Adding upstream version 110.0.1.upstream/110.0.1upstream

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

189 files changed, 16972 insertions, 0 deletions

diff --git a/third_party/rust/uniffi_bindgen/.cargo-checksum.json b/third_party/rust/uniffi_bindgen/.cargo-checksum.json
new file mode 100644
index 0000000000..4b63276ba4
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/.cargo-checksum.json
@@ -0,0 +1 @@
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\ No newline at end of file
diff --git a/third_party/rust/uniffi_bindgen/Cargo.lock b/third_party/rust/uniffi_bindgen/Cargo.lock
new file mode 100644
index 0000000000..0c06566ebc
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/Cargo.lock
@@ -0,0 +1,517 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
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+
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+dependencies = [
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+ "askama_escape",
+ "askama_shared",
+]
+
+[[package]]
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+ "askama_shared",
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+ "syn",
+]
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diff --git a/third_party/rust/uniffi_bindgen/Cargo.toml b/third_party/rust/uniffi_bindgen/Cargo.toml
new file mode 100644
index 0000000000..ac9ed39dc1
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/Cargo.toml
@@ -0,0 +1,81 @@
+# 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 = "2021"
+name = "uniffi_bindgen"
+version = "0.21.1"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+description = "a multi-language bindings generator for rust (codegen and cli tooling)"
+homepage = "https://mozilla.github.io/uniffi-rs"
+documentation = "https://mozilla.github.io/uniffi-rs"
+keywords = [
+    "ffi",
+    "bindgen",
+]
+license = "MPL-2.0"
+repository = "https://github.com/mozilla/uniffi-rs"
+
+[[bin]]
+name = "uniffi-bindgen"
+path = "src/main.rs"
+
+[dependencies.anyhow]
+version = "1"
+
+[dependencies.askama]
+version = "0.11"
+features = ["config"]
+default-features = false
+
+[dependencies.bincode]
+version = "1.3"
+
+[dependencies.camino]
+version = "1.0.8"
+
+[dependencies.clap]
+version = "3.1"
+features = [
+    "cargo",
+    "std",
+    "derive",
+]
+
+[dependencies.fs-err]
+version = "2.7.0"
+
+[dependencies.goblin]
+version = "0.6"
+
+[dependencies.heck]
+version = "0.4"
+
+[dependencies.once_cell]
+version = "1.12"
+
+[dependencies.paste]
+version = "1.0"
+
+[dependencies.serde]
+version = "1"
+
+[dependencies.serde_json]
+version = "1.0.80"
+
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+version = "=0.21.1"
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diff --git a/third_party/rust/uniffi_bindgen/askama.toml b/third_party/rust/uniffi_bindgen/askama.toml
new file mode 100644
index 0000000000..a0aae5f41b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/askama.toml
@@ -0,0 +1,21 @@
+[general]
+# Directories to search for templates, relative to the crate root.
+dirs = [ "src/scaffolding/templates", "src/bindings/kotlin/templates", "src/bindings/python/templates", "src/bindings/swift/templates", "src/bindings/ruby/templates" ]
+
+[[syntax]]
+name = "kt"
+
+[[syntax]]
+name = "py"
+
+[[syntax]]
+name = "swift"
+
+[[syntax]]
+name = "c"
+
+[[syntax]]
+name = "rs"
+
+[[syntax]]
+name = "rb"
diff --git a/third_party/rust/uniffi_bindgen/src/backend/config.rs b/third_party/rust/uniffi_bindgen/src/backend/config.rs
new file mode 100644
index 0000000000..616cde0656
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/backend/config.rs
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use serde::{Deserialize, Serialize};
+
+/// Config value for template expressions
+///
+/// These are strings that support simple template substitution.  `{}` gets replaced by a value.
+#[derive(Debug, Default, Clone, Serialize, Deserialize)]
+pub struct TemplateExpression(String);
+
+impl TemplateExpression {
+    pub fn render(&self, var: &str) -> String {
+        self.0.replace("{}", var)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/backend/declarations.rs b/third_party/rust/uniffi_bindgen/src/backend/declarations.rs
new file mode 100644
index 0000000000..320cfe995c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/backend/declarations.rs
@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use super::CodeOracle;
+
+/// A trait that is able to render a declaration about a particular member declared in
+/// the `ComponentInterface`.
