling
+                    } else {
+                        if self.ctx.options().untagged_union {
+                            trace!(
+                                "    cannot derive {} for Rust unions",
+                                self.derive_trait
+                            );
+                            return CanDerive::No;
+                        }
+
+                        let layout_can_derive =
+                            ty.layout(self.ctx).map_or(CanDerive::Yes, |l| {
+                                l.opaque()
+                                    .array_size_within_derive_limit(self.ctx)
+                            });
+                        match layout_can_derive {
+                            CanDerive::Yes => {
+                                trace!(
+                                    "    union layout can trivially derive {}",
+                                    self.derive_trait
+                                );
+                            }
+                            _ => {
+                                trace!(
+                                    "    union layout cannot derive {}",
+                                    self.derive_trait
+                                );
+                            }
+                        };
+                        return layout_can_derive;
+                    }
+                }
+
+                if !self.derive_trait.can_derive_compound_with_vtable() &&
+                    item.has_vtable(self.ctx)
+                {
+                    trace!(
+                        "    cannot derive {} for comp with vtable",
+                        self.derive_trait
+                    );
+                    return CanDerive::No;
+                }
+
+                // Bitfield units are always represented as arrays of u8, but
+                // they're not traced as arrays, so we need to check here
+                // instead.
+                if !self.derive_trait.can_derive_large_array(self.ctx) &&
+                    info.has_too_large_bitfield_unit() &&
+                    !item.is_opaque(self.ctx, &())
+                {
+                    trace!(
+                        "    cannot derive {} for comp with too large bitfield unit",
+                        self.derive_trait
+                    );
+                    return CanDerive::No;
+                }
+
+                let pred = self.derive_trait.consider_edge_comp();
+                self.constrain_join(item, pred)
+            }
+
+            TypeKind::ResolvedTypeRef(..) |
+            TypeKind::TemplateAlias(..) |
+            TypeKind::Alias(..) |
+            TypeKind::BlockPointer(..) => {
+                let pred = self.derive_trait.consider_edge_typeref();
+                self.constrain_join(item, pred)
+            }
+
+            TypeKind::TemplateInstantiation(..) => {
+                let pred = self.derive_trait.consider_edge_tmpl_inst();
+                self.constrain_join(item, pred)
+            }
+
+            TypeKind::Opaque => unreachable!(
+                "The early ty.is_opaque check should have handled this case"
+            ),
+        }
+    }
+
+    fn constrain_join(
+        &mut self,
+        item: &Item,
+        consider_edge: EdgePredicate,
+    ) -> CanDerive {
+        let mut candidate = None;
+
+        item.trace(
+            self.ctx,
+            &mut |sub_id, edge_kind| {
+                // Ignore ourselves, since union with ourself is a
+                // no-op. Ignore edges that aren't relevant to the
+                // analysis.
+                if sub_id == item.id() || !consider_edge(edge_kind) {
+                    return;
+                }
+
+                let can_derive = self.can_derive
+                    .get(&sub_id)
+                    .cloned()
+                    .unwrap_or_default();
+
+                match can_derive {
+                    CanDerive::Yes => trace!("    member {:?} can derive {}", sub_id, self.derive_trait),
+                    CanDerive::Manually => trace!("    member {:?} cannot derive {}, but it may be implemented", sub_id, self.derive_trait),
+                    CanDerive::No => trace!("    member {:?} cannot derive {}", sub_id, self.derive_trait),
+                }
+
+                *candidate.get_or_insert(CanDerive::Yes) |= can_derive;
+            },
+            &(),
+        );
+
+        if candidate.is_none() {
+            trace!(
+                "    can derive {} because there are no members",
+                self.derive_trait
+            );
+        }
+        candidate.unwrap_or_default()
+    }
+}
+
+impl DeriveTrait {
+    fn not_by_name(&self, ctx: &BindgenContext, item: &Item) -> bool {
+        match self {
+            DeriveTrait::Copy => ctx.no_copy_by_name(item),
+            DeriveTrait::Debug => ctx.no_debug_by_name(item),
+            DeriveTrait::Default => ctx.no_default_by_name(item),
+            DeriveTrait::Hash => ctx.no_hash_by_name(item),
+            DeriveTrait::PartialEqOrPartialOrd => {
+                ctx.no_partialeq_by_name(item)
+            }
+        }
+    }
+
+    fn consider_edge_comp(&self) -> EdgePredicate {
+        match self {
+            DeriveTrait::PartialEqOrPartialOrd => consider_edge_default,
+            _ => |kind| matches!(kind, EdgeKind::BaseMember | EdgeKind::Field),
+        }
+    }
+
+    fn consider_edge_typeref(&self) -> EdgePredicate {
+        match self {
+            DeriveTrait::PartialEqOrPartialOrd => consider_edge_default,
+            _ => |kind| kind == EdgeKind::TypeReference,
+        }
+    }
+
+    fn consider_edge_tmpl_inst(&self) -> EdgePredicate {
+        match self {
+            DeriveTrait::PartialEqOrPartialOrd => consider_edge_default,
+            _ => |kind| {
+                matches!(
+                    kind,
+                    EdgeKind::TemplateArgument | EdgeKind::TemplateDeclaration
+                )
+            },
+        }
+    }
+
+    fn can_derive_large_array(&self, ctx: &BindgenContext) -> bool {
+        if ctx.options().rust_features().larger_arrays {
+            !matches!(self, DeriveTrait::Default)
+        } else {
+            matches!(self, DeriveTrait::Copy)
+        }
+    }
+
+    fn can_derive_union(&self) -> bool {
+        matches!(self, DeriveTrait::Copy)
+    }
+
+    fn can_derive_compound_with_destructor(&self) -> bool {
+        !matches!(self, DeriveTrait::Copy)
+    }
+
+    fn can_derive_compound_with_vtable(&self) -> bool {
+        !matches!(self, DeriveTrait::Default)
+    }
+
+    fn can_derive_compound_forward_decl(&self) -> bool {
+        matches!(self, DeriveTrait::Copy | DeriveTrait::Debug)
+    }
+
+    fn can_derive_incomplete_array(&self) -> bool {
+        !matches!(
+            self,
+            DeriveTrait::Copy |
+                DeriveTrait::Hash |
+                DeriveTrait::PartialEqOrPartialOrd
+        )
+    }
+
+    fn can_derive_fnptr(&self, f: &FunctionSig) -> CanDerive {
+        match (self, f.function_pointers_can_derive()) {
+            (DeriveTrait::Copy, _) | (DeriveTrait::Default, _) | (_, true) => {
+                trace!("    function pointer can derive {}", self);
+                CanDerive::Yes
+            }
+            (DeriveTrait::Debug, false) => {
+                trace!("    function pointer cannot derive {}, but it may be implemented", self);
+                CanDerive::Manually
+            }
+            (_, false) => {
+                trace!("    function pointer cannot derive {}", self);
+                CanDerive::No
+            }
+        }
+    }
+
+    fn can_derive_vector(&self) -> CanDerive {
+        match self {
+            DeriveTrait::PartialEqOrPartialOrd => {
+                // FIXME: vectors always can derive PartialEq, but they should
+                // not derive PartialOrd:
+                // https://github.com/rust-lang-nursery/packed_simd/issues/48
+                trace!("    vectors cannot derive PartialOrd");
+                CanDerive::No
+            }
+            _ => {
+                trace!("    vector can derive {}", self);
+                CanDerive::Yes
+            }
+        }
+    }
+
+    fn can_derive_pointer(&self) -> CanDerive {
+        match self {
+            DeriveTrait::Default => {
+                trace!("    pointer cannot derive Default");
+                CanDerive::No
+            }
+            _ => {
+                trace!("    pointer can derive {}", self);
+                CanDerive::Yes
+            }
+        }
+    }
+
+    fn can_derive_simple(&self, kind: &TypeKind) -> CanDerive {
+        match (self, kind) {
+            // === Default ===
+            (DeriveTrait::Default, TypeKind::Void) |
+            (DeriveTrait::Default, TypeKind::NullPtr) |
+            (DeriveTrait::Default, TypeKind::Enum(..)) |
+            (DeriveTrait::Default, TypeKind::Reference(..)) |
+            (DeriveTrait::Default, TypeKind::TypeParam) |
+            (DeriveTrait::Default, TypeKind::ObjCInterface(..)) |
+            (DeriveTrait::Default, TypeKind::ObjCId) |
+            (DeriveTrait::Default, TypeKind::ObjCSel) => {
+                trace!("    types that always cannot derive Default");
+                CanDerive::No
+            }
+            (DeriveTrait::Default, TypeKind::UnresolvedTypeRef(..)) => {
+                unreachable!(
+                    "Type with unresolved type ref can't reach derive default"
+                )
+            }
+            // === Hash ===
+            (DeriveTrait::Hash, TypeKind::Float(..)) |
+            (DeriveTrait::Hash, TypeKind::Complex(..)) => {
+                trace!("    float cannot derive Hash");
+                CanDerive::No
+            }
+            // === others ===
+            _ => {
+                trace!("    simple type that can always derive {}", self);
+                CanDerive::Yes
+            }
+        }
+    }
+}
+
+impl fmt::Display for DeriveTrait {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let s = match self {
+            DeriveTrait::Copy => "Copy",
+            DeriveTrait::Debug => "Debug",
+            DeriveTrait::Default => "Default",
+            DeriveTrait::Hash => "Hash",
+            DeriveTrait::PartialEqOrPartialOrd => "PartialEq/PartialOrd",
+        };
+        s.fmt(f)
+    }
+}
+
+impl<'ctx> MonotoneFramework for CannotDerive<'ctx> {
+    type Node = ItemId;
+    type Extra = (&'ctx BindgenContext, DeriveTrait);
+    type Output = HashMap<ItemId, CanDerive>;
+
+    fn new(
+        (ctx, derive_trait): (&'ctx BindgenContext, DeriveTrait),
+    ) -> CannotDerive<'ctx> {
+        let can_derive = HashMap::default();
+        let dependencies = generate_dependencies(ctx, consider_edge_default);
+
+        CannotDerive {
+            ctx,
+            derive_trait,
+            can_derive,
+            dependencies,
+        }
+    }
+
+    fn initial_worklist(&self) -> Vec<ItemId> {
+        // The transitive closure of all allowlisted items, including explicitly
+        // blocklisted items.
+        self.ctx
+            .allowlisted_items()
+            .iter()
+            .cloned()
+            .flat_map(|i| {
+                let mut reachable = vec![i];
+                i.trace(
+                    self.ctx,
+                    &mut |s, _| {
+                        reachable.push(s);
+                    },
+                    &(),
+                );
+                reachable
+            })
+            .collect()
+    }
+
+    fn constrain(&mut self, id: ItemId) -> ConstrainResult {
+        trace!("constrain: {:?}", id);
+
+        if let Some(CanDerive::No) = self.can_derive.get(&id).cloned() {
+            trace!("    already know it cannot derive {}", self.derive_trait);
+            return ConstrainResult::Same;
+        }
+
+        let item = self.ctx.resolve_item(id);
+        let can_derive = match item.as_type() {
+            Some(ty) => {
+                let mut can_derive = self.constrain_type(item, ty);
+                if let CanDerive::Yes = can_derive {
+                    let is_reached_limit =
+                        |l: Layout| l.align > RUST_DERIVE_IN_ARRAY_LIMIT;
+                    if !self.derive_trait.can_derive_large_array(self.ctx) &&
+                        ty.layout(self.ctx).map_or(false, is_reached_limit)
+                    {
+                        // We have to be conservative: the struct *could* have enough
+                        // padding that we emit an array that is longer than
+                        // `RUST_DERIVE_IN_ARRAY_LIMIT`. If we moved padding calculations
+                        // into the IR and computed them before this analysis, then we could
+                        // be precise rather than conservative here.
+                        can_derive = CanDerive::Manually;
+                    }
+                }
+                can_derive
+            }
+            None => self.constrain_join(item, consider_edge_default),
+        };
+
+        self.insert(id, can_derive)
+    }
+
+    fn each_depending_on<F>(&self, id: ItemId, mut f: F)
+    where
+        F: FnMut(ItemId),
+    {
+        if let Some(edges) = self.dependencies.get(&id) {
+            for item in edges {
+                trace!("enqueue {:?} into worklist", item);
+                f(*item);
+            }
+        }
+    }
+}
+
+impl<'ctx> From<CannotDerive<'ctx>> for HashMap<ItemId, CanDerive> {
+    fn from(analysis: CannotDerive<'ctx>) -> Self {
+        extra_assert!(analysis
+            .can_derive
+            .values()
+            .all(|v| *v != CanDerive::Yes));
+
+        analysis.can_derive
+    }
+}
+
+/// Convert a `HashMap<ItemId, CanDerive>` into a `HashSet<ItemId>`.
+///
+/// Elements that are not `CanDerive::Yes` are kept in the set, so that it
+/// represents all items that cannot derive.
+pub(crate) fn as_cannot_derive_set(
+    can_derive: HashMap<ItemId, CanDerive>,
+) -> HashSet<ItemId> {
+    can_derive
+        .into_iter()
+        .filter_map(|(k, v)| if v != CanDerive::Yes { Some(k) } else { None })
+        .collect()
+}
diff --git a/third_party/rust/bindgen/ir/analysis/has_destructor.rs b/third_party/rust/bindgen/ir/analysis/has_destructor.rs
new file mode 100644
index 0000000000..cbcbe55af2
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/has_destructor.rs
@@ -0,0 +1,176 @@
+//! Determining which types have destructors
+
+use super::{generate_dependencies, ConstrainResult, MonotoneFramework};
+use crate::ir::comp::{CompKind, Field, FieldMethods};
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::traversal::EdgeKind;
+use crate::ir::ty::TypeKind;
+use crate::{HashMap, HashSet};
+
+/// An analysis that finds for each IR item whether it has a destructor or not
+///
+/// We use the monotone function `has destructor`, defined as follows:
+///
+/// * If T is a type alias, a templated alias, or an indirection to another type,
+///   T has a destructor if the type T refers to has a destructor.
+/// * If T is a compound type, T has a destructor if we saw a destructor when parsing it,
+///   or if it's a struct, T has a destructor if any of its base members has a destructor,
+///   or if any of its fields have a destructor.
+/// * If T is an instantiation of an abstract template definition, T has
+///   a destructor if its template definition has a destructor,
+///   or if any of the template arguments has a destructor.
+/// * If T is the type of a field, that field has a destructor if it's not a bitfield,
+///   and if T has a destructor.
+#[derive(Debug, Clone)]
+pub(crate) struct HasDestructorAnalysis<'ctx> {
+    ctx: &'ctx BindgenContext,
+
+    // The incremental result of this analysis's computation. Everything in this
+    // set definitely has a destructor.
+    have_destructor: HashSet<ItemId>,
+
+    // Dependencies saying that if a key ItemId has been inserted into the
+    // `have_destructor` set, then each of the ids in Vec<ItemId> need to be
+    // considered again.
+    //
+    // This is a subset of the natural IR graph with reversed edges, where we
+    // only include the edges from the IR graph that can affect whether a type
+    // has a destructor or not.
+    dependencies: HashMap<ItemId, Vec<ItemId>>,
+}
+
+impl<'ctx> HasDestructorAnalysis<'ctx> {
+    fn consider_edge(kind: EdgeKind) -> bool {
+        // These are the only edges that can affect whether a type has a
+        // destructor or not.
+        matches!(
+            kind,
+            EdgeKind::TypeReference |
+                EdgeKind::BaseMember |
+                EdgeKind::Field |
+                EdgeKind::TemplateArgument |
+                EdgeKind::TemplateDeclaration
+        )
+    }
+
+    fn insert<Id: Into<ItemId>>(&mut self, id: Id) -> ConstrainResult {
+        let id = id.into();
+        let was_not_already_in_set = self.have_destructor.insert(id);
+        assert!(
+            was_not_already_in_set,
+            "We shouldn't try and insert {:?} twice because if it was \
+             already in the set, `constrain` should have exited early.",
+            id
+        );
+        ConstrainResult::Changed
+    }
+}
+
+impl<'ctx> MonotoneFramework for HasDestructorAnalysis<'ctx> {
+    type Node = ItemId;
+    type Extra = &'ctx BindgenContext;
+    type Output = HashSet<ItemId>;
+
+    fn new(ctx: &'ctx BindgenContext) -> Self {
+        let have_destructor = HashSet::default();
+        let dependencies = generate_dependencies(ctx, Self::consider_edge);
+
+        HasDestructorAnalysis {
+            ctx,
+            have_destructor,
+            dependencies,
+        }
+    }
+
+    fn initial_worklist(&self) -> Vec<ItemId> {
+        self.ctx.allowlisted_items().iter().cloned().collect()
+    }
+
+    fn constrain(&mut self, id: ItemId) -> ConstrainResult {
+        if self.have_destructor.contains(&id) {
+            // We've already computed that this type has a destructor and that can't
+            // change.
+            return ConstrainResult::Same;
+        }
+
+        let item = self.ctx.resolve_item(id);
+        let ty = match item.as_type() {
+            None => return ConstrainResult::Same,
+            Some(ty) => ty,
+        };
+
+        match *ty.kind() {
+            TypeKind::TemplateAlias(t, _) |
+            TypeKind::Alias(t) |
+            TypeKind::ResolvedTypeRef(t) => {
+                if self.have_destructor.contains(&t.into()) {
+                    self.insert(id)
+                } else {
+                    ConstrainResult::Same
+                }
+            }
+
+            TypeKind::Comp(ref info) => {
+                if info.has_own_destructor() {
+                    return self.insert(id);
+                }
+
+                match info.kind() {
+                    CompKind::Union => ConstrainResult::Same,
+                    CompKind::Struct => {
+                        let base_or_field_destructor =
+                            info.base_members().iter().any(|base| {
+                                self.have_destructor.contains(&base.ty.into())
+                            }) || info.fields().iter().any(
+                                |field| match *field {
+                                    Field::DataMember(ref data) => self
+                                        .have_destructor
+                                        .contains(&data.ty().into()),
+                                    Field::Bitfields(_) => false,
+                                },
+                            );
+                        if base_or_field_destructor {
+                            self.insert(id)
+                        } else {
+                            ConstrainResult::Same
+                        }
+                    }
+                }
+            }
+
+            TypeKind::TemplateInstantiation(ref inst) => {
+                let definition_or_arg_destructor = self
+                    .have_destructor
+                    .contains(&inst.template_definition().into()) ||
+                    inst.template_arguments().iter().any(|arg| {
+                        self.have_destructor.contains(&arg.into())
+                    });
+                if definition_or_arg_destructor {
+                    self.insert(id)
+                } else {
+                    ConstrainResult::Same
+                }
+            }
+
+            _ => ConstrainResult::Same,
+        }
+    }
+
+    fn each_depending_on<F>(&self, id: ItemId, mut f: F)
+    where
+        F: FnMut(ItemId),
+    {
+        if let Some(edges) = self.dependencies.get(&id) {
+            for item in edges {
+                trace!("enqueue {:?} into worklist", item);
+                f(*item);
+            }
+        }
+    }
+}
+
+impl<'ctx> From<HasDestructorAnalysis<'ctx>> for HashSet<ItemId> {
+    fn from(analysis: HasDestructorAnalysis<'ctx>) -> Self {
+        analysis.have_destructor
+    }
+}
diff --git a/third_party/rust/bindgen/ir/analysis/has_float.rs b/third_party/rust/bindgen/ir/analysis/has_float.rs
new file mode 100644
index 0000000000..219c5a5a8d
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/has_float.rs
@@ -0,0 +1,252 @@
+//! Determining which types has float.
+
+use super::{generate_dependencies, ConstrainResult, MonotoneFramework};
+use crate::ir::comp::Field;
+use crate::ir::comp::FieldMethods;
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::traversal::EdgeKind;
+use crate::ir::ty::TypeKind;
+use crate::{HashMap, HashSet};
+
+/// An analysis that finds for each IR item whether it has float or not.
+///
+/// We use the monotone constraint function `has_float`,
+/// defined as follows:
+///
+/// * If T is float or complex float, T trivially has.
+/// * If T is a type alias, a templated alias or an indirection to another type,
+///   it has float if the type T refers to has.
+/// * If T is a compound type, it has float if any of base memter or field
+///   has.
+/// * If T is an instantiation of an abstract template definition, T has
+///   float if any of the template arguments or template definition
+///   has.
+#[derive(Debug, Clone)]
+pub(crate) struct HasFloat<'ctx> {
+    ctx: &'ctx BindgenContext,
+
+    // The incremental result of this analysis's computation. Everything in this
+    // set has float.
+    has_float: HashSet<ItemId>,
+
+    // Dependencies saying that if a key ItemId has been inserted into the
+    // `has_float` set, then each of the ids in Vec<ItemId> need to be
+    // considered again.
+    //
+    // This is a subset of the natural IR graph with reversed edges, where we
+    // only include the edges from the IR graph that can affect whether a type
+    // has float or not.
+    dependencies: HashMap<ItemId, Vec<ItemId>>,
+}
+
+impl<'ctx> HasFloat<'ctx> {
+    fn consider_edge(kind: EdgeKind) -> bool {
+        match kind {
+            EdgeKind::BaseMember |
+            EdgeKind::Field |
+            EdgeKind::TypeReference |
+            EdgeKind::VarType |
+            EdgeKind::TemplateArgument |
+            EdgeKind::TemplateDeclaration |
+            EdgeKind::TemplateParameterDefinition => true,
+
+            EdgeKind::Constructor |
+            EdgeKind::Destructor |
+            EdgeKind::FunctionReturn |
+            EdgeKind::FunctionParameter |
+            EdgeKind::InnerType |
+            EdgeKind::InnerVar |
+            EdgeKind::Method => false,
+            EdgeKind::Generic => false,
+        }
+    }
+
+    fn insert<Id: Into<ItemId>>(&mut self, id: Id) -> ConstrainResult {
+        let id = id.into();
+        trace!("inserting {:?} into the has_float set", id);
+
+        let was_not_already_in_set = self.has_float.insert(id);
+        assert!(
+            was_not_already_in_set,
+            "We shouldn't try and insert {:?} twice because if it was \
+             already in the set, `constrain` should have exited early.",
+            id
+        );
+
+        ConstrainResult::Changed
+    }
+}
+
+impl<'ctx> MonotoneFramework for HasFloat<'ctx> {
+    type Node = ItemId;
+    type Extra = &'ctx BindgenContext;
+    type Output = HashSet<ItemId>;
+
+    fn new(ctx: &'ctx BindgenContext) -> HasFloat<'ctx> {
+        let has_float = HashSet::default();
+        let dependencies = generate_dependencies(ctx, Self::consider_edge);
+
+        HasFloat {
+            ctx,
+            has_float,
+            dependencies,
+        }
+    }
+
+    fn initial_worklist(&self) -> Vec<ItemId> {
+        self.ctx.allowlisted_items().iter().cloned().collect()
+    }
+
+    fn constrain(&mut self, id: ItemId) -> ConstrainResult {
+        trace!("constrain: {:?}", id);
+
+        if self.has_float.contains(&id) {
+            trace!("    already know it do not have float");
+            return ConstrainResult::Same;
+        }
+
+        let item = self.ctx.resolve_item(id);
+        let ty = match item.as_type() {
+            Some(ty) => ty,
+            None => {
+                trace!("    not a type; ignoring");
+                return ConstrainResult::Same;
+            }
+        };
+
+        match *ty.kind() {
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Int(..) |
+            TypeKind::Function(..) |
+            TypeKind::Enum(..) |
+            TypeKind::Reference(..) |
+            TypeKind::TypeParam |
+            TypeKind::Opaque |
+            TypeKind::Pointer(..) |
+            TypeKind::UnresolvedTypeRef(..) |
+            TypeKind::ObjCInterface(..) |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel => {
+                trace!("    simple type that do not have float");
+                ConstrainResult::Same
+            }
+
+            TypeKind::Float(..) | TypeKind::Complex(..) => {
+                trace!("    float type has float");
+                self.insert(id)
+            }
+
+            TypeKind::Array(t, _) => {
+                if self.has_float.contains(&t.into()) {
+                    trace!(
+                        "    Array with type T that has float also has float"
+                    );
+                    return self.insert(id);
+                }
+                trace!("    Array with type T that do not have float also do not have float");
+                ConstrainResult::Same
+            }
+            TypeKind::Vector(t, _) => {
+                if self.has_float.contains(&t.into()) {
+                    trace!(
+                        "    Vector with type T that has float also has float"
+                    );
+                    return self.insert(id);
+                }
+                trace!("    Vector with type T that do not have float also do not have float");
+                ConstrainResult::Same
+            }
+
+            TypeKind::ResolvedTypeRef(t) |
+            TypeKind::TemplateAlias(t, _) |
+            TypeKind::Alias(t) |
+            TypeKind::BlockPointer(t) => {
+                if self.has_float.contains(&t.into()) {
+                    trace!(
+                        "    aliases and type refs to T which have float \
+                         also have float"
+                    );
+                    self.insert(id)
+                } else {
+                    trace!("    aliases and type refs to T which do not have float \
+                            also do not have floaarrayt");
+                    ConstrainResult::Same
+                }
+            }
+
+            TypeKind::Comp(ref info) => {
+                let bases_have = info
+                    .base_members()
+                    .iter()
+                    .any(|base| self.has_float.contains(&base.ty.into()));
+                if bases_have {
+                    trace!("    bases have float, so we also have");
+                    return self.insert(id);
+                }
+                let fields_have = info.fields().iter().any(|f| match *f {
+                    Field::DataMember(ref data) => {
+                        self.has_float.contains(&data.ty().into())
+                    }
+                    Field::Bitfields(ref bfu) => bfu
+                        .bitfields()
+                        .iter()
+                        .any(|b| self.has_float.contains(&b.ty().into())),
+                });
+                if fields_have {
+                    trace!("    fields have float, so we also have");
+                    return self.insert(id);
+                }
+
+                trace!("    comp doesn't have float");
+                ConstrainResult::Same
+            }
+
+            TypeKind::TemplateInstantiation(ref template) => {
+                let args_have = template
+                    .template_arguments()
+                    .iter()
+                    .any(|arg| self.has_float.contains(&arg.into()));
+                if args_have {
+                    trace!(
+                        "    template args have float, so \
+                         insantiation also has float"
+                    );
+                    return self.insert(id);
+                }
+
+                let def_has = self
+                    .has_float
+                    .contains(&template.template_definition().into());
+                if def_has {
+                    trace!(
+                        "    template definition has float, so \
+                         insantiation also has"
+                    );
+                    return self.insert(id);
+                }
+
+                trace!("    template instantiation do not have float");
+                ConstrainResult::Same
+            }
+        }
+    }
+
+    fn each_depending_on<F>(&self, id: ItemId, mut f: F)
+    where
+        F: FnMut(ItemId),
+    {
+        if let Some(edges) = self.dependencies.get(&id) {
+            for item in edges {
+                trace!("enqueue {:?} into worklist", item);
+                f(*item);
+            }
+        }
+    }
+}
+
+impl<'ctx> From<HasFloat<'ctx>> for HashSet<ItemId> {
+    fn from(analysis: HasFloat<'ctx>) -> Self {
+        analysis.has_float
+    }
+}
diff --git a/third_party/rust/bindgen/ir/analysis/has_type_param_in_array.rs b/third_party/rust/bindgen/ir/analysis/has_type_param_in_array.rs
new file mode 100644
index 0000000000..088c08f542
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/has_type_param_in_array.rs
@@ -0,0 +1,252 @@
+//! Determining which types has typed parameters in array.
+
+use super::{generate_dependencies, ConstrainResult, MonotoneFramework};
+use crate::ir::comp::Field;
+use crate::ir::comp::FieldMethods;
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::traversal::EdgeKind;
+use crate::ir::ty::TypeKind;
+use crate::{HashMap, HashSet};
+
+/// An analysis that finds for each IR item whether it has array or not.
+///
+/// We use the monotone constraint function `has_type_parameter_in_array`,
+/// defined as follows:
+///
+/// * If T is Array type with type parameter, T trivially has.
+/// * If T is a type alias, a templated alias or an indirection to another type,
+///   it has type parameter in array if the type T refers to has.
+/// * If T is a compound type, it has array if any of base memter or field
+///   has type paramter in array.
+/// * If T is an instantiation of an abstract template definition, T has
+///   type parameter in array if any of the template arguments or template definition
+///   has.
+#[derive(Debug, Clone)]
+pub(crate) struct HasTypeParameterInArray<'ctx> {
+    ctx: &'ctx BindgenContext,
+
+    // The incremental result of this analysis's computation. Everything in this
+    // set has array.
+    has_type_parameter_in_array: HashSet<ItemId>,
+
+    // Dependencies saying that if a key ItemId has been inserted into the
+    // `has_type_parameter_in_array` set, then each of the ids in Vec<ItemId> need to be
+    // considered again.
+    //
+    // This is a subset of the natural IR graph with reversed edges, where we
+    // only include the edges from the IR graph that can affect whether a type
+    // has array or not.
+    dependencies: HashMap<ItemId, Vec<ItemId>>,
+}
+
+impl<'ctx> HasTypeParameterInArray<'ctx> {
+    fn consider_edge(kind: EdgeKind) -> bool {
+        match kind {
+            // These are the only edges that can affect whether a type has type parameter
+            // in array or not.
+            EdgeKind::BaseMember |
+            EdgeKind::Field |
+            EdgeKind::TypeReference |
+            EdgeKind::VarType |
+            EdgeKind::TemplateArgument |
+            EdgeKind::TemplateDeclaration |
+            EdgeKind::TemplateParameterDefinition => true,
+
+            EdgeKind::Constructor |
+            EdgeKind::Destructor |
+            EdgeKind::FunctionReturn |
+            EdgeKind::FunctionParameter |
+            EdgeKind::InnerType |
+            EdgeKind::InnerVar |
+            EdgeKind::Method => false,
+            EdgeKind::Generic => false,
+        }
+    }
+
+    fn insert<Id: Into<ItemId>>(&mut self, id: Id) -> ConstrainResult {
+        let id = id.into();
+        trace!(
+            "inserting {:?} into the has_type_parameter_in_array set",
+            id
+        );
+
+        let was_not_already_in_set =
+            self.has_type_parameter_in_array.insert(id);
+        assert!(
+            was_not_already_in_set,
+            "We shouldn't try and insert {:?} twice because if it was \
+             already in the set, `constrain` should have exited early.",
+            id
+        );
+
+        ConstrainResult::Changed
+    }
+}
+
+impl<'ctx> MonotoneFramework for HasTypeParameterInArray<'ctx> {
+    type Node = ItemId;
+    type Extra = &'ctx BindgenContext;
+    type Output = HashSet<ItemId>;
+
+    fn new(ctx: &'ctx BindgenContext) -> HasTypeParameterInArray<'ctx> {
+        let has_type_parameter_in_array = HashSet::default();
+        let dependencies = generate_dependencies(ctx, Self::consider_edge);
+
+        HasTypeParameterInArray {
+            ctx,
+            has_type_parameter_in_array,
+            dependencies,
+        }
+    }
+
+    fn initial_worklist(&self) -> Vec<ItemId> {
+        self.ctx.allowlisted_items().iter().cloned().collect()
+    }
+
+    fn constrain(&mut self, id: ItemId) -> ConstrainResult {
+        trace!("constrain: {:?}", id);
+
+        if self.has_type_parameter_in_array.contains(&id) {
+            trace!("    already know it do not have array");
+            return ConstrainResult::Same;
+        }
+
+        let item = self.ctx.resolve_item(id);
+        let ty = match item.as_type() {
+            Some(ty) => ty,
+            None => {
+                trace!("    not a type; ignoring");
+                return ConstrainResult::Same;
+            }
+        };
+
+        match *ty.kind() {
+            // Handle the simple cases. These cannot have array in type parameter
+            // without further information.
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Int(..) |
+            TypeKind::Float(..) |
+            TypeKind::Vector(..) |
+            TypeKind::Complex(..) |
+            TypeKind::Function(..) |
+            TypeKind::Enum(..) |
+            TypeKind::Reference(..) |
+            TypeKind::TypeParam |
+            TypeKind::Opaque |
+            TypeKind::Pointer(..) |
+            TypeKind::UnresolvedTypeRef(..) |
+            TypeKind::ObjCInterface(..) |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel => {
+                trace!("    simple type that do not have array");
+                ConstrainResult::Same
+            }
+
+            TypeKind::Array(t, _) => {
+                let inner_ty =
+                    self.ctx.resolve_type(t).canonical_type(self.ctx);
+                match *inner_ty.kind() {
+                    TypeKind::TypeParam => {
+                        trace!("    Array with Named type has type parameter");
+                        self.insert(id)
+                    }
+                    _ => {
+                        trace!(
+                            "    Array without Named type does have type parameter"
+                        );
+                        ConstrainResult::Same
+                    }
+                }
+            }
+
+            TypeKind::ResolvedTypeRef(t) |
+            TypeKind::TemplateAlias(t, _) |
+            TypeKind::Alias(t) |
+            TypeKind::BlockPointer(t) => {
+                if self.has_type_parameter_in_array.contains(&t.into()) {
+                    trace!(
+                        "    aliases and type refs to T which have array \
+                         also have array"
+                    );
+                    self.insert(id)
+                } else {
+                    trace!(
+                        "    aliases and type refs to T which do not have array \
+                            also do not have array"
+                    );
+                    ConstrainResult::Same
+                }
+            }
+
+            TypeKind::Comp(ref info) => {
+                let bases_have = info.base_members().iter().any(|base| {
+                    self.has_type_parameter_in_array.contains(&base.ty.into())
+                });
+                if bases_have {
+                    trace!("    bases have array, so we also have");
+                    return self.insert(id);
+                }
+                let fields_have = info.fields().iter().any(|f| match *f {
+                    Field::DataMember(ref data) => self
+                        .has_type_parameter_in_array
+                        .contains(&data.ty().into()),
+                    Field::Bitfields(..) => false,
+                });
+                if fields_have {
+                    trace!("    fields have array, so we also have");
+                    return self.insert(id);
+                }
+
+                trace!("    comp doesn't have array");
+                ConstrainResult::Same
+            }
+
+            TypeKind::TemplateInstantiation(ref template) => {
+                let args_have =
+                    template.template_arguments().iter().any(|arg| {
+                        self.has_type_parameter_in_array.contains(&arg.into())
+                    });
+                if args_have {
+                    trace!(
+                        "    template args have array, so \
+                         insantiation also has array"
+                    );
+                    return self.insert(id);
+                }
+
+                let def_has = self
+                    .has_type_parameter_in_array
+                    .contains(&template.template_definition().into());
+                if def_has {
+                    trace!(
+                        "    template definition has array, so \
+                         insantiation also has"
+                    );
+                    return self.insert(id);
+                }
+
+                trace!("    template instantiation do not have array");
+                ConstrainResult::Same
+            }
+        }
+    }
+
+    fn each_depending_on<F>(&self, id: ItemId, mut f: F)
+    where
+        F: FnMut(ItemId),
+    {
+        if let Some(edges) = self.dependencies.get(&id) {
+            for item in edges {
+                trace!("enqueue {:?} into worklist", item);
+                f(*item);
+            }
+        }
+    }
+}
+
+impl<'ctx> From<HasTypeParameterInArray<'ctx>> for HashSet<ItemId> {
+    fn from(analysis: HasTypeParameterInArray<'ctx>) -> Self {
+        analysis.has_type_parameter_in_array
+    }
+}
diff --git a/third_party/rust/bindgen/ir/analysis/has_vtable.rs b/third_party/rust/bindgen/ir/analysis/has_vtable.rs
new file mode 100644
index 0000000000..980a551b88
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/has_vtable.rs
@@ -0,0 +1,240 @@
+//! Determining which types has vtable
+
+use super::{generate_dependencies, ConstrainResult, MonotoneFramework};
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::traversal::EdgeKind;
+use crate::ir::ty::TypeKind;
+use crate::{Entry, HashMap};
+use std::cmp;
+use std::ops;
+
+/// The result of the `HasVtableAnalysis` for an individual item.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub(crate) enum HasVtableResult {
+    /// The item does not have a vtable pointer.
+    No,
+
+    /// The item has a vtable and the actual vtable pointer is within this item.
+    SelfHasVtable,
+
+    /// The item has a vtable, but the actual vtable pointer is in a base
+    /// member.
+    BaseHasVtable,
+}
+
+impl Default for HasVtableResult {
+    fn default() -> Self {
+        HasVtableResult::No
+    }
+}
+
+impl HasVtableResult {
+    /// Take the least upper bound of `self` and `rhs`.
+    pub(crate) fn join(self, rhs: Self) -> Self {
+        cmp::max(self, rhs)
+    }
+}
+
+impl ops::BitOr for HasVtableResult {
+    type Output = Self;
+
+    fn bitor(self, rhs: HasVtableResult) -> Self::Output {
+        self.join(rhs)
+    }
+}
+
+impl ops::BitOrAssign for HasVtableResult {
+    fn bitor_assign(&mut self, rhs: HasVtableResult) {
+        *self = self.join(rhs)
+    }
+}
+
+/// An analysis that finds for each IR item whether it has vtable or not
+///
+/// We use the monotone function `has vtable`, defined as follows:
+///
+/// * If T is a type alias, a templated alias, an indirection to another type,
+///   or a reference of a type, T has vtable if the type T refers to has vtable.
+/// * If T is a compound type, T has vtable if we saw a virtual function when
+///   parsing it or any of its base member has vtable.
+/// * If T is an instantiation of an abstract template definition, T has
+///   vtable if template definition has vtable
+#[derive(Debug, Clone)]
+pub(crate) struct HasVtableAnalysis<'ctx> {
+    ctx: &'ctx BindgenContext,
+
+    // The incremental result of this analysis's computation. Everything in this
+    // set definitely has a vtable.
+    have_vtable: HashMap<ItemId, HasVtableResult>,
+
+    // Dependencies saying that if a key ItemId has been inserted into the
+    // `have_vtable` set, then each of the ids in Vec<ItemId> need to be
+    // considered again.
+    //
+    // This is a subset of the natural IR graph with reversed edges, where we
+    // only include the edges from the IR graph that can affect whether a type
+    // has a vtable or not.
+    dependencies: HashMap<ItemId, Vec<ItemId>>,
+}
+
+impl<'ctx> HasVtableAnalysis<'ctx> {
+    fn consider_edge(kind: EdgeKind) -> bool {
+        // These are the only edges that can affect whether a type has a
+        // vtable or not.
+        matches!(
+            kind,
+            EdgeKind::TypeReference |
+                EdgeKind::BaseMember |
+                EdgeKind::TemplateDeclaration
+        )
+    }
+
+    fn insert<Id: Into<ItemId>>(
+        &mut self,
+        id: Id,
+        result: HasVtableResult,
+    ) -> ConstrainResult {
+        if let HasVtableResult::No = result {
+            return ConstrainResult::Same;
+        }
+
+        let id = id.into();
+        match self.have_vtable.entry(id) {
+            Entry::Occupied(mut entry) => {
+                if *entry.get() < result {
+                    entry.insert(result);
+                    ConstrainResult::Changed
+                } else {
+                    ConstrainResult::Same
+                }
+            }
+            Entry::Vacant(entry) => {
+                entry.insert(result);
+                ConstrainResult::Changed
+            }
+        }
+    }
+
+    fn forward<Id1, Id2>(&mut self, from: Id1, to: Id2) -> ConstrainResult
+    where
+        Id1: Into<ItemId>,
+        Id2: Into<ItemId>,
+    {
+        let from = from.into();
+        let to = to.into();
+
+        match self.have_vtable.get(&from).cloned() {
+            None => ConstrainResult::Same,
+            Some(r) => self.insert(to, r),
+        }
+    }
+}
+
+impl<'ctx> MonotoneFramework for HasVtableAnalysis<'ctx> {
+    type Node = ItemId;
+    type Extra = &'ctx BindgenContext;
+    type Output = HashMap<ItemId, HasVtableResult>;
+
+    fn new(ctx: &'ctx BindgenContext) -> HasVtableAnalysis<'ctx> {
+        let have_vtable = HashMap::default();
+        let dependencies = generate_dependencies(ctx, Self::consider_edge);
+
+        HasVtableAnalysis {
+            ctx,
+            have_vtable,
+            dependencies,
+        }
+    }
+
+    fn initial_worklist(&self) -> Vec<ItemId> {
+        self.ctx.allowlisted_items().iter().cloned().collect()
+    }
+
+    fn constrain(&mut self, id: ItemId) -> ConstrainResult {
+        trace!("constrain {:?}", id);
+
+        let item = self.ctx.resolve_item(id);
+        let ty = match item.as_type() {
+            None => return ConstrainResult::Same,
+            Some(ty) => ty,
+        };
+
+        // TODO #851: figure out a way to handle deriving from template type parameters.
+        match *ty.kind() {
+            TypeKind::TemplateAlias(t, _) |
+            TypeKind::Alias(t) |
+            TypeKind::ResolvedTypeRef(t) |
+            TypeKind::Reference(t) => {
+                trace!(
+                    "    aliases and references forward to their inner type"
+                );
+                self.forward(t, id)
+            }
+
+            TypeKind::Comp(ref info) => {
+                trace!("    comp considers its own methods and bases");
+                let mut result = HasVtableResult::No;
+
+                if info.has_own_virtual_method() {
+                    trace!("    comp has its own virtual method");
+                    result |= HasVtableResult::SelfHasVtable;
+                }
+
+                let bases_has_vtable = info.base_members().iter().any(|base| {
+                    trace!("    comp has a base with a vtable: {:?}", base);
+                    self.have_vtable.contains_key(&base.ty.into())
+                });
+                if bases_has_vtable {
+                    result |= HasVtableResult::BaseHasVtable;
+                }
+
+                self.insert(id, result)
+            }
+
+            TypeKind::TemplateInstantiation(ref inst) => {
+                self.forward(inst.template_definition(), id)
+            }
+
+            _ => ConstrainResult::Same,
+        }
+    }
+
+    fn each_depending_on<F>(&self, id: ItemId, mut f: F)
+    where
+        F: FnMut(ItemId),
+    {
+        if let Some(edges) = self.dependencies.get(&id) {
+            for item in edges {
+                trace!("enqueue {:?} into worklist", item);
+                f(*item);
+            }
+        }
+    }
+}
+
+impl<'ctx> From<HasVtableAnalysis<'ctx>> for HashMap<ItemId, HasVtableResult> {
+    fn from(analysis: HasVtableAnalysis<'ctx>) -> Self {
+        // We let the lack of an entry mean "No" to save space.
+        extra_assert!(analysis
+            .have_vtable
+            .values()
+            .all(|v| { *v != HasVtableResult::No }));
+
+        analysis.have_vtable
+    }
+}
+
+/// A convenience trait for the things for which we might wonder if they have a
+/// vtable during codegen.
+///
+/// This is not for _computing_ whether the thing has a vtable, it is for
+/// looking up the results of the HasVtableAnalysis's computations for a
+/// specific thing.
+pub(crate) trait HasVtable {
+    /// Return `true` if this thing has vtable, `false` otherwise.
+    fn has_vtable(&self, ctx: &BindgenContext) -> bool;
+
+    /// Return `true` if this thing has an actual vtable pointer in itself, as
+    /// opposed to transitively in a base member.
+    fn has_vtable_ptr(&self, ctx: &BindgenContext) -> bool;
+}
diff --git a/third_party/rust/bindgen/ir/analysis/mod.rs b/third_party/rust/bindgen/ir/analysis/mod.rs
new file mode 100644
index 0000000000..443384a487
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/mod.rs
@@ -0,0 +1,400 @@
+//! Fix-point analyses on the IR using the "monotone framework".
+//!
+//! A lattice is a set with a partial ordering between elements, where there is
+//! a single least upper bound and a single greatest least bound for every
+//! subset. We are dealing with finite lattices, which means that it has a
+//! finite number of elements, and it follows that there exists a single top and
+//! a single bottom member of the lattice. For example, the power set of a
+//! finite set forms a finite lattice where partial ordering is defined by set
+//! inclusion, that is `a <= b` if `a` is a subset of `b`. Here is the finite
+//! lattice constructed from the set {0,1,2}:
+//!
+//! ```text
+//!                    .----- Top = {0,1,2} -----.
+//!                   /            |              \
+//!                  /             |               \
+//!                 /              |                \
+//!              {0,1} -------.  {0,2}  .--------- {1,2}
+//!                |           \ /   \ /             |
+//!                |            /     \              |
+//!                |           / \   / \             |
+//!               {0} --------'   {1}   `---------- {2}
+//!                 \              |                /
+//!                  \             |               /
+//!                   \            |              /
+//!                    `------ Bottom = {} ------'
+//! ```
+//!
+//! A monotone function `f` is a function where if `x <= y`, then it holds that
+//! `f(x) <= f(y)`. It should be clear that running a monotone function to a
+//! fix-point on a finite lattice will always terminate: `f` can only "move"
+//! along the lattice in a single direction, and therefore can only either find
+//! a fix-point in the middle of the lattice or continue to the top or bottom
+//! depending if it is ascending or descending the lattice respectively.
+//!
+//! For a deeper introduction to the general form of this kind of analysis, see
+//! [Static Program Analysis by Anders Møller and Michael I. Schwartzbach][spa].
+//!
+//! [spa]: https://cs.au.dk/~amoeller/spa/spa.pdf
+
+// Re-export individual analyses.
+mod template_params;
+pub(crate) use self::template_params::UsedTemplateParameters;
+mod derive;
+pub use self::derive::DeriveTrait;
+pub(crate) use self::derive::{as_cannot_derive_set, CannotDerive};
+mod has_vtable;
+pub(crate) use self::has_vtable::{
+    HasVtable, HasVtableAnalysis, HasVtableResult,
+};
+mod has_destructor;
+pub(crate) use self::has_destructor::HasDestructorAnalysis;
+mod has_type_param_in_array;
+pub(crate) use self::has_type_param_in_array::HasTypeParameterInArray;
+mod has_float;
+pub(crate) use self::has_float::HasFloat;
+mod sizedness;
+pub(crate) use self::sizedness::{
+    Sizedness, SizednessAnalysis, SizednessResult,
+};
+
+use crate::ir::context::{BindgenContext, ItemId};
+
+use crate::ir::traversal::{EdgeKind, Trace};
+use crate::HashMap;
+use std::fmt;
+use std::ops;
+
+/// An analysis in the monotone framework.
+///
+/// Implementors of this trait must maintain the following two invariants:
+///
+/// 1. The concrete data must be a member of a finite-height lattice.
+/// 2. The concrete `constrain` method must be monotone: that is,
+///    if `x <= y`, then `constrain(x) <= constrain(y)`.
+///
+/// If these invariants do not hold, iteration to a fix-point might never
+/// complete.
+///
+/// For a simple example analysis, see the `ReachableFrom` type in the `tests`
+/// module below.
+pub(crate) trait MonotoneFramework: Sized + fmt::Debug {
+    /// The type of node in our dependency graph.
+    ///
+    /// This is just generic (and not `ItemId`) so that we can easily unit test
+    /// without constructing real `Item`s and their `ItemId`s.
+    type Node: Copy;
+
+    /// Any extra data that is needed during computation.
+    ///
+    /// Again, this is just generic (and not `&BindgenContext`) so that we can
+    /// easily unit test without constructing real `BindgenContext`s full of
+    /// real `Item`s and real `ItemId`s.
+    type Extra: Sized;
+
+    /// The final output of this analysis. Once we have reached a fix-point, we
+    /// convert `self` into this type, and return it as the final result of the
+    /// analysis.
+    type Output: From<Self> + fmt::Debug;
+
+    /// Construct a new instance of this analysis.
+    fn new(extra: Self::Extra) -> Self;
+
+    /// Get the initial set of nodes from which to start the analysis. Unless
+    /// you are sure of some domain-specific knowledge, this should be the
+    /// complete set of nodes.
+    fn initial_worklist(&self) -> Vec<Self::Node>;
+
+    /// Update the analysis for the given node.
+    ///
+    /// If this results in changing our internal state (ie, we discovered that
+    /// we have not reached a fix-point and iteration should continue), return
+    /// `ConstrainResult::Changed`. Otherwise, return `ConstrainResult::Same`.
+    /// When `constrain` returns `ConstrainResult::Same` for all nodes in the
+    /// set, we have reached a fix-point and the analysis is complete.
+    fn constrain(&mut self, node: Self::Node) -> ConstrainResult;
+
+    /// For each node `d` that depends on the given `node`'s current answer when
+    /// running `constrain(d)`, call `f(d)`. This informs us which new nodes to
+    /// queue up in the worklist when `constrain(node)` reports updated
+    /// information.
+    fn each_depending_on<F>(&self, node: Self::Node, f: F)
+    where
+        F: FnMut(Self::Node);
+}
+
+/// Whether an analysis's `constrain` function modified the incremental results
+/// or not.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum ConstrainResult {
+    /// The incremental results were updated, and the fix-point computation
+    /// should continue.
+    Changed,
+
+    /// The incremental results were not updated.
+    Same,
+}
+
+impl Default for ConstrainResult {
+    fn default() -> Self {
+        ConstrainResult::Same
+    }
+}
+
+impl ops::BitOr for ConstrainResult {
+    type Output = Self;
+
+    fn bitor(self, rhs: ConstrainResult) -> Self::Output {
+        if self == ConstrainResult::Changed || rhs == ConstrainResult::Changed {
+            ConstrainResult::Changed
+        } else {
+            ConstrainResult::Same
+        }
+    }
+}
+
+impl ops::BitOrAssign for ConstrainResult {
+    fn bitor_assign(&mut self, rhs: ConstrainResult) {
+        *self = *self | rhs;
+    }
+}
+
+/// Run an analysis in the monotone framework.
+pub(crate) fn analyze<Analysis>(extra: Analysis::Extra) -> Analysis::Output
+where
+    Analysis: MonotoneFramework,
+{
+    let mut analysis = Analysis::new(extra);
+    let mut worklist = analysis.initial_worklist();
+
+    while let Some(node) = worklist.pop() {
+        if let ConstrainResult::Changed = analysis.constrain(node) {
+            analysis.each_depending_on(node, |needs_work| {
+                worklist.push(needs_work);
+            });
+        }
+    }
+
+    analysis.into()
+}
+
+/// Generate the dependency map for analysis
+pub(crate) fn generate_dependencies<F>(
+    ctx: &BindgenContext,
+    consider_edge: F,
+) -> HashMap<ItemId, Vec<ItemId>>
+where
+    F: Fn(EdgeKind) -> bool,
+{
+    let mut dependencies = HashMap::default();
+
+    for &item in ctx.allowlisted_items() {
+        dependencies.entry(item).or_insert_with(Vec::new);
+
+        {
+            // We reverse our natural IR graph edges to find dependencies
+            // between nodes.
+            item.trace(
+                ctx,
+                &mut |sub_item: ItemId, edge_kind| {
+                    if ctx.allowlisted_items().contains(&sub_item) &&
+                        consider_edge(edge_kind)
+                    {
+                        dependencies
+                            .entry(sub_item)
+                            .or_insert_with(Vec::new)
+                            .push(item);
+                    }
+                },
+                &(),
+            );
+        }
+    }
+    dependencies
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{HashMap, HashSet};
+
+    // Here we find the set of nodes that are reachable from any given
+    // node. This is a lattice mapping nodes to subsets of all nodes. Our join
+    // function is set union.
+    //
+    // This is our test graph:
+    //
+    //     +---+                    +---+
+    //     |   |                    |   |
+    //     | 1 |               .----| 2 |
+    //     |   |               |    |   |
+    //     +---+               |    +---+
+    //       |                 |      ^
+    //       |                 |      |
+    //       |      +---+      '------'
+    //       '----->|   |
+    //              | 3 |
+    //       .------|   |------.
+    //       |      +---+      |
+    //       |        ^        |
+    //       v        |        v
+    //     +---+      |      +---+    +---+
+    //     |   |      |      |   |    |   |
+    //     | 4 |      |      | 5 |--->| 6 |
+    //     |   |      |      |   |    |   |
+    //     +---+      |      +---+    +---+
+    //       |        |        |        |
+    //       |        |        |        v
+    //       |      +---+      |      +---+
+    //       |      |   |      |      |   |
+    //       '----->| 7 |<-----'      | 8 |
+    //              |   |             |   |
+    //              +---+             +---+
+    //
+    // And here is the mapping from a node to the set of nodes that are
+    // reachable from it within the test graph:
+    //
+    //     1: {3,4,5,6,7,8}
+    //     2: {2}
+    //     3: {3,4,5,6,7,8}
+    //     4: {3,4,5,6,7,8}
+    //     5: {3,4,5,6,7,8}
+    //     6: {8}
+    //     7: {3,4,5,6,7,8}
+    //     8: {}
+
+    #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
+    struct Node(usize);
+
+    #[derive(Clone, Debug, Default, PartialEq, Eq)]
+    struct Graph(HashMap<Node, Vec<Node>>);
+
+    impl Graph {
+        fn make_test_graph() -> Graph {
+            let mut g = Graph::default();
+            g.0.insert(Node(1), vec![Node(3)]);
+            g.0.insert(Node(2), vec![Node(2)]);
+            g.0.insert(Node(3), vec![Node(4), Node(5)]);
+            g.0.insert(Node(4), vec![Node(7)]);
+            g.0.insert(Node(5), vec![Node(6), Node(7)]);
+            g.0.insert(Node(6), vec![Node(8)]);
+            g.0.insert(Node(7), vec![Node(3)]);
+            g.0.insert(Node(8), vec![]);
+            g
+        }
+
+        fn reverse(&self) -> Graph {
+            let mut reversed = Graph::default();
+            for (node, edges) in self.0.iter() {
+                reversed.0.entry(*node).or_insert_with(Vec::new);
+                for referent in edges.iter() {
+                    reversed
+                        .0
+                        .entry(*referent)
+                        .or_insert_with(Vec::new)
+                        .push(*node);
+                }
+            }
+            reversed
+        }
+    }
+
+    #[derive(Clone, Debug, PartialEq, Eq)]
+    struct ReachableFrom<'a> {
+        reachable: HashMap<Node, HashSet<Node>>,
+        graph: &'a Graph,
+        reversed: Graph,
+    }
+
+    impl<'a> MonotoneFramework for ReachableFrom<'a> {
+        type Node = Node;
+        type Extra = &'a Graph;
+        type Output = HashMap<Node, HashSet<Node>>;
+
+        fn new(graph: &'a Graph) -> ReachableFrom {
+            let reversed = graph.reverse();
+            ReachableFrom {
+                reachable: Default::default(),
+                graph,
+                reversed,
+            }
+        }
+
+        fn initial_worklist(&self) -> Vec<Node> {
+            self.graph.0.keys().cloned().collect()
+        }
+
+        fn constrain(&mut self, node: Node) -> ConstrainResult {
+            // The set of nodes reachable from a node `x` is
+            //
+            //     reachable(x) = s_0 U s_1 U ... U reachable(s_0) U reachable(s_1) U ...
+            //
+            // where there exist edges from `x` to each of `s_0, s_1, ...`.
+            //
+            // Yes, what follows is a **terribly** inefficient set union
+            // implementation. Don't copy this code outside of this test!
+
+            let original_size = self.reachable.entry(node).or_default().len();
+
+            for sub_node in self.graph.0[&node].iter() {
+                self.reachable.get_mut(&node).unwrap().insert(*sub_node);
+
+                let sub_reachable =
+                    self.reachable.entry(*sub_node).or_default().clone();
+
+                for transitive in sub_reachable {
+                    self.reachable.get_mut(&node).unwrap().insert(transitive);
+                }
+            }
+
+            let new_size = self.reachable[&node].len();
+            if original_size != new_size {
+                ConstrainResult::Changed
+            } else {
+                ConstrainResult::Same
+            }
+        }
+
+        fn each_depending_on<F>(&self, node: Node, mut f: F)
+        where
+            F: FnMut(Node),
+        {
+            for dep in self.reversed.0[&node].iter() {
+                f(*dep);
+            }
+        }
+    }
+
+    impl<'a> From<ReachableFrom<'a>> for HashMap<Node, HashSet<Node>> {
+        fn from(reachable: ReachableFrom<'a>) -> Self {
+            reachable.reachable
+        }
+    }
+
+    #[test]
+    fn monotone() {
+        let g = Graph::make_test_graph();
+        let reachable = analyze::<ReachableFrom>(&g);
+        println!("reachable = {:#?}", reachable);
+
+        fn nodes<A>(nodes: A) -> HashSet<Node>
+        where
+            A: AsRef<[usize]>,
+        {
+            nodes.as_ref().iter().cloned().map(Node).collect()
+        }
+
+        let mut expected = HashMap::default();
+        expected.insert(Node(1), nodes([3, 4, 5, 6, 7, 8]));
+        expected.insert(Node(2), nodes([2]));
+        expected.insert(Node(3), nodes([3, 4, 5, 6, 7, 8]));
+        expected.insert(Node(4), nodes([3, 4, 5, 6, 7, 8]));
+        expected.insert(Node(5), nodes([3, 4, 5, 6, 7, 8]));
+        expected.insert(Node(6), nodes([8]));
+        expected.insert(Node(7), nodes([3, 4, 5, 6, 7, 8]));
+        expected.insert(Node(8), nodes([]));
+        println!("expected = {:#?}", expected);
+
+        assert_eq!(reachable, expected);
+    }
+}
diff --git a/third_party/rust/bindgen/ir/analysis/sizedness.rs b/third_party/rust/bindgen/ir/analysis/sizedness.rs
new file mode 100644
index 0000000000..995d700794
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/sizedness.rs
@@ -0,0 +1,361 @@
+//! Determining the sizedness of types (as base classes and otherwise).
+
+use super::{
+    generate_dependencies, ConstrainResult, HasVtable, MonotoneFramework,
+};
+use crate::ir::context::{BindgenContext, TypeId};
+use crate::ir::item::IsOpaque;
+use crate::ir::traversal::EdgeKind;
+use crate::ir::ty::TypeKind;
+use crate::{Entry, HashMap};
+use std::{cmp, ops};
+
+/// The result of the `Sizedness` analysis for an individual item.
+///
+/// This is a chain lattice of the form:
+///
+/// ```ignore
+///                   NonZeroSized
+///                        |
+///                DependsOnTypeParam
+///                        |
+///                     ZeroSized
+/// ```
+///
+/// We initially assume that all types are `ZeroSized` and then update our
+/// understanding as we learn more about each type.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub(crate) enum SizednessResult {
+    /// The type is zero-sized.
+    ///
+    /// This means that if it is a C++ type, and is not being used as a base
+    /// member, then we must add an `_address` byte to enforce the
+    /// unique-address-per-distinct-object-instance rule.
+    ZeroSized,
+
+    /// Whether this type is zero-sized or not depends on whether a type
+    /// parameter is zero-sized or not.
+    ///
+    /// For example, given these definitions:
+    ///
+    /// ```c++
+    /// template<class T>
+    /// class Flongo : public T {};
+    ///
+    /// class Empty {};
+    ///
+    /// class NonEmpty { int x; };
+    /// ```
+    ///
+    /// Then `Flongo<Empty>` is zero-sized, and needs an `_address` byte
+    /// inserted, while `Flongo<NonEmpty>` is *not* zero-sized, and should *not*
+    /// have an `_address` byte inserted.
+    ///
+    /// We don't properly handle this situation correctly right now:
+    /// <https://github.com/rust-lang/rust-bindgen/issues/586>
+    DependsOnTypeParam,
+
+    /// Has some size that is known to be greater than zero. That doesn't mean
+    /// it has a static size, but it is not zero sized for sure. In other words,
+    /// it might contain an incomplete array or some other dynamically sized
+    /// type.
+    NonZeroSized,
+}
+
+impl Default for SizednessResult {
+    fn default() -> Self {
+        SizednessResult::ZeroSized
+    }
+}
+
+impl SizednessResult {
+    /// Take the least upper bound of `self` and `rhs`.
+    pub(crate) fn join(self, rhs: Self) -> Self {
+        cmp::max(self, rhs)
+    }
+}
+
+impl ops::BitOr for SizednessResult {
+    type Output = Self;
+
+    fn bitor(self, rhs: SizednessResult) -> Self::Output {
+        self.join(rhs)
+    }
+}
+
+impl ops::BitOrAssign for SizednessResult {
+    fn bitor_assign(&mut self, rhs: SizednessResult) {
+        *self = self.join(rhs)
+    }
+}
+
+/// An analysis that computes the sizedness of all types.
+///
+/// * For types with known sizes -- for example pointers, scalars, etc... --
+/// they are assigned `NonZeroSized`.
+///
+/// * For compound structure types with one or more fields, they are assigned
+/// `NonZeroSized`.
+///
+/// * For compound structure types without any fields, the results of the bases
+/// are `join`ed.
+///
+/// * For type parameters, `DependsOnTypeParam` is assigned.
+#[derive(Debug)]
+pub(crate) struct SizednessAnalysis<'ctx> {
+    ctx: &'ctx BindgenContext,
+    dependencies: HashMap<TypeId, Vec<TypeId>>,
+    // Incremental results of the analysis. Missing entries are implicitly
+    // considered `ZeroSized`.
+    sized: HashMap<TypeId, SizednessResult>,
+}
+
+impl<'ctx> SizednessAnalysis<'ctx> {
+    fn consider_edge(kind: EdgeKind) -> bool {
+        // These are the only edges that can affect whether a type is
+        // zero-sized or not.
+        matches!(
+            kind,
+            EdgeKind::TemplateArgument |
+                EdgeKind::TemplateParameterDefinition |
+                EdgeKind::TemplateDeclaration |
+                EdgeKind::TypeReference |
+                EdgeKind::BaseMember |
+                EdgeKind::Field
+        )
+    }
+
+    /// Insert an incremental result, and return whether this updated our
+    /// knowledge of types and we should continue the analysis.
+    fn insert(
+        &mut self,
+        id: TypeId,
+        result: SizednessResult,
+    ) -> ConstrainResult {
+        trace!("inserting {:?} for {:?}", result, id);
+
+        if let SizednessResult::ZeroSized = result {
+            return ConstrainResult::Same;
+        }
+
+        match self.sized.entry(id) {
+            Entry::Occupied(mut entry) => {
+                if *entry.get() < result {
+                    entry.insert(result);
+                    ConstrainResult::Changed
+                } else {
+                    ConstrainResult::Same
+                }
+            }
+            Entry::Vacant(entry) => {
+                entry.insert(result);
+                ConstrainResult::Changed
+            }
+        }
+    }
+
+    fn forward(&mut self, from: TypeId, to: TypeId) -> ConstrainResult {
+        match self.sized.get(&from).cloned() {
+            None => ConstrainResult::Same,
+            Some(r) => self.insert(to, r),
+        }
+    }
+}
+
+impl<'ctx> MonotoneFramework for SizednessAnalysis<'ctx> {
+    type Node = TypeId;
+    type Extra = &'ctx BindgenContext;
+    type Output = HashMap<TypeId, SizednessResult>;
+
+    fn new(ctx: &'ctx BindgenContext) -> SizednessAnalysis<'ctx> {
+        let dependencies = generate_dependencies(ctx, Self::consider_edge)
+            .into_iter()
+            .filter_map(|(id, sub_ids)| {
+                id.as_type_id(ctx).map(|id| {
+                    (
+                        id,
+                        sub_ids
+                            .into_iter()
+                            .filter_map(|s| s.as_type_id(ctx))
+                            .collect::<Vec<_>>(),
+                    )
+                })
+            })
+            .collect();
+
+        let sized = HashMap::default();
+
+        SizednessAnalysis {
+            ctx,
+            dependencies,
+            sized,
+        }
+    }
+
+    fn initial_worklist(&self) -> Vec<TypeId> {
+        self.ctx
+            .allowlisted_items()
+            .iter()
+            .cloned()
+            .filter_map(|id| id.as_type_id(self.ctx))
+            .collect()
+    }
+
+    fn constrain(&mut self, id: TypeId) -> ConstrainResult {
+        trace!("constrain {:?}", id);
+
+        if let Some(SizednessResult::NonZeroSized) =
+            self.sized.get(&id).cloned()
+        {
+            trace!("    already know it is not zero-sized");
+            return ConstrainResult::Same;
+        }
+
+        if id.has_vtable_ptr(self.ctx) {
+            trace!("    has an explicit vtable pointer, therefore is not zero-sized");
+            return self.insert(id, SizednessResult::NonZeroSized);
+        }
+
+        let ty = self.ctx.resolve_type(id);
+
+        if id.is_opaque(self.ctx, &()) {
+            trace!("    type is opaque; checking layout...");
+            let result =
+                ty.layout(self.ctx).map_or(SizednessResult::ZeroSized, |l| {
+                    if l.size == 0 {
+                        trace!("    ...layout has size == 0");
+                        SizednessResult::ZeroSized
+                    } else {
+                        trace!("    ...layout has size > 0");
+                        SizednessResult::NonZeroSized
+                    }
+                });
+            return self.insert(id, result);
+        }
+
+        match *ty.kind() {
+            TypeKind::Void => {
+                trace!("    void is zero-sized");
+                self.insert(id, SizednessResult::ZeroSized)
+            }
+
+            TypeKind::TypeParam => {
+                trace!(
+                    "    type params sizedness depends on what they're \
+                     instantiated as"
+                );
+                self.insert(id, SizednessResult::DependsOnTypeParam)
+            }
+
+            TypeKind::Int(..) |
+            TypeKind::Float(..) |
+            TypeKind::Complex(..) |
+            TypeKind::Function(..) |
+            TypeKind::Enum(..) |
+            TypeKind::Reference(..) |
+            TypeKind::NullPtr |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel |
+            TypeKind::Pointer(..) => {
+                trace!("    {:?} is known not to be zero-sized", ty.kind());
+                self.insert(id, SizednessResult::NonZeroSized)
+            }
+
+            TypeKind::ObjCInterface(..) => {
+                trace!("    obj-c interfaces always have at least the `isa` pointer");
+                self.insert(id, SizednessResult::NonZeroSized)
+            }
+
+            TypeKind::TemplateAlias(t, _) |
+            TypeKind::Alias(t) |
+            TypeKind::BlockPointer(t) |
+            TypeKind::ResolvedTypeRef(t) => {
+                trace!("    aliases and type refs forward to their inner type");
+                self.forward(t, id)
+            }
+
+            TypeKind::TemplateInstantiation(ref inst) => {
+                trace!(
+                    "    template instantiations are zero-sized if their \
+                     definition is zero-sized"
+                );
+                self.forward(inst.template_definition(), id)
+            }
+
+            TypeKind::Array(_, 0) => {
+                trace!("    arrays of zero elements are zero-sized");
+                self.insert(id, SizednessResult::ZeroSized)
+            }
+            TypeKind::Array(..) => {
+                trace!("    arrays of > 0 elements are not zero-sized");
+                self.insert(id, SizednessResult::NonZeroSized)
+            }
+            TypeKind::Vector(..) => {
+                trace!("    vectors are not zero-sized");
+                self.insert(id, SizednessResult::NonZeroSized)
+            }
+
+            TypeKind::Comp(ref info) => {
+                trace!("    comp considers its own fields and bases");
+
+                if !info.fields().is_empty() {
+                    return self.insert(id, SizednessResult::NonZeroSized);
+                }
+
+                let result = info
+                    .base_members()
+                    .iter()
+                    .filter_map(|base| self.sized.get(&base.ty))
+                    .fold(SizednessResult::ZeroSized, |a, b| a.join(*b));
+
+                self.insert(id, result)
+            }
+
+            TypeKind::Opaque => {
+                unreachable!("covered by the .is_opaque() check above")
+            }
+
+            TypeKind::UnresolvedTypeRef(..) => {
+                unreachable!("Should have been resolved after parsing!");
+            }
+        }
+    }
+
+    fn each_depending_on<F>(&self, id: TypeId, mut f: F)
+    where
+        F: FnMut(TypeId),
+    {
+        if let Some(edges) = self.dependencies.get(&id) {
+            for ty in edges {
+                trace!("enqueue {:?} into worklist", ty);
+                f(*ty);
+            }
+        }
+    }
+}
+
+impl<'ctx> From<SizednessAnalysis<'ctx>> for HashMap<TypeId, SizednessResult> {
+    fn from(analysis: SizednessAnalysis<'ctx>) -> Self {
+        // We let the lack of an entry mean "ZeroSized" to save space.
+        extra_assert!(analysis
+            .sized
+            .values()
+            .all(|v| { *v != SizednessResult::ZeroSized }));
+
+        analysis.sized
+    }
+}
+
+/// A convenience trait for querying whether some type or ID is sized.
+///
+/// This is not for _computing_ whether the thing is sized, it is for looking up
+/// the results of the `Sizedness` analysis's computations for a specific thing.
+pub(crate) trait Sizedness {
+    /// Get the sizedness of this type.
+    fn sizedness(&self, ctx: &BindgenContext) -> SizednessResult;
+
+    /// Is the sizedness for this type `SizednessResult::ZeroSized`?
+    fn is_zero_sized(&self, ctx: &BindgenContext) -> bool {
+        self.sizedness(ctx) == SizednessResult::ZeroSized
+    }
+}
diff --git a/third_party/rust/bindgen/ir/analysis/template_params.rs b/third_party/rust/bindgen/ir/analysis/template_params.rs
new file mode 100644
index 0000000000..e4261cf675
--- /dev/null
+++ b/third_party/rust/bindgen/ir/analysis/template_params.rs
@@ -0,0 +1,607 @@
+//! Discover which template type parameters are actually used.
+//!
+//! ### Why do we care?
+//!
+//! C++ allows ignoring template parameters, while Rust does not. Usually we can
+//! blindly stick a `PhantomData<T>` inside a generic Rust struct to make up for
+//! this. That doesn't work for templated type aliases, however:
+//!
+//! ```C++
+//! template <typename T>
+//! using Fml = int;
+//! ```
+//!
+//! If we generate the naive Rust code for this alias, we get:
+//!
+//! ```ignore
+//! pub(crate) type Fml<T> = ::std::os::raw::int;
+//! ```
+//!
+//! And this is rejected by `rustc` due to the unused type parameter.
+//!
+//! (Aside: in these simple cases, `libclang` will often just give us the
+//! aliased type directly, and we will never even know we were dealing with
+//! aliases, let alone templated aliases. It's the more convoluted scenarios
+//! where we get to have some fun...)
+//!
+//! For such problematic template aliases, we could generate a tuple whose
+//! second member is a `PhantomData<T>`. Or, if we wanted to go the extra mile,
+//! we could even generate some smarter wrapper that implements `Deref`,
+//! `DerefMut`, `From`, `Into`, `AsRef`, and `AsMut` to the actually aliased
+//! type. However, this is still lackluster:
+//!
+//! 1. Even with a billion conversion-trait implementations, using the generated
+//!    bindings is rather un-ergonomic.
+//! 2. With either of these solutions, we need to keep track of which aliases
+//!    we've transformed like this in order to generate correct uses of the
+//!    wrapped type.
+//!
+//! Given that we have to properly track which template parameters ended up used
+//! for (2), we might as well leverage that information to make ergonomic
+//! bindings that don't contain any unused type parameters at all, and
+//! completely avoid the pain of (1).
+//!
+//! ### How do we determine which template parameters are used?
+//!
+//! Determining which template parameters are actually used is a trickier
+//! problem than it might seem at a glance. On the one hand, trivial uses are
+//! easy to detect:
+//!
+//! ```C++
+//! template <typename T>
+//! class Foo {
+//!     T trivial_use_of_t;
+//! };
+//! ```
+//!
+//! It gets harder when determining if one template parameter is used depends on
+//! determining if another template parameter is used. In this example, whether
+//! `U` is used depends on whether `T` is used.
+//!
+//! ```C++
+//! template <typename T>
+//! class DoesntUseT {
+//!     int x;
+//! };
+//!
+//! template <typename U>
+//! class Fml {
+//!     DoesntUseT<U> lololol;
+//! };
+//! ```
+//!
+//! We can express the set of used template parameters as a constraint solving
+//! problem (where the set of template parameters used by a given IR item is the
+//! union of its sub-item's used template parameters) and iterate to a
+//! fixed-point.
+//!
+//! We use the `ir::analysis::MonotoneFramework` infrastructure for this
+//! fix-point analysis, where our lattice is the mapping from each IR item to
+//! the powerset of the template parameters that appear in the input C++ header,
+//! our join function is set union. The set of template parameters appearing in
+//! the program is finite, as is the number of IR items. We start at our
+//! lattice's bottom element: every item mapping to an empty set of template
+//! parameters. Our analysis only adds members to each item's set of used
+//! template parameters, never removes them, so it is monotone. Because our
+//! lattice is finite and our constraint function is monotone, iteration to a
+//! fix-point will terminate.
+//!
+//! See `src/ir/analysis.rs` for more.
+
+use super::{ConstrainResult, MonotoneFramework};
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::item::{Item, ItemSet};
+use crate::ir::template::{TemplateInstantiation, TemplateParameters};
+use crate::ir::traversal::{EdgeKind, Trace};
+use crate::ir::ty::TypeKind;
+use crate::{HashMap, HashSet};
+
+/// An analysis that finds for each IR item its set of template parameters that
+/// it uses.
+///
+/// We use the monotone constraint function `template_param_usage`, defined as
+/// follows:
+///
+/// * If `T` is a named template type parameter, it trivially uses itself:
+///
+/// ```ignore
+/// template_param_usage(T) = { T }
+/// ```
+///
+/// * If `inst` is a template instantiation, `inst.args` are the template
+///   instantiation's template arguments, `inst.def` is the template definition
+///   being instantiated, and `inst.def.params` is the template definition's
+///   template parameters, then the instantiation's usage is the union of each
+///   of its arguments' usages *if* the corresponding template parameter is in
+///   turn used by the template definition:
+///
+/// ```ignore
+/// template_param_usage(inst) = union(
+///     template_param_usage(inst.args[i])
+///         for i in 0..length(inst.args.length)
+///             if inst.def.params[i] in template_param_usage(inst.def)
+/// )
+/// ```
+///
+/// * Finally, for all other IR item kinds, we use our lattice's `join`
+/// operation: set union with each successor of the given item's template
+/// parameter usage:
+///
+/// ```ignore
+/// template_param_usage(v) =
+///     union(template_param_usage(w) for w in successors(v))
+/// ```
+///
+/// Note that we ignore certain edges in the graph, such as edges from a
+/// template declaration to its template parameters' definitions for this
+/// analysis. If we didn't, then we would mistakenly determine that ever
+/// template parameter is always used.
+///
+/// The final wrinkle is handling of blocklisted types. Normally, we say that
+/// the set of allowlisted items is the transitive closure of items explicitly
+/// called out for allowlisting, *without* any items explicitly called out as
+/// blocklisted. However, for the purposes of this analysis's correctness, we
+/// simplify and consider run the analysis on the full transitive closure of
+/// allowlisted items. We do, however, treat instantiations of blocklisted items
+/// specially; see `constrain_instantiation_of_blocklisted_template` and its
+/// documentation for details.
+#[derive(Debug, Clone)]
+pub(crate) struct UsedTemplateParameters<'ctx> {
+    ctx: &'ctx BindgenContext,
+
+    // The Option is only there for temporary moves out of the hash map. See the
+    // comments in `UsedTemplateParameters::constrain` below.
+    used: HashMap<ItemId, Option<ItemSet>>,
+
+    dependencies: HashMap<ItemId, Vec<ItemId>>,
+
+    // The set of allowlisted items, without any blocklisted items reachable
+    // from the allowlisted items which would otherwise be considered
+    // allowlisted as well.
+    allowlisted_items: HashSet<ItemId>,
+}
+
+impl<'ctx> UsedTemplateParameters<'ctx> {
+    fn consider_edge(kind: EdgeKind) -> bool {
+        match kind {
+            // For each of these kinds of edges, if the referent uses a template
+            // parameter, then it should be considered that the origin of the
+            // edge also uses the template parameter.
+            EdgeKind::TemplateArgument |
+            EdgeKind::BaseMember |
+            EdgeKind::Field |
+            EdgeKind::Constructor |
+            EdgeKind::Destructor |
+            EdgeKind::VarType |
+            EdgeKind::FunctionReturn |
+            EdgeKind::FunctionParameter |
+            EdgeKind::TypeReference => true,
+
+            // An inner var or type using a template parameter is orthogonal
+            // from whether we use it. See template-param-usage-{6,11}.hpp.
+            EdgeKind::InnerVar | EdgeKind::InnerType => false,
+
+            // We can't emit machine code for new monomorphizations of class
+            // templates' methods (and don't detect explicit instantiations) so
+            // we must ignore template parameters that are only used by
+            // methods. This doesn't apply to a function type's return or
+            // parameter types, however, because of type aliases of function
+            // pointers that use template parameters, eg
+            // tests/headers/struct_with_typedef_template_arg.hpp
+            EdgeKind::Method => false,
+
+            // If we considered these edges, we would end up mistakenly claiming
+            // that every template parameter always used.
+            EdgeKind::TemplateDeclaration |
+            EdgeKind::TemplateParameterDefinition => false,
+
+            // Since we have to be careful about which edges we consider for
+            // this analysis to be correct, we ignore generic edges. We also
+            // avoid a `_` wild card to force authors of new edge kinds to
+            // determine whether they need to be considered by this analysis.
+            EdgeKind::Generic => false,
+        }
+    }
+
+    fn take_this_id_usage_set<Id: Into<ItemId>>(
+        &mut self,
+        this_id: Id,
+    ) -> ItemSet {
+        let this_id = this_id.into();
+        self.used
+            .get_mut(&this_id)
+            .expect(
+                "Should have a set of used template params for every item \
+                 id",
+            )
+            .take()
+            .expect(
+                "Should maintain the invariant that all used template param \
+                 sets are `Some` upon entry of `constrain`",
+            )
+    }
+
+    /// We say that blocklisted items use all of their template parameters. The
+    /// blocklisted type is most likely implemented explicitly by the user,
+    /// since it won't be in the generated bindings, and we don't know exactly
+    /// what they'll to with template parameters, but we can push the issue down
+    /// the line to them.
+    fn constrain_instantiation_of_blocklisted_template(
+        &self,
+        this_id: ItemId,
+        used_by_this_id: &mut ItemSet,
+        instantiation: &TemplateInstantiation,
+    ) {
+        trace!(
+            "    instantiation of blocklisted template, uses all template \
+             arguments"
+        );
+
+        let args = instantiation
+            .template_arguments()
+            .iter()
+            .map(|a| {
+                a.into_resolver()
+                    .through_type_refs()
+                    .through_type_aliases()
+                    .resolve(self.ctx)
+                    .id()
+            })
+            .filter(|a| *a != this_id)
+            .flat_map(|a| {
+                self.used
+                    .get(&a)
+                    .expect("Should have a used entry for the template arg")
+                    .as_ref()
+                    .expect(
+                        "Because a != this_id, and all used template \
+                         param sets other than this_id's are `Some`, \
+                         a's used template param set should be `Some`",
+                    )
+                    .iter()
+                    .cloned()
+            });
+
+        used_by_this_id.extend(args);
+    }
+
+    /// A template instantiation's concrete template argument is only used if
+    /// the template definition uses the corresponding template parameter.
+    fn constrain_instantiation(
+        &self,
+        this_id: ItemId,
+        used_by_this_id: &mut ItemSet,
+        instantiation: &TemplateInstantiation,
+    ) {
+        trace!("    template instantiation");
+
+        let decl = self.ctx.resolve_type(instantiation.template_definition());
+        let args = instantiation.template_arguments();
+
+        let params = decl.self_template_params(self.ctx);
+
+        debug_assert!(this_id != instantiation.template_definition());
+        let used_by_def = self.used
+            .get(&instantiation.template_definition().into())
+            .expect("Should have a used entry for instantiation's template definition")
+            .as_ref()
+            .expect("And it should be Some because only this_id's set is None, and an \
+                     instantiation's template definition should never be the \
+                     instantiation itself");
+
+        for (arg, param) in args.iter().zip(params.iter()) {
+            trace!(
+                "      instantiation's argument {:?} is used if definition's \
+                 parameter {:?} is used",
+                arg,
+                param
+            );
+
+            if used_by_def.contains(&param.into()) {
+                trace!("        param is used by template definition");
+
+                let arg = arg
+                    .into_resolver()
+                    .through_type_refs()
+                    .through_type_aliases()
+                    .resolve(self.ctx)
+                    .id();
+
+                if arg == this_id {
+                    continue;
+                }
+
+                let used_by_arg = self
+                    .used
+                    .get(&arg)
+                    .expect("Should have a used entry for the template arg")
+                    .as_ref()
+                    .expect(
+                        "Because arg != this_id, and all used template \
+                         param sets other than this_id's are `Some`, \
+                         arg's used template param set should be \
+                         `Some`",
+                    )
+                    .iter()
+                    .cloned();
+                used_by_this_id.extend(used_by_arg);
+            }
+        }
+    }
+
+    /// The join operation on our lattice: the set union of all of this ID's
+    /// successors.
+    fn constrain_join(&self, used_by_this_id: &mut ItemSet, item: &Item) {
+        trace!("    other item: join with successors' usage");
+
+        item.trace(
+            self.ctx,
+            &mut |sub_id, edge_kind| {
+                // Ignore ourselves, since union with ourself is a
+                // no-op. Ignore edges that aren't relevant to the
+                // analysis.
+                if sub_id == item.id() || !Self::consider_edge(edge_kind) {
+                    return;
+                }
+
+                let used_by_sub_id = self
+                    .used
+                    .get(&sub_id)
+                    .expect("Should have a used set for the sub_id successor")
+                    .as_ref()
+                    .expect(
+                        "Because sub_id != id, and all used template \
+                         param sets other than id's are `Some`, \
+                         sub_id's used template param set should be \
+                         `Some`",
+                    )
+                    .iter()
+                    .cloned();
+
+                trace!(
+                    "      union with {:?}'s usage: {:?}",
+                    sub_id,
+                    used_by_sub_id.clone().collect::<Vec<_>>()
+                );
+
+                used_by_this_id.extend(used_by_sub_id);
+            },
+            &(),
+        );
+    }
+}
+
+impl<'ctx> MonotoneFramework for UsedTemplateParameters<'ctx> {
+    type Node = ItemId;
+    type Extra = &'ctx BindgenContext;
+    type Output = HashMap<ItemId, ItemSet>;
+
+    fn new(ctx: &'ctx BindgenContext) -> UsedTemplateParameters<'ctx> {
+        let mut used = HashMap::default();
+        let mut dependencies = HashMap::default();
+        let allowlisted_items: HashSet<_> =
+            ctx.allowlisted_items().iter().cloned().collect();
+
+        let allowlisted_and_blocklisted_items: ItemSet = allowlisted_items
+            .iter()
+            .cloned()
+            .flat_map(|i| {
+                let mut reachable = vec![i];
+                i.trace(
+                    ctx,
+                    &mut |s, _| {
+                        reachable.push(s);
+                    },
+                    &(),
+                );
+                reachable
+            })
+            .collect();
+
+        for item in allowlisted_and_blocklisted_items {
+            dependencies.entry(item).or_insert_with(Vec::new);
+            used.entry(item).or_insert_with(|| Some(ItemSet::new()));
+
+            {
+                // We reverse our natural IR graph edges to find dependencies
+                // between nodes.
+                item.trace(
+                    ctx,
+                    &mut |sub_item: ItemId, _| {
+                        used.entry(sub_item)
+                            .or_insert_with(|| Some(ItemSet::new()));
+                        dependencies
+                            .entry(sub_item)
+                            .or_insert_with(Vec::new)
+                            .push(item);
+                    },
+                    &(),
+                );
+            }
+
+            // Additionally, whether a template instantiation's template
+            // arguments are used depends on whether the template declaration's
+            // generic template parameters are used.
+            let item_kind =
+                ctx.resolve_item(item).as_type().map(|ty| ty.kind());
+            if let Some(TypeKind::TemplateInstantiation(inst)) = item_kind {
+                let decl = ctx.resolve_type(inst.template_definition());
+                let args = inst.template_arguments();
+
+                // Although template definitions should always have
+                // template parameters, there is a single exception:
+                // opaque templates. Hence the unwrap_or.
+                let params = decl.self_template_params(ctx);
+
+                for (arg, param) in args.iter().zip(params.iter()) {
+                    let arg = arg
+                        .into_resolver()
+                        .through_type_aliases()
+                        .through_type_refs()
+                        .resolve(ctx)
+                        .id();
+
+                    let param = param
+                        .into_resolver()
+                        .through_type_aliases()
+                        .through_type_refs()
+                        .resolve(ctx)
+                        .id();
+
+                    used.entry(arg).or_insert_with(|| Some(ItemSet::new()));
+                    used.entry(param).or_insert_with(|| Some(ItemSet::new()));
+
+                    dependencies
+                        .entry(arg)
+                        .or_insert_with(Vec::new)
+                        .push(param);
+                }
+            }
+        }
+
+        if cfg!(feature = "__testing_only_extra_assertions") {
+            // Invariant: The `used` map has an entry for every allowlisted
+            // item, as well as all explicitly blocklisted items that are
+            // reachable from allowlisted items.
+            //
+            // Invariant: the `dependencies` map has an entry for every
+            // allowlisted item.
+            //
+            // (This is so that every item we call `constrain` on is guaranteed
+            // to have a set of template parameters, and we can allow
+            // blocklisted templates to use all of their parameters).
+            for item in allowlisted_items.iter() {
+                extra_assert!(used.contains_key(item));
+                extra_assert!(dependencies.contains_key(item));
+                item.trace(
+                    ctx,
+                    &mut |sub_item, _| {
+                        extra_assert!(used.contains_key(&sub_item));
+                        extra_assert!(dependencies.contains_key(&sub_item));
+                    },
+                    &(),
+                )
+            }
+        }
+
+        UsedTemplateParameters {
+            ctx,
+            used,
+            dependencies,
+            allowlisted_items,
+        }
+    }
+
+    fn initial_worklist(&self) -> Vec<ItemId> {
+        // The transitive closure of all allowlisted items, including explicitly
+        // blocklisted items.
+        self.ctx
+            .allowlisted_items()
+            .iter()
+            .cloned()
+            .flat_map(|i| {
+                let mut reachable = vec![i];
+                i.trace(
+                    self.ctx,
+                    &mut |s, _| {
+                        reachable.push(s);
+                    },
+                    &(),
+                );
+                reachable
+            })
+            .collect()
+    }
+
+    fn constrain(&mut self, id: ItemId) -> ConstrainResult {
+        // Invariant: all hash map entries' values are `Some` upon entering and
+        // exiting this method.
+        extra_assert!(self.used.values().all(|v| v.is_some()));
+
+        // Take the set for this ID out of the hash map while we mutate it based
+        // on other hash map entries. We *must* put it back into the hash map at
+        // the end of this method. This allows us to side-step HashMap's lack of
+        // an analog to slice::split_at_mut.
+        let mut used_by_this_id = self.take_this_id_usage_set(id);
+
+        trace!("constrain {:?}", id);
+        trace!("  initially, used set is {:?}", used_by_this_id);
+
+        let original_len = used_by_this_id.len();
+
+        let item = self.ctx.resolve_item(id);
+        let ty_kind = item.as_type().map(|ty| ty.kind());
+        match ty_kind {
+            // Named template type parameters trivially use themselves.
+            Some(&TypeKind::TypeParam) => {
+                trace!("    named type, trivially uses itself");
+                used_by_this_id.insert(id);
+            }
+            // Template instantiations only use their template arguments if the
+            // template definition uses the corresponding template parameter.
+            Some(TypeKind::TemplateInstantiation(inst)) => {
+                if self
+                    .allowlisted_items
+                    .contains(&inst.template_definition().into())
+                {
+                    self.constrain_instantiation(
+                        id,
+                        &mut used_by_this_id,
+                        inst,
+                    );
+                } else {
+                    self.constrain_instantiation_of_blocklisted_template(
+                        id,
+                        &mut used_by_this_id,
+                        inst,
+                    );
+                }
+            }
+            // Otherwise, add the union of each of its referent item's template
+            // parameter usage.
+            _ => self.constrain_join(&mut used_by_this_id, item),
+        }
+
+        trace!("  finally, used set is {:?}", used_by_this_id);
+
+        let new_len = used_by_this_id.len();
+        assert!(
+            new_len >= original_len,
+            "This is the property that ensures this function is monotone -- \
+             if it doesn't hold, the analysis might never terminate!"
+        );
+
+        // Put the set back in the hash map and restore our invariant.
+        debug_assert!(self.used[&id].is_none());
+        self.used.insert(id, Some(used_by_this_id));
+        extra_assert!(self.used.values().all(|v| v.is_some()));
+
+        if new_len != original_len {
+            ConstrainResult::Changed
+        } else {
+            ConstrainResult::Same
+        }
+    }
+
+    fn each_depending_on<F>(&self, item: ItemId, mut f: F)
+    where
+        F: FnMut(ItemId),
+    {
+        if let Some(edges) = self.dependencies.get(&item) {
+            for item in edges {
+                trace!("enqueue {:?} into worklist", item);
+                f(*item);
+            }
+        }
+    }
+}
+
+impl<'ctx> From<UsedTemplateParameters<'ctx>> for HashMap<ItemId, ItemSet> {
+    fn from(used_templ_params: UsedTemplateParameters<'ctx>) -> Self {
+        used_templ_params
+            .used
+            .into_iter()
+            .map(|(k, v)| (k, v.unwrap()))
+            .collect()
+    }
+}
diff --git a/third_party/rust/bindgen/ir/annotations.rs b/third_party/rust/bindgen/ir/annotations.rs
new file mode 100644
index 0000000000..d085f5c574
--- /dev/null
+++ b/third_party/rust/bindgen/ir/annotations.rs
@@ -0,0 +1,256 @@
+//! Types and functions related to bindgen annotation comments.
+//!
+//! Users can add annotations in doc comments to types that they would like to
+//! replace other types with, mark as opaque, etc. This module deals with all of
+//! that stuff.
+
+use std::str::FromStr;
+
+use crate::clang;
+
+/// What kind of visibility modifer should be used for a struct or field?
+#[derive(Copy, PartialEq, Eq, PartialOrd, Ord, Clone, Debug)]
+pub enum FieldVisibilityKind {
+    /// Fields are marked as private, i.e., struct Foo {bar: bool}
+    Private,
+    /// Fields are marked as crate public, i.e., struct Foo {pub(crate) bar: bool}
+    PublicCrate,
+    /// Fields are marked as public, i.e., struct Foo {pub bar: bool}
+    Public,
+}
+
+impl FromStr for FieldVisibilityKind {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "private" => Ok(Self::Private),
+            "crate" => Ok(Self::PublicCrate),
+            "public" => Ok(Self::Public),
+            _ => Err(format!("Invalid visibility kind: `{}`", s)),
+        }
+    }
+}
+
+impl std::fmt::Display for FieldVisibilityKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let s = match self {
+            FieldVisibilityKind::Private => "private",
+            FieldVisibilityKind::PublicCrate => "crate",
+            FieldVisibilityKind::Public => "public",
+        };
+
+        s.fmt(f)
+    }
+}
+
+impl Default for FieldVisibilityKind {
+    fn default() -> Self {
+        FieldVisibilityKind::Public
+    }
+}
+
+/// What kind of accessor should we provide for a field?
+#[derive(Copy, PartialEq, Eq, Clone, Debug)]
+pub(crate) enum FieldAccessorKind {
+    /// No accessor.
+    None,
+    /// Plain accessor.
+    Regular,
+    /// Unsafe accessor.
+    Unsafe,
+    /// Immutable accessor.
+    Immutable,
+}
+
+/// Annotations for a given item, or a field.
+///
+/// You can see the kind of comments that are accepted in the [Doxygen documentation](https://www.doxygen.nl/manual/docblocks.html).
+#[derive(Default, Clone, PartialEq, Eq, Debug)]
+pub(crate) struct Annotations {
+    /// Whether this item is marked as opaque. Only applies to types.
+    opaque: bool,
+    /// Whether this item should be hidden from the output. Only applies to
+    /// types, or enum variants.
+    hide: bool,
+    /// Whether this type should be replaced by another. The name is a
+    /// namespace-aware path.
+    use_instead_of: Option<Vec<String>>,
+    /// Manually disable deriving copy/clone on this type. Only applies to
+    /// struct or union types.
+    disallow_copy: bool,
+    /// Manually disable deriving debug on this type.
+    disallow_debug: bool,
+    /// Manually disable deriving/implement default on this type.
+    disallow_default: bool,
+    /// Whether to add a `#[must_use]` annotation to this type.
+    must_use_type: bool,
+    /// Visibility of struct fields. You can set this on
+    /// structs (it will apply to all the fields), or individual fields.
+    visibility_kind: Option<FieldVisibilityKind>,
+    /// The kind of accessor this field will have. Also can be applied to
+    /// structs so all the fields inside share it by default.
+    accessor_kind: Option<FieldAccessorKind>,
+    /// Whether this enum variant should be constified.
+    ///
+    /// This is controlled by the `constant` attribute, this way:
+    ///
+    /// ```cpp
+    /// enum Foo {
+    ///     Bar = 0, /**< <div rustbindgen constant></div> */
+    ///     Baz = 0,
+    /// };
+    /// ```
+    ///
+    /// In that case, bindgen will generate a constant for `Bar` instead of
+    /// `Baz`.
+    constify_enum_variant: bool,
+    /// List of explicit derives for this type.
+    derives: Vec<String>,
+}
+
+fn parse_accessor(s: &str) -> FieldAccessorKind {
+    match s {
+        "false" => FieldAccessorKind::None,
+        "unsafe" => FieldAccessorKind::Unsafe,
+        "immutable" => FieldAccessorKind::Immutable,
+        _ => FieldAccessorKind::Regular,
+    }
+}
+
+impl Annotations {
+    /// Construct new annotations for the given cursor and its bindgen comments
+    /// (if any).
+    pub(crate) fn new(cursor: &clang::Cursor) -> Option<Annotations> {
+        let mut anno = Annotations::default();
+        let mut matched_one = false;
+        anno.parse(&cursor.comment(), &mut matched_one);
+
+        if matched_one {
+            Some(anno)
+        } else {
+            None
+        }
+    }
+
+    /// Should this type be hidden?
+    pub(crate) fn hide(&self) -> bool {
+        self.hide
+    }
+
+    /// Should this type be opaque?
+    pub(crate) fn opaque(&self) -> bool {
+        self.opaque
+    }
+
+    /// For a given type, indicates the type it should replace.
+    ///
+    /// For example, in the following code:
+    ///
+    /// ```cpp
+    ///
+    /// /** <div rustbindgen replaces="Bar"></div> */
+    /// struct Foo { int x; };
+    ///
+    /// struct Bar { char foo; };
+    /// ```
+    ///
+    /// the generated code would look something like:
+    ///
+    /// ```
+    /// /** <div rustbindgen replaces="Bar"></div> */
+    /// struct Bar {
+    ///     x: ::std::os::raw::c_int,
+    /// };
+    /// ```
+    ///
+    /// That is, code for `Foo` is used to generate `Bar`.
+    pub(crate) fn use_instead_of(&self) -> Option<&[String]> {
+        self.use_instead_of.as_deref()
+    }
+
+    /// The list of derives that have been specified in this annotation.
+    pub(crate) fn derives(&self) -> &[String] {
+        &self.derives
+    }
+
+    /// Should we avoid implementing the `Copy` trait?
+    pub(crate) fn disallow_copy(&self) -> bool {
+        self.disallow_copy
+    }
+
+    /// Should we avoid implementing the `Debug` trait?
+    pub(crate) fn disallow_debug(&self) -> bool {
+        self.disallow_debug
+    }
+
+    /// Should we avoid implementing the `Default` trait?
+    pub(crate) fn disallow_default(&self) -> bool {
+        self.disallow_default
+    }
+
+    /// Should this type get a `#[must_use]` annotation?
+    pub(crate) fn must_use_type(&self) -> bool {
+        self.must_use_type
+    }
+
+    /// What kind of accessors should we provide for this type's fields?
+    pub(crate) fn visibility_kind(&self) -> Option<FieldVisibilityKind> {
+        self.visibility_kind
+    }
+
+    /// What kind of accessors should we provide for this type's fields?
+    pub(crate) fn accessor_kind(&self) -> Option<FieldAccessorKind> {
+        self.accessor_kind
+    }
+
+    fn parse(&mut self, comment: &clang::Comment, matched: &mut bool) {
+        use clang_sys::CXComment_HTMLStartTag;
+        if comment.kind() == CXComment_HTMLStartTag &&
+            comment.get_tag_name() == "div" &&
+            comment
+                .get_tag_attrs()
+                .next()
+                .map_or(false, |attr| attr.name == "rustbindgen")
+        {
+            *matched = true;
+            for attr in comment.get_tag_attrs() {
+                match attr.name.as_str() {
+                    "opaque" => self.opaque = true,
+                    "hide" => self.hide = true,
+                    "nocopy" => self.disallow_copy = true,
+                    "nodebug" => self.disallow_debug = true,
+                    "nodefault" => self.disallow_default = true,
+                    "mustusetype" => self.must_use_type = true,
+                    "replaces" => {
+                        self.use_instead_of = Some(
+                            attr.value.split("::").map(Into::into).collect(),
+                        )
+                    }
+                    "derive" => self.derives.push(attr.value),
+                    "private" => {
+                        self.visibility_kind = if attr.value != "false" {
+                            Some(FieldVisibilityKind::Private)
+                        } else {
+                            Some(FieldVisibilityKind::Public)
+                        };
+                    }
+                    "accessor" => {
+                        self.accessor_kind = Some(parse_accessor(&attr.value))
+                    }
+                    "constant" => self.constify_enum_variant = true,
+                    _ => {}
+                }
+            }
+        }
+
+        for child in comment.get_children() {
+            self.parse(&child, matched);
+        }
+    }
+
+    /// Returns whether we've parsed a "constant" attribute.
+    pub(crate) fn constify_enum_variant(&self) -> bool {
+        self.constify_enum_variant
+    }
+}
diff --git a/third_party/rust/bindgen/ir/comment.rs b/third_party/rust/bindgen/ir/comment.rs
new file mode 100644
index 0000000000..7b6f105a4d
--- /dev/null
+++ b/third_party/rust/bindgen/ir/comment.rs
@@ -0,0 +1,100 @@
+//! Utilities for manipulating C/C++ comments.
+
+/// The type of a comment.
+#[derive(Debug, PartialEq, Eq)]
+enum Kind {
+    /// A `///` comment, or something of the like.
+    /// All lines in a comment should start with the same symbol.
+    SingleLines,
+    /// A `/**` comment, where each other line can start with `*` and the
+    /// entire block ends with `*/`.
+    MultiLine,
+}
+
+/// Preprocesses a C/C++ comment so that it is a valid Rust comment.
+pub(crate) fn preprocess(comment: &str) -> String {
+    match self::kind(comment) {
+        Some(Kind::SingleLines) => preprocess_single_lines(comment),
+        Some(Kind::MultiLine) => preprocess_multi_line(comment),
+        None => comment.to_owned(),
+    }
+}
+
+/// Gets the kind of the doc comment, if it is one.
+fn kind(comment: &str) -> Option<Kind> {
+    if comment.starts_with("/*") {
+        Some(Kind::MultiLine)
+    } else if comment.starts_with("//") {
+        Some(Kind::SingleLines)
+    } else {
+        None
+    }
+}
+
+/// Preprocesses multiple single line comments.
+///
+/// Handles lines starting with both `//` and `///`.
+fn preprocess_single_lines(comment: &str) -> String {
+    debug_assert!(comment.starts_with("//"), "comment is not single line");
+
+    let lines: Vec<_> = comment
+        .lines()
+        .map(|l| l.trim().trim_start_matches('/'))
+        .collect();
+    lines.join("\n")
+}
+
+fn preprocess_multi_line(comment: &str) -> String {
+    let comment = comment
+        .trim_start_matches('/')
+        .trim_end_matches('/')
+        .trim_end_matches('*');
+
+    // Strip any potential `*` characters preceding each line.
+    let mut lines: Vec<_> = comment
+        .lines()
+        .map(|line| line.trim().trim_start_matches('*').trim_start_matches('!'))
+        .skip_while(|line| line.trim().is_empty()) // Skip the first empty lines.
+        .collect();
+
+    // Remove the trailing line corresponding to the `*/`.
+    if lines.last().map_or(false, |l| l.trim().is_empty()) {
+        lines.pop();
+    }
+
+    lines.join("\n")
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn picks_up_single_and_multi_line_doc_comments() {
+        assert_eq!(kind("/// hello"), Some(Kind::SingleLines));
+        assert_eq!(kind("/** world */"), Some(Kind::MultiLine));
+    }
+
+    #[test]
+    fn processes_single_lines_correctly() {
+        assert_eq!(preprocess("///"), "");
+        assert_eq!(preprocess("/// hello"), " hello");
+        assert_eq!(preprocess("// hello"), " hello");
+        assert_eq!(preprocess("//    hello"), "    hello");
+    }
+
+    #[test]
+    fn processes_multi_lines_correctly() {
+        assert_eq!(preprocess("/**/"), "");
+
+        assert_eq!(
+            preprocess("/** hello \n * world \n * foo \n */"),
+            " hello\n world\n foo"
+        );
+
+        assert_eq!(
+            preprocess("/**\nhello\n*world\n*foo\n*/"),
+            "hello\nworld\nfoo"
+        );
+    }
+}
diff --git a/third_party/rust/bindgen/ir/comp.rs b/third_party/rust/bindgen/ir/comp.rs
new file mode 100644
index 0000000000..fed6ba8ac8
--- /dev/null
+++ b/third_party/rust/bindgen/ir/comp.rs
@@ -0,0 +1,1896 @@
+//! Compound types (unions and structs) in our intermediate representation.
+
+use itertools::Itertools;
+
+use super::analysis::Sizedness;
+use super::annotations::Annotations;
+use super::context::{BindgenContext, FunctionId, ItemId, TypeId, VarId};
+use super::dot::DotAttributes;
+use super::item::{IsOpaque, Item};
+use super::layout::Layout;
+use super::template::TemplateParameters;
+use super::traversal::{EdgeKind, Trace, Tracer};
+use super::ty::RUST_DERIVE_IN_ARRAY_LIMIT;
+use crate::clang;
+use crate::codegen::struct_layout::{align_to, bytes_from_bits_pow2};
+use crate::ir::derive::CanDeriveCopy;
+use crate::parse::ParseError;
+use crate::HashMap;
+use crate::NonCopyUnionStyle;
+use std::cmp;
+use std::io;
+use std::mem;
+
+/// The kind of compound type.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum CompKind {
+    /// A struct.
+    Struct,
+    /// A union.
+    Union,
+}
+
+/// The kind of C++ method.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum MethodKind {
+    /// A constructor. We represent it as method for convenience, to avoid code
+    /// duplication.
+    Constructor,
+    /// A destructor.
+    Destructor,
+    /// A virtual destructor.
+    VirtualDestructor {
+        /// Whether it's pure virtual.
+        pure_virtual: bool,
+    },
+    /// A static method.
+    Static,
+    /// A normal method.
+    Normal,
+    /// A virtual method.
+    Virtual {
+        /// Whether it's pure virtual.
+        pure_virtual: bool,
+    },
+}
+
+impl MethodKind {
+    /// Is this a destructor method?
+    pub(crate) fn is_destructor(&self) -> bool {
+        matches!(
+            *self,
+            MethodKind::Destructor | MethodKind::VirtualDestructor { .. }
+        )
+    }
+
+    /// Is this a pure virtual method?
+    pub(crate) fn is_pure_virtual(&self) -> bool {
+        match *self {
+            MethodKind::Virtual { pure_virtual } |
+            MethodKind::VirtualDestructor { pure_virtual } => pure_virtual,
+            _ => false,
+        }
+    }
+}
+
+/// A struct representing a C++ method, either static, normal, or virtual.
+#[derive(Debug)]
+pub(crate) struct Method {
+    kind: MethodKind,
+    /// The signature of the method. Take into account this is not a `Type`
+    /// item, but a `Function` one.
+    ///
+    /// This is tricky and probably this field should be renamed.
+    signature: FunctionId,
+    is_const: bool,
+}
+
+impl Method {
+    /// Construct a new `Method`.
+    pub(crate) fn new(
+        kind: MethodKind,
+        signature: FunctionId,
+        is_const: bool,
+    ) -> Self {
+        Method {
+            kind,
+            signature,
+            is_const,
+        }
+    }
+
+    /// What kind of method is this?
+    pub(crate) fn kind(&self) -> MethodKind {
+        self.kind
+    }
+
+    /// Is this a constructor?
+    pub(crate) fn is_constructor(&self) -> bool {
+        self.kind == MethodKind::Constructor
+    }
+
+    /// Is this a virtual method?
+    pub(crate) fn is_virtual(&self) -> bool {
+        matches!(
+            self.kind,
+            MethodKind::Virtual { .. } | MethodKind::VirtualDestructor { .. }
+        )
+    }
+
+    /// Is this a static method?
+    pub(crate) fn is_static(&self) -> bool {
+        self.kind == MethodKind::Static
+    }
+
+    /// Get the ID for the `Function` signature for this method.
+    pub(crate) fn signature(&self) -> FunctionId {
+        self.signature
+    }
+
+    /// Is this a const qualified method?
+    pub(crate) fn is_const(&self) -> bool {
+        self.is_const
+    }
+}
+
+/// Methods common to the various field types.
+pub(crate) trait FieldMethods {
+    /// Get the name of this field.
+    fn name(&self) -> Option<&str>;
+
+    /// Get the type of this field.
+    fn ty(&self) -> TypeId;
+
+    /// Get the comment for this field.
+    fn comment(&self) -> Option<&str>;
+
+    /// If this is a bitfield, how many bits does it need?
+    fn bitfield_width(&self) -> Option<u32>;
+
+    /// Is this feild declared public?
+    fn is_public(&self) -> bool;
+
+    /// Get the annotations for this field.
+    fn annotations(&self) -> &Annotations;
+
+    /// The offset of the field (in bits)
+    fn offset(&self) -> Option<usize>;
+}
+
+/// A contiguous set of logical bitfields that live within the same physical
+/// allocation unit. See 9.2.4 [class.bit] in the C++ standard and [section
+/// 2.4.II.1 in the Itanium C++
+/// ABI](http://itanium-cxx-abi.github.io/cxx-abi/abi.html#class-types).
+#[derive(Debug)]
+pub(crate) struct BitfieldUnit {
+    nth: usize,
+    layout: Layout,
+    bitfields: Vec<Bitfield>,
+}
+
+impl BitfieldUnit {
+    /// Get the 1-based index of this bitfield unit within its containing
+    /// struct. Useful for generating a Rust struct's field name for this unit
+    /// of bitfields.
+    pub(crate) fn nth(&self) -> usize {
+        self.nth
+    }
+
+    /// Get the layout within which these bitfields reside.
+    pub(crate) fn layout(&self) -> Layout {
+        self.layout
+    }
+
+    /// Get the bitfields within this unit.
+    pub(crate) fn bitfields(&self) -> &[Bitfield] {
+        &self.bitfields
+    }
+}
+
+/// A struct representing a C++ field.
+#[derive(Debug)]
+pub(crate) enum Field {
+    /// A normal data member.
+    DataMember(FieldData),
+
+    /// A physical allocation unit containing many logical bitfields.
+    Bitfields(BitfieldUnit),
+}
+
+impl Field {
+    /// Get this field's layout.
+    pub(crate) fn layout(&self, ctx: &BindgenContext) -> Option<Layout> {
+        match *self {
+            Field::Bitfields(BitfieldUnit { layout, .. }) => Some(layout),
+            Field::DataMember(ref data) => {
+                ctx.resolve_type(data.ty).layout(ctx)
+            }
+        }
+    }
+}
+
+impl Trace for Field {
+    type Extra = ();
+
+    fn trace<T>(&self, _: &BindgenContext, tracer: &mut T, _: &())
+    where
+        T: Tracer,
+    {
+        match *self {
+            Field::DataMember(ref data) => {
+                tracer.visit_kind(data.ty.into(), EdgeKind::Field);
+            }
+            Field::Bitfields(BitfieldUnit { ref bitfields, .. }) => {
+                for bf in bitfields {
+                    tracer.visit_kind(bf.ty().into(), EdgeKind::Field);
+                }
+            }
+        }
+    }
+}
+
+impl DotAttributes for Field {
+    fn dot_attributes<W>(
+        &self,
+        ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        match *self {
+            Field::DataMember(ref data) => data.dot_attributes(ctx, out),
+            Field::Bitfields(BitfieldUnit {
+                layout,
+                ref bitfields,
+                ..
+            }) => {
+                writeln!(
+                    out,
+                    r#"<tr>
+                              <td>bitfield unit</td>
+                              <td>
+                                <table border="0">
+                                  <tr>
+                                    <td>unit.size</td><td>{}</td>
+                                  </tr>
+                                  <tr>
+                                    <td>unit.align</td><td>{}</td>
+                                  </tr>
+                         "#,
+                    layout.size, layout.align
+                )?;
+                for bf in bitfields {
+                    bf.dot_attributes(ctx, out)?;
+                }
+                writeln!(out, "</table></td></tr>")
+            }
+        }
+    }
+}
+
+impl DotAttributes for FieldData {
+    fn dot_attributes<W>(
+        &self,
+        _ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        writeln!(
+            out,
+            "<tr><td>{}</td><td>{:?}</td></tr>",
+            self.name().unwrap_or("(anonymous)"),
+            self.ty()
+        )
+    }
+}
+
+impl DotAttributes for Bitfield {
+    fn dot_attributes<W>(
+        &self,
+        _ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        writeln!(
+            out,
+            "<tr><td>{} : {}</td><td>{:?}</td></tr>",
+            self.name().unwrap_or("(anonymous)"),
+            self.width(),
+            self.ty()
+        )
+    }
+}
+
+/// A logical bitfield within some physical bitfield allocation unit.
+#[derive(Debug)]
+pub(crate) struct Bitfield {
+    /// Index of the bit within this bitfield's allocation unit where this
+    /// bitfield's bits begin.
+    offset_into_unit: usize,
+
+    /// The field data for this bitfield.
+    data: FieldData,
+
+    /// Name of the generated Rust getter for this bitfield.
+    ///
+    /// Should be assigned before codegen.
+    getter_name: Option<String>,
+
+    /// Name of the generated Rust setter for this bitfield.
+    ///
+    /// Should be assigned before codegen.
+    setter_name: Option<String>,
+}
+
+impl Bitfield {
+    /// Construct a new bitfield.
+    fn new(offset_into_unit: usize, raw: RawField) -> Bitfield {
+        assert!(raw.bitfield_width().is_some());
+
+        Bitfield {
+            offset_into_unit,
+            data: raw.0,
+            getter_name: None,
+            setter_name: None,
+        }
+    }
+
+    /// Get the index of the bit within this bitfield's allocation unit where
+    /// this bitfield begins.
+    pub(crate) fn offset_into_unit(&self) -> usize {
+        self.offset_into_unit
+    }
+
+    /// Get the bit width of this bitfield.
+    pub(crate) fn width(&self) -> u32 {
+        self.data.bitfield_width().unwrap()
+    }
+
+    /// Name of the generated Rust getter for this bitfield.
+    ///
+    /// Panics if called before assigning bitfield accessor names or if
+    /// this bitfield have no name.
+    pub(crate) fn getter_name(&self) -> &str {
+        assert!(
+            self.name().is_some(),
+            "`Bitfield::getter_name` called on anonymous field"
+        );
+        self.getter_name.as_ref().expect(
+            "`Bitfield::getter_name` should only be called after\
+             assigning bitfield accessor names",
+        )
+    }
+
+    /// Name of the generated Rust setter for this bitfield.
+    ///
+    /// Panics if called before assigning bitfield accessor names or if
+    /// this bitfield have no name.
+    pub(crate) fn setter_name(&self) -> &str {
+        assert!(
+            self.name().is_some(),
+            "`Bitfield::setter_name` called on anonymous field"
+        );
+        self.setter_name.as_ref().expect(
+            "`Bitfield::setter_name` should only be called\
+             after assigning bitfield accessor names",
+        )
+    }
+}
+
+impl FieldMethods for Bitfield {
+    fn name(&self) -> Option<&str> {
+        self.data.name()
+    }
+
+    fn ty(&self) -> TypeId {
+        self.data.ty()
+    }
+
+    fn comment(&self) -> Option<&str> {
+        self.data.comment()
+    }
+
+    fn bitfield_width(&self) -> Option<u32> {
+        self.data.bitfield_width()
+    }
+
+    fn is_public(&self) -> bool {
+        self.data.is_public()
+    }
+
+    fn annotations(&self) -> &Annotations {
+        self.data.annotations()
+    }
+
+    fn offset(&self) -> Option<usize> {
+        self.data.offset()
+    }
+}
+
+/// A raw field might be either of a plain data member or a bitfield within a
+/// bitfield allocation unit, but we haven't processed it and determined which
+/// yet (which would involve allocating it into a bitfield unit if it is a
+/// bitfield).
+#[derive(Debug)]
+struct RawField(FieldData);
+
+impl RawField {
+    /// Construct a new `RawField`.
+    fn new(
+        name: Option<String>,
+        ty: TypeId,
+        comment: Option<String>,
+        annotations: Option<Annotations>,
+        bitfield_width: Option<u32>,
+        public: bool,
+        offset: Option<usize>,
+    ) -> RawField {
+        RawField(FieldData {
+            name,
+            ty,
+            comment,
+            annotations: annotations.unwrap_or_default(),
+            bitfield_width,
+            public,
+            offset,
+        })
+    }
+}
+
+impl FieldMethods for RawField {
+    fn name(&self) -> Option<&str> {
+        self.0.name()
+    }
+
+    fn ty(&self) -> TypeId {
+        self.0.ty()
+    }
+
+    fn comment(&self) -> Option<&str> {
+        self.0.comment()
+    }
+
+    fn bitfield_width(&self) -> Option<u32> {
+        self.0.bitfield_width()
+    }
+
+    fn is_public(&self) -> bool {
+        self.0.is_public()
+    }
+
+    fn annotations(&self) -> &Annotations {
+        self.0.annotations()
+    }
+
+    fn offset(&self) -> Option<usize> {
+        self.0.offset()
+    }
+}
+
+/// Convert the given ordered set of raw fields into a list of either plain data
+/// members, and/or bitfield units containing multiple bitfields.
+///
+/// If we do not have the layout for a bitfield's type, then we can't reliably
+/// compute its allocation unit. In such cases, we return an error.
+fn raw_fields_to_fields_and_bitfield_units<I>(
+    ctx: &BindgenContext,
+    raw_fields: I,
+    packed: bool,
+) -> Result<(Vec<Field>, bool), ()>
+where
+    I: IntoIterator<Item = RawField>,
+{
+    let mut raw_fields = raw_fields.into_iter().fuse().peekable();
+    let mut fields = vec![];
+    let mut bitfield_unit_count = 0;
+
+    loop {
+        // While we have plain old data members, just keep adding them to our
+        // resulting fields. We introduce a scope here so that we can use
+        // `raw_fields` again after the `by_ref` iterator adaptor is dropped.
+        {
+            let non_bitfields = raw_fields
+                .by_ref()
+                .peeking_take_while(|f| f.bitfield_width().is_none())
+                .map(|f| Field::DataMember(f.0));
+            fields.extend(non_bitfields);
+        }
+
+        // Now gather all the consecutive bitfields. Only consecutive bitfields
+        // may potentially share a bitfield allocation unit with each other in
+        // the Itanium C++ ABI.
+        let mut bitfields = raw_fields
+            .by_ref()
+            .peeking_take_while(|f| f.bitfield_width().is_some())
+            .peekable();
+
+        if bitfields.peek().is_none() {
+            break;
+        }
+
+        bitfields_to_allocation_units(
+            ctx,
+            &mut bitfield_unit_count,
+            &mut fields,
+            bitfields,
+            packed,
+        )?;
+    }
+
+    assert!(
+        raw_fields.next().is_none(),
+        "The above loop should consume all items in `raw_fields`"
+    );
+
+    Ok((fields, bitfield_unit_count != 0))
+}
+
+/// Given a set of contiguous raw bitfields, group and allocate them into
+/// (potentially multiple) bitfield units.
+fn bitfields_to_allocation_units<E, I>(
+    ctx: &BindgenContext,
+    bitfield_unit_count: &mut usize,
+    fields: &mut E,
+    raw_bitfields: I,
+    packed: bool,
+) -> Result<(), ()>
+where
+    E: Extend<Field>,
+    I: IntoIterator<Item = RawField>,
+{
+    assert!(ctx.collected_typerefs());
+
+    // NOTE: What follows is reverse-engineered from LLVM's
+    // lib/AST/RecordLayoutBuilder.cpp
+    //
+    // FIXME(emilio): There are some differences between Microsoft and the
+    // Itanium ABI, but we'll ignore those and stick to Itanium for now.
+    //
+    // Also, we need to handle packed bitfields and stuff.
+    //
+    // TODO(emilio): Take into account C++'s wide bitfields, and
+    // packing, sigh.
+
+    fn flush_allocation_unit<E>(
+        fields: &mut E,
+        bitfield_unit_count: &mut usize,
+        unit_size_in_bits: usize,
+        unit_align_in_bits: usize,
+        bitfields: Vec<Bitfield>,
+        packed: bool,
+    ) where
+        E: Extend<Field>,
+    {
+        *bitfield_unit_count += 1;
+        let align = if packed {
+            1
+        } else {
+            bytes_from_bits_pow2(unit_align_in_bits)
+        };
+        let size = align_to(unit_size_in_bits, 8) / 8;
+        let layout = Layout::new(size, align);
+        fields.extend(Some(Field::Bitfields(BitfieldUnit {
+            nth: *bitfield_unit_count,
+            layout,
+            bitfields,
+        })));
+    }
+
+    let mut max_align = 0;
+    let mut unfilled_bits_in_unit = 0;
+    let mut unit_size_in_bits = 0;
+    let mut unit_align = 0;
+    let mut bitfields_in_unit = vec![];
+
+    // TODO(emilio): Determine this from attributes or pragma ms_struct
+    // directives. Also, perhaps we should check if the target is MSVC?
+    const is_ms_struct: bool = false;
+
+    for bitfield in raw_bitfields {
+        let bitfield_width = bitfield.bitfield_width().unwrap() as usize;
+        let bitfield_layout =
+            ctx.resolve_type(bitfield.ty()).layout(ctx).ok_or(())?;
+        let bitfield_size = bitfield_layout.size;
+        let bitfield_align = bitfield_layout.align;
+
+        let mut offset = unit_size_in_bits;
+        if !packed {
+            if is_ms_struct {
+                if unit_size_in_bits != 0 &&
+                    (bitfield_width == 0 ||
+                        bitfield_width > unfilled_bits_in_unit)
+                {
+                    // We've reached the end of this allocation unit, so flush it
+                    // and its bitfields.
+                    unit_size_in_bits =
+                        align_to(unit_size_in_bits, unit_align * 8);
+                    flush_allocation_unit(
+                        fields,
+                        bitfield_unit_count,
+                        unit_size_in_bits,
+                        unit_align,
+                        mem::take(&mut bitfields_in_unit),
+                        packed,
+                    );
+
+                    // Now we're working on a fresh bitfield allocation unit, so reset
+                    // the current unit size and alignment.
+                    offset = 0;
+                    unit_align = 0;
+                }
+            } else if offset != 0 &&
+                (bitfield_width == 0 ||
+                    (offset & (bitfield_align * 8 - 1)) + bitfield_width >
+                        bitfield_size * 8)
+            {
+                offset = align_to(offset, bitfield_align * 8);
+            }
+        }
+
+        // According to the x86[-64] ABI spec: "Unnamed bit-fields’ types do not
+        // affect the alignment of a structure or union". This makes sense: such
+        // bit-fields are only used for padding, and we can't perform an
+        // un-aligned read of something we can't read because we can't even name
+        // it.
+        if bitfield.name().is_some() {
+            max_align = cmp::max(max_align, bitfield_align);
+
+            // NB: The `bitfield_width` here is completely, absolutely
+            // intentional.  Alignment of the allocation unit is based on the
+            // maximum bitfield width, not (directly) on the bitfields' types'
+            // alignment.
+            unit_align = cmp::max(unit_align, bitfield_width);
+        }
+
+        // Always keep all bitfields around. While unnamed bitifields are used
+        // for padding (and usually not needed hereafter), large unnamed
+        // bitfields over their types size cause weird allocation size behavior from clang.
+        // Therefore, all bitfields needed to be kept around in order to check for this
+        // and make the struct opaque in this case
+        bitfields_in_unit.push(Bitfield::new(offset, bitfield));
+
+        unit_size_in_bits = offset + bitfield_width;
+
+        // Compute what the physical unit's final size would be given what we
+        // have seen so far, and use that to compute how many bits are still
+        // available in the unit.
+        let data_size = align_to(unit_size_in_bits, bitfield_align * 8);
+        unfilled_bits_in_unit = data_size - unit_size_in_bits;
+    }
+
+    if unit_size_in_bits != 0 {
+        // Flush the last allocation unit and its bitfields.
+        flush_allocation_unit(
+            fields,
+            bitfield_unit_count,
+            unit_size_in_bits,
+            unit_align,
+            bitfields_in_unit,
+            packed,
+        );
+    }
+
+    Ok(())
+}
+
+/// A compound structure's fields are initially raw, and have bitfields that
+/// have not been grouped into allocation units. During this time, the fields
+/// are mutable and we build them up during parsing.
+///
+/// Then, once resolving typerefs is completed, we compute all structs' fields'
+/// bitfield allocation units, and they remain frozen and immutable forever
+/// after.
+#[derive(Debug)]
+enum CompFields {
+    Before(Vec<RawField>),
+    After {
+        fields: Vec<Field>,
+        has_bitfield_units: bool,
+    },
+    Error,
+}
+
+impl Default for CompFields {
+    fn default() -> CompFields {
+        CompFields::Before(vec![])
+    }
+}
+
+impl CompFields {
+    fn append_raw_field(&mut self, raw: RawField) {
+        match *self {
+            CompFields::Before(ref mut raws) => {
+                raws.push(raw);
+            }
+            _ => {
+                panic!(
+                    "Must not append new fields after computing bitfield allocation units"
+                );
+            }
+        }
+    }
+
+    fn compute_bitfield_units(&mut self, ctx: &BindgenContext, packed: bool) {
+        let raws = match *self {
+            CompFields::Before(ref mut raws) => mem::take(raws),
+            _ => {
+                panic!("Already computed bitfield units");
+            }
+        };
+
+        let result = raw_fields_to_fields_and_bitfield_units(ctx, raws, packed);
+
+        match result {
+            Ok((fields, has_bitfield_units)) => {
+                *self = CompFields::After {
+                    fields,
+                    has_bitfield_units,
+                };
+            }
+            Err(()) => {
+                *self = CompFields::Error;
+            }
+        }
+    }
+
+    fn deanonymize_fields(&mut self, ctx: &BindgenContext, methods: &[Method]) {
+        let fields = match *self {
+            CompFields::After { ref mut fields, .. } => fields,
+            // Nothing to do here.
+            CompFields::Error => return,
+            CompFields::Before(_) => {
+                panic!("Not yet computed bitfield units.");
+            }
+        };
+
+        fn has_method(
+            methods: &[Method],
+            ctx: &BindgenContext,
+            name: &str,
+        ) -> bool {
+            methods.iter().any(|method| {
+                let method_name = ctx.resolve_func(method.signature()).name();
+                method_name == name || ctx.rust_mangle(method_name) == name
+            })
+        }
+
+        struct AccessorNamesPair {
+            getter: String,
+            setter: String,
+        }
+
+        let mut accessor_names: HashMap<String, AccessorNamesPair> = fields
+            .iter()
+            .flat_map(|field| match *field {
+                Field::Bitfields(ref bu) => &*bu.bitfields,
+                Field::DataMember(_) => &[],
+            })
+            .filter_map(|bitfield| bitfield.name())
+            .map(|bitfield_name| {
+                let bitfield_name = bitfield_name.to_string();
+                let getter = {
+                    let mut getter =
+                        ctx.rust_mangle(&bitfield_name).to_string();
+                    if has_method(methods, ctx, &getter) {
+                        getter.push_str("_bindgen_bitfield");
+                    }
+                    getter
+                };
+                let setter = {
+                    let setter = format!("set_{}", bitfield_name);
+                    let mut setter = ctx.rust_mangle(&setter).to_string();
+                    if has_method(methods, ctx, &setter) {
+                        setter.push_str("_bindgen_bitfield");
+                    }
+                    setter
+                };
+                (bitfield_name, AccessorNamesPair { getter, setter })
+            })
+            .collect();
+
+        let mut anon_field_counter = 0;
+        for field in fields.iter_mut() {
+            match *field {
+                Field::DataMember(FieldData { ref mut name, .. }) => {
+                    if name.is_some() {
+                        continue;
+                    }
+
+                    anon_field_counter += 1;
+                    *name = Some(format!(
+                        "{}{}",
+                        ctx.options().anon_fields_prefix,
+                        anon_field_counter
+                    ));
+                }
+                Field::Bitfields(ref mut bu) => {
+                    for bitfield in &mut bu.bitfields {
+                        if bitfield.name().is_none() {
+                            continue;
+                        }
+
+                        if let Some(AccessorNamesPair { getter, setter }) =
+                            accessor_names.remove(bitfield.name().unwrap())
+                        {
+                            bitfield.getter_name = Some(getter);
+                            bitfield.setter_name = Some(setter);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl Trace for CompFields {
+    type Extra = ();
+
+    fn trace<T>(&self, context: &BindgenContext, tracer: &mut T, _: &())
+    where
+        T: Tracer,
+    {
+        match *self {
+            CompFields::Error => {}
+            CompFields::Before(ref fields) => {
+                for f in fields {
+                    tracer.visit_kind(f.ty().into(), EdgeKind::Field);
+                }
+            }
+            CompFields::After { ref fields, .. } => {
+                for f in fields {
+                    f.trace(context, tracer, &());
+                }
+            }
+        }
+    }
+}
+
+/// Common data shared across different field types.
+#[derive(Clone, Debug)]
+pub(crate) struct FieldData {
+    /// The name of the field, empty if it's an unnamed bitfield width.
+    name: Option<String>,
+
+    /// The inner type.
+    ty: TypeId,
+
+    /// The doc comment on the field if any.
+    comment: Option<String>,
+
+    /// Annotations for this field, or the default.
+    annotations: Annotations,
+
+    /// If this field is a bitfield, and how many bits does it contain if it is.
+    bitfield_width: Option<u32>,
+
+    /// If the C++ field is declared `public`
+    public: bool,
+
+    /// The offset of the field (in bits)
+    offset: Option<usize>,
+}
+
+impl FieldMethods for FieldData {
+    fn name(&self) -> Option<&str> {
+        self.name.as_deref()
+    }
+
+    fn ty(&self) -> TypeId {
+        self.ty
+    }
+
+    fn comment(&self) -> Option<&str> {
+        self.comment.as_deref()
+    }
+
+    fn bitfield_width(&self) -> Option<u32> {
+        self.bitfield_width
+    }
+
+    fn is_public(&self) -> bool {
+        self.public
+    }
+
+    fn annotations(&self) -> &Annotations {
+        &self.annotations
+    }
+
+    fn offset(&self) -> Option<usize> {
+        self.offset
+    }
+}
+
+/// The kind of inheritance a base class is using.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) enum BaseKind {
+    /// Normal inheritance, like:
+    ///
+    /// ```cpp
+    /// class A : public B {};
+    /// ```
+    Normal,
+    /// Virtual inheritance, like:
+    ///
+    /// ```cpp
+    /// class A: public virtual B {};
+    /// ```
+    Virtual,
+}
+
+/// A base class.
+#[derive(Clone, Debug)]
+pub(crate) struct Base {
+    /// The type of this base class.
+    pub(crate) ty: TypeId,
+    /// The kind of inheritance we're doing.
+    pub(crate) kind: BaseKind,
+    /// Name of the field in which this base should be stored.
+    pub(crate) field_name: String,
+    /// Whether this base is inherited from publically.
+    pub(crate) is_pub: bool,
+}
+
+impl Base {
+    /// Whether this base class is inheriting virtually.
+    pub(crate) fn is_virtual(&self) -> bool {
+        self.kind == BaseKind::Virtual
+    }
+
+    /// Whether this base class should have it's own field for storage.
+    pub(crate) fn requires_storage(&self, ctx: &BindgenContext) -> bool {
+        // Virtual bases are already taken into account by the vtable
+        // pointer.
+        //
+        // FIXME(emilio): Is this always right?
+        if self.is_virtual() {
+            return false;
+        }
+
+        // NB: We won't include zero-sized types in our base chain because they
+        // would contribute to our size given the dummy field we insert for
+        // zero-sized types.
+        if self.ty.is_zero_sized(ctx) {
+            return false;
+        }
+
+        true
+    }
+
+    /// Whether this base is inherited from publically.
+    pub(crate) fn is_public(&self) -> bool {
+        self.is_pub
+    }
+}
+
+/// A compound type.
+///
+/// Either a struct or union, a compound type is built up from the combination
+/// of fields which also are associated with their own (potentially compound)
+/// type.
+#[derive(Debug)]
+pub(crate) struct CompInfo {
+    /// Whether this is a struct or a union.
+    kind: CompKind,
+
+    /// The members of this struct or union.
+    fields: CompFields,
+
+    /// The abstract template parameters of this class. Note that these are NOT
+    /// concrete template arguments, and should always be a
+    /// `Type(TypeKind::TypeParam(name))`. For concrete template arguments, see
+    /// `TypeKind::TemplateInstantiation`.
+    template_params: Vec<TypeId>,
+
+    /// The method declarations inside this class, if in C++ mode.
+    methods: Vec<Method>,
+
+    /// The different constructors this struct or class contains.
+    constructors: Vec<FunctionId>,
+
+    /// The destructor of this type. The bool represents whether this destructor
+    /// is virtual.
+    destructor: Option<(MethodKind, FunctionId)>,
+
+    /// Vector of classes this one inherits from.
+    base_members: Vec<Base>,
+
+    /// The inner types that were declared inside this class, in something like:
+    ///
+    /// class Foo {
+    ///     typedef int FooTy;
+    ///     struct Bar {
+    ///         int baz;
+    ///     };
+    /// }
+    ///
+    /// static Foo::Bar const = {3};
+    inner_types: Vec<TypeId>,
+
+    /// Set of static constants declared inside this class.
+    inner_vars: Vec<VarId>,
+
+    /// Whether this type should generate an vtable (TODO: Should be able to
+    /// look at the virtual methods and ditch this field).
+    has_own_virtual_method: bool,
+
+    /// Whether this type has destructor.
+    has_destructor: bool,
+
+    /// Whether this type has a base type with more than one member.
+    ///
+    /// TODO: We should be able to compute this.
+    has_nonempty_base: bool,
+
+    /// If this type has a template parameter which is not a type (e.g.: a
+    /// size_t)
+    has_non_type_template_params: bool,
+
+    /// Whether this type has a bit field member whose width couldn't be
+    /// evaluated (e.g. if it depends on a template parameter). We generate an
+    /// opaque type in this case.
+    has_unevaluable_bit_field_width: bool,
+
+    /// Whether we saw `__attribute__((packed))` on or within this type.
+    packed_attr: bool,
+
+    /// Used to know if we've found an opaque attribute that could cause us to
+    /// generate a type with invalid layout. This is explicitly used to avoid us
+    /// generating bad alignments when parsing types like max_align_t.
+    ///
+    /// It's not clear what the behavior should be here, if generating the item
+    /// and pray, or behave as an opaque type.
+    found_unknown_attr: bool,
+
+    /// Used to indicate when a struct has been forward declared. Usually used
+    /// in headers so that APIs can't modify them directly.
+    is_forward_declaration: bool,
+}
+
+impl CompInfo {
+    /// Construct a new compound type.
+    pub(crate) fn new(kind: CompKind) -> Self {
+        CompInfo {
+            kind,
+            fields: CompFields::default(),
+            template_params: vec![],
+            methods: vec![],
+            constructors: vec![],
+            destructor: None,
+            base_members: vec![],
+            inner_types: vec![],
+            inner_vars: vec![],
+            has_own_virtual_method: false,
+            has_destructor: false,
+            has_nonempty_base: false,
+            has_non_type_template_params: false,
+            has_unevaluable_bit_field_width: false,
+            packed_attr: false,
+            found_unknown_attr: false,
+            is_forward_declaration: false,
+        }
+    }
+
+    /// Compute the layout of this type.
+    ///
+    /// This is called as a fallback under some circumstances where LLVM doesn't
+    /// give us the correct layout.
+    ///
+    /// If we're a union without known layout, we try to compute it from our
+    /// members. This is not ideal, but clang fails to report the size for these
+    /// kind of unions, see test/headers/template_union.hpp
+    pub(crate) fn layout(&self, ctx: &BindgenContext) -> Option<Layout> {
+        // We can't do better than clang here, sorry.
+        if self.kind == CompKind::Struct {
+            return None;
+        }
+
+        // By definition, we don't have the right layout information here if
+        // we're a forward declaration.
+        if self.is_forward_declaration() {
+            return None;
+        }
+
+        // empty union case
+        if !self.has_fields() {
+            return None;
+        }
+
+        let mut max_size = 0;
+        // Don't allow align(0)
+        let mut max_align = 1;
+        self.each_known_field_layout(ctx, |layout| {
+            max_size = cmp::max(max_size, layout.size);
+            max_align = cmp::max(max_align, layout.align);
+        });
+
+        Some(Layout::new(max_size, max_align))
+    }
+
+    /// Get this type's set of fields.
+    pub(crate) fn fields(&self) -> &[Field] {
+        match self.fields {
+            CompFields::Error => &[],
+            CompFields::After { ref fields, .. } => fields,
+            CompFields::Before(..) => {
+                panic!("Should always have computed bitfield units first");
+            }
+        }
+    }
+
+    fn has_fields(&self) -> bool {
+        match self.fields {
+            CompFields::Error => false,
+            CompFields::After { ref fields, .. } => !fields.is_empty(),
+            CompFields::Before(ref raw_fields) => !raw_fields.is_empty(),
+        }
+    }
+
+    fn each_known_field_layout(
+        &self,
+        ctx: &BindgenContext,
+        mut callback: impl FnMut(Layout),
+    ) {
+        match self.fields {
+            CompFields::Error => {}
+            CompFields::After { ref fields, .. } => {
+                for field in fields.iter() {
+                    if let Some(layout) = field.layout(ctx) {
+                        callback(layout);
+                    }
+                }
+            }
+            CompFields::Before(ref raw_fields) => {
+                for field in raw_fields.iter() {
+                    let field_ty = ctx.resolve_type(field.0.ty);
+                    if let Some(layout) = field_ty.layout(ctx) {
+                        callback(layout);
+                    }
+                }
+            }
+        }
+    }
+
+    fn has_bitfields(&self) -> bool {
+        match self.fields {
+            CompFields::Error => false,
+            CompFields::After {
+                has_bitfield_units, ..
+            } => has_bitfield_units,
+            CompFields::Before(_) => {
+                panic!("Should always have computed bitfield units first");
+            }
+        }
+    }
+
+    /// Returns whether we have a too large bitfield unit, in which case we may
+    /// not be able to derive some of the things we should be able to normally
+    /// derive.
+    pub(crate) fn has_too_large_bitfield_unit(&self) -> bool {
+        if !self.has_bitfields() {
+            return false;
+        }
+        self.fields().iter().any(|field| match *field {
+            Field::DataMember(..) => false,
+            Field::Bitfields(ref unit) => {
+                unit.layout.size > RUST_DERIVE_IN_ARRAY_LIMIT
+            }
+        })
+    }
+
+    /// Does this type have any template parameters that aren't types
+    /// (e.g. int)?
+    pub(crate) fn has_non_type_template_params(&self) -> bool {
+        self.has_non_type_template_params
+    }
+
+    /// Do we see a virtual function during parsing?
+    /// Get the has_own_virtual_method boolean.
+    pub(crate) fn has_own_virtual_method(&self) -> bool {
+        self.has_own_virtual_method
+    }
+
+    /// Did we see a destructor when parsing this type?
+    pub(crate) fn has_own_destructor(&self) -> bool {
+        self.has_destructor
+    }
+
+    /// Get this type's set of methods.
+    pub(crate) fn methods(&self) -> &[Method] {
+        &self.methods
+    }
+
+    /// Get this type's set of constructors.
+    pub(crate) fn constructors(&self) -> &[FunctionId] {
+        &self.constructors
+    }
+
+    /// Get this type's destructor.
+    pub(crate) fn destructor(&self) -> Option<(MethodKind, FunctionId)> {
+        self.destructor
+    }
+
+    /// What kind of compound type is this?
+    pub(crate) fn kind(&self) -> CompKind {
+        self.kind
+    }
+
+    /// Is this a union?
+    pub(crate) fn is_union(&self) -> bool {
+        self.kind() == CompKind::Union
+    }
+
+    /// The set of types that this one inherits from.
+    pub(crate) fn base_members(&self) -> &[Base] {
+        &self.base_members
+    }
+
+    /// Construct a new compound type from a Clang type.
+    pub(crate) fn from_ty(
+        potential_id: ItemId,
+        ty: &clang::Type,
+        location: Option<clang::Cursor>,
+        ctx: &mut BindgenContext,
+    ) -> Result<Self, ParseError> {
+        use clang_sys::*;
+        assert!(
+            ty.template_args().is_none(),
+            "We handle template instantiations elsewhere"
+        );
+
+        let mut cursor = ty.declaration();
+        let mut kind = Self::kind_from_cursor(&cursor);
+        if kind.is_err() {
+            if let Some(location) = location {
+                kind = Self::kind_from_cursor(&location);
+                cursor = location;
+            }
+        }
+
+        let kind = kind?;
+
+        debug!("CompInfo::from_ty({:?}, {:?})", kind, cursor);
+
+        let mut ci = CompInfo::new(kind);
+        ci.is_forward_declaration =
+            location.map_or(true, |cur| match cur.kind() {
+                CXCursor_ParmDecl => true,
+                CXCursor_StructDecl | CXCursor_UnionDecl |
+                CXCursor_ClassDecl => !cur.is_definition(),
+                _ => false,
+            });
+
+        let mut maybe_anonymous_struct_field = None;
+        cursor.visit(|cur| {
+            if cur.kind() != CXCursor_FieldDecl {
+                if let Some((ty, clang_ty, public, offset)) =
+                    maybe_anonymous_struct_field.take()
+                {
+                    if cur.kind() == CXCursor_TypedefDecl &&
+                        cur.typedef_type().unwrap().canonical_type() ==
+                            clang_ty
+                    {
+                        // Typedefs of anonymous structs appear later in the ast
+                        // than the struct itself, that would otherwise be an
+                        // anonymous field. Detect that case here, and do
+                        // nothing.
+                    } else {
+                        let field = RawField::new(
+                            None, ty, None, None, None, public, offset,
+                        );
+                        ci.fields.append_raw_field(field);
+                    }
+                }
+            }
+
+            match cur.kind() {
+                CXCursor_FieldDecl => {
+                    if let Some((ty, clang_ty, public, offset)) =
+                        maybe_anonymous_struct_field.take()
+                    {
+                        let mut used = false;
+                        cur.visit(|child| {
+                            if child.cur_type() == clang_ty {
+                                used = true;
+                            }
+                            CXChildVisit_Continue
+                        });
+
+                        if !used {
+                            let field = RawField::new(
+                                None, ty, None, None, None, public, offset,
+                            );
+                            ci.fields.append_raw_field(field);
+                        }
+                    }
+
+                    let bit_width = if cur.is_bit_field() {
+                        let width = cur.bit_width();
+
+                        // Make opaque type if the bit width couldn't be
+                        // evaluated.
+                        if width.is_none() {
+                            ci.has_unevaluable_bit_field_width = true;
+                            return CXChildVisit_Break;
+                        }
+
+                        width
+                    } else {
+                        None
+                    };
+
+                    let field_type = Item::from_ty_or_ref(
+                        cur.cur_type(),
+                        cur,
+                        Some(potential_id),
+                        ctx,
+                    );
+
+                    let comment = cur.raw_comment();
+                    let annotations = Annotations::new(&cur);
+                    let name = cur.spelling();
+                    let is_public = cur.public_accessible();
+                    let offset = cur.offset_of_field().ok();
+
+                    // Name can be empty if there are bitfields, for example,
+                    // see tests/headers/struct_with_bitfields.h
+                    assert!(
+                        !name.is_empty() || bit_width.is_some(),
+                        "Empty field name?"
+                    );
+
+                    let name = if name.is_empty() { None } else { Some(name) };
+
+                    let field = RawField::new(
+                        name,
+                        field_type,
+                        comment,
+                        annotations,
+                        bit_width,
+                        is_public,
+                        offset,
+                    );
+                    ci.fields.append_raw_field(field);
+
+                    // No we look for things like attributes and stuff.
+                    cur.visit(|cur| {
+                        if cur.kind() == CXCursor_UnexposedAttr {
+                            ci.found_unknown_attr = true;
+                        }
+                        CXChildVisit_Continue
+                    });
+                }
+                CXCursor_UnexposedAttr => {
+                    ci.found_unknown_attr = true;
+                }
+                CXCursor_EnumDecl |
+                CXCursor_TypeAliasDecl |
+                CXCursor_TypeAliasTemplateDecl |
+                CXCursor_TypedefDecl |
+                CXCursor_StructDecl |
+                CXCursor_UnionDecl |
+                CXCursor_ClassTemplate |
+                CXCursor_ClassDecl => {
+                    // We can find non-semantic children here, clang uses a
+                    // StructDecl to note incomplete structs that haven't been
+                    // forward-declared before, see [1].
+                    //
+                    // Also, clang seems to scope struct definitions inside
+                    // unions, and other named struct definitions inside other
+                    // structs to the whole translation unit.
+                    //
+                    // Let's just assume that if the cursor we've found is a
+                    // definition, it's a valid inner type.
+                    //
+                    // [1]: https://github.com/rust-lang/rust-bindgen/issues/482
+                    let is_inner_struct =
+                        cur.semantic_parent() == cursor || cur.is_definition();
+                    if !is_inner_struct {
+                        return CXChildVisit_Continue;
+                    }
+
+                    // Even if this is a definition, we may not be the semantic
+                    // parent, see #1281.
+                    let inner = Item::parse(cur, Some(potential_id), ctx)
+                        .expect("Inner ClassDecl");
+
+                    // If we avoided recursion parsing this type (in
+                    // `Item::from_ty_with_id()`), then this might not be a
+                    // valid type ID, so check and gracefully handle this.
+                    if ctx.resolve_item_fallible(inner).is_some() {
+                        let inner = inner.expect_type_id(ctx);
+
+                        ci.inner_types.push(inner);
+
+                        // A declaration of an union or a struct without name
+                        // could also be an unnamed field, unfortunately.
+                        if cur.is_anonymous() && cur.kind() != CXCursor_EnumDecl
+                        {
+                            let ty = cur.cur_type();
+                            let public = cur.public_accessible();
+                            let offset = cur.offset_of_field().ok();
+
+                            maybe_anonymous_struct_field =
+                                Some((inner, ty, public, offset));
+                        }
+                    }
+                }
+                CXCursor_PackedAttr => {
+                    ci.packed_attr = true;
+                }
+                CXCursor_TemplateTypeParameter => {
+                    let param = Item::type_param(None, cur, ctx).expect(
+                        "Item::type_param should't fail when pointing \
+                         at a TemplateTypeParameter",
+                    );
+                    ci.template_params.push(param);
+                }
+                CXCursor_CXXBaseSpecifier => {
+                    let is_virtual_base = cur.is_virtual_base();
+                    ci.has_own_virtual_method |= is_virtual_base;
+
+                    let kind = if is_virtual_base {
+                        BaseKind::Virtual
+                    } else {
+                        BaseKind::Normal
+                    };
+
+                    let field_name = match ci.base_members.len() {
+                        0 => "_base".into(),
+                        n => format!("_base_{}", n),
+                    };
+                    let type_id =
+                        Item::from_ty_or_ref(cur.cur_type(), cur, None, ctx);
+                    ci.base_members.push(Base {
+                        ty: type_id,
+                        kind,
+                        field_name,
+                        is_pub: cur.access_specifier() ==
+                            clang_sys::CX_CXXPublic,
+                    });
+                }
+                CXCursor_Constructor | CXCursor_Destructor |
+                CXCursor_CXXMethod => {
+                    let is_virtual = cur.method_is_virtual();
+                    let is_static = cur.method_is_static();
+                    debug_assert!(!(is_static && is_virtual), "How?");
+
+                    ci.has_destructor |= cur.kind() == CXCursor_Destructor;
+                    ci.has_own_virtual_method |= is_virtual;
+
+                    // This used to not be here, but then I tried generating
+                    // stylo bindings with this (without path filters), and
+                    // cried a lot with a method in gfx/Point.h
+                    // (ToUnknownPoint), that somehow was causing the same type
+                    // to be inserted in the map two times.
+                    //
+                    // I couldn't make a reduced test case, but anyway...
+                    // Methods of template functions not only used to be inlined,
+                    // but also instantiated, and we wouldn't be able to call
+                    // them, so just bail out.
+                    if !ci.template_params.is_empty() {
+                        return CXChildVisit_Continue;
+                    }
+
+                    // NB: This gets us an owned `Function`, not a
+                    // `FunctionSig`.
+                    let signature =
+                        match Item::parse(cur, Some(potential_id), ctx) {
+                            Ok(item)
+                                if ctx
+                                    .resolve_item(item)
+                                    .kind()
+                                    .is_function() =>
+                            {
+                                item
+                            }
+                            _ => return CXChildVisit_Continue,
+                        };
+
+                    let signature = signature.expect_function_id(ctx);
+
+                    match cur.kind() {
+                        CXCursor_Constructor => {
+                            ci.constructors.push(signature);
+                        }
+                        CXCursor_Destructor => {
+                            let kind = if is_virtual {
+                                MethodKind::VirtualDestructor {
+                                    pure_virtual: cur.method_is_pure_virtual(),
+                                }
+                            } else {
+                                MethodKind::Destructor
+                            };
+                            ci.destructor = Some((kind, signature));
+                        }
+                        CXCursor_CXXMethod => {
+                            let is_const = cur.method_is_const();
+                            let method_kind = if is_static {
+                                MethodKind::Static
+                            } else if is_virtual {
+                                MethodKind::Virtual {
+                                    pure_virtual: cur.method_is_pure_virtual(),
+                                }
+                            } else {
+                                MethodKind::Normal
+                            };
+
+                            let method =
+                                Method::new(method_kind, signature, is_const);
+
+                            ci.methods.push(method);
+                        }
+                        _ => unreachable!("How can we see this here?"),
+                    }
+                }
+                CXCursor_NonTypeTemplateParameter => {
+                    ci.has_non_type_template_params = true;
+                }
+                CXCursor_VarDecl => {
+                    let linkage = cur.linkage();
+                    if linkage != CXLinkage_External &&
+                        linkage != CXLinkage_UniqueExternal
+                    {
+                        return CXChildVisit_Continue;
+                    }
+
+                    let visibility = cur.visibility();
+                    if visibility != CXVisibility_Default {
+                        return CXChildVisit_Continue;
+                    }
+
+                    if let Ok(item) = Item::parse(cur, Some(potential_id), ctx)
+                    {
+                        ci.inner_vars.push(item.as_var_id_unchecked());
+                    }
+                }
+                // Intentionally not handled
+                CXCursor_CXXAccessSpecifier |
+                CXCursor_CXXFinalAttr |
+                CXCursor_FunctionTemplate |
+                CXCursor_ConversionFunction => {}
+                _ => {
+                    warn!(
+                        "unhandled comp member `{}` (kind {:?}) in `{}` ({})",
+                        cur.spelling(),
+                        clang::kind_to_str(cur.kind()),
+                        cursor.spelling(),
+                        cur.location()
+                    );
+                }
+            }
+            CXChildVisit_Continue
+        });
+
+        if let Some((ty, _, public, offset)) = maybe_anonymous_struct_field {
+            let field =
+                RawField::new(None, ty, None, None, None, public, offset);
+            ci.fields.append_raw_field(field);
+        }
+
+        Ok(ci)
+    }
+
+    fn kind_from_cursor(
+        cursor: &clang::Cursor,
+    ) -> Result<CompKind, ParseError> {
+        use clang_sys::*;
+        Ok(match cursor.kind() {
+            CXCursor_UnionDecl => CompKind::Union,
+            CXCursor_ClassDecl | CXCursor_StructDecl => CompKind::Struct,
+            CXCursor_CXXBaseSpecifier |
+            CXCursor_ClassTemplatePartialSpecialization |
+            CXCursor_ClassTemplate => match cursor.template_kind() {
+                CXCursor_UnionDecl => CompKind::Union,
+                _ => CompKind::Struct,
+            },
+            _ => {
+                warn!("Unknown kind for comp type: {:?}", cursor);
+                return Err(ParseError::Continue);
+            }
+        })
+    }
+
+    /// Get the set of types that were declared within this compound type
+    /// (e.g. nested class definitions).
+    pub(crate) fn inner_types(&self) -> &[TypeId] {
+        &self.inner_types
+    }
+
+    /// Get the set of static variables declared within this compound type.
+    pub(crate) fn inner_vars(&self) -> &[VarId] {
+        &self.inner_vars
+    }
+
+    /// Have we found a field with an opaque type that could potentially mess up
+    /// the layout of this compound type?
+    pub(crate) fn found_unknown_attr(&self) -> bool {
+        self.found_unknown_attr
+    }
+
+    /// Is this compound type packed?
+    pub(crate) fn is_packed(
+        &self,
+        ctx: &BindgenContext,
+        layout: Option<&Layout>,
+    ) -> bool {
+        if self.packed_attr {
+            return true;
+        }
+
+        // Even though `libclang` doesn't expose `#pragma packed(...)`, we can
+        // detect it through its effects.
+        if let Some(parent_layout) = layout {
+            let mut packed = false;
+            self.each_known_field_layout(ctx, |layout| {
+                packed = packed || layout.align > parent_layout.align;
+            });
+            if packed {
+                info!("Found a struct that was defined within `#pragma packed(...)`");
+                return true;
+            }
+
+            if self.has_own_virtual_method && parent_layout.align == 1 {
+                return true;
+            }
+        }
+
+        false
+    }
+
+    /// Return true if a compound type is "naturally packed". This means we can exclude the
+    /// "packed" attribute without changing the layout.