+/// Like `CodeType`, it can render declaration code and imports. It also is able to render
+/// code at start-up of the FFI.
+/// All methods are optional, and there is no requirement that the trait be used for a particular
+/// `interface::` member. Thus, it can also be useful for conditionally rendering code.
+pub trait CodeDeclaration {
+    /// A list of imports that are needed if this type is in use.
+    /// Classes are imported exactly once.
+    fn imports(&self, _oracle: &dyn CodeOracle) -> Option<Vec<String>> {
+        None
+    }
+
+    /// Code (one or more statements) that is run on start-up of the library,
+    /// but before the client code has access to it.
+    fn initialization_code(&self, _oracle: &dyn CodeOracle) -> Option<String> {
+        None
+    }
+
+    /// Code which represents this member. e.g. the foreign language class definition for
+    /// a given Object type.
+    fn definition_code(&self, _oracle: &dyn CodeOracle) -> Option<String> {
+        None
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/backend/mod.rs b/third_party/rust/uniffi_bindgen/src/backend/mod.rs
new file mode 100644
index 0000000000..ed4c032508
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/backend/mod.rs
@@ -0,0 +1,16 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+mod config;
+mod declarations;
+mod oracle;
+mod types;
+
+pub use config::TemplateExpression;
+pub use declarations::CodeDeclaration;
+pub use oracle::CodeOracle;
+pub use types::CodeType;
+
+pub type TypeIdentifier = crate::interface::Type;
+pub type Literal = crate::interface::Literal;
diff --git a/third_party/rust/uniffi_bindgen/src/backend/oracle.rs b/third_party/rust/uniffi_bindgen/src/backend/oracle.rs
new file mode 100644
index 0000000000..9819046584
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/backend/oracle.rs
@@ -0,0 +1,35 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use super::{CodeType, TypeIdentifier};
+use crate::interface::FFIType;
+
+/// An object to look up a foreign language code specific renderer for a given type used.
+/// Every `Type` referred to in the `ComponentInterface` should map to a corresponding
+/// `CodeType`.
+///
+/// The mapping may be opaque, but the oracle always knows the answer.
+///
+/// In adddition, the oracle knows how to render identifiers (function names,
+/// class names, variable names etc).
+pub trait CodeOracle {
+    fn find(&self, type_: &TypeIdentifier) -> Box<dyn CodeType>;
+
+    /// Get the idiomatic rendering of a class name (for enums, records, errors, etc).
+    fn class_name(&self, nm: &str) -> String;
+
+    /// Get the idiomatic rendering of a function name.
+    fn fn_name(&self, nm: &str) -> String;
+
+    /// Get the idiomatic rendering of a variable name.
+    fn var_name(&self, nm: &str) -> String;
+
+    /// Get the idiomatic rendering of an individual enum variant.
+    fn enum_variant_name(&self, nm: &str) -> String;
+
+    /// Get the idiomatic rendering of an error name.
+    fn error_name(&self, nm: &str) -> String;
+
+    fn ffi_type_label(&self, ffi_type: &FFIType) -> String;
+}
diff --git a/third_party/rust/uniffi_bindgen/src/backend/types.rs b/third_party/rust/uniffi_bindgen/src/backend/types.rs
new file mode 100644
index 0000000000..aaf5cdaf36
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/backend/types.rs
@@ -0,0 +1,239 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Backend traits
+//!
+//! This module provides a number of traits useful for implementing a backend for Uniffi.
+//!
+//! A `CodeType` is needed for each type that will cross the FFI. It should provide helper machinery
+//! in the target language to lift from and lower into a value of that type into a primitive type
+//! (the FFIType), and foreign language expressions that call into the machinery. This helper code
+//! can be provided by a template file.
+//!
+//! A `CodeDeclaration` is needed for each type that is declared in the UDL file. This has access to
+//! the [crate::interface::ComponentInterface], which is the closest thing to an Intermediate Representation.
+//!