+    /// This is useful for types that need an "align(N)" attribute since rustc won't compile
+    /// structs that have both of those attributes.
+    pub(crate) fn already_packed(&self, ctx: &BindgenContext) -> Option<bool> {
+        let mut total_size: usize = 0;
+
+        for field in self.fields().iter() {
+            let layout = field.layout(ctx)?;
+
+            if layout.align != 0 && total_size % layout.align != 0 {
+                return Some(false);
+            }
+
+            total_size += layout.size;
+        }
+
+        Some(true)
+    }
+
+    /// Returns true if compound type has been forward declared
+    pub(crate) fn is_forward_declaration(&self) -> bool {
+        self.is_forward_declaration
+    }
+
+    /// Compute this compound structure's bitfield allocation units.
+    pub(crate) fn compute_bitfield_units(
+        &mut self,
+        ctx: &BindgenContext,
+        layout: Option<&Layout>,
+    ) {
+        let packed = self.is_packed(ctx, layout);
+        self.fields.compute_bitfield_units(ctx, packed)
+    }
+
+    /// Assign for each anonymous field a generated name.
+    pub(crate) fn deanonymize_fields(&mut self, ctx: &BindgenContext) {
+        self.fields.deanonymize_fields(ctx, &self.methods);
+    }
+
+    /// Returns whether the current union can be represented as a Rust `union`
+    ///
+    /// Requirements:
+    ///     1. Current RustTarget allows for `untagged_union`
+    ///     2. Each field can derive `Copy` or we use ManuallyDrop.
+    ///     3. It's not zero-sized.
+    ///
+    /// Second boolean returns whether all fields can be copied (and thus
+    /// ManuallyDrop is not needed).
+    pub(crate) fn is_rust_union(
+        &self,
+        ctx: &BindgenContext,
+        layout: Option<&Layout>,
+        name: &str,
+    ) -> (bool, bool) {
+        if !self.is_union() {
+            return (false, false);
+        }
+
+        if !ctx.options().untagged_union {
+            return (false, false);
+        }
+
+        if self.is_forward_declaration() {
+            return (false, false);
+        }
+
+        let union_style = if ctx.options().bindgen_wrapper_union.matches(name) {
+            NonCopyUnionStyle::BindgenWrapper
+        } else if ctx.options().manually_drop_union.matches(name) {
+            NonCopyUnionStyle::ManuallyDrop
+        } else {
+            ctx.options().default_non_copy_union_style
+        };
+
+        let all_can_copy = self.fields().iter().all(|f| match *f {
+            Field::DataMember(ref field_data) => {
+                field_data.ty().can_derive_copy(ctx)
+            }
+            Field::Bitfields(_) => true,
+        });
+
+        if !all_can_copy && union_style == NonCopyUnionStyle::BindgenWrapper {
+            return (false, false);
+        }
+
+        if layout.map_or(false, |l| l.size == 0) {
+            return (false, false);
+        }
+
+        (true, all_can_copy)
+    }
+}
+
+impl DotAttributes for CompInfo {
+    fn dot_attributes<W>(
+        &self,
+        ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        writeln!(out, "<tr><td>CompKind</td><td>{:?}</td></tr>", self.kind)?;
+
+        if self.has_own_virtual_method {
+            writeln!(out, "<tr><td>has_vtable</td><td>true</td></tr>")?;
+        }
+
+        if self.has_destructor {
+            writeln!(out, "<tr><td>has_destructor</td><td>true</td></tr>")?;
+        }
+
+        if self.has_nonempty_base {
+            writeln!(out, "<tr><td>has_nonempty_base</td><td>true</td></tr>")?;
+        }
+
+        if self.has_non_type_template_params {
+            writeln!(
+                out,
+                "<tr><td>has_non_type_template_params</td><td>true</td></tr>"
+            )?;
+        }
+
+        if self.packed_attr {
+            writeln!(out, "<tr><td>packed_attr</td><td>true</td></tr>")?;
+        }
+
+        if self.is_forward_declaration {
+            writeln!(
+                out,
+                "<tr><td>is_forward_declaration</td><td>true</td></tr>"
+            )?;
+        }
+
+        if !self.fields().is_empty() {
+            writeln!(out, r#"<tr><td>fields</td><td><table border="0">"#)?;
+            for field in self.fields() {
+                field.dot_attributes(ctx, out)?;
+            }
+            writeln!(out, "</table></td></tr>")?;
+        }
+
+        Ok(())
+    }
+}
+
+impl IsOpaque for CompInfo {
+    type Extra = Option<Layout>;
+
+    fn is_opaque(&self, ctx: &BindgenContext, layout: &Option<Layout>) -> bool {
+        if self.has_non_type_template_params ||
+            self.has_unevaluable_bit_field_width
+        {
+            return true;
+        }
+
+        // When we do not have the layout for a bitfield's type (for example, it
+        // is a type parameter), then we can't compute bitfield units. We are
+        // left with no choice but to make the whole struct opaque, or else we
+        // might generate structs with incorrect sizes and alignments.
+        if let CompFields::Error = self.fields {
+            return true;
+        }
+
+        // Bitfields with a width that is larger than their unit's width have
+        // some strange things going on, and the best we can do is make the
+        // whole struct opaque.
+        if self.fields().iter().any(|f| match *f {
+            Field::DataMember(_) => false,
+            Field::Bitfields(ref unit) => unit.bitfields().iter().any(|bf| {
+                let bitfield_layout = ctx
+                    .resolve_type(bf.ty())
+                    .layout(ctx)
+                    .expect("Bitfield without layout? Gah!");
+                bf.width() / 8 > bitfield_layout.size as u32
+            }),
+        }) {
+            return true;
+        }
+
+        if !ctx.options().rust_features().repr_packed_n {
+            // If we don't have `#[repr(packed(N)]`, the best we can
+            // do is make this struct opaque.
+            //
+            // See https://github.com/rust-lang/rust-bindgen/issues/537 and
+            // https://github.com/rust-lang/rust/issues/33158
+            if self.is_packed(ctx, layout.as_ref()) &&
+                layout.map_or(false, |l| l.align > 1)
+            {
+                warn!("Found a type that is both packed and aligned to greater than \
+                       1; Rust before version 1.33 doesn't have `#[repr(packed(N))]`, so we \
+                       are treating it as opaque. You may wish to set bindgen's rust target \
+                       version to 1.33 or later to enable `#[repr(packed(N))]` support.");
+                return true;
+            }
+        }
+
+        false
+    }
+}
+
+impl TemplateParameters for CompInfo {
+    fn self_template_params(&self, _ctx: &BindgenContext) -> Vec<TypeId> {
+        self.template_params.clone()
+    }
+}
+
+impl Trace for CompInfo {
+    type Extra = Item;
+
+    fn trace<T>(&self, context: &BindgenContext, tracer: &mut T, item: &Item)
+    where
+        T: Tracer,
+    {
+        for p in item.all_template_params(context) {
+            tracer.visit_kind(p.into(), EdgeKind::TemplateParameterDefinition);
+        }
+
+        for ty in self.inner_types() {
+            tracer.visit_kind(ty.into(), EdgeKind::InnerType);
+        }
+
+        for &var in self.inner_vars() {
+            tracer.visit_kind(var.into(), EdgeKind::InnerVar);
+        }
+
+        for method in self.methods() {
+            tracer.visit_kind(method.signature.into(), EdgeKind::Method);
+        }
+
+        if let Some((_kind, signature)) = self.destructor() {
+            tracer.visit_kind(signature.into(), EdgeKind::Destructor);
+        }
+
+        for ctor in self.constructors() {
+            tracer.visit_kind(ctor.into(), EdgeKind::Constructor);
+        }
+
+        // Base members and fields are not generated for opaque types (but all
+        // of the above things are) so stop here.
+        if item.is_opaque(context, &()) {
+            return;
+        }
+
+        for base in self.base_members() {
+            tracer.visit_kind(base.ty.into(), EdgeKind::BaseMember);
+        }
+
+        self.fields.trace(context, tracer, &());
+    }
+}
diff --git a/third_party/rust/bindgen/ir/context.rs b/third_party/rust/bindgen/ir/context.rs
new file mode 100644
index 0000000000..517d3365b6
--- /dev/null
+++ b/third_party/rust/bindgen/ir/context.rs
@@ -0,0 +1,3038 @@
+//! Common context that is passed around during parsing and codegen.
+
+use super::super::time::Timer;
+use super::analysis::{
+    analyze, as_cannot_derive_set, CannotDerive, DeriveTrait,
+    HasDestructorAnalysis, HasFloat, HasTypeParameterInArray,
+    HasVtableAnalysis, HasVtableResult, SizednessAnalysis, SizednessResult,
+    UsedTemplateParameters,
+};
+use super::derive::{
+    CanDerive, CanDeriveCopy, CanDeriveDebug, CanDeriveDefault, CanDeriveEq,
+    CanDeriveHash, CanDeriveOrd, CanDerivePartialEq, CanDerivePartialOrd,
+};
+use super::function::Function;
+use super::int::IntKind;
+use super::item::{IsOpaque, Item, ItemAncestors, ItemSet};
+use super::item_kind::ItemKind;
+use super::module::{Module, ModuleKind};
+use super::template::{TemplateInstantiation, TemplateParameters};
+use super::traversal::{self, Edge, ItemTraversal};
+use super::ty::{FloatKind, Type, TypeKind};
+use crate::clang::{self, ABIKind, Cursor};
+use crate::codegen::CodegenError;
+use crate::BindgenOptions;
+use crate::{Entry, HashMap, HashSet};
+
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::ToTokens;
+use std::borrow::Cow;
+use std::cell::{Cell, RefCell};
+use std::collections::{BTreeSet, HashMap as StdHashMap};
+use std::iter::IntoIterator;
+use std::mem;
+
+/// An identifier for some kind of IR item.
+#[derive(Debug, Copy, Clone, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct ItemId(usize);
+
+/// Declare a newtype around `ItemId` with convesion methods.
+macro_rules! item_id_newtype {
+    (
+        $( #[$attr:meta] )*
+        pub(crate) struct $name:ident(ItemId)
+        where
+            $( #[$checked_attr:meta] )*
+            checked = $checked:ident with $check_method:ident,
+            $( #[$expected_attr:meta] )*
+            expected = $expected:ident,
+            $( #[$unchecked_attr:meta] )*
+            unchecked = $unchecked:ident;
+    ) => {
+        $( #[$attr] )*
+        #[derive(Debug, Copy, Clone, Eq, PartialOrd, Ord, Hash)]
+        pub(crate) struct $name(ItemId);
+
+        impl $name {
+            /// Create an `ItemResolver` from this ID.
+            #[allow(dead_code)]
+            pub(crate) fn into_resolver(self) -> ItemResolver {
+                let id: ItemId = self.into();
+                id.into()
+            }
+        }
+
+        impl<T> ::std::cmp::PartialEq<T> for $name
+        where
+            T: Copy + Into<ItemId>
+        {
+            fn eq(&self, rhs: &T) -> bool {
+                let rhs: ItemId = (*rhs).into();
+                self.0 == rhs
+            }
+        }
+
+        impl From<$name> for ItemId {
+            fn from(id: $name) -> ItemId {
+                id.0
+            }
+        }
+
+        impl<'a> From<&'a $name> for ItemId {
+            fn from(id: &'a $name) -> ItemId {
+                id.0
+            }
+        }
+
+        #[allow(dead_code)]
+        impl ItemId {
+            $( #[$checked_attr] )*
+            pub(crate) fn $checked(&self, ctx: &BindgenContext) -> Option<$name> {
+                if ctx.resolve_item(*self).kind().$check_method() {
+                    Some($name(*self))
+                } else {
+                    None
+                }
+            }
+
+            $( #[$expected_attr] )*
+            pub(crate) fn $expected(&self, ctx: &BindgenContext) -> $name {
+                self.$checked(ctx)
+                    .expect(concat!(
+                        stringify!($expected),
+                        " called with ItemId that points to the wrong ItemKind"
+                    ))
+            }
+
+            $( #[$unchecked_attr] )*
+            pub(crate) fn $unchecked(&self) -> $name {
+                $name(*self)
+            }
+        }
+    }
+}
+
+item_id_newtype! {
+    /// An identifier for an `Item` whose `ItemKind` is known to be
+    /// `ItemKind::Type`.
+    pub(crate) struct TypeId(ItemId)
+    where
+        /// Convert this `ItemId` into a `TypeId` if its associated item is a type,
+        /// otherwise return `None`.
+        checked = as_type_id with is_type,
+
+        /// Convert this `ItemId` into a `TypeId`.
+        ///
+        /// If this `ItemId` does not point to a type, then panic.
+        expected = expect_type_id,
+
+        /// Convert this `ItemId` into a `TypeId` without actually checking whether
+        /// this ID actually points to a `Type`.
+        unchecked = as_type_id_unchecked;
+}
+
+item_id_newtype! {
+    /// An identifier for an `Item` whose `ItemKind` is known to be
+    /// `ItemKind::Module`.
+    pub(crate) struct ModuleId(ItemId)
+    where
+        /// Convert this `ItemId` into a `ModuleId` if its associated item is a
+        /// module, otherwise return `None`.
+        checked = as_module_id with is_module,
+
+        /// Convert this `ItemId` into a `ModuleId`.
+        ///
+        /// If this `ItemId` does not point to a module, then panic.
+        expected = expect_module_id,
+
+        /// Convert this `ItemId` into a `ModuleId` without actually checking
+        /// whether this ID actually points to a `Module`.
+        unchecked = as_module_id_unchecked;
+}
+
+item_id_newtype! {
+    /// An identifier for an `Item` whose `ItemKind` is known to be
+    /// `ItemKind::Var`.
+    pub(crate) struct VarId(ItemId)
+    where
+        /// Convert this `ItemId` into a `VarId` if its associated item is a var,
+        /// otherwise return `None`.
+        checked = as_var_id with is_var,
+
+        /// Convert this `ItemId` into a `VarId`.
+        ///
+        /// If this `ItemId` does not point to a var, then panic.
+        expected = expect_var_id,
+
+        /// Convert this `ItemId` into a `VarId` without actually checking whether
+        /// this ID actually points to a `Var`.
+        unchecked = as_var_id_unchecked;
+}
+
+item_id_newtype! {
+    /// An identifier for an `Item` whose `ItemKind` is known to be
+    /// `ItemKind::Function`.
+    pub(crate) struct FunctionId(ItemId)
+    where
+        /// Convert this `ItemId` into a `FunctionId` if its associated item is a function,
+        /// otherwise return `None`.
+        checked = as_function_id with is_function,
+
+        /// Convert this `ItemId` into a `FunctionId`.
+        ///
+        /// If this `ItemId` does not point to a function, then panic.
+        expected = expect_function_id,
+
+        /// Convert this `ItemId` into a `FunctionId` without actually checking whether
+        /// this ID actually points to a `Function`.
+        unchecked = as_function_id_unchecked;
+}
+
+impl From<ItemId> for usize {
+    fn from(id: ItemId) -> usize {
+        id.0
+    }
+}
+
+impl ItemId {
+    /// Get a numeric representation of this ID.
+    pub(crate) fn as_usize(&self) -> usize {
+        (*self).into()
+    }
+}
+
+impl<T> ::std::cmp::PartialEq<T> for ItemId
+where
+    T: Copy + Into<ItemId>,
+{
+    fn eq(&self, rhs: &T) -> bool {
+        let rhs: ItemId = (*rhs).into();
+        self.0 == rhs.0
+    }
+}
+
+impl<T> CanDeriveDebug for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_debug(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_debug && ctx.lookup_can_derive_debug(*self)
+    }
+}
+
+impl<T> CanDeriveDefault for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_default(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_default && ctx.lookup_can_derive_default(*self)
+    }
+}
+
+impl<T> CanDeriveCopy for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_copy(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_copy && ctx.lookup_can_derive_copy(*self)
+    }
+}
+
+impl<T> CanDeriveHash for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_hash(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_hash && ctx.lookup_can_derive_hash(*self)
+    }
+}
+
+impl<T> CanDerivePartialOrd for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_partialord(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_partialord &&
+            ctx.lookup_can_derive_partialeq_or_partialord(*self) ==
+                CanDerive::Yes
+    }
+}
+
+impl<T> CanDerivePartialEq for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_partialeq(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_partialeq &&
+            ctx.lookup_can_derive_partialeq_or_partialord(*self) ==
+                CanDerive::Yes
+    }
+}
+
+impl<T> CanDeriveEq for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_eq(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_eq &&
+            ctx.lookup_can_derive_partialeq_or_partialord(*self) ==
+                CanDerive::Yes &&
+            !ctx.lookup_has_float(*self)
+    }
+}
+
+impl<T> CanDeriveOrd for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn can_derive_ord(&self, ctx: &BindgenContext) -> bool {
+        ctx.options().derive_ord &&
+            ctx.lookup_can_derive_partialeq_or_partialord(*self) ==
+                CanDerive::Yes &&
+            !ctx.lookup_has_float(*self)
+    }
+}
+
+/// A key used to index a resolved type, so we only process it once.
+///
+/// This is almost always a USR string (an unique identifier generated by
+/// clang), but it can also be the canonical declaration if the type is unnamed,
+/// in which case clang may generate the same USR for multiple nested unnamed
+/// types.
+#[derive(Eq, PartialEq, Hash, Debug)]
+enum TypeKey {
+    Usr(String),
+    Declaration(Cursor),
+}
+
+/// A context used during parsing and generation of structs.
+#[derive(Debug)]
+pub(crate) struct BindgenContext {
+    /// The map of all the items parsed so far, keyed off ItemId.
+    items: Vec<Option<Item>>,
+
+    /// Clang USR to type map. This is needed to be able to associate types with
+    /// item ids during parsing.
+    types: HashMap<TypeKey, TypeId>,
+
+    /// Maps from a cursor to the item ID of the named template type parameter
+    /// for that cursor.
+    type_params: HashMap<clang::Cursor, TypeId>,
+
+    /// A cursor to module map. Similar reason than above.
+    modules: HashMap<Cursor, ModuleId>,
+
+    /// The root module, this is guaranteed to be an item of kind Module.
+    root_module: ModuleId,
+
+    /// Current module being traversed.
+    current_module: ModuleId,
+
+    /// A HashMap keyed on a type definition, and whose value is the parent ID
+    /// of the declaration.
+    ///
+    /// This is used to handle the cases where the semantic and the lexical
+    /// parents of the cursor differ, like when a nested class is defined
+    /// outside of the parent class.
+    semantic_parents: HashMap<clang::Cursor, ItemId>,
+
+    /// A stack with the current type declarations and types we're parsing. This
+    /// is needed to avoid infinite recursion when parsing a type like:
+    ///
+    /// struct c { struct c* next; };
+    ///
+    /// This means effectively, that a type has a potential ID before knowing if
+    /// it's a correct type. But that's not important in practice.
+    ///
+    /// We could also use the `types` HashMap, but my intention with it is that
+    /// only valid types and declarations end up there, and this could
+    /// potentially break that assumption.
+    currently_parsed_types: Vec<PartialType>,
+
+    /// A map with all the already parsed macro names. This is done to avoid
+    /// hard errors while parsing duplicated macros, as well to allow macro
+    /// expression parsing.
+    ///
+    /// This needs to be an std::HashMap because the cexpr API requires it.
+    parsed_macros: StdHashMap<Vec<u8>, cexpr::expr::EvalResult>,
+
+    /// A map with all include locations.
+    ///
+    /// This is needed so that items are created in the order they are defined in.
+    ///
+    /// The key is the included file, the value is a pair of the source file and
+    /// the position of the `#include` directive in the source file.
+    includes: StdHashMap<String, (String, usize)>,
+
+    /// A set of all the included filenames.
+    deps: BTreeSet<Box<str>>,
+
+    /// The active replacements collected from replaces="xxx" annotations.
+    replacements: HashMap<Vec<String>, ItemId>,
+
+    collected_typerefs: bool,
+
+    in_codegen: bool,
+
+    /// The translation unit for parsing.
+    translation_unit: clang::TranslationUnit,
+
+    /// Target information that can be useful for some stuff.
+    target_info: clang::TargetInfo,
+
+    /// The options given by the user via cli or other medium.
+    options: BindgenOptions,
+
+    /// Whether a bindgen complex was generated
+    generated_bindgen_complex: Cell<bool>,
+
+    /// Whether a bindgen float16 was generated
+    generated_bindgen_float16: Cell<bool>,
+
+    /// The set of `ItemId`s that are allowlisted. This the very first thing
+    /// computed after parsing our IR, and before running any of our analyses.
+    allowlisted: Option<ItemSet>,
+
+    /// Cache for calls to `ParseCallbacks::blocklisted_type_implements_trait`
+    blocklisted_types_implement_traits:
+        RefCell<HashMap<DeriveTrait, HashMap<ItemId, CanDerive>>>,
+
+    /// The set of `ItemId`s that are allowlisted for code generation _and_ that
+    /// we should generate accounting for the codegen options.
+    ///
+    /// It's computed right after computing the allowlisted items.
+    codegen_items: Option<ItemSet>,
+
+    /// Map from an item's ID to the set of template parameter items that it
+    /// uses. See `ir::named` for more details. Always `Some` during the codegen
+    /// phase.
+    used_template_parameters: Option<HashMap<ItemId, ItemSet>>,
+
+    /// The set of `TypeKind::Comp` items found during parsing that need their
+    /// bitfield allocation units computed. Drained in `compute_bitfield_units`.
+    need_bitfield_allocation: Vec<ItemId>,
+
+    /// The set of enums that are defined by a pair of `enum` and `typedef`,
+    /// which is legal in C (but not C++).
+    ///
+    /// ```c++
+    /// // in either order
+    /// enum Enum { Variants... };
+    /// typedef int16_t Enum;
+    /// ```
+    ///
+    /// The stored `ItemId` is that of the `TypeKind::Enum`, not of the
+    /// `TypeKind::Alias`.
+    ///
+    /// This is populated when we enter codegen by `compute_enum_typedef_combos`
+    /// and is always `None` before that and `Some` after.
+    enum_typedef_combos: Option<HashSet<ItemId>>,
+
+    /// The set of (`ItemId`s of) types that can't derive debug.
+    ///
+    /// This is populated when we enter codegen by `compute_cannot_derive_debug`
+    /// and is always `None` before that and `Some` after.
+    cannot_derive_debug: Option<HashSet<ItemId>>,
+
+    /// The set of (`ItemId`s of) types that can't derive default.
+    ///
+    /// This is populated when we enter codegen by `compute_cannot_derive_default`
+    /// and is always `None` before that and `Some` after.
+    cannot_derive_default: Option<HashSet<ItemId>>,
+
+    /// The set of (`ItemId`s of) types that can't derive copy.
+    ///
+    /// This is populated when we enter codegen by `compute_cannot_derive_copy`
+    /// and is always `None` before that and `Some` after.
+    cannot_derive_copy: Option<HashSet<ItemId>>,
+
+    /// The set of (`ItemId`s of) types that can't derive hash.
+    ///
+    /// This is populated when we enter codegen by `compute_can_derive_hash`
+    /// and is always `None` before that and `Some` after.
+    cannot_derive_hash: Option<HashSet<ItemId>>,
+
+    /// The map why specified `ItemId`s of) types that can't derive hash.
+    ///
+    /// This is populated when we enter codegen by
+    /// `compute_cannot_derive_partialord_partialeq_or_eq` and is always `None`
+    /// before that and `Some` after.
+    cannot_derive_partialeq_or_partialord: Option<HashMap<ItemId, CanDerive>>,
+
+    /// The sizedness of types.
+    ///
+    /// This is populated by `compute_sizedness` and is always `None` before
+    /// that function is invoked and `Some` afterwards.
+    sizedness: Option<HashMap<TypeId, SizednessResult>>,
+
+    /// The set of (`ItemId's of`) types that has vtable.
+    ///
+    /// Populated when we enter codegen by `compute_has_vtable`; always `None`
+    /// before that and `Some` after.
+    have_vtable: Option<HashMap<ItemId, HasVtableResult>>,
+
+    /// The set of (`ItemId's of`) types that has destructor.
+    ///
+    /// Populated when we enter codegen by `compute_has_destructor`; always `None`
+    /// before that and `Some` after.
+    have_destructor: Option<HashSet<ItemId>>,
+
+    /// The set of (`ItemId's of`) types that has array.
+    ///
+    /// Populated when we enter codegen by `compute_has_type_param_in_array`; always `None`
+    /// before that and `Some` after.
+    has_type_param_in_array: Option<HashSet<ItemId>>,
+
+    /// The set of (`ItemId's of`) types that has float.
+    ///
+    /// Populated when we enter codegen by `compute_has_float`; always `None`
+    /// before that and `Some` after.
+    has_float: Option<HashSet<ItemId>>,
+}
+
+/// A traversal of allowlisted items.
+struct AllowlistedItemsTraversal<'ctx> {
+    ctx: &'ctx BindgenContext,
+    traversal: ItemTraversal<'ctx, ItemSet, Vec<ItemId>>,
+}
+
+impl<'ctx> Iterator for AllowlistedItemsTraversal<'ctx> {
+    type Item = ItemId;
+
+    fn next(&mut self) -> Option<ItemId> {
+        loop {
+            let id = self.traversal.next()?;
+
+            if self.ctx.resolve_item(id).is_blocklisted(self.ctx) {
+                continue;
+            }
+
+            return Some(id);
+        }
+    }
+}
+
+impl<'ctx> AllowlistedItemsTraversal<'ctx> {
+    /// Construct a new allowlisted items traversal.
+    pub(crate) fn new<R>(
+        ctx: &'ctx BindgenContext,
+        roots: R,
+        predicate: for<'a> fn(&'a BindgenContext, Edge) -> bool,
+    ) -> Self
+    where
+        R: IntoIterator<Item = ItemId>,
+    {
+        AllowlistedItemsTraversal {
+            ctx,
+            traversal: ItemTraversal::new(ctx, roots, predicate),
+        }
+    }
+}
+
+impl BindgenContext {
+    /// Construct the context for the given `options`.
+    pub(crate) fn new(
+        options: BindgenOptions,
+        input_unsaved_files: &[clang::UnsavedFile],
+    ) -> Self {
+        // TODO(emilio): Use the CXTargetInfo here when available.
+        //
+        // see: https://reviews.llvm.org/D32389
+        let index = clang::Index::new(false, true);
+
+        let parse_options =
+            clang_sys::CXTranslationUnit_DetailedPreprocessingRecord;
+
+        let translation_unit = {
+            let _t =
+                Timer::new("translation_unit").with_output(options.time_phases);
+
+            clang::TranslationUnit::parse(
+                &index,
+                "",
+                &options.clang_args,
+                input_unsaved_files,
+                parse_options,
+            ).expect("libclang error; possible causes include:
+- Invalid flag syntax
+- Unrecognized flags
+- Invalid flag arguments
+- File I/O errors
+- Host vs. target architecture mismatch
+If you encounter an error missing from this list, please file an issue or a PR!")
+        };
+
+        let target_info = clang::TargetInfo::new(&translation_unit);
+        let root_module = Self::build_root_module(ItemId(0));
+        let root_module_id = root_module.id().as_module_id_unchecked();
+
+        // depfiles need to include the explicitly listed headers too
+        let deps = options.input_headers.iter().cloned().collect();
+
+        BindgenContext {
+            items: vec![Some(root_module)],
+            includes: Default::default(),
+            deps,
+            types: Default::default(),
+            type_params: Default::default(),
+            modules: Default::default(),
+            root_module: root_module_id,
+            current_module: root_module_id,
+            semantic_parents: Default::default(),
+            currently_parsed_types: vec![],
+            parsed_macros: Default::default(),
+            replacements: Default::default(),
+            collected_typerefs: false,
+            in_codegen: false,
+            translation_unit,
+            target_info,
+            options,
+            generated_bindgen_complex: Cell::new(false),
+            generated_bindgen_float16: Cell::new(false),
+            allowlisted: None,
+            blocklisted_types_implement_traits: Default::default(),
+            codegen_items: None,
+            used_template_parameters: None,
+            need_bitfield_allocation: Default::default(),
+            enum_typedef_combos: None,
+            cannot_derive_debug: None,
+            cannot_derive_default: None,
+            cannot_derive_copy: None,
+            cannot_derive_hash: None,
+            cannot_derive_partialeq_or_partialord: None,
+            sizedness: None,
+            have_vtable: None,
+            have_destructor: None,
+            has_type_param_in_array: None,
+            has_float: None,
+        }
+    }
+
+    /// Returns `true` if the target architecture is wasm32
+    pub(crate) fn is_target_wasm32(&self) -> bool {
+        self.target_info.triple.starts_with("wasm32-")
+    }
+
+    /// Creates a timer for the current bindgen phase. If time_phases is `true`,
+    /// the timer will print to stderr when it is dropped, otherwise it will do
+    /// nothing.
+    pub(crate) fn timer<'a>(&self, name: &'a str) -> Timer<'a> {
+        Timer::new(name).with_output(self.options.time_phases)
+    }
+
+    /// Returns the pointer width to use for the target for the current
+    /// translation.
+    pub(crate) fn target_pointer_size(&self) -> usize {
+        self.target_info.pointer_width / 8
+    }
+
+    /// Returns the ABI, which is mostly useful for determining the mangling kind.
+    pub(crate) fn abi_kind(&self) -> ABIKind {
+        self.target_info.abi
+    }
+
+    /// Get the stack of partially parsed types that we are in the middle of
+    /// parsing.
+    pub(crate) fn currently_parsed_types(&self) -> &[PartialType] {
+        &self.currently_parsed_types[..]
+    }
+
+    /// Begin parsing the given partial type, and push it onto the
+    /// `currently_parsed_types` stack so that we won't infinite recurse if we
+    /// run into a reference to it while parsing it.
+    pub(crate) fn begin_parsing(&mut self, partial_ty: PartialType) {
+        self.currently_parsed_types.push(partial_ty);
+    }
+
+    /// Finish parsing the current partial type, pop it off the
+    /// `currently_parsed_types` stack, and return it.
+    pub(crate) fn finish_parsing(&mut self) -> PartialType {
+        self.currently_parsed_types.pop().expect(
+            "should have been parsing a type, if we finished parsing a type",
+        )
+    }
+
+    /// Add the location of the `#include` directive for the `included_file`.
+    pub(crate) fn add_include(
+        &mut self,
+        source_file: String,
+        included_file: String,
+        offset: usize,
+    ) {
+        self.includes
+            .entry(included_file)
+            .or_insert((source_file, offset));
+    }
+
+    /// Get the location of the first `#include` directive for the `included_file`.
+    pub(crate) fn included_file_location(
+        &self,
+        included_file: &str,
+    ) -> Option<(String, usize)> {
+        self.includes.get(included_file).cloned()
+    }
+
+    /// Add an included file.
+    pub(crate) fn add_dep(&mut self, dep: Box<str>) {
+        self.deps.insert(dep);
+    }
+
+    /// Get any included files.
+    pub(crate) fn deps(&self) -> &BTreeSet<Box<str>> {
+        &self.deps
+    }
+
+    /// Define a new item.
+    ///
+    /// This inserts it into the internal items set, and its type into the
+    /// internal types set.
+    pub(crate) fn add_item(
+        &mut self,
+        item: Item,
+        declaration: Option<Cursor>,
+        location: Option<Cursor>,
+    ) {
+        debug!(
+            "BindgenContext::add_item({:?}, declaration: {:?}, loc: {:?}",
+            item, declaration, location
+        );
+        debug_assert!(
+            declaration.is_some() ||
+                !item.kind().is_type() ||
+                item.kind().expect_type().is_builtin_or_type_param() ||
+                item.kind().expect_type().is_opaque(self, &item) ||
+                item.kind().expect_type().is_unresolved_ref(),
+            "Adding a type without declaration?"
+        );
+
+        let id = item.id();
+        let is_type = item.kind().is_type();
+        let is_unnamed = is_type && item.expect_type().name().is_none();
+        let is_template_instantiation =
+            is_type && item.expect_type().is_template_instantiation();
+
+        if item.id() != self.root_module {
+            self.add_item_to_module(&item);
+        }
+
+        if is_type && item.expect_type().is_comp() {
+            self.need_bitfield_allocation.push(id);
+        }
+
+        let old_item = mem::replace(&mut self.items[id.0], Some(item));
+        assert!(
+            old_item.is_none(),
+            "should not have already associated an item with the given id"
+        );
+
+        // Unnamed items can have an USR, but they can't be referenced from
+        // other sites explicitly and the USR can match if the unnamed items are
+        // nested, so don't bother tracking them.
+        if !is_type || is_template_instantiation {
+            return;
+        }
+        if let Some(mut declaration) = declaration {
+            if !declaration.is_valid() {
+                if let Some(location) = location {
+                    if location.is_template_like() {
+                        declaration = location;
+                    }
+                }
+            }
+            declaration = declaration.canonical();
+            if !declaration.is_valid() {
+                // This could happen, for example, with types like `int*` or
+                // similar.
+                //
+                // Fortunately, we don't care about those types being
+                // duplicated, so we can just ignore them.
+                debug!(
+                    "Invalid declaration {:?} found for type {:?}",
+                    declaration,
+                    self.resolve_item_fallible(id)
+                        .unwrap()
+                        .kind()
+                        .expect_type()
+                );
+                return;
+            }
+
+            let key = if is_unnamed {
+                TypeKey::Declaration(declaration)
+            } else if let Some(usr) = declaration.usr() {
+                TypeKey::Usr(usr)
+            } else {
+                warn!(
+                    "Valid declaration with no USR: {:?}, {:?}",
+                    declaration, location
+                );
+                TypeKey::Declaration(declaration)
+            };
+
+            let old = self.types.insert(key, id.as_type_id_unchecked());
+            debug_assert_eq!(old, None);
+        }
+    }
+
+    /// Ensure that every item (other than the root module) is in a module's
+    /// children list. This is to make sure that every allowlisted item get's
+    /// codegen'd, even if its parent is not allowlisted. See issue #769 for
+    /// details.
+    fn add_item_to_module(&mut self, item: &Item) {
+        assert!(item.id() != self.root_module);
+        assert!(self.resolve_item_fallible(item.id()).is_none());
+
+        if let Some(ref mut parent) = self.items[item.parent_id().0] {
+            if let Some(module) = parent.as_module_mut() {
+                debug!(
+                    "add_item_to_module: adding {:?} as child of parent module {:?}",
+                    item.id(),
+                    item.parent_id()
+                );
+
+                module.children_mut().insert(item.id());
+                return;
+            }
+        }
+
+        debug!(
+            "add_item_to_module: adding {:?} as child of current module {:?}",
+            item.id(),
+            self.current_module
+        );
+
+        self.items[(self.current_module.0).0]
+            .as_mut()
+            .expect("Should always have an item for self.current_module")
+            .as_module_mut()
+            .expect("self.current_module should always be a module")
+            .children_mut()
+            .insert(item.id());
+    }
+
+    /// Add a new named template type parameter to this context's item set.
+    pub(crate) fn add_type_param(
+        &mut self,
+        item: Item,
+        definition: clang::Cursor,
+    ) {
+        debug!(
+            "BindgenContext::add_type_param: item = {:?}; definition = {:?}",
+            item, definition
+        );
+
+        assert!(
+            item.expect_type().is_type_param(),
+            "Should directly be a named type, not a resolved reference or anything"
+        );
+        assert_eq!(
+            definition.kind(),
+            clang_sys::CXCursor_TemplateTypeParameter
+        );
+
+        self.add_item_to_module(&item);
+
+        let id = item.id();
+        let old_item = mem::replace(&mut self.items[id.0], Some(item));
+        assert!(
+            old_item.is_none(),
+            "should not have already associated an item with the given id"
+        );
+
+        let old_named_ty = self
+            .type_params
+            .insert(definition, id.as_type_id_unchecked());
+        assert!(
+            old_named_ty.is_none(),
+            "should not have already associated a named type with this id"
+        );
+    }
+
+    /// Get the named type defined at the given cursor location, if we've
+    /// already added one.
+    pub(crate) fn get_type_param(
+        &self,
+        definition: &clang::Cursor,
+    ) -> Option<TypeId> {
+        assert_eq!(
+            definition.kind(),
+            clang_sys::CXCursor_TemplateTypeParameter
+        );
+        self.type_params.get(definition).cloned()
+    }
+
+    // TODO: Move all this syntax crap to other part of the code.
+
+    /// Mangles a name so it doesn't conflict with any keyword.
+    #[rustfmt::skip]
+    pub(crate) fn rust_mangle<'a>(&self, name: &'a str) -> Cow<'a, str> {
+        if name.contains('@') ||
+            name.contains('?') ||
+            name.contains('$') ||
+            matches!(
+                name,
+                "abstract" | "alignof" | "as" | "async" | "await" | "become" |
+                    "box" | "break" | "const" | "continue" | "crate" | "do" |
+                    "dyn" | "else" | "enum" | "extern" | "false" | "final" |
+                    "fn" | "for" | "if" | "impl" | "in" | "let" | "loop" |
+                    "macro" | "match" | "mod" | "move" | "mut" | "offsetof" |
+                    "override" | "priv" | "proc" | "pub" | "pure" | "ref" |
+                    "return" | "Self" | "self" | "sizeof" | "static" |
+                    "struct" | "super" | "trait" | "true" | "try" | "type" | "typeof" |
+                    "unsafe" | "unsized" | "use" | "virtual" | "where" |
+                    "while" | "yield" | "str" | "bool" | "f32" | "f64" |
+                    "usize" | "isize" | "u128" | "i128" | "u64" | "i64" |
+                    "u32" | "i32" | "u16" | "i16" | "u8" | "i8" | "_"
+            )
+        {
+            let mut s = name.to_owned();
+            s = s.replace('@', "_");
+            s = s.replace('?', "_");
+            s = s.replace('$', "_");
+            s.push('_');
+            return Cow::Owned(s);
+        }
+        Cow::Borrowed(name)
+    }
+
+    /// Returns a mangled name as a rust identifier.
+    pub(crate) fn rust_ident<S>(&self, name: S) -> Ident
+    where
+        S: AsRef<str>,
+    {
+        self.rust_ident_raw(self.rust_mangle(name.as_ref()))
+    }
+
+    /// Returns a mangled name as a rust identifier.
+    pub(crate) fn rust_ident_raw<T>(&self, name: T) -> Ident
+    where
+        T: AsRef<str>,
+    {
+        Ident::new(name.as_ref(), Span::call_site())
+    }
+
+    /// Iterate over all items that have been defined.
+    pub(crate) fn items(&self) -> impl Iterator<Item = (ItemId, &Item)> {
+        self.items.iter().enumerate().filter_map(|(index, item)| {
+            let item = item.as_ref()?;
+            Some((ItemId(index), item))
+        })
+    }
+
+    /// Have we collected all unresolved type references yet?
+    pub(crate) fn collected_typerefs(&self) -> bool {
+        self.collected_typerefs
+    }
+
+    /// Gather all the unresolved type references.
+    fn collect_typerefs(
+        &mut self,
+    ) -> Vec<(ItemId, clang::Type, clang::Cursor, Option<ItemId>)> {
+        debug_assert!(!self.collected_typerefs);
+        self.collected_typerefs = true;
+        let mut typerefs = vec![];
+
+        for (id, item) in self.items() {
+            let kind = item.kind();
+            let ty = match kind.as_type() {
+                Some(ty) => ty,
+                None => continue,
+            };
+
+            if let TypeKind::UnresolvedTypeRef(ref ty, loc, parent_id) =
+                *ty.kind()
+            {
+                typerefs.push((id, *ty, loc, parent_id));
+            };
+        }
+        typerefs
+    }
+
+    /// Collect all of our unresolved type references and resolve them.
+    fn resolve_typerefs(&mut self) {
+        let _t = self.timer("resolve_typerefs");
+
+        let typerefs = self.collect_typerefs();
+
+        for (id, ty, loc, parent_id) in typerefs {
+            let _resolved =
+                {
+                    let resolved = Item::from_ty(&ty, loc, parent_id, self)
+                    .unwrap_or_else(|_| {
+                        warn!("Could not resolve type reference, falling back \
+                               to opaque blob");
+                        Item::new_opaque_type(self.next_item_id(), &ty, self)
+                    });
+
+                    let item = self.items[id.0].as_mut().unwrap();
+                    *item.kind_mut().as_type_mut().unwrap().kind_mut() =
+                        TypeKind::ResolvedTypeRef(resolved);
+                    resolved
+                };
+
+            // Something in the STL is trolling me. I don't need this assertion
+            // right now, but worth investigating properly once this lands.
+            //
+            // debug_assert!(self.items.get(&resolved).is_some(), "How?");
+            //
+            // if let Some(parent_id) = parent_id {
+            //     assert_eq!(self.items[&resolved].parent_id(), parent_id);
+            // }
+        }
+    }
+
+    /// Temporarily loan `Item` with the given `ItemId`. This provides means to
+    /// mutably borrow `Item` while having a reference to `BindgenContext`.
+    ///
+    /// `Item` with the given `ItemId` is removed from the context, given
+    /// closure is executed and then `Item` is placed back.
+    ///
+    /// # Panics
+    ///
+    /// Panics if attempt to resolve given `ItemId` inside the given
+    /// closure is made.
+    fn with_loaned_item<F, T>(&mut self, id: ItemId, f: F) -> T
+    where
+        F: (FnOnce(&BindgenContext, &mut Item) -> T),
+    {
+        let mut item = self.items[id.0].take().unwrap();
+
+        let result = f(self, &mut item);
+
+        let existing = mem::replace(&mut self.items[id.0], Some(item));
+        assert!(existing.is_none());
+
+        result
+    }
+
+    /// Compute the bitfield allocation units for all `TypeKind::Comp` items we
+    /// parsed.
+    fn compute_bitfield_units(&mut self) {
+        let _t = self.timer("compute_bitfield_units");
+
+        assert!(self.collected_typerefs());
+
+        let need_bitfield_allocation =
+            mem::take(&mut self.need_bitfield_allocation);
+        for id in need_bitfield_allocation {
+            self.with_loaned_item(id, |ctx, item| {
+                let ty = item.kind_mut().as_type_mut().unwrap();
+                let layout = ty.layout(ctx);
+                ty.as_comp_mut()
+                    .unwrap()
+                    .compute_bitfield_units(ctx, layout.as_ref());
+            });
+        }
+    }
+
+    /// Assign a new generated name for each anonymous field.
+    fn deanonymize_fields(&mut self) {
+        let _t = self.timer("deanonymize_fields");
+
+        let comp_item_ids: Vec<ItemId> = self
+            .items()
+            .filter_map(|(id, item)| {
+                if item.kind().as_type()?.is_comp() {
+                    return Some(id);
+                }
+                None
+            })
+            .collect();
+
+        for id in comp_item_ids {
+            self.with_loaned_item(id, |ctx, item| {
+                item.kind_mut()
+                    .as_type_mut()
+                    .unwrap()
+                    .as_comp_mut()
+                    .unwrap()
+                    .deanonymize_fields(ctx);
+            });
+        }
+    }
+
+    /// Iterate over all items and replace any item that has been named in a
+    /// `replaces="SomeType"` annotation with the replacement type.
+    fn process_replacements(&mut self) {
+        let _t = self.timer("process_replacements");
+        if self.replacements.is_empty() {
+            debug!("No replacements to process");
+            return;
+        }
+
+        // FIXME: This is linear, but the replaces="xxx" annotation was already
+        // there, and for better or worse it's useful, sigh...
+        //
+        // We leverage the ResolvedTypeRef thing, though, which is cool :P.
+
+        let mut replacements = vec![];
+
+        for (id, item) in self.items() {
+            if item.annotations().use_instead_of().is_some() {
+                continue;
+            }
+
+            // Calls to `canonical_name` are expensive, so eagerly filter out
+            // items that cannot be replaced.
+            let ty = match item.kind().as_type() {
+                Some(ty) => ty,
+                None => continue,
+            };
+
+            match *ty.kind() {
+                TypeKind::Comp(..) |
+                TypeKind::TemplateAlias(..) |
+                TypeKind::Enum(..) |
+                TypeKind::Alias(..) => {}
+                _ => continue,
+            }
+
+            let path = item.path_for_allowlisting(self);
+            let replacement = self.replacements.get(&path[1..]);
+
+            if let Some(replacement) = replacement {
+                if *replacement != id {
+                    // We set this just after parsing the annotation. It's
+                    // very unlikely, but this can happen.
+                    if self.resolve_item_fallible(*replacement).is_some() {
+                        replacements.push((
+                            id.expect_type_id(self),
+                            replacement.expect_type_id(self),
+                        ));
+                    }
+                }
+            }
+        }
+
+        for (id, replacement_id) in replacements {
+            debug!("Replacing {:?} with {:?}", id, replacement_id);
+            let new_parent = {
+                let item_id: ItemId = id.into();
+                let item = self.items[item_id.0].as_mut().unwrap();
+                *item.kind_mut().as_type_mut().unwrap().kind_mut() =
+                    TypeKind::ResolvedTypeRef(replacement_id);
+                item.parent_id()
+            };
+
+            // Relocate the replacement item from where it was declared, to
+            // where the thing it is replacing was declared.
+            //
+            // First, we'll make sure that its parent ID is correct.
+
+            let old_parent = self.resolve_item(replacement_id).parent_id();
+            if new_parent == old_parent {
+                // Same parent and therefore also same containing
+                // module. Nothing to do here.
+                continue;
+            }
+
+            let replacement_item_id: ItemId = replacement_id.into();
+            self.items[replacement_item_id.0]
+                .as_mut()
+                .unwrap()
+                .set_parent_for_replacement(new_parent);
+
+            // Second, make sure that it is in the correct module's children
+            // set.
+
+            let old_module = {
+                let immut_self = &*self;
+                old_parent
+                    .ancestors(immut_self)
+                    .chain(Some(immut_self.root_module.into()))
+                    .find(|id| {
+                        let item = immut_self.resolve_item(*id);
+                        item.as_module().map_or(false, |m| {
+                            m.children().contains(&replacement_id.into())
+                        })
+                    })
+            };
+            let old_module = old_module
+                .expect("Every replacement item should be in a module");
+
+            let new_module = {
+                let immut_self = &*self;
+                new_parent
+                    .ancestors(immut_self)
+                    .find(|id| immut_self.resolve_item(*id).is_module())
+            };
+            let new_module =
+                new_module.unwrap_or_else(|| self.root_module.into());
+
+            if new_module == old_module {
+                // Already in the correct module.
+                continue;
+            }
+
+            self.items[old_module.0]
+                .as_mut()
+                .unwrap()
+                .as_module_mut()
+                .unwrap()
+                .children_mut()
+                .remove(&replacement_id.into());
+
+            self.items[new_module.0]
+                .as_mut()
+                .unwrap()
+                .as_module_mut()
+                .unwrap()
+                .children_mut()
+                .insert(replacement_id.into());
+        }
+    }
+
+    /// Enter the code generation phase, invoke the given callback `cb`, and
+    /// leave the code generation phase.
+    pub(crate) fn gen<F, Out>(
+        mut self,
+        cb: F,
+    ) -> Result<(Out, BindgenOptions), CodegenError>
+    where
+        F: FnOnce(&Self) -> Result<Out, CodegenError>,
+    {
+        self.in_codegen = true;
+
+        self.resolve_typerefs();
+        self.compute_bitfield_units();
+        self.process_replacements();
+
+        self.deanonymize_fields();
+
+        self.assert_no_dangling_references();
+
+        // Compute the allowlisted set after processing replacements and
+        // resolving type refs, as those are the final mutations of the IR
+        // graph, and their completion means that the IR graph is now frozen.
+        self.compute_allowlisted_and_codegen_items();
+
+        // Make sure to do this after processing replacements, since that messes
+        // with the parentage and module children, and we want to assert that it
+        // messes with them correctly.
+        self.assert_every_item_in_a_module();
+
+        self.compute_has_vtable();
+        self.compute_sizedness();
+        self.compute_has_destructor();
+        self.find_used_template_parameters();
+        self.compute_enum_typedef_combos();
+        self.compute_cannot_derive_debug();
+        self.compute_cannot_derive_default();
+        self.compute_cannot_derive_copy();
+        self.compute_has_type_param_in_array();
+        self.compute_has_float();
+        self.compute_cannot_derive_hash();
+        self.compute_cannot_derive_partialord_partialeq_or_eq();
+
+        let ret = cb(&self)?;
+        Ok((ret, self.options))
+    }
+
+    /// When the `__testing_only_extra_assertions` feature is enabled, this
+    /// function walks the IR graph and asserts that we do not have any edges
+    /// referencing an ItemId for which we do not have an associated IR item.
+    fn assert_no_dangling_references(&self) {
+        if cfg!(feature = "__testing_only_extra_assertions") {
+            for _ in self.assert_no_dangling_item_traversal() {
+                // The iterator's next method does the asserting for us.
+            }
+        }
+    }
+
+    fn assert_no_dangling_item_traversal(
+        &self,
+    ) -> traversal::AssertNoDanglingItemsTraversal {
+        assert!(self.in_codegen_phase());
+        assert!(self.current_module == self.root_module);
+
+        let roots = self.items().map(|(id, _)| id);
+        traversal::AssertNoDanglingItemsTraversal::new(
+            self,
+            roots,
+            traversal::all_edges,
+        )
+    }
+
+    /// When the `__testing_only_extra_assertions` feature is enabled, walk over
+    /// every item and ensure that it is in the children set of one of its
+    /// module ancestors.
+    fn assert_every_item_in_a_module(&self) {
+        if cfg!(feature = "__testing_only_extra_assertions") {
+            assert!(self.in_codegen_phase());
+            assert!(self.current_module == self.root_module);
+
+            for (id, _item) in self.items() {
+                if id == self.root_module {
+                    continue;
+                }
+
+                assert!(
+                    {
+                        let id = id
+                            .into_resolver()
+                            .through_type_refs()
+                            .through_type_aliases()
+                            .resolve(self)
+                            .id();
+                        id.ancestors(self)
+                            .chain(Some(self.root_module.into()))
+                            .any(|ancestor| {
+                                debug!(
+                                    "Checking if {:?} is a child of {:?}",
+                                    id, ancestor
+                                );
+                                self.resolve_item(ancestor)
+                                    .as_module()
+                                    .map_or(false, |m| {
+                                        m.children().contains(&id)
+                                    })
+                            })
+                    },
+                    "{:?} should be in some ancestor module's children set",
+                    id
+                );
+            }
+        }
+    }
+
+    /// Compute for every type whether it is sized or not, and whether it is
+    /// sized or not as a base class.
+    fn compute_sizedness(&mut self) {
+        let _t = self.timer("compute_sizedness");
+        assert!(self.sizedness.is_none());
+        self.sizedness = Some(analyze::<SizednessAnalysis>(self));
+    }
+
+    /// Look up whether the type with the given ID is sized or not.
+    pub(crate) fn lookup_sizedness(&self, id: TypeId) -> SizednessResult {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute sizedness after we've entered codegen"
+        );
+
+        self.sizedness
+            .as_ref()
+            .unwrap()
+            .get(&id)
+            .cloned()
+            .unwrap_or(SizednessResult::ZeroSized)
+    }
+
+    /// Compute whether the type has vtable.
+    fn compute_has_vtable(&mut self) {
+        let _t = self.timer("compute_has_vtable");
+        assert!(self.have_vtable.is_none());
+        self.have_vtable = Some(analyze::<HasVtableAnalysis>(self));
+    }
+
+    /// Look up whether the item with `id` has vtable or not.
+    pub(crate) fn lookup_has_vtable(&self, id: TypeId) -> HasVtableResult {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute vtables when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` has a
+        // vtable or not.
+        self.have_vtable
+            .as_ref()
+            .unwrap()
+            .get(&id.into())
+            .cloned()
+            .unwrap_or(HasVtableResult::No)
+    }
+
+    /// Compute whether the type has a destructor.
+    fn compute_has_destructor(&mut self) {
+        let _t = self.timer("compute_has_destructor");
+        assert!(self.have_destructor.is_none());
+        self.have_destructor = Some(analyze::<HasDestructorAnalysis>(self));
+    }
+
+    /// Look up whether the item with `id` has a destructor.
+    pub(crate) fn lookup_has_destructor(&self, id: TypeId) -> bool {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute destructors when we enter codegen"
+        );
+
+        self.have_destructor.as_ref().unwrap().contains(&id.into())
+    }
+
+    fn find_used_template_parameters(&mut self) {
+        let _t = self.timer("find_used_template_parameters");
+        if self.options.allowlist_recursively {
+            let used_params = analyze::<UsedTemplateParameters>(self);
+            self.used_template_parameters = Some(used_params);
+        } else {
+            // If you aren't recursively allowlisting, then we can't really make
+            // any sense of template parameter usage, and you're on your own.
+            let mut used_params = HashMap::default();
+            for &id in self.allowlisted_items() {
+                used_params.entry(id).or_insert_with(|| {
+                    id.self_template_params(self)
+                        .into_iter()
+                        .map(|p| p.into())
+                        .collect()
+                });
+            }
+            self.used_template_parameters = Some(used_params);
+        }
+    }
+
+    /// Return `true` if `item` uses the given `template_param`, `false`
+    /// otherwise.
+    ///
+    /// This method may only be called during the codegen phase, because the
+    /// template usage information is only computed as we enter the codegen
+    /// phase.
+    ///
+    /// If the item is blocklisted, then we say that it always uses the template
+    /// parameter. This is a little subtle. The template parameter usage
+    /// analysis only considers allowlisted items, and if any blocklisted item
+    /// shows up in the generated bindings, it is the user's responsibility to
+    /// manually provide a definition for them. To give them the most
+    /// flexibility when doing that, we assume that they use every template
+    /// parameter and always pass template arguments through in instantiations.
+    pub(crate) fn uses_template_parameter(
+        &self,
+        item: ItemId,
+        template_param: TypeId,
+    ) -> bool {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute template parameter usage as we enter codegen"
+        );
+
+        if self.resolve_item(item).is_blocklisted(self) {
+            return true;
+        }
+
+        let template_param = template_param
+            .into_resolver()
+            .through_type_refs()
+            .through_type_aliases()
+            .resolve(self)
+            .id();
+
+        self.used_template_parameters
+            .as_ref()
+            .expect("should have found template parameter usage if we're in codegen")
+            .get(&item)
+            .map_or(false, |items_used_params| items_used_params.contains(&template_param))
+    }
+
+    /// Return `true` if `item` uses any unbound, generic template parameters,
+    /// `false` otherwise.
+    ///
+    /// Has the same restrictions that `uses_template_parameter` has.
+    pub(crate) fn uses_any_template_parameters(&self, item: ItemId) -> bool {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute template parameter usage as we enter codegen"
+        );
+
+        self.used_template_parameters
+            .as_ref()
+            .expect(
+                "should have template parameter usage info in codegen phase",
+            )
+            .get(&item)
+            .map_or(false, |used| !used.is_empty())
+    }
+
+    // This deserves a comment. Builtin types don't get a valid declaration, so
+    // we can't add it to the cursor->type map.
+    //
+    // That being said, they're not generated anyway, and are few, so the
+    // duplication and special-casing is fine.
+    //
+    // If at some point we care about the memory here, probably a map TypeKind
+    // -> builtin type ItemId would be the best to improve that.
+    fn add_builtin_item(&mut self, item: Item) {
+        debug!("add_builtin_item: item = {:?}", item);
+        debug_assert!(item.kind().is_type());
+        self.add_item_to_module(&item);
+        let id = item.id();
+        let old_item = mem::replace(&mut self.items[id.0], Some(item));
+        assert!(old_item.is_none(), "Inserted type twice?");
+    }
+
+    fn build_root_module(id: ItemId) -> Item {
+        let module = Module::new(Some("root".into()), ModuleKind::Normal);
+        Item::new(id, None, None, id, ItemKind::Module(module), None)
+    }
+
+    /// Get the root module.
+    pub(crate) fn root_module(&self) -> ModuleId {
+        self.root_module
+    }
+
+    /// Resolve a type with the given ID.
+    ///
+    /// Panics if there is no item for the given `TypeId` or if the resolved
+    /// item is not a `Type`.
+    pub(crate) fn resolve_type(&self, type_id: TypeId) -> &Type {
+        self.resolve_item(type_id).kind().expect_type()
+    }
+
+    /// Resolve a function with the given ID.
+    ///
+    /// Panics if there is no item for the given `FunctionId` or if the resolved
+    /// item is not a `Function`.
+    pub(crate) fn resolve_func(&self, func_id: FunctionId) -> &Function {
+        self.resolve_item(func_id).kind().expect_function()
+    }
+
+    /// Resolve the given `ItemId` as a type, or `None` if there is no item with
+    /// the given ID.
+    ///
+    /// Panics if the ID resolves to an item that is not a type.
+    pub(crate) fn safe_resolve_type(&self, type_id: TypeId) -> Option<&Type> {
+        self.resolve_item_fallible(type_id)
+            .map(|t| t.kind().expect_type())
+    }
+
+    /// Resolve the given `ItemId` into an `Item`, or `None` if no such item
+    /// exists.
+    pub(crate) fn resolve_item_fallible<Id: Into<ItemId>>(
+        &self,
+        id: Id,
+    ) -> Option<&Item> {
+        self.items.get(id.into().0)?.as_ref()
+    }
+
+    /// Resolve the given `ItemId` into an `Item`.
+    ///
+    /// Panics if the given ID does not resolve to any item.
+    pub(crate) fn resolve_item<Id: Into<ItemId>>(&self, item_id: Id) -> &Item {
+        let item_id = item_id.into();
+        match self.resolve_item_fallible(item_id) {
+            Some(item) => item,
+            None => panic!("Not an item: {:?}", item_id),
+        }
+    }
+
+    /// Get the current module.
+    pub(crate) fn current_module(&self) -> ModuleId {
+        self.current_module
+    }
+
+    /// Add a semantic parent for a given type definition.
+    ///
+    /// We do this from the type declaration, in order to be able to find the
+    /// correct type definition afterwards.
+    ///
+    /// TODO(emilio): We could consider doing this only when
+    /// declaration.lexical_parent() != definition.lexical_parent(), but it's
+    /// not sure it's worth it.
+    pub(crate) fn add_semantic_parent(
+        &mut self,
+        definition: clang::Cursor,
+        parent_id: ItemId,
+    ) {
+        self.semantic_parents.insert(definition, parent_id);
+    }
+
+    /// Returns a known semantic parent for a given definition.
+    pub(crate) fn known_semantic_parent(
+        &self,
+        definition: clang::Cursor,
+    ) -> Option<ItemId> {
+        self.semantic_parents.get(&definition).cloned()
+    }
+
+    /// Given a cursor pointing to the location of a template instantiation,
+    /// return a tuple of the form `(declaration_cursor, declaration_id,
+    /// num_expected_template_args)`.
+    ///
+    /// Note that `declaration_id` is not guaranteed to be in the context's item
+    /// set! It is possible that it is a partial type that we are still in the
+    /// middle of parsing.
+    fn get_declaration_info_for_template_instantiation(
+        &self,
+        instantiation: &Cursor,
+    ) -> Option<(Cursor, ItemId, usize)> {
+        instantiation
+            .cur_type()
+            .canonical_declaration(Some(instantiation))
+            .and_then(|canon_decl| {
+                self.get_resolved_type(&canon_decl).and_then(
+                    |template_decl_id| {
+                        let num_params =
+                            template_decl_id.num_self_template_params(self);
+                        if num_params == 0 {
+                            None
+                        } else {
+                            Some((
+                                *canon_decl.cursor(),
+                                template_decl_id.into(),
+                                num_params,
+                            ))
+                        }
+                    },
+                )
+            })
+            .or_else(|| {
+                // If we haven't already parsed the declaration of
+                // the template being instantiated, then it *must*
+                // be on the stack of types we are currently
+                // parsing. If it wasn't then clang would have
+                // already errored out before we started
+                // constructing our IR because you can't instantiate
+                // a template until it is fully defined.
+                instantiation
+                    .referenced()
+                    .and_then(|referenced| {
+                        self.currently_parsed_types()
+                            .iter()
+                            .find(|partial_ty| *partial_ty.decl() == referenced)
+                            .cloned()
+                    })
+                    .and_then(|template_decl| {
+                        let num_template_params =
+                            template_decl.num_self_template_params(self);
+                        if num_template_params == 0 {
+                            None
+                        } else {
+                            Some((
+                                *template_decl.decl(),
+                                template_decl.id(),
+                                num_template_params,
+                            ))
+                        }
+                    })
+            })
+    }
+
+    /// Parse a template instantiation, eg `Foo<int>`.
+    ///
+    /// This is surprisingly difficult to do with libclang, due to the fact that
+    /// it doesn't provide explicit template argument information, except for
+    /// function template declarations(!?!??!).
+    ///
+    /// The only way to do this is manually inspecting the AST and looking for
+    /// TypeRefs and TemplateRefs inside. This, unfortunately, doesn't work for
+    /// more complex cases, see the comment on the assertion below.
+    ///
+    /// To add insult to injury, the AST itself has structure that doesn't make
+    /// sense. Sometimes `Foo<Bar<int>>` has an AST with nesting like you might
+    /// expect: `(Foo (Bar (int)))`. Other times, the AST we get is completely
+    /// flat: `(Foo Bar int)`.
+    ///
+    /// To see an example of what this method handles:
+    ///
+    /// ```c++
+    /// template<typename T>
+    /// class Incomplete {
+    ///   T p;
+    /// };
+    ///
+    /// template<typename U>
+    /// class Foo {
+    ///   Incomplete<U> bar;
+    /// };
+    /// ```
+    ///
+    /// Finally, template instantiations are always children of the current
+    /// module. They use their template's definition for their name, so the
+    /// parent is only useful for ensuring that their layout tests get
+    /// codegen'd.
+    fn instantiate_template(
+        &mut self,
+        with_id: ItemId,
+        template: TypeId,
+        ty: &clang::Type,
+        location: clang::Cursor,
+    ) -> Option<TypeId> {
+        let num_expected_args =
+            self.resolve_type(template).num_self_template_params(self);
+        if num_expected_args == 0 {
+            warn!(
+                "Tried to instantiate a template for which we could not \
+                 determine any template parameters"
+            );
+            return None;
+        }
+
+        let mut args = vec![];
+        let mut found_const_arg = false;
+        let mut children = location.collect_children();
+
+        if children.iter().all(|c| !c.has_children()) {
+            // This is insanity... If clang isn't giving us a properly nested
+            // AST for which template arguments belong to which template we are
+            // instantiating, we'll need to construct it ourselves. However,
+            // there is an extra `NamespaceRef, NamespaceRef, ..., TemplateRef`
+            // representing a reference to the outermost template declaration
+            // that we need to filter out of the children. We need to do this
+            // filtering because we already know which template declaration is
+            // being specialized via the `location`'s type, and if we do not
+            // filter it out, we'll add an extra layer of template instantiation
+            // on accident.
+            let idx = children
+                .iter()
+                .position(|c| c.kind() == clang_sys::CXCursor_TemplateRef);
+            if let Some(idx) = idx {
+                if children
+                    .iter()
+                    .take(idx)
+                    .all(|c| c.kind() == clang_sys::CXCursor_NamespaceRef)
+                {
+                    children = children.into_iter().skip(idx + 1).collect();
+                }
+            }
+        }
+
+        for child in children.iter().rev() {
+            match child.kind() {
+                clang_sys::CXCursor_TypeRef |
+                clang_sys::CXCursor_TypedefDecl |
+                clang_sys::CXCursor_TypeAliasDecl => {
+                    // The `with_id` ID will potentially end up unused if we give up
+                    // on this type (for example, because it has const value
+                    // template args), so if we pass `with_id` as the parent, it is
+                    // potentially a dangling reference. Instead, use the canonical
+                    // template declaration as the parent. It is already parsed and
+                    // has a known-resolvable `ItemId`.
+                    let ty = Item::from_ty_or_ref(
+                        child.cur_type(),
+                        *child,
+                        Some(template.into()),
+                        self,
+                    );
+                    args.push(ty);
+                }
+                clang_sys::CXCursor_TemplateRef => {
+                    let (
+                        template_decl_cursor,
+                        template_decl_id,
+                        num_expected_template_args,
+                    ) = self.get_declaration_info_for_template_instantiation(
+                        child,
+                    )?;
+
+                    if num_expected_template_args == 0 ||
+                        child.has_at_least_num_children(
+                            num_expected_template_args,
+                        )
+                    {
+                        // Do a happy little parse. See comment in the TypeRef
+                        // match arm about parent IDs.
+                        let ty = Item::from_ty_or_ref(
+                            child.cur_type(),
+                            *child,
+                            Some(template.into()),
+                            self,
+                        );
+                        args.push(ty);
+                    } else {
+                        // This is the case mentioned in the doc comment where
+                        // clang gives us a flattened AST and we have to
+                        // reconstruct which template arguments go to which
+                        // instantiation :(
+                        let args_len = args.len();
+                        if args_len < num_expected_template_args {
+                            warn!(
+                                "Found a template instantiation without \
+                                 enough template arguments"
+                            );
+                            return None;
+                        }
+
+                        let mut sub_args: Vec<_> = args
+                            .drain(args_len - num_expected_template_args..)
+                            .collect();
+                        sub_args.reverse();
+
+                        let sub_name = Some(template_decl_cursor.spelling());
+                        let sub_inst = TemplateInstantiation::new(
+                            // This isn't guaranteed to be a type that we've
+                            // already finished parsing yet.
+                            template_decl_id.as_type_id_unchecked(),
+                            sub_args,
+                        );
+                        let sub_kind =
+                            TypeKind::TemplateInstantiation(sub_inst);
+                        let sub_ty = Type::new(
+                            sub_name,
+                            template_decl_cursor
+                                .cur_type()
+                                .fallible_layout(self)
+                                .ok(),
+                            sub_kind,
+                            false,
+                        );
+                        let sub_id = self.next_item_id();
+                        let sub_item = Item::new(
+                            sub_id,
+                            None,
+                            None,
+                            self.current_module.into(),
+                            ItemKind::Type(sub_ty),
+                            Some(child.location()),
+                        );
+
+                        // Bypass all the validations in add_item explicitly.
+                        debug!(
+                            "instantiate_template: inserting nested \
+                             instantiation item: {:?}",
+                            sub_item
+                        );
+                        self.add_item_to_module(&sub_item);
+                        debug_assert_eq!(sub_id, sub_item.id());
+                        self.items[sub_id.0] = Some(sub_item);
+                        args.push(sub_id.as_type_id_unchecked());
+                    }
+                }
+                _ => {
+                    warn!(
+                        "Found template arg cursor we can't handle: {:?}",
+                        child
+                    );
+                    found_const_arg = true;
+                }
+            }
+        }
+
+        if found_const_arg {
+            // This is a dependently typed template instantiation. That is, an
+            // instantiation of a template with one or more const values as
+            // template arguments, rather than only types as template
+            // arguments. For example, `Foo<true, 5>` versus `Bar<bool, int>`.
+            // We can't handle these instantiations, so just punt in this
+            // situation...
+            warn!(
+                "Found template instantiated with a const value; \
+                 bindgen can't handle this kind of template instantiation!"
+            );
+            return None;
+        }
+
+        if args.len() != num_expected_args {
+            warn!(
+                "Found a template with an unexpected number of template \
+                 arguments"
+            );
+            return None;
+        }
+
+        args.reverse();
+        let type_kind = TypeKind::TemplateInstantiation(
+            TemplateInstantiation::new(template, args),
+        );
+        let name = ty.spelling();
+        let name = if name.is_empty() { None } else { Some(name) };
+        let ty = Type::new(
+            name,
+            ty.fallible_layout(self).ok(),
+            type_kind,
+            ty.is_const(),
+        );
+        let item = Item::new(
+            with_id,
+            None,
+            None,
+            self.current_module.into(),
+            ItemKind::Type(ty),
+            Some(location.location()),
+        );
+
+        // Bypass all the validations in add_item explicitly.
+        debug!("instantiate_template: inserting item: {:?}", item);
+        self.add_item_to_module(&item);
+        debug_assert_eq!(with_id, item.id());
+        self.items[with_id.0] = Some(item);
+        Some(with_id.as_type_id_unchecked())
+    }
+
+    /// If we have already resolved the type for the given type declaration,
+    /// return its `ItemId`. Otherwise, return `None`.
+    pub(crate) fn get_resolved_type(
+        &self,
+        decl: &clang::CanonicalTypeDeclaration,
+    ) -> Option<TypeId> {
+        self.types
+            .get(&TypeKey::Declaration(*decl.cursor()))
+            .or_else(|| {
+                decl.cursor()
+                    .usr()
+                    .and_then(|usr| self.types.get(&TypeKey::Usr(usr)))
+            })
+            .cloned()
+    }
+
+    /// Looks up for an already resolved type, either because it's builtin, or
+    /// because we already have it in the map.
+    pub(crate) fn builtin_or_resolved_ty(
+        &mut self,
+        with_id: ItemId,
+        parent_id: Option<ItemId>,
+        ty: &clang::Type,
+        location: Option<clang::Cursor>,
+    ) -> Option<TypeId> {
+        use clang_sys::{CXCursor_TypeAliasTemplateDecl, CXCursor_TypeRef};
+        debug!(
+            "builtin_or_resolved_ty: {:?}, {:?}, {:?}, {:?}",
+            ty, location, with_id, parent_id
+        );
+
+        if let Some(decl) = ty.canonical_declaration(location.as_ref()) {
+            if let Some(id) = self.get_resolved_type(&decl) {
+                debug!(
+                    "Already resolved ty {:?}, {:?}, {:?} {:?}",
+                    id, decl, ty, location
+                );
+                // If the declaration already exists, then either:
+                //
+                //   * the declaration is a template declaration of some sort,
+                //     and we are looking at an instantiation or specialization
+                //     of it, or
+                //   * we have already parsed and resolved this type, and
+                //     there's nothing left to do.
+                if let Some(location) = location {
+                    if decl.cursor().is_template_like() &&
+                        *ty != decl.cursor().cur_type()
+                    {
+                        // For specialized type aliases, there's no way to get the
+                        // template parameters as of this writing (for a struct
+                        // specialization we wouldn't be in this branch anyway).
+                        //
+                        // Explicitly return `None` if there aren't any
+                        // unspecialized parameters (contains any `TypeRef`) so we
+                        // resolve the canonical type if there is one and it's
+                        // exposed.
+                        //
+                        // This is _tricky_, I know :(
+                        if decl.cursor().kind() ==
+                            CXCursor_TypeAliasTemplateDecl &&
+                            !location.contains_cursor(CXCursor_TypeRef) &&
+                            ty.canonical_type().is_valid_and_exposed()
+                        {
+                            return None;
+                        }
+
+                        return self
+                            .instantiate_template(with_id, id, ty, location)
+                            .or(Some(id));
+                    }
+                }
+
+                return Some(self.build_ty_wrapper(with_id, id, parent_id, ty));
+            }
+        }
+
+        debug!("Not resolved, maybe builtin?");
+        self.build_builtin_ty(ty)
+    }
+
+    /// Make a new item that is a resolved type reference to the `wrapped_id`.
+    ///
+    /// This is unfortunately a lot of bloat, but is needed to properly track
+    /// constness et al.
+    ///
+    /// We should probably make the constness tracking separate, so it doesn't
+    /// bloat that much, but hey, we already bloat the heck out of builtin
+    /// types.
+    pub(crate) fn build_ty_wrapper(
+        &mut self,
+        with_id: ItemId,
+        wrapped_id: TypeId,
+        parent_id: Option<ItemId>,
+        ty: &clang::Type,
+    ) -> TypeId {
+        self.build_wrapper(with_id, wrapped_id, parent_id, ty, ty.is_const())
+    }
+
+    /// A wrapper over a type that adds a const qualifier explicitly.
+    ///
+    /// Needed to handle const methods in C++, wrapping the type .
+    pub(crate) fn build_const_wrapper(
+        &mut self,
+        with_id: ItemId,
+        wrapped_id: TypeId,
+        parent_id: Option<ItemId>,
+        ty: &clang::Type,
+    ) -> TypeId {
+        self.build_wrapper(
+            with_id, wrapped_id, parent_id, ty, /* is_const = */ true,
+        )
+    }
+
+    fn build_wrapper(
+        &mut self,
+        with_id: ItemId,
+        wrapped_id: TypeId,
+        parent_id: Option<ItemId>,
+        ty: &clang::Type,
+        is_const: bool,
+    ) -> TypeId {
+        let spelling = ty.spelling();
+        let layout = ty.fallible_layout(self).ok();
+        let location = ty.declaration().location();
+        let type_kind = TypeKind::ResolvedTypeRef(wrapped_id);
+        let ty = Type::new(Some(spelling), layout, type_kind, is_const);
+        let item = Item::new(
+            with_id,
+            None,
+            None,
+            parent_id.unwrap_or_else(|| self.current_module.into()),
+            ItemKind::Type(ty),
+            Some(location),
+        );
+        self.add_builtin_item(item);
+        with_id.as_type_id_unchecked()
+    }
+
+    /// Returns the next item ID to be used for an item.
+    pub(crate) fn next_item_id(&mut self) -> ItemId {
+        let ret = ItemId(self.items.len());
+        self.items.push(None);
+        ret
+    }
+
+    fn build_builtin_ty(&mut self, ty: &clang::Type) -> Option<TypeId> {
+        use clang_sys::*;
+        let type_kind = match ty.kind() {
+            CXType_NullPtr => TypeKind::NullPtr,
+            CXType_Void => TypeKind::Void,
+            CXType_Bool => TypeKind::Int(IntKind::Bool),
+            CXType_Int => TypeKind::Int(IntKind::Int),
+            CXType_UInt => TypeKind::Int(IntKind::UInt),
+            CXType_Char_S => TypeKind::Int(IntKind::Char { is_signed: true }),
+            CXType_Char_U => TypeKind::Int(IntKind::Char { is_signed: false }),
+            CXType_SChar => TypeKind::Int(IntKind::SChar),
+            CXType_UChar => TypeKind::Int(IntKind::UChar),
+            CXType_Short => TypeKind::Int(IntKind::Short),
+            CXType_UShort => TypeKind::Int(IntKind::UShort),
+            CXType_WChar => TypeKind::Int(IntKind::WChar),
+            CXType_Char16 => TypeKind::Int(IntKind::U16),
+            CXType_Char32 => TypeKind::Int(IntKind::U32),
+            CXType_Long => TypeKind::Int(IntKind::Long),
+            CXType_ULong => TypeKind::Int(IntKind::ULong),
+            CXType_LongLong => TypeKind::Int(IntKind::LongLong),
+            CXType_ULongLong => TypeKind::Int(IntKind::ULongLong),
+            CXType_Int128 => TypeKind::Int(IntKind::I128),
+            CXType_UInt128 => TypeKind::Int(IntKind::U128),
+            CXType_Float16 | CXType_Half => TypeKind::Float(FloatKind::Float16),
+            CXType_Float => TypeKind::Float(FloatKind::Float),
+            CXType_Double => TypeKind::Float(FloatKind::Double),
+            CXType_LongDouble => TypeKind::Float(FloatKind::LongDouble),
+            CXType_Float128 => TypeKind::Float(FloatKind::Float128),
+            CXType_Complex => {
+                let float_type =
+                    ty.elem_type().expect("Not able to resolve complex type?");
+                let float_kind = match float_type.kind() {
+                    CXType_Float16 | CXType_Half => FloatKind::Float16,
+                    CXType_Float => FloatKind::Float,
+                    CXType_Double => FloatKind::Double,
+                    CXType_LongDouble => FloatKind::LongDouble,
+                    CXType_Float128 => FloatKind::Float128,
+                    _ => panic!(
+                        "Non floating-type complex? {:?}, {:?}",
+                        ty, float_type,
+                    ),
+                };
+                TypeKind::Complex(float_kind)
+            }
+            _ => return None,
+        };
+
+        let spelling = ty.spelling();
+        let is_const = ty.is_const();
+        let layout = ty.fallible_layout(self).ok();
+        let location = ty.declaration().location();
+        let ty = Type::new(Some(spelling), layout, type_kind, is_const);
+        let id = self.next_item_id();
+        let item = Item::new(
+            id,
+            None,
+            None,
+            self.root_module.into(),
+            ItemKind::Type(ty),
+            Some(location),
+        );
+        self.add_builtin_item(item);
+        Some(id.as_type_id_unchecked())
+    }
+
+    /// Get the current Clang translation unit that is being processed.