+//! `CodeDeclaration`s provide the target language's version of the UDL type, including forwarding method calls
+//! into Rust. It is likely if you're implementing a `CodeDeclaration` for this purpose, it will also need to cross
+//! the FFI, and you'll also need a `CodeType`.
+//!
+//! `CodeDeclaration`s can also be used to conditionally include code: e.g. only include the CallbackInterfaceRuntime
+//! if the user has used at least one callback interface.
+//!
+//! Each backend has a wrapper template for each file it needs to generate. This should collect the `CodeDeclaration`s that
+//! the backend and `ComponentInterface` between them specify and use them to stitch together a file in the target language.
+//!
+//! The `CodeOracle` provides methods to map the `Type` values found in the `ComponentInterface` to the `CodeType`s specified
+//! by the backend. It also provides methods for transforming identifiers into the coding standard for the target language.
+//!
+//! Each backend will have its own `filter` module, which is used by the askama templates used in all `CodeType`s and `CodeDeclaration`s.
+//! This filter provides methods to generate expressions and identifiers in the target language. These are all forwarded to the oracle.
+
+use super::{CodeOracle, Literal};
+use crate::interface::*;
+
+/// A Trait to emit foreign language code to handle referenced types.
+/// A type which is specified in the UDL (i.e. a member of the component interface)
+/// will have a `CodeDeclaration` as well, but for types used e.g. primitive types, Strings, etc
+/// only a `CodeType` is needed.
+pub trait CodeType {
+    /// The language specific label used to reference this type. This will be used in
+    /// method signatures and property declarations.
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String;
+
+    /// A representation of this type label that can be used as part of another
+    /// identifier. e.g. `read_foo()`, or `FooInternals`.
+    ///
+    /// This is especially useful when creating specialized objects or methods to deal
+    /// with this type only.
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        self.type_label(oracle)
+    }
+
+    /// A representation of the given literal for this type.
+    /// N.B. `Literal` is aliased from `interface::Literal`, so may not be whole suited to this task.
+    fn literal(&self, oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unimplemented!("Unimplemented for {}", self.type_label(oracle))
+    }
+
+    /// Name of the FfiConverter
+    ///
+    /// This is the object that contains the lower, write, lift, and read methods for this type.
+    /// Depending on the binding this will either be a singleton or a class with static methods.
+    ///
+    /// This is the newer way of handling these methods and replaces the lower, write, lift, and
+    /// read CodeType methods.  Currently only used by Kotlin, but the plan is to move other
+    /// backends to using this.
+    fn ffi_converter_name(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&format!("FfiConverter{}", self.canonical_name(oracle)))
+    }
+
+    /// An expression for lowering a value into something we can pass over the FFI.
+    ///
+    /// N.B. This should align with the `helper_code` generated by this `CodeType`.
+    fn lower(&self, oracle: &dyn CodeOracle, _nm: &str) -> String {
+        unimplemented!("Unimplemented for {}", self.type_label(oracle))
+    }
+
+    /// An expression for writing a value into a byte buffer.
+    ///
+    /// N.B. This should align with the `helper_code` generated by this `CodeType`.
+    fn write(&self, oracle: &dyn CodeOracle, _nm: &str, _target: &str) -> String {
+        unimplemented!("Unimplemented for {}", self.type_label(oracle))
+    }
+
+    /// An expression for lifting a value from something we received over the FFI.
+    ///
+    /// N.B. This should align with the `helper_code` generated by this `CodeType`.
+    fn lift(&self, oracle: &dyn CodeOracle, _nm: &str) -> String {
+        unimplemented!("Unimplemented for {}", self.type_label(oracle))
+    }
+
+    /// An expression for reading a value from a byte buffer.
+    ///
+    /// N.B. This should align with the `helper_code` generated by this `CodeType`.
+    fn read(&self, oracle: &dyn CodeOracle, _nm: &str) -> String {
+        unimplemented!("Unimplemented for {}", self.type_label(oracle))
+    }
+
+    /// The lift/lower/read/write methods above must be producing expressions that
+    /// can be part of a larger statement. Most of the time, that is a function call
+    /// to do the work for it.
+    /// The functions being called by those experessions should be declared in the
+    /// helper code generated by this method.