+    pub(crate) fn translation_unit(&self) -> &clang::TranslationUnit {
+        &self.translation_unit
+    }
+
+    /// Have we parsed the macro named `macro_name` already?
+    pub(crate) fn parsed_macro(&self, macro_name: &[u8]) -> bool {
+        self.parsed_macros.contains_key(macro_name)
+    }
+
+    /// Get the currently parsed macros.
+    pub(crate) fn parsed_macros(
+        &self,
+    ) -> &StdHashMap<Vec<u8>, cexpr::expr::EvalResult> {
+        debug_assert!(!self.in_codegen_phase());
+        &self.parsed_macros
+    }
+
+    /// Mark the macro named `macro_name` as parsed.
+    pub(crate) fn note_parsed_macro(
+        &mut self,
+        id: Vec<u8>,
+        value: cexpr::expr::EvalResult,
+    ) {
+        self.parsed_macros.insert(id, value);
+    }
+
+    /// Are we in the codegen phase?
+    pub(crate) fn in_codegen_phase(&self) -> bool {
+        self.in_codegen
+    }
+
+    /// Mark the type with the given `name` as replaced by the type with ID
+    /// `potential_ty`.
+    ///
+    /// Replacement types are declared using the `replaces="xxx"` annotation,
+    /// and implies that the original type is hidden.
+    pub(crate) fn replace(&mut self, name: &[String], potential_ty: ItemId) {
+        match self.replacements.entry(name.into()) {
+            Entry::Vacant(entry) => {
+                debug!(
+                    "Defining replacement for {:?} as {:?}",
+                    name, potential_ty
+                );
+                entry.insert(potential_ty);
+            }
+            Entry::Occupied(occupied) => {
+                warn!(
+                    "Replacement for {:?} already defined as {:?}; \
+                     ignoring duplicate replacement definition as {:?}",
+                    name,
+                    occupied.get(),
+                    potential_ty
+                );
+            }
+        }
+    }
+
+    /// Has the item with the given `name` and `id` been replaced by another
+    /// type?
+    pub(crate) fn is_replaced_type<Id: Into<ItemId>>(
+        &self,
+        path: &[String],
+        id: Id,
+    ) -> bool {
+        let id = id.into();
+        matches!(self.replacements.get(path), Some(replaced_by) if *replaced_by != id)
+    }
+
+    /// Is the type with the given `name` marked as opaque?
+    pub(crate) fn opaque_by_name(&self, path: &[String]) -> bool {
+        debug_assert!(
+            self.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        self.options.opaque_types.matches(path[1..].join("::"))
+    }
+
+    /// Get the options used to configure this bindgen context.
+    pub(crate) fn options(&self) -> &BindgenOptions {
+        &self.options
+    }
+
+    /// Tokenizes a namespace cursor in order to get the name and kind of the
+    /// namespace.
+    fn tokenize_namespace(
+        &self,
+        cursor: &clang::Cursor,
+    ) -> (Option<String>, ModuleKind) {
+        assert_eq!(
+            cursor.kind(),
+            ::clang_sys::CXCursor_Namespace,
+            "Be a nice person"
+        );
+
+        let mut module_name = None;
+        let spelling = cursor.spelling();
+        if !spelling.is_empty() {
+            module_name = Some(spelling)
+        }
+
+        let mut kind = ModuleKind::Normal;
+        let mut looking_for_name = false;
+        for token in cursor.tokens().iter() {
+            match token.spelling() {
+                b"inline" => {
+                    debug_assert!(
+                        kind != ModuleKind::Inline,
+                        "Multiple inline keywords?"
+                    );
+                    kind = ModuleKind::Inline;
+                    // When hitting a nested inline namespace we get a spelling
+                    // that looks like ["inline", "foo"]. Deal with it properly.
+                    looking_for_name = true;
+                }
+                // The double colon allows us to handle nested namespaces like
+                // namespace foo::bar { }
+                //
+                // libclang still gives us two namespace cursors, which is cool,
+                // but the tokenization of the second begins with the double
+                // colon. That's ok, so we only need to handle the weird
+                // tokenization here.
+                b"namespace" | b"::" => {
+                    looking_for_name = true;
+                }
+                b"{" => {
+                    // This should be an anonymous namespace.
+                    assert!(looking_for_name);
+                    break;
+                }
+                name => {
+                    if looking_for_name {
+                        if module_name.is_none() {
+                            module_name = Some(
+                                String::from_utf8_lossy(name).into_owned(),
+                            );
+                        }
+                        break;
+                    } else {
+                        // This is _likely_, but not certainly, a macro that's
+                        // been placed just before the namespace keyword.
+                        // Unfortunately, clang tokens don't let us easily see
+                        // through the ifdef tokens, so we don't know what this
+                        // token should really be. Instead of panicking though,
+                        // we warn the user that we assumed the token was blank,
+                        // and then move on.
+                        //
+                        // See also https://github.com/rust-lang/rust-bindgen/issues/1676.
+                        warn!(
+                            "Ignored unknown namespace prefix '{}' at {:?} in {:?}",
+                            String::from_utf8_lossy(name),
+                            token,
+                            cursor
+                        );
+                    }
+                }
+            }
+        }
+
+        (module_name, kind)
+    }
+
+    /// Given a CXCursor_Namespace cursor, return the item ID of the
+    /// corresponding module, or create one on the fly.
+    pub(crate) fn module(&mut self, cursor: clang::Cursor) -> ModuleId {
+        use clang_sys::*;
+        assert_eq!(cursor.kind(), CXCursor_Namespace, "Be a nice person");
+        let cursor = cursor.canonical();
+        if let Some(id) = self.modules.get(&cursor) {
+            return *id;
+        }
+
+        let (module_name, kind) = self.tokenize_namespace(&cursor);
+
+        let module_id = self.next_item_id();
+        let module = Module::new(module_name, kind);
+        let module = Item::new(
+            module_id,
+            None,
+            None,
+            self.current_module.into(),
+            ItemKind::Module(module),
+            Some(cursor.location()),
+        );
+
+        let module_id = module.id().as_module_id_unchecked();
+        self.modules.insert(cursor, module_id);
+
+        self.add_item(module, None, None);
+
+        module_id
+    }
+
+    /// Start traversing the module with the given `module_id`, invoke the
+    /// callback `cb`, and then return to traversing the original module.
+    pub(crate) fn with_module<F>(&mut self, module_id: ModuleId, cb: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        debug_assert!(self.resolve_item(module_id).kind().is_module(), "Wat");
+
+        let previous_id = self.current_module;
+        self.current_module = module_id;
+
+        cb(self);
+
+        self.current_module = previous_id;
+    }
+
+    /// Iterate over all (explicitly or transitively) allowlisted items.
+    ///
+    /// If no items are explicitly allowlisted, then all items are considered
+    /// allowlisted.
+    pub(crate) fn allowlisted_items(&self) -> &ItemSet {
+        assert!(self.in_codegen_phase());
+        assert!(self.current_module == self.root_module);
+
+        self.allowlisted.as_ref().unwrap()
+    }
+
+    /// Check whether a particular blocklisted type implements a trait or not.
+    /// Results may be cached.
+    pub(crate) fn blocklisted_type_implements_trait(
+        &self,
+        item: &Item,
+        derive_trait: DeriveTrait,
+    ) -> CanDerive {
+        assert!(self.in_codegen_phase());
+        assert!(self.current_module == self.root_module);
+
+        *self
+            .blocklisted_types_implement_traits
+            .borrow_mut()
+            .entry(derive_trait)
+            .or_default()
+            .entry(item.id())
+            .or_insert_with(|| {
+                item.expect_type()
+                    .name()
+                    .and_then(|name| {
+                        if self.options.parse_callbacks.is_empty() {
+                            // Sized integer types from <stdint.h> get mapped to Rust primitive
+                            // types regardless of whether they are blocklisted, so ensure that
+                            // standard traits are considered derivable for them too.
+                            if self.is_stdint_type(name) {
+                                Some(CanDerive::Yes)
+                            } else {
+                                Some(CanDerive::No)
+                            }
+                        } else {
+                            self.options.last_callback(|cb| {
+                                cb.blocklisted_type_implements_trait(
+                                    name,
+                                    derive_trait,
+                                )
+                            })
+                        }
+                    })
+                    .unwrap_or(CanDerive::No)
+            })
+    }
+
+    /// Is the given type a type from <stdint.h> that corresponds to a Rust primitive type?
+    pub(crate) fn is_stdint_type(&self, name: &str) -> bool {
+        match name {
+            "int8_t" | "uint8_t" | "int16_t" | "uint16_t" | "int32_t" |
+            "uint32_t" | "int64_t" | "uint64_t" | "uintptr_t" |
+            "intptr_t" | "ptrdiff_t" => true,
+            "size_t" | "ssize_t" => self.options.size_t_is_usize,
+            _ => false,
+        }
+    }
+
+    /// Get a reference to the set of items we should generate.
+    pub(crate) fn codegen_items(&self) -> &ItemSet {
+        assert!(self.in_codegen_phase());
+        assert!(self.current_module == self.root_module);
+        self.codegen_items.as_ref().unwrap()
+    }
+
+    /// Compute the allowlisted items set and populate `self.allowlisted`.
+    fn compute_allowlisted_and_codegen_items(&mut self) {
+        assert!(self.in_codegen_phase());
+        assert!(self.current_module == self.root_module);
+        assert!(self.allowlisted.is_none());
+        let _t = self.timer("compute_allowlisted_and_codegen_items");
+
+        let roots = {
+            let mut roots = self
+                .items()
+                // Only consider roots that are enabled for codegen.
+                .filter(|&(_, item)| item.is_enabled_for_codegen(self))
+                .filter(|&(_, item)| {
+                    // If nothing is explicitly allowlisted, then everything is fair
+                    // game.
+                    if self.options().allowlisted_types.is_empty() &&
+                        self.options().allowlisted_functions.is_empty() &&
+                        self.options().allowlisted_vars.is_empty() &&
+                        self.options().allowlisted_files.is_empty() &&
+                        self.options().allowlisted_items.is_empty()
+                    {
+                        return true;
+                    }
+
+                    // If this is a type that explicitly replaces another, we assume
+                    // you know what you're doing.
+                    if item.annotations().use_instead_of().is_some() {
+                        return true;
+                    }
+
+                    // Items with a source location in an explicitly allowlisted file
+                    // are always included.
+                    if !self.options().allowlisted_files.is_empty() {
+                        if let Some(location) = item.location() {
+                            let (file, _, _, _) = location.location();
+                            if let Some(filename) = file.name() {
+                                if self
+                                    .options()
+                                    .allowlisted_files
+                                    .matches(filename)
+                                {
+                                    return true;
+                                }
+                            }
+                        }
+                    }
+
+                    let name = item.path_for_allowlisting(self)[1..].join("::");
+                    debug!("allowlisted_items: testing {:?}", name);
+
+                    if self.options().allowlisted_items.matches(&name) {
+                        return true;
+                    }
+
+                    match *item.kind() {
+                        ItemKind::Module(..) => true,
+                        ItemKind::Function(_) => {
+                            self.options().allowlisted_functions.matches(&name)
+                        }
+                        ItemKind::Var(_) => {
+                            self.options().allowlisted_vars.matches(&name)
+                        }
+                        ItemKind::Type(ref ty) => {
+                            if self.options().allowlisted_types.matches(&name) {
+                                return true;
+                            }
+
+                            // Auto-allowlist types that don't need code
+                            // generation if not allowlisting recursively, to
+                            // make the #[derive] analysis not be lame.
+                            if !self.options().allowlist_recursively {
+                                match *ty.kind() {
+                                    TypeKind::Void |
+                                    TypeKind::NullPtr |
+                                    TypeKind::Int(..) |
+                                    TypeKind::Float(..) |
+                                    TypeKind::Complex(..) |
+                                    TypeKind::Array(..) |
+                                    TypeKind::Vector(..) |
+                                    TypeKind::Pointer(..) |
+                                    TypeKind::Reference(..) |
+                                    TypeKind::Function(..) |
+                                    TypeKind::ResolvedTypeRef(..) |
+                                    TypeKind::Opaque |
+                                    TypeKind::TypeParam => return true,
+                                    _ => {}
+                                }
+                                if self.is_stdint_type(&name) {
+                                    return true;
+                                }
+                            }
+
+                            // Unnamed top-level enums are special and we
+                            // allowlist them via the `allowlisted_vars` filter,
+                            // since they're effectively top-level constants,
+                            // and there's no way for them to be referenced
+                            // consistently.
+                            let parent = self.resolve_item(item.parent_id());
+                            if !parent.is_module() {
+                                return false;
+                            }
+
+                            let enum_ = match *ty.kind() {
+                                TypeKind::Enum(ref e) => e,
+                                _ => return false,
+                            };
+
+                            if ty.name().is_some() {
+                                return false;
+                            }
+
+                            let mut prefix_path =
+                                parent.path_for_allowlisting(self).clone();
+                            enum_.variants().iter().any(|variant| {
+                                prefix_path.push(
+                                    variant.name_for_allowlisting().into(),
+                                );
+                                let name = prefix_path[1..].join("::");
+                                prefix_path.pop().unwrap();
+                                self.options().allowlisted_vars.matches(name)
+                            })
+                        }
+                    }
+                })
+                .map(|(id, _)| id)
+                .collect::<Vec<_>>();
+
+            // The reversal preserves the expected ordering of traversal,
+            // resulting in more stable-ish bindgen-generated names for
+            // anonymous types (like unions).
+            roots.reverse();
+            roots
+        };
+
+        let allowlisted_items_predicate =
+            if self.options().allowlist_recursively {
+                traversal::all_edges
+            } else {
+                // Only follow InnerType edges from the allowlisted roots.
+                // Such inner types (e.g. anonymous structs/unions) are
+                // always emitted by codegen, and they need to be allowlisted
+                // to make sure they are processed by e.g. the derive analysis.
+                traversal::only_inner_type_edges
+            };
+
+        let allowlisted = AllowlistedItemsTraversal::new(
+            self,
+            roots.clone(),
+            allowlisted_items_predicate,
+        )
+        .collect::<ItemSet>();
+
+        let codegen_items = if self.options().allowlist_recursively {
+            AllowlistedItemsTraversal::new(
+                self,
+                roots,
+                traversal::codegen_edges,
+            )
+            .collect::<ItemSet>()
+        } else {
+            allowlisted.clone()
+        };
+
+        self.allowlisted = Some(allowlisted);
+        self.codegen_items = Some(codegen_items);
+
+        for item in self.options().allowlisted_functions.unmatched_items() {
+            unused_regex_diagnostic(item, "--allowlist-function", self);
+        }
+
+        for item in self.options().allowlisted_vars.unmatched_items() {
+            unused_regex_diagnostic(item, "--allowlist-var", self);
+        }
+
+        for item in self.options().allowlisted_types.unmatched_items() {
+            unused_regex_diagnostic(item, "--allowlist-type", self);
+        }
+
+        for item in self.options().allowlisted_items.unmatched_items() {
+            unused_regex_diagnostic(item, "--allowlist-items", self);
+        }
+    }
+
+    /// Convenient method for getting the prefix to use for most traits in
+    /// codegen depending on the `use_core` option.
+    pub(crate) fn trait_prefix(&self) -> Ident {
+        if self.options().use_core {
+            self.rust_ident_raw("core")
+        } else {
+            self.rust_ident_raw("std")
+        }
+    }
+
+    /// Call if a bindgen complex is generated
+    pub(crate) fn generated_bindgen_complex(&self) {
+        self.generated_bindgen_complex.set(true)
+    }
+
+    /// Whether we need to generate the bindgen complex type
+    pub(crate) fn need_bindgen_complex_type(&self) -> bool {
+        self.generated_bindgen_complex.get()
+    }
+
+    /// Call if a bindgen float16 is generated
+    pub(crate) fn generated_bindgen_float16(&self) {
+        self.generated_bindgen_float16.set(true)
+    }
+
+    /// Whether we need to generate the bindgen float16 type
+    pub(crate) fn need_bindgen_float16_type(&self) -> bool {
+        self.generated_bindgen_float16.get()
+    }
+
+    /// Compute which `enum`s have an associated `typedef` definition.
+    fn compute_enum_typedef_combos(&mut self) {
+        let _t = self.timer("compute_enum_typedef_combos");
+        assert!(self.enum_typedef_combos.is_none());
+
+        let mut enum_typedef_combos = HashSet::default();
+        for item in &self.items {
+            if let Some(ItemKind::Module(module)) =
+                item.as_ref().map(Item::kind)
+            {
+                // Find typedefs in this module, and build set of their names.
+                let mut names_of_typedefs = HashSet::default();
+                for child_id in module.children() {
+                    if let Some(ItemKind::Type(ty)) =
+                        self.items[child_id.0].as_ref().map(Item::kind)
+                    {
+                        if let (Some(name), TypeKind::Alias(type_id)) =
+                            (ty.name(), ty.kind())
+                        {
+                            // We disregard aliases that refer to the enum
+                            // itself, such as in `typedef enum { ... } Enum;`.
+                            if type_id
+                                .into_resolver()
+                                .through_type_refs()
+                                .through_type_aliases()
+                                .resolve(self)
+                                .expect_type()
+                                .is_int()
+                            {
+                                names_of_typedefs.insert(name);
+                            }
+                        }
+                    }
+                }
+
+                // Find enums in this module, and record the ID of each one that
+                // has a typedef.
+                for child_id in module.children() {
+                    if let Some(ItemKind::Type(ty)) =
+                        self.items[child_id.0].as_ref().map(Item::kind)
+                    {
+                        if let (Some(name), true) = (ty.name(), ty.is_enum()) {
+                            if names_of_typedefs.contains(name) {
+                                enum_typedef_combos.insert(*child_id);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        self.enum_typedef_combos = Some(enum_typedef_combos);
+    }
+
+    /// Look up whether `id` refers to an `enum` whose underlying type is
+    /// defined by a `typedef`.
+    pub(crate) fn is_enum_typedef_combo(&self, id: ItemId) -> bool {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute enum_typedef_combos when we enter codegen",
+        );
+        self.enum_typedef_combos.as_ref().unwrap().contains(&id)
+    }
+
+    /// Compute whether we can derive debug.
+    fn compute_cannot_derive_debug(&mut self) {
+        let _t = self.timer("compute_cannot_derive_debug");
+        assert!(self.cannot_derive_debug.is_none());
+        if self.options.derive_debug {
+            self.cannot_derive_debug =
+                Some(as_cannot_derive_set(analyze::<CannotDerive>((
+                    self,
+                    DeriveTrait::Debug,
+                ))));
+        }
+    }
+
+    /// Look up whether the item with `id` can
+    /// derive debug or not.
+    pub(crate) fn lookup_can_derive_debug<Id: Into<ItemId>>(
+        &self,
+        id: Id,
+    ) -> bool {
+        let id = id.into();
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute can_derive_debug when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` can
+        // derive debug or not.
+        !self.cannot_derive_debug.as_ref().unwrap().contains(&id)
+    }
+
+    /// Compute whether we can derive default.
+    fn compute_cannot_derive_default(&mut self) {
+        let _t = self.timer("compute_cannot_derive_default");
+        assert!(self.cannot_derive_default.is_none());
+        if self.options.derive_default {
+            self.cannot_derive_default =
+                Some(as_cannot_derive_set(analyze::<CannotDerive>((
+                    self,
+                    DeriveTrait::Default,
+                ))));
+        }
+    }
+
+    /// Look up whether the item with `id` can
+    /// derive default or not.
+    pub(crate) fn lookup_can_derive_default<Id: Into<ItemId>>(
+        &self,
+        id: Id,
+    ) -> bool {
+        let id = id.into();
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute can_derive_default when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` can
+        // derive default or not.
+        !self.cannot_derive_default.as_ref().unwrap().contains(&id)
+    }
+
+    /// Compute whether we can derive copy.
+    fn compute_cannot_derive_copy(&mut self) {
+        let _t = self.timer("compute_cannot_derive_copy");
+        assert!(self.cannot_derive_copy.is_none());
+        self.cannot_derive_copy =
+            Some(as_cannot_derive_set(analyze::<CannotDerive>((
+                self,
+                DeriveTrait::Copy,
+            ))));
+    }
+
+    /// Compute whether we can derive hash.
+    fn compute_cannot_derive_hash(&mut self) {
+        let _t = self.timer("compute_cannot_derive_hash");
+        assert!(self.cannot_derive_hash.is_none());
+        if self.options.derive_hash {
+            self.cannot_derive_hash =
+                Some(as_cannot_derive_set(analyze::<CannotDerive>((
+                    self,
+                    DeriveTrait::Hash,
+                ))));
+        }
+    }
+
+    /// Look up whether the item with `id` can
+    /// derive hash or not.
+    pub(crate) fn lookup_can_derive_hash<Id: Into<ItemId>>(
+        &self,
+        id: Id,
+    ) -> bool {
+        let id = id.into();
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute can_derive_debug when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` can
+        // derive hash or not.
+        !self.cannot_derive_hash.as_ref().unwrap().contains(&id)
+    }
+
+    /// Compute whether we can derive PartialOrd, PartialEq or Eq.
+    fn compute_cannot_derive_partialord_partialeq_or_eq(&mut self) {
+        let _t = self.timer("compute_cannot_derive_partialord_partialeq_or_eq");
+        assert!(self.cannot_derive_partialeq_or_partialord.is_none());
+        if self.options.derive_partialord ||
+            self.options.derive_partialeq ||
+            self.options.derive_eq
+        {
+            self.cannot_derive_partialeq_or_partialord =
+                Some(analyze::<CannotDerive>((
+                    self,
+                    DeriveTrait::PartialEqOrPartialOrd,
+                )));
+        }
+    }
+
+    /// Look up whether the item with `id` can derive `Partial{Eq,Ord}`.
+    pub(crate) fn lookup_can_derive_partialeq_or_partialord<
+        Id: Into<ItemId>,
+    >(
+        &self,
+        id: Id,
+    ) -> CanDerive {
+        let id = id.into();
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute can_derive_partialeq_or_partialord when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` can
+        // derive partialeq or not.
+        self.cannot_derive_partialeq_or_partialord
+            .as_ref()
+            .unwrap()
+            .get(&id)
+            .cloned()
+            .unwrap_or(CanDerive::Yes)
+    }
+
+    /// Look up whether the item with `id` can derive `Copy` or not.
+    pub(crate) fn lookup_can_derive_copy<Id: Into<ItemId>>(
+        &self,
+        id: Id,
+    ) -> bool {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute can_derive_debug when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` can
+        // derive `Copy` or not.
+        let id = id.into();
+
+        !self.lookup_has_type_param_in_array(id) &&
+            !self.cannot_derive_copy.as_ref().unwrap().contains(&id)
+    }
+
+    /// Compute whether the type has type parameter in array.
+    fn compute_has_type_param_in_array(&mut self) {
+        let _t = self.timer("compute_has_type_param_in_array");
+        assert!(self.has_type_param_in_array.is_none());
+        self.has_type_param_in_array =
+            Some(analyze::<HasTypeParameterInArray>(self));
+    }
+
+    /// Look up whether the item with `id` has type parameter in array or not.
+    pub(crate) fn lookup_has_type_param_in_array<Id: Into<ItemId>>(
+        &self,
+        id: Id,
+    ) -> bool {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute has array when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` has
+        // type parameter in array or not.
+        self.has_type_param_in_array
+            .as_ref()
+            .unwrap()
+            .contains(&id.into())
+    }
+
+    /// Compute whether the type has float.
+    fn compute_has_float(&mut self) {
+        let _t = self.timer("compute_has_float");
+        assert!(self.has_float.is_none());
+        if self.options.derive_eq || self.options.derive_ord {
+            self.has_float = Some(analyze::<HasFloat>(self));
+        }
+    }
+
+    /// Look up whether the item with `id` has array or not.
+    pub(crate) fn lookup_has_float<Id: Into<ItemId>>(&self, id: Id) -> bool {
+        assert!(
+            self.in_codegen_phase(),
+            "We only compute has float when we enter codegen"
+        );
+
+        // Look up the computed value for whether the item with `id` has
+        // float or not.
+        self.has_float.as_ref().unwrap().contains(&id.into())
+    }
+
+    /// Check if `--no-partialeq` flag is enabled for this item.
+    pub(crate) fn no_partialeq_by_name(&self, item: &Item) -> bool {
+        let name = item.path_for_allowlisting(self)[1..].join("::");
+        self.options().no_partialeq_types.matches(name)
+    }
+
+    /// Check if `--no-copy` flag is enabled for this item.
+    pub(crate) fn no_copy_by_name(&self, item: &Item) -> bool {
+        let name = item.path_for_allowlisting(self)[1..].join("::");
+        self.options().no_copy_types.matches(name)
+    }
+
+    /// Check if `--no-debug` flag is enabled for this item.
+    pub(crate) fn no_debug_by_name(&self, item: &Item) -> bool {
+        let name = item.path_for_allowlisting(self)[1..].join("::");
+        self.options().no_debug_types.matches(name)
+    }
+
+    /// Check if `--no-default` flag is enabled for this item.
+    pub(crate) fn no_default_by_name(&self, item: &Item) -> bool {
+        let name = item.path_for_allowlisting(self)[1..].join("::");
+        self.options().no_default_types.matches(name)
+    }
+
+    /// Check if `--no-hash` flag is enabled for this item.
+    pub(crate) fn no_hash_by_name(&self, item: &Item) -> bool {
+        let name = item.path_for_allowlisting(self)[1..].join("::");
+        self.options().no_hash_types.matches(name)
+    }
+
+    /// Check if `--must-use-type` flag is enabled for this item.
+    pub(crate) fn must_use_type_by_name(&self, item: &Item) -> bool {
+        let name = item.path_for_allowlisting(self)[1..].join("::");
+        self.options().must_use_types.matches(name)
+    }
+
+    /// Wrap some tokens in an `unsafe` block if the `--wrap-unsafe-ops` option is enabled.
+    pub(crate) fn wrap_unsafe_ops(&self, tokens: impl ToTokens) -> TokenStream {
+        if self.options.wrap_unsafe_ops {
+            quote!(unsafe { #tokens })
+        } else {
+            tokens.into_token_stream()
+        }
+    }
+
+    /// Get the suffix to be added to `static` functions if the `--wrap-static-fns` option is
+    /// enabled.
+    pub(crate) fn wrap_static_fns_suffix(&self) -> &str {
+        self.options()
+            .wrap_static_fns_suffix
+            .as_deref()
+            .unwrap_or(crate::DEFAULT_NON_EXTERN_FNS_SUFFIX)
+    }
+}
+
+/// A builder struct for configuring item resolution options.
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct ItemResolver {
+    id: ItemId,
+    through_type_refs: bool,
+    through_type_aliases: bool,
+}
+
+impl ItemId {
+    /// Create an `ItemResolver` from this item ID.
+    pub(crate) fn into_resolver(self) -> ItemResolver {
+        self.into()
+    }
+}
+
+impl<T> From<T> for ItemResolver
+where
+    T: Into<ItemId>,
+{
+    fn from(id: T) -> ItemResolver {
+        ItemResolver::new(id)
+    }
+}
+
+impl ItemResolver {
+    /// Construct a new `ItemResolver` from the given ID.
+    pub(crate) fn new<Id: Into<ItemId>>(id: Id) -> ItemResolver {
+        let id = id.into();
+        ItemResolver {
+            id,
+            through_type_refs: false,
+            through_type_aliases: false,
+        }
+    }
+
+    /// Keep resolving through `Type::TypeRef` items.
+    pub(crate) fn through_type_refs(mut self) -> ItemResolver {
+        self.through_type_refs = true;
+        self
+    }
+
+    /// Keep resolving through `Type::Alias` items.
+    pub(crate) fn through_type_aliases(mut self) -> ItemResolver {
+        self.through_type_aliases = true;
+        self
+    }
+
+    /// Finish configuring and perform the actual item resolution.
+    pub(crate) fn resolve(self, ctx: &BindgenContext) -> &Item {
+        assert!(ctx.collected_typerefs());
+
+        let mut id = self.id;
+        let mut seen_ids = HashSet::default();
+        loop {
+            let item = ctx.resolve_item(id);
+
+            // Detect cycles and bail out. These can happen in certain cases
+            // involving incomplete qualified dependent types (#2085).
+            if !seen_ids.insert(id) {
+                return item;
+            }
+
+            let ty_kind = item.as_type().map(|t| t.kind());
+            match ty_kind {
+                Some(&TypeKind::ResolvedTypeRef(next_id))
+                    if self.through_type_refs =>
+                {
+                    id = next_id.into();
+                }
+                // We intentionally ignore template aliases here, as they are
+                // more complicated, and don't represent a simple renaming of
+                // some type.
+                Some(&TypeKind::Alias(next_id))
+                    if self.through_type_aliases =>
+                {
+                    id = next_id.into();
+                }
+                _ => return item,
+            }
+        }
+    }
+}
+
+/// A type that we are in the middle of parsing.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) struct PartialType {
+    decl: Cursor,
+    // Just an ItemId, and not a TypeId, because we haven't finished this type
+    // yet, so there's still time for things to go wrong.
+    id: ItemId,
+}
+
+impl PartialType {
+    /// Construct a new `PartialType`.
+    pub(crate) fn new(decl: Cursor, id: ItemId) -> PartialType {
+        // assert!(decl == decl.canonical());
+        PartialType { decl, id }
+    }
+
+    /// The cursor pointing to this partial type's declaration location.
+    pub(crate) fn decl(&self) -> &Cursor {
+        &self.decl
+    }
+
+    /// The item ID allocated for this type. This is *NOT* a key for an entry in
+    /// the context's item set yet!
+    pub(crate) fn id(&self) -> ItemId {
+        self.id
+    }
+}
+
+impl TemplateParameters for PartialType {
+    fn self_template_params(&self, _ctx: &BindgenContext) -> Vec<TypeId> {
+        // Maybe at some point we will eagerly parse named types, but for now we
+        // don't and this information is unavailable.
+        vec![]
+    }
+
+    fn num_self_template_params(&self, _ctx: &BindgenContext) -> usize {
+        // Wouldn't it be nice if libclang would reliably give us this
+        // information‽
+        match self.decl().kind() {
+            clang_sys::CXCursor_ClassTemplate |
+            clang_sys::CXCursor_FunctionTemplate |
+            clang_sys::CXCursor_TypeAliasTemplateDecl => {
+                let mut num_params = 0;
+                self.decl().visit(|c| {
+                    match c.kind() {
+                        clang_sys::CXCursor_TemplateTypeParameter |
+                        clang_sys::CXCursor_TemplateTemplateParameter |
+                        clang_sys::CXCursor_NonTypeTemplateParameter => {
+                            num_params += 1;
+                        }
+                        _ => {}
+                    };
+                    clang_sys::CXChildVisit_Continue
+                });
+                num_params
+            }
+            _ => 0,
+        }
+    }
+}
+
+fn unused_regex_diagnostic(item: &str, name: &str, _ctx: &BindgenContext) {
+    warn!("unused option: {} {}", name, item);
+
+    #[cfg(feature = "experimental")]
+    if _ctx.options().emit_diagnostics {
+        use crate::diagnostics::{Diagnostic, Level};
+
+        Diagnostic::default()
+            .with_title(
+                format!("Unused regular expression: `{}`.", item),
+                Level::Warn,
+            )
+            .add_annotation(
+                format!("This regular expression was passed to `{}`.", name),
+                Level::Note,
+            )
+            .display();
+    }
+}
diff --git a/third_party/rust/bindgen/ir/derive.rs b/third_party/rust/bindgen/ir/derive.rs
new file mode 100644
index 0000000000..3877b42f8f
--- /dev/null
+++ b/third_party/rust/bindgen/ir/derive.rs
@@ -0,0 +1,135 @@
+//! Traits for determining whether we can derive traits for a thing or not.
+//!
+//! These traits tend to come in pairs:
+//!
+//! 1. A "trivial" version, whose implementations aren't allowed to recursively
+//! look at other types or the results of fix point analyses.
+//!
+//! 2. A "normal" version, whose implementations simply query the results of a
+//! fix point analysis.
+//!
+//! The former is used by the analyses when creating the results queried by the
+//! second.
+
+use super::context::BindgenContext;
+
+use std::cmp;
+use std::ops;
+
+/// A trait that encapsulates the logic for whether or not we can derive `Debug`
+/// for a given thing.
+pub(crate) trait CanDeriveDebug {
+    /// Return `true` if `Debug` can be derived for this thing, `false`
+    /// otherwise.
+    fn can_derive_debug(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait that encapsulates the logic for whether or not we can derive `Copy`
+/// for a given thing.
+pub(crate) trait CanDeriveCopy {
+    /// Return `true` if `Copy` can be derived for this thing, `false`
+    /// otherwise.
+    fn can_derive_copy(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait that encapsulates the logic for whether or not we can derive
+/// `Default` for a given thing.
+pub(crate) trait CanDeriveDefault {
+    /// Return `true` if `Default` can be derived for this thing, `false`
+    /// otherwise.
+    fn can_derive_default(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait that encapsulates the logic for whether or not we can derive `Hash`
+/// for a given thing.
+pub(crate) trait CanDeriveHash {
+    /// Return `true` if `Hash` can be derived for this thing, `false`
+    /// otherwise.
+    fn can_derive_hash(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait that encapsulates the logic for whether or not we can derive
+/// `PartialEq` for a given thing.
+pub(crate) trait CanDerivePartialEq {
+    /// Return `true` if `PartialEq` can be derived for this thing, `false`
+    /// otherwise.
+    fn can_derive_partialeq(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait that encapsulates the logic for whether or not we can derive
+/// `PartialOrd` for a given thing.
+pub(crate) trait CanDerivePartialOrd {
+    /// Return `true` if `PartialOrd` can be derived for this thing, `false`
+    /// otherwise.
+    fn can_derive_partialord(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait that encapsulates the logic for whether or not we can derive `Eq`
+/// for a given thing.
+pub(crate) trait CanDeriveEq {
+    /// Return `true` if `Eq` can be derived for this thing, `false` otherwise.
+    fn can_derive_eq(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait that encapsulates the logic for whether or not we can derive `Ord`
+/// for a given thing.
+pub(crate) trait CanDeriveOrd {
+    /// Return `true` if `Ord` can be derived for this thing, `false` otherwise.
+    fn can_derive_ord(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// Whether it is possible or not to automatically derive trait for an item.
+///
+/// ```ignore
+///         No
+///          ^
+///          |
+///      Manually
+///          ^
+///          |
+///         Yes
+/// ```
+///
+/// Initially we assume that we can derive trait for all types and then
+/// update our understanding as we learn more about each type.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub enum CanDerive {
+    /// Yes, we can derive automatically.
+    Yes,
+
+    /// The only thing that stops us from automatically deriving is that
+    /// array with more than maximum number of elements is used.
+    ///
+    /// This means we probably can "manually" implement such trait.
+    Manually,
+
+    /// No, we cannot.
+    No,
+}
+
+impl Default for CanDerive {
+    fn default() -> CanDerive {
+        CanDerive::Yes
+    }
+}
+
+impl CanDerive {
+    /// Take the least upper bound of `self` and `rhs`.
+    pub(crate) fn join(self, rhs: Self) -> Self {
+        cmp::max(self, rhs)
+    }
+}
+
+impl ops::BitOr for CanDerive {
+    type Output = Self;
+
+    fn bitor(self, rhs: Self) -> Self::Output {
+        self.join(rhs)
+    }
+}
+
+impl ops::BitOrAssign for CanDerive {
+    fn bitor_assign(&mut self, rhs: Self) {
+        *self = self.join(rhs)
+    }
+}
diff --git a/third_party/rust/bindgen/ir/dot.rs b/third_party/rust/bindgen/ir/dot.rs
new file mode 100644
index 0000000000..d5c1a42fdc
--- /dev/null
+++ b/third_party/rust/bindgen/ir/dot.rs
@@ -0,0 +1,86 @@
+//! Generating Graphviz `dot` files from our IR.
+
+use super::context::{BindgenContext, ItemId};
+use super::traversal::Trace;
+use std::fs::File;
+use std::io::{self, Write};
+use std::path::Path;
+
+/// A trait for anything that can write attributes as `<table>` rows to a dot
+/// file.
+pub(crate) trait DotAttributes {
+    /// Write this thing's attributes to the given output. Each attribute must
+    /// be its own `<tr>...</tr>`.
+    fn dot_attributes<W>(
+        &self,
+        ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write;
+}
+
+/// Write a graphviz dot file containing our IR.
+pub(crate) fn write_dot_file<P>(ctx: &BindgenContext, path: P) -> io::Result<()>
+where
+    P: AsRef<Path>,
+{
+    let file = File::create(path)?;
+    let mut dot_file = io::BufWriter::new(file);
+    writeln!(&mut dot_file, "digraph {{")?;
+
+    let mut err: Option<io::Result<_>> = None;
+
+    for (id, item) in ctx.items() {
+        let is_allowlisted = ctx.allowlisted_items().contains(&id);
+
+        writeln!(
+            &mut dot_file,
+            r#"{} [fontname="courier", color={}, label=< <table border="0" align="left">"#,
+            id.as_usize(),
+            if is_allowlisted { "black" } else { "gray" }
+        )?;
+        item.dot_attributes(ctx, &mut dot_file)?;
+        writeln!(&mut dot_file, r#"</table> >];"#)?;
+
+        item.trace(
+            ctx,
+            &mut |sub_id: ItemId, edge_kind| {
+                if err.is_some() {
+                    return;
+                }
+
+                match writeln!(
+                    &mut dot_file,
+                    "{} -> {} [label={:?}, color={}];",
+                    id.as_usize(),
+                    sub_id.as_usize(),
+                    edge_kind,
+                    if is_allowlisted { "black" } else { "gray" }
+                ) {
+                    Ok(_) => {}
+                    Err(e) => err = Some(Err(e)),
+                }
+            },
+            &(),
+        );
+
+        if let Some(err) = err {
+            return err;
+        }
+
+        if let Some(module) = item.as_module() {
+            for child in module.children() {
+                writeln!(
+                    &mut dot_file,
+                    "{} -> {} [style=dotted, color=gray]",
+                    item.id().as_usize(),
+                    child.as_usize()
+                )?;
+            }
+        }
+    }
+
+    writeln!(&mut dot_file, "}}")?;
+    Ok(())
+}
diff --git a/third_party/rust/bindgen/ir/enum_ty.rs b/third_party/rust/bindgen/ir/enum_ty.rs
new file mode 100644
index 0000000000..70cf0eae88
--- /dev/null
+++ b/third_party/rust/bindgen/ir/enum_ty.rs
@@ -0,0 +1,323 @@
+//! Intermediate representation for C/C++ enumerations.
+
+use super::super::codegen::EnumVariation;
+use super::context::{BindgenContext, TypeId};
+use super::item::Item;
+use super::ty::{Type, TypeKind};
+use crate::clang;
+use crate::ir::annotations::Annotations;
+use crate::parse::ParseError;
+use crate::regex_set::RegexSet;
+
+/// An enum representing custom handling that can be given to a variant.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum EnumVariantCustomBehavior {
+    /// This variant will be a module containing constants.
+    ModuleConstify,
+    /// This variant will be constified, that is, forced to generate a constant.
+    Constify,
+    /// This variant will be hidden entirely from the resulting enum.
+    Hide,
+}
+
+/// A C/C++ enumeration.
+#[derive(Debug)]
+pub(crate) struct Enum {
+    /// The representation used for this enum; it should be an `IntKind` type or
+    /// an alias to one.
+    ///
+    /// It's `None` if the enum is a forward declaration and isn't defined
+    /// anywhere else, see `tests/headers/func_ptr_in_struct.h`.
+    repr: Option<TypeId>,
+
+    /// The different variants, with explicit values.
+    variants: Vec<EnumVariant>,
+}
+
+impl Enum {
+    /// Construct a new `Enum` with the given representation and variants.
+    pub(crate) fn new(
+        repr: Option<TypeId>,
+        variants: Vec<EnumVariant>,
+    ) -> Self {
+        Enum { repr, variants }
+    }
+
+    /// Get this enumeration's representation.
+    pub(crate) fn repr(&self) -> Option<TypeId> {
+        self.repr
+    }
+
+    /// Get this enumeration's variants.
+    pub(crate) fn variants(&self) -> &[EnumVariant] {
+        &self.variants
+    }
+
+    /// Construct an enumeration from the given Clang type.
+    pub(crate) fn from_ty(
+        ty: &clang::Type,
+        ctx: &mut BindgenContext,
+    ) -> Result<Self, ParseError> {
+        use clang_sys::*;
+        debug!("Enum::from_ty {:?}", ty);
+
+        if ty.kind() != CXType_Enum {
+            return Err(ParseError::Continue);
+        }
+
+        let declaration = ty.declaration().canonical();
+        let repr = declaration
+            .enum_type()
+            .and_then(|et| Item::from_ty(&et, declaration, None, ctx).ok());
+        let mut variants = vec![];
+
+        let variant_ty =
+            repr.and_then(|r| ctx.resolve_type(r).safe_canonical_type(ctx));
+        let is_bool = variant_ty.map_or(false, Type::is_bool);
+
+        // Assume signedness since the default type by the C standard is an int.
+        let is_signed = variant_ty.map_or(true, |ty| match *ty.kind() {
+            TypeKind::Int(ref int_kind) => int_kind.is_signed(),
+            ref other => {
+                panic!("Since when enums can be non-integers? {:?}", other)
+            }
+        });
+
+        let type_name = ty.spelling();
+        let type_name = if type_name.is_empty() {
+            None
+        } else {
+            Some(type_name)
+        };
+        let type_name = type_name.as_deref();
+
+        let definition = declaration.definition().unwrap_or(declaration);
+        definition.visit(|cursor| {
+            if cursor.kind() == CXCursor_EnumConstantDecl {
+                let value = if is_bool {
+                    cursor.enum_val_boolean().map(EnumVariantValue::Boolean)
+                } else if is_signed {
+                    cursor.enum_val_signed().map(EnumVariantValue::Signed)
+                } else {
+                    cursor.enum_val_unsigned().map(EnumVariantValue::Unsigned)
+                };
+                if let Some(val) = value {
+                    let name = cursor.spelling();
+                    let annotations = Annotations::new(&cursor);
+                    let custom_behavior = ctx
+                        .options()
+                        .last_callback(|callbacks| {
+                            callbacks
+                                .enum_variant_behavior(type_name, &name, val)
+                        })
+                        .or_else(|| {
+                            let annotations = annotations.as_ref()?;
+                            if annotations.hide() {
+                                Some(EnumVariantCustomBehavior::Hide)
+                            } else if annotations.constify_enum_variant() {
+                                Some(EnumVariantCustomBehavior::Constify)
+                            } else {
+                                None
+                            }
+                        });
+
+                    let new_name = ctx
+                        .options()
+                        .last_callback(|callbacks| {
+                            callbacks.enum_variant_name(type_name, &name, val)
+                        })
+                        .or_else(|| {
+                            annotations
+                                .as_ref()?
+                                .use_instead_of()?
+                                .last()
+                                .cloned()
+                        })
+                        .unwrap_or_else(|| name.clone());
+
+                    let comment = cursor.raw_comment();
+                    variants.push(EnumVariant::new(
+                        new_name,
+                        name,
+                        comment,
+                        val,
+                        custom_behavior,
+                    ));
+                }
+            }
+            CXChildVisit_Continue
+        });
+        Ok(Enum::new(repr, variants))
+    }
+
+    fn is_matching_enum(
+        &self,
+        ctx: &BindgenContext,
+        enums: &RegexSet,
+        item: &Item,
+    ) -> bool {
+        let path = item.path_for_allowlisting(ctx);
+        let enum_ty = item.expect_type();
+
+        if enums.matches(path[1..].join("::")) {
+            return true;
+        }
+
+        // Test the variants if the enum is anonymous.
+        if enum_ty.name().is_some() {
+            return false;
+        }
+
+        self.variants().iter().any(|v| enums.matches(v.name()))
+    }
+
+    /// Returns the final representation of the enum.
+    pub(crate) fn computed_enum_variation(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> EnumVariation {
+        // ModuleConsts has higher precedence before Rust in order to avoid
+        // problems with overlapping match patterns.
+        if self.is_matching_enum(
+            ctx,
+            &ctx.options().constified_enum_modules,
+            item,
+        ) {
+            EnumVariation::ModuleConsts
+        } else if self.is_matching_enum(
+            ctx,
+            &ctx.options().bitfield_enums,
+            item,
+        ) {
+            EnumVariation::NewType {
+                is_bitfield: true,
+                is_global: false,
+            }
+        } else if self.is_matching_enum(ctx, &ctx.options().newtype_enums, item)
+        {
+            EnumVariation::NewType {
+                is_bitfield: false,
+                is_global: false,
+            }
+        } else if self.is_matching_enum(
+            ctx,
+            &ctx.options().newtype_global_enums,
+            item,
+        ) {
+            EnumVariation::NewType {
+                is_bitfield: false,
+                is_global: true,
+            }
+        } else if self.is_matching_enum(
+            ctx,
+            &ctx.options().rustified_enums,
+            item,
+        ) {
+            EnumVariation::Rust {
+                non_exhaustive: false,
+            }
+        } else if self.is_matching_enum(
+            ctx,
+            &ctx.options().rustified_non_exhaustive_enums,
+            item,
+        ) {
+            EnumVariation::Rust {
+                non_exhaustive: true,
+            }
+        } else if self.is_matching_enum(
+            ctx,
+            &ctx.options().constified_enums,
+            item,
+        ) {
+            EnumVariation::Consts
+        } else {
+            ctx.options().default_enum_style
+        }
+    }
+}
+
+/// A single enum variant, to be contained only in an enum.
+#[derive(Debug)]
+pub(crate) struct EnumVariant {
+    /// The name of the variant.
+    name: String,
+
+    /// The original name of the variant (without user mangling)
+    name_for_allowlisting: String,
+
+    /// An optional doc comment.
+    comment: Option<String>,
+
+    /// The integer value of the variant.
+    val: EnumVariantValue,
+
+    /// The custom behavior this variant may have, if any.
+    custom_behavior: Option<EnumVariantCustomBehavior>,
+}
+
+/// A constant value assigned to an enumeration variant.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum EnumVariantValue {
+    /// A boolean constant.
+    Boolean(bool),
+
+    /// A signed constant.
+    Signed(i64),
+
+    /// An unsigned constant.
+    Unsigned(u64),
+}
+
+impl EnumVariant {
+    /// Construct a new enumeration variant from the given parts.
+    pub(crate) fn new(
+        name: String,
+        name_for_allowlisting: String,
+        comment: Option<String>,
+        val: EnumVariantValue,
+        custom_behavior: Option<EnumVariantCustomBehavior>,
+    ) -> Self {
+        EnumVariant {
+            name,
+            name_for_allowlisting,
+            comment,
+            val,
+            custom_behavior,
+        }
+    }
+
+    /// Get this variant's name.
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Get this variant's name.
+    pub(crate) fn name_for_allowlisting(&self) -> &str {
+        &self.name_for_allowlisting
+    }
+
+    /// Get this variant's value.
+    pub(crate) fn val(&self) -> EnumVariantValue {
+        self.val
+    }
+
+    /// Get this variant's documentation.
+    pub(crate) fn comment(&self) -> Option<&str> {
+        self.comment.as_deref()
+    }
+
+    /// Returns whether this variant should be enforced to be a constant by code
+    /// generation.
+    pub(crate) fn force_constification(&self) -> bool {
+        self.custom_behavior
+            .map_or(false, |b| b == EnumVariantCustomBehavior::Constify)
+    }
+
+    /// Returns whether the current variant should be hidden completely from the
+    /// resulting rust enum.
+    pub(crate) fn hidden(&self) -> bool {
+        self.custom_behavior
+            .map_or(false, |b| b == EnumVariantCustomBehavior::Hide)
+    }
+}
diff --git a/third_party/rust/bindgen/ir/function.rs b/third_party/rust/bindgen/ir/function.rs
new file mode 100644
index 0000000000..448bcd22ea
--- /dev/null
+++ b/third_party/rust/bindgen/ir/function.rs
@@ -0,0 +1,839 @@
+//! Intermediate representation for C/C++ functions and methods.
+
+use super::comp::MethodKind;
+use super::context::{BindgenContext, TypeId};
+use super::dot::DotAttributes;
+use super::item::Item;
+use super::traversal::{EdgeKind, Trace, Tracer};
+use super::ty::TypeKind;
+use crate::callbacks::{ItemInfo, ItemKind};
+use crate::clang::{self, ABIKind, Attribute};
+use crate::parse::{ClangSubItemParser, ParseError, ParseResult};
+use clang_sys::{self, CXCallingConv};
+
+use quote::TokenStreamExt;
+use std::io;
+use std::str::FromStr;
+
+const RUST_DERIVE_FUNPTR_LIMIT: usize = 12;
+
+/// What kind of a function are we looking at?
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum FunctionKind {
+    /// A plain, free function.
+    Function,
+    /// A method of some kind.
+    Method(MethodKind),
+}
+
+impl FunctionKind {
+    /// Given a clang cursor, return the kind of function it represents, or
+    /// `None` otherwise.
+    pub(crate) fn from_cursor(cursor: &clang::Cursor) -> Option<FunctionKind> {
+        // FIXME(emilio): Deduplicate logic with `ir::comp`.
+        Some(match cursor.kind() {
+            clang_sys::CXCursor_FunctionDecl => FunctionKind::Function,
+            clang_sys::CXCursor_Constructor => {
+                FunctionKind::Method(MethodKind::Constructor)
+            }
+            clang_sys::CXCursor_Destructor => {
+                FunctionKind::Method(if cursor.method_is_virtual() {
+                    MethodKind::VirtualDestructor {
+                        pure_virtual: cursor.method_is_pure_virtual(),
+                    }
+                } else {
+                    MethodKind::Destructor
+                })
+            }
+            clang_sys::CXCursor_CXXMethod => {
+                if cursor.method_is_virtual() {
+                    FunctionKind::Method(MethodKind::Virtual {
+                        pure_virtual: cursor.method_is_pure_virtual(),
+                    })
+                } else if cursor.method_is_static() {
+                    FunctionKind::Method(MethodKind::Static)
+                } else {
+                    FunctionKind::Method(MethodKind::Normal)
+                }
+            }
+            _ => return None,
+        })
+    }
+}
+
+/// The style of linkage
+#[derive(Debug, Clone, Copy)]
+pub(crate) enum Linkage {
+    /// Externally visible and can be linked against
+    External,
+    /// Not exposed externally. 'static inline' functions will have this kind of linkage
+    Internal,
+}
+
+/// A function declaration, with a signature, arguments, and argument names.
+///
+/// The argument names vector must be the same length as the ones in the
+/// signature.
+#[derive(Debug)]
+pub(crate) struct Function {
+    /// The name of this function.
+    name: String,
+
+    /// The mangled name, that is, the symbol.
+    mangled_name: Option<String>,
+
+    /// The link name. If specified, overwrite mangled_name.
+    link_name: Option<String>,
+
+    /// The ID pointing to the current function signature.
+    signature: TypeId,
+
+    /// The kind of function this is.
+    kind: FunctionKind,
+
+    /// The linkage of the function.
+    linkage: Linkage,
+}
+
+impl Function {
+    /// Construct a new function.
+    pub(crate) fn new(
+        name: String,
+        mangled_name: Option<String>,
+        link_name: Option<String>,
+        signature: TypeId,
+        kind: FunctionKind,
+        linkage: Linkage,
+    ) -> Self {
+        Function {
+            name,
+            mangled_name,
+            link_name,
+            signature,
+            kind,
+            linkage,
+        }
+    }
+
+    /// Get this function's name.
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Get this function's name.
+    pub(crate) fn mangled_name(&self) -> Option<&str> {
+        self.mangled_name.as_deref()
+    }
+
+    /// Get this function's link name.
+    pub fn link_name(&self) -> Option<&str> {
+        self.link_name.as_deref()
+    }
+
+    /// Get this function's signature type.
+    pub(crate) fn signature(&self) -> TypeId {
+        self.signature
+    }
+
+    /// Get this function's kind.
+    pub(crate) fn kind(&self) -> FunctionKind {
+        self.kind
+    }
+
+    /// Get this function's linkage.
+    pub(crate) fn linkage(&self) -> Linkage {
+        self.linkage
+    }
+}
+
+impl DotAttributes for Function {
+    fn dot_attributes<W>(
+        &self,
+        _ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        if let Some(ref mangled) = self.mangled_name {
+            let mangled: String =
+                mangled.chars().flat_map(|c| c.escape_default()).collect();
+            writeln!(
+                out,
+                "<tr><td>mangled name</td><td>{}</td></tr>",
+                mangled
+            )?;
+        }
+
+        Ok(())
+    }
+}
+
+/// A valid rust ABI.
+#[derive(Debug, Copy, Clone, Hash, Eq, PartialEq)]
+pub enum Abi {
+    /// The default C ABI.
+    C,
+    /// The "stdcall" ABI.
+    Stdcall,
+    /// The "efiapi" ABI.
+    EfiApi,
+    /// The "fastcall" ABI.
+    Fastcall,
+    /// The "thiscall" ABI.
+    ThisCall,
+    /// The "vectorcall" ABI.
+    Vectorcall,
+    /// The "aapcs" ABI.
+    Aapcs,
+    /// The "win64" ABI.
+    Win64,
+    /// The "C-unwind" ABI.
+    CUnwind,
+    /// The "system" ABI.
+    System,
+}
+
+impl FromStr for Abi {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "C" => Ok(Self::C),
+            "stdcall" => Ok(Self::Stdcall),
+            "efiapi" => Ok(Self::EfiApi),
+            "fastcall" => Ok(Self::Fastcall),
+            "thiscall" => Ok(Self::ThisCall),
+            "vectorcall" => Ok(Self::Vectorcall),
+            "aapcs" => Ok(Self::Aapcs),
+            "win64" => Ok(Self::Win64),
+            "C-unwind" => Ok(Self::CUnwind),
+            "system" => Ok(Self::System),
+            _ => Err(format!("Invalid or unknown ABI {:?}", s)),
+        }
+    }
+}
+
+impl std::fmt::Display for Abi {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let s = match *self {
+            Self::C => "C",
+            Self::Stdcall => "stdcall",
+            Self::EfiApi => "efiapi",
+            Self::Fastcall => "fastcall",
+            Self::ThisCall => "thiscall",
+            Self::Vectorcall => "vectorcall",
+            Self::Aapcs => "aapcs",
+            Self::Win64 => "win64",
+            Self::CUnwind => "C-unwind",
+            Abi::System => "system",
+        };
+
+        s.fmt(f)
+    }
+}
+
+impl quote::ToTokens for Abi {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        let abi = self.to_string();
+        tokens.append_all(quote! { #abi });
+    }
+}
+
+/// An ABI extracted from a clang cursor.
+#[derive(Debug, Copy, Clone)]
+pub(crate) enum ClangAbi {
+    /// An ABI known by Rust.
+    Known(Abi),
+    /// An unknown or invalid ABI.
+    Unknown(CXCallingConv),
+}
+
+impl ClangAbi {
+    /// Returns whether this Abi is known or not.
+    fn is_unknown(&self) -> bool {
+        matches!(*self, ClangAbi::Unknown(..))
+    }
+}
+
+impl quote::ToTokens for ClangAbi {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        match *self {
+            Self::Known(abi) => abi.to_tokens(tokens),
+            Self::Unknown(cc) => panic!(
+                "Cannot turn unknown calling convention to tokens: {:?}",
+                cc
+            ),
+        }
+    }
+}
+
+/// A function signature.
+#[derive(Debug)]
+pub(crate) struct FunctionSig {
+    /// The name of this function signature.
+    name: String,
+
+    /// The return type of the function.
+    return_type: TypeId,
+
+    /// The type of the arguments, optionally with the name of the argument when
+    /// declared.
+    argument_types: Vec<(Option<String>, TypeId)>,
+
+    /// Whether this function is variadic.
+    is_variadic: bool,
+    is_divergent: bool,
+
+    /// Whether this function's return value must be used.
+    must_use: bool,
+
+    /// The ABI of this function.
+    abi: ClangAbi,
+}
+
+fn get_abi(cc: CXCallingConv) -> ClangAbi {
+    use clang_sys::*;
+    match cc {
+        CXCallingConv_Default => ClangAbi::Known(Abi::C),
+        CXCallingConv_C => ClangAbi::Known(Abi::C),
+        CXCallingConv_X86StdCall => ClangAbi::Known(Abi::Stdcall),
+        CXCallingConv_X86FastCall => ClangAbi::Known(Abi::Fastcall),
+        CXCallingConv_X86ThisCall => ClangAbi::Known(Abi::ThisCall),
+        CXCallingConv_X86VectorCall => ClangAbi::Known(Abi::Vectorcall),
+        CXCallingConv_AAPCS => ClangAbi::Known(Abi::Aapcs),
+        CXCallingConv_X86_64Win64 => ClangAbi::Known(Abi::Win64),
+        CXCallingConv_AArch64VectorCall => ClangAbi::Known(Abi::Vectorcall),
+        other => ClangAbi::Unknown(other),
+    }
+}
+
+/// Get the mangled name for the cursor's referent.
+pub(crate) fn cursor_mangling(
+    ctx: &BindgenContext,
+    cursor: &clang::Cursor,
+) -> Option<String> {
+    if !ctx.options().enable_mangling {
+        return None;
+    }
+
+    // We early return here because libclang may crash in some case
+    // if we pass in a variable inside a partial specialized template.
+    // See rust-lang/rust-bindgen#67, and rust-lang/rust-bindgen#462.
+    if cursor.is_in_non_fully_specialized_template() {
+        return None;
+    }
+
+    let is_itanium_abi = ctx.abi_kind() == ABIKind::GenericItanium;
+    let is_destructor = cursor.kind() == clang_sys::CXCursor_Destructor;
+    if let Ok(mut manglings) = cursor.cxx_manglings() {
+        while let Some(m) = manglings.pop() {
+            // Only generate the destructor group 1, see below.
+            if is_itanium_abi && is_destructor && !m.ends_with("D1Ev") {
+                continue;
+            }
+
+            return Some(m);
+        }
+    }
+
+    let mut mangling = cursor.mangling();
+    if mangling.is_empty() {
+        return None;
+    }
+
+    if is_itanium_abi && is_destructor {
+        // With old (3.8-) libclang versions, and the Itanium ABI, clang returns
+        // the "destructor group 0" symbol, which means that it'll try to free
+        // memory, which definitely isn't what we want.
+        //
+        // Explicitly force the destructor group 1 symbol.
+        //
+        // See http://refspecs.linuxbase.org/cxxabi-1.83.html#mangling-special
+        // for the reference, and http://stackoverflow.com/a/6614369/1091587 for
+        // a more friendly explanation.
+        //
+        // We don't need to do this for constructors since clang seems to always
+        // have returned the C1 constructor.
+        //
+        // FIXME(emilio): Can a legit symbol in other ABIs end with this string?
+        // I don't think so, but if it can this would become a linker error
+        // anyway, not an invalid free at runtime.
+        //
+        // TODO(emilio, #611): Use cpp_demangle if this becomes nastier with
+        // time.
+        if mangling.ends_with("D0Ev") {
+            let new_len = mangling.len() - 4;
+            mangling.truncate(new_len);
+            mangling.push_str("D1Ev");
+        }
+    }
+
+    Some(mangling)
+}
+
+fn args_from_ty_and_cursor(
+    ty: &clang::Type,
+    cursor: &clang::Cursor,
+    ctx: &mut BindgenContext,
+) -> Vec<(Option<String>, TypeId)> {
+    let cursor_args = cursor.args().unwrap_or_default().into_iter();
+    let type_args = ty.args().unwrap_or_default().into_iter();
+
+    // Argument types can be found in either the cursor or the type, but argument names may only be
+    // found on the cursor. We often have access to both a type and a cursor for each argument, but
+    // in some cases we may only have one.
+    //
+    // Prefer using the type as the source of truth for the argument's type, but fall back to
+    // inspecting the cursor (this happens for Objective C interfaces).
+    //
+    // Prefer using the cursor for the argument's type, but fall back to using the parent's cursor
+    // (this happens for function pointer return types).
+    cursor_args
+        .map(Some)
+        .chain(std::iter::repeat(None))
+        .zip(type_args.map(Some).chain(std::iter::repeat(None)))
+        .take_while(|(cur, ty)| cur.is_some() || ty.is_some())
+        .map(|(arg_cur, arg_ty)| {
+            let name = arg_cur.map(|a| a.spelling()).and_then(|name| {
+                if name.is_empty() {
+                    None
+                } else {
+                    Some(name)
+                }
+            });
+
+            let cursor = arg_cur.unwrap_or(*cursor);
+            let ty = arg_ty.unwrap_or_else(|| cursor.cur_type());
+            (name, Item::from_ty_or_ref(ty, cursor, None, ctx))
+        })
+        .collect()
+}
+
+impl FunctionSig {
+    /// Get the function name.
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Construct a new function signature from the given Clang type.
+    pub(crate) fn from_ty(
+        ty: &clang::Type,
+        cursor: &clang::Cursor,
+        ctx: &mut BindgenContext,
+    ) -> Result<Self, ParseError> {
+        use clang_sys::*;
+        debug!("FunctionSig::from_ty {:?} {:?}", ty, cursor);
+
+        // Skip function templates
+        let kind = cursor.kind();
+        if kind == CXCursor_FunctionTemplate {
+            return Err(ParseError::Continue);
+        }
+
+        let spelling = cursor.spelling();
+
+        // Don't parse operatorxx functions in C++
+        let is_operator = |spelling: &str| {
+            spelling.starts_with("operator") &&
+                !clang::is_valid_identifier(spelling)
+        };
+        if is_operator(&spelling) {
+            return Err(ParseError::Continue);
+        }
+
+        // Constructors of non-type template parameter classes for some reason
+        // include the template parameter in their name. Just skip them, since
+        // we don't handle well non-type template parameters anyway.
+        if (kind == CXCursor_Constructor || kind == CXCursor_Destructor) &&
+            spelling.contains('<')
+        {
+            return Err(ParseError::Continue);
+        }
+
+        let cursor = if cursor.is_valid() {
+            *cursor
+        } else {
+            ty.declaration()
+        };
+
+        let mut args = match kind {
+            CXCursor_FunctionDecl |
+            CXCursor_Constructor |
+            CXCursor_CXXMethod |
+            CXCursor_ObjCInstanceMethodDecl |
+            CXCursor_ObjCClassMethodDecl => {
+                args_from_ty_and_cursor(ty, &cursor, ctx)
+            }
+            _ => {
+                // For non-CXCursor_FunctionDecl, visiting the cursor's children
+                // is the only reliable way to get parameter names.
+                let mut args = vec![];
+                cursor.visit(|c| {
+                    if c.kind() == CXCursor_ParmDecl {
+                        let ty =
+                            Item::from_ty_or_ref(c.cur_type(), c, None, ctx);
+                        let name = c.spelling();
+                        let name =
+                            if name.is_empty() { None } else { Some(name) };
+                        args.push((name, ty));
+                    }
+                    CXChildVisit_Continue
+                });
+
+                if args.is_empty() {
+                    // FIXME(emilio): Sometimes libclang doesn't expose the
+                    // right AST for functions tagged as stdcall and such...
+                    //
+                    // https://bugs.llvm.org/show_bug.cgi?id=45919
+                    args_from_ty_and_cursor(ty, &cursor, ctx)
+                } else {
+                    args
+                }
+            }
+        };
+
+        let (must_use, mut is_divergent) =
+            if ctx.options().enable_function_attribute_detection {
+                let [must_use, no_return, no_return_cpp] = cursor.has_attrs(&[
+                    Attribute::MUST_USE,
+                    Attribute::NO_RETURN,
+                    Attribute::NO_RETURN_CPP,
+                ]);
+                (must_use, no_return || no_return_cpp)
+            } else {
+                Default::default()
+            };
+
+        // Check if the type contains __attribute__((noreturn)) outside of parentheses. This is
+        // somewhat fragile, but it seems to be the only way to get at this information as of
+        // libclang 9.
+        let ty_spelling = ty.spelling();
+        let has_attribute_noreturn = ty_spelling
+            .match_indices("__attribute__((noreturn))")
+            .any(|(i, _)| {
+                let depth = ty_spelling[..i]
+                    .bytes()
+                    .filter_map(|ch| match ch {
+                        b'(' => Some(1),
+                        b')' => Some(-1),
+                        _ => None,
+                    })
+                    .sum::<isize>();
+                depth == 0
+            });
+        is_divergent = is_divergent || has_attribute_noreturn;
+
+        let is_method = kind == CXCursor_CXXMethod;
+        let is_constructor = kind == CXCursor_Constructor;
+        let is_destructor = kind == CXCursor_Destructor;
+        if (is_constructor || is_destructor || is_method) &&
+            cursor.lexical_parent() != cursor.semantic_parent()
+        {
+            // Only parse constructors once.
+            return Err(ParseError::Continue);
+        }
+
+        if is_method || is_constructor || is_destructor {
+            let is_const = is_method && cursor.method_is_const();
+            let is_virtual = is_method && cursor.method_is_virtual();
+            let is_static = is_method && cursor.method_is_static();
+            if !is_static && !is_virtual {
+                let parent = cursor.semantic_parent();
+                let class = Item::parse(parent, None, ctx)
+                    .expect("Expected to parse the class");
+                // The `class` most likely is not finished parsing yet, so use
+                // the unchecked variant.
+                let class = class.as_type_id_unchecked();
+
+                let class = if is_const {
+                    let const_class_id = ctx.next_item_id();
+                    ctx.build_const_wrapper(
+                        const_class_id,
+                        class,
+                        None,
+                        &parent.cur_type(),
+                    )
+                } else {
+                    class
+                };
+
+                let ptr =
+                    Item::builtin_type(TypeKind::Pointer(class), false, ctx);
+                args.insert(0, (Some("this".into()), ptr));
+            } else if is_virtual {
+                let void = Item::builtin_type(TypeKind::Void, false, ctx);
+                let ptr =
+                    Item::builtin_type(TypeKind::Pointer(void), false, ctx);
+                args.insert(0, (Some("this".into()), ptr));
+            }
+        }
+
+        let ty_ret_type = if kind == CXCursor_ObjCInstanceMethodDecl ||
+            kind == CXCursor_ObjCClassMethodDecl
+        {
+            ty.ret_type()
+                .or_else(|| cursor.ret_type())
+                .ok_or(ParseError::Continue)?
+        } else {
+            ty.ret_type().ok_or(ParseError::Continue)?
+        };
+
+        let ret = if is_constructor && ctx.is_target_wasm32() {
+            // Constructors in Clang wasm32 target return a pointer to the object
+            // being constructed.
+            let void = Item::builtin_type(TypeKind::Void, false, ctx);
+            Item::builtin_type(TypeKind::Pointer(void), false, ctx)
+        } else {
+            Item::from_ty_or_ref(ty_ret_type, cursor, None, ctx)
+        };
+
+        // Clang plays with us at "find the calling convention", see #549 and
+        // co. This seems to be a better fix than that commit.
+        let mut call_conv = ty.call_conv();
+        if let Some(ty) = cursor.cur_type().canonical_type().pointee_type() {
+            let cursor_call_conv = ty.call_conv();
+            if cursor_call_conv != CXCallingConv_Invalid {
+                call_conv = cursor_call_conv;
+            }
+        }
+
+        let abi = get_abi(call_conv);
+
+        if abi.is_unknown() {
+            warn!("Unknown calling convention: {:?}", call_conv);
+        }
+
+        Ok(Self {
+            name: spelling,
+            return_type: ret,
+            argument_types: args,
+            is_variadic: ty.is_variadic(),
+            is_divergent,
+            must_use,
+            abi,
+        })
+    }
+
+    /// Get this function signature's return type.
+    pub(crate) fn return_type(&self) -> TypeId {
+        self.return_type
+    }
+
+    /// Get this function signature's argument (name, type) pairs.
+    pub(crate) fn argument_types(&self) -> &[(Option<String>, TypeId)] {
+        &self.argument_types
+    }
+
+    /// Get this function signature's ABI.
+    pub(crate) fn abi(
+        &self,
+        ctx: &BindgenContext,
+        name: Option<&str>,
+    ) -> crate::codegen::error::Result<ClangAbi> {
+        // FIXME (pvdrz): Try to do this check lazily instead. Maybe store the ABI inside `ctx`
+        // instead?.
+        let abi = if let Some(name) = name {
+            if let Some((abi, _)) = ctx
+                .options()
+                .abi_overrides
+                .iter()
+                .find(|(_, regex_set)| regex_set.matches(name))
+            {
+                ClangAbi::Known(*abi)
+            } else {
+                self.abi
+            }
+        } else if let Some((abi, _)) = ctx
+            .options()
+            .abi_overrides
+            .iter()
+            .find(|(_, regex_set)| regex_set.matches(&self.name))
+        {
+            ClangAbi::Known(*abi)
+        } else {
+            self.abi
+        };
+
+        match abi {
+            ClangAbi::Known(Abi::ThisCall)
+                if !ctx.options().rust_features().thiscall_abi =>
+            {
+                Err(crate::codegen::error::Error::UnsupportedAbi("thiscall"))
+            }
+            ClangAbi::Known(Abi::Vectorcall)
+                if !ctx.options().rust_features().vectorcall_abi =>
+            {
+                Err(crate::codegen::error::Error::UnsupportedAbi("vectorcall"))
+            }
+            ClangAbi::Known(Abi::CUnwind)
+                if !ctx.options().rust_features().c_unwind_abi =>
+            {
+                Err(crate::codegen::error::Error::UnsupportedAbi("C-unwind"))
+            }
+            ClangAbi::Known(Abi::EfiApi)
+                if !ctx.options().rust_features().abi_efiapi =>
+            {
+                Err(crate::codegen::error::Error::UnsupportedAbi("efiapi"))
+            }
+            ClangAbi::Known(Abi::Win64) if self.is_variadic() => {
+                Err(crate::codegen::error::Error::UnsupportedAbi("Win64"))
+            }
+            abi => Ok(abi),
+        }
+    }
+
+    /// Is this function signature variadic?
+    pub(crate) fn is_variadic(&self) -> bool {
+        // Clang reports some functions as variadic when they *might* be
+        // variadic. We do the argument check because rust doesn't codegen well
+        // variadic functions without an initial argument.
+        self.is_variadic && !self.argument_types.is_empty()
+    }
+
+    /// Must this function's return value be used?
+    pub(crate) fn must_use(&self) -> bool {
+        self.must_use
+    }
+
+    /// Are function pointers with this signature able to derive Rust traits?
+    /// Rust only supports deriving traits for function pointers with a limited
+    /// number of parameters and a couple ABIs.
+    ///
+    /// For more details, see:
+    ///
+    /// * <https://github.com/rust-lang/rust-bindgen/issues/547>,
+    /// * <https://github.com/rust-lang/rust/issues/38848>,
+    /// * and <https://github.com/rust-lang/rust/issues/40158>
+    pub(crate) fn function_pointers_can_derive(&self) -> bool {
+        if self.argument_types.len() > RUST_DERIVE_FUNPTR_LIMIT {
+            return false;
+        }
+
+        matches!(self.abi, ClangAbi::Known(Abi::C) | ClangAbi::Unknown(..))
+    }
+
+    /// Whether this function has attributes marking it as divergent.
+    pub(crate) fn is_divergent(&self) -> bool {
+        self.is_divergent
+    }
+}
+
+impl ClangSubItemParser for Function {
+    fn parse(
+        cursor: clang::Cursor,
+        context: &mut BindgenContext,
+    ) -> Result<ParseResult<Self>, ParseError> {
+        use clang_sys::*;
+
+        let kind = match FunctionKind::from_cursor(&cursor) {
+            None => return Err(ParseError::Continue),
+            Some(k) => k,
+        };
+
+        debug!("Function::parse({:?}, {:?})", cursor, cursor.cur_type());
+        let visibility = cursor.visibility();
+        if visibility != CXVisibility_Default {
+            return Err(ParseError::Continue);
+        }
+
+        if cursor.access_specifier() == CX_CXXPrivate {
+            return Err(ParseError::Continue);
+        }
+
+        let linkage = cursor.linkage();
+        let linkage = match linkage {
+            CXLinkage_External | CXLinkage_UniqueExternal => Linkage::External,
+            CXLinkage_Internal => Linkage::Internal,
+            _ => return Err(ParseError::Continue),
+        };
+
+        if cursor.is_inlined_function() ||
+            cursor
+                .definition()
+                .map_or(false, |x| x.is_inlined_function())
+        {
+            if !context.options().generate_inline_functions &&
+                !context.options().wrap_static_fns
+            {
+                return Err(ParseError::Continue);
+            }
+
+            if cursor.is_deleted_function() {
+                return Err(ParseError::Continue);
+            }
+
+            // We cannot handle `inline` functions that are not `static`.
+            if context.options().wrap_static_fns &&
+                cursor.is_inlined_function() &&
+                matches!(linkage, Linkage::External)
+            {
+                return Err(ParseError::Continue);
+            }
+        }
+
+        // Grab the signature using Item::from_ty.
+        let sig = Item::from_ty(&cursor.cur_type(), cursor, None, context)?;
+
+        let mut name = cursor.spelling();
+        assert!(!name.is_empty(), "Empty function name?");
+
+        if cursor.kind() == CXCursor_Destructor {
+            // Remove the leading `~`. The alternative to this is special-casing
+            // code-generation for destructor functions, which seems less than
+            // ideal.
+            if name.starts_with('~') {
+                name.remove(0);
+            }
+
+            // Add a suffix to avoid colliding with constructors. This would be
+            // technically fine (since we handle duplicated functions/methods),
+            // but seems easy enough to handle it here.