+    fn helper_code(&self, _oracle: &dyn CodeOracle) -> Option<String> {
+        None
+    }
+
+    /// A list of imports that are needed if this type is in use.
+    /// Classes are imported exactly once.
+    fn imports(&self, _oracle: &dyn CodeOracle) -> Option<Vec<String>> {
+        None
+    }
+
+    /// Function to run at startup
+    fn initialization_fn(&self, _oracle: &dyn CodeOracle) -> Option<String> {
+        None
+    }
+
+    /// An expression to coerce the given variable to the expected type.
+    fn coerce(&self, oracle: &dyn CodeOracle, _nm: &str) -> String {
+        panic!("Unimplemented for {}", self.type_label(oracle));
+    }
+}
+
+/// This trait is used to implement `CodeType` for `Type` and type-like structs (`Record`, `Enum`, `Field`,
+/// etc).  We forward all method calls to a `Box<dyn CodeType>`, which we get by calling
+/// `CodeOracle.find()`.
+pub trait CodeTypeDispatch {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType>;
+}
+
+impl CodeTypeDispatch for Type {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(self)
+    }
+}
+
+impl CodeTypeDispatch for Record {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(&self.type_())
+    }
+}
+
+impl CodeTypeDispatch for Enum {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(&self.type_())
+    }
+}
+
+impl CodeTypeDispatch for Error {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(&self.type_())
+    }
+}
+
+impl CodeTypeDispatch for Object {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(&self.type_())
+    }
+}
+
+impl CodeTypeDispatch for CallbackInterface {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(&self.type_())
+    }
+}
+
+impl CodeTypeDispatch for Field {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(self.type_())
+    }
+}
+
+impl CodeTypeDispatch for Argument {
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        oracle.find(self.type_())
+    }
+}
+
+// Needed to handle &&Type and &&&Type values, which we sometimes end up with in the template code
+impl<T, C> CodeTypeDispatch for T
+where
+    T: std::ops::Deref<Target = C>,
+    C: CodeTypeDispatch,
+{
+    fn code_type_impl(&self, oracle: &dyn CodeOracle) -> Box<dyn CodeType> {
+        self.deref().code_type_impl(oracle)
+    }
+}
+
+impl<T: CodeTypeDispatch> CodeType for T {
+    // The above code implements `CodeTypeDispatch` for `Type` and type-like structs (`Record`,
+    // `Enum`, `Field`, etc).  Now we can leverage that to implement `CodeType` for all of them.
+    // This allows for simpler template code (`field|lower` instead of `field.type_()|lower`)
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        self.code_type_impl(oracle).type_label(oracle)
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        self.code_type_impl(oracle).canonical_name(oracle)
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        self.code_type_impl(oracle).literal(oracle, literal)
+    }
+
+    fn lower(&self, oracle: &dyn CodeOracle, nm: &str) -> String {
+        self.code_type_impl(oracle).lower(oracle, nm)
+    }
+
+    fn write(&self, oracle: &dyn CodeOracle, nm: &str, target: &str) -> String {
+        self.code_type_impl(oracle).write(oracle, nm, target)
+    }
+
+    fn lift(&self, oracle: &dyn CodeOracle, nm: &str) -> String {
+        self.code_type_impl(oracle).lift(oracle, nm)
+    }
+
+    fn read(&self, oracle: &dyn CodeOracle, nm: &str) -> String {
+        self.code_type_impl(oracle).read(oracle, nm)
+    }
+
+    fn helper_code(&self, oracle: &dyn CodeOracle) -> Option<String> {
+        self.code_type_impl(oracle).helper_code(oracle)
+    }
+
+    fn imports(&self, oracle: &dyn CodeOracle) -> Option<Vec<String>> {
+        self.code_type_impl(oracle).imports(oracle)
+    }
+
+    fn initialization_fn(&self, oracle: &dyn CodeOracle) -> Option<String> {
+        self.code_type_impl(oracle).initialization_fn(oracle)
+    }
+
+    fn coerce(&self, oracle: &dyn CodeOracle, nm: &str) -> String {
+        self.code_type_impl(oracle).coerce(oracle, nm)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/callback_interface.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/callback_interface.rs
new file mode 100644
index 0000000000..c0c7ab29b9
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/callback_interface.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct CallbackInterfaceCodeType {
+    id: String,
+}
+
+impl CallbackInterfaceCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for CallbackInterfaceCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+
+    fn initialization_fn(&self, oracle: &dyn CodeOracle) -> Option<String> {
+        Some(format!("{}.register", self.ffi_converter_name(oracle)))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/compounds.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/compounds.rs