+            name.push_str("_destructor");
+        }
+        if let Some(nm) = context.options().last_callback(|callbacks| {
+            callbacks.generated_name_override(ItemInfo {
+                name: name.as_str(),
+                kind: ItemKind::Function,
+            })
+        }) {
+            name = nm;
+        }
+        assert!(!name.is_empty(), "Empty function name.");
+
+        let mangled_name = cursor_mangling(context, &cursor);
+
+        let link_name = context.options().last_callback(|callbacks| {
+            callbacks.generated_link_name_override(ItemInfo {
+                name: name.as_str(),
+                kind: ItemKind::Function,
+            })
+        });
+
+        let function = Self::new(
+            name.clone(),
+            mangled_name,
+            link_name,
+            sig,
+            kind,
+            linkage,
+        );
+
+        Ok(ParseResult::New(function, Some(cursor)))
+    }
+}
+
+impl Trace for FunctionSig {
+    type Extra = ();
+
+    fn trace<T>(&self, _: &BindgenContext, tracer: &mut T, _: &())
+    where
+        T: Tracer,
+    {
+        tracer.visit_kind(self.return_type().into(), EdgeKind::FunctionReturn);
+
+        for &(_, ty) in self.argument_types() {
+            tracer.visit_kind(ty.into(), EdgeKind::FunctionParameter);
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/ir/int.rs b/third_party/rust/bindgen/ir/int.rs
new file mode 100644
index 0000000000..4251b3753a
--- /dev/null
+++ b/third_party/rust/bindgen/ir/int.rs
@@ -0,0 +1,127 @@
+//! Intermediate representation for integral types.
+
+/// Which integral type are we dealing with?
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub enum IntKind {
+    /// A `bool`.
+    Bool,
+
+    /// A `signed char`.
+    SChar,
+
+    /// An `unsigned char`.
+    UChar,
+
+    /// A `wchar_t`.
+    WChar,
+
+    /// A platform-dependent `char` type, with the signedness support.
+    Char {
+        /// Whether the char is signed for the target platform.
+        is_signed: bool,
+    },
+
+    /// A `short`.
+    Short,
+
+    /// An `unsigned short`.
+    UShort,
+
+    /// An `int`.
+    Int,
+
+    /// An `unsigned int`.
+    UInt,
+
+    /// A `long`.
+    Long,
+
+    /// An `unsigned long`.
+    ULong,
+
+    /// A `long long`.
+    LongLong,
+
+    /// An `unsigned long long`.
+    ULongLong,
+
+    /// A 8-bit signed integer.
+    I8,
+
+    /// A 8-bit unsigned integer.
+    U8,
+
+    /// A 16-bit signed integer.
+    I16,
+
+    /// Either a `char16_t` or a `wchar_t`.
+    U16,
+
+    /// A 32-bit signed integer.
+    I32,
+
+    /// A 32-bit unsigned integer.
+    U32,
+
+    /// A 64-bit signed integer.
+    I64,
+
+    /// A 64-bit unsigned integer.
+    U64,
+
+    /// An `int128_t`
+    I128,
+
+    /// A `uint128_t`.
+    U128,
+
+    /// A custom integer type, used to allow custom macro types depending on
+    /// range.
+    Custom {
+        /// The name of the type, which would be used without modification.
+        name: &'static str,
+        /// Whether the type is signed or not.
+        is_signed: bool,
+    },
+}
+
+impl IntKind {
+    /// Is this integral type signed?
+    pub(crate) fn is_signed(&self) -> bool {
+        use self::IntKind::*;
+        match *self {
+            // TODO(emilio): wchar_t can in theory be signed, but we have no way
+            // to know whether it is or not right now (unlike char, there's no
+            // WChar_S / WChar_U).
+            Bool | UChar | UShort | UInt | ULong | ULongLong | U8 | U16 |
+            WChar | U32 | U64 | U128 => false,
+
+            SChar | Short | Int | Long | LongLong | I8 | I16 | I32 | I64 |
+            I128 => true,
+
+            Char { is_signed } => is_signed,
+
+            Custom { is_signed, .. } => is_signed,
+        }
+    }
+
+    /// If this type has a known size, return it (in bytes). This is to
+    /// alleviate libclang sometimes not giving us a layout (like in the case
+    /// when an enum is defined inside a class with template parameters).
+    pub(crate) fn known_size(&self) -> Option<usize> {
+        use self::IntKind::*;
+        Some(match *self {
+            Bool | UChar | SChar | U8 | I8 | Char { .. } => 1,
+            U16 | I16 => 2,
+            U32 | I32 => 4,
+            U64 | I64 => 8,
+            I128 | U128 => 16,
+            _ => return None,
+        })
+    }
+
+    /// Whether this type's signedness matches the value.
+    pub(crate) fn signedness_matches(&self, val: i64) -> bool {
+        val >= 0 || self.is_signed()
+    }
+}
diff --git a/third_party/rust/bindgen/ir/item.rs b/third_party/rust/bindgen/ir/item.rs
new file mode 100644
index 0000000000..2941eb81e2
--- /dev/null
+++ b/third_party/rust/bindgen/ir/item.rs
@@ -0,0 +1,2034 @@
+//! Bindgen's core intermediate representation type.
+
+use super::super::codegen::{EnumVariation, CONSTIFIED_ENUM_MODULE_REPR_NAME};
+use super::analysis::{HasVtable, HasVtableResult, Sizedness, SizednessResult};
+use super::annotations::Annotations;
+use super::comp::{CompKind, MethodKind};
+use super::context::{BindgenContext, ItemId, PartialType, TypeId};
+use super::derive::{
+    CanDeriveCopy, CanDeriveDebug, CanDeriveDefault, CanDeriveEq,
+    CanDeriveHash, CanDeriveOrd, CanDerivePartialEq, CanDerivePartialOrd,
+};
+use super::dot::DotAttributes;
+use super::function::{Function, FunctionKind};
+use super::item_kind::ItemKind;
+use super::layout::Opaque;
+use super::module::Module;
+use super::template::{AsTemplateParam, TemplateParameters};
+use super::traversal::{EdgeKind, Trace, Tracer};
+use super::ty::{Type, TypeKind};
+use crate::clang;
+use crate::parse::{ClangSubItemParser, ParseError, ParseResult};
+
+use lazycell::LazyCell;
+
+use std::cell::Cell;
+use std::collections::BTreeSet;
+use std::fmt::Write;
+use std::io;
+use std::iter;
+
+/// A trait to get the canonical name from an item.
+///
+/// This is the trait that will eventually isolate all the logic related to name
+/// mangling and that kind of stuff.
+///
+/// This assumes no nested paths, at some point I'll have to make it a more
+/// complex thing.
+///
+/// This name is required to be safe for Rust, that is, is not expected to
+/// return any rust keyword from here.
+pub(crate) trait ItemCanonicalName {
+    /// Get the canonical name for this item.
+    fn canonical_name(&self, ctx: &BindgenContext) -> String;
+}
+
+/// The same, but specifies the path that needs to be followed to reach an item.
+///
+/// To contrast with canonical_name, here's an example:
+///
+/// ```c++
+/// namespace foo {
+///     const BAR = 3;
+/// }
+/// ```
+///
+/// For bar, the canonical path is `vec!["foo", "BAR"]`, while the canonical
+/// name is just `"BAR"`.
+pub(crate) trait ItemCanonicalPath {
+    /// Get the namespace-aware canonical path for this item. This means that if
+    /// namespaces are disabled, you'll get a single item, and otherwise you get
+    /// the whole path.
+    fn namespace_aware_canonical_path(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Vec<String>;
+
+    /// Get the canonical path for this item.
+    fn canonical_path(&self, ctx: &BindgenContext) -> Vec<String>;
+}
+
+/// A trait for determining if some IR thing is opaque or not.
+pub(crate) trait IsOpaque {
+    /// Extra context the IR thing needs to determine if it is opaque or not.
+    type Extra;
+
+    /// Returns `true` if the thing is opaque, and `false` otherwise.
+    ///
+    /// May only be called when `ctx` is in the codegen phase.
+    fn is_opaque(&self, ctx: &BindgenContext, extra: &Self::Extra) -> bool;
+}
+
+/// A trait for determining if some IR thing has type parameter in array or not.
+pub(crate) trait HasTypeParamInArray {
+    /// Returns `true` if the thing has Array, and `false` otherwise.
+    fn has_type_param_in_array(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait for determining if some IR thing has float or not.
+pub(crate) trait HasFloat {
+    /// Returns `true` if the thing has float, and `false` otherwise.
+    fn has_float(&self, ctx: &BindgenContext) -> bool;
+}
+
+/// A trait for iterating over an item and its parents and up its ancestor chain
+/// up to (but not including) the implicit root module.
+pub(crate) trait ItemAncestors {
+    /// Get an iterable over this item's ancestors.
+    fn ancestors<'a>(&self, ctx: &'a BindgenContext) -> ItemAncestorsIter<'a>;
+}
+
+#[cfg(feature = "__testing_only_extra_assertions")]
+type DebugOnlyItemSet = ItemSet;
+
+#[cfg(not(feature = "__testing_only_extra_assertions"))]
+struct DebugOnlyItemSet;
+
+#[cfg(not(feature = "__testing_only_extra_assertions"))]
+impl DebugOnlyItemSet {
+    fn new() -> Self {
+        DebugOnlyItemSet
+    }
+
+    fn contains(&self, _id: &ItemId) -> bool {
+        false
+    }
+
+    fn insert(&mut self, _id: ItemId) {}
+}
+
+/// An iterator over an item and its ancestors.
+pub(crate) struct ItemAncestorsIter<'a> {
+    item: ItemId,
+    ctx: &'a BindgenContext,
+    seen: DebugOnlyItemSet,
+}
+
+impl<'a> ItemAncestorsIter<'a> {
+    fn new<Id: Into<ItemId>>(ctx: &'a BindgenContext, id: Id) -> Self {
+        ItemAncestorsIter {
+            item: id.into(),
+            ctx,
+            seen: DebugOnlyItemSet::new(),
+        }
+    }
+}
+
+impl<'a> Iterator for ItemAncestorsIter<'a> {
+    type Item = ItemId;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let item = self.ctx.resolve_item(self.item);
+
+        if item.parent_id() == self.item {
+            None
+        } else {
+            self.item = item.parent_id();
+
+            extra_assert!(!self.seen.contains(&item.id()));
+            self.seen.insert(item.id());
+
+            Some(item.id())
+        }
+    }
+}
+
+impl<T> AsTemplateParam for T
+where
+    T: Copy + Into<ItemId>,
+{
+    type Extra = ();
+
+    fn as_template_param(
+        &self,
+        ctx: &BindgenContext,
+        _: &(),
+    ) -> Option<TypeId> {
+        ctx.resolve_item((*self).into()).as_template_param(ctx, &())
+    }
+}
+
+impl AsTemplateParam for Item {
+    type Extra = ();
+
+    fn as_template_param(
+        &self,
+        ctx: &BindgenContext,
+        _: &(),
+    ) -> Option<TypeId> {
+        self.kind.as_template_param(ctx, self)
+    }
+}
+
+impl AsTemplateParam for ItemKind {
+    type Extra = Item;
+
+    fn as_template_param(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> Option<TypeId> {
+        match *self {
+            ItemKind::Type(ref ty) => ty.as_template_param(ctx, item),
+            ItemKind::Module(..) |
+            ItemKind::Function(..) |
+            ItemKind::Var(..) => None,
+        }
+    }
+}
+
+impl<T> ItemCanonicalName for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn canonical_name(&self, ctx: &BindgenContext) -> String {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.resolve_item(*self).canonical_name(ctx)
+    }
+}
+
+impl<T> ItemCanonicalPath for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn namespace_aware_canonical_path(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Vec<String> {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.resolve_item(*self).namespace_aware_canonical_path(ctx)
+    }
+
+    fn canonical_path(&self, ctx: &BindgenContext) -> Vec<String> {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.resolve_item(*self).canonical_path(ctx)
+    }
+}
+
+impl<T> ItemAncestors for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn ancestors<'a>(&self, ctx: &'a BindgenContext) -> ItemAncestorsIter<'a> {
+        ItemAncestorsIter::new(ctx, *self)
+    }
+}
+
+impl ItemAncestors for Item {
+    fn ancestors<'a>(&self, ctx: &'a BindgenContext) -> ItemAncestorsIter<'a> {
+        self.id().ancestors(ctx)
+    }
+}
+
+impl<Id> Trace for Id
+where
+    Id: Copy + Into<ItemId>,
+{
+    type Extra = ();
+
+    fn trace<T>(&self, ctx: &BindgenContext, tracer: &mut T, extra: &())
+    where
+        T: Tracer,
+    {
+        ctx.resolve_item(*self).trace(ctx, tracer, extra);
+    }
+}
+
+impl Trace for Item {
+    type Extra = ();
+
+    fn trace<T>(&self, ctx: &BindgenContext, tracer: &mut T, _extra: &())
+    where
+        T: Tracer,
+    {
+        // Even if this item is blocklisted/hidden, we want to trace it. It is
+        // traversal iterators' consumers' responsibility to filter items as
+        // needed. Generally, this filtering happens in the implementation of
+        // `Iterator` for `allowlistedItems`. Fully tracing blocklisted items is
+        // necessary for things like the template parameter usage analysis to
+        // function correctly.
+
+        match *self.kind() {
+            ItemKind::Type(ref ty) => {
+                // There are some types, like resolved type references, where we
+                // don't want to stop collecting types even though they may be
+                // opaque.
+                if ty.should_be_traced_unconditionally() ||
+                    !self.is_opaque(ctx, &())
+                {
+                    ty.trace(ctx, tracer, self);
+                }
+            }
+            ItemKind::Function(ref fun) => {
+                // Just the same way, it has not real meaning for a function to
+                // be opaque, so we trace across it.
+                tracer.visit(fun.signature().into());
+            }
+            ItemKind::Var(ref var) => {
+                tracer.visit_kind(var.ty().into(), EdgeKind::VarType);
+            }
+            ItemKind::Module(_) => {
+                // Module -> children edges are "weak", and we do not want to
+                // trace them. If we did, then allowlisting wouldn't work as
+                // expected: everything in every module would end up
+                // allowlisted.
+                //
+                // TODO: make a new edge kind for module -> children edges and
+                // filter them during allowlisting traversals.
+            }
+        }
+    }
+}
+
+impl CanDeriveDebug for Item {
+    fn can_derive_debug(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_debug(ctx)
+    }
+}
+
+impl CanDeriveDefault for Item {
+    fn can_derive_default(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_default(ctx)
+    }
+}
+
+impl CanDeriveCopy for Item {
+    fn can_derive_copy(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_copy(ctx)
+    }
+}
+
+impl CanDeriveHash for Item {
+    fn can_derive_hash(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_hash(ctx)
+    }
+}
+
+impl CanDerivePartialOrd for Item {
+    fn can_derive_partialord(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_partialord(ctx)
+    }
+}
+
+impl CanDerivePartialEq for Item {
+    fn can_derive_partialeq(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_partialeq(ctx)
+    }
+}
+
+impl CanDeriveEq for Item {
+    fn can_derive_eq(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_eq(ctx)
+    }
+}
+
+impl CanDeriveOrd for Item {
+    fn can_derive_ord(&self, ctx: &BindgenContext) -> bool {
+        self.id().can_derive_ord(ctx)
+    }
+}
+
+/// An item is the base of the bindgen representation, it can be either a
+/// module, a type, a function, or a variable (see `ItemKind` for more
+/// information).
+///
+/// Items refer to each other by `ItemId`. Every item has its parent's
+/// ID. Depending on the kind of item this is, it may also refer to other items,
+/// such as a compound type item referring to other types. Collectively, these
+/// references form a graph.
+///
+/// The entry-point to this graph is the "root module": a meta-item used to hold
+/// all top-level items.
+///
+/// An item may have a comment, and annotations (see the `annotations` module).
+///
+/// Note that even though we parse all the types of annotations in comments, not
+/// all of them apply to every item. Those rules are described in the
+/// `annotations` module.
+#[derive(Debug)]
+pub(crate) struct Item {
+    /// This item's ID.
+    id: ItemId,
+
+    /// The item's local ID, unique only amongst its siblings. Only used for
+    /// anonymous items.
+    ///
+    /// Lazily initialized in local_id().
+    ///
+    /// Note that only structs, unions, and enums get a local type ID. In any
+    /// case this is an implementation detail.
+    local_id: LazyCell<usize>,
+
+    /// The next local ID to use for a child or template instantiation.
+    next_child_local_id: Cell<usize>,
+
+    /// A cached copy of the canonical name, as returned by `canonical_name`.
+    ///
+    /// This is a fairly used operation during codegen so this makes bindgen
+    /// considerably faster in those cases.
+    canonical_name: LazyCell<String>,
+
+    /// The path to use for allowlisting and other name-based checks, as
+    /// returned by `path_for_allowlisting`, lazily constructed.
+    path_for_allowlisting: LazyCell<Vec<String>>,
+
+    /// A doc comment over the item, if any.
+    comment: Option<String>,
+    /// Annotations extracted from the doc comment, or the default ones
+    /// otherwise.
+    annotations: Annotations,
+    /// An item's parent ID. This will most likely be a class where this item
+    /// was declared, or a module, etc.
+    ///
+    /// All the items have a parent, except the root module, in which case the
+    /// parent ID is its own ID.
+    parent_id: ItemId,
+    /// The item kind.
+    kind: ItemKind,
+    /// The source location of the item.
+    location: Option<clang::SourceLocation>,
+}
+
+impl AsRef<ItemId> for Item {
+    fn as_ref(&self) -> &ItemId {
+        &self.id
+    }
+}
+
+impl Item {
+    /// Construct a new `Item`.
+    pub(crate) fn new(
+        id: ItemId,
+        comment: Option<String>,
+        annotations: Option<Annotations>,
+        parent_id: ItemId,
+        kind: ItemKind,
+        location: Option<clang::SourceLocation>,
+    ) -> Self {
+        debug_assert!(id != parent_id || kind.is_module());
+        Item {
+            id,
+            local_id: LazyCell::new(),
+            next_child_local_id: Cell::new(1),
+            canonical_name: LazyCell::new(),
+            path_for_allowlisting: LazyCell::new(),
+            parent_id,
+            comment,
+            annotations: annotations.unwrap_or_default(),
+            kind,
+            location,
+        }
+    }
+
+    /// Construct a new opaque item type.
+    pub(crate) fn new_opaque_type(
+        with_id: ItemId,
+        ty: &clang::Type,
+        ctx: &mut BindgenContext,
+    ) -> TypeId {
+        let location = ty.declaration().location();
+        let ty = Opaque::from_clang_ty(ty, ctx);
+        let kind = ItemKind::Type(ty);
+        let parent = ctx.root_module().into();
+        ctx.add_item(
+            Item::new(with_id, None, None, parent, kind, Some(location)),
+            None,
+            None,
+        );
+        with_id.as_type_id_unchecked()
+    }
+
+    /// Get this `Item`'s identifier.
+    pub(crate) fn id(&self) -> ItemId {
+        self.id
+    }
+
+    /// Get this `Item`'s parent's identifier.
+    ///
+    /// For the root module, the parent's ID is its own ID.
+    pub(crate) fn parent_id(&self) -> ItemId {
+        self.parent_id
+    }
+
+    /// Set this item's parent ID.
+    ///
+    /// This is only used so replacements get generated in the proper module.
+    pub(crate) fn set_parent_for_replacement<Id: Into<ItemId>>(
+        &mut self,
+        id: Id,
+    ) {
+        self.parent_id = id.into();
+    }
+
+    /// Returns the depth this item is indented to.
+    ///
+    /// FIXME(emilio): This may need fixes for the enums within modules stuff.
+    pub(crate) fn codegen_depth(&self, ctx: &BindgenContext) -> usize {
+        if !ctx.options().enable_cxx_namespaces {
+            return 0;
+        }
+
+        self.ancestors(ctx)
+            .filter(|id| {
+                ctx.resolve_item(*id).as_module().map_or(false, |module| {
+                    !module.is_inline() ||
+                        ctx.options().conservative_inline_namespaces
+                })
+            })
+            .count() +
+            1
+    }
+
+    /// Get this `Item`'s comment, if it has any, already preprocessed and with
+    /// the right indentation.
+    pub(crate) fn comment(&self, ctx: &BindgenContext) -> Option<String> {
+        if !ctx.options().generate_comments {
+            return None;
+        }
+
+        self.comment
+            .as_ref()
+            .map(|comment| ctx.options().process_comment(comment))
+    }
+
+    /// What kind of item is this?
+    pub(crate) fn kind(&self) -> &ItemKind {
+        &self.kind
+    }
+
+    /// Get a mutable reference to this item's kind.
+    pub(crate) fn kind_mut(&mut self) -> &mut ItemKind {
+        &mut self.kind
+    }
+
+    /// Where in the source is this item located?
+    pub(crate) fn location(&self) -> Option<&clang::SourceLocation> {
+        self.location.as_ref()
+    }
+
+    /// Get an identifier that differentiates this item from its siblings.
+    ///
+    /// This should stay relatively stable in the face of code motion outside or
+    /// below this item's lexical scope, meaning that this can be useful for
+    /// generating relatively stable identifiers within a scope.
+    pub(crate) fn local_id(&self, ctx: &BindgenContext) -> usize {
+        *self.local_id.borrow_with(|| {
+            let parent = ctx.resolve_item(self.parent_id);
+            parent.next_child_local_id()
+        })
+    }
+
+    /// Get an identifier that differentiates a child of this item of other
+    /// related items.
+    ///
+    /// This is currently used for anonymous items, and template instantiation
+    /// tests, in both cases in order to reduce noise when system headers are at
+    /// place.
+    pub(crate) fn next_child_local_id(&self) -> usize {
+        let local_id = self.next_child_local_id.get();
+        self.next_child_local_id.set(local_id + 1);
+        local_id
+    }
+
+    /// Returns whether this item is a top-level item, from the point of view of
+    /// bindgen.
+    ///
+    /// This point of view changes depending on whether namespaces are enabled
+    /// or not. That way, in the following example:
+    ///
+    /// ```c++
+    /// namespace foo {
+    ///     static int var;
+    /// }
+    /// ```
+    ///
+    /// `var` would be a toplevel item if namespaces are disabled, but won't if
+    /// they aren't.
+    ///
+    /// This function is used to determine when the codegen phase should call
+    /// `codegen` on an item, since any item that is not top-level will be
+    /// generated by its parent.
+    pub(crate) fn is_toplevel(&self, ctx: &BindgenContext) -> bool {
+        // FIXME: Workaround for some types falling behind when parsing weird
+        // stl classes, for example.
+        if ctx.options().enable_cxx_namespaces &&
+            self.kind().is_module() &&
+            self.id() != ctx.root_module()
+        {
+            return false;
+        }
+
+        let mut parent = self.parent_id;
+        loop {
+            let parent_item = match ctx.resolve_item_fallible(parent) {
+                Some(item) => item,
+                None => return false,
+            };
+
+            if parent_item.id() == ctx.root_module() {
+                return true;
+            } else if ctx.options().enable_cxx_namespaces ||
+                !parent_item.kind().is_module()
+            {
+                return false;
+            }
+
+            parent = parent_item.parent_id();
+        }
+    }
+
+    /// Get a reference to this item's underlying `Type`. Panic if this is some
+    /// other kind of item.
+    pub(crate) fn expect_type(&self) -> &Type {
+        self.kind().expect_type()
+    }
+
+    /// Get a reference to this item's underlying `Type`, or `None` if this is
+    /// some other kind of item.
+    pub(crate) fn as_type(&self) -> Option<&Type> {
+        self.kind().as_type()
+    }
+
+    /// Get a reference to this item's underlying `Function`. Panic if this is
+    /// some other kind of item.
+    pub(crate) fn expect_function(&self) -> &Function {
+        self.kind().expect_function()
+    }
+
+    /// Is this item a module?
+    pub(crate) fn is_module(&self) -> bool {
+        matches!(self.kind, ItemKind::Module(..))
+    }
+
+    /// Get this item's annotations.
+    pub(crate) fn annotations(&self) -> &Annotations {
+        &self.annotations
+    }
+
+    /// Whether this item should be blocklisted.
+    ///
+    /// This may be due to either annotations or to other kind of configuration.
+    pub(crate) fn is_blocklisted(&self, ctx: &BindgenContext) -> bool {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        if self.annotations.hide() {
+            return true;
+        }
+
+        if !ctx.options().blocklisted_files.is_empty() {
+            if let Some(location) = &self.location {
+                let (file, _, _, _) = location.location();
+                if let Some(filename) = file.name() {
+                    if ctx.options().blocklisted_files.matches(filename) {
+                        return true;
+                    }
+                }
+            }
+        }
+
+        let path = self.path_for_allowlisting(ctx);
+        let name = path[1..].join("::");
+        ctx.options().blocklisted_items.matches(&name) ||
+            match self.kind {
+                ItemKind::Type(..) => {
+                    ctx.options().blocklisted_types.matches(&name) ||
+                        ctx.is_replaced_type(path, self.id)
+                }
+                ItemKind::Function(..) => {
+                    ctx.options().blocklisted_functions.matches(&name)
+                }
+                ItemKind::Var(..) => {
+                    ctx.options().blocklisted_vars.matches(&name)
+                }
+                // TODO: Add namespace blocklisting?
+                ItemKind::Module(..) => false,
+            }
+    }
+
+    /// Take out item NameOptions
+    pub(crate) fn name<'a>(
+        &'a self,
+        ctx: &'a BindgenContext,
+    ) -> NameOptions<'a> {
+        NameOptions::new(self, ctx)
+    }
+
+    /// Get the target item ID for name generation.
+    fn name_target(&self, ctx: &BindgenContext) -> ItemId {
+        let mut targets_seen = DebugOnlyItemSet::new();
+        let mut item = self;
+
+        loop {
+            extra_assert!(!targets_seen.contains(&item.id()));
+            targets_seen.insert(item.id());
+
+            if self.annotations().use_instead_of().is_some() {
+                return self.id();
+            }
+
+            match *item.kind() {
+                ItemKind::Type(ref ty) => match *ty.kind() {
+                    TypeKind::ResolvedTypeRef(inner) => {
+                        item = ctx.resolve_item(inner);
+                    }
+                    TypeKind::TemplateInstantiation(ref inst) => {
+                        item = ctx.resolve_item(inst.template_definition());
+                    }
+                    _ => return item.id(),
+                },
+                _ => return item.id(),
+            }
+        }
+    }
+
+    /// Create a fully disambiguated name for an item, including template
+    /// parameters if it is a type
+    pub(crate) fn full_disambiguated_name(
+        &self,
+        ctx: &BindgenContext,
+    ) -> String {
+        let mut s = String::new();
+        let level = 0;
+        self.push_disambiguated_name(ctx, &mut s, level);
+        s
+    }
+
+    /// Helper function for full_disambiguated_name
+    fn push_disambiguated_name(
+        &self,
+        ctx: &BindgenContext,
+        to: &mut String,
+        level: u8,
+    ) {
+        to.push_str(&self.canonical_name(ctx));
+        if let ItemKind::Type(ref ty) = *self.kind() {
+            if let TypeKind::TemplateInstantiation(ref inst) = *ty.kind() {
+                to.push_str(&format!("_open{}_", level));
+                for arg in inst.template_arguments() {
+                    arg.into_resolver()
+                        .through_type_refs()
+                        .resolve(ctx)
+                        .push_disambiguated_name(ctx, to, level + 1);
+                    to.push('_');
+                }
+                to.push_str(&format!("close{}", level));
+            }
+        }
+    }
+
+    /// Get this function item's name, or `None` if this item is not a function.
+    fn func_name(&self) -> Option<&str> {
+        match *self.kind() {
+            ItemKind::Function(ref func) => Some(func.name()),
+            _ => None,
+        }
+    }
+
+    /// Get the overload index for this method. If this is not a method, return
+    /// `None`.
+    fn overload_index(&self, ctx: &BindgenContext) -> Option<usize> {
+        self.func_name().and_then(|func_name| {
+            let parent = ctx.resolve_item(self.parent_id());
+            if let ItemKind::Type(ref ty) = *parent.kind() {
+                if let TypeKind::Comp(ref ci) = *ty.kind() {
+                    // All the constructors have the same name, so no need to
+                    // resolve and check.
+                    return ci
+                        .constructors()
+                        .iter()
+                        .position(|c| *c == self.id())
+                        .or_else(|| {
+                            ci.methods()
+                                .iter()
+                                .filter(|m| {
+                                    let item = ctx.resolve_item(m.signature());
+                                    let func = item.expect_function();
+                                    func.name() == func_name
+                                })
+                                .position(|m| m.signature() == self.id())
+                        });
+                }
+            }
+
+            None
+        })
+    }
+
+    /// Get this item's base name (aka non-namespaced name).
+    fn base_name(&self, ctx: &BindgenContext) -> String {
+        if let Some(path) = self.annotations().use_instead_of() {
+            return path.last().unwrap().clone();
+        }
+
+        match *self.kind() {
+            ItemKind::Var(ref var) => var.name().to_owned(),
+            ItemKind::Module(ref module) => {
+                module.name().map(ToOwned::to_owned).unwrap_or_else(|| {
+                    format!("_bindgen_mod_{}", self.exposed_id(ctx))
+                })
+            }
+            ItemKind::Type(ref ty) => {
+                ty.sanitized_name(ctx).map(Into::into).unwrap_or_else(|| {
+                    format!("_bindgen_ty_{}", self.exposed_id(ctx))
+                })
+            }
+            ItemKind::Function(ref fun) => {
+                let mut name = fun.name().to_owned();
+
+                if let Some(idx) = self.overload_index(ctx) {
+                    if idx > 0 {
+                        write!(&mut name, "{}", idx).unwrap();
+                    }
+                }
+
+                name
+            }
+        }
+    }
+
+    fn is_anon(&self) -> bool {
+        match self.kind() {
+            ItemKind::Module(module) => module.name().is_none(),
+            ItemKind::Type(ty) => ty.name().is_none(),
+            ItemKind::Function(_) => false,
+            ItemKind::Var(_) => false,
+        }
+    }
+
+    /// Get the canonical name without taking into account the replaces
+    /// annotation.
+    ///
+    /// This is the base logic used to implement hiding and replacing via
+    /// annotations, and also to implement proper name mangling.
+    ///
+    /// The idea is that each generated type in the same "level" (read: module
+    /// or namespace) has a unique canonical name.
+    ///
+    /// This name should be derived from the immutable state contained in the
+    /// type and the parent chain, since it should be consistent.
+    ///
+    /// If `BindgenOptions::disable_nested_struct_naming` is true then returned
+    /// name is the inner most non-anonymous name plus all the anonymous base names
+    /// that follows.
+    pub(crate) fn real_canonical_name(
+        &self,
+        ctx: &BindgenContext,
+        opt: &NameOptions,
+    ) -> String {
+        let target = ctx.resolve_item(self.name_target(ctx));
+
+        // Short-circuit if the target has an override, and just use that.
+        if let Some(path) = target.annotations.use_instead_of() {
+            if ctx.options().enable_cxx_namespaces {
+                return path.last().unwrap().clone();
+            }
+            return path.join("_");
+        }
+
+        let base_name = target.base_name(ctx);
+
+        // Named template type arguments are never namespaced, and never
+        // mangled.
+        if target.is_template_param(ctx, &()) {
+            return base_name;
+        }
+
+        // Ancestors' ID iter
+        let mut ids_iter = target
+            .parent_id()
+            .ancestors(ctx)
+            .filter(|id| *id != ctx.root_module())
+            .take_while(|id| {
+                // Stop iterating ancestors once we reach a non-inline namespace
+                // when opt.within_namespaces is set.
+                !opt.within_namespaces || !ctx.resolve_item(*id).is_module()
+            })
+            .filter(|id| {
+                if !ctx.options().conservative_inline_namespaces {
+                    if let ItemKind::Module(ref module) =
+                        *ctx.resolve_item(*id).kind()
+                    {
+                        return !module.is_inline();
+                    }
+                }
+
+                true
+            });
+
+        let ids: Vec<_> = if ctx.options().disable_nested_struct_naming {
+            let mut ids = Vec::new();
+
+            // If target is anonymous we need find its first named ancestor.
+            if target.is_anon() {
+                for id in ids_iter.by_ref() {
+                    ids.push(id);
+
+                    if !ctx.resolve_item(id).is_anon() {
+                        break;
+                    }
+                }
+            }
+
+            ids
+        } else {
+            ids_iter.collect()
+        };
+
+        // Concatenate this item's ancestors' names together.
+        let mut names: Vec<_> = ids
+            .into_iter()
+            .map(|id| {
+                let item = ctx.resolve_item(id);
+                let target = ctx.resolve_item(item.name_target(ctx));
+                target.base_name(ctx)
+            })
+            .filter(|name| !name.is_empty())
+            .collect();
+
+        names.reverse();
+
+        if !base_name.is_empty() {
+            names.push(base_name);
+        }
+
+        if ctx.options().c_naming {
+            if let Some(prefix) = self.c_naming_prefix() {
+                names.insert(0, prefix.to_string());
+            }
+        }
+
+        let name = names.join("_");
+
+        let name = if opt.user_mangled == UserMangled::Yes {
+            ctx.options()
+                .last_callback(|callbacks| callbacks.item_name(&name))
+                .unwrap_or(name)
+        } else {
+            name
+        };
+
+        ctx.rust_mangle(&name).into_owned()
+    }
+
+    /// The exposed ID that represents an unique ID among the siblings of a
+    /// given item.
+    pub(crate) fn exposed_id(&self, ctx: &BindgenContext) -> String {
+        // Only use local ids for enums, classes, structs and union types.  All
+        // other items use their global ID.
+        let ty_kind = self.kind().as_type().map(|t| t.kind());
+        if let Some(ty_kind) = ty_kind {
+            match *ty_kind {
+                TypeKind::Comp(..) |
+                TypeKind::TemplateInstantiation(..) |
+                TypeKind::Enum(..) => return self.local_id(ctx).to_string(),
+                _ => {}
+            }
+        }
+
+        // Note that this `id_` prefix prevents (really unlikely) collisions
+        // between the global ID and the local ID of an item with the same
+        // parent.
+        format!("id_{}", self.id().as_usize())
+    }
+
+    /// Get a reference to this item's `Module`, or `None` if this is not a
+    /// `Module` item.
+    pub(crate) fn as_module(&self) -> Option<&Module> {
+        match self.kind {
+            ItemKind::Module(ref module) => Some(module),
+            _ => None,
+        }
+    }
+
+    /// Get a mutable reference to this item's `Module`, or `None` if this is
+    /// not a `Module` item.
+    pub(crate) fn as_module_mut(&mut self) -> Option<&mut Module> {
+        match self.kind {
+            ItemKind::Module(ref mut module) => Some(module),
+            _ => None,
+        }
+    }
+
+    /// Returns whether the item is a constified module enum
+    fn is_constified_enum_module(&self, ctx: &BindgenContext) -> bool {
+        // Do not jump through aliases, except for aliases that point to a type
+        // with the same name, since we dont generate coe for them.
+        let item = self.id.into_resolver().through_type_refs().resolve(ctx);
+        let type_ = match *item.kind() {
+            ItemKind::Type(ref type_) => type_,
+            _ => return false,
+        };
+
+        match *type_.kind() {
+            TypeKind::Enum(ref enum_) => {
+                enum_.computed_enum_variation(ctx, self) ==
+                    EnumVariation::ModuleConsts
+            }
+            TypeKind::Alias(inner_id) => {
+                // TODO(emilio): Make this "hop through type aliases that aren't
+                // really generated" an option in `ItemResolver`?
+                let inner_item = ctx.resolve_item(inner_id);
+                let name = item.canonical_name(ctx);
+
+                if inner_item.canonical_name(ctx) == name {
+                    inner_item.is_constified_enum_module(ctx)
+                } else {
+                    false
+                }
+            }
+            _ => false,
+        }
+    }
+
+    /// Is this item of a kind that is enabled for code generation?
+    pub(crate) fn is_enabled_for_codegen(&self, ctx: &BindgenContext) -> bool {
+        let cc = &ctx.options().codegen_config;
+        match *self.kind() {
+            ItemKind::Module(..) => true,
+            ItemKind::Var(_) => cc.vars(),
+            ItemKind::Type(_) => cc.types(),
+            ItemKind::Function(ref f) => match f.kind() {
+                FunctionKind::Function => cc.functions(),
+                FunctionKind::Method(MethodKind::Constructor) => {
+                    cc.constructors()
+                }
+                FunctionKind::Method(MethodKind::Destructor) |
+                FunctionKind::Method(MethodKind::VirtualDestructor {
+                    ..
+                }) => cc.destructors(),
+                FunctionKind::Method(MethodKind::Static) |
+                FunctionKind::Method(MethodKind::Normal) |
+                FunctionKind::Method(MethodKind::Virtual { .. }) => {
+                    cc.methods()
+                }
+            },
+        }
+    }
+
+    /// Returns the path we should use for allowlisting / blocklisting, which
+    /// doesn't include user-mangling.
+    pub(crate) fn path_for_allowlisting(
+        &self,
+        ctx: &BindgenContext,
+    ) -> &Vec<String> {
+        self.path_for_allowlisting
+            .borrow_with(|| self.compute_path(ctx, UserMangled::No))
+    }
+
+    fn compute_path(
+        &self,
+        ctx: &BindgenContext,
+        mangled: UserMangled,
+    ) -> Vec<String> {
+        if let Some(path) = self.annotations().use_instead_of() {
+            let mut ret =
+                vec![ctx.resolve_item(ctx.root_module()).name(ctx).get()];
+            ret.extend_from_slice(path);
+            return ret;
+        }
+
+        let target = ctx.resolve_item(self.name_target(ctx));
+        let mut path: Vec<_> = target
+            .ancestors(ctx)
+            .chain(iter::once(ctx.root_module().into()))
+            .map(|id| ctx.resolve_item(id))
+            .filter(|item| {
+                item.id() == target.id() ||
+                    item.as_module().map_or(false, |module| {
+                        !module.is_inline() ||
+                            ctx.options().conservative_inline_namespaces
+                    })
+            })
+            .map(|item| {
+                ctx.resolve_item(item.name_target(ctx))
+                    .name(ctx)
+                    .within_namespaces()
+                    .user_mangled(mangled)
+                    .get()
+            })
+            .collect();
+        path.reverse();
+        path
+    }
+
+    /// Returns a prefix for the canonical name when C naming is enabled.
+    fn c_naming_prefix(&self) -> Option<&str> {
+        let ty = match self.kind {
+            ItemKind::Type(ref ty) => ty,
+            _ => return None,
+        };
+
+        Some(match ty.kind() {
+            TypeKind::Comp(ref ci) => match ci.kind() {
+                CompKind::Struct => "struct",
+                CompKind::Union => "union",
+            },
+            TypeKind::Enum(..) => "enum",
+            _ => return None,
+        })
+    }
+
+    /// Whether this is a `#[must_use]` type.
+    pub(crate) fn must_use(&self, ctx: &BindgenContext) -> bool {
+        self.annotations().must_use_type() || ctx.must_use_type_by_name(self)
+    }
+}
+
+impl<T> IsOpaque for T
+where
+    T: Copy + Into<ItemId>,
+{
+    type Extra = ();
+
+    fn is_opaque(&self, ctx: &BindgenContext, _: &()) -> bool {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.resolve_item((*self).into()).is_opaque(ctx, &())
+    }
+}
+
+impl IsOpaque for Item {
+    type Extra = ();
+
+    fn is_opaque(&self, ctx: &BindgenContext, _: &()) -> bool {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        self.annotations.opaque() ||
+            self.as_type().map_or(false, |ty| ty.is_opaque(ctx, self)) ||
+            ctx.opaque_by_name(self.path_for_allowlisting(ctx))
+    }
+}
+
+impl<T> HasVtable for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn has_vtable(&self, ctx: &BindgenContext) -> bool {
+        let id: ItemId = (*self).into();
+        id.as_type_id(ctx).map_or(false, |id| {
+            !matches!(ctx.lookup_has_vtable(id), HasVtableResult::No)
+        })
+    }
+
+    fn has_vtable_ptr(&self, ctx: &BindgenContext) -> bool {
+        let id: ItemId = (*self).into();
+        id.as_type_id(ctx).map_or(false, |id| {
+            matches!(ctx.lookup_has_vtable(id), HasVtableResult::SelfHasVtable)
+        })
+    }
+}
+
+impl HasVtable for Item {
+    fn has_vtable(&self, ctx: &BindgenContext) -> bool {
+        self.id().has_vtable(ctx)
+    }
+
+    fn has_vtable_ptr(&self, ctx: &BindgenContext) -> bool {
+        self.id().has_vtable_ptr(ctx)
+    }
+}
+
+impl<T> Sizedness for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn sizedness(&self, ctx: &BindgenContext) -> SizednessResult {
+        let id: ItemId = (*self).into();
+        id.as_type_id(ctx)
+            .map_or(SizednessResult::default(), |id| ctx.lookup_sizedness(id))
+    }
+}
+
+impl Sizedness for Item {
+    fn sizedness(&self, ctx: &BindgenContext) -> SizednessResult {
+        self.id().sizedness(ctx)
+    }
+}
+
+impl<T> HasTypeParamInArray for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn has_type_param_in_array(&self, ctx: &BindgenContext) -> bool {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.lookup_has_type_param_in_array(*self)
+    }
+}
+
+impl HasTypeParamInArray for Item {
+    fn has_type_param_in_array(&self, ctx: &BindgenContext) -> bool {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.lookup_has_type_param_in_array(self.id())
+    }
+}
+
+impl<T> HasFloat for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn has_float(&self, ctx: &BindgenContext) -> bool {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.lookup_has_float(*self)
+    }
+}
+
+impl HasFloat for Item {
+    fn has_float(&self, ctx: &BindgenContext) -> bool {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        ctx.lookup_has_float(self.id())
+    }
+}
+
+/// A set of items.
+pub(crate) type ItemSet = BTreeSet<ItemId>;
+
+impl DotAttributes for Item {
+    fn dot_attributes<W>(
+        &self,
+        ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        writeln!(
+            out,
+            "<tr><td>{:?}</td></tr>
+                       <tr><td>name</td><td>{}</td></tr>",
+            self.id,
+            self.name(ctx).get()
+        )?;
+
+        if self.is_opaque(ctx, &()) {
+            writeln!(out, "<tr><td>opaque</td><td>true</td></tr>")?;
+        }
+
+        self.kind.dot_attributes(ctx, out)
+    }
+}
+
+impl<T> TemplateParameters for T
+where
+    T: Copy + Into<ItemId>,
+{
+    fn self_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId> {
+        ctx.resolve_item_fallible(*self)
+            .map_or(vec![], |item| item.self_template_params(ctx))
+    }
+}
+
+impl TemplateParameters for Item {
+    fn self_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId> {
+        self.kind.self_template_params(ctx)
+    }
+}
+
+impl TemplateParameters for ItemKind {
+    fn self_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId> {
+        match *self {
+            ItemKind::Type(ref ty) => ty.self_template_params(ctx),
+            // If we start emitting bindings to explicitly instantiated
+            // functions, then we'll need to check ItemKind::Function for
+            // template params.
+            ItemKind::Function(_) | ItemKind::Module(_) | ItemKind::Var(_) => {
+                vec![]
+            }
+        }
+    }
+}
+
+// An utility function to handle recursing inside nested types.
+fn visit_child(
+    cur: clang::Cursor,
+    id: ItemId,
+    ty: &clang::Type,
+    parent_id: Option<ItemId>,
+    ctx: &mut BindgenContext,
+    result: &mut Result<TypeId, ParseError>,
+) -> clang_sys::CXChildVisitResult {
+    use clang_sys::*;
+    if result.is_ok() {
+        return CXChildVisit_Break;
+    }
+
+    *result = Item::from_ty_with_id(id, ty, cur, parent_id, ctx);
+
+    match *result {
+        Ok(..) => CXChildVisit_Break,
+        Err(ParseError::Recurse) => {
+            cur.visit(|c| visit_child(c, id, ty, parent_id, ctx, result));
+            CXChildVisit_Continue
+        }
+        Err(ParseError::Continue) => CXChildVisit_Continue,
+    }
+}
+
+impl Item {
+    /// Create a builtin type.
+    pub(crate) fn builtin_type(
+        kind: TypeKind,
+        is_const: bool,
+        ctx: &mut BindgenContext,
+    ) -> TypeId {
+        // Feel free to add more here, I'm just lazy.
+        match kind {
+            TypeKind::Void |
+            TypeKind::Int(..) |
+            TypeKind::Pointer(..) |
+            TypeKind::Float(..) => {}
+            _ => panic!("Unsupported builtin type"),
+        }
+
+        let ty = Type::new(None, None, kind, is_const);
+        let id = ctx.next_item_id();
+        let module = ctx.root_module().into();
+        ctx.add_item(
+            Item::new(id, None, None, module, ItemKind::Type(ty), None),
+            None,
+            None,
+        );
+        id.as_type_id_unchecked()
+    }
+
+    /// Parse this item from the given Clang cursor.
+    pub(crate) fn parse(
+        cursor: clang::Cursor,
+        parent_id: Option<ItemId>,
+        ctx: &mut BindgenContext,
+    ) -> Result<ItemId, ParseError> {
+        use crate::ir::var::Var;
+        use clang_sys::*;
+
+        if !cursor.is_valid() {
+            return Err(ParseError::Continue);
+        }
+
+        let comment = cursor.raw_comment();
+        let annotations = Annotations::new(&cursor);
+
+        let current_module = ctx.current_module().into();
+        let relevant_parent_id = parent_id.unwrap_or(current_module);
+
+        #[allow(clippy::missing_docs_in_private_items)]
+        macro_rules! try_parse {
+            ($what:ident) => {
+                match $what::parse(cursor, ctx) {
+                    Ok(ParseResult::New(item, declaration)) => {
+                        let id = ctx.next_item_id();
+
+                        ctx.add_item(
+                            Item::new(
+                                id,
+                                comment,
+                                annotations,
+                                relevant_parent_id,
+                                ItemKind::$what(item),
+                                Some(cursor.location()),
+                            ),
+                            declaration,
+                            Some(cursor),
+                        );
+                        return Ok(id);
+                    }
+                    Ok(ParseResult::AlreadyResolved(id)) => {
+                        return Ok(id);
+                    }
+                    Err(ParseError::Recurse) => return Err(ParseError::Recurse),
+                    Err(ParseError::Continue) => {}
+                }
+            };
+        }
+
+        try_parse!(Module);
+
+        // NOTE: Is extremely important to parse functions and vars **before**
+        // types.  Otherwise we can parse a function declaration as a type
+        // (which is legal), and lose functions to generate.
+        //
+        // In general, I'm not totally confident this split between
+        // ItemKind::Function and TypeKind::FunctionSig is totally worth it, but
+        // I guess we can try.
+        try_parse!(Function);
+        try_parse!(Var);
+
+        // Types are sort of special, so to avoid parsing template classes
+        // twice, handle them separately.
+        {
+            let definition = cursor.definition();
+            let applicable_cursor = definition.unwrap_or(cursor);
+
+            let relevant_parent_id = match definition {
+                Some(definition) => {
+                    if definition != cursor {
+                        ctx.add_semantic_parent(definition, relevant_parent_id);
+                        return Ok(Item::from_ty_or_ref(
+                            applicable_cursor.cur_type(),
+                            cursor,
+                            parent_id,
+                            ctx,
+                        )
+                        .into());
+                    }
+                    ctx.known_semantic_parent(definition)
+                        .or(parent_id)
+                        .unwrap_or_else(|| ctx.current_module().into())
+                }
+                None => relevant_parent_id,
+            };
+
+            match Item::from_ty(
+                &applicable_cursor.cur_type(),
+                applicable_cursor,
+                Some(relevant_parent_id),
+                ctx,
+            ) {
+                Ok(ty) => return Ok(ty.into()),
+                Err(ParseError::Recurse) => return Err(ParseError::Recurse),
+                Err(ParseError::Continue) => {}
+            }
+        }
+
+        match cursor.kind() {
+            // On Clang 18+, extern "C" is reported accurately as a LinkageSpec.
+            // Older LLVM treat it as UnexposedDecl.
+            CXCursor_LinkageSpec | CXCursor_UnexposedDecl => {
+                Err(ParseError::Recurse)
+            }
+
+            // We allowlist cursors here known to be unhandled, to prevent being
+            // too noisy about this.
+            CXCursor_MacroDefinition |
+            CXCursor_MacroExpansion |
+            CXCursor_UsingDeclaration |
+            CXCursor_UsingDirective |
+            CXCursor_StaticAssert |
+            CXCursor_FunctionTemplate => {
+                debug!(
+                    "Unhandled cursor kind {:?}: {:?}",
+                    cursor.kind(),
+                    cursor
+                );
+                Err(ParseError::Continue)
+            }
+
+            CXCursor_InclusionDirective => {
+                let file = cursor.get_included_file_name();
+                match file {
+                    None => {
+                        warn!("Inclusion of a nameless file in {:?}", cursor);
+                    }
+                    Some(included_file) => {
+                        for cb in &ctx.options().parse_callbacks {
+                            cb.include_file(&included_file);
+                        }
+
+                        ctx.add_dep(included_file.into_boxed_str());
+                    }
+                }
+                Err(ParseError::Continue)
+            }
+
+            _ => {
+                // ignore toplevel operator overloads
+                let spelling = cursor.spelling();
+                if !spelling.starts_with("operator") {
+                    warn!(
+                        "Unhandled cursor kind {:?}: {:?}",
+                        cursor.kind(),
+                        cursor
+                    );
+                }
+                Err(ParseError::Continue)
+            }
+        }
+    }
+
+    /// Parse this item from the given Clang type, or if we haven't resolved all
+    /// the other items this one depends on, an unresolved reference.
+    pub(crate) fn from_ty_or_ref(
+        ty: clang::Type,
+        location: clang::Cursor,
+        parent_id: Option<ItemId>,
+        ctx: &mut BindgenContext,
+    ) -> TypeId {
+        let id = ctx.next_item_id();
+        Self::from_ty_or_ref_with_id(id, ty, location, parent_id, ctx)
+    }
+
+    /// Parse a C++ type. If we find a reference to a type that has not been
+    /// defined yet, use `UnresolvedTypeRef` as a placeholder.
+    ///
+    /// This logic is needed to avoid parsing items with the incorrect parent
+    /// and it's sort of complex to explain, so I'll just point to
+    /// `tests/headers/typeref.hpp` to see the kind of constructs that forced
+    /// this.
+    ///
+    /// Typerefs are resolved once parsing is completely done, see
+    /// `BindgenContext::resolve_typerefs`.
+    pub(crate) fn from_ty_or_ref_with_id(
+        potential_id: ItemId,
+        ty: clang::Type,
+        location: clang::Cursor,
+        parent_id: Option<ItemId>,
+        ctx: &mut BindgenContext,
+    ) -> TypeId {
+        debug!(
+            "from_ty_or_ref_with_id: {:?} {:?}, {:?}, {:?}",
+            potential_id, ty, location, parent_id
+        );
+
+        if ctx.collected_typerefs() {
+            debug!("refs already collected, resolving directly");
+            return Item::from_ty_with_id(
+                potential_id,
+                &ty,
+                location,
+                parent_id,
+                ctx,
+            )
+            .unwrap_or_else(|_| Item::new_opaque_type(potential_id, &ty, ctx));
+        }
+
+        if let Some(ty) = ctx.builtin_or_resolved_ty(
+            potential_id,
+            parent_id,
+            &ty,
+            Some(location),
+        ) {
+            debug!("{:?} already resolved: {:?}", ty, location);
+            return ty;
+        }
+
+        debug!("New unresolved type reference: {:?}, {:?}", ty, location);
+
+        let is_const = ty.is_const();
+        let kind = TypeKind::UnresolvedTypeRef(ty, location, parent_id);
+        let current_module = ctx.current_module();
+
+        ctx.add_item(
+            Item::new(
+                potential_id,
+                None,
+                None,
+                parent_id.unwrap_or_else(|| current_module.into()),
+                ItemKind::Type(Type::new(None, None, kind, is_const)),
+                Some(location.location()),
+            ),
+            None,
+            None,
+        );
+        potential_id.as_type_id_unchecked()
+    }
+
+    /// Parse this item from the given Clang type. See [`Item::from_ty_with_id`].
+    pub(crate) fn from_ty(
+        ty: &clang::Type,
+        location: clang::Cursor,
+        parent_id: Option<ItemId>,
+        ctx: &mut BindgenContext,
+    ) -> Result<TypeId, ParseError> {
+        let id = ctx.next_item_id();
+        Item::from_ty_with_id(id, ty, location, parent_id, ctx)
+    }
+
+    /// This is one of the trickiest methods you'll find (probably along with
+    /// some of the ones that handle templates in `BindgenContext`).
+    ///
+    /// This method parses a type, given the potential ID of that type (if
+    /// parsing it was correct), an optional location we're scanning, which is
+    /// critical some times to obtain information, an optional parent item ID,
+    /// that will, if it's `None`, become the current module ID, and the
+    /// context.
+    pub(crate) fn from_ty_with_id(
+        id: ItemId,
+        ty: &clang::Type,
+        location: clang::Cursor,
+        parent_id: Option<ItemId>,
+        ctx: &mut BindgenContext,
+    ) -> Result<TypeId, ParseError> {
+        use clang_sys::*;
+
+        debug!(
+            "Item::from_ty_with_id: {:?}\n\
+             \tty = {:?},\n\
+             \tlocation = {:?}",
+            id, ty, location
+        );
+
+        if ty.kind() == clang_sys::CXType_Unexposed ||
+            location.cur_type().kind() == clang_sys::CXType_Unexposed
+        {
+            if ty.is_associated_type() ||
+                location.cur_type().is_associated_type()
+            {
+                return Ok(Item::new_opaque_type(id, ty, ctx));
+            }
+
+            if let Some(param_id) = Item::type_param(None, location, ctx) {
+                return Ok(ctx.build_ty_wrapper(id, param_id, None, ty));
+            }
+        }
+
+        // Treat all types that are declared inside functions as opaque. The Rust binding
+        // won't be able to do anything with them anyway.
+        //
+        // (If we don't do this check here, we can have subtle logic bugs because we generally
+        // ignore function bodies. See issue #2036.)
+        if let Some(ref parent) = ty.declaration().fallible_semantic_parent() {
+            if FunctionKind::from_cursor(parent).is_some() {
+                debug!("Skipping type declared inside function: {:?}", ty);
+                return Ok(Item::new_opaque_type(id, ty, ctx));
+            }
+        }
+
+        let decl = {
+            let canonical_def = ty.canonical_type().declaration().definition();
+            canonical_def.unwrap_or_else(|| ty.declaration())
+        };
+
+        let comment = location
+            .raw_comment()
+            .or_else(|| decl.raw_comment())
+            .or_else(|| location.raw_comment());
+
+        let annotations =
+            Annotations::new(&decl).or_else(|| Annotations::new(&location));
+
+        if let Some(ref annotations) = annotations {
+            if let Some(replaced) = annotations.use_instead_of() {
+                ctx.replace(replaced, id);
+            }
+        }
+
+        if let Some(ty) =
+            ctx.builtin_or_resolved_ty(id, parent_id, ty, Some(location))
+        {
+            return Ok(ty);
+        }
+
+        // First, check we're not recursing.
+        let mut valid_decl = decl.kind() != CXCursor_NoDeclFound;
+        let declaration_to_look_for = if valid_decl {
+            decl.canonical()
+        } else if location.kind() == CXCursor_ClassTemplate {
+            valid_decl = true;
+            location
+        } else {
+            decl
+        };
+
+        if valid_decl {
+            if let Some(partial) = ctx
+                .currently_parsed_types()
+                .iter()
+                .find(|ty| *ty.decl() == declaration_to_look_for)
+            {
+                debug!("Avoiding recursion parsing type: {:?}", ty);
+                // Unchecked because we haven't finished this type yet.
+                return Ok(partial.id().as_type_id_unchecked());
+            }
+        }
+
+        let current_module = ctx.current_module().into();
+        let partial_ty = PartialType::new(declaration_to_look_for, id);
+        if valid_decl {
+            ctx.begin_parsing(partial_ty);
+        }
+
+        let result = Type::from_clang_ty(id, ty, location, parent_id, ctx);
+        let relevant_parent_id = parent_id.unwrap_or(current_module);
+        let ret = match result {
+            Ok(ParseResult::AlreadyResolved(ty)) => {
+                Ok(ty.as_type_id_unchecked())
+            }
+            Ok(ParseResult::New(item, declaration)) => {
+                ctx.add_item(
+                    Item::new(
+                        id,
+                        comment,
+                        annotations,
+                        relevant_parent_id,
+                        ItemKind::Type(item),
+                        Some(location.location()),
+                    ),
+                    declaration,
+                    Some(location),
+                );
+                Ok(id.as_type_id_unchecked())
+            }
+            Err(ParseError::Continue) => Err(ParseError::Continue),
+            Err(ParseError::Recurse) => {
+                debug!("Item::from_ty recursing in the ast");
+                let mut result = Err(ParseError::Recurse);
+
+                // Need to pop here, otherwise we'll get stuck.
+                //
+                // TODO: Find a nicer interface, really. Also, the
+                // declaration_to_look_for suspiciously shares a lot of
+                // logic with ir::context, so we should refactor that.
+                if valid_decl {
+                    let finished = ctx.finish_parsing();
+                    assert_eq!(*finished.decl(), declaration_to_look_for);
+                }
+
+                location.visit(|cur| {
+                    visit_child(cur, id, ty, parent_id, ctx, &mut result)
+                });
+
+                if valid_decl {
+                    let partial_ty =
+                        PartialType::new(declaration_to_look_for, id);
+                    ctx.begin_parsing(partial_ty);
+                }
+
+                // If we have recursed into the AST all we know, and we still
+                // haven't found what we've got, let's just try and make a named
+                // type.
+                //
+                // This is what happens with some template members, for example.
+                if let Err(ParseError::Recurse) = result {
+                    warn!(
+                        "Unknown type, assuming named template type: \
+                         id = {:?}; spelling = {}",
+                        id,
+                        ty.spelling()
+                    );
+                    Item::type_param(Some(id), location, ctx)
+                        .map(Ok)
+                        .unwrap_or(Err(ParseError::Recurse))
+                } else {
+                    result
+                }
+            }
+        };
+
+        if valid_decl {
+            let partial_ty = ctx.finish_parsing();
+            assert_eq!(*partial_ty.decl(), declaration_to_look_for);
+        }
+
+        ret
+    }
+
+    /// A named type is a template parameter, e.g., the `T` in `Foo<T>`. They're always local so
+    /// it's the only exception when there's no declaration for a type.
+    pub(crate) fn type_param(
+        with_id: Option<ItemId>,
+        location: clang::Cursor,
+        ctx: &mut BindgenContext,
+    ) -> Option<TypeId> {
+        let ty = location.cur_type();
+
+        debug!(
+            "Item::type_param:\n\
+             \twith_id = {:?},\n\
+             \tty = {} {:?},\n\
+             \tlocation: {:?}",
+            with_id,
+            ty.spelling(),
+            ty,
+            location
+        );
+
+        if ty.kind() != clang_sys::CXType_Unexposed {
+            // If the given cursor's type's kind is not Unexposed, then we
+            // aren't looking at a template parameter. This check may need to be
+            // updated in the future if they start properly exposing template
+            // type parameters.
+            return None;
+        }
+
+        let ty_spelling = ty.spelling();
+
+        // Clang does not expose any information about template type parameters
+        // via their clang::Type, nor does it give us their canonical cursors
+        // the straightforward way. However, there are three situations from
+        // which we can find the definition of the template type parameter, if
+        // the cursor is indeed looking at some kind of a template type
+        // parameter or use of one:
+        //
+        // 1. The cursor is pointing at the template type parameter's
+        // definition. This is the trivial case.
+        //
+        //     (kind = TemplateTypeParameter, ...)
+        //
+        // 2. The cursor is pointing at a TypeRef whose referenced() cursor is
+        // situation (1).
+        //
+        //     (kind = TypeRef,
+        //      referenced = (kind = TemplateTypeParameter, ...),
+        //      ...)
+        //
+        // 3. The cursor is pointing at some use of a template type parameter
+        // (for example, in a FieldDecl), and this cursor has a child cursor
+        // whose spelling is the same as the parent's type's spelling, and whose
+        // kind is a TypeRef of the situation (2) variety.
+        //
+        //    (kind = FieldDecl,
+        //     type = (kind = Unexposed,
+        //             spelling = "T",
+        //             ...),
+        //     children =
+        //        (kind = TypeRef,
+        //         spelling = "T",
+        //         referenced = (kind = TemplateTypeParameter,
+        //                       spelling = "T",
+        //                       ...),
+        //         ...)
+        //     ...)
+        //
+        // TODO: The alternative to this hacky pattern matching would be to
+        // maintain proper scopes of template parameters while parsing and use
+        // de Brujin indices to access template parameters, which clang exposes
+        // in the cursor's type's canonical type's spelling:
+        // "type-parameter-x-y". That is probably a better approach long-term,
+        // but maintaining these scopes properly would require more changes to
+        // the whole libclang -> IR parsing code.
+
+        fn is_template_with_spelling(
+            refd: &clang::Cursor,
+            spelling: &str,
+        ) -> bool {
+            lazy_static! {
+                static ref ANON_TYPE_PARAM_RE: regex::Regex =
+                    regex::Regex::new(r"^type\-parameter\-\d+\-\d+$").unwrap();
+            }
+
+            if refd.kind() != clang_sys::CXCursor_TemplateTypeParameter {
+                return false;
+            }
+
+            let refd_spelling = refd.spelling();
+            refd_spelling == spelling ||
+                // Allow for anonymous template parameters.
+                (refd_spelling.is_empty() && ANON_TYPE_PARAM_RE.is_match(spelling.as_ref()))
+        }
+
+        let definition = if is_template_with_spelling(&location, &ty_spelling) {
+            // Situation (1)
+            location
+        } else if location.kind() == clang_sys::CXCursor_TypeRef {
+            // Situation (2)
+            match location.referenced() {
+                Some(refd)
+                    if is_template_with_spelling(&refd, &ty_spelling) =>
+                {
+                    refd
+                }
+                _ => return None,
+            }
+        } else {
+            // Situation (3)
+            let mut definition = None;
+
+            location.visit(|child| {
+                let child_ty = child.cur_type();
+                if child_ty.kind() == clang_sys::CXCursor_TypeRef &&
+                    child_ty.spelling() == ty_spelling
+                {
+                    match child.referenced() {
+                        Some(refd)
+                            if is_template_with_spelling(
+                                &refd,
+                                &ty_spelling,
+                            ) =>
+                        {
+                            definition = Some(refd);
+                            return clang_sys::CXChildVisit_Break;
+                        }
+                        _ => {}
+                    }
+                }
+
+                clang_sys::CXChildVisit_Continue
+            });
+
+            definition?
+        };
+        assert!(is_template_with_spelling(&definition, &ty_spelling));
+
+        // Named types are always parented to the root module. They are never
+        // referenced with namespace prefixes, and they can't inherit anything
+        // from their parent either, so it is simplest to just hang them off
+        // something we know will always exist.
+        let parent = ctx.root_module().into();
+
+        if let Some(id) = ctx.get_type_param(&definition) {
+            if let Some(with_id) = with_id {
+                return Some(ctx.build_ty_wrapper(
+                    with_id,
+                    id,
+                    Some(parent),
+                    &ty,
+                ));
+            } else {
+                return Some(id);
+            }
+        }
+
+        // See tests/headers/const_tparam.hpp and
+        // tests/headers/variadic_tname.hpp.
+        let name = ty_spelling.replace("const ", "").replace('.', "");
+
+        let id = with_id.unwrap_or_else(|| ctx.next_item_id());
+        let item = Item::new(
+            id,
+            None,
+            None,
+            parent,
+            ItemKind::Type(Type::named(name)),
+            Some(location.location()),
+        );
+        ctx.add_type_param(item, definition);
+        Some(id.as_type_id_unchecked())
+    }
+}
+
+impl ItemCanonicalName for Item {
+    fn canonical_name(&self, ctx: &BindgenContext) -> String {
+        debug_assert!(
+            ctx.in_codegen_phase(),
+            "You're not supposed to call this yet"
+        );
+        self.canonical_name
+            .borrow_with(|| {
+                let in_namespace = ctx.options().enable_cxx_namespaces ||
+                    ctx.options().disable_name_namespacing;
+
+                if in_namespace {
+                    self.name(ctx).within_namespaces().get()
+                } else {
+                    self.name(ctx).get()
+                }
+            })
+            .clone()
+    }
+}
+
+impl ItemCanonicalPath for Item {
+    fn namespace_aware_canonical_path(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Vec<String> {
+        let mut path = self.canonical_path(ctx);
+
+        // ASSUMPTION: (disable_name_namespacing && cxx_namespaces)
+        // is equivalent to
+        // disable_name_namespacing
+        if ctx.options().disable_name_namespacing {
+            // Only keep the last item in path
+            let split_idx = path.len() - 1;
+            path = path.split_off(split_idx);
+        } else if !ctx.options().enable_cxx_namespaces {
+            // Ignore first item "root"
+            path = vec![path[1..].join("_")];
+        }
+
+        if self.is_constified_enum_module(ctx) {
+            path.push(CONSTIFIED_ENUM_MODULE_REPR_NAME.into());
+        }
+
+        path
+    }
+
+    fn canonical_path(&self, ctx: &BindgenContext) -> Vec<String> {
+        self.compute_path(ctx, UserMangled::Yes)
+    }
+}
+
+/// Whether to use the user-mangled name (mangled by the `item_name` callback or
+/// not.
+///
+/// Most of the callers probably want just yes, but the ones dealing with
+/// allowlisting and blocklisting don't.
+#[derive(Copy, Clone, Debug, PartialEq)]
+enum UserMangled {
+    No,
+    Yes,
+}
+
+/// Builder struct for naming variations, which hold inside different
+/// flags for naming options.
+#[derive(Debug)]
+pub(crate) struct NameOptions<'a> {
+    item: &'a Item,
+    ctx: &'a BindgenContext,
+    within_namespaces: bool,
+    user_mangled: UserMangled,
+}
+
+impl<'a> NameOptions<'a> {
+    /// Construct a new `NameOptions`
+    pub(crate) fn new(item: &'a Item, ctx: &'a BindgenContext) -> Self {
+        NameOptions {
+            item,
+            ctx,
+            within_namespaces: false,
+            user_mangled: UserMangled::Yes,
+        }
+    }
+
+    /// Construct the name without the item's containing C++ namespaces mangled
+    /// into it. In other words, the item's name within the item's namespace.
+    pub(crate) fn within_namespaces(&mut self) -> &mut Self {
+        self.within_namespaces = true;
+        self
+    }
+
+    fn user_mangled(&mut self, user_mangled: UserMangled) -> &mut Self {
+        self.user_mangled = user_mangled;
+        self
+    }
+
+    /// Construct a name `String`
+    pub(crate) fn get(&self) -> String {
+        self.item.real_canonical_name(self.ctx, self)
+    }
+}
diff --git a/third_party/rust/bindgen/ir/item_kind.rs b/third_party/rust/bindgen/ir/item_kind.rs
new file mode 100644
index 0000000000..e8618498ad
--- /dev/null
+++ b/third_party/rust/bindgen/ir/item_kind.rs
@@ -0,0 +1,135 @@
+//! Different variants of an `Item` in our intermediate representation.
+
+use super::context::BindgenContext;
+use super::dot::DotAttributes;
+use super::function::Function;
+use super::module::Module;
+use super::ty::Type;
+use super::var::Var;
+use std::io;
+
+/// A item we parse and translate.
+#[derive(Debug)]
+pub(crate) enum ItemKind {
+    /// A module, created implicitly once (the root module), or via C++
+    /// namespaces.
+    Module(Module),
+
+    /// A type declared in any of the multiple ways it can be declared.
+    Type(Type),
+
+    /// A function or method declaration.
+    Function(Function),
+
+    /// A variable declaration, most likely a static.
+    Var(Var),
+}
+
+impl ItemKind {
+    /// Get a reference to this `ItemKind`'s underying `Module`, or `None` if it
+    /// is some other kind.
+    pub(crate) fn as_module(&self) -> Option<&Module> {
+        match *self {
+            ItemKind::Module(ref module) => Some(module),
+            _ => None,
+        }
+    }
+
+    /// Transform our `ItemKind` into a string.
+    pub(crate) fn kind_name(&self) -> &'static str {
+        match *self {
+            ItemKind::Module(..) => "Module",
+            ItemKind::Type(..) => "Type",
+            ItemKind::Function(..) => "Function",
+            ItemKind::Var(..) => "Var",
+        }
+    }
+
+    /// Is this a module?
+    pub(crate) fn is_module(&self) -> bool {
+        self.as_module().is_some()
+    }
+
+    /// Get a reference to this `ItemKind`'s underying `Function`, or `None` if
+    /// it is some other kind.
+    pub(crate) fn as_function(&self) -> Option<&Function> {
+        match *self {
+            ItemKind::Function(ref func) => Some(func),
+            _ => None,
+        }
+    }
+
+    /// Is this a function?
+    pub(crate) fn is_function(&self) -> bool {
+        self.as_function().is_some()
+    }
+
+    /// Get a reference to this `ItemKind`'s underying `Function`, or panic if
+    /// it is some other kind.
+    pub(crate) fn expect_function(&self) -> &Function {
+        self.as_function().expect("Not a function")
+    }
+
+    /// Get a reference to this `ItemKind`'s underying `Type`, or `None` if
+    /// it is some other kind.
+    pub(crate) fn as_type(&self) -> Option<&Type> {
+        match *self {
+            ItemKind::Type(ref ty) => Some(ty),
+            _ => None,
+        }
+    }
+
+    /// Get a mutable reference to this `ItemKind`'s underying `Type`, or `None`
+    /// if it is some other kind.
+    pub(crate) fn as_type_mut(&mut self) -> Option<&mut Type> {
+        match *self {
+            ItemKind::Type(ref mut ty) => Some(ty),
+            _ => None,
+        }
+    }
+
+    /// Is this a type?
+    pub(crate) fn is_type(&self) -> bool {
+        self.as_type().is_some()
+    }
+
+    /// Get a reference to this `ItemKind`'s underying `Type`, or panic if it is
+    /// some other kind.
+    pub(crate) fn expect_type(&self) -> &Type {
+        self.as_type().expect("Not a type")
+    }
+
+    /// Get a reference to this `ItemKind`'s underying `Var`, or `None` if it is
+    /// some other kind.
+    pub(crate) fn as_var(&self) -> Option<&Var> {
+        match *self {
+            ItemKind::Var(ref v) => Some(v),
+            _ => None,
+        }
+    }
+
+    /// Is this a variable?
+    pub(crate) fn is_var(&self) -> bool {
+        self.as_var().is_some()
+    }
+}
+
+impl DotAttributes for ItemKind {
+    fn dot_attributes<W>(
+        &self,
+        ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        writeln!(out, "<tr><td>kind</td><td>{}</td></tr>", self.kind_name())?;
+
+        match *self {
+            ItemKind::Module(ref module) => module.dot_attributes(ctx, out),
+            ItemKind::Type(ref ty) => ty.dot_attributes(ctx, out),
+            ItemKind::Function(ref func) => func.dot_attributes(ctx, out),
+            ItemKind::Var(ref var) => var.dot_attributes(ctx, out),
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/ir/layout.rs b/third_party/rust/bindgen/ir/layout.rs
new file mode 100644
index 0000000000..85a553da31
--- /dev/null
+++ b/third_party/rust/bindgen/ir/layout.rs
@@ -0,0 +1,138 @@
+//! Intermediate representation for the physical layout of some type.
+
+use super::derive::CanDerive;
+use super::ty::{Type, TypeKind, RUST_DERIVE_IN_ARRAY_LIMIT};
+use crate::clang;
+use crate::ir::context::BindgenContext;
+use std::cmp;
+
+/// A type that represents the struct layout of a type.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) struct Layout {
+    /// The size (in bytes) of this layout.
+    pub(crate) size: usize,
+    /// The alignment (in bytes) of this layout.
+    pub(crate) align: usize,
+    /// Whether this layout's members are packed or not.
+    pub(crate) packed: bool,
+}
+
+#[test]
+fn test_layout_for_size() {
+    use std::mem;
+
+    let ptr_size = mem::size_of::<*mut ()>();
+    assert_eq!(
+        Layout::for_size_internal(ptr_size, ptr_size),
+        Layout::new(ptr_size, ptr_size)
+    );
+    assert_eq!(
+        Layout::for_size_internal(ptr_size, 3 * ptr_size),
+        Layout::new(3 * ptr_size, ptr_size)
+    );
+}
+
+impl Layout {
+    /// Gets the integer type name for a given known size.
+    pub(crate) fn known_type_for_size(
+        ctx: &BindgenContext,
+        size: usize,
+    ) -> Option<syn::Type> {
+        Some(match size {
+            16 if ctx.options().rust_features.i128_and_u128 => {
+                syn::parse_quote! { u128 }
+            }
+            8 => syn::parse_quote! { u64 },
+            4 => syn::parse_quote! { u32 },
+            2 => syn::parse_quote! { u16 },
+            1 => syn::parse_quote! { u8 },
+            _ => return None,
+        })
+    }
+
+    /// Construct a new `Layout` with the given `size` and `align`. It is not
+    /// packed.
+    pub(crate) fn new(size: usize, align: usize) -> Self {
+        Layout {
+            size,
+            align,
+            packed: false,
+        }
+    }
+
+    fn for_size_internal(ptr_size: usize, size: usize) -> Self {
+        let mut next_align = 2;
+        while size % next_align == 0 && next_align <= ptr_size {
+            next_align *= 2;
+        }
+        Layout {
+            size,
+            align: next_align / 2,
+            packed: false,
+        }
+    }
+
+    /// Creates a non-packed layout for a given size, trying to use the maximum
+    /// alignment possible.
+    pub(crate) fn for_size(ctx: &BindgenContext, size: usize) -> Self {
+        Self::for_size_internal(ctx.target_pointer_size(), size)
+    }
+
+    /// Get this layout as an opaque type.
+    pub(crate) fn opaque(&self) -> Opaque {
+        Opaque(*self)
+    }
+}
+
+/// When we are treating a type as opaque, it is just a blob with a `Layout`.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) struct Opaque(pub(crate) Layout);
+
+impl Opaque {
+    /// Construct a new opaque type from the given clang type.
+    pub(crate) fn from_clang_ty(
+        ty: &clang::Type,
+        ctx: &BindgenContext,
+    ) -> Type {
+        let layout = Layout::new(ty.size(ctx), ty.align(ctx));
+        let ty_kind = TypeKind::Opaque;
+        let is_const = ty.is_const();
+        Type::new(None, Some(layout), ty_kind, is_const)
+    }
+
+    /// Return the known rust type we should use to create a correctly-aligned
+    /// field with this layout.
+    pub(crate) fn known_rust_type_for_array(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Option<syn::Type> {
+        Layout::known_type_for_size(ctx, self.0.align)
+    }
+
+    /// Return the array size that an opaque type for this layout should have if
+    /// we know the correct type for it, or `None` otherwise.
+    pub(crate) fn array_size(&self, ctx: &BindgenContext) -> Option<usize> {
+        if self.known_rust_type_for_array(ctx).is_some() {
+            Some(self.0.size / cmp::max(self.0.align, 1))
+        } else {
+            None
+        }
+    }
+
+    /// Return `true` if this opaque layout's array size will fit within the
+    /// maximum number of array elements that Rust allows deriving traits
+    /// with. Return `false` otherwise.
+    pub(crate) fn array_size_within_derive_limit(
+        &self,
+        ctx: &BindgenContext,
+    ) -> CanDerive {
+        if self
+            .array_size(ctx)
+            .map_or(false, |size| size <= RUST_DERIVE_IN_ARRAY_LIMIT)
+        {
+            CanDerive::Yes
+        } else {
+            CanDerive::Manually
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/ir/mod.rs b/third_party/rust/bindgen/ir/mod.rs
new file mode 100644
index 0000000000..acdb4896cd
--- /dev/null
+++ b/third_party/rust/bindgen/ir/mod.rs
@@ -0,0 +1,25 @@
+//! The ir module defines bindgen's intermediate representation.
+//!
+//! Parsing C/C++ generates the IR, while code generation outputs Rust code from
+//! the IR.
+#![deny(clippy::missing_docs_in_private_items)]
+
+pub(crate) mod analysis;
+pub(crate) mod annotations;
+pub(crate) mod comment;
+pub(crate) mod comp;
+pub(crate) mod context;
+pub(crate) mod derive;
+pub(crate) mod dot;
+pub(crate) mod enum_ty;
+pub(crate) mod function;
+pub(crate) mod int;
+pub(crate) mod item;
+pub(crate) mod item_kind;
+pub(crate) mod layout;
+pub(crate) mod module;
+pub(crate) mod objc;
+pub(crate) mod template;
+pub(crate) mod traversal;
+pub(crate) mod ty;
+pub(crate) mod var;
diff --git a/third_party/rust/bindgen/ir/module.rs b/third_party/rust/bindgen/ir/module.rs
new file mode 100644
index 0000000000..5ec55e9048
--- /dev/null
+++ b/third_party/rust/bindgen/ir/module.rs
@@ -0,0 +1,96 @@
+//! Intermediate representation for modules (AKA C++ namespaces).
+
+use super::context::BindgenContext;
+use super::dot::DotAttributes;
+use super::item::ItemSet;
+use crate::clang;
+use crate::parse::{ClangSubItemParser, ParseError, ParseResult};
+use crate::parse_one;
+
+use std::io;
+
+/// Whether this module is inline or not.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum ModuleKind {
+    /// This module is not inline.
+    Normal,
+    /// This module is inline, as in `inline namespace foo {}`.
+    Inline,
+}
+
+/// A module, as in, a C++ namespace.
+#[derive(Clone, Debug)]
+pub(crate) struct Module {
+    /// The name of the module, or none if it's anonymous.
+    name: Option<String>,
+    /// The kind of module this is.
+    kind: ModuleKind,
+    /// The children of this module, just here for convenience.
+    children: ItemSet,
+}
+
+impl Module {
+    /// Construct a new `Module`.
+    pub(crate) fn new(name: Option<String>, kind: ModuleKind) -> Self {
+        Module {
+            name,
+            kind,
+            children: ItemSet::new(),
+        }
+    }
+
+    /// Get this module's name.
+    pub(crate) fn name(&self) -> Option<&str> {
+        self.name.as_deref()
+    }
+
+    /// Get a mutable reference to this module's children.
+    pub(crate) fn children_mut(&mut self) -> &mut ItemSet {
+        &mut self.children
+    }
+
+    /// Get this module's children.
+    pub(crate) fn children(&self) -> &ItemSet {
+        &self.children
+    }
+
+    /// Whether this namespace is inline.
+    pub(crate) fn is_inline(&self) -> bool {
+        self.kind == ModuleKind::Inline
+    }
+}
+
+impl DotAttributes for Module {
+    fn dot_attributes<W>(
+        &self,
+        _ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        writeln!(out, "<tr><td>ModuleKind</td><td>{:?}</td></tr>", self.kind)
+    }
+}
+
+impl ClangSubItemParser for Module {
+    fn parse(
+        cursor: clang::Cursor,
+        ctx: &mut BindgenContext,
+    ) -> Result<ParseResult<Self>, ParseError> {
+        use clang_sys::*;
+        match cursor.kind() {
+            CXCursor_Namespace => {
+                let module_id = ctx.module(cursor);
+                ctx.with_module(module_id, |ctx| {
+                    cursor.visit_sorted(ctx, |ctx, child| {
+                        parse_one(ctx, child, Some(module_id.into()))
+                    })
+                });
+
+                Ok(ParseResult::AlreadyResolved(module_id.into()))
+            }
+            _ => Err(ParseError::Continue),
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/ir/objc.rs b/third_party/rust/bindgen/ir/objc.rs
new file mode 100644
index 0000000000..93d8b3bfdf
--- /dev/null
+++ b/third_party/rust/bindgen/ir/objc.rs
@@ -0,0 +1,354 @@
+//! Objective C types
+
+use super::context::{BindgenContext, ItemId};
+use super::function::FunctionSig;
+use super::item::Item;
+use super::traversal::{Trace, Tracer};
+use super::ty::TypeKind;
+use crate::clang;
+use clang_sys::CXChildVisit_Continue;
+use clang_sys::CXCursor_ObjCCategoryDecl;
+use clang_sys::CXCursor_ObjCClassMethodDecl;
+use clang_sys::CXCursor_ObjCClassRef;
+use clang_sys::CXCursor_ObjCInstanceMethodDecl;
+use clang_sys::CXCursor_ObjCProtocolDecl;
+use clang_sys::CXCursor_ObjCProtocolRef;
+use clang_sys::CXCursor_ObjCSuperClassRef;
+use clang_sys::CXCursor_TemplateTypeParameter;
+use proc_macro2::{Ident, Span, TokenStream};
+
+/// Objective C interface as used in TypeKind
+///
+/// Also protocols and categories are parsed as this type
+#[derive(Debug)]
+pub(crate) struct ObjCInterface {
+    /// The name
+    /// like, NSObject
+    name: String,
+
+    category: Option<String>,
+
+    is_protocol: bool,
+
+    /// The list of template names almost always, ObjectType or KeyType
+    pub(crate) template_names: Vec<String>,
+
+    /// The list of protocols that this interface conforms to.
+    pub(crate) conforms_to: Vec<ItemId>,
+
+    /// The direct parent for this interface.
+    pub(crate) parent_class: Option<ItemId>,
+
+    /// List of the methods defined in this interfae
+    methods: Vec<ObjCMethod>,
+
+    class_methods: Vec<ObjCMethod>,
+}
+
+/// The objective c methods
+#[derive(Debug)]
+pub(crate) struct ObjCMethod {
+    /// The original method selector name
+    /// like, dataWithBytes:length:
+    name: String,
+
+    /// Method name as converted to rust
+    /// like, dataWithBytes_length_
+    rust_name: String,
+
+    signature: FunctionSig,
+
+    /// Is class method?
+    is_class_method: bool,
+}
+
+impl ObjCInterface {
+    fn new(name: &str) -> ObjCInterface {
+        ObjCInterface {
+            name: name.to_owned(),
+            category: None,
+            is_protocol: false,
+            template_names: Vec::new(),
+            parent_class: None,
+            conforms_to: Vec::new(),
+            methods: Vec::new(),
+            class_methods: Vec::new(),
+        }
+    }
+
+    /// The name
+    /// like, NSObject
+    pub(crate) fn name(&self) -> &str {
+        self.name.as_ref()
+    }
+
+    /// Formats the name for rust
+    /// Can be like NSObject, but with categories might be like NSObject_NSCoderMethods
+    /// and protocols are like PNSObject
+    pub(crate) fn rust_name(&self) -> String {
+        if let Some(ref cat) = self.category {
+            format!("{}_{}", self.name(), cat)
+        } else if self.is_protocol {
+            format!("P{}", self.name())
+        } else {
+            format!("I{}", self.name().to_owned())
+        }
+    }
+
+    /// Is this a template interface?
+    pub(crate) fn is_template(&self) -> bool {
+        !self.template_names.is_empty()
+    }
+
+    /// List of the methods defined in this interface
+    pub(crate) fn methods(&self) -> &Vec<ObjCMethod> {
+        &self.methods
+    }
+
+    /// Is this a protocol?
+    pub(crate) fn is_protocol(&self) -> bool {
+        self.is_protocol
+    }
+
+    /// Is this a category?
+    pub(crate) fn is_category(&self) -> bool {
+        self.category.is_some()
+    }
+
+    /// List of the class methods defined in this interface
+    pub(crate) fn class_methods(&self) -> &Vec<ObjCMethod> {
+        &self.class_methods
+    }
+
+    /// Parses the Objective C interface from the cursor
+    pub(crate) fn from_ty(
+        cursor: &clang::Cursor,
+        ctx: &mut BindgenContext,
+    ) -> Option<Self> {
+        let name = cursor.spelling();
+        let mut interface = Self::new(&name);
+
+        if cursor.kind() == CXCursor_ObjCProtocolDecl {
+            interface.is_protocol = true;
+        }
+
+        cursor.visit(|c| {
+            match c.kind() {
+                CXCursor_ObjCClassRef => {
+                    if cursor.kind() == CXCursor_ObjCCategoryDecl {
+                        // We are actually a category extension, and we found the reference
+                        // to the original interface, so name this interface approriately
+                        interface.name = c.spelling();
+                        interface.category = Some(cursor.spelling());
+                    }
+                }
+                CXCursor_ObjCProtocolRef => {
+                    // Gather protocols this interface conforms to
+                    let needle = format!("P{}", c.spelling());
+                    let items_map = ctx.items();
+                    debug!(
+                        "Interface {} conforms to {}, find the item",
+                        interface.name, needle
+                    );
+
+                    for (id, item) in items_map {
+                        if let Some(ty) = item.as_type() {
+                            if let TypeKind::ObjCInterface(ref protocol) =
+                                *ty.kind()
+                            {
+                                if protocol.is_protocol {
+                                    debug!(
+                                        "Checking protocol {}, ty.name {:?}",
+                                        protocol.name,
+                                        ty.name()
+                                    );
+                                    if Some(needle.as_ref()) == ty.name() {
+                                        debug!(
+                                            "Found conforming protocol {:?}",
+                                            item
+                                        );
+                                        interface.conforms_to.push(id);
+                                        break;
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                CXCursor_ObjCInstanceMethodDecl |
+                CXCursor_ObjCClassMethodDecl => {
+                    let name = c.spelling();
+                    let signature =
+                        FunctionSig::from_ty(&c.cur_type(), &c, ctx)
+                            .expect("Invalid function sig");
+                    let is_class_method =
+                        c.kind() == CXCursor_ObjCClassMethodDecl;
+                    let method =
+                        ObjCMethod::new(&name, signature, is_class_method);
+                    interface.add_method(method);
+                }
+                CXCursor_TemplateTypeParameter => {
+                    let name = c.spelling();
+                    interface.template_names.push(name);
+                }
+                CXCursor_ObjCSuperClassRef => {
+                    let item = Item::from_ty_or_ref(c.cur_type(), c, None, ctx);
+                    interface.parent_class = Some(item.into());
+                }
+                _ => {}
+            }
+            CXChildVisit_Continue
+        });
+        Some(interface)
+    }
+
+    fn add_method(&mut self, method: ObjCMethod) {
+        if method.is_class_method {
+            self.class_methods.push(method);
+        } else {
+            self.methods.push(method);
+        }
+    }
+}
+
+impl ObjCMethod {
+    fn new(
+        name: &str,
+        signature: FunctionSig,
+        is_class_method: bool,
+    ) -> ObjCMethod {
+        let split_name: Vec<&str> = name.split(':').collect();
+
+        let rust_name = split_name.join("_");
+
+        ObjCMethod {
+            name: name.to_owned(),
+            rust_name,
+            signature,
+            is_class_method,
+        }
+    }
+
+    /// Method name as converted to rust
+    /// like, dataWithBytes_length_
+    pub(crate) fn rust_name(&self) -> &str {
+        self.rust_name.as_ref()
+    }
+
+    /// Returns the methods signature as FunctionSig
+    pub(crate) fn signature(&self) -> &FunctionSig {
+        &self.signature
+    }
+
+    /// Is this a class method?
+    pub(crate) fn is_class_method(&self) -> bool {
+        self.is_class_method
+    }
+
+    /// Formats the method call
+    pub(crate) fn format_method_call(
+        &self,
+        args: &[TokenStream],
+    ) -> TokenStream {
+        let split_name: Vec<Option<Ident>> = self
+            .name
+            .split(':')
+            .enumerate()
+            .map(|(idx, name)| {
+                if name.is_empty() {
+                    None
+                } else if idx == 0 {
+                    // Try to parse the method name as an identifier. Having a keyword is ok
+                    // unless it is `crate`, `self`, `super` or `Self`, so we try to add the `_`
+                    // suffix to it and parse it.
+                    if ["crate", "self", "super", "Self"].contains(&name) {
+                        Some(Ident::new(
+                            &format!("{}_", name),
+                            Span::call_site(),
+                        ))
+                    } else {
+                        Some(Ident::new(name, Span::call_site()))
+                    }
+                } else {
+                    // Try to parse the current joining name as an identifier. This might fail if the name
+                    // is a keyword, so we try to  "r#" to it and parse again, this could also fail
+                    // if the name is `crate`, `self`, `super` or `Self`, so we try to add the `_`
+                    // suffix to it and parse again. If this also fails, we panic with the first
+                    // error.
+                    Some(
+                        syn::parse_str::<Ident>(name)
+                            .or_else(|err| {
+                                syn::parse_str::<Ident>(&format!("r#{}", name))
+                                    .map_err(|_| err)
+                            })
+                            .or_else(|err| {
+                                syn::parse_str::<Ident>(&format!("{}_", name))
+                                    .map_err(|_| err)
+                            })
+                            .expect("Invalid identifier"),
+                    )
+                }
+            })
+            .collect();
+
+        // No arguments
+        if args.is_empty() && split_name.len() == 1 {
+            let name = &split_name[0];
+            return quote! {
+                #name
+            };
+        }
+
+        // Check right amount of arguments
+        assert!(
+            args.len() == split_name.len() - 1,
+            "Incorrect method name or arguments for objc method, {:?} vs {:?}",
+            args,
+            split_name
+        );
+
+        // Get arguments without type signatures to pass to `msg_send!`
+        let mut args_without_types = vec![];
+        for arg in args.iter() {
+            let arg = arg.to_string();
+            let name_and_sig: Vec<&str> = arg.split(' ').collect();
+            let name = name_and_sig[0];
+            args_without_types.push(Ident::new(name, Span::call_site()))
+        }
+
+        let args = split_name.into_iter().zip(args_without_types).map(
+            |(arg, arg_val)| {
+                if let Some(arg) = arg {
+                    quote! { #arg: #arg_val }
+                } else {
+                    quote! { #arg_val: #arg_val }
+                }
+            },
+        );
+
+        quote! {
+            #( #args )*
+        }
+    }
+}
+
+impl Trace for ObjCInterface {
+    type Extra = ();
+
+    fn trace<T>(&self, context: &BindgenContext, tracer: &mut T, _: &())
+    where
+        T: Tracer,
+    {
+        for method in &self.methods {
+            method.signature.trace(context, tracer, &());
+        }
+
+        for class_method in &self.class_methods {
+            class_method.signature.trace(context, tracer, &());
+        }
+
+        for protocol in &self.conforms_to {
+            tracer.visit(*protocol);
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/ir/template.rs b/third_party/rust/bindgen/ir/template.rs
new file mode 100644
index 0000000000..4dd8442c58
--- /dev/null
+++ b/third_party/rust/bindgen/ir/template.rs
@@ -0,0 +1,342 @@
+//! Template declaration and instantiation related things.
+//!
+//! The nomenclature surrounding templates is often confusing, so here are a few
+//! brief definitions:
+//!
+//! * "Template definition": a class/struct/alias/function definition that takes
+//! generic template parameters. For example:
+//!
+//! ```c++
+//! template<typename T>
+//! class List<T> {
+//!     // ...
+//! };
+//! ```
+//!
+//! * "Template instantiation": an instantiation is a use of a template with
+//! concrete template arguments. For example, `List<int>`.
+//!
+//! * "Template specialization": an alternative template definition providing a
+//! custom definition for instantiations with the matching template
+//! arguments. This C++ feature is unsupported by bindgen. For example:
+//!
+//! ```c++
+//! template<>
+//! class List<int> {
+//!     // Special layout for int lists...
+//! };
+//! ```
+
+use super::context::{BindgenContext, ItemId, TypeId};
+use super::item::{IsOpaque, Item, ItemAncestors};
+use super::traversal::{EdgeKind, Trace, Tracer};
+use crate::clang;
+
+/// Template declaration (and such declaration's template parameters) related
+/// methods.
+///
+/// This trait's methods distinguish between `None` and `Some([])` for
+/// declarations that are not templates and template declarations with zero
+/// parameters, in general.
+///
+/// Consider this example:
+///
+/// ```c++
+/// template <typename T, typename U>
+/// class Foo {
+///     T use_of_t;
+///     U use_of_u;
+///
+///     template <typename V>
+///     using Bar = V*;
+///
+///     class Inner {
+///         T        x;
+///         U        y;
+///         Bar<int> z;
+///     };
+///
+///     template <typename W>
+///     class Lol {
+///         // No use of W, but here's a use of T.
+///         T t;
+///     };
+///
+///     template <typename X>
+///     class Wtf {
+///         // X is not used because W is not used.
+///         Lol<X> lololol;
+///     };
+/// };
+///
+/// class Qux {
+///     int y;
+/// };
+/// ```
+///
+/// The following table depicts the results of each trait method when invoked on
+/// each of the declarations above:
+///
+/// +------+----------------------+--------------------------+-------------------------+----
+/// |Decl. | self_template_params | num_self_template_params | all_template_parameters | ...
+/// +------+----------------------+--------------------------+-------------------------+----
+/// |Foo   | T, U                 | 2                        | T, U                    | ...
+/// |Bar   | V                    | 1                        | T, U, V                 | ...
+/// |Inner |                      | 0                        | T, U                    | ...
+/// |Lol   | W                    | 1                        | T, U, W                 | ...
+/// |Wtf   | X                    | 1                        | T, U, X                 | ...
+/// |Qux   |                      | 0                        |                         | ...
+/// +------+----------------------+--------------------------+------------------------+----
+///
+/// ----+------+-----+----------------------+
+/// ... |Decl. | ... | used_template_params |
+/// ----+------+-----+----------------------+
+/// ... |Foo   | ... | T, U                 |
+/// ... |Bar   | ... | V                    |
+/// ... |Inner | ... |                      |
+/// ... |Lol   | ... | T                    |
+/// ... |Wtf   | ... | T                    |
+/// ... |Qux   | ... |                      |
+/// ----+------+-----+----------------------+
+pub(crate) trait TemplateParameters: Sized {
+    /// Get the set of `ItemId`s that make up this template declaration's free
+    /// template parameters.
+    ///
+    /// Note that these might *not* all be named types: C++ allows
+    /// constant-value template parameters as well as template-template
+    /// parameters. Of course, Rust does not allow generic parameters to be
+    /// anything but types, so we must treat them as opaque, and avoid
+    /// instantiating them.
+    fn self_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId>;
+
+    /// Get the number of free template parameters this template declaration
+    /// has.
+    fn num_self_template_params(&self, ctx: &BindgenContext) -> usize {
+        self.self_template_params(ctx).len()
+    }
+
+    /// Get the complete set of template parameters that can affect this
+    /// declaration.
+    ///
+    /// Note that this item doesn't need to be a template declaration itself for
+    /// `Some` to be returned here (in contrast to `self_template_params`). If
+    /// this item is a member of a template declaration, then the parent's
+    /// template parameters are included here.
+    ///
+    /// In the example above, `Inner` depends on both of the `T` and `U` type
+    /// parameters, even though it is not itself a template declaration and
+    /// therefore has no type parameters itself. Perhaps it helps to think about
+    /// how we would fully reference such a member type in C++:
+    /// `Foo<int,char>::Inner`. `Foo` *must* be instantiated with template
+    /// arguments before we can gain access to the `Inner` member type.
+    fn all_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId>
+    where
+        Self: ItemAncestors,
+    {
+        let mut ancestors: Vec<_> = self.ancestors(ctx).collect();
+        ancestors.reverse();
+        ancestors
+            .into_iter()
+            .flat_map(|id| id.self_template_params(ctx).into_iter())
+            .collect()
+    }
+
+    /// Get only the set of template parameters that this item uses. This is a
+    /// subset of `all_template_params` and does not necessarily contain any of
+    /// `self_template_params`.
+    fn used_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId>
+    where
+        Self: AsRef<ItemId>,
+    {
+        assert!(
+            ctx.in_codegen_phase(),
+            "template parameter usage is not computed until codegen"
+        );
+
+        let id = *self.as_ref();
+        ctx.resolve_item(id)
+            .all_template_params(ctx)
+            .into_iter()
+            .filter(|p| ctx.uses_template_parameter(id, *p))
+            .collect()
+    }
+}
+
+/// A trait for things which may or may not be a named template type parameter.
+pub(crate) trait AsTemplateParam {
+    /// Any extra information the implementor might need to make this decision.
+    type Extra;
+
+    /// Convert this thing to the item ID of a named template type parameter.
+    fn as_template_param(
+        &self,
+        ctx: &BindgenContext,
+        extra: &Self::Extra,
+    ) -> Option<TypeId>;
+
+    /// Is this a named template type parameter?
+    fn is_template_param(
+        &self,
+        ctx: &BindgenContext,
+        extra: &Self::Extra,
+    ) -> bool {
+        self.as_template_param(ctx, extra).is_some()
+    }
+}
+
+/// A concrete instantiation of a generic template.
+#[derive(Clone, Debug)]
+pub(crate) struct TemplateInstantiation {
+    /// The template definition which this is instantiating.
+    definition: TypeId,
+    /// The concrete template arguments, which will be substituted in the
+    /// definition for the generic template parameters.
+    args: Vec<TypeId>,
+}
+
+impl TemplateInstantiation {
+    /// Construct a new template instantiation from the given parts.
+    pub(crate) fn new<I>(definition: TypeId, args: I) -> TemplateInstantiation
+    where
+        I: IntoIterator<Item = TypeId>,
+    {
+        TemplateInstantiation {
+            definition,
+            args: args.into_iter().collect(),
+        }
+    }
+
+    /// Get the template definition for this instantiation.
+    pub(crate) fn template_definition(&self) -> TypeId {
+        self.definition
+    }
+
+    /// Get the concrete template arguments used in this instantiation.
+    pub(crate) fn template_arguments(&self) -> &[TypeId] {
+        &self.args[..]
+    }
+
+    /// Parse a `TemplateInstantiation` from a clang `Type`.
+    pub(crate) fn from_ty(
+        ty: &clang::Type,
+        ctx: &mut BindgenContext,
+    ) -> Option<TemplateInstantiation> {
+        use clang_sys::*;
+
+        let template_args = ty.template_args().map_or(vec![], |args| match ty
+            .canonical_type()
+            .template_args()
+        {
+            Some(canonical_args) => {
+                let arg_count = args.len();
+                args.chain(canonical_args.skip(arg_count))
+                    .filter(|t| t.kind() != CXType_Invalid)
+                    .map(|t| {
+                        Item::from_ty_or_ref(t, t.declaration(), None, ctx)
+                    })
+                    .collect()
+            }
+            None => args
+                .filter(|t| t.kind() != CXType_Invalid)
+                .map(|t| Item::from_ty_or_ref(t, t.declaration(), None, ctx))
+                .collect(),
+        });
+
+        let declaration = ty.declaration();
+        let definition = if declaration.kind() == CXCursor_TypeAliasTemplateDecl
+        {
+            Some(declaration)
+        } else {
+            declaration.specialized().or_else(|| {
+                let mut template_ref = None;
+                ty.declaration().visit(|child| {
+                    if child.kind() == CXCursor_TemplateRef {
+                        template_ref = Some(child);
+                        return CXVisit_Break;
+                    }
+
+                    // Instantiations of template aliases might have the
+                    // TemplateRef to the template alias definition arbitrarily
+                    // deep, so we need to recurse here and not only visit
+                    // direct children.
+                    CXChildVisit_Recurse
+                });
+
+                template_ref.and_then(|cur| cur.referenced())
+            })
+        };
+
+        let definition = match definition {
+            Some(def) => def,
+            None => {
+                if !ty.declaration().is_builtin() {
+                    warn!(
+                        "Could not find template definition for template \
+                         instantiation"
+                    );
+                }
+                return None;
+            }
+        };
+
+        let template_definition =
+            Item::from_ty_or_ref(definition.cur_type(), definition, None, ctx);
+
+        Some(TemplateInstantiation::new(
+            template_definition,
+            template_args,
+        ))
+    }
+}
+
+impl IsOpaque for TemplateInstantiation {
+    type Extra = Item;
+
+    /// Is this an opaque template instantiation?
+    fn is_opaque(&self, ctx: &BindgenContext, item: &Item) -> bool {
+        if self.template_definition().is_opaque(ctx, &()) {
+            return true;
+        }
+
+        // TODO(#774): This doesn't properly handle opaque instantiations where
+        // an argument is itself an instantiation because `canonical_name` does
+        // not insert the template arguments into the name, ie it for nested
+        // template arguments it creates "Foo" instead of "Foo<int>". The fully
+        // correct fix is to make `canonical_{name,path}` include template
+        // arguments properly.
+
+        let mut path = item.path_for_allowlisting(ctx).clone();
+        let args: Vec<_> = self
+            .template_arguments()
+            .iter()
+            .map(|arg| {
+                let arg_path =
+                    ctx.resolve_item(*arg).path_for_allowlisting(ctx);
+                arg_path[1..].join("::")
+            })
+            .collect();
+        {
+            let last = path.last_mut().unwrap();
+            last.push('<');
+            last.push_str(&args.join(", "));
+            last.push('>');
+        }
+
+        ctx.opaque_by_name(&path)
+    }
+}
+
+impl Trace for TemplateInstantiation {
+    type Extra = ();
+
+    fn trace<T>(&self, _ctx: &BindgenContext, tracer: &mut T, _: &())
+    where
+        T: Tracer,
+    {
+        tracer
+            .visit_kind(self.definition.into(), EdgeKind::TemplateDeclaration);
+        for arg in self.template_arguments() {
+            tracer.visit_kind(arg.into(), EdgeKind::TemplateArgument);
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/ir/traversal.rs b/third_party/rust/bindgen/ir/traversal.rs
new file mode 100644
index 0000000000..17e24f701e
--- /dev/null
+++ b/third_party/rust/bindgen/ir/traversal.rs
@@ -0,0 +1,479 @@
+//! Traversal of the graph of IR items and types.
+
+use super::context::{BindgenContext, ItemId};
+use super::item::ItemSet;
+use std::collections::{BTreeMap, VecDeque};
+
+/// An outgoing edge in the IR graph is a reference from some item to another
+/// item:
+///
+///   from --> to
+///
+/// The `from` is left implicit: it is the concrete `Trace` implementer which
+/// yielded this outgoing edge.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct Edge {
+    to: ItemId,
+    kind: EdgeKind,
+}
+
+impl Edge {
+    /// Construct a new edge whose referent is `to` and is of the given `kind`.
+    pub(crate) fn new(to: ItemId, kind: EdgeKind) -> Edge {
+        Edge { to, kind }
+    }
+}
+
+impl From<Edge> for ItemId {
+    fn from(val: Edge) -> Self {
+        val.to
+    }
+}
+
+/// The kind of edge reference. This is useful when we wish to only consider
+/// certain kinds of edges for a particular traversal or analysis.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) enum EdgeKind {
+    /// A generic, catch-all edge.
+    Generic,
+
+    /// An edge from a template declaration, to the definition of a named type
+    /// parameter. For example, the edge from `Foo<T>` to `T` in the following
+    /// snippet:
+    ///
+    /// ```C++
+    /// template<typename T>
+    /// class Foo { };
+    /// ```
+    TemplateParameterDefinition,
+
+    /// An edge from a template instantiation to the template declaration that
+    /// is being instantiated. For example, the edge from `Foo<int>` to
+    /// to `Foo<T>`:
+    ///
+    /// ```C++
+    /// template<typename T>
+    /// class Foo { };
+    ///
+    /// using Bar = Foo<ant>;
+    /// ```
+    TemplateDeclaration,
+
+    /// An edge from a template instantiation to its template argument. For
+    /// example, `Foo<Bar>` to `Bar`:
+    ///
+    /// ```C++
+    /// template<typename T>
+    /// class Foo { };
+    ///
+    /// class Bar { };
+    ///
+    /// using FooBar = Foo<Bar>;
+    /// ```
+    TemplateArgument,
+
+    /// An edge from a compound type to one of its base member types. For
+    /// example, the edge from `Bar` to `Foo`:
+    ///
+    /// ```C++
+    /// class Foo { };
+    ///
+    /// class Bar : public Foo { };
+    /// ```
+    BaseMember,
+
+    /// An edge from a compound type to the types of one of its fields. For
+    /// example, the edge from `Foo` to `int`:
+    ///
+    /// ```C++
+    /// class Foo {
+    ///     int x;
+    /// };
+    /// ```
+    Field,
+
+    /// An edge from an class or struct type to an inner type member. For
+    /// example, the edge from `Foo` to `Foo::Bar` here:
+    ///
+    /// ```C++
+    /// class Foo {
+    ///     struct Bar { };
+    /// };
+    /// ```
+    InnerType,
+
+    /// An edge from an class or struct type to an inner static variable. For
+    /// example, the edge from `Foo` to `Foo::BAR` here:
+    ///
+    /// ```C++
+    /// class Foo {
+    ///     static const char* BAR;
+    /// };
+    /// ```
+    InnerVar,
+
+    /// An edge from a class or struct type to one of its method functions. For
+    /// example, the edge from `Foo` to `Foo::bar`:
+    ///
+    /// ```C++
+    /// class Foo {
+    ///     bool bar(int x, int y);
+    /// };
+    /// ```
+    Method,
+
+    /// An edge from a class or struct type to one of its constructor
+    /// functions. For example, the edge from `Foo` to `Foo::Foo(int x, int y)`:
+    ///
+    /// ```C++
+    /// class Foo {
+    ///     int my_x;
+    ///     int my_y;
+    ///
+    ///   public:
+    ///     Foo(int x, int y);
+    /// };
+    /// ```
+    Constructor,
+
+    /// An edge from a class or struct type to its destructor function. For
+    /// example, the edge from `Doggo` to `Doggo::~Doggo()`:
+    ///
+    /// ```C++
+    /// struct Doggo {
+    ///     char* wow;
+    ///
+    ///   public:
+    ///     ~Doggo();
+    /// };
+    /// ```
+    Destructor,
+
+    /// An edge from a function declaration to its return type. For example, the
+    /// edge from `foo` to `int`:
+    ///
+    /// ```C++
+    /// int foo(char* string);
+    /// ```
+    FunctionReturn,
+
+    /// An edge from a function declaration to one of its parameter types. For
+    /// example, the edge from `foo` to `char*`:
+    ///
+    /// ```C++
+    /// int foo(char* string);
+    /// ```
+    FunctionParameter,
+
+    /// An edge from a static variable to its type. For example, the edge from
+    /// `FOO` to `const char*`:
+    ///
+    /// ```C++
+    /// static const char* FOO;
+    /// ```
+    VarType,
+
+    /// An edge from a non-templated alias or typedef to the referenced type.
+    TypeReference,
+}
+
+/// A predicate to allow visiting only sub-sets of the whole IR graph by
+/// excluding certain edges from being followed by the traversal.
+///
+/// The predicate must return true if the traversal should follow this edge
+/// and visit everything that is reachable through it.
+pub(crate) type TraversalPredicate =
+    for<'a> fn(&'a BindgenContext, Edge) -> bool;
+
+/// A `TraversalPredicate` implementation that follows all edges, and therefore
+/// traversals using this predicate will see the whole IR graph reachable from
+/// the traversal's roots.
+pub(crate) fn all_edges(_: &BindgenContext, _: Edge) -> bool {
+    true
+}
+
+/// A `TraversalPredicate` implementation that only follows
+/// `EdgeKind::InnerType` edges, and therefore traversals using this predicate
+/// will only visit the traversal's roots and their inner types. This is used
+/// in no-recursive-allowlist mode, where inner types such as anonymous
+/// structs/unions still need to be processed.
+pub(crate) fn only_inner_type_edges(_: &BindgenContext, edge: Edge) -> bool {
+    edge.kind == EdgeKind::InnerType
+}
+
+/// A `TraversalPredicate` implementation that only follows edges to items that
+/// are enabled for code generation. This lets us skip considering items for
+/// which are not reachable from code generation.
+pub(crate) fn codegen_edges(ctx: &BindgenContext, edge: Edge) -> bool {
+    let cc = &ctx.options().codegen_config;
+    match edge.kind {
+        EdgeKind::Generic => {
+            ctx.resolve_item(edge.to).is_enabled_for_codegen(ctx)
+        }
+
+        // We statically know the kind of item that non-generic edges can point
+        // to, so we don't need to actually resolve the item and check
+        // `Item::is_enabled_for_codegen`.
+        EdgeKind::TemplateParameterDefinition |
+        EdgeKind::TemplateArgument |
+        EdgeKind::TemplateDeclaration |
+        EdgeKind::BaseMember |
+        EdgeKind::Field |
+        EdgeKind::InnerType |
+        EdgeKind::FunctionReturn |
+        EdgeKind::FunctionParameter |
+        EdgeKind::VarType |
+        EdgeKind::TypeReference => cc.types(),
+        EdgeKind::InnerVar => cc.vars(),
+        EdgeKind::Method => cc.methods(),
+        EdgeKind::Constructor => cc.constructors(),
+        EdgeKind::Destructor => cc.destructors(),
+    }
+}
+
+/// The storage for the set of items that have been seen (although their
+/// outgoing edges might not have been fully traversed yet) in an active
+/// traversal.
+pub(crate) trait TraversalStorage<'ctx> {
+    /// Construct a new instance of this TraversalStorage, for a new traversal.
+    fn new(ctx: &'ctx BindgenContext) -> Self;
+
+    /// Add the given item to the storage. If the item has never been seen
+    /// before, return `true`. Otherwise, return `false`.
+    ///
+    /// The `from` item is the item from which we discovered this item, or is
+    /// `None` if this item is a root.
+    fn add(&mut self, from: Option<ItemId>, item: ItemId) -> bool;
+}
+
+impl<'ctx> TraversalStorage<'ctx> for ItemSet {
+    fn new(_: &'ctx BindgenContext) -> Self {
+        ItemSet::new()
+    }
+
+    fn add(&mut self, _: Option<ItemId>, item: ItemId) -> bool {
+        self.insert(item)
+    }
+}
+
+/// A `TraversalStorage` implementation that keeps track of how we first reached
+/// each item. This is useful for providing debug assertions with meaningful
+/// diagnostic messages about dangling items.
+#[derive(Debug)]
+pub(crate) struct Paths<'ctx>(BTreeMap<ItemId, ItemId>, &'ctx BindgenContext);
+
+impl<'ctx> TraversalStorage<'ctx> for Paths<'ctx> {
+    fn new(ctx: &'ctx BindgenContext) -> Self {
+        Paths(BTreeMap::new(), ctx)
+    }
+
+    fn add(&mut self, from: Option<ItemId>, item: ItemId) -> bool {
+        let newly_discovered =
+            self.0.insert(item, from.unwrap_or(item)).is_none();
+
+        if self.1.resolve_item_fallible(item).is_none() {
+            let mut path = vec![];
+            let mut current = item;
+            loop {
+                let predecessor = *self.0.get(&current).expect(
+                    "We know we found this item id, so it must have a \
+                     predecessor",
+                );
+                if predecessor == current {
+                    break;
+                }
+                path.push(predecessor);
+                current = predecessor;
+            }
+            path.reverse();
+            panic!(
+                "Found reference to dangling id = {:?}\nvia path = {:?}",
+                item, path
+            );
+        }
+
+        newly_discovered
+    }
+}
+
+/// The queue of seen-but-not-yet-traversed items.
+///
+/// Using a FIFO queue with a traversal will yield a breadth-first traversal,
+/// while using a LIFO queue will result in a depth-first traversal of the IR
+/// graph.
+pub(crate) trait TraversalQueue: Default {
+    /// Add a newly discovered item to the queue.
+    fn push(&mut self, item: ItemId);
+
+    /// Pop the next item to traverse, if any.
+    fn next(&mut self) -> Option<ItemId>;
+}
+
+impl TraversalQueue for Vec<ItemId> {
+    fn push(&mut self, item: ItemId) {
+        self.push(item);
+    }
+
+    fn next(&mut self) -> Option<ItemId> {
+        self.pop()
+    }
+}
+
+impl TraversalQueue for VecDeque<ItemId> {
+    fn push(&mut self, item: ItemId) {
+        self.push_back(item);
+    }
+
+    fn next(&mut self) -> Option<ItemId> {
+        self.pop_front()
+    }
+}
+
+/// Something that can receive edges from a `Trace` implementation.
+pub(crate) trait Tracer {
+    /// Note an edge between items. Called from within a `Trace` implementation.
+    fn visit_kind(&mut self, item: ItemId, kind: EdgeKind);
+
+    /// A synonym for `tracer.visit_kind(item, EdgeKind::Generic)`.
+    fn visit(&mut self, item: ItemId) {
+        self.visit_kind(item, EdgeKind::Generic);
+    }
+}
+
+impl<F> Tracer for F
+where
+    F: FnMut(ItemId, EdgeKind),
+{
+    fn visit_kind(&mut self, item: ItemId, kind: EdgeKind) {
+        (*self)(item, kind)
+    }
+}
+
+/// Trace all of the outgoing edges to other items. Implementations should call
+/// one of `tracer.visit(edge)` or `tracer.visit_kind(edge, EdgeKind::Whatever)`
+/// for each of their outgoing edges.
+pub(crate) trait Trace {
+    /// If a particular type needs extra information beyond what it has in
+    /// `self` and `context` to find its referenced items, its implementation
+    /// can define this associated type, forcing callers to pass the needed
+    /// information through.
+    type Extra;
+
+    /// Trace all of this item's outgoing edges to other items.
+    fn trace<T>(
+        &self,
+        context: &BindgenContext,
+        tracer: &mut T,
+        extra: &Self::Extra,
+    ) where
+        T: Tracer;
+}
+
+/// An graph traversal of the transitive closure of references between items.
+///
+/// See `BindgenContext::allowlisted_items` for more information.
+pub(crate) struct ItemTraversal<'ctx, Storage, Queue>
+where
+    Storage: TraversalStorage<'ctx>,
+    Queue: TraversalQueue,
+{
+    ctx: &'ctx BindgenContext,
+
+    /// The set of items we have seen thus far in this traversal.
+    seen: Storage,
+
+    /// The set of items that we have seen, but have yet to traverse.
+    queue: Queue,
+
+    /// The predicate that determines which edges this traversal will follow.
+    predicate: TraversalPredicate,
+
+    /// The item we are currently traversing.
+    currently_traversing: Option<ItemId>,
+}
+
+impl<'ctx, Storage, Queue> ItemTraversal<'ctx, Storage, Queue>
+where
+    Storage: TraversalStorage<'ctx>,
+    Queue: TraversalQueue,
+{
+    /// Begin a new traversal, starting from the given roots.
+    pub(crate) fn new<R>(
+        ctx: &'ctx BindgenContext,
+        roots: R,
+        predicate: TraversalPredicate,
+    ) -> ItemTraversal<'ctx, Storage, Queue>
+    where
+        R: IntoIterator<Item = ItemId>,
+    {
+        let mut seen = Storage::new(ctx);
+        let mut queue = Queue::default();
+
+        for id in roots {
+            seen.add(None, id);
+            queue.push(id);
+        }
+
+        ItemTraversal {
+            ctx,
+            seen,
+            queue,
+            predicate,
+            currently_traversing: None,
+        }
+    }
+}
+
+impl<'ctx, Storage, Queue> Tracer for ItemTraversal<'ctx, Storage, Queue>
+where
+    Storage: TraversalStorage<'ctx>,
+    Queue: TraversalQueue,
+{
+    fn visit_kind(&mut self, item: ItemId, kind: EdgeKind) {
+        let edge = Edge::new(item, kind);
+        if !(self.predicate)(self.ctx, edge) {
+            return;
+        }
+
+        let is_newly_discovered =
+            self.seen.add(self.currently_traversing, item);
+        if is_newly_discovered {
+            self.queue.push(item)
+        }
+    }
+}
+
+impl<'ctx, Storage, Queue> Iterator for ItemTraversal<'ctx, Storage, Queue>
+where
+    Storage: TraversalStorage<'ctx>,
+    Queue: TraversalQueue,
+{
+    type Item = ItemId;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let id = self.queue.next()?;
+
+        let newly_discovered = self.seen.add(None, id);
+        debug_assert!(
+            !newly_discovered,
+            "should have already seen anything we get out of our queue"
+        );
+        debug_assert!(
+            self.ctx.resolve_item_fallible(id).is_some(),
+            "should only get IDs of actual items in our context during traversal"
+        );
+
+        self.currently_traversing = Some(id);
+        id.trace(self.ctx, self, &());
+        self.currently_traversing = None;
+
+        Some(id)
+    }
+}
+
+/// An iterator to find any dangling items.
+///
+/// See `BindgenContext::assert_no_dangling_item_traversal` for more
+/// information.
+pub(crate) type AssertNoDanglingItemsTraversal<'ctx> =
+    ItemTraversal<'ctx, Paths<'ctx>, VecDeque<ItemId>>;
diff --git a/third_party/rust/bindgen/ir/ty.rs b/third_party/rust/bindgen/ir/ty.rs
new file mode 100644
index 0000000000..b7a429323e
--- /dev/null
+++ b/third_party/rust/bindgen/ir/ty.rs
@@ -0,0 +1,1281 @@
+//! Everything related to types in our intermediate representation.
+
+use super::comp::CompInfo;
+use super::context::{BindgenContext, ItemId, TypeId};
+use super::dot::DotAttributes;
+use super::enum_ty::Enum;
+use super::function::FunctionSig;
+use super::item::{IsOpaque, Item};
+use super::layout::{Layout, Opaque};
+use super::objc::ObjCInterface;
+use super::template::{
+    AsTemplateParam, TemplateInstantiation, TemplateParameters,
+};
+use super::traversal::{EdgeKind, Trace, Tracer};
+use crate::clang::{self, Cursor};
+use crate::parse::{ParseError, ParseResult};
+use std::borrow::Cow;
+use std::io;
+
+pub use super::int::IntKind;
+
+/// The base representation of a type in bindgen.
+///
+/// A type has an optional name, which if present cannot be empty, a `layout`
+/// (size, alignment and packedness) if known, a `Kind`, which determines which
+/// kind of type it is, and whether the type is const.
+#[derive(Debug)]
+pub(crate) struct Type {
+    /// The name of the type, or None if it was an unnamed struct or union.
+    name: Option<String>,
+    /// The layout of the type, if known.
+    layout: Option<Layout>,
+    /// The inner kind of the type
+    kind: TypeKind,
+    /// Whether this type is const-qualified.
+    is_const: bool,
+}
+
+/// The maximum number of items in an array for which Rust implements common
+/// traits, and so if we have a type containing an array with more than this
+/// many items, we won't be able to derive common traits on that type.
+///
+pub(crate) const RUST_DERIVE_IN_ARRAY_LIMIT: usize = 32;
+
+impl Type {
+    /// Get the underlying `CompInfo` for this type as a mutable reference, or
+    /// `None` if this is some other kind of type.
+    pub(crate) fn as_comp_mut(&mut self) -> Option<&mut CompInfo> {
+        match self.kind {
+            TypeKind::Comp(ref mut ci) => Some(ci),
+            _ => None,
+        }
+    }
+
+    /// Construct a new `Type`.
+    pub(crate) fn new(
+        name: Option<String>,
+        layout: Option<Layout>,
+        kind: TypeKind,
+        is_const: bool,
+    ) -> Self {
+        Type {
+            name,
+            layout,
+            kind,
+            is_const,
+        }
+    }
+
+    /// Which kind of type is this?
+    pub(crate) fn kind(&self) -> &TypeKind {
+        &self.kind
+    }
+
+    /// Get a mutable reference to this type's kind.
+    pub(crate) fn kind_mut(&mut self) -> &mut TypeKind {
+        &mut self.kind
+    }
+
+    /// Get this type's name.
+    pub(crate) fn name(&self) -> Option<&str> {
+        self.name.as_deref()
+    }
+
+    /// Whether this is a block pointer type.
+    pub(crate) fn is_block_pointer(&self) -> bool {
+        matches!(self.kind, TypeKind::BlockPointer(..))
+    }
+
+    /// Is this an integer type, including `bool` or `char`?
+    pub(crate) fn is_int(&self) -> bool {
+        matches!(self.kind, TypeKind::Int(_))
+    }
+
+    /// Is this a compound type?
+    pub(crate) fn is_comp(&self) -> bool {
+        matches!(self.kind, TypeKind::Comp(..))
+    }
+
+    /// Is this a union?
+    pub(crate) fn is_union(&self) -> bool {
+        match self.kind {
+            TypeKind::Comp(ref comp) => comp.is_union(),
+            _ => false,
+        }
+    }
+
+    /// Is this type of kind `TypeKind::TypeParam`?
+    pub(crate) fn is_type_param(&self) -> bool {
+        matches!(self.kind, TypeKind::TypeParam)
+    }
+
+    /// Is this a template instantiation type?
+    pub(crate) fn is_template_instantiation(&self) -> bool {
+        matches!(self.kind, TypeKind::TemplateInstantiation(..))
+    }
+
+    /// Is this a function type?
+    pub(crate) fn is_function(&self) -> bool {
+        matches!(self.kind, TypeKind::Function(..))
+    }
+
+    /// Is this an enum type?
+    pub(crate) fn is_enum(&self) -> bool {
+        matches!(self.kind, TypeKind::Enum(..))
+    }
+
+    /// Is this void?
+    pub(crate) fn is_void(&self) -> bool {
+        matches!(self.kind, TypeKind::Void)
+    }
+    /// Is this either a builtin or named type?
+    pub(crate) fn is_builtin_or_type_param(&self) -> bool {
+        matches!(
+            self.kind,
+            TypeKind::Void |
+                TypeKind::NullPtr |
+                TypeKind::Function(..) |
+                TypeKind::Array(..) |
+                TypeKind::Reference(..) |
+                TypeKind::Pointer(..) |
+                TypeKind::Int(..) |
+                TypeKind::Float(..) |
+                TypeKind::TypeParam
+        )
+    }
+
+    /// Creates a new named type, with name `name`.
+    pub(crate) fn named(name: String) -> Self {
+        let name = if name.is_empty() { None } else { Some(name) };
+        Self::new(name, None, TypeKind::TypeParam, false)
+    }
+
+    /// Is this a floating point type?
+    pub(crate) fn is_float(&self) -> bool {
+        matches!(self.kind, TypeKind::Float(..))
+    }
+
+    /// Is this a boolean type?
+    pub(crate) fn is_bool(&self) -> bool {
+        matches!(self.kind, TypeKind::Int(IntKind::Bool))
+    }
+
+    /// Is this an integer type?
+    pub(crate) fn is_integer(&self) -> bool {
+        matches!(self.kind, TypeKind::Int(..))
+    }
+
+    /// Cast this type to an integer kind, or `None` if it is not an integer
+    /// type.
+    pub(crate) fn as_integer(&self) -> Option<IntKind> {
+        match self.kind {
+            TypeKind::Int(int_kind) => Some(int_kind),
+            _ => None,
+        }
+    }
+
+    /// Is this a `const` qualified type?
+    pub(crate) fn is_const(&self) -> bool {
+        self.is_const
+    }
+
+    /// Is this an unresolved reference?
+    pub(crate) fn is_unresolved_ref(&self) -> bool {
+        matches!(self.kind, TypeKind::UnresolvedTypeRef(_, _, _))
+    }
+
+    /// Is this a incomplete array type?
+    pub(crate) fn is_incomplete_array(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Option<ItemId> {
+        match self.kind {
+            TypeKind::Array(item, len) => {
+                if len == 0 {
+                    Some(item.into())
+                } else {
+                    None
+                }
+            }
+            TypeKind::ResolvedTypeRef(inner) => {
+                ctx.resolve_type(inner).is_incomplete_array(ctx)
+            }
+            _ => None,
+        }
+    }
+
+    /// What is the layout of this type?
+    pub(crate) fn layout(&self, ctx: &BindgenContext) -> Option<Layout> {
+        self.layout.or_else(|| {
+            match self.kind {
+                TypeKind::Comp(ref ci) => ci.layout(ctx),
+                TypeKind::Array(inner, 0) => Some(Layout::new(
+                    0,
+                    ctx.resolve_type(inner).layout(ctx)?.align,
+                )),
+                // FIXME(emilio): This is a hack for anonymous union templates.
+                // Use the actual pointer size!
+                TypeKind::Pointer(..) => Some(Layout::new(
+                    ctx.target_pointer_size(),
+                    ctx.target_pointer_size(),
+                )),
+                TypeKind::ResolvedTypeRef(inner) => {
+                    ctx.resolve_type(inner).layout(ctx)
+                }
+                _ => None,
+            }
+        })
+    }
+
+    /// Whether this named type is an invalid C++ identifier. This is done to
+    /// avoid generating invalid code with some cases we can't handle, see:
+    ///
+    /// tests/headers/381-decltype-alias.hpp
+    pub(crate) fn is_invalid_type_param(&self) -> bool {
+        match self.kind {
+            TypeKind::TypeParam => {
+                let name = self.name().expect("Unnamed named type?");
+                !clang::is_valid_identifier(name)
+            }
+            _ => false,
+        }
+    }
+
+    /// Takes `name`, and returns a suitable identifier representation for it.
+    fn sanitize_name(name: &str) -> Cow<str> {
+        if clang::is_valid_identifier(name) {
+            return Cow::Borrowed(name);
+        }
+
+        let name = name.replace(|c| c == ' ' || c == ':' || c == '.', "_");
+        Cow::Owned(name)
+    }
+
+    /// Get this type's santizied name.
+    pub(crate) fn sanitized_name<'a>(
+        &'a self,
+        ctx: &BindgenContext,
+    ) -> Option<Cow<'a, str>> {
+        let name_info = match *self.kind() {
+            TypeKind::Pointer(inner) => Some((inner, Cow::Borrowed("ptr"))),
+            TypeKind::Reference(inner) => Some((inner, Cow::Borrowed("ref"))),
+            TypeKind::Array(inner, length) => {
+                Some((inner, format!("array{}", length).into()))
+            }
+            _ => None,
+        };
+        if let Some((inner, prefix)) = name_info {
+            ctx.resolve_item(inner)
+                .expect_type()
+                .sanitized_name(ctx)
+                .map(|name| format!("{}_{}", prefix, name).into())
+        } else {
+            self.name().map(Self::sanitize_name)
+        }
+    }
+
+    /// See safe_canonical_type.
+    pub(crate) fn canonical_type<'tr>(
+        &'tr self,
+        ctx: &'tr BindgenContext,
+    ) -> &'tr Type {
+        self.safe_canonical_type(ctx)
+            .expect("Should have been resolved after parsing!")
+    }
+
+    /// Returns the canonical type of this type, that is, the "inner type".
+    ///
+    /// For example, for a `typedef`, the canonical type would be the
+    /// `typedef`ed type, for a template instantiation, would be the template
+    /// its specializing, and so on. Return None if the type is unresolved.
+    pub(crate) fn safe_canonical_type<'tr>(
+        &'tr self,
+        ctx: &'tr BindgenContext,
+    ) -> Option<&'tr Type> {
+        match self.kind {
+            TypeKind::TypeParam |
+            TypeKind::Array(..) |
+            TypeKind::Vector(..) |
+            TypeKind::Comp(..) |
+            TypeKind::Opaque |
+            TypeKind::Int(..) |
+            TypeKind::Float(..) |
+            TypeKind::Complex(..) |
+            TypeKind::Function(..) |
+            TypeKind::Enum(..) |
+            TypeKind::Reference(..) |
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Pointer(..) |
+            TypeKind::BlockPointer(..) |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel |
+            TypeKind::ObjCInterface(..) => Some(self),
+
+            TypeKind::ResolvedTypeRef(inner) |
+            TypeKind::Alias(inner) |
+            TypeKind::TemplateAlias(inner, _) => {
+                ctx.resolve_type(inner).safe_canonical_type(ctx)
+            }
+            TypeKind::TemplateInstantiation(ref inst) => ctx
+                .resolve_type(inst.template_definition())
+                .safe_canonical_type(ctx),
+
+            TypeKind::UnresolvedTypeRef(..) => None,
+        }
+    }
+
+    /// There are some types we don't want to stop at when finding an opaque
+    /// item, so we can arrive to the proper item that needs to be generated.
+    pub(crate) fn should_be_traced_unconditionally(&self) -> bool {
+        matches!(
+            self.kind,
+            TypeKind::Comp(..) |
+                TypeKind::Function(..) |
+                TypeKind::Pointer(..) |
+                TypeKind::Array(..) |
+                TypeKind::Reference(..) |
+                TypeKind::TemplateInstantiation(..) |
+                TypeKind::ResolvedTypeRef(..)
+        )
+    }
+}
+
+impl IsOpaque for Type {
+    type Extra = Item;
+
+    fn is_opaque(&self, ctx: &BindgenContext, item: &Item) -> bool {
+        match self.kind {
+            TypeKind::Opaque => true,
+            TypeKind::TemplateInstantiation(ref inst) => {
+                inst.is_opaque(ctx, item)
+            }
+            TypeKind::Comp(ref comp) => comp.is_opaque(ctx, &self.layout),
+            TypeKind::ResolvedTypeRef(to) => to.is_opaque(ctx, &()),
+            _ => false,
+        }
+    }
+}
+
+impl AsTemplateParam for Type {
+    type Extra = Item;
+
+    fn as_template_param(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> Option<TypeId> {
+        self.kind.as_template_param(ctx, item)
+    }
+}
+
+impl AsTemplateParam for TypeKind {
+    type Extra = Item;
+
+    fn as_template_param(
+        &self,
+        ctx: &BindgenContext,
+        item: &Item,
+    ) -> Option<TypeId> {
+        match *self {
+            TypeKind::TypeParam => Some(item.id().expect_type_id(ctx)),
+            TypeKind::ResolvedTypeRef(id) => id.as_template_param(ctx, &()),
+            _ => None,
+        }
+    }
+}
+
+impl DotAttributes for Type {
+    fn dot_attributes<W>(
+        &self,
+        ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        if let Some(ref layout) = self.layout {
+            writeln!(
+                out,
+                "<tr><td>size</td><td>{}</td></tr>
+                           <tr><td>align</td><td>{}</td></tr>",
+                layout.size, layout.align
+            )?;
+            if layout.packed {
+                writeln!(out, "<tr><td>packed</td><td>true</td></tr>")?;
+            }
+        }
+
+        if self.is_const {
+            writeln!(out, "<tr><td>const</td><td>true</td></tr>")?;
+        }
+
+        self.kind.dot_attributes(ctx, out)
+    }
+}
+
+impl DotAttributes for TypeKind {
+    fn dot_attributes<W>(
+        &self,
+        ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        writeln!(
+            out,
+            "<tr><td>type kind</td><td>{}</td></tr>",
+            self.kind_name()
+        )?;
+
+        if let TypeKind::Comp(ref comp) = *self {
+            comp.dot_attributes(ctx, out)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl TypeKind {
+    fn kind_name(&self) -> &'static str {
+        match *self {
+            TypeKind::Void => "Void",
+            TypeKind::NullPtr => "NullPtr",
+            TypeKind::Comp(..) => "Comp",
+            TypeKind::Opaque => "Opaque",
+            TypeKind::Int(..) => "Int",
+            TypeKind::Float(..) => "Float",
+            TypeKind::Complex(..) => "Complex",
+            TypeKind::Alias(..) => "Alias",
+            TypeKind::TemplateAlias(..) => "TemplateAlias",
+            TypeKind::Array(..) => "Array",
+            TypeKind::Vector(..) => "Vector",
+            TypeKind::Function(..) => "Function",
+            TypeKind::Enum(..) => "Enum",
+            TypeKind::Pointer(..) => "Pointer",
+            TypeKind::BlockPointer(..) => "BlockPointer",
+            TypeKind::Reference(..) => "Reference",
+            TypeKind::TemplateInstantiation(..) => "TemplateInstantiation",
+            TypeKind::UnresolvedTypeRef(..) => "UnresolvedTypeRef",
+            TypeKind::ResolvedTypeRef(..) => "ResolvedTypeRef",
+            TypeKind::TypeParam => "TypeParam",
+            TypeKind::ObjCInterface(..) => "ObjCInterface",
+            TypeKind::ObjCId => "ObjCId",
+            TypeKind::ObjCSel => "ObjCSel",
+        }
+    }
+}
+
+#[test]
+fn is_invalid_type_param_valid() {
+    let ty = Type::new(Some("foo".into()), None, TypeKind::TypeParam, false);
+    assert!(!ty.is_invalid_type_param())
+}
+
+#[test]
+fn is_invalid_type_param_valid_underscore_and_numbers() {
+    let ty = Type::new(
+        Some("_foo123456789_".into()),
+        None,
+        TypeKind::TypeParam,
+        false,
+    );
+    assert!(!ty.is_invalid_type_param())
+}
+
+#[test]
+fn is_invalid_type_param_valid_unnamed_kind() {
+    let ty = Type::new(Some("foo".into()), None, TypeKind::Void, false);
+    assert!(!ty.is_invalid_type_param())
+}
+
+#[test]
+fn is_invalid_type_param_invalid_start() {
+    let ty = Type::new(Some("1foo".into()), None, TypeKind::TypeParam, false);
+    assert!(ty.is_invalid_type_param())
+}
+
+#[test]
+fn is_invalid_type_param_invalid_remaing() {
+    let ty = Type::new(Some("foo-".into()), None, TypeKind::TypeParam, false);
+    assert!(ty.is_invalid_type_param())
+}
+
+#[test]
+#[should_panic]
+fn is_invalid_type_param_unnamed() {
+    let ty = Type::new(None, None, TypeKind::TypeParam, false);
+    assert!(ty.is_invalid_type_param())
+}
+
+#[test]
+fn is_invalid_type_param_empty_name() {
+    let ty = Type::new(Some("".into()), None, TypeKind::TypeParam, false);
+    assert!(ty.is_invalid_type_param())
+}
+
+impl TemplateParameters for Type {
+    fn self_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId> {
+        self.kind.self_template_params(ctx)
+    }
+}
+
+impl TemplateParameters for TypeKind {
+    fn self_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId> {
+        match *self {
+            TypeKind::ResolvedTypeRef(id) => {
+                ctx.resolve_type(id).self_template_params(ctx)
+            }
+            TypeKind::Comp(ref comp) => comp.self_template_params(ctx),
+            TypeKind::TemplateAlias(_, ref args) => args.clone(),
+
+            TypeKind::Opaque |
+            TypeKind::TemplateInstantiation(..) |
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Int(_) |
+            TypeKind::Float(_) |
+            TypeKind::Complex(_) |
+            TypeKind::Array(..) |
+            TypeKind::Vector(..) |
+            TypeKind::Function(_) |
+            TypeKind::Enum(_) |
+            TypeKind::Pointer(_) |
+            TypeKind::BlockPointer(_) |
+            TypeKind::Reference(_) |
+            TypeKind::UnresolvedTypeRef(..) |
+            TypeKind::TypeParam |
+            TypeKind::Alias(_) |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel |
+            TypeKind::ObjCInterface(_) => vec![],
+        }
+    }
+}
+
+/// The kind of float this type represents.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum FloatKind {
+    /// A half (`_Float16` or `__fp16`)
+    Float16,
+    /// A `float`.
+    Float,
+    /// A `double`.
+    Double,
+    /// A `long double`.
+    LongDouble,
+    /// A `__float128`.
+    Float128,
+}
+
+/// The different kinds of types that we can parse.
+#[derive(Debug)]
+pub(crate) enum TypeKind {
+    /// The void type.
+    Void,
+
+    /// The `nullptr_t` type.
+    NullPtr,
+
+    /// A compound type, that is, a class, struct, or union.
+    Comp(CompInfo),
+
+    /// An opaque type that we just don't understand. All usage of this shoulf
+    /// result in an opaque blob of bytes generated from the containing type's
+    /// layout.
+    Opaque,
+
+    /// An integer type, of a given kind. `bool` and `char` are also considered
+    /// integers.
+    Int(IntKind),
+
+    /// A floating point type.
+    Float(FloatKind),
+
+    /// A complex floating point type.
+    Complex(FloatKind),
+
+    /// A type alias, with a name, that points to another type.
+    Alias(TypeId),
+
+    /// A templated alias, pointing to an inner type, just as `Alias`, but with
+    /// template parameters.
+    TemplateAlias(TypeId, Vec<TypeId>),
+
+    /// A packed vector type: element type, number of elements
+    Vector(TypeId, usize),
+
+    /// An array of a type and a length.
+    Array(TypeId, usize),
+
+    /// A function type, with a given signature.
+    Function(FunctionSig),
+
+    /// An `enum` type.
+    Enum(Enum),
+
+    /// A pointer to a type. The bool field represents whether it's const or
+    /// not.
+    Pointer(TypeId),
+
+    /// A pointer to an Apple block.
+    BlockPointer(TypeId),
+
+    /// A reference to a type, as in: int& foo().
+    Reference(TypeId),
+
+    /// An instantiation of an abstract template definition with a set of
+    /// concrete template arguments.
+    TemplateInstantiation(TemplateInstantiation),
+
+    /// A reference to a yet-to-resolve type. This stores the clang cursor
+    /// itself, and postpones its resolution.
+    ///
+    /// These are gone in a phase after parsing where these are mapped to
+    /// already known types, and are converted to ResolvedTypeRef.
+    ///
+    /// see tests/headers/typeref.hpp to see somewhere where this is a problem.
+    UnresolvedTypeRef(
+        clang::Type,
+        clang::Cursor,
+        /* parent_id */
+        Option<ItemId>,
+    ),
+
+    /// An indirection to another type.
+    ///
+    /// These are generated after we resolve a forward declaration, or when we
+    /// replace one type with another.
+    ResolvedTypeRef(TypeId),
+
+    /// A named type, that is, a template parameter.
+    TypeParam,
+
+    /// Objective C interface. Always referenced through a pointer
+    ObjCInterface(ObjCInterface),
+
+    /// Objective C 'id' type, points to any object
+    ObjCId,
+
+    /// Objective C selector type
+    ObjCSel,
+}
+
+impl Type {
+    /// This is another of the nasty methods. This one is the one that takes
+    /// care of the core logic of converting a clang type to a `Type`.
+    ///
+    /// It's sort of nasty and full of special-casing, but hopefully the
+    /// comments in every special case justify why they're there.
+    pub(crate) fn from_clang_ty(
+        potential_id: ItemId,
+        ty: &clang::Type,
+        location: Cursor,
+        parent_id: Option<ItemId>,
+        ctx: &mut BindgenContext,
+    ) -> Result<ParseResult<Self>, ParseError> {
+        use clang_sys::*;
+        {
+            let already_resolved = ctx.builtin_or_resolved_ty(
+                potential_id,
+                parent_id,
+                ty,
+                Some(location),
+            );
+            if let Some(ty) = already_resolved {
+                debug!("{:?} already resolved: {:?}", ty, location);
+                return Ok(ParseResult::AlreadyResolved(ty.into()));
+            }
+        }
+
+        let layout = ty.fallible_layout(ctx).ok();
+        let cursor = ty.declaration();
+        let is_anonymous = cursor.is_anonymous();
+        let mut name = if is_anonymous {
+            None
+        } else {
+            Some(cursor.spelling()).filter(|n| !n.is_empty())
+        };
+
+        debug!(
+            "from_clang_ty: {:?}, ty: {:?}, loc: {:?}",
+            potential_id, ty, location
+        );
+        debug!("currently_parsed_types: {:?}", ctx.currently_parsed_types());
+
+        let canonical_ty = ty.canonical_type();
+
+        // Parse objc protocols as if they were interfaces
+        let mut ty_kind = ty.kind();
+        match location.kind() {
+            CXCursor_ObjCProtocolDecl | CXCursor_ObjCCategoryDecl => {
+                ty_kind = CXType_ObjCInterface
+            }
+            _ => {}
+        }
+
+        // Objective C template type parameter
+        // FIXME: This is probably wrong, we are attempting to find the
+        //        objc template params, which seem to manifest as a typedef.
+        //        We are rewriting them as ID to suppress multiple conflicting
+        //        typedefs at root level
+        if ty_kind == CXType_Typedef {
+            let is_template_type_param =
+                ty.declaration().kind() == CXCursor_TemplateTypeParameter;
+            let is_canonical_objcpointer =
+                canonical_ty.kind() == CXType_ObjCObjectPointer;
+
+            // We have found a template type for objc interface
+            if is_canonical_objcpointer && is_template_type_param {
+                // Objective-C generics are just ids with fancy name.
+                // To keep it simple, just name them ids
+                name = Some("id".to_owned());
+            }
+        }
+
+        if location.kind() == CXCursor_ClassTemplatePartialSpecialization {
+            // Sorry! (Not sorry)
+            warn!(
+                "Found a partial template specialization; bindgen does not \
+                 support partial template specialization! Constructing \
+                 opaque type instead."
+            );
+            return Ok(ParseResult::New(
+                Opaque::from_clang_ty(&canonical_ty, ctx),
+                None,
+            ));
+        }
+
+        let kind = if location.kind() == CXCursor_TemplateRef ||
+            (ty.template_args().is_some() && ty_kind != CXType_Typedef)
+        {
+            // This is a template instantiation.
+            match TemplateInstantiation::from_ty(ty, ctx) {
+                Some(inst) => TypeKind::TemplateInstantiation(inst),
+                None => TypeKind::Opaque,
+            }
+        } else {
+            match ty_kind {
+                CXType_Unexposed
+                    if *ty != canonical_ty &&
+                                    canonical_ty.kind() != CXType_Invalid &&
+                                    ty.ret_type().is_none() &&
+                                    // Sometime clang desugars some types more than
+                                    // what we need, specially with function
+                                    // pointers.
+                                    //
+                                    // We should also try the solution of inverting
+                                    // those checks instead of doing this, that is,
+                                    // something like:
+                                    //
+                                    // CXType_Unexposed if ty.ret_type().is_some()
+                                    //   => { ... }
+                                    //
+                                    // etc.
+                                    !canonical_ty.spelling().contains("type-parameter") =>
+                {
+                    debug!("Looking for canonical type: {:?}", canonical_ty);
+                    return Self::from_clang_ty(
+                        potential_id,
+                        &canonical_ty,
+                        location,
+                        parent_id,
+                        ctx,
+                    );
+                }
+                CXType_Unexposed | CXType_Invalid => {
+                    // For some reason Clang doesn't give us any hint in some
+                    // situations where we should generate a function pointer (see
+                    // tests/headers/func_ptr_in_struct.h), so we do a guess here
+                    // trying to see if it has a valid return type.
+                    if ty.ret_type().is_some() {
+                        let signature =
+                            FunctionSig::from_ty(ty, &location, ctx)?;
+                        TypeKind::Function(signature)
+                    // Same here, with template specialisations we can safely
+                    // assume this is a Comp(..)
+                    } else if ty.is_fully_instantiated_template() {
+                        debug!(
+                            "Template specialization: {:?}, {:?} {:?}",
+                            ty, location, canonical_ty
+                        );
+                        let complex = CompInfo::from_ty(
+                            potential_id,
+                            ty,
+                            Some(location),
+                            ctx,
+                        )
+                        .expect("C'mon");
+                        TypeKind::Comp(complex)
+                    } else {
+                        match location.kind() {
+                            CXCursor_CXXBaseSpecifier |
+                            CXCursor_ClassTemplate => {
+                                if location.kind() == CXCursor_CXXBaseSpecifier
+                                {
+                                    // In the case we're parsing a base specifier
+                                    // inside an unexposed or invalid type, it means
+                                    // that we're parsing one of two things:
+                                    //
+                                    //  * A template parameter.
+                                    //  * A complex class that isn't exposed.
+                                    //
+                                    // This means, unfortunately, that there's no
+                                    // good way to differentiate between them.
+                                    //
+                                    // Probably we could try to look at the
+                                    // declaration and complicate more this logic,
+                                    // but we'll keep it simple... if it's a valid
+                                    // C++ identifier, we'll consider it as a
+                                    // template parameter.
+                                    //
+                                    // This is because:
+                                    //
+                                    //  * We expect every other base that is a
+                                    //    proper identifier (that is, a simple
+                                    //    struct/union declaration), to be exposed,
+                                    //    so this path can't be reached in that
+                                    //    case.
+                                    //
+                                    //  * Quite conveniently, complex base
+                                    //    specifiers preserve their full names (that
+                                    //    is: Foo<T> instead of Foo). We can take
+                                    //    advantage of this.
+                                    //
+                                    // If we find some edge case where this doesn't
+                                    // work (which I guess is unlikely, see the
+                                    // different test cases[1][2][3][4]), we'd need
+                                    // to find more creative ways of differentiating
+                                    // these two cases.
+                                    //
+                                    // [1]: inherit_named.hpp
+                                    // [2]: forward-inherit-struct-with-fields.hpp
+                                    // [3]: forward-inherit-struct.hpp
+                                    // [4]: inherit-namespaced.hpp
+                                    if location.spelling().chars().all(|c| {
+                                        c.is_alphanumeric() || c == '_'
+                                    }) {
+                                        return Err(ParseError::Recurse);
+                                    }
+                                } else {
+                                    name = Some(location.spelling());
+                                }
+
+                                let complex = CompInfo::from_ty(
+                                    potential_id,
+                                    ty,
+                                    Some(location),
+                                    ctx,
+                                );
+                                match complex {
+                                    Ok(complex) => TypeKind::Comp(complex),
+                                    Err(_) => {
+                                        warn!(
+                                            "Could not create complex type \
+                                             from class template or base \
+                                             specifier, using opaque blob"
+                                        );
+                                        let opaque =
+                                            Opaque::from_clang_ty(ty, ctx);
+                                        return Ok(ParseResult::New(
+                                            opaque, None,
+                                        ));
+                                    }
+                                }
+                            }
+                            CXCursor_TypeAliasTemplateDecl => {
+                                debug!("TypeAliasTemplateDecl");
+
+                                // We need to manually unwind this one.
+                                let mut inner = Err(ParseError::Continue);
+                                let mut args = vec![];
+
+                                location.visit(|cur| {
+                                    match cur.kind() {
+                                        CXCursor_TypeAliasDecl => {
+                                            let current = cur.cur_type();
+
+                                            debug_assert_eq!(
+                                                current.kind(),
+                                                CXType_Typedef
+                                            );
+
+                                            name = Some(location.spelling());
+
+                                            let inner_ty = cur
+                                                .typedef_type()
+                                                .expect("Not valid Type?");
+                                            inner = Ok(Item::from_ty_or_ref(
+                                                inner_ty,
+                                                cur,
+                                                Some(potential_id),
+                                                ctx,
+                                            ));
+                                        }
+                                        CXCursor_TemplateTypeParameter => {
+                                            let param = Item::type_param(
+                                                None, cur, ctx,
+                                            )
+                                            .expect(
+                                                "Item::type_param shouldn't \
+                                                 ever fail if we are looking \
+                                                 at a TemplateTypeParameter",
+                                            );
+                                            args.push(param);
+                                        }
+                                        _ => {}
+                                    }
+                                    CXChildVisit_Continue
+                                });
+
+                                let inner_type = match inner {
+                                    Ok(inner) => inner,
+                                    Err(..) => {
+                                        warn!(
+                                            "Failed to parse template alias \
+                                             {:?}",
+                                            location
+                                        );
+                                        return Err(ParseError::Continue);
+                                    }
+                                };
+
+                                TypeKind::TemplateAlias(inner_type, args)
+                            }
+                            CXCursor_TemplateRef => {
+                                let referenced = location.referenced().unwrap();
+                                let referenced_ty = referenced.cur_type();
+
+                                debug!(
+                                    "TemplateRef: location = {:?}; referenced = \
+                                        {:?}; referenced_ty = {:?}",
+                                    location,
+                                    referenced,
+                                    referenced_ty
+                                );
+
+                                return Self::from_clang_ty(
+                                    potential_id,
+                                    &referenced_ty,
+                                    referenced,
+                                    parent_id,
+                                    ctx,
+                                );
+                            }
+                            CXCursor_TypeRef => {
+                                let referenced = location.referenced().unwrap();
+                                let referenced_ty = referenced.cur_type();
+                                let declaration = referenced_ty.declaration();
+
+                                debug!(
+                                    "TypeRef: location = {:?}; referenced = \
+                                     {:?}; referenced_ty = {:?}",
+                                    location, referenced, referenced_ty
+                                );
+
+                                let id = Item::from_ty_or_ref_with_id(
+                                    potential_id,
+                                    referenced_ty,
+                                    declaration,
+                                    parent_id,
+                                    ctx,
+                                );
+                                return Ok(ParseResult::AlreadyResolved(
+                                    id.into(),
+                                ));
+                            }
+                            CXCursor_NamespaceRef => {
+                                return Err(ParseError::Continue);
+                            }
+                            _ => {
+                                if ty.kind() == CXType_Unexposed {
+                                    warn!(
+                                        "Unexposed type {:?}, recursing inside, \
+                                          loc: {:?}",
+                                        ty,
+                                        location
+                                    );
+                                    return Err(ParseError::Recurse);
+                                }
+
+                                warn!("invalid type {:?}", ty);
+                                return Err(ParseError::Continue);
+                            }
+                        }
+                    }
+                }
+                CXType_Auto => {
+                    if canonical_ty == *ty {
+                        debug!("Couldn't find deduced type: {:?}", ty);
+                        return Err(ParseError::Continue);
+                    }
+
+                    return Self::from_clang_ty(
+                        potential_id,
+                        &canonical_ty,
+                        location,
+                        parent_id,
+                        ctx,
+                    );
+                }
+                // NOTE: We don't resolve pointers eagerly because the pointee type
+                // might not have been parsed, and if it contains templates or
+                // something else we might get confused, see the comment inside
+                // TypeRef.
+                //
+                // We might need to, though, if the context is already in the
+                // process of resolving them.
+                CXType_ObjCObjectPointer |
+                CXType_MemberPointer |
+                CXType_Pointer => {
+                    let mut pointee = ty.pointee_type().unwrap();
+                    if *ty != canonical_ty {
+                        let canonical_pointee =
+                            canonical_ty.pointee_type().unwrap();
+                        // clang sometimes loses pointee constness here, see
+                        // #2244.
+                        if canonical_pointee.is_const() != pointee.is_const() {
+                            pointee = canonical_pointee;
+                        }
+                    }
+                    let inner =
+                        Item::from_ty_or_ref(pointee, location, None, ctx);
+                    TypeKind::Pointer(inner)
+                }
+                CXType_BlockPointer => {
+                    let pointee = ty.pointee_type().expect("Not valid Type?");
+                    let inner =
+                        Item::from_ty_or_ref(pointee, location, None, ctx);
+                    TypeKind::BlockPointer(inner)
+                }
+                // XXX: RValueReference is most likely wrong, but I don't think we
+                // can even add bindings for that, so huh.