new file mode 100644
index 0000000000..7d5f77141f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/compounds.rs
@@ -0,0 +1,94 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal, TypeIdentifier};
+use paste::paste;
+
+fn render_literal(oracle: &dyn CodeOracle, literal: &Literal, inner: &TypeIdentifier) -> String {
+    match literal {
+        Literal::Null => "null".into(),
+        Literal::EmptySequence => "listOf()".into(),
+        Literal::EmptyMap => "mapOf()".into(),
+
+        // For optionals
+        _ => oracle.find(inner).literal(oracle, literal),
+    }
+}
+
+macro_rules! impl_code_type_for_compound {
+     ($T:ty, $type_label_pattern:literal, $canonical_name_pattern: literal) => {
+        paste! {
+            pub struct $T {
+                inner: TypeIdentifier,
+            }
+
+            impl $T {
+                pub fn new(inner: TypeIdentifier) -> Self {
+                    Self { inner }
+                }
+                fn inner(&self) -> &TypeIdentifier {
+                    &self.inner
+                }
+            }
+
+            impl CodeType for $T  {
+                fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+                    format!($type_label_pattern, oracle.find(self.inner()).type_label(oracle))
+                }
+
+                fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+                    format!($canonical_name_pattern, oracle.find(self.inner()).canonical_name(oracle))
+                }
+
+                fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+                    render_literal(oracle, literal, self.inner())
+                }
+            }
+        }
+    }
+ }
+
+impl_code_type_for_compound!(OptionalCodeType, "{}?", "Optional{}");
+impl_code_type_for_compound!(SequenceCodeType, "List<{}>", "Sequence{}");
+
+pub struct MapCodeType {
+    key: TypeIdentifier,
+    value: TypeIdentifier,
+}
+
+impl MapCodeType {
+    pub fn new(key: TypeIdentifier, value: TypeIdentifier) -> Self {
+        Self { key, value }
+    }
+
+    fn key(&self) -> &TypeIdentifier {
+        &self.key
+    }
+
+    fn value(&self) -> &TypeIdentifier {
+        &self.value
+    }
+}
+
+impl CodeType for MapCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Map<{}, {}>",
+            self.key().type_label(oracle),
+            self.value().type_label(oracle),
+        )
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Map{}{}",
+            self.key().type_label(oracle),
+            self.value().type_label(oracle),
+        )
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        render_literal(oracle, literal, &self.value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/custom.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/custom.rs
new file mode 100644
index 0000000000..4a5636a228
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/custom.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct CustomCodeType {
+    name: String,
+}
+
+impl CustomCodeType {
+    pub fn new(name: String) -> Self {
+        CustomCodeType { name }
+    }
+}
+
+impl CodeType for CustomCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        self.name.clone()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.name)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!("Can't have a literal of a custom type");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/enum_.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/enum_.rs
new file mode 100644
index 0000000000..941008e370
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/enum_.rs
@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct EnumCodeType {
+    id: String,
+}
+
+impl EnumCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for EnumCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        if let Literal::Enum(v, _) = literal {
+            format!(
+                "{}.{}",
+                self.type_label(oracle),
+                oracle.enum_variant_name(v)
+            )
+        } else {
+            unreachable!();
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/error.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/error.rs
new file mode 100644
index 0000000000..3ab5f0ac9f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/error.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ErrorCodeType {
+    id: String,
+}
+
+impl ErrorCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ErrorCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.error_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/external.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/external.rs
new file mode 100644