+                CXType_RValueReference | CXType_LValueReference => {
+                    let inner = Item::from_ty_or_ref(
+                        ty.pointee_type().unwrap(),
+                        location,
+                        None,
+                        ctx,
+                    );
+                    TypeKind::Reference(inner)
+                }
+                // XXX DependentSizedArray is wrong
+                CXType_VariableArray | CXType_DependentSizedArray => {
+                    let inner = Item::from_ty(
+                        ty.elem_type().as_ref().unwrap(),
+                        location,
+                        None,
+                        ctx,
+                    )
+                    .expect("Not able to resolve array element?");
+                    TypeKind::Pointer(inner)
+                }
+                CXType_IncompleteArray => {
+                    let inner = Item::from_ty(
+                        ty.elem_type().as_ref().unwrap(),
+                        location,
+                        None,
+                        ctx,
+                    )
+                    .expect("Not able to resolve array element?");
+                    TypeKind::Array(inner, 0)
+                }
+                CXType_FunctionNoProto | CXType_FunctionProto => {
+                    let signature = FunctionSig::from_ty(ty, &location, ctx)?;
+                    TypeKind::Function(signature)
+                }
+                CXType_Typedef => {
+                    let inner = cursor.typedef_type().expect("Not valid Type?");
+                    let inner_id =
+                        Item::from_ty_or_ref(inner, location, None, ctx);
+                    if inner_id == potential_id {
+                        warn!(
+                            "Generating oqaque type instead of self-referential \
+                            typedef");
+                        // This can happen if we bail out of recursive situations
+                        // within the clang parsing.
+                        TypeKind::Opaque
+                    } else {
+                        // Check if this type definition is an alias to a pointer of a `struct` /
+                        // `union` / `enum` with the same name and add the `_ptr` suffix to it to
+                        // avoid name collisions.
+                        if let Some(ref mut name) = name {
+                            if inner.kind() == CXType_Pointer &&
+                                !ctx.options().c_naming
+                            {
+                                let pointee = inner.pointee_type().unwrap();
+                                if pointee.kind() == CXType_Elaborated &&
+                                    pointee.declaration().spelling() == *name
+                                {
+                                    *name += "_ptr";
+                                }
+                            }
+                        }
+                        TypeKind::Alias(inner_id)
+                    }
+                }
+                CXType_Enum => {
+                    let enum_ = Enum::from_ty(ty, ctx).expect("Not an enum?");
+
+                    if !is_anonymous {
+                        let pretty_name = ty.spelling();
+                        if clang::is_valid_identifier(&pretty_name) {
+                            name = Some(pretty_name);
+                        }
+                    }
+
+                    TypeKind::Enum(enum_)
+                }
+                CXType_Record => {
+                    let complex = CompInfo::from_ty(
+                        potential_id,
+                        ty,
+                        Some(location),
+                        ctx,
+                    )
+                    .expect("Not a complex type?");
+
+                    if !is_anonymous {
+                        // The pretty-printed name may contain typedefed name,
+                        // but may also be "struct (anonymous at .h:1)"
+                        let pretty_name = ty.spelling();
+                        if clang::is_valid_identifier(&pretty_name) {
+                            name = Some(pretty_name);
+                        }
+                    }
+
+                    TypeKind::Comp(complex)
+                }
+                CXType_Vector => {
+                    let inner = Item::from_ty(
+                        ty.elem_type().as_ref().unwrap(),
+                        location,
+                        None,
+                        ctx,
+                    )?;
+                    TypeKind::Vector(inner, ty.num_elements().unwrap())
+                }
+                CXType_ConstantArray => {
+                    let inner = Item::from_ty(
+                        ty.elem_type().as_ref().unwrap(),
+                        location,
+                        None,
+                        ctx,
+                    )
+                    .expect("Not able to resolve array element?");
+                    TypeKind::Array(inner, ty.num_elements().unwrap())
+                }
+                CXType_Elaborated => {
+                    return Self::from_clang_ty(
+                        potential_id,
+                        &ty.named(),
+                        location,
+                        parent_id,
+                        ctx,
+                    );
+                }
+                CXType_ObjCId => TypeKind::ObjCId,
+                CXType_ObjCSel => TypeKind::ObjCSel,
+                CXType_ObjCClass | CXType_ObjCInterface => {
+                    let interface = ObjCInterface::from_ty(&location, ctx)
+                        .expect("Not a valid objc interface?");
+                    if !is_anonymous {
+                        name = Some(interface.rust_name());
+                    }
+                    TypeKind::ObjCInterface(interface)
+                }
+                CXType_Dependent => {
+                    return Err(ParseError::Continue);
+                }
+                _ => {
+                    warn!(
+                        "unsupported type: kind = {:?}; ty = {:?}; at {:?}",
+                        ty.kind(),
+                        ty,
+                        location
+                    );
+                    return Err(ParseError::Continue);
+                }
+            }
+        };
+
+        name = name.filter(|n| !n.is_empty());
+
+        let is_const = ty.is_const() ||
+            (ty.kind() == CXType_ConstantArray &&
+                ty.elem_type()
+                    .map_or(false, |element| element.is_const()));
+
+        let ty = Type::new(name, layout, kind, is_const);
+        // TODO: maybe declaration.canonical()?
+        Ok(ParseResult::New(ty, Some(cursor.canonical())))
+    }
+}
+
+impl Trace for Type {
+    type Extra = Item;
+
+    fn trace<T>(&self, context: &BindgenContext, tracer: &mut T, item: &Item)
+    where
+        T: Tracer,
+    {
+        if self
+            .name()
+            .map_or(false, |name| context.is_stdint_type(name))
+        {
+            // These types are special-cased in codegen and don't need to be traversed.
+            return;
+        }
+        match *self.kind() {
+            TypeKind::Pointer(inner) |
+            TypeKind::Reference(inner) |
+            TypeKind::Array(inner, _) |
+            TypeKind::Vector(inner, _) |
+            TypeKind::BlockPointer(inner) |
+            TypeKind::Alias(inner) |
+            TypeKind::ResolvedTypeRef(inner) => {
+                tracer.visit_kind(inner.into(), EdgeKind::TypeReference);
+            }
+            TypeKind::TemplateAlias(inner, ref template_params) => {
+                tracer.visit_kind(inner.into(), EdgeKind::TypeReference);
+                for param in template_params {
+                    tracer.visit_kind(
+                        param.into(),
+                        EdgeKind::TemplateParameterDefinition,
+                    );
+                }
+            }
+            TypeKind::TemplateInstantiation(ref inst) => {
+                inst.trace(context, tracer, &());
+            }
+            TypeKind::Comp(ref ci) => ci.trace(context, tracer, item),
+            TypeKind::Function(ref sig) => sig.trace(context, tracer, &()),
+            TypeKind::Enum(ref en) => {
+                if let Some(repr) = en.repr() {
+                    tracer.visit(repr.into());
+                }
+            }
+            TypeKind::UnresolvedTypeRef(_, _, Some(id)) => {
+                tracer.visit(id);
+            }
+
+            TypeKind::ObjCInterface(ref interface) => {
+                interface.trace(context, tracer, &());
+            }
+
+            // None of these variants have edges to other items and types.
+            TypeKind::Opaque |
+            TypeKind::UnresolvedTypeRef(_, _, None) |
+            TypeKind::TypeParam |
+            TypeKind::Void |
+            TypeKind::NullPtr |
+            TypeKind::Int(_) |
+            TypeKind::Float(_) |
+            TypeKind::Complex(_) |
+            TypeKind::ObjCId |
+            TypeKind::ObjCSel => {}
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/ir/var.rs b/third_party/rust/bindgen/ir/var.rs
new file mode 100644
index 0000000000..a548ec881b
--- /dev/null
+++ b/third_party/rust/bindgen/ir/var.rs
@@ -0,0 +1,488 @@
+//! Intermediate representation of variables.
+
+use super::super::codegen::MacroTypeVariation;
+use super::context::{BindgenContext, TypeId};
+use super::dot::DotAttributes;
+use super::function::cursor_mangling;
+use super::int::IntKind;
+use super::item::Item;
+use super::ty::{FloatKind, TypeKind};
+use crate::callbacks::{ItemInfo, ItemKind, MacroParsingBehavior};
+use crate::clang;
+use crate::clang::ClangToken;
+use crate::parse::{ClangSubItemParser, ParseError, ParseResult};
+
+use std::io;
+use std::num::Wrapping;
+
+/// The type for a constant variable.
+#[derive(Debug)]
+pub(crate) enum VarType {
+    /// A boolean.
+    Bool(bool),
+    /// An integer.
+    Int(i64),
+    /// A floating point number.
+    Float(f64),
+    /// A character.
+    Char(u8),
+    /// A string, not necessarily well-formed utf-8.
+    String(Vec<u8>),
+}
+
+/// A `Var` is our intermediate representation of a variable.
+#[derive(Debug)]
+pub(crate) struct Var {
+    /// The name of the variable.
+    name: String,
+    /// The mangled name of the variable.
+    mangled_name: Option<String>,
+    /// The link name of the variable.
+    link_name: Option<String>,
+    /// The type of the variable.
+    ty: TypeId,
+    /// The value of the variable, that needs to be suitable for `ty`.
+    val: Option<VarType>,
+    /// Whether this variable is const.
+    is_const: bool,
+}
+
+impl Var {
+    /// Construct a new `Var`.
+    pub(crate) fn new(
+        name: String,
+        mangled_name: Option<String>,
+        link_name: Option<String>,
+        ty: TypeId,
+        val: Option<VarType>,
+        is_const: bool,
+    ) -> Var {
+        assert!(!name.is_empty());
+        Var {
+            name,
+            mangled_name,
+            link_name,
+            ty,
+            val,
+            is_const,
+        }
+    }
+
+    /// Is this variable `const` qualified?
+    pub(crate) fn is_const(&self) -> bool {
+        self.is_const
+    }
+
+    /// The value of this constant variable, if any.
+    pub(crate) fn val(&self) -> Option<&VarType> {
+        self.val.as_ref()
+    }
+
+    /// Get this variable's type.
+    pub(crate) fn ty(&self) -> TypeId {
+        self.ty
+    }
+
+    /// Get this variable's name.
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Get this variable's mangled name.
+    pub(crate) fn mangled_name(&self) -> Option<&str> {
+        self.mangled_name.as_deref()
+    }
+
+    /// Get this variable's link name.
+    pub fn link_name(&self) -> Option<&str> {
+        self.link_name.as_deref()
+    }
+}
+
+impl DotAttributes for Var {
+    fn dot_attributes<W>(
+        &self,
+        _ctx: &BindgenContext,
+        out: &mut W,
+    ) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        if self.is_const {
+            writeln!(out, "<tr><td>const</td><td>true</td></tr>")?;
+        }
+
+        if let Some(ref mangled) = self.mangled_name {
+            writeln!(
+                out,
+                "<tr><td>mangled name</td><td>{}</td></tr>",
+                mangled
+            )?;
+        }
+
+        Ok(())
+    }
+}
+
+fn default_macro_constant_type(ctx: &BindgenContext, value: i64) -> IntKind {
+    if value < 0 ||
+        ctx.options().default_macro_constant_type ==
+            MacroTypeVariation::Signed
+    {
+        if value < i32::min_value() as i64 || value > i32::max_value() as i64 {
+            IntKind::I64
+        } else if !ctx.options().fit_macro_constants ||
+            value < i16::min_value() as i64 ||
+            value > i16::max_value() as i64
+        {
+            IntKind::I32
+        } else if value < i8::min_value() as i64 ||
+            value > i8::max_value() as i64
+        {
+            IntKind::I16
+        } else {
+            IntKind::I8
+        }
+    } else if value > u32::max_value() as i64 {
+        IntKind::U64
+    } else if !ctx.options().fit_macro_constants ||
+        value > u16::max_value() as i64
+    {
+        IntKind::U32
+    } else if value > u8::max_value() as i64 {
+        IntKind::U16
+    } else {
+        IntKind::U8
+    }
+}
+
+/// Parses tokens from a CXCursor_MacroDefinition pointing into a function-like
+/// macro, and calls the func_macro callback.
+fn handle_function_macro(
+    cursor: &clang::Cursor,
+    callbacks: &dyn crate::callbacks::ParseCallbacks,
+) {
+    let is_closing_paren = |t: &ClangToken| {
+        // Test cheap token kind before comparing exact spellings.
+        t.kind == clang_sys::CXToken_Punctuation && t.spelling() == b")"
+    };
+    let tokens: Vec<_> = cursor.tokens().iter().collect();
+    if let Some(boundary) = tokens.iter().position(is_closing_paren) {
+        let mut spelled = tokens.iter().map(ClangToken::spelling);
+        // Add 1, to convert index to length.
+        let left = spelled.by_ref().take(boundary + 1);
+        let left = left.collect::<Vec<_>>().concat();
+        if let Ok(left) = String::from_utf8(left) {
+            let right: Vec<_> = spelled.collect();
+            callbacks.func_macro(&left, &right);
+        }
+    }
+}
+
+impl ClangSubItemParser for Var {
+    fn parse(
+        cursor: clang::Cursor,
+        ctx: &mut BindgenContext,
+    ) -> Result<ParseResult<Self>, ParseError> {
+        use cexpr::expr::EvalResult;
+        use cexpr::literal::CChar;
+        use clang_sys::*;
+        match cursor.kind() {
+            CXCursor_MacroDefinition => {
+                for callbacks in &ctx.options().parse_callbacks {
+                    match callbacks.will_parse_macro(&cursor.spelling()) {
+                        MacroParsingBehavior::Ignore => {
+                            return Err(ParseError::Continue);
+                        }
+                        MacroParsingBehavior::Default => {}
+                    }
+
+                    if cursor.is_macro_function_like() {
+                        handle_function_macro(&cursor, callbacks.as_ref());
+                        // We handled the macro, skip macro processing below.
+                        return Err(ParseError::Continue);
+                    }
+                }
+
+                let value = parse_macro(ctx, &cursor);
+
+                let (id, value) = match value {
+                    Some(v) => v,
+                    None => return Err(ParseError::Continue),
+                };
+
+                assert!(!id.is_empty(), "Empty macro name?");
+
+                let previously_defined = ctx.parsed_macro(&id);
+
+                // NB: It's important to "note" the macro even if the result is
+                // not an integer, otherwise we might loose other kind of
+                // derived macros.
+                ctx.note_parsed_macro(id.clone(), value.clone());
+
+                if previously_defined {
+                    let name = String::from_utf8(id).unwrap();
+                    duplicated_macro_diagnostic(&name, cursor.location(), ctx);
+                    return Err(ParseError::Continue);
+                }
+
+                // NOTE: Unwrapping, here and above, is safe, because the
+                // identifier of a token comes straight from clang, and we
+                // enforce utf8 there, so we should have already panicked at
+                // this point.
+                let name = String::from_utf8(id).unwrap();
+                let (type_kind, val) = match value {
+                    EvalResult::Invalid => return Err(ParseError::Continue),
+                    EvalResult::Float(f) => {
+                        (TypeKind::Float(FloatKind::Double), VarType::Float(f))
+                    }
+                    EvalResult::Char(c) => {
+                        let c = match c {
+                            CChar::Char(c) => {
+                                assert_eq!(c.len_utf8(), 1);
+                                c as u8
+                            }
+                            CChar::Raw(c) => {
+                                assert!(c <= ::std::u8::MAX as u64);
+                                c as u8
+                            }
+                        };
+
+                        (TypeKind::Int(IntKind::U8), VarType::Char(c))
+                    }
+                    EvalResult::Str(val) => {
+                        let char_ty = Item::builtin_type(
+                            TypeKind::Int(IntKind::U8),
+                            true,
+                            ctx,
+                        );
+                        for callbacks in &ctx.options().parse_callbacks {
+                            callbacks.str_macro(&name, &val);
+                        }
+                        (TypeKind::Pointer(char_ty), VarType::String(val))
+                    }
+                    EvalResult::Int(Wrapping(value)) => {
+                        let kind = ctx
+                            .options()
+                            .last_callback(|c| c.int_macro(&name, value))
+                            .unwrap_or_else(|| {
+                                default_macro_constant_type(ctx, value)
+                            });
+
+                        (TypeKind::Int(kind), VarType::Int(value))
+                    }
+                };
+
+                let ty = Item::builtin_type(type_kind, true, ctx);
+
+                Ok(ParseResult::New(
+                    Var::new(name, None, None, ty, Some(val), true),
+                    Some(cursor),
+                ))
+            }
+            CXCursor_VarDecl => {
+                let mut name = cursor.spelling();
+                if cursor.linkage() == CXLinkage_External {
+                    if let Some(nm) = ctx.options().last_callback(|callbacks| {
+                        callbacks.generated_name_override(ItemInfo {
+                            name: name.as_str(),
+                            kind: ItemKind::Var,
+                        })
+                    }) {
+                        name = nm;
+                    }
+                }
+                // No more changes to name
+                let name = name;
+
+                if name.is_empty() {
+                    warn!("Empty constant name?");
+                    return Err(ParseError::Continue);
+                }
+
+                let link_name = ctx.options().last_callback(|callbacks| {
+                    callbacks.generated_link_name_override(ItemInfo {
+                        name: name.as_str(),
+                        kind: ItemKind::Var,
+                    })
+                });
+
+                let ty = cursor.cur_type();
+
+                // TODO(emilio): do we have to special-case constant arrays in
+                // some other places?
+                let is_const = ty.is_const() ||
+                    ([CXType_ConstantArray, CXType_IncompleteArray]
+                        .contains(&ty.kind()) &&
+                        ty.elem_type()
+                            .map_or(false, |element| element.is_const()));
+
+                let ty = match Item::from_ty(&ty, cursor, None, ctx) {
+                    Ok(ty) => ty,
+                    Err(e) => {
+                        assert!(
+                            matches!(ty.kind(), CXType_Auto | CXType_Unexposed),
+                            "Couldn't resolve constant type, and it \
+                             wasn't an nondeductible auto type or unexposed \
+                             type!"
+                        );
+                        return Err(e);
+                    }
+                };
+
+                // Note: Ty might not be totally resolved yet, see
+                // tests/headers/inner_const.hpp
+                //
+                // That's fine because in that case we know it's not a literal.
+                let canonical_ty = ctx
+                    .safe_resolve_type(ty)
+                    .and_then(|t| t.safe_canonical_type(ctx));
+
+                let is_integer = canonical_ty.map_or(false, |t| t.is_integer());
+                let is_float = canonical_ty.map_or(false, |t| t.is_float());
+
+                // TODO: We could handle `char` more gracefully.
+                // TODO: Strings, though the lookup is a bit more hard (we need
+                // to look at the canonical type of the pointee too, and check
+                // is char, u8, or i8 I guess).
+                let value = if is_integer {
+                    let kind = match *canonical_ty.unwrap().kind() {
+                        TypeKind::Int(kind) => kind,
+                        _ => unreachable!(),
+                    };
+
+                    let mut val = cursor.evaluate().and_then(|v| v.as_int());
+                    if val.is_none() || !kind.signedness_matches(val.unwrap()) {
+                        val = get_integer_literal_from_cursor(&cursor);
+                    }
+
+                    val.map(|val| {
+                        if kind == IntKind::Bool {
+                            VarType::Bool(val != 0)
+                        } else {
+                            VarType::Int(val)
+                        }
+                    })
+                } else if is_float {
+                    cursor
+                        .evaluate()
+                        .and_then(|v| v.as_double())
+                        .map(VarType::Float)
+                } else {
+                    cursor
+                        .evaluate()
+                        .and_then(|v| v.as_literal_string())
+                        .map(VarType::String)
+                };
+
+                let mangling = cursor_mangling(ctx, &cursor);
+                let var =
+                    Var::new(name, mangling, link_name, ty, value, is_const);
+
+                Ok(ParseResult::New(var, Some(cursor)))
+            }
+            _ => {
+                /* TODO */
+                Err(ParseError::Continue)
+            }
+        }
+    }
+}
+
+/// Try and parse a macro using all the macros parsed until now.
+fn parse_macro(
+    ctx: &BindgenContext,
+    cursor: &clang::Cursor,
+) -> Option<(Vec<u8>, cexpr::expr::EvalResult)> {
+    use cexpr::expr;
+
+    let cexpr_tokens = cursor.cexpr_tokens();
+
+    let parser = expr::IdentifierParser::new(ctx.parsed_macros());
+
+    match parser.macro_definition(&cexpr_tokens) {
+        Ok((_, (id, val))) => Some((id.into(), val)),
+        _ => None,
+    }
+}
+
+fn parse_int_literal_tokens(cursor: &clang::Cursor) -> Option<i64> {
+    use cexpr::expr;
+    use cexpr::expr::EvalResult;
+
+    let cexpr_tokens = cursor.cexpr_tokens();
+
+    // TODO(emilio): We can try to parse other kinds of literals.
+    match expr::expr(&cexpr_tokens) {
+        Ok((_, EvalResult::Int(Wrapping(val)))) => Some(val),
+        _ => None,
+    }
+}
+
+fn get_integer_literal_from_cursor(cursor: &clang::Cursor) -> Option<i64> {
+    use clang_sys::*;
+    let mut value = None;
+    cursor.visit(|c| {
+        match c.kind() {
+            CXCursor_IntegerLiteral | CXCursor_UnaryOperator => {
+                value = parse_int_literal_tokens(&c);
+            }
+            CXCursor_UnexposedExpr => {
+                value = get_integer_literal_from_cursor(&c);
+            }
+            _ => (),
+        }
+        if value.is_some() {
+            CXChildVisit_Break
+        } else {
+            CXChildVisit_Continue
+        }
+    });
+    value
+}
+
+fn duplicated_macro_diagnostic(
+    macro_name: &str,
+    _location: crate::clang::SourceLocation,
+    _ctx: &BindgenContext,
+) {
+    warn!("Duplicated macro definition: {}", macro_name);
+
+    #[cfg(feature = "experimental")]
+    // FIXME (pvdrz & amanjeev): This diagnostic message shows way too often to be actually
+    // useful. We have to change the logic where this function is called to be able to emit this
+    // message only when the duplication is an actuall issue.
+    //
+    // If I understood correctly, `bindgen` ignores all `#undef` directives. Meaning that this:
+    // ```c
+    // #define FOO 1
+    // #undef FOO
+    // #define FOO 2
+    // ```
+    //
+    // Will trigger this message even though there's nothing wrong with it.
+    #[allow(clippy::overly_complex_bool_expr)]
+    if false && _ctx.options().emit_diagnostics {
+        use crate::diagnostics::{get_line, Diagnostic, Level, Slice};
+        use std::borrow::Cow;
+
+        let mut slice = Slice::default();
+        let mut source = Cow::from(macro_name);
+
+        let (file, line, col, _) = _location.location();
+        if let Some(filename) = file.name() {
+            if let Ok(Some(code)) = get_line(&filename, line) {
+                source = code.into();
+            }
+            slice.with_location(filename, line, col);
+        }
+
+        slice.with_source(source);
+
+        Diagnostic::default()
+            .with_title("Duplicated macro definition.", Level::Warn)
+            .add_slice(slice)
+            .add_annotation("This macro had a duplicate.", Level::Note)
+            .display();
+    }
+}
diff --git a/third_party/rust/bindgen/lib.rs b/third_party/rust/bindgen/lib.rs
new file mode 100644
index 0000000000..c4ab11486c
--- /dev/null
+++ b/third_party/rust/bindgen/lib.rs
@@ -0,0 +1,1380 @@
+//! Generate Rust bindings for C and C++ libraries.
+//!
+//! Provide a C/C++ header file, receive Rust FFI code to call into C/C++
+//! functions and use types defined in the header.
+//!
+//! See the [`Builder`](./struct.Builder.html) struct for usage.
+//!
+//! See the [Users Guide](https://rust-lang.github.io/rust-bindgen/) for
+//! additional documentation.
+#![deny(missing_docs)]
+#![deny(unused_extern_crates)]
+#![deny(clippy::disallowed_methods)]
+// To avoid rather annoying warnings when matching with CXCursor_xxx as a
+// constant.
+#![allow(non_upper_case_globals)]
+// `quote!` nests quite deeply.
+#![recursion_limit = "128"]
+
+#[macro_use]
+extern crate bitflags;
+#[macro_use]
+extern crate lazy_static;
+#[macro_use]
+extern crate quote;
+
+#[cfg(feature = "logging")]
+#[macro_use]
+extern crate log;
+
+#[cfg(not(feature = "logging"))]
+#[macro_use]
+mod log_stubs;
+
+#[macro_use]
+mod extra_assertions;
+
+mod codegen;
+mod deps;
+mod options;
+mod time;
+
+pub mod callbacks;
+
+mod clang;
+#[cfg(feature = "experimental")]
+mod diagnostics;
+mod features;
+mod ir;
+mod parse;
+mod regex_set;
+
+pub use codegen::{
+    AliasVariation, EnumVariation, MacroTypeVariation, NonCopyUnionStyle,
+};
+#[cfg(feature = "__cli")]
+pub use features::RUST_TARGET_STRINGS;
+pub use features::{RustTarget, LATEST_STABLE_RUST};
+pub use ir::annotations::FieldVisibilityKind;
+pub use ir::function::Abi;
+pub use regex_set::RegexSet;
+
+use codegen::CodegenError;
+use features::RustFeatures;
+use ir::comment;
+use ir::context::{BindgenContext, ItemId};
+use ir::item::Item;
+use options::BindgenOptions;
+use parse::ParseError;
+
+use std::borrow::Cow;
+use std::collections::hash_map::Entry;
+use std::env;
+use std::ffi::OsStr;
+use std::fs::{File, OpenOptions};
+use std::io::{self, Write};
+use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio};
+use std::rc::Rc;
+use std::str::FromStr;
+
+// Some convenient typedefs for a fast hash map and hash set.
+type HashMap<K, V> = rustc_hash::FxHashMap<K, V>;
+type HashSet<K> = rustc_hash::FxHashSet<K>;
+
+/// Default prefix for the anon fields.
+pub const DEFAULT_ANON_FIELDS_PREFIX: &str = "__bindgen_anon_";
+
+const DEFAULT_NON_EXTERN_FNS_SUFFIX: &str = "__extern";
+
+fn file_is_cpp(name_file: &str) -> bool {
+    name_file.ends_with(".hpp") ||
+        name_file.ends_with(".hxx") ||
+        name_file.ends_with(".hh") ||
+        name_file.ends_with(".h++")
+}
+
+fn args_are_cpp(clang_args: &[Box<str>]) -> bool {
+    for w in clang_args.windows(2) {
+        if w[0].as_ref() == "-xc++" || w[1].as_ref() == "-xc++" {
+            return true;
+        }
+        if w[0].as_ref() == "-x" && w[1].as_ref() == "c++" {
+            return true;
+        }
+        if w[0].as_ref() == "-include" && file_is_cpp(w[1].as_ref()) {
+            return true;
+        }
+    }
+    false
+}
+
+bitflags! {
+    /// A type used to indicate which kind of items we have to generate.
+    #[derive(Copy, Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+    pub struct CodegenConfig: u32 {
+        /// Whether to generate functions.
+        const FUNCTIONS = 1 << 0;
+        /// Whether to generate types.
+        const TYPES = 1 << 1;
+        /// Whether to generate constants.
+        const VARS = 1 << 2;
+        /// Whether to generate methods.
+        const METHODS = 1 << 3;
+        /// Whether to generate constructors
+        const CONSTRUCTORS = 1 << 4;
+        /// Whether to generate destructors.
+        const DESTRUCTORS = 1 << 5;
+    }
+}
+
+impl CodegenConfig {
+    /// Returns true if functions should be generated.
+    pub fn functions(self) -> bool {
+        self.contains(CodegenConfig::FUNCTIONS)
+    }
+
+    /// Returns true if types should be generated.
+    pub fn types(self) -> bool {
+        self.contains(CodegenConfig::TYPES)
+    }
+
+    /// Returns true if constants should be generated.
+    pub fn vars(self) -> bool {
+        self.contains(CodegenConfig::VARS)
+    }
+
+    /// Returns true if methds should be generated.
+    pub fn methods(self) -> bool {
+        self.contains(CodegenConfig::METHODS)
+    }
+
+    /// Returns true if constructors should be generated.
+    pub fn constructors(self) -> bool {
+        self.contains(CodegenConfig::CONSTRUCTORS)
+    }
+
+    /// Returns true if destructors should be generated.
+    pub fn destructors(self) -> bool {
+        self.contains(CodegenConfig::DESTRUCTORS)
+    }
+}
+
+impl Default for CodegenConfig {
+    fn default() -> Self {
+        CodegenConfig::all()
+    }
+}
+
+/// Formatting tools that can be used to format the bindings
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum Formatter {
+    /// Do not format the bindings.
+    None,
+    /// Use `rustfmt` to format the bindings.
+    Rustfmt,
+    #[cfg(feature = "prettyplease")]
+    /// Use `prettyplease` to format the bindings.
+    Prettyplease,
+}
+
+impl Default for Formatter {
+    fn default() -> Self {
+        Self::Rustfmt
+    }
+}
+
+impl FromStr for Formatter {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "none" => Ok(Self::None),
+            "rustfmt" => Ok(Self::Rustfmt),
+            #[cfg(feature = "prettyplease")]
+            "prettyplease" => Ok(Self::Prettyplease),
+            _ => Err(format!("`{}` is not a valid formatter", s)),
+        }
+    }
+}
+
+impl std::fmt::Display for Formatter {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let s = match self {
+            Self::None => "none",
+            Self::Rustfmt => "rustfmt",
+            #[cfg(feature = "prettyplease")]
+            Self::Prettyplease => "prettyplease",
+        };
+
+        s.fmt(f)
+    }
+}
+
+/// Configure and generate Rust bindings for a C/C++ header.
+///
+/// This is the main entry point to the library.
+///
+/// ```ignore
+/// use bindgen::builder;
+///
+/// // Configure and generate bindings.
+/// let bindings = builder().header("path/to/input/header")
+///     .allowlist_type("SomeCoolClass")
+///     .allowlist_function("do_some_cool_thing")
+///     .generate()?;
+///
+/// // Write the generated bindings to an output file.
+/// bindings.write_to_file("path/to/output.rs")?;
+/// ```
+///
+/// # Enums
+///
+/// Bindgen can map C/C++ enums into Rust in different ways. The way bindgen maps enums depends on
+/// the pattern passed to several methods:
+///
+/// 1. [`constified_enum_module()`](#method.constified_enum_module)
+/// 2. [`bitfield_enum()`](#method.bitfield_enum)
+/// 3. [`newtype_enum()`](#method.newtype_enum)
+/// 4. [`rustified_enum()`](#method.rustified_enum)
+///
+/// For each C enum, bindgen tries to match the pattern in the following order:
+///
+/// 1. Constified enum module
+/// 2. Bitfield enum
+/// 3. Newtype enum
+/// 4. Rustified enum
+///
+/// If none of the above patterns match, then bindgen will generate a set of Rust constants.
+///
+/// # Clang arguments
+///
+/// Extra arguments can be passed to with clang:
+/// 1. [`clang_arg()`](#method.clang_arg): takes a single argument
+/// 2. [`clang_args()`](#method.clang_args): takes an iterator of arguments
+/// 3. `BINDGEN_EXTRA_CLANG_ARGS` environment variable: whitespace separate
+///    environment variable of arguments
+///
+/// Clang arguments specific to your crate should be added via the
+/// `clang_arg()`/`clang_args()` methods.
+///
+/// End-users of the crate may need to set the `BINDGEN_EXTRA_CLANG_ARGS` environment variable to
+/// add additional arguments. For example, to build against a different sysroot a user could set
+/// `BINDGEN_EXTRA_CLANG_ARGS` to `--sysroot=/path/to/sysroot`.
+///
+/// # Regular expression arguments
+///
+/// Some [`Builder`] methods, such as `allowlist_*` and `blocklist_*`, allow regular
+/// expressions as arguments. These regular expressions will be enclosed in parentheses and
+/// anchored with `^` and `$`. So, if the argument passed is `<regex>`, the regular expression to be
+/// stored will be `^(<regex>)$`.
+///
+/// As a consequence, regular expressions passed to `bindgen` will try to match the whole name of
+/// an item instead of a section of it, which means that to match any items with the prefix
+/// `prefix`, the `prefix.*` regular expression must be used.
+///
+/// Certain methods, like [`Builder::allowlist_function`], use regular expressions over function
+/// names. To match C++ methods, prefix the name of the type where they belong, followed by an
+/// underscore. So, if the type `Foo` has a method `bar`, it can be matched with the `Foo_bar`
+/// regular expression.
+///
+/// Additionally, Objective-C interfaces can be matched by prefixing the regular expression with
+/// `I`. For example, the `IFoo` regular expression matches the `Foo` interface, and the `IFoo_foo`
+/// regular expression matches the `foo` method of the `Foo` interface.
+///
+/// Releases of `bindgen` with a version lesser or equal to `0.62.0` used to accept the wildcard
+/// pattern `*` as a valid regular expression. This behavior has been deprecated, and the `.*`
+/// regular expression must be used instead.
+#[derive(Debug, Default, Clone)]
+pub struct Builder {
+    options: BindgenOptions,
+}
+
+/// Construct a new [`Builder`](./struct.Builder.html).
+pub fn builder() -> Builder {
+    Default::default()
+}
+
+fn get_extra_clang_args(
+    parse_callbacks: &[Rc<dyn callbacks::ParseCallbacks>],
+) -> Vec<String> {
+    // Add any extra arguments from the environment to the clang command line.
+    let extra_clang_args = match get_target_dependent_env_var(
+        parse_callbacks,
+        "BINDGEN_EXTRA_CLANG_ARGS",
+    ) {
+        None => return vec![],
+        Some(s) => s,
+    };
+
+    // Try to parse it with shell quoting. If we fail, make it one single big argument.
+    if let Some(strings) = shlex::split(&extra_clang_args) {
+        return strings;
+    }
+    vec![extra_clang_args]
+}
+
+impl Builder {
+    /// Generate the Rust bindings using the options built up thus far.
+    pub fn generate(mut self) -> Result<Bindings, BindgenError> {
+        // Add any extra arguments from the environment to the clang command line.
+        self.options.clang_args.extend(
+            get_extra_clang_args(&self.options.parse_callbacks)
+                .into_iter()
+                .map(String::into_boxed_str),
+        );
+
+        for header in &self.options.input_headers {
+            self.options
+                .for_each_callback(|cb| cb.header_file(header.as_ref()));
+        }
+
+        // Transform input headers to arguments on the clang command line.
+        self.options.clang_args.extend(
+            self.options.input_headers
+                [..self.options.input_headers.len().saturating_sub(1)]
+                .iter()
+                .flat_map(|header| ["-include".into(), header.clone()]),
+        );
+
+        let input_unsaved_files =
+            std::mem::take(&mut self.options.input_header_contents)
+                .into_iter()
+                .map(|(name, contents)| {
+                    clang::UnsavedFile::new(name.as_ref(), contents.as_ref())
+                })
+                .collect::<Vec<_>>();
+
+        Bindings::generate(self.options, input_unsaved_files)
+    }
+
+    /// Preprocess and dump the input header files to disk.
+    ///
+    /// This is useful when debugging bindgen, using C-Reduce, or when filing
+    /// issues. The resulting file will be named something like `__bindgen.i` or
+    /// `__bindgen.ii`
+    pub fn dump_preprocessed_input(&self) -> io::Result<()> {
+        let clang =
+            clang_sys::support::Clang::find(None, &[]).ok_or_else(|| {
+                io::Error::new(
+                    io::ErrorKind::Other,
+                    "Cannot find clang executable",
+                )
+            })?;
+
+        // The contents of a wrapper file that includes all the input header
+        // files.
+        let mut wrapper_contents = String::new();
+
+        // Whether we are working with C or C++ inputs.
+        let mut is_cpp = args_are_cpp(&self.options.clang_args);
+
+        // For each input header, add `#include "$header"`.
+        for header in &self.options.input_headers {
+            is_cpp |= file_is_cpp(header);
+
+            wrapper_contents.push_str("#include \"");
+            wrapper_contents.push_str(header);
+            wrapper_contents.push_str("\"\n");
+        }
+
+        // For each input header content, add a prefix line of `#line 0 "$name"`
+        // followed by the contents.
+        for (name, contents) in &self.options.input_header_contents {
+            is_cpp |= file_is_cpp(name);
+
+            wrapper_contents.push_str("#line 0 \"");
+            wrapper_contents.push_str(name);
+            wrapper_contents.push_str("\"\n");
+            wrapper_contents.push_str(contents);
+        }
+
+        let wrapper_path = PathBuf::from(if is_cpp {
+            "__bindgen.cpp"
+        } else {
+            "__bindgen.c"
+        });
+
+        {
+            let mut wrapper_file = File::create(&wrapper_path)?;
+            wrapper_file.write_all(wrapper_contents.as_bytes())?;
+        }
+
+        let mut cmd = Command::new(clang.path);
+        cmd.arg("-save-temps")
+            .arg("-E")
+            .arg("-C")
+            .arg("-c")
+            .arg(&wrapper_path)
+            .stdout(Stdio::piped());
+
+        for a in &self.options.clang_args {
+            cmd.arg(a.as_ref());
+        }
+
+        for a in get_extra_clang_args(&self.options.parse_callbacks) {
+            cmd.arg(a);
+        }
+
+        let mut child = cmd.spawn()?;
+
+        let mut preprocessed = child.stdout.take().unwrap();
+        let mut file = File::create(if is_cpp {
+            "__bindgen.ii"
+        } else {
+            "__bindgen.i"
+        })?;
+        io::copy(&mut preprocessed, &mut file)?;
+
+        if child.wait()?.success() {
+            Ok(())
+        } else {
+            Err(io::Error::new(
+                io::ErrorKind::Other,
+                "clang exited with non-zero status",
+            ))
+        }
+    }
+}
+
+impl BindgenOptions {
+    fn build(&mut self) {
+        const REGEX_SETS_LEN: usize = 29;
+
+        let regex_sets: [_; REGEX_SETS_LEN] = [
+            &mut self.blocklisted_types,
+            &mut self.blocklisted_functions,
+            &mut self.blocklisted_items,
+            &mut self.blocklisted_files,
+            &mut self.blocklisted_vars,
+            &mut self.opaque_types,
+            &mut self.allowlisted_vars,
+            &mut self.allowlisted_types,
+            &mut self.allowlisted_functions,
+            &mut self.allowlisted_files,
+            &mut self.allowlisted_items,
+            &mut self.bitfield_enums,
+            &mut self.constified_enums,
+            &mut self.constified_enum_modules,
+            &mut self.newtype_enums,
+            &mut self.newtype_global_enums,
+            &mut self.rustified_enums,
+            &mut self.rustified_non_exhaustive_enums,
+            &mut self.type_alias,
+            &mut self.new_type_alias,
+            &mut self.new_type_alias_deref,
+            &mut self.bindgen_wrapper_union,
+            &mut self.manually_drop_union,
+            &mut self.no_partialeq_types,
+            &mut self.no_copy_types,
+            &mut self.no_debug_types,
+            &mut self.no_default_types,
+            &mut self.no_hash_types,
+            &mut self.must_use_types,
+        ];
+
+        let record_matches = self.record_matches;
+        #[cfg(feature = "experimental")]
+        {
+            let sets_len = REGEX_SETS_LEN + self.abi_overrides.len();
+            let names = if self.emit_diagnostics {
+                <[&str; REGEX_SETS_LEN]>::into_iter([
+                    "--blocklist-type",
+                    "--blocklist-function",
+                    "--blocklist-item",
+                    "--blocklist-file",
+                    "--blocklist-var",
+                    "--opaque-type",
+                    "--allowlist-type",
+                    "--allowlist-function",
+                    "--allowlist-var",
+                    "--allowlist-file",
+                    "--allowlist-item",
+                    "--bitfield-enum",
+                    "--newtype-enum",
+                    "--newtype-global-enum",
+                    "--rustified-enum",
+                    "--rustified-enum-non-exhaustive",
+                    "--constified-enum-module",
+                    "--constified-enum",
+                    "--type-alias",
+                    "--new-type-alias",
+                    "--new-type-alias-deref",
+                    "--bindgen-wrapper-union",
+                    "--manually-drop-union",
+                    "--no-partialeq",
+                    "--no-copy",
+                    "--no-debug",
+                    "--no-default",
+                    "--no-hash",
+                    "--must-use",
+                ])
+                .chain((0..self.abi_overrides.len()).map(|_| "--override-abi"))
+                .map(Some)
+                .collect()
+            } else {
+                vec![None; sets_len]
+            };
+
+            for (regex_set, name) in
+                self.abi_overrides.values_mut().chain(regex_sets).zip(names)
+            {
+                regex_set.build_with_diagnostics(record_matches, name);
+            }
+        }
+        #[cfg(not(feature = "experimental"))]
+        for regex_set in self.abi_overrides.values_mut().chain(regex_sets) {
+            regex_set.build(record_matches);
+        }
+
+        let rust_target = self.rust_target;
+        #[allow(deprecated)]
+        if rust_target <= RustTarget::Stable_1_30 {
+            deprecated_target_diagnostic(rust_target, self);
+        }
+
+        // Disable `untagged_union` if the target does not support it.
+        if !self.rust_features.untagged_union {
+            self.untagged_union = false;
+        }
+    }
+
+    /// Update rust target version
+    pub fn set_rust_target(&mut self, rust_target: RustTarget) {
+        self.rust_target = rust_target;
+
+        // Keep rust_features synced with rust_target
+        self.rust_features = rust_target.into();
+    }
+
+    /// Get features supported by target Rust version
+    pub fn rust_features(&self) -> RustFeatures {
+        self.rust_features
+    }
+
+    fn last_callback<T>(
+        &self,
+        f: impl Fn(&dyn callbacks::ParseCallbacks) -> Option<T>,
+    ) -> Option<T> {
+        self.parse_callbacks
+            .iter()
+            .filter_map(|cb| f(cb.as_ref()))
+            .last()
+    }
+
+    fn all_callbacks<T>(
+        &self,
+        f: impl Fn(&dyn callbacks::ParseCallbacks) -> Vec<T>,
+    ) -> Vec<T> {
+        self.parse_callbacks
+            .iter()
+            .flat_map(|cb| f(cb.as_ref()))
+            .collect()
+    }
+
+    fn for_each_callback(&self, f: impl Fn(&dyn callbacks::ParseCallbacks)) {
+        self.parse_callbacks.iter().for_each(|cb| f(cb.as_ref()));
+    }
+
+    fn process_comment(&self, comment: &str) -> String {
+        let comment = comment::preprocess(comment);
+        self.parse_callbacks
+            .last()
+            .and_then(|cb| cb.process_comment(&comment))
+            .unwrap_or(comment)
+    }
+}
+
+fn deprecated_target_diagnostic(target: RustTarget, _options: &BindgenOptions) {
+    warn!("The {} Rust target is deprecated. If you have a need to use this target please report it at https://github.com/rust-lang/rust-bindgen/issues", target);
+
+    #[cfg(feature = "experimental")]
+    if _options.emit_diagnostics {
+        use crate::diagnostics::{Diagnostic, Level};
+
+        let mut diagnostic = Diagnostic::default();
+        diagnostic.with_title(
+            format!("The {} Rust target is deprecated.", target),
+            Level::Warn,
+        );
+        diagnostic.add_annotation(
+            "This Rust target was passed to `--rust-target`",
+            Level::Info,
+        );
+        diagnostic.add_annotation("If you have a good reason to use this target please report it at https://github.com/rust-lang/rust-bindgen/issues", Level::Help);
+        diagnostic.display();
+    }
+}
+
+#[cfg(feature = "runtime")]
+fn ensure_libclang_is_loaded() {
+    if clang_sys::is_loaded() {
+        return;
+    }
+
+    // XXX (issue #350): Ensure that our dynamically loaded `libclang`
+    // doesn't get dropped prematurely, nor is loaded multiple times
+    // across different threads.
+
+    lazy_static! {
+        static ref LIBCLANG: std::sync::Arc<clang_sys::SharedLibrary> = {
+            clang_sys::load().expect("Unable to find libclang");
+            clang_sys::get_library().expect(
+                "We just loaded libclang and it had better still be \
+                 here!",
+            )
+        };
+    }
+
+    clang_sys::set_library(Some(LIBCLANG.clone()));
+}
+
+#[cfg(not(feature = "runtime"))]
+fn ensure_libclang_is_loaded() {}
+
+/// Error type for rust-bindgen.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[non_exhaustive]
+pub enum BindgenError {
+    /// The header was a folder.
+    FolderAsHeader(PathBuf),
+    /// Permissions to read the header is insufficient.
+    InsufficientPermissions(PathBuf),
+    /// The header does not exist.
+    NotExist(PathBuf),
+    /// Clang diagnosed an error.
+    ClangDiagnostic(String),
+    /// Code generation reported an error.
+    Codegen(CodegenError),
+}
+
+impl std::fmt::Display for BindgenError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            BindgenError::FolderAsHeader(h) => {
+                write!(f, "'{}' is a folder", h.display())
+            }
+            BindgenError::InsufficientPermissions(h) => {
+                write!(f, "insufficient permissions to read '{}'", h.display())
+            }
+            BindgenError::NotExist(h) => {
+                write!(f, "header '{}' does not exist.", h.display())
+            }
+            BindgenError::ClangDiagnostic(message) => {
+                write!(f, "clang diagnosed error: {}", message)
+            }
+            BindgenError::Codegen(err) => {
+                write!(f, "codegen error: {}", err)
+            }
+        }
+    }
+}
+
+impl std::error::Error for BindgenError {}
+
+/// Generated Rust bindings.
+#[derive(Debug)]
+pub struct Bindings {
+    options: BindgenOptions,
+    module: proc_macro2::TokenStream,
+}
+
+pub(crate) const HOST_TARGET: &str =
+    include_str!(concat!(env!("OUT_DIR"), "/host-target.txt"));
+
+// Some architecture triplets are different between rust and libclang, see #1211
+// and duplicates.
+fn rust_to_clang_target(rust_target: &str) -> Box<str> {
+    if rust_target.starts_with("aarch64-apple-") {
+        let mut clang_target = "arm64-apple-".to_owned();
+        clang_target
+            .push_str(rust_target.strip_prefix("aarch64-apple-").unwrap());
+        return clang_target.into();
+    } else if rust_target.starts_with("riscv64gc-") {
+        let mut clang_target = "riscv64-".to_owned();
+        clang_target.push_str(rust_target.strip_prefix("riscv64gc-").unwrap());
+        return clang_target.into();
+    } else if rust_target.ends_with("-espidf") {
+        let mut clang_target =
+            rust_target.strip_suffix("-espidf").unwrap().to_owned();
+        clang_target.push_str("-elf");
+        if clang_target.starts_with("riscv32imc-") {
+            clang_target = "riscv32-".to_owned() +
+                clang_target.strip_prefix("riscv32imc-").unwrap();
+        }
+        return clang_target.into();
+    } else if rust_target.starts_with("riscv32imc-") {
+        let mut clang_target = "riscv32-".to_owned();
+        clang_target.push_str(rust_target.strip_prefix("riscv32imc-").unwrap());
+        return clang_target.into();
+    } else if rust_target.starts_with("riscv32imac-") {
+        let mut clang_target = "riscv32-".to_owned();
+        clang_target
+            .push_str(rust_target.strip_prefix("riscv32imac-").unwrap());
+        return clang_target.into();
+    }
+    rust_target.into()
+}
+
+/// Returns the effective target, and whether it was explicitly specified on the
+/// clang flags.
+fn find_effective_target(clang_args: &[Box<str>]) -> (Box<str>, bool) {
+    let mut args = clang_args.iter();
+    while let Some(opt) = args.next() {
+        if opt.starts_with("--target=") {
+            let mut split = opt.split('=');
+            split.next();
+            return (split.next().unwrap().into(), true);
+        }
+
+        if opt.as_ref() == "-target" {
+            if let Some(target) = args.next() {
+                return (target.clone(), true);
+            }
+        }
+    }
+
+    // If we're running from a build script, try to find the cargo target.
+    if let Ok(t) = env::var("TARGET") {
+        return (rust_to_clang_target(&t), false);
+    }
+
+    (rust_to_clang_target(HOST_TARGET), false)
+}
+
+impl Bindings {
+    /// Generate bindings for the given options.
+    pub(crate) fn generate(
+        mut options: BindgenOptions,
+        input_unsaved_files: Vec<clang::UnsavedFile>,
+    ) -> Result<Bindings, BindgenError> {
+        ensure_libclang_is_loaded();
+
+        #[cfg(feature = "runtime")]
+        debug!(
+            "Generating bindings, libclang at {}",
+            clang_sys::get_library().unwrap().path().display()
+        );
+        #[cfg(not(feature = "runtime"))]
+        debug!("Generating bindings, libclang linked");
+
+        options.build();
+
+        let (effective_target, explicit_target) =
+            find_effective_target(&options.clang_args);
+
+        let is_host_build =
+            rust_to_clang_target(HOST_TARGET) == effective_target;
+
+        // NOTE: The is_host_build check wouldn't be sound normally in some
+        // cases if we were to call a binary (if you have a 32-bit clang and are
+        // building on a 64-bit system for example).  But since we rely on
+        // opening libclang.so, it has to be the same architecture and thus the
+        // check is fine.
+        if !explicit_target && !is_host_build {
+            options.clang_args.insert(
+                0,
+                format!("--target={}", effective_target).into_boxed_str(),
+            );
+        };
+
+        fn detect_include_paths(options: &mut BindgenOptions) {
+            if !options.detect_include_paths {
+                return;
+            }
+
+            // Filter out include paths and similar stuff, so we don't incorrectly
+            // promote them to `-isystem`.
+            let clang_args_for_clang_sys = {
+                let mut last_was_include_prefix = false;
+                options
+                    .clang_args
+                    .iter()
+                    .filter(|arg| {
+                        if last_was_include_prefix {
+                            last_was_include_prefix = false;
+                            return false;
+                        }
+
+                        let arg = arg.as_ref();
+
+                        // https://clang.llvm.org/docs/ClangCommandLineReference.html
+                        // -isystem and -isystem-after are harmless.
+                        if arg == "-I" || arg == "--include-directory" {
+                            last_was_include_prefix = true;
+                            return false;
+                        }
+
+                        if arg.starts_with("-I") ||
+                            arg.starts_with("--include-directory=")
+                        {
+                            return false;
+                        }
+
+                        true
+                    })
+                    .map(|arg| arg.clone().into())
+                    .collect::<Vec<_>>()
+            };
+
+            debug!(
+                "Trying to find clang with flags: {:?}",
+                clang_args_for_clang_sys
+            );
+
+            let clang = match clang_sys::support::Clang::find(
+                None,
+                &clang_args_for_clang_sys,
+            ) {
+                None => return,
+                Some(clang) => clang,
+            };
+
+            debug!("Found clang: {:?}", clang);
+
+            // Whether we are working with C or C++ inputs.
+            let is_cpp = args_are_cpp(&options.clang_args) ||
+                options.input_headers.iter().any(|h| file_is_cpp(h));
+
+            let search_paths = if is_cpp {
+                clang.cpp_search_paths
+            } else {
+                clang.c_search_paths
+            };
+
+            if let Some(search_paths) = search_paths {
+                for path in search_paths.into_iter() {
+                    if let Ok(path) = path.into_os_string().into_string() {
+                        options.clang_args.push("-isystem".into());
+                        options.clang_args.push(path.into_boxed_str());
+                    }
+                }
+            }
+        }
+
+        detect_include_paths(&mut options);
+
+        #[cfg(unix)]
+        fn can_read(perms: &std::fs::Permissions) -> bool {
+            use std::os::unix::fs::PermissionsExt;
+            perms.mode() & 0o444 > 0
+        }
+
+        #[cfg(not(unix))]
+        fn can_read(_: &std::fs::Permissions) -> bool {
+            true
+        }
+
+        if let Some(h) = options.input_headers.last() {
+            let path = Path::new(h.as_ref());
+            if let Ok(md) = std::fs::metadata(path) {
+                if md.is_dir() {
+                    return Err(BindgenError::FolderAsHeader(path.into()));
+                }
+                if !can_read(&md.permissions()) {
+                    return Err(BindgenError::InsufficientPermissions(
+                        path.into(),
+                    ));
+                }
+                options.clang_args.push(h.clone());
+            } else {
+                return Err(BindgenError::NotExist(path.into()));
+            }
+        }
+
+        for (idx, f) in input_unsaved_files.iter().enumerate() {
+            if idx != 0 || !options.input_headers.is_empty() {
+                options.clang_args.push("-include".into());
+            }
+            options.clang_args.push(f.name.to_str().unwrap().into())
+        }
+
+        debug!("Fixed-up options: {:?}", options);
+
+        let time_phases = options.time_phases;
+        let mut context = BindgenContext::new(options, &input_unsaved_files);
+
+        if is_host_build {
+            debug_assert_eq!(
+                context.target_pointer_size(),
+                std::mem::size_of::<*mut ()>(),
+                "{:?} {:?}",
+                effective_target,
+                HOST_TARGET
+            );
+        }
+
+        {
+            let _t = time::Timer::new("parse").with_output(time_phases);
+            parse(&mut context)?;
+        }
+
+        let (module, options) =
+            codegen::codegen(context).map_err(BindgenError::Codegen)?;
+
+        Ok(Bindings { options, module })
+    }
+
+    /// Write these bindings as source text to a file.
+    pub fn write_to_file<P: AsRef<Path>>(&self, path: P) -> io::Result<()> {
+        let file = OpenOptions::new()
+            .write(true)
+            .truncate(true)
+            .create(true)
+            .open(path.as_ref())?;
+        self.write(Box::new(file))?;
+        Ok(())
+    }
+
+    /// Write these bindings as source text to the given `Write`able.
+    pub fn write<'a>(&self, mut writer: Box<dyn Write + 'a>) -> io::Result<()> {
+        const NL: &str = if cfg!(windows) { "\r\n" } else { "\n" };
+
+        if !self.options.disable_header_comment {
+            let version =
+                option_env!("CARGO_PKG_VERSION").unwrap_or("(unknown version)");
+            writeln!(
+                writer,
+                "/* automatically generated by rust-bindgen {version} */{NL}",
+            )?;
+        }
+
+        for line in self.options.raw_lines.iter() {
+            writer.write_all(line.as_bytes())?;
+            writer.write_all(NL.as_bytes())?;
+        }
+
+        if !self.options.raw_lines.is_empty() {
+            writer.write_all(NL.as_bytes())?;
+        }
+
+        match self.format_tokens(&self.module) {
+            Ok(formatted_bindings) => {
+                writer.write_all(formatted_bindings.as_bytes())?;
+            }
+            Err(err) => {
+                eprintln!(
+                    "Failed to run rustfmt: {} (non-fatal, continuing)",
+                    err
+                );
+                writer.write_all(self.module.to_string().as_bytes())?;
+            }
+        }
+        Ok(())
+    }
+
+    /// Gets the rustfmt path to rustfmt the generated bindings.
+    fn rustfmt_path(&self) -> io::Result<Cow<PathBuf>> {
+        debug_assert!(matches!(self.options.formatter, Formatter::Rustfmt));
+        if let Some(ref p) = self.options.rustfmt_path {
+            return Ok(Cow::Borrowed(p));
+        }
+        if let Ok(rustfmt) = env::var("RUSTFMT") {
+            return Ok(Cow::Owned(rustfmt.into()));
+        }
+        #[cfg(feature = "which-rustfmt")]
+        match which::which("rustfmt") {
+            Ok(p) => Ok(Cow::Owned(p)),
+            Err(e) => {
+                Err(io::Error::new(io::ErrorKind::Other, format!("{}", e)))
+            }
+        }
+        #[cfg(not(feature = "which-rustfmt"))]
+        // No rustfmt binary was specified, so assume that the binary is called
+        // "rustfmt" and that it is in the user's PATH.
+        Ok(Cow::Owned("rustfmt".into()))
+    }
+
+    /// Formats a token stream with the formatter set up in `BindgenOptions`.
+    fn format_tokens(
+        &self,
+        tokens: &proc_macro2::TokenStream,
+    ) -> io::Result<String> {
+        let _t = time::Timer::new("rustfmt_generated_string")
+            .with_output(self.options.time_phases);
+
+        match self.options.formatter {
+            Formatter::None => return Ok(tokens.to_string()),
+            #[cfg(feature = "prettyplease")]
+            Formatter::Prettyplease => {
+                return Ok(prettyplease::unparse(&syn::parse_quote!(#tokens)));
+            }
+            Formatter::Rustfmt => (),
+        }
+
+        let rustfmt = self.rustfmt_path()?;
+        let mut cmd = Command::new(&*rustfmt);
+
+        cmd.stdin(Stdio::piped()).stdout(Stdio::piped());
+
+        if let Some(path) = self
+            .options
+            .rustfmt_configuration_file
+            .as_ref()
+            .and_then(|f| f.to_str())
+        {
+            cmd.args(["--config-path", path]);
+        }
+
+        let mut child = cmd.spawn()?;
+        let mut child_stdin = child.stdin.take().unwrap();
+        let mut child_stdout = child.stdout.take().unwrap();
+
+        let source = tokens.to_string();
+
+        // Write to stdin in a new thread, so that we can read from stdout on this
+        // thread. This keeps the child from blocking on writing to its stdout which
+        // might block us from writing to its stdin.
+        let stdin_handle = ::std::thread::spawn(move || {
+            let _ = child_stdin.write_all(source.as_bytes());
+            source
+        });
+
+        let mut output = vec![];
+        io::copy(&mut child_stdout, &mut output)?;
+
+        let status = child.wait()?;
+        let source = stdin_handle.join().expect(
+            "The thread writing to rustfmt's stdin doesn't do \
+             anything that could panic",
+        );
+
+        match String::from_utf8(output) {
+            Ok(bindings) => match status.code() {
+                Some(0) => Ok(bindings),
+                Some(2) => Err(io::Error::new(
+                    io::ErrorKind::Other,
+                    "Rustfmt parsing errors.".to_string(),
+                )),
+                Some(3) => {
+                    rustfmt_non_fatal_error_diagnostic(
+                        "Rustfmt could not format some lines",
+                        &self.options,
+                    );
+                    Ok(bindings)
+                }
+                _ => Err(io::Error::new(
+                    io::ErrorKind::Other,
+                    "Internal rustfmt error".to_string(),
+                )),
+            },
+            _ => Ok(source),
+        }
+    }
+}
+
+fn rustfmt_non_fatal_error_diagnostic(msg: &str, _options: &BindgenOptions) {
+    warn!("{}", msg);
+
+    #[cfg(feature = "experimental")]
+    if _options.emit_diagnostics {
+        use crate::diagnostics::{Diagnostic, Level};
+
+        Diagnostic::default()
+            .with_title(msg, Level::Warn)
+            .add_annotation(
+                "The bindings will be generated but not formatted.",
+                Level::Note,
+            )
+            .display();
+    }
+}
+
+impl std::fmt::Display for Bindings {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut bytes = vec![];
+        self.write(Box::new(&mut bytes) as Box<dyn Write>)
+            .expect("writing to a vec cannot fail");
+        f.write_str(
+            std::str::from_utf8(&bytes)
+                .expect("we should only write bindings that are valid utf-8"),
+        )
+    }
+}
+
+/// Determines whether the given cursor is in any of the files matched by the
+/// options.
+fn filter_builtins(ctx: &BindgenContext, cursor: &clang::Cursor) -> bool {
+    ctx.options().builtins || !cursor.is_builtin()
+}
+
+/// Parse one `Item` from the Clang cursor.
+fn parse_one(
+    ctx: &mut BindgenContext,
+    cursor: clang::Cursor,
+    parent: Option<ItemId>,
+) {
+    if !filter_builtins(ctx, &cursor) {
+        return;
+    }
+
+    match Item::parse(cursor, parent, ctx) {
+        Ok(..) => {}
+        Err(ParseError::Continue) => {}
+        Err(ParseError::Recurse) => {
+            cursor
+                .visit_sorted(ctx, |ctx, child| parse_one(ctx, child, parent));
+        }
+    }
+}
+
+/// Parse the Clang AST into our `Item` internal representation.
+fn parse(context: &mut BindgenContext) -> Result<(), BindgenError> {
+    use clang_sys::*;
+
+    let mut error = None;
+    for d in context.translation_unit().diags().iter() {
+        let msg = d.format();
+        let is_err = d.severity() >= CXDiagnostic_Error;
+        if is_err {
+            let error = error.get_or_insert_with(String::new);
+            error.push_str(&msg);
+            error.push('\n');
+        } else {
+            eprintln!("clang diag: {}", msg);
+        }
+    }
+
+    if let Some(message) = error {
+        return Err(BindgenError::ClangDiagnostic(message));
+    }
+
+    let cursor = context.translation_unit().cursor();
+
+    if context.options().emit_ast {
+        fn dump_if_not_builtin(cur: &clang::Cursor) -> CXChildVisitResult {
+            if !cur.is_builtin() {
+                clang::ast_dump(cur, 0)
+            } else {
+                CXChildVisit_Continue
+            }
+        }
+        cursor.visit(|cur| dump_if_not_builtin(&cur));
+    }
+
+    let root = context.root_module();
+    context.with_module(root, |ctx| {
+        cursor.visit_sorted(ctx, |ctx, child| parse_one(ctx, child, None))
+    });
+
+    assert!(
+        context.current_module() == context.root_module(),
+        "How did this happen?"
+    );
+    Ok(())
+}
+
+/// Extracted Clang version data
+#[derive(Debug)]
+pub struct ClangVersion {
+    /// Major and minor semver, if parsing was successful
+    pub parsed: Option<(u32, u32)>,
+    /// full version string
+    pub full: String,
+}
+
+/// Get the major and the minor semver numbers of Clang's version
+pub fn clang_version() -> ClangVersion {
+    ensure_libclang_is_loaded();
+
+    //Debian clang version 11.0.1-2
+    let raw_v: String = clang::extract_clang_version();
+    let split_v: Option<Vec<&str>> = raw_v
+        .split_whitespace()
+        .find(|t| t.chars().next().map_or(false, |v| v.is_ascii_digit()))
+        .map(|v| v.split('.').collect());
+    if let Some(v) = split_v {
+        if v.len() >= 2 {
+            let maybe_major = v[0].parse::<u32>();
+            let maybe_minor = v[1].parse::<u32>();
+            if let (Ok(major), Ok(minor)) = (maybe_major, maybe_minor) {
+                return ClangVersion {
+                    parsed: Some((major, minor)),
+                    full: raw_v.clone(),
+                };
+            }
+        }
+    };
+    ClangVersion {
+        parsed: None,
+        full: raw_v.clone(),
+    }
+}
+
+fn env_var<K: AsRef<str> + AsRef<OsStr>>(
+    parse_callbacks: &[Rc<dyn callbacks::ParseCallbacks>],
+    key: K,
+) -> Result<String, std::env::VarError> {
+    for callback in parse_callbacks {
+        callback.read_env_var(key.as_ref());
+    }
+    std::env::var(key)
+}
+
+/// Looks for the env var `var_${TARGET}`, and falls back to just `var` when it is not found.
+fn get_target_dependent_env_var(
+    parse_callbacks: &[Rc<dyn callbacks::ParseCallbacks>],
+    var: &str,
+) -> Option<String> {
+    if let Ok(target) = env_var(parse_callbacks, "TARGET") {
+        if let Ok(v) = env_var(parse_callbacks, format!("{}_{}", var, target)) {
+            return Some(v);
+        }
+        if let Ok(v) = env_var(
+            parse_callbacks,
+            format!("{}_{}", var, target.replace('-', "_")),
+        ) {
+            return Some(v);
+        }
+    }
+
+    env_var(parse_callbacks, var).ok()
+}
+
+/// A ParseCallbacks implementation that will act on file includes by echoing a rerun-if-changed
+/// line and on env variable usage by echoing a rerun-if-env-changed line
+///
+/// When running inside a `build.rs` script, this can be used to make cargo invalidate the
+/// generated bindings whenever any of the files included from the header change:
+/// ```
+/// use bindgen::builder;
+/// let bindings = builder()
+///     .header("path/to/input/header")
+///     .parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))
+///     .generate();
+/// ```
+#[derive(Debug)]
+pub struct CargoCallbacks {
+    rerun_on_header_files: bool,
+}
+
+/// Create a new `CargoCallbacks` value with [`CargoCallbacks::rerun_on_header_files`] disabled.
+///
+/// This constructor has been deprecated in favor of [`CargoCallbacks::new`] where
+/// [`CargoCallbacks::rerun_on_header_files`] is enabled by default.
+#[deprecated = "Use `CargoCallbacks::new()` instead. Please, check the documentation for further information."]
+pub const CargoCallbacks: CargoCallbacks = CargoCallbacks {
+    rerun_on_header_files: false,
+};
+
+impl CargoCallbacks {
+    /// Create a new `CargoCallbacks` value.
+    pub fn new() -> Self {
+        Self {
+            rerun_on_header_files: true,
+        }
+    }
+
+    /// Whether Cargo should re-run the build script if any of the input header files has changed.
+    ///
+    /// This option is enabled by default unless the deprecated [`const@CargoCallbacks`]
+    /// constructor is used.
+    pub fn rerun_on_header_files(mut self, doit: bool) -> Self {
+        self.rerun_on_header_files = doit;
+        self
+    }
+}
+
+impl Default for CargoCallbacks {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl callbacks::ParseCallbacks for CargoCallbacks {
+    fn header_file(&self, filename: &str) {
+        if self.rerun_on_header_files {
+            println!("cargo:rerun-if-changed={}", filename);
+        }
+    }
+
+    fn include_file(&self, filename: &str) {
+        println!("cargo:rerun-if-changed={}", filename);
+    }
+
+    fn read_env_var(&self, key: &str) {
+        println!("cargo:rerun-if-env-changed={}", key);
+    }
+}
+
+/// Test command_line_flag function.
+#[test]
+fn commandline_flag_unit_test_function() {
+    //Test 1
+    let bindings = crate::builder();
+    let command_line_flags = bindings.command_line_flags();
+
+    let test_cases = [
+        "--rust-target",
+        "--no-derive-default",
+        "--generate",
+        "functions,types,vars,methods,constructors,destructors",
+    ]
+    .iter()
+    .map(|&x| x.into())
+    .collect::<Vec<String>>();
+
+    assert!(test_cases.iter().all(|x| command_line_flags.contains(x)));
+
+    //Test 2
+    let bindings = crate::builder()
+        .header("input_header")
+        .allowlist_type("Distinct_Type")
+        .allowlist_function("safe_function");
+
+    let command_line_flags = bindings.command_line_flags();
+    let test_cases = [
+        "--rust-target",
+        "input_header",
+        "--no-derive-default",
+        "--generate",
+        "functions,types,vars,methods,constructors,destructors",
+        "--allowlist-type",
+        "Distinct_Type",
+        "--allowlist-function",
+        "safe_function",
+    ]
+    .iter()
+    .map(|&x| x.into())
+    .collect::<Vec<String>>();
+    println!("{:?}", command_line_flags);
+
+    assert!(test_cases.iter().all(|x| command_line_flags.contains(x)));
+}
+
+#[test]
+fn test_rust_to_clang_target() {
+    assert_eq!(
+        rust_to_clang_target("aarch64-apple-ios").as_ref(),
+        "arm64-apple-ios"
+    );
+}
+
+#[test]
+fn test_rust_to_clang_target_riscv() {
+    assert_eq!(
+        rust_to_clang_target("riscv64gc-unknown-linux-gnu").as_ref(),
+        "riscv64-unknown-linux-gnu"
+    );
+    assert_eq!(
+        rust_to_clang_target("riscv32imc-unknown-none-elf").as_ref(),
+        "riscv32-unknown-none-elf"
+    );
+    assert_eq!(
+        rust_to_clang_target("riscv32imac-unknown-none-elf").as_ref(),
+        "riscv32-unknown-none-elf"
+    );
+}
+
+#[test]
+fn test_rust_to_clang_target_espidf() {
+    assert_eq!(
+        rust_to_clang_target("riscv32imc-esp-espidf").as_ref(),
+        "riscv32-esp-elf"
+    );
+    assert_eq!(
+        rust_to_clang_target("xtensa-esp32-espidf").as_ref(),
+        "xtensa-esp32-elf"
+    );
+}
diff --git a/third_party/rust/bindgen/log_stubs.rs b/third_party/rust/bindgen/log_stubs.rs
new file mode 100644
index 0000000000..8315983128
--- /dev/null
+++ b/third_party/rust/bindgen/log_stubs.rs
@@ -0,0 +1,32 @@
+#![allow(unused)]
+
+macro_rules! log {
+    (target: $target:expr, $lvl:expr, $($arg:tt)+) => {{
+        let _ = $target;
+        let _ = log!($lvl, $($arg)+);
+    }};
+    ($lvl:expr, $($arg:tt)+) => {{
+        let _ = $lvl;
+        let _ = format_args!($($arg)+);
+    }};
+}
+macro_rules! error {
+    (target: $target:expr, $($arg:tt)+) => { log!(target: $target, "", $($arg)+) };
+    ($($arg:tt)+) => { log!("", $($arg)+) };
+}
+macro_rules! warn {
+    (target: $target:expr, $($arg:tt)*) => { log!(target: $target, "", $($arg)*) };
+    ($($arg:tt)*) => { log!("", $($arg)*) };
+}
+macro_rules! info {
+    (target: $target:expr, $($arg:tt)+) => { log!(target: $target, "", $($arg)+) };
+    ($($arg:tt)+) => { log!("", $($arg)+) };
+}
+macro_rules! debug {
+    (target: $target:expr, $($arg:tt)+) => { log!(target: $target, "", $($arg)+) };
+    ($($arg:tt)+) => { log!("", $($arg)+) };
+}
+macro_rules! trace {
+    (target: $target:expr, $($arg:tt)+) => { log!(target: $target, "", $($arg)+) };
+    ($($arg:tt)+) => { log!("", $($arg)+) };
+}
diff --git a/third_party/rust/bindgen/options/as_args.rs b/third_party/rust/bindgen/options/as_args.rs
new file mode 100644
index 0000000000..6918ad9fec
--- /dev/null
+++ b/third_party/rust/bindgen/options/as_args.rs
@@ -0,0 +1,52 @@
+use std::path::PathBuf;
+
+use crate::RegexSet;
+
+/// Trait used to turn [`crate::BindgenOptions`] fields into CLI args.
+pub(super) trait AsArgs {
+    fn as_args(&self, args: &mut Vec<String>, flag: &str);
+}
+
+/// If the `bool` is `true`, `flag` is pushed into `args`.
+///
+/// be careful about the truth value of the field as some options, like `--no-layout-tests`, are
+/// actually negations of the fields.
+impl AsArgs for bool {
+    fn as_args(&self, args: &mut Vec<String>, flag: &str) {
+        if *self {
+            args.push(flag.to_string());
+        }
+    }
+}
+
+/// Iterate over all the items of the `RegexSet` and push `flag` followed by the item into `args`
+/// for each item.
+impl AsArgs for RegexSet {
+    fn as_args(&self, args: &mut Vec<String>, flag: &str) {
+        for item in self.get_items() {
+            args.extend_from_slice(&[flag.to_owned(), item.clone().into()]);
+        }
+    }
+}
+
+/// If the `Option` is `Some(value)`, push `flag` followed by `value`.
+impl AsArgs for Option<String> {
+    fn as_args(&self, args: &mut Vec<String>, flag: &str) {
+        if let Some(string) = self {
+            args.extend_from_slice(&[flag.to_owned(), string.clone()]);
+        }
+    }
+}
+
+/// If the `Option` is `Some(path)`, push `flag` followed by the [`std::path::Path::display`]
+/// representation of `path`.
+impl AsArgs for Option<PathBuf> {
+    fn as_args(&self, args: &mut Vec<String>, flag: &str) {
+        if let Some(path) = self {
+            args.extend_from_slice(&[
+                flag.to_owned(),
+                path.display().to_string(),
+            ]);
+        }
+    }
+}
diff --git a/third_party/rust/bindgen/options/helpers.rs b/third_party/rust/bindgen/options/helpers.rs
new file mode 100644
index 0000000000..1816c72b57
--- /dev/null
+++ b/third_party/rust/bindgen/options/helpers.rs
@@ -0,0 +1,43 @@
+/// Helper function that appends extra documentation to [`crate::Builder`] methods that support regular
+/// expressions in their input.
+macro_rules! regex_option {
+    ($(#[$attrs:meta])* pub fn $($tokens:tt)*) => {
+        $(#[$attrs])*
+        ///
+        /// Regular expressions are supported. Check the [regular expression
+        /// arguments](./struct.Builder.html#regular-expression-arguments) section and the
+        /// [regex](https://docs.rs/regex) crate documentation for further information.
+        pub fn $($tokens)*
+    };
+}
+
+/// Helper macro to set the default value of each option.
+///
+/// This macro is an internal implementation detail of the `options` macro and should not be used
+/// directly.
+macro_rules! default {
+    () => {
+        Default::default()
+    };
+    ($expr:expr) => {
+        $expr
+    };
+}
+
+/// Helper macro to set the conversion to CLI arguments for each option.
+///
+/// This macro is an internal implementation detail of the `options` macro and should not be used
+/// directly.
+macro_rules! as_args {
+    ($flag:literal) => {
+        |field, args| AsArgs::as_args(field, args, $flag)
+    };
+    ($expr:expr) => {
+        $expr
+    };
+}
+
+/// Helper function to ignore an option when converting it into CLI arguments.
+///
+/// This function is only used inside `options` and should not be used in other contexts.
+pub(super) fn ignore<T>(_: &T, _: &mut Vec<String>) {}
diff --git a/third_party/rust/bindgen/options/mod.rs b/third_party/rust/bindgen/options/mod.rs
new file mode 100644
index 0000000000..1fc2241615
--- /dev/null
+++ b/third_party/rust/bindgen/options/mod.rs
@@ -0,0 +1,2079 @@
+//! Declarations and setter methods for `bindgen` options.
+//!
+//! The main entry point of this module is the `options` macro.
+#[macro_use]
+mod helpers;
+mod as_args;
+
+use crate::callbacks::ParseCallbacks;
+use crate::codegen::{
+    AliasVariation, EnumVariation, MacroTypeVariation, NonCopyUnionStyle,
+};
+use crate::deps::DepfileSpec;
+use crate::features::{RustFeatures, RustTarget};
+use crate::regex_set::RegexSet;
+use crate::Abi;
+use crate::Builder;
+use crate::CodegenConfig;
+use crate::FieldVisibilityKind;
+use crate::Formatter;
+use crate::HashMap;
+use crate::DEFAULT_ANON_FIELDS_PREFIX;
+
+use std::env;
+#[cfg(feature = "experimental")]
+use std::path::Path;
+use std::path::PathBuf;
+use std::rc::Rc;
+
+use as_args::AsArgs;
+use helpers::ignore;
+
+/// Macro used to generate the [`BindgenOptions`] type and the [`Builder`] setter methods for each
+/// one of the fields of `BindgenOptions`.