index 0000000000..32d47cb3f1
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/external.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ExternalCodeType {
+    name: String,
+}
+
+impl ExternalCodeType {
+    pub fn new(name: String) -> Self {
+        Self { name }
+    }
+}
+
+impl CodeType for ExternalCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        self.name.clone()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.name)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!("Can't have a literal of an external type");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/miscellany.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/miscellany.rs
new file mode 100644
index 0000000000..57b9a145e7
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/miscellany.rs
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+use paste::paste;
+
+macro_rules! impl_code_type_for_miscellany {
+    ($T:ty, $class_name:literal, $canonical_name:literal) => {
+        paste! {
+            pub struct $T;
+
+            impl CodeType for $T  {
+                fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+                    $class_name.into()
+                }
+
+                fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+                   $canonical_name.into()
+               }
+
+                fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+                    unreachable!()
+                }
+            }
+        }
+    };
+}
+
+impl_code_type_for_miscellany!(TimestampCodeType, "java.time.Instant", "Timestamp");
+
+impl_code_type_for_miscellany!(DurationCodeType, "java.time.Duration", "Duration");
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/mod.rs
new file mode 100644
index 0000000000..b5907898d4
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/mod.rs
@@ -0,0 +1,380 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::borrow::Borrow;
+use std::cell::RefCell;
+use std::collections::{BTreeSet, HashMap, HashSet};
+
+use anyhow::{Context, Result};
+use askama::Template;
+use heck::{ToLowerCamelCase, ToShoutySnakeCase, ToUpperCamelCase};
+use serde::{Deserialize, Serialize};
+
+use crate::backend::{CodeOracle, CodeType, TemplateExpression, TypeIdentifier};
+use crate::interface::*;
+use crate::MergeWith;
+
+mod callback_interface;
+mod compounds;
+mod custom;
+mod enum_;
+mod error;
+mod external;
+mod miscellany;
+mod object;
+mod primitives;
+mod record;
+
+// config options to customize the generated Kotlin.
+#[derive(Debug, Default, Clone, Serialize, Deserialize)]
+pub struct Config {
+    package_name: Option<String>,
+    cdylib_name: Option<String>,
+    #[serde(default)]
+    custom_types: HashMap<String, CustomTypeConfig>,
+    #[serde(default)]
+    external_packages: HashMap<String, String>,
+}
+
+#[derive(Debug, Default, Clone, Serialize, Deserialize)]
+pub struct CustomTypeConfig {
+    imports: Option<Vec<String>>,
+    type_name: Option<String>,
+    into_custom: TemplateExpression,
+    from_custom: TemplateExpression,
+}
+
+impl Config {
+    pub fn package_name(&self) -> String {
+        if let Some(package_name) = &self.package_name {
+            package_name.clone()
+        } else {
+            "uniffi".into()
+        }
+    }
+
+    pub fn cdylib_name(&self) -> String {
+        if let Some(cdylib_name) = &self.cdylib_name {
+            cdylib_name.clone()
+        } else {
+            "uniffi".into()
+        }
+    }
+}
+
+impl From<&ComponentInterface> for Config {
+    fn from(ci: &ComponentInterface) -> Self {
+        Config {
+            package_name: Some(format!("uniffi.{}", ci.namespace())),
+            cdylib_name: Some(format!("uniffi_{}", ci.namespace())),
+            custom_types: HashMap::new(),
+            external_packages: HashMap::new(),
+        }
+    }
+}
+
+impl MergeWith for Config {
+    fn merge_with(&self, other: &Self) -> Self {
+        Config {
+            package_name: self.package_name.merge_with(&other.package_name),
+            cdylib_name: self.cdylib_name.merge_with(&other.cdylib_name),
+            custom_types: self.custom_types.merge_with(&other.custom_types),
+            external_packages: self.external_packages.merge_with(&other.external_packages),
+        }
+    }
+}
+
+// Generate kotlin bindings for the given ComponentInterface, as a string.
+pub fn generate_bindings(config: &Config, ci: &ComponentInterface) -> Result<String> {
+    KotlinWrapper::new(config.clone(), ci)
+        .render()
+        .context("failed to render kotlin bindings")
+}
+
+/// Renders Kotlin helper code for all types
+///
+/// This template is a bit different than others in that it stores internal state from the render
+/// process.  Make sure to only call `render()` once.
+#[derive(Template)]
+#[template(syntax = "kt", escape = "none", path = "Types.kt")]
+pub struct TypeRenderer<'a> {
+    kotlin_config: &'a Config,
+    ci: &'a ComponentInterface,
+    // Track included modules for the `include_once()` macro
+    include_once_names: RefCell<HashSet<String>>,
+    // Track imports added with the `add_import()` macro
+    imports: RefCell<BTreeSet<String>>,
+}
+
+impl<'a> TypeRenderer<'a> {
+    fn new(kotlin_config: &'a Config, ci: &'a ComponentInterface) -> Self {
+        Self {
+            kotlin_config,
+            ci,
+            include_once_names: RefCell::new(HashSet::new()),
+            imports: RefCell::new(BTreeSet::new()),
+        }
+    }
+
+    // Get the package name for an external type
+    fn external_type_package_name(&self, crate_name: &str) -> String {
+        match self.kotlin_config.external_packages.get(crate_name) {
+            Some(name) => name.clone(),
+            None => crate_name.to_string(),
+        }
+    }
+
+    // The following methods are used by the `Types.kt` macros.
+
+    // Helper for the including a template, but only once.
+    //
+    // The first time this is called with a name it will return true, indicating that we should
+    // include the template.  Subsequent calls will return false.
+    fn include_once_check(&self, name: &str) -> bool {
+        self.include_once_names
+            .borrow_mut()
+            .insert(name.to_string())
+    }
+
+    // Helper to add an import statement
+    //
+    // Call this inside your template to cause an import statement to be added at the top of the
+    // file.  Imports will be sorted and de-deuped.
+    //
+    // Returns an empty string so that it can be used inside an askama `{{ }}` block.
+    fn add_import(&self, name: &str) -> &str {
+        self.imports.borrow_mut().insert(name.to_owned());
+        ""
+    }
+}
+
+#[derive(Template)]
+#[template(syntax = "kt", escape = "none", path = "wrapper.kt")]
+pub struct KotlinWrapper<'a> {
+    config: Config,
+    ci: &'a ComponentInterface,
+    type_helper_code: String,
+    type_imports: BTreeSet<String>,
+}
+
+impl<'a> KotlinWrapper<'a> {
+    pub fn new(config: Config, ci: &'a ComponentInterface) -> Self {
+        let type_renderer = TypeRenderer::new(&config, ci);
+        let type_helper_code = type_renderer.render().unwrap();
+        let type_imports = type_renderer.imports.into_inner();
+        Self {
+            config,
+            ci,
+            type_helper_code,
+            type_imports,
+        }
+    }
+
+    pub fn initialization_fns(&self) -> Vec<String> {
+        self.ci
+            .iter_types()
+            .filter_map(|t| t.initialization_fn(&KotlinCodeOracle))
+            .collect()
+    }
+
+    pub fn imports(&self) -> Vec<String> {
+        self.type_imports.iter().cloned().collect()
+    }
+}
+
+#[derive(Clone)]
+pub struct KotlinCodeOracle;
+
+impl KotlinCodeOracle {
+    // Map `Type` instances to a `Box<dyn CodeType>` for that type.
+    //
+    // There is a companion match in `templates/Types.kt` which performs a similar function for the
+    // template code.
+    //
+    //   - When adding additional types here, make sure to also add a match arm to the `Types.kt` template.