+///
+/// The input format of this macro resembles a `struct` pattern. Each field of the `BindgenOptions`
+/// type is declared by adding the name of the field and its type using the `name: type` syntax and
+/// a block of code with the following items:
+///
+/// - `default`: The default value for the field. If this item is omitted, `Default::default()` is
+/// used instead, meaning that the type of the field must implement `Default`.
+/// - `methods`: A block of code containing methods for the `Builder` type. These methods should be
+/// related to the field being declared.
+/// - `as_args`: This item declares how the field should be converted into a valid CLI argument for
+/// `bindgen` and is used in the [`Builder::command_line_flags`] method which is used to do a
+/// roundtrip test of the CLI args in the `bindgen-test` crate. This item can take one of the
+/// following:
+///   - A string literal with the flag if the type of the field implements the [`AsArgs`] trait.
+///   - A closure with the signature `|field, args: &mut Vec<String>| -> ()` that pushes arguments
+///   into the `args` buffer based on the value of the field. This is used if the field does not
+///   implement `AsArgs` or if the implementation of the trait is not logically correct for the
+///   option and a custom behavior must be taken into account.
+///   - The `ignore` literal, which does not emit any CLI arguments for this field. This is useful
+///   if the field cannot be used from the `bindgen` CLI.
+///
+/// As an example, this would be the declaration of a `bool` field called `be_fun` whose default
+/// value is `false` (the `Default` value for `bool`):
+/// ```rust,ignore
+/// be_fun: bool {
+///    methods: {
+///        /// Ask `bindgen` to be fun. This option is disabled by default.
+///        fn be_fun(mut self) -> Self {
+///            self.options.be_fun = true;
+///            self
+///        }
+///    },
+///    as_args: "--be-fun",
+/// }
+/// ```
+///
+/// However, we could also set the `be_fun` field to `true` by default and use a `--not-fun` flag
+/// instead. This means that we have to add the `default` item and use a closure in the `as_args`
+/// item:
+/// ```rust,ignore
+/// be_fun: bool {
+///    default: true,
+///    methods: {
+///        /// Ask `bindgen` to not be fun. `bindgen` is fun by default.
+///        fn not_fun(mut self) -> Self {
+///            self.options.be_fun = false;
+///            self
+///        }
+///    },
+///    as_args: |be_fun, args| (!be_fun).as_args(args, "--not-fun"),
+/// }
+/// ```
+/// More complex examples can be found in the sole invocation of this macro.
+macro_rules! options {
+    ($(
+        $(#[doc = $docs:literal])+
+        $field:ident: $ty:ty {
+            $(default: $default:expr,)?
+            methods: {$($methods_tokens:tt)*}$(,)?
+            as_args: $as_args:expr$(,)?
+        }$(,)?
+    )*) => {
+        #[derive(Debug, Clone)]
+        pub(crate) struct BindgenOptions {
+            $($(#[doc = $docs])* pub(crate) $field: $ty,)*
+        }
+
+        impl Default for BindgenOptions {
+            fn default() -> Self {
+                Self {
+                    $($field: default!($($default)*),)*
+                }
+            }
+        }
+
+        impl Builder {
+            /// Generates the command line flags used to create this [`Builder`].
+            pub fn command_line_flags(&self) -> Vec<String> {
+                let mut args = vec![];
+
+                let headers = match self.options.input_headers.split_last() {
+                    Some((header, headers)) => {
+                        // The last input header is passed as an argument in the first position.
+                        args.push(header.clone().into());
+                        headers
+                    },
+                    None => &[]
+                };
+
+                $({
+                    let func: fn(&$ty, &mut Vec<String>) = as_args!($as_args);
+                    func(&self.options.$field, &mut args);
+                })*
+
+                // Add the `--experimental` flag if `bindgen` is built with the `experimental`
+                // feature.
+                if cfg!(feature = "experimental") {
+                    args.push("--experimental".to_owned());
+                }
+
+                // Add all the clang arguments.
+                args.push("--".to_owned());
+
+                if !self.options.clang_args.is_empty() {
+                    args.extend(self.options.clang_args.iter().map(|s| s.clone().into()));
+                }
+
+                // We need to pass all but the last header via the `-include` clang argument.
+                for header in headers {
+                    args.push("-include".to_owned());
+                    args.push(header.clone().into());
+                }
+
+                args
+            }
+
+            $($($methods_tokens)*)*
+        }
+    };
+}
+
+options! {
+    /// Types that have been blocklisted and should not appear anywhere in the generated code.
+    blocklisted_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not generate any bindings for the given type.
+                ///
+                /// This option is not recursive, meaning that it will only block types whose names
+                /// explicitly match the argument of this method.
+                pub fn blocklist_type<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.blocklisted_types.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--blocklist-type",
+    },
+    /// Functions that have been blocklisted and should not appear in the generated code.
+    blocklisted_functions: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not generate any bindings for the given function.
+                ///
+                /// This option is not recursive, meaning that it will only block functions whose
+                /// names explicitly match the argument of this method.
+                pub fn blocklist_function<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.blocklisted_functions.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--blocklist-function",
+    },
+    /// Items that have been blocklisted and should not appear in the generated code.
+    blocklisted_items: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not generate any bindings for the given item, regardless of whether it is a
+                /// type, function, module, etc.
+                ///
+                /// This option is not recursive, meaning that it will only block items whose names
+                /// explicitly match the argument of this method.
+                pub fn blocklist_item<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.blocklisted_items.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--blocklist-item",
+    },
+    /// Files whose contents should be blocklisted and should not appear in the generated code.
+    blocklisted_files: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not generate any bindings for the contents of the given file, regardless of
+                /// whether the contents of the file are types, functions, modules, etc.
+                ///
+                /// This option is not recursive, meaning that it will only block files whose names
+                /// explicitly match the argument of this method.
+                ///
+                /// This method will use the argument to match the complete path of the file
+                /// instead of a section of it.
+                pub fn blocklist_file<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.blocklisted_files.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--blocklist-file",
+    },
+    /// Variables that have been blocklisted and should not appear in the generated code.
+    blocklisted_vars: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not generate any bindings for the given variable.
+                ///
+                /// This option is not recursive, meaning that it will only block variables whose
+                /// names explicitly match the argument of this method.
+                pub fn blocklist_var<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.blocklisted_vars.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--blocklist-var",
+    },
+    /// Types that should be treated as opaque structures in the generated code.
+    opaque_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Treat the given type as opaque in the generated bindings.
+                ///
+                /// Opaque in this context means that none of the generated bindings will contain
+                /// information about the inner representation of the type and the type itself will
+                /// be represented as a chunk of bytes with the alignment and size of the type.
+                pub fn opaque_type<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.opaque_types.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--opaque-type",
+    },
+    /// The explicit `rustfmt` path.
+    rustfmt_path: Option<PathBuf> {
+        methods: {
+            /// Set an explicit path to the `rustfmt` binary.
+            ///
+            /// This option only comes into effect if `rustfmt` is set to be the formatter used by
+            /// `bindgen`. Check the documentation of the [`Builder::formatter`] method for more
+            /// information.
+            pub fn with_rustfmt<P: Into<PathBuf>>(mut self, path: P) -> Self {
+                self.options.rustfmt_path = Some(path.into());
+                self
+            }
+        },
+        // This option cannot be set from the CLI.
+        as_args: ignore,
+    },
+    /// The path to which we should write a Makefile-syntax depfile (if any).
+    depfile: Option<DepfileSpec> {
+        methods: {
+            /// Add a depfile output which will be written alongside the generated bindings.
+            pub fn depfile<H: Into<String>, D: Into<PathBuf>>(
+                mut self,
+                output_module: H,
+                depfile: D,
+            ) -> Builder {
+                self.options.depfile = Some(DepfileSpec {
+                    output_module: output_module.into(),
+                    depfile_path: depfile.into(),
+                });
+                self
+            }
+        },
+        as_args: |depfile, args| {
+            if let Some(depfile) = depfile {
+                args.push("--depfile".into());
+                args.push(depfile.depfile_path.display().to_string());
+            }
+        },
+    },
+    /// Types that have been allowlisted and should appear in the generated code.
+    allowlisted_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Generate bindings for the given type.
+                ///
+                /// This option is transitive by default. Check the documentation of the
+                /// [`Builder::allowlist_recursively`] method for further information.
+                pub fn allowlist_type<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.allowlisted_types.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--allowlist-type",
+    },
+    /// Functions that have been allowlisted and should appear in the generated code.
+    allowlisted_functions: RegexSet {
+        methods: {
+            regex_option! {
+                /// Generate bindings for the given function.
+                ///
+                /// This option is transitive by default. Check the documentation of the
+                /// [`Builder::allowlist_recursively`] method for further information.
+                pub fn allowlist_function<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.allowlisted_functions.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--allowlist-function",
+    },
+    /// Variables that have been allowlisted and should appear in the generated code.
+    allowlisted_vars: RegexSet {
+        methods: {
+            regex_option! {
+                /// Generate bindings for the given variable.
+                ///
+                /// This option is transitive by default. Check the documentation of the
+                /// [`Builder::allowlist_recursively`] method for further information.
+                pub fn allowlist_var<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.allowlisted_vars.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--allowlist-var",
+    },
+    /// Files whose contents have been allowlisted and should appear in the generated code.
+    allowlisted_files: RegexSet {
+        methods: {
+            regex_option! {
+                /// Generate bindings for the content of the given file.
+                ///
+                /// This option is transitive by default. Check the documentation of the
+                /// [`Builder::allowlist_recursively`] method for further information.
+                ///
+                /// This method will use the argument to match the complete path of the file
+                /// instead of a section of it.
+                pub fn allowlist_file<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.allowlisted_files.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--allowlist-file",
+    },
+    /// Items that have been allowlisted and should appear in the generated code.
+    allowlisted_items: RegexSet {
+        methods: {
+            regex_option! {
+                /// Generate bindings for the given item, regardless of whether it is a type,
+                /// function, module, etc.
+                ///
+                /// This option is transitive by default. Check the documentation of the
+                /// [`Builder::allowlist_recursively`] method for further information.
+                pub fn allowlist_item<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.allowlisted_items.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--allowlist-item",
+    },
+    /// The default style of for generated `enum`s.
+    default_enum_style: EnumVariation {
+        methods: {
+            /// Set the default style for generated `enum`s.
+            ///
+            /// If this method is not called, the [`EnumVariation::Consts`] style will be used by
+            /// default.
+            ///
+            /// To set the style for individual `enum`s, use [`Builder::bitfield_enum`],
+            /// [`Builder::newtype_enum`], [`Builder::newtype_global_enum`],
+            /// [`Builder::rustified_enum`], [`Builder::rustified_non_exhaustive_enum`],
+            /// [`Builder::constified_enum_module`] or [`Builder::constified_enum`].
+            pub fn default_enum_style(
+                mut self,
+                arg: EnumVariation,
+            ) -> Builder {
+                self.options.default_enum_style = arg;
+                self
+            }
+        },
+        as_args: |variation, args| {
+            if *variation != Default::default() {
+                args.push("--default-enum-style".to_owned());
+                args.push(variation.to_string());
+            }
+        },
+    },
+    /// `enum`s marked as bitfield-like. This is, newtypes with bitwise operations.
+    bitfield_enums: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `enum` as being bitfield-like.
+                ///
+                /// This is similar to the [`Builder::newtype_enum`] style, but with the bitwise
+                /// operators implemented.
+                pub fn bitfield_enum<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.bitfield_enums.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--bitfield-enum",
+    },
+    /// `enum`s marked as newtypes.
+    newtype_enums: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `enum` as a newtype.
+                ///
+                /// This means that an integer newtype will be declared to represent the `enum`
+                /// type and its variants will be represented as constants inside of this type's
+                /// `impl` block.
+                pub fn newtype_enum<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.newtype_enums.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--newtype-enum",
+    },
+    /// `enum`s marked as global newtypes .
+    newtype_global_enums: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `enum` as a global newtype.
+                ///
+                /// This is similar to the [`Builder::newtype_enum`] style, but the constants for
+                /// each variant are free constants instead of being declared inside an `impl`
+                /// block for the newtype.
+                pub fn newtype_global_enum<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.newtype_global_enums.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--newtype-global-enum",
+    },
+    /// `enum`s marked as Rust `enum`s.
+    rustified_enums: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `enum` as a Rust `enum`.
+                ///
+                /// This means that each variant of the `enum` will be represented as a Rust `enum`
+                /// variant.
+                ///
+                /// **Use this with caution**, creating an instance of a Rust `enum` with an
+                /// invalid value will cause undefined behaviour. To avoid this, use the
+                /// [`Builder::newtype_enum`] style instead.
+                pub fn rustified_enum<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.rustified_enums.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--rustified-enum",
+    },
+    /// `enum`s marked as non-exhaustive Rust `enum`s.
+    rustified_non_exhaustive_enums: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `enum` as a non-exhaustive Rust `enum`.
+                ///
+                /// This is similar to the [`Builder::rustified_enum`] style, but the `enum` is
+                /// tagged with the `#[non_exhaustive]` attribute.
+                pub fn rustified_non_exhaustive_enum<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.rustified_non_exhaustive_enums.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--rustified-non-exhaustive-enums",
+    },
+    /// `enum`s marked as modules of constants.
+    constified_enum_modules: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `enum` as a module with a set of integer constants.
+                pub fn constified_enum_module<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.constified_enum_modules.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--constified-enum-module",
+    },
+    /// `enum`s marked as a set of constants.
+    constified_enums: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `enum` as a set o integer constants.
+                ///
+                /// This is similar to the [`Builder::constified_enum_module`] style, but the
+                /// constants are generated in the current module instead of in a new module.
+                pub fn constified_enum<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.constified_enums.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--constified-enum",
+    },
+    /// The default type signedness for C macro constants.
+    default_macro_constant_type: MacroTypeVariation {
+        methods: {
+            /// Set the default type signedness to be used for macro constants.
+            ///
+            /// If this method is not called, [`MacroTypeVariation::Unsigned`] is used by default.
+            ///
+            /// To set the type for individual macro constants, use the
+            /// [`ParseCallbacks::int_macro`] method.
+            pub fn default_macro_constant_type(mut self, arg: MacroTypeVariation) -> Builder {
+                self.options.default_macro_constant_type = arg;
+                self
+            }
+
+        },
+        as_args: |variation, args| {
+            if *variation != Default::default() {
+                args.push("--default-macro-constant-type".to_owned());
+                args.push(variation.to_string());
+            }
+        },
+    },
+    /// The default style of code generation for `typedef`s.
+    default_alias_style: AliasVariation {
+        methods: {
+            /// Set the default style of code generation for `typedef`s.
+            ///
+            /// If this method is not called, the [`AliasVariation::TypeAlias`] style is used by
+            /// default.
+            ///
+            /// To set the style for individual `typedefs`s, use [`Builder::type_alias`],
+            /// [`Builder::new_type_alias`] or [`Builder::new_type_alias_deref`].
+            pub fn default_alias_style(
+                mut self,
+                arg: AliasVariation,
+            ) -> Builder {
+                self.options.default_alias_style = arg;
+                self
+            }
+        },
+        as_args: |variation, args| {
+            if *variation != Default::default() {
+                args.push("--default-alias-style".to_owned());
+                args.push(variation.to_string());
+            }
+        },
+    },
+    /// `typedef` patterns that will use regular type aliasing.
+    type_alias: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `typedef` as a regular Rust `type` alias.
+                ///
+                /// This is the default behavior, meaning that this method only comes into effect
+                /// if a style different from [`AliasVariation::TypeAlias`] was passed to the
+                /// [`Builder::default_alias_style`] method.
+                pub fn type_alias<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.type_alias.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--type-alias",
+    },
+    /// `typedef` patterns that will be aliased by creating a newtype.
+    new_type_alias: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `typedef` as a Rust newtype by having the aliased
+                /// type be wrapped in a `struct` with `#[repr(transparent)]`.
+                ///
+                /// This method can be used to enforce stricter type checking.
+                pub fn new_type_alias<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.new_type_alias.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--new-type-alias",
+    },
+    /// `typedef` patterns that will be wrapped in a newtype implementing `Deref` and `DerefMut`.
+    new_type_alias_deref: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `typedef` to be generated as a newtype that can be dereferenced.
+                ///
+                /// This is similar to the [`Builder::new_type_alias`] style, but the newtype
+                /// implements `Deref` and `DerefMut` with the aliased type as a target.
+                pub fn new_type_alias_deref<T: AsRef<str>>(mut self, arg: T) -> Builder {
+                    self.options.new_type_alias_deref.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--new-type-alias-deref",
+    },
+    /// The default style of code to generate for `union`s containing non-`Copy` members.
+    default_non_copy_union_style: NonCopyUnionStyle {
+        methods: {
+            /// Set the default style of code to generate for `union`s with non-`Copy` members.
+            ///
+            /// If this method is not called, the [`NonCopyUnionStyle::BindgenWrapper`] style is
+            /// used by default.
+            ///
+            /// To set the style for individual `union`s, use [`Builder::bindgen_wrapper_union`] or
+            /// [`Builder::manually_drop_union`].
+            pub fn default_non_copy_union_style(mut self, arg: NonCopyUnionStyle) -> Self {
+                self.options.default_non_copy_union_style = arg;
+                self
+            }
+        },
+        as_args: |style, args| {
+            if *style != Default::default() {
+                args.push("--default-non-copy-union-style".to_owned());
+                args.push(style.to_string());
+            }
+        },
+    },
+    /// The patterns marking non-`Copy` `union`s as using the `bindgen` generated wrapper.
+    bindgen_wrapper_union: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `union` to use a `bindgen`-generated wrapper for its members if at
+                /// least one them is not `Copy`.
+                ///
+                /// This is the default behavior, meaning that this method only comes into effect
+                /// if a style different from [`NonCopyUnionStyle::BindgenWrapper`] was passed to
+                /// the [`Builder::default_non_copy_union_style`] method.
+                pub fn bindgen_wrapper_union<T: AsRef<str>>(mut self, arg: T) -> Self {
+                    self.options.bindgen_wrapper_union.insert(arg);
+                    self
+                }
+            }
+        },
+        as_args: "--bindgen-wrapper-union",
+    },
+    /// The patterns marking non-`Copy` `union`s as using the `ManuallyDrop` wrapper.
+    manually_drop_union: RegexSet {
+        methods: {
+            regex_option! {
+                /// Mark the given `union` to use [`::core::mem::ManuallyDrop`] for its members if
+                /// at least one of them is not `Copy`.
+                ///
+                /// The `ManuallyDrop` type was stabilized in Rust 1.20.0, do not use this option
+                /// if your target version is lower than this.
+                pub fn manually_drop_union<T: AsRef<str>>(mut self, arg: T) -> Self {
+                    self.options.manually_drop_union.insert(arg);
+                    self
+                }
+            }
+
+        },
+        as_args: "--manually-drop-union",
+    },
+
+
+    /// Whether we should generate built-in definitions.
+    builtins: bool {
+        methods: {
+            /// Generate Rust bindings for built-in definitions (for example `__builtin_va_list`).
+            ///
+            /// Bindings for built-in definitions are not emitted by default.
+            pub fn emit_builtins(mut self) -> Builder {
+                self.options.builtins = true;
+                self
+            }
+        },
+        as_args: "--builtins",
+    },
+    /// Whether we should dump the Clang AST for debugging purposes.
+    emit_ast: bool {
+        methods: {
+            /// Emit the Clang AST to `stdout` for debugging purposes.
+            ///
+            /// The Clang AST is not emitted by default.
+            pub fn emit_clang_ast(mut self) -> Builder {
+                self.options.emit_ast = true;
+                self
+            }
+        },
+        as_args: "--emit-clang-ast",
+    },
+    /// Whether we should dump our IR for debugging purposes.
+    emit_ir: bool {
+        methods: {
+            /// Emit the `bindgen` internal representation to `stdout` for debugging purposes.
+            ///
+            /// This internal representation is not emitted by default.
+            pub fn emit_ir(mut self) -> Builder {
+                self.options.emit_ir = true;
+                self
+            }
+        },
+        as_args: "--emit-ir",
+    },
+    /// Output path for the `graphviz` DOT file.
+    emit_ir_graphviz: Option<String> {
+        methods: {
+            /// Set the path for the file where the`bindgen` internal representation will be
+            /// emitted as a graph using the `graphviz` DOT language.
+            ///
+            /// This graph representation is not emitted by default.
+            pub fn emit_ir_graphviz<T: Into<String>>(mut self, path: T) -> Builder {
+                let path = path.into();
+                self.options.emit_ir_graphviz = Some(path);
+                self
+            }
+        },
+        as_args: "--emit-ir-graphviz",
+    },
+
+    /// Whether we should emulate C++ namespaces with Rust modules.
+    enable_cxx_namespaces: bool {
+        methods: {
+            /// Emulate C++ namespaces using Rust modules in the generated bindings.
+            ///
+            /// C++ namespaces are not emulated by default.
+            pub fn enable_cxx_namespaces(mut self) -> Builder {
+                self.options.enable_cxx_namespaces = true;
+                self
+            }
+        },
+        as_args: "--enable-cxx-namespaces",
+    },
+    /// Whether we should try to find unexposed attributes in functions.
+    enable_function_attribute_detection: bool {
+        methods: {
+            /// Enable detecting function attributes on C functions.
+            ///
+            /// This enables the following features:
+            /// - Add `#[must_use]` attributes to Rust items whose C counterparts are marked as so.
+            /// This feature also requires that the Rust target version supports the attribute.
+            /// - Set `!` as the return type for Rust functions whose C counterparts are marked as
+            /// diverging.
+            ///
+            /// This option can be quite slow in some cases (check [#1465]), so it is disabled by
+            /// default.
+            ///
+            /// [#1465]: https://github.com/rust-lang/rust-bindgen/issues/1465
+            pub fn enable_function_attribute_detection(mut self) -> Self {
+                self.options.enable_function_attribute_detection = true;
+                self
+            }
+
+        },
+        as_args: "--enable-function-attribute-detection",
+    },
+    /// Whether we should avoid mangling names with namespaces.
+    disable_name_namespacing: bool {
+        methods: {
+            /// Disable name auto-namespacing.
+            ///
+            /// By default, `bindgen` mangles names like `foo::bar::Baz` to look like `foo_bar_Baz`
+            /// instead of just `Baz`. This method disables that behavior.
+            ///
+            /// Note that this does not change the names used for allowlisting and blocklisting,
+            /// which should still be mangled with the namespaces. Additionally, this option may
+            /// cause `bindgen` to generate duplicate names.
+            pub fn disable_name_namespacing(mut self) -> Builder {
+                self.options.disable_name_namespacing = true;
+                self
+            }
+        },
+        as_args: "--disable-name-namespacing",
+    },
+    /// Whether we should avoid generating nested `struct` names.
+    disable_nested_struct_naming: bool {
+        methods: {
+            /// Disable nested `struct` naming.
+            ///
+            /// The following `struct`s have different names for C and C++. In C, they are visible
+            /// as `foo` and `bar`. In C++, they are visible as `foo` and `foo::bar`.
+            ///
+            /// ```c
+            /// struct foo {
+            ///     struct bar {
+            ///     } b;
+            /// };
+            /// ```
+            ///
+            /// `bindgen` tries to avoid duplicate names by default, so it follows the C++ naming
+            /// convention and it generates `foo` and `foo_bar` instead of just `foo` and `bar`.
+            ///
+            /// This method disables this behavior and it is indented to be used only for headers
+            /// that were written in C.
+            pub fn disable_nested_struct_naming(mut self) -> Builder {
+                self.options.disable_nested_struct_naming = true;
+                self
+            }
+        },
+        as_args: "--disable-nested-struct-naming",
+    },
+    /// Whether we should avoid embedding version identifiers into source code.
+    disable_header_comment: bool {
+        methods: {
+            /// Do not insert the `bindgen` version identifier into the generated bindings.
+            ///
+            /// This identifier is inserted by default.
+            pub fn disable_header_comment(mut self) -> Self {
+                self.options.disable_header_comment = true;
+                self
+            }
+
+        },
+        as_args: "--disable-header-comment",
+    },
+    /// Whether we should generate layout tests for generated `struct`s.
+    layout_tests: bool {
+        default: true,
+        methods: {
+            /// Set whether layout tests should be generated.
+            ///
+            /// Layout tests are generated by default.
+            pub fn layout_tests(mut self, doit: bool) -> Self {
+                self.options.layout_tests = doit;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-layout-tests"),
+    },
+    /// Whether we should implement `Debug` for types that cannot derive it.
+    impl_debug: bool {
+        methods: {
+            /// Set whether `Debug` should be implemented for types that cannot derive it.
+            ///
+            /// This option is disabled by default.
+            pub fn impl_debug(mut self, doit: bool) -> Self {
+                self.options.impl_debug = doit;
+                self
+            }
+
+        },
+        as_args: "--impl-debug",
+    },
+    /// Whether we should implement `PartialEq` types that cannot derive it.
+    impl_partialeq: bool {
+        methods: {
+            /// Set whether `PartialEq` should be implemented for types that cannot derive it.
+            ///
+            /// This option is disabled by default.
+            pub fn impl_partialeq(mut self, doit: bool) -> Self {
+                self.options.impl_partialeq = doit;
+                self
+            }
+        },
+        as_args: "--impl-partialeq",
+    },
+    /// Whether we should derive `Copy` when possible.
+    derive_copy: bool {
+        default: true,
+        methods: {
+            /// Set whether the `Copy` trait should be derived when possible.
+            ///
+            /// `Copy` is derived by default.
+            pub fn derive_copy(mut self, doit: bool) -> Self {
+                self.options.derive_copy = doit;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-derive-copy"),
+    },
+
+    /// Whether we should derive `Debug` when possible.
+    derive_debug: bool {
+        default: true,
+        methods: {
+            /// Set whether the `Debug` trait should be derived when possible.
+            ///
+            /// The [`Builder::impl_debug`] method can be used to implement `Debug` for types that
+            /// cannot derive it.
+            ///
+            /// `Debug` is derived by default.
+            pub fn derive_debug(mut self, doit: bool) -> Self {
+                self.options.derive_debug = doit;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-derive-debug"),
+    },
+
+    /// Whether we should derive `Default` when possible.
+    derive_default: bool {
+        methods: {
+            /// Set whether the `Default` trait should be derived when possible.
+            ///
+            /// `Default` is not derived by default.
+            pub fn derive_default(mut self, doit: bool) -> Self {
+                self.options.derive_default = doit;
+                self
+            }
+        },
+        as_args: |&value, args| {
+            let arg = if value {
+                "--with-derive-default"
+            } else {
+                "--no-derive-default"
+            };
+
+            args.push(arg.to_owned());
+        },
+    },
+    /// Whether we should derive `Hash` when possible.
+    derive_hash: bool {
+        methods: {
+            /// Set whether the `Hash` trait should be derived when possible.
+            ///
+            /// `Hash` is not derived by default.
+            pub fn derive_hash(mut self, doit: bool) -> Self {
+                self.options.derive_hash = doit;
+                self
+            }
+        },
+        as_args: "--with-derive-hash",
+    },
+    /// Whether we should derive `PartialOrd` when possible.
+    derive_partialord: bool {
+        methods: {
+            /// Set whether the `PartialOrd` trait should be derived when possible.
+            ///
+            /// Take into account that `Ord` cannot be derived for a type that does not implement
+            /// `PartialOrd`. For this reason, setting this method to `false` also sets
+            /// automatically [`Builder::derive_ord`] to `false`.
+            ///
+            /// `PartialOrd` is not derived by default.
+            pub fn derive_partialord(mut self, doit: bool) -> Self {
+                self.options.derive_partialord = doit;
+                if !doit {
+                    self.options.derive_ord = false;
+                }
+                self
+            }
+        },
+        as_args: "--with-derive-partialord",
+    },
+    /// Whether we should derive `Ord` when possible.
+    derive_ord: bool {
+        methods: {
+            /// Set whether the `Ord` trait should be derived when possible.
+            ///
+            /// Take into account that `Ord` cannot be derived for a type that does not implement
+            /// `PartialOrd`. For this reason, the value set with this method will also be set
+            /// automatically for [`Builder::derive_partialord`].
+            ///
+            /// `Ord` is not derived by default.
+            pub fn derive_ord(mut self, doit: bool) -> Self {
+                self.options.derive_ord = doit;
+                self.options.derive_partialord = doit;
+                self
+            }
+        },
+        as_args: "--with-derive-ord",
+    },
+    /// Whether we should derive `PartialEq` when possible.
+    derive_partialeq: bool {
+        methods: {
+            /// Set whether the `PartialEq` trait should be derived when possible.
+            ///
+            /// Take into account that `Eq` cannot be derived for a type that does not implement
+            /// `PartialEq`. For this reason, setting this method to `false` also sets
+            /// automatically [`Builder::derive_eq`] to `false`.
+            ///
+            /// The [`Builder::impl_partialeq`] method can be used to implement `PartialEq` for
+            /// types that cannot derive it.
+            ///
+            /// `PartialEq` is not derived by default.
+            pub fn derive_partialeq(mut self, doit: bool) -> Self {
+                self.options.derive_partialeq = doit;
+                if !doit {
+                    self.options.derive_eq = false;
+                }
+                self
+            }
+        },
+        as_args: "--with-derive-partialeq",
+    },
+    /// Whether we should derive `Eq` when possible.
+    derive_eq: bool {
+        methods: {
+            /// Set whether the `Eq` trait should be derived when possible.
+            ///
+            /// Take into account that `Eq` cannot be derived for a type that does not implement
+            /// `PartialEq`. For this reason, the value set with this method will also be set
+            /// automatically for [`Builder::derive_partialeq`].
+            ///
+            /// `Eq` is not derived by default.
+            pub fn derive_eq(mut self, doit: bool) -> Self {
+                self.options.derive_eq = doit;
+                if doit {
+                    self.options.derive_partialeq = doit;
+                }
+                self
+            }
+        },
+        as_args: "--with-derive-eq",
+    },
+    /// Whether we should use `core` instead of `std`.
+    ///
+    /// If this option is enabled and the Rust target version is greater than 1.64, the prefix for
+    /// C platform-specific types will be `::core::ffi` instead of `::core::os::raw`.
+    use_core: bool {
+        methods: {
+            /// Use `core` instead of `std` in the generated bindings.
+            ///
+            /// `std` is used by default.
+            pub fn use_core(mut self) -> Builder {
+                self.options.use_core = true;
+                self
+            }
+
+        },
+        as_args: "--use-core",
+    },
+    /// An optional prefix for the C platform-specific types.
+    ctypes_prefix: Option<String> {
+        methods: {
+            /// Use the given prefix for the C platform-specific types instead of `::std::os::raw`.
+            ///
+            /// Alternatively, the [`Builder::use_core`] method can be used to set the prefix to
+            /// `::core::ffi` or `::core::os::raw`.
+            pub fn ctypes_prefix<T: Into<String>>(mut self, prefix: T) -> Builder {
+                self.options.ctypes_prefix = Some(prefix.into());
+                self
+            }
+        },
+        as_args: "--ctypes-prefix",
+    },
+    /// The prefix for anonymous fields.
+    anon_fields_prefix: String {
+        default: DEFAULT_ANON_FIELDS_PREFIX.into(),
+        methods: {
+            /// Use the given prefix for the anonymous fields.
+            ///
+            /// An anonymous field, is a field of a C/C++ type that does not have a name. For
+            /// example, in the following C code:
+            /// ```c
+            /// struct integer {
+            ///   struct {
+            ///     int inner;
+            ///   };
+            /// }
+            /// ```
+            ///
+            /// The only field of the `integer` `struct` is an anonymous field and its Rust
+            /// representation will be named using this prefix followed by an integer identifier.
+            ///
+            /// The default prefix is `__bindgen_anon_`.
+            pub fn anon_fields_prefix<T: Into<String>>(mut self, prefix: T) -> Builder {
+                self.options.anon_fields_prefix = prefix.into();
+                self
+            }
+        },
+        as_args: |prefix, args| {
+            if prefix != DEFAULT_ANON_FIELDS_PREFIX {
+                args.push("--anon-fields-prefix".to_owned());
+                args.push(prefix.clone());
+            }
+        },
+    },
+    /// Whether to measure the time for each one of the `bindgen` phases.
+    time_phases: bool {
+        methods: {
+            /// Set whether to measure the elapsed time for each one of the `bindgen` phases. This
+            /// information is printed to `stderr`.
+            ///
+            /// The elapsed time is not measured by default.
+            pub fn time_phases(mut self, doit: bool) -> Self {
+                self.options.time_phases = doit;
+                self
+            }
+        },
+        as_args: "--time-phases",
+    },
+    /// Whether to convert C float types to `f32` and `f64`.
+    convert_floats: bool {
+        default: true,
+        methods: {
+            /// Avoid converting C float types to `f32` and `f64`.
+            pub fn no_convert_floats(mut self) -> Self {
+                self.options.convert_floats = false;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-convert-floats"),
+    },
+    /// The set of raw lines to be prepended to the top-level module of the generated Rust code.
+    raw_lines: Vec<Box<str>> {
+        methods: {
+            /// Add a line of Rust code at the beginning of the generated bindings. The string is
+            /// passed through without any modification.
+            pub fn raw_line<T: Into<String>>(mut self, arg: T) -> Self {
+                self.options.raw_lines.push(arg.into().into_boxed_str());
+                self
+            }
+        },
+        as_args: |raw_lines, args| {
+            for line in raw_lines {
+                args.push("--raw-line".to_owned());
+                args.push(line.clone().into());
+            }
+        },
+    },
+    /// The set of raw lines to prepend to different modules.
+    module_lines: HashMap<Box<str>, Vec<Box<str>>> {
+        methods: {
+            /// Add a given line to the beginning of a given module.
+            ///
+            /// This option only comes into effect if the [`Builder::enable_cxx_namespaces`] method
+            /// is also being called.
+            pub fn module_raw_line<T, U>(mut self, module: T, line: U) -> Self
+            where
+                T: Into<String>,
+                U: Into<String>,
+            {
+                self.options
+                    .module_lines
+                    .entry(module.into().into_boxed_str())
+                    .or_default()
+                    .push(line.into().into_boxed_str());
+                self
+            }
+        },
+        as_args: |module_lines, args| {
+            for (module, lines) in module_lines {
+                for line in lines.iter() {
+                    args.push("--module-raw-line".to_owned());
+                    args.push(module.clone().into());
+                    args.push(line.clone().into());
+                }
+            }
+        },
+    },
+    /// The input header files.
+    input_headers:  Vec<Box<str>> {
+        methods: {
+            /// Add an input C/C++ header to generate bindings for.
+            ///
+            /// This can be used to generate bindings for a single header:
+            ///
+            /// ```ignore
+            /// let bindings = bindgen::Builder::default()
+            ///     .header("input.h")
+            ///     .generate()
+            ///     .unwrap();
+            /// ```
+            ///
+            /// Or for multiple headers:
+            ///
+            /// ```ignore
+            /// let bindings = bindgen::Builder::default()
+            ///     .header("first.h")
+            ///     .header("second.h")
+            ///     .header("third.h")
+            ///     .generate()
+            ///     .unwrap();
+            /// ```
+            pub fn header<T: Into<String>>(mut self, header: T) -> Builder {
+                self.options.input_headers.push(header.into().into_boxed_str());
+                self
+            }
+        },
+        // This field is handled specially inside the macro.
+        as_args: ignore,
+    },
+    /// The set of arguments to be passed straight through to Clang.
+    clang_args: Vec<Box<str>> {
+        methods: {
+            /// Add an argument to be passed straight through to Clang.
+            pub fn clang_arg<T: Into<String>>(self, arg: T) -> Builder {
+                self.clang_args([arg.into().into_boxed_str()])
+            }
+
+            /// Add several arguments to be passed straight through to Clang.
+            pub fn clang_args<I: IntoIterator>(mut self, args: I) -> Builder
+            where
+                I::Item: AsRef<str>,
+            {
+                for arg in args {
+                    self.options.clang_args.push(arg.as_ref().to_owned().into_boxed_str());
+                }
+                self
+            }
+        },
+        // This field is handled specially inside the macro.
+        as_args: ignore,
+    },
+    /// Tuples of unsaved file contents of the form (name, contents).
+    input_header_contents: Vec<(Box<str>, Box<str>)> {
+        methods: {
+            /// Add `contents` as an input C/C++ header named `name`.
+            ///
+            /// This can be used to inject additional C/C++ code as an input without having to
+            /// create additional header files.
+            pub fn header_contents(mut self, name: &str, contents: &str) -> Builder {
+                // Apparently clang relies on having virtual FS correspondent to
+                // the real one, so we need absolute paths here
+                let absolute_path = env::current_dir()
+                    .expect("Cannot retrieve current directory")
+                    .join(name)
+                    .to_str()
+                    .expect("Cannot convert current directory name to string")
+                    .into();
+                self.options
+                    .input_header_contents
+                    .push((absolute_path, contents.into()));
+                self
+            }
+        },
+        // Header contents cannot be added from the CLI.
+        as_args: ignore,
+    },
+    /// A user-provided visitor to allow customizing different kinds of situations.
+    parse_callbacks: Vec<Rc<dyn ParseCallbacks>> {
+        methods: {
+            /// Add a new [`ParseCallbacks`] instance to configure types in different situations.
+            pub fn parse_callbacks(mut self, cb: Box<dyn ParseCallbacks>) -> Self {
+                self.options.parse_callbacks.push(Rc::from(cb));
+                self
+            }
+        },
+        as_args: |_callbacks, _args| {
+            #[cfg(feature = "__cli")]
+            for cb in _callbacks {
+                _args.extend(cb.cli_args());
+            }
+        },
+    },
+    /// Which kind of items should we generate. We generate all of them by default.
+    codegen_config: CodegenConfig {
+        default: CodegenConfig::all(),
+        methods: {
+            /// Do not generate any functions.
+            ///
+            /// Functions are generated by default.
+            pub fn ignore_functions(mut self) -> Builder {
+                self.options.codegen_config.remove(CodegenConfig::FUNCTIONS);
+                self
+            }
+
+            /// Do not generate any methods.
+            ///
+            /// Methods are generated by default.
+            pub fn ignore_methods(mut self) -> Builder {
+                self.options.codegen_config.remove(CodegenConfig::METHODS);
+                self
+            }
+
+            /// Choose what to generate using a [`CodegenConfig`].
+            ///
+            /// This option overlaps with [`Builder::ignore_functions`] and
+            /// [`Builder::ignore_methods`].
+            ///
+            /// All the items in `CodegenConfig` are generated by default.
+            pub fn with_codegen_config(mut self, config: CodegenConfig) -> Self {
+                self.options.codegen_config = config;
+                self
+            }
+        },
+        as_args: |codegen_config, args| {
+            if !codegen_config.functions() {
+                args.push("--ignore-functions".to_owned());
+            }
+
+            args.push("--generate".to_owned());
+
+            //Temporary placeholder for the 4 options below.
+            let mut options: Vec<String> = Vec::new();
+            if codegen_config.functions() {
+                options.push("functions".to_owned());
+            }
+
+            if codegen_config.types() {
+                options.push("types".to_owned());
+            }
+
+            if codegen_config.vars() {
+                options.push("vars".to_owned());
+            }
+
+            if codegen_config.methods() {
+                options.push("methods".to_owned());
+            }
+
+            if codegen_config.constructors() {
+                options.push("constructors".to_owned());
+            }
+
+            if codegen_config.destructors() {
+                options.push("destructors".to_owned());
+            }
+
+            args.push(options.join(","));
+
+            if !codegen_config.methods() {
+                args.push("--ignore-methods".to_owned());
+            }
+        },
+    },
+    /// Whether to treat inline namespaces conservatively.
+    conservative_inline_namespaces: bool {
+        methods: {
+            /// Treat inline namespaces conservatively.
+            ///
+            /// This is tricky, because in C++ is technically legal to override an item
+            /// defined in an inline namespace:
+            ///
+            /// ```cpp
+            /// inline namespace foo {
+            ///     using Bar = int;
+            /// }
+            /// using Bar = long;
+            /// ```
+            ///
+            /// Even though referencing `Bar` is a compiler error.
+            ///
+            /// We want to support this (arguably esoteric) use case, but we do not want to make
+            /// the rest of `bindgen` users pay an usability penalty for that.
+            ///
+            /// To support this, we need to keep all the inline namespaces around, but then using
+            /// `bindgen` becomes a bit more difficult, because you cannot reference paths like
+            /// `std::string` (you'd need to use the proper inline namespace).
+            ///
+            /// We could complicate a lot of the logic to detect name collisions and, in the
+            /// absence of collisions, generate a `pub use inline_ns::*` or something like that.
+            ///
+            /// That is probably something we can do to improve the usability of this option if we
+            /// realize it is needed way more often. Our guess is that this extra logic is not
+            /// going to be very useful.
+            ///
+            /// This option is disabled by default.
+            pub fn conservative_inline_namespaces(mut self) -> Builder {
+                self.options.conservative_inline_namespaces = true;
+                self
+            }
+        },
+        as_args: "--conservative-inline-namespaces",
+    },
+    /// Whether to keep documentation comments in the generated output.
+    generate_comments: bool {
+        default: true,
+        methods: {
+            /// Set whether the generated bindings should contain documentation comments.
+            ///
+            /// Documentation comments are included by default.
+            ///
+            /// Note that clang excludes comments from system headers by default, pass
+            /// `"-fretain-comments-from-system-headers"` to the [`Builder::clang_arg`] method to
+            /// include them.
+            ///
+            /// It is also possible to process all comments and not just documentation using the
+            /// `"-fparse-all-comments"` flag. Check [these slides on clang comment parsing](
+            /// https://llvm.org/devmtg/2012-11/Gribenko_CommentParsing.pdf) for more information
+            /// and examples.
+            pub fn generate_comments(mut self, doit: bool) -> Self {
+                self.options.generate_comments = doit;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-doc-comments"),
+    },
+    /// Whether to generate inline functions.
+    generate_inline_functions: bool {
+        methods: {
+            /// Set whether to generate inline functions.
+            ///
+            /// This option is disabled by default.
+            ///
+            /// Note that they will usually not work. However you can use `-fkeep-inline-functions`
+            /// or `-fno-inline-functions` if you are responsible of compiling the library to make
+            /// them callable.
+            #[cfg_attr(
+                feature = "experimental",
+                doc = "\nCheck the [`Builder::wrap_static_fns`] method for an alternative."
+            )]
+            pub fn generate_inline_functions(mut self, doit: bool) -> Self {
+                self.options.generate_inline_functions = doit;
+                self
+            }
+        },
+        as_args: "--generate-inline-functions",
+    },
+    /// Whether to allowlist types recursively.
+    allowlist_recursively: bool {
+        default: true,
+        methods: {
+            /// Set whether to recursively allowlist items.
+            ///
+            /// Items are allowlisted recursively by default.
+            ///
+            /// Given that we have explicitly allowlisted the `initiate_dance_party` function in
+            /// this C header:
+            ///
+            /// ```c
+            /// typedef struct MoonBoots {
+            ///     int bouncy_level;
+            /// } MoonBoots;
+            ///
+            /// void initiate_dance_party(MoonBoots* boots);
+            /// ```
+            ///
+            /// We would normally generate bindings to both the `initiate_dance_party` function and
+            /// the `MoonBoots` type that it transitively references. If `false` is passed to this
+            /// method, `bindgen` will not emit bindings for anything except the explicitly
+            /// allowlisted items, meaning that the definition for `MoonBoots` would not be
+            /// generated. However, the `initiate_dance_party` function would still reference
+            /// `MoonBoots`!
+            ///
+            /// **Disabling this feature will almost certainly cause `bindgen` to emit bindings
+            /// that will not compile!** If you disable this feature, then it is *your*
+            /// responsibility to provide definitions for every type that is referenced from an
+            /// explicitly allowlisted item. One way to provide the missing definitions is by using
+            /// the [`Builder::raw_line`] method, another would be to define them in Rust and then
+            /// `include!(...)` the bindings immediately afterwards.
+            pub fn allowlist_recursively(mut self, doit: bool) -> Self {
+                self.options.allowlist_recursively = doit;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-recursive-allowlist"),
+    },
+    /// Whether to emit `#[macro_use] extern crate objc;` instead of `use objc;` in the prologue of
+    /// the files generated from objective-c files.
+    objc_extern_crate: bool {
+        methods: {
+            /// Emit `#[macro_use] extern crate objc;` instead of `use objc;` in the prologue of
+            /// the files generated from objective-c files.
+            ///
+            /// `use objc;` is emitted by default.
+            pub fn objc_extern_crate(mut self, doit: bool) -> Self {
+                self.options.objc_extern_crate = doit;
+                self
+            }
+        },
+        as_args: "--objc-extern-crate",
+    },
+    /// Whether to generate proper block signatures instead of `void` pointers.
+    generate_block: bool {
+        methods: {
+            /// Generate proper block signatures instead of `void` pointers.
+            ///
+            /// `void` pointers are used by default.
+            pub fn generate_block(mut self, doit: bool) -> Self {
+                self.options.generate_block = doit;
+                self
+            }
+        },
+        as_args: "--generate-block",
+    },
+    /// Whether to generate strings as `CStr`.
+    generate_cstr: bool {
+        methods: {
+            /// Set whether string constants should be generated as `&CStr` instead of `&[u8]`.
+            ///
+            /// A minimum Rust target of 1.59 is required for this to have any effect as support
+            /// for `CStr::from_bytes_with_nul_unchecked` in `const` contexts is needed.
+            ///
+            /// This option is disabled by default but will become enabled by default in a future
+            /// release, so enabling this is recommended.
+            pub fn generate_cstr(mut self, doit: bool) -> Self {
+                self.options.generate_cstr = doit;
+                self
+            }
+        },
+        as_args: "--generate-cstr",
+    },
+    /// Whether to emit `#[macro_use] extern crate block;` instead of `use block;` in the prologue
+    /// of the files generated from apple block files.
+    block_extern_crate: bool {
+        methods: {
+            /// Emit `#[macro_use] extern crate block;` instead of `use block;` in the prologue of
+            /// the files generated from apple block files.
+            ///
+            /// `use block;` is emitted by default.
+            pub fn block_extern_crate(mut self, doit: bool) -> Self {
+                self.options.block_extern_crate = doit;
+                self
+            }
+        },
+        as_args: "--block-extern-crate",
+    },
+    /// Whether to use the clang-provided name mangling.
+    enable_mangling: bool {
+        default: true,
+        methods: {
+            /// Set whether to use the clang-provided name mangling. This is probably needed for
+            /// C++ features.
+            ///
+            /// The mangling provided by clang is used by default.
+            ///
+            /// We allow disabling this option because some old `libclang` versions seem to return
+            /// incorrect results in some cases for non-mangled functions, check [#528] for more
+            /// information.
+            ///
+            /// [#528]: https://github.com/rust-lang/rust-bindgen/issues/528
+            pub fn trust_clang_mangling(mut self, doit: bool) -> Self {
+                self.options.enable_mangling = doit;
+                self
+            }
+
+        },
+        as_args: |value, args| (!value).as_args(args, "--distrust-clang-mangling"),
+    },
+    /// Whether to detect include paths using `clang_sys`.
+    detect_include_paths: bool {
+        default: true,
+        methods: {
+            /// Set whether to detect include paths using `clang_sys`.
+            ///
+            /// `clang_sys` is used to detect include paths by default.
+            pub fn detect_include_paths(mut self, doit: bool) -> Self {
+                self.options.detect_include_paths = doit;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-include-path-detection"),
+    },
+    /// Whether we should try to fit macro constants into types smaller than `u32` and `i32`.
+    fit_macro_constants: bool {
+        methods: {
+            /// Set whether `bindgen` should try to fit macro constants into types smaller than `u32`
+            /// and `i32`.
+            ///
+            /// This option is disabled by default.
+            pub fn fit_macro_constants(mut self, doit: bool) -> Self {
+                self.options.fit_macro_constants = doit;
+                self
+            }
+        },
+        as_args: "--fit-macro-constant-types",
+    },
+    /// Whether to prepend the `enum` name to constant or newtype variants.
+    prepend_enum_name: bool {
+        default: true,
+        methods: {
+            /// Set whether to prepend the `enum` name to constant or newtype variants.
+            ///
+            /// The `enum` name is prepended by default.
+            pub fn prepend_enum_name(mut self, doit: bool) -> Self {
+                self.options.prepend_enum_name = doit;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-prepend-enum-name"),
+    },
+    /// Version of the Rust compiler to target.
+    rust_target: RustTarget {
+        methods: {
+            /// Specify the Rust target version.
+            ///
+            /// The default target is the latest stable Rust version.
+            pub fn rust_target(mut self, rust_target: RustTarget) -> Self {
+                self.options.set_rust_target(rust_target);
+                self
+            }
+        },
+        as_args: |rust_target, args| {
+            args.push("--rust-target".to_owned());
+            args.push(rust_target.to_string());
+        },
+    },
+    /// Features to be enabled. They are derived from `rust_target`.
+    rust_features: RustFeatures {
+        default: RustTarget::default().into(),
+        methods: {},
+        // This field cannot be set from the CLI,
+        as_args: ignore,
+    },
+    /// Enable support for native Rust unions if they are supported.
+    untagged_union: bool {
+        default: true,
+        methods: {
+            /// Disable support for native Rust unions, if supported.
+            ///
+            /// The default value of this option is set based on the value passed to
+            /// [`Builder::rust_target`].
+            pub fn disable_untagged_union(mut self) -> Self {
+                self.options.untagged_union = false;
+                self
+            }
+        }
+        as_args: |value, args| (!value).as_args(args, "--disable-untagged-union"),
+    },
+    /// Whether we should record which items in the regex sets did match any C items.
+    record_matches: bool {
+        default: true,
+        methods: {
+            /// Set whether we should record which items in our regex sets did match any C items.
+            ///
+            /// Matches are recorded by default.
+            pub fn record_matches(mut self, doit: bool) -> Self {
+                self.options.record_matches = doit;
+                self
+            }
+
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-record-matches"),
+    },
+    /// Whether `size_t` should be translated to `usize` automatically.
+    size_t_is_usize: bool {
+        default: true,
+        methods: {
+            /// Set whether `size_t` should be translated to `usize`.
+            ///
+            /// If `size_t` is translated to `usize`, type definitions for `size_t` will not be
+            /// emitted.
+            ///
+            /// `size_t` is translated to `usize` by default.
+            pub fn size_t_is_usize(mut self, is: bool) -> Self {
+                self.options.size_t_is_usize = is;
+                self
+            }
+        },
+        as_args: |value, args| (!value).as_args(args, "--no-size_t-is-usize"),
+    },
+    /// The tool that should be used to format the generated bindings.
+    formatter: Formatter {
+        methods: {
+            /// Set whether `rustfmt` should be used to format the generated bindings.
+            ///
+            /// `rustfmt` is used by default.
+            ///
+            /// This method overlaps in functionality with the more general [`Builder::formatter`].
+            /// Thus, the latter should be preferred.
+            #[deprecated]
+            pub fn rustfmt_bindings(mut self, doit: bool) -> Self {
+                self.options.formatter = if doit {
+                    Formatter::Rustfmt
+                } else {
+                    Formatter::None
+                };
+                self
+            }
+
+            /// Set which tool should be used to format the generated bindings.
+            ///
+            /// The default formatter is [`Formatter::Rustfmt`].
+            ///
+            /// To be able to use `prettyplease` as a formatter, the `"prettyplease"` feature for
+            /// `bindgen` must be enabled in the Cargo manifest.
+            pub fn formatter(mut self, formatter: Formatter) -> Self {
+                self.options.formatter = formatter;
+                self
+            }
+        },
+        as_args: |formatter, args| {
+            if *formatter != Default::default() {
+                args.push("--formatter".to_owned());
+                args.push(formatter.to_string());
+            }
+        },
+    },
+    /// The absolute path to the `rustfmt` configuration file.
+    rustfmt_configuration_file: Option<PathBuf> {
+        methods: {
+            /// Set the absolute path to the `rustfmt` configuration file.
+            ///
+            /// The default `rustfmt` options are used if `None` is passed to this method or if
+            /// this method is not called at all.
+            ///
+            /// Calling this method will set the [`Builder::rustfmt_bindings`] option to `true`
+            /// and the [`Builder::formatter`] option to [`Formatter::Rustfmt`].
+            pub fn rustfmt_configuration_file(mut self, path: Option<PathBuf>) -> Self {
+                self = self.formatter(Formatter::Rustfmt);
+                self.options.rustfmt_configuration_file = path;
+                self
+            }
+        },
+        as_args: "--rustfmt-configuration-file",
+    },
+    /// Types that should not derive `PartialEq`.
+    no_partialeq_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not derive `PartialEq` for a given type.
+                pub fn no_partialeq<T: Into<String>>(mut self, arg: T) -> Builder {
+                    self.options.no_partialeq_types.insert(arg.into());
+                    self
+                }
+            }
+        },
+        as_args: "--no-partialeq",
+    },
+    /// Types that should not derive `Copy`.
+    no_copy_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not derive `Copy` and `Clone` for a given type.
+                pub fn no_copy<T: Into<String>>(mut self, arg: T) -> Self {
+                    self.options.no_copy_types.insert(arg.into());
+                    self
+                }
+            }
+        },
+        as_args: "--no-copy",
+    },
+    /// Types that should not derive `Debug`.
+    no_debug_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not derive `Debug` for a given type.
+                pub fn no_debug<T: Into<String>>(mut self, arg: T) -> Self {
+                    self.options.no_debug_types.insert(arg.into());
+                    self
+                }
+            }
+        },
+        as_args: "--no-debug",
+    },
+    /// Types that should not derive or implement `Default`.
+    no_default_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not derive or implement `Default` for a given type.
+                pub fn no_default<T: Into<String>>(mut self, arg: T) -> Self {
+                    self.options.no_default_types.insert(arg.into());
+                    self
+                }
+            }
+        },
+        as_args: "--no-default",
+    },
+    /// Types that should not derive `Hash`.
+    no_hash_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Do not derive `Hash` for a given type.
+                pub fn no_hash<T: Into<String>>(mut self, arg: T) -> Builder {
+                    self.options.no_hash_types.insert(arg.into());
+                    self
+                }
+            }
+        },
+        as_args: "--no-hash",
+    },
+    /// Types that should be annotated with `#[must_use]`.
+    must_use_types: RegexSet {
+        methods: {
+            regex_option! {
+                /// Annotate the given type with the `#[must_use]` attribute.
+                pub fn must_use_type<T: Into<String>>(mut self, arg: T) -> Builder {
+                    self.options.must_use_types.insert(arg.into());
+                    self
+                }
+            }
+        },
+        as_args: "--must-use-type",
+    },
+    /// Whether C arrays should be regular pointers in rust or array pointers
+    array_pointers_in_arguments: bool {
+        methods: {
+            /// Translate arrays `T arr[size]` into array pointers `*mut [T; size]` instead of
+            /// translating them as `*mut T` which is the default.
+            ///
+            /// The same is done for `*const` pointers.
+            pub fn array_pointers_in_arguments(mut self, doit: bool) -> Self {
+                self.options.array_pointers_in_arguments = doit;
+                self
+            }
+
+        },
+        as_args: "--use-array-pointers-in-arguments",
+    },
+    /// The name of the `wasm_import_module`.
+    wasm_import_module_name: Option<String> {
+        methods: {
+            /// Adds the `#[link(wasm_import_module = import_name)]` attribute to all the `extern`
+            /// blocks generated by `bindgen`.
+            ///
+            /// This attribute is not added by default.
+            pub fn wasm_import_module_name<T: Into<String>>(
+                mut self,
+                import_name: T,
+            ) -> Self {
+                self.options.wasm_import_module_name = Some(import_name.into());
+                self
+            }
+        },
+        as_args: "--wasm-import-module-name",
+    },
+    /// The name of the dynamic library (if we are generating bindings for a shared library).
+    dynamic_library_name: Option<String> {
+        methods: {
+            /// Generate bindings for a shared library with the given name.
+            ///
+            /// This option is disabled by default.
+            pub fn dynamic_library_name<T: Into<String>>(
+                mut self,
+                dynamic_library_name: T,
+            ) -> Self {
+                self.options.dynamic_library_name = Some(dynamic_library_name.into());
+                self
+            }
+        },
+        as_args: "--dynamic-loading",
+    },
+    /// Whether to equire successful linkage for all routines in a shared library.
+    dynamic_link_require_all: bool {
+        methods: {
+            /// Set whether to require successful linkage for all routines in a shared library.
+            /// This allows us to optimize function calls by being able to safely assume function
+            /// pointers are valid.
+            ///
+            /// This option only comes into effect if the [`Builder::dynamic_library_name`] option
+            /// is set.
+            ///
+            /// This option is disabled by default.
+            pub fn dynamic_link_require_all(mut self, req: bool) -> Self {
+                self.options.dynamic_link_require_all = req;
+                self
+            }
+        },
+        as_args: "--dynamic-link-require-all",
+    },
+    /// Whether to only make generated bindings `pub` if the items would be publicly accessible by
+    /// C++.
+    respect_cxx_access_specs: bool {
+        methods: {
+            /// Set whether to respect the C++ access specifications.
+            ///
+            /// Passing `true` to this method will set the visibility of the generated Rust items
+            /// as `pub` only if the corresponding C++ items are publicly accessible instead of
+            /// marking all the items as public, which is the default.
+            pub fn respect_cxx_access_specs(mut self, doit: bool) -> Self {
+                self.options.respect_cxx_access_specs = doit;
+                self
+            }
+
+        },
+        as_args: "--respect-cxx-access-specs",
+    },
+    /// Whether to translate `enum` integer types to native Rust integer types.
+    translate_enum_integer_types: bool {
+        methods: {
+            /// Set whether to always translate `enum` integer types to native Rust integer types.
+            ///
+            /// Passing `true` to this method will result in `enum`s having types such as `u32` and
+            /// `i16` instead of `c_uint` and `c_short` which is the default. The `#[repr]` types
+            /// of Rust `enum`s are always translated to Rust integer types.
+            pub fn translate_enum_integer_types(mut self, doit: bool) -> Self {
+                self.options.translate_enum_integer_types = doit;
+                self
+            }
+        },
+        as_args: "--translate-enum-integer-types",
+    },
+    /// Whether to generate types with C style naming.
+    c_naming: bool {
+        methods: {
+            /// Set whether to generate types with C style naming.
+            ///
+            /// Passing `true` to this method will add prefixes to the generated type names. For
+            /// example, instead of a `struct` with name `A` we will generate a `struct` with
+            /// `struct_A`. Currently applies to `struct`s, `union`s, and `enum`s.
+            pub fn c_naming(mut self, doit: bool) -> Self {
+                self.options.c_naming = doit;
+                self
+            }
+        },
+        as_args: "--c-naming",
+    },
+    /// Wether to always emit explicit padding fields.
+    force_explicit_padding: bool {
+        methods: {
+            /// Set whether to always emit explicit padding fields.
+            ///
+            /// This option should be enabled if a `struct` needs to be serialized in its native
+            /// format (padding bytes and all). This could be required if such `struct` will be
+            /// written to a file or sent over the network, as anything reading the padding bytes
+            /// of a struct may cause undefined behavior.
+            ///
+            /// Padding fields are not emitted by default.
+            pub fn explicit_padding(mut self, doit: bool) -> Self {
+                self.options.force_explicit_padding = doit;
+                self
+            }
+        },
+        as_args: "--explicit-padding",
+    },
+    /// Whether to emit vtable functions.
+    vtable_generation: bool {
+        methods: {
+            /// Set whether to enable experimental support to generate virtual table functions.
+            ///
+            /// This option should mostly work, though some edge cases are likely to be broken.
+            ///
+            /// Virtual table generation is disabled by default.
+            pub fn vtable_generation(mut self, doit: bool) -> Self {
+                self.options.vtable_generation = doit;
+                self
+            }
+        },
+        as_args: "--vtable-generation",
+    },
+    /// Whether to sort the generated Rust items.
+    sort_semantically: bool {
+        methods: {
+            /// Set whether to sort the generated Rust items in a predefined manner.
+            ///
+            /// Items are not ordered by default.
+            pub fn sort_semantically(mut self, doit: bool) -> Self {
+                self.options.sort_semantically = doit;
+                self
+            }
+        },
+        as_args: "--sort-semantically",
+    },
+    /// Whether to deduplicate `extern` blocks.
+    merge_extern_blocks: bool {
+        methods: {
+            /// Merge all extern blocks under the same module into a single one.
+            ///
+            /// Extern blocks are not merged by default.
+            pub fn merge_extern_blocks(mut self, doit: bool) -> Self {
+                self.options.merge_extern_blocks = doit;
+                self
+            }
+        },
+        as_args: "--merge-extern-blocks",
+    },
+    /// Whether to wrap unsafe operations in unsafe blocks.
+    wrap_unsafe_ops: bool {
+        methods: {
+            /// Wrap all unsafe operations in unsafe blocks.
+            ///
+            /// Unsafe operations are not wrapped by default.
+            pub fn wrap_unsafe_ops(mut self, doit: bool) -> Self {
+                self.options.wrap_unsafe_ops = doit;
+                self
+            }
+        },
+        as_args: "--wrap-unsafe-ops",
+    },
+    /// Patterns for functions whose ABI should be overriden.
+    abi_overrides: HashMap<Abi, RegexSet> {
+        methods: {
+            regex_option! {
+                /// Override the ABI of a given function.
+                pub fn override_abi<T: Into<String>>(mut self, abi: Abi, arg: T) -> Self {
+                    self.options
+                        .abi_overrides
+                        .entry(abi)
+                        .or_default()
+                        .insert(arg.into());
+                    self
+                }
+            }
+        },
+        as_args: |overrides, args| {
+            for (abi, set) in overrides {
+                for item in set.get_items() {
+                    args.push("--override-abi".to_owned());
+                    args.push(format!("{}={}", item, abi));
+                }
+            }
+        },
+    },
+    /// Whether to generate wrappers for `static` functions.
+    wrap_static_fns: bool {
+        methods: {
+            #[cfg(feature = "experimental")]
+            /// Set whether to generate wrappers for `static`` functions.
+            ///
+            /// Passing `true` to this method will generate a C source file with non-`static`
+            /// functions that call the `static` functions found in the input headers and can be
+            /// called from Rust once the source file is compiled.
+            ///
+            /// The path of this source file can be set using the [`Builder::wrap_static_fns_path`]
+            /// method.
+            pub fn wrap_static_fns(mut self, doit: bool) -> Self {
+                self.options.wrap_static_fns = doit;
+                self
+            }
+        },
+        as_args: "--wrap-static-fns",
+    },
+    /// The suffix to be added to the function wrappers for `static` functions.
+    wrap_static_fns_suffix: Option<String> {
+        methods: {
+            #[cfg(feature = "experimental")]
+            /// Set the suffix added to the wrappers for `static` functions.
+            ///
+            /// This option only comes into effect if `true` is passed to the
+            /// [`Builder::wrap_static_fns`] method.
+            ///
+            /// The default suffix is `__extern`.
+            pub fn wrap_static_fns_suffix<T: AsRef<str>>(mut self, suffix: T) -> Self {
+                self.options.wrap_static_fns_suffix = Some(suffix.as_ref().to_owned());
+                self
+            }
+        },
+        as_args: "--wrap-static-fns-suffix",
+    },
+    /// The path of the file where the wrappers for `static` functions will be emitted.
+    wrap_static_fns_path: Option<PathBuf> {
+        methods: {
+            #[cfg(feature = "experimental")]
+            /// Set the path for the source code file that would be created if any wrapper
+            /// functions must be generated due to the presence of `static` functions.
+            ///
+            /// `bindgen` will automatically add the right extension to the header and source code
+            /// files.
+            ///
+            /// This option only comes into effect if `true` is passed to the
+            /// [`Builder::wrap_static_fns`] method.
+            ///
+            /// The default path is `temp_dir/bindgen/extern`, where `temp_dir` is the path
+            /// returned by [`std::env::temp_dir`] .
+            pub fn wrap_static_fns_path<T: AsRef<Path>>(mut self, path: T) -> Self {
+                self.options.wrap_static_fns_path = Some(path.as_ref().to_owned());
+                self
+            }
+        },
+        as_args: "--wrap-static-fns-path",
+    },
+    /// Default visibility of fields.
+    default_visibility: FieldVisibilityKind {
+        methods: {
+            /// Set the default visibility of fields, including bitfields and accessor methods for
+            /// bitfields.
+            ///
+            /// This option only comes into effect if the [`Builder::respect_cxx_access_specs`]
+            /// option is disabled.
+            pub fn default_visibility(
+                mut self,
+                visibility: FieldVisibilityKind,
+            ) -> Self {
+                self.options.default_visibility = visibility;
+                self
+            }
+        },
+        as_args: |visibility, args| {
+            if *visibility != Default::default() {
+                args.push("--default-visibility".to_owned());
+                args.push(visibility.to_string());
+            }
+        },
+    },
+    /// Whether to emit diagnostics or not.
+    emit_diagnostics: bool {
+        methods: {
+            #[cfg(feature = "experimental")]
+            /// Emit diagnostics.
+            ///
+            /// These diagnostics are emitted to `stderr` if you are using `bindgen-cli` or printed
+            /// using `cargo:warning=` if you are using `bindgen` as a `build-dependency`.
+            ///
+            /// Diagnostics are not emitted by default.
+            ///
+            /// The layout and contents of these diagnostic messages are not covered by versioning
+            /// and can change without notice.
+            pub fn emit_diagnostics(mut self) -> Self {
+                self.options.emit_diagnostics = true;
+                self
+            }
+        },
+        as_args: "--emit-diagnostics",
+    }
+}
diff --git a/third_party/rust/bindgen/parse.rs b/third_party/rust/bindgen/parse.rs
new file mode 100644
index 0000000000..d29b090fcb
--- /dev/null
+++ b/third_party/rust/bindgen/parse.rs
@@ -0,0 +1,41 @@
+//! Common traits and types related to parsing our IR from Clang cursors.
+#![deny(clippy::missing_docs_in_private_items)]
+
+use crate::clang;
+use crate::ir::context::{BindgenContext, ItemId};
+
+/// Not so much an error in the traditional sense, but a control flow message
+/// when walking over Clang's AST with a cursor.
+#[derive(Debug)]
+pub(crate) enum ParseError {
+    /// Recurse down the current AST node's children.
+    Recurse,
+    /// Continue on to the next sibling AST node, or back up to the parent's
+    /// siblings if we've exhausted all of this node's siblings (and so on).
+    Continue,
+}
+
+/// The result of parsing a Clang AST node.
+#[derive(Debug)]
+pub(crate) enum ParseResult<T> {
+    /// We've already resolved this item before, here is the extant `ItemId` for
+    /// it.
+    AlreadyResolved(ItemId),
+
+    /// This is a newly parsed item. If the cursor is `Some`, it points to the
+    /// AST node where the new `T` was declared.
+    New(T, Option<clang::Cursor>),
+}
+
+/// An intermediate representation "sub-item" (i.e. one of the types contained
+/// inside an `ItemKind` variant) that can be parsed from a Clang cursor.
+pub(crate) trait ClangSubItemParser: Sized {
+    /// Attempt to parse this type from the given cursor.
+    ///
+    /// The fact that is a reference guarantees it's held by the context, and
+    /// allow returning already existing types.
+    fn parse(
+        cursor: clang::Cursor,
+        context: &mut BindgenContext,
+    ) -> Result<ParseResult<Self>, ParseError>;
+}
diff --git a/third_party/rust/bindgen/regex_set.rs b/third_party/rust/bindgen/regex_set.rs
new file mode 100644
index 0000000000..b78424aae1
--- /dev/null
+++ b/third_party/rust/bindgen/regex_set.rs
@@ -0,0 +1,204 @@
+//! A type that represents the union of a set of regular expressions.
+#![deny(clippy::missing_docs_in_private_items)]
+
+use regex::RegexSet as RxSet;
+use std::cell::Cell;
+
+/// A dynamic set of regular expressions.
+#[derive(Clone, Debug, Default)]
+pub struct RegexSet {
+    items: Vec<Box<str>>,
+    /// Whether any of the items in the set was ever matched. The length of this
+    /// vector is exactly the length of `items`.
+    matched: Vec<Cell<bool>>,
+    set: Option<RxSet>,
+    /// Whether we should record matching items in the `matched` vector or not.
+    record_matches: bool,
+}
+
+impl RegexSet {
+    /// Create a new RegexSet
+    pub fn new() -> RegexSet {
+        RegexSet::default()
+    }
+
+    /// Is this set empty?
+    pub fn is_empty(&self) -> bool {
+        self.items.is_empty()
+    }
+
+    /// Insert a new regex into this set.
+    pub fn insert<S>(&mut self, string: S)
+    where
+        S: AsRef<str>,
+    {
+        self.items.push(string.as_ref().to_owned().into_boxed_str());
+        self.matched.push(Cell::new(false));
+        self.set = None;
+    }
+
+    /// Returns slice of String from its field 'items'
+    pub fn get_items(&self) -> &[Box<str>] {
+        &self.items
+    }
+
+    /// Returns an iterator over regexes in the set which didn't match any
+    /// strings yet.
+    pub fn unmatched_items(&self) -> impl Iterator<Item = &str> {
+        self.items.iter().enumerate().filter_map(move |(i, item)| {
+            if !self.record_matches || self.matched[i].get() {
+                return None;
+            }
+
+            Some(item.as_ref())
+        })
+    }
+
+    /// Construct a RegexSet from the set of entries we've accumulated.
+    ///
+    /// Must be called before calling `matches()`, or it will always return
+    /// false.
+    #[inline]
+    pub fn build(&mut self, record_matches: bool) {
+        self.build_inner(record_matches, None)
+    }
+
+    #[cfg(all(feature = "__cli", feature = "experimental"))]
+    /// Construct a RegexSet from the set of entries we've accumulated and emit diagnostics if the
+    /// name of the regex set is passed to it.
+    ///
+    /// Must be called before calling `matches()`, or it will always return
+    /// false.
+    #[inline]
+    pub fn build_with_diagnostics(
+        &mut self,
+        record_matches: bool,
+        name: Option<&'static str>,
+    ) {
+        self.build_inner(record_matches, name)
+    }
+
+    #[cfg(all(not(feature = "__cli"), feature = "experimental"))]
+    /// Construct a RegexSet from the set of entries we've accumulated and emit diagnostics if the
+    /// name of the regex set is passed to it.
+    ///
+    /// Must be called before calling `matches()`, or it will always return
+    /// false.
+    #[inline]
+    pub(crate) fn build_with_diagnostics(
+        &mut self,
+        record_matches: bool,
+        name: Option<&'static str>,
+    ) {
+        self.build_inner(record_matches, name)
+    }
+
+    fn build_inner(
+        &mut self,
+        record_matches: bool,
+        _name: Option<&'static str>,
+    ) {
+        let items = self.items.iter().map(|item| format!("^({})$", item));
+        self.record_matches = record_matches;
+        self.set = match RxSet::new(items) {
+            Ok(x) => Some(x),
+            Err(e) => {
+                warn!("Invalid regex in {:?}: {:?}", self.items, e);
+                #[cfg(feature = "experimental")]
+                if let Some(name) = _name {
+                    invalid_regex_warning(self, e, name);
+                }
+                None
+            }
+        }
+    }
+
+    /// Does the given `string` match any of the regexes in this set?
+    pub fn matches<S>(&self, string: S) -> bool
+    where
+        S: AsRef<str>,
+    {
+        let s = string.as_ref();
+        let set = match self.set {
+            Some(ref set) => set,
+            None => return false,
+        };
+
+        if !self.record_matches {
+            return set.is_match(s);
+        }
+
+        let matches = set.matches(s);
+        if !matches.matched_any() {
+            return false;
+        }
+        for i in matches.iter() {
+            self.matched[i].set(true);
+        }
+
+        true
+    }
+}
+
+#[cfg(feature = "experimental")]
+fn invalid_regex_warning(
+    set: &RegexSet,
+    err: regex::Error,
+    name: &'static str,
+) {
+    use crate::diagnostics::{Diagnostic, Level, Slice};
+
+    let mut diagnostic = Diagnostic::default();
+
+    match err {
+        regex::Error::Syntax(string) => {
+            if string.starts_with("regex parse error:\n") {
+                let mut source = String::new();
+
+                let mut parsing_source = true;
+
+                for line in string.lines().skip(1) {
+                    if parsing_source {
+                        if line.starts_with(' ') {
+                            source.push_str(line);
+                            source.push('\n');
+                            continue;
+                        }
+                        parsing_source = false;
+                    }
+                    let error = "error: ";
+                    if line.starts_with(error) {
+                        let (_, msg) = line.split_at(error.len());
+                        diagnostic.add_annotation(msg.to_owned(), Level::Error);
+                    } else {
+                        diagnostic.add_annotation(line.to_owned(), Level::Info);
+                    }
+                }
+                let mut slice = Slice::default();
+                slice.with_source(source);
+                diagnostic.add_slice(slice);
+
+                diagnostic.with_title(
+                    "Error while parsing a regular expression.",
+                    Level::Warn,
+                );
+            } else {
+                diagnostic.with_title(string, Level::Warn);
+            }
+        }
+        err => {
+            let err = err.to_string();
+            diagnostic.with_title(err, Level::Warn);
+        }
+    }
+
+    diagnostic.add_annotation(
+        format!("This regular expression was passed via `{}`.", name),
+        Level::Note,
+    );
+
+    if set.items.iter().any(|item| item.as_ref() == "*") {
+        diagnostic.add_annotation("Wildcard patterns \"*\" are no longer considered valid. Use \".*\" instead.", Level::Help);
+    }
+    diagnostic.display();
+}
diff --git a/third_party/rust/bindgen/time.rs b/third_party/rust/bindgen/time.rs
new file mode 100644
index 0000000000..c13a640c46
--- /dev/null
+++ b/third_party/rust/bindgen/time.rs
@@ -0,0 +1,52 @@
+use std::io::{self, Write};
+use std::time::{Duration, Instant};
+
+/// RAII timer to measure how long phases take.
+#[derive(Debug)]
+pub struct Timer<'a> {
+    output: bool,
+    name: &'a str,
+    start: Instant,
+}
+
+impl<'a> Timer<'a> {
+    /// Creates a Timer with the given name, and starts it. By default,
+    /// will print to stderr when it is `drop`'d
+    pub fn new(name: &'a str) -> Self {
+        Timer {
+            output: true,
+            name,
+            start: Instant::now(),
+        }
+    }
+
+    /// Sets whether or not the Timer will print a message
+    /// when it is dropped.
+    pub fn with_output(mut self, output: bool) -> Self {
+        self.output = output;
+        self
+    }
+
+    /// Returns the time elapsed since the timer's creation
+    pub fn elapsed(&self) -> Duration {
+        Instant::now() - self.start
+    }
+
+    fn print_elapsed(&mut self) {
+        if self.output {
+            let elapsed = self.elapsed();
+            let time = (elapsed.as_secs() as f64) * 1e3 +
+                (elapsed.subsec_nanos() as f64) / 1e6;
+            let stderr = io::stderr();
+            // Arbitrary output format, subject to change.
+            writeln!(stderr.lock(), "  time: {:>9.3} ms.\t{}", time, self.name)
+                .expect("timer write should not fail");
+        }
+    }
+}
+
+impl<'a> Drop for Timer<'a> {
+    fn drop(&mut self) {
+        self.print_elapsed();
+    }
+}