+    //   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+    fn create_code_type(&self, type_: TypeIdentifier) -> Box<dyn CodeType> {
+        match type_ {
+            Type::UInt8 => Box::new(primitives::UInt8CodeType),
+            Type::Int8 => Box::new(primitives::Int8CodeType),
+            Type::UInt16 => Box::new(primitives::UInt16CodeType),
+            Type::Int16 => Box::new(primitives::Int16CodeType),
+            Type::UInt32 => Box::new(primitives::UInt32CodeType),
+            Type::Int32 => Box::new(primitives::Int32CodeType),
+            Type::UInt64 => Box::new(primitives::UInt64CodeType),
+            Type::Int64 => Box::new(primitives::Int64CodeType),
+            Type::Float32 => Box::new(primitives::Float32CodeType),
+            Type::Float64 => Box::new(primitives::Float64CodeType),
+            Type::Boolean => Box::new(primitives::BooleanCodeType),
+            Type::String => Box::new(primitives::StringCodeType),
+
+            Type::Timestamp => Box::new(miscellany::TimestampCodeType),
+            Type::Duration => Box::new(miscellany::DurationCodeType),
+
+            Type::Enum(id) => Box::new(enum_::EnumCodeType::new(id)),
+            Type::Object(id) => Box::new(object::ObjectCodeType::new(id)),
+            Type::Record(id) => Box::new(record::RecordCodeType::new(id)),
+            Type::Error(id) => Box::new(error::ErrorCodeType::new(id)),
+            Type::CallbackInterface(id) => {
+                Box::new(callback_interface::CallbackInterfaceCodeType::new(id))
+            }
+            Type::Optional(inner) => Box::new(compounds::OptionalCodeType::new(*inner)),
+            Type::Sequence(inner) => Box::new(compounds::SequenceCodeType::new(*inner)),
+            Type::Map(key, value) => Box::new(compounds::MapCodeType::new(*key, *value)),
+            Type::External { name, .. } => Box::new(external::ExternalCodeType::new(name)),
+            Type::Custom { name, .. } => Box::new(custom::CustomCodeType::new(name)),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling create_code_type")
+            }
+        }
+    }
+}
+
+impl CodeOracle for KotlinCodeOracle {
+    fn find(&self, type_: &TypeIdentifier) -> Box<dyn CodeType> {
+        self.create_code_type(type_.clone())
+    }
+
+    /// Get the idiomatic Kotlin rendering of a class name (for enums, records, errors, etc).
+    fn class_name(&self, nm: &str) -> String {
+        nm.to_string().to_upper_camel_case()
+    }
+
+    /// Get the idiomatic Kotlin rendering of a function name.
+    fn fn_name(&self, nm: &str) -> String {
+        format!("`{}`", nm.to_string().to_lower_camel_case())
+    }
+
+    /// Get the idiomatic Kotlin rendering of a variable name.
+    fn var_name(&self, nm: &str) -> String {
+        format!("`{}`", nm.to_string().to_lower_camel_case())
+    }
+
+    /// Get the idiomatic Kotlin rendering of an individual enum variant.
+    fn enum_variant_name(&self, nm: &str) -> String {
+        nm.to_string().to_shouty_snake_case()
+    }
+
+    /// Get the idiomatic Kotlin rendering of an exception name
+    ///
+    /// This replaces "Error" at the end of the name with "Exception".  Rust code typically uses
+    /// "Error" for any type of error but in the Java world, "Error" means a non-recoverable error
+    /// and is distinguished from an "Exception".
+    fn error_name(&self, nm: &str) -> String {
+        // errors are a class in kotlin.
+        let name = self.class_name(nm);
+        match name.strip_suffix("Error") {
+            None => name,
+            Some(stripped) => format!("{}Exception", stripped),
+        }
+    }
+
+    fn ffi_type_label(&self, ffi_type: &FFIType) -> String {
+        match ffi_type {
+            // Note that unsigned integers in Kotlin are currently experimental, but java.nio.ByteBuffer does not
+            // support them yet. Thus, we use the signed variants to represent both signed and unsigned
+            // types from the component API.
+            FFIType::Int8 | FFIType::UInt8 => "Byte".to_string(),
+            FFIType::Int16 | FFIType::UInt16 => "Short".to_string(),
+            FFIType::Int32 | FFIType::UInt32 => "Int".to_string(),
+            FFIType::Int64 | FFIType::UInt64 => "Long".to_string(),
+            FFIType::Float32 => "Float".to_string(),
+            FFIType::Float64 => "Double".to_string(),
+            FFIType::RustArcPtr(_) => "Pointer".to_string(),
+            FFIType::RustBuffer => "RustBuffer.ByValue".to_string(),
+            FFIType::ForeignBytes => "ForeignBytes.ByValue".to_string(),
+            FFIType::ForeignCallback => "ForeignCallback".to_string(),
+        }
+    }
+}
+
+pub mod filters {
+    use super::*;
+
+    fn oracle() -> &'static KotlinCodeOracle {
+        &KotlinCodeOracle
+    }
+
+    pub fn type_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(codetype.type_label(oracle()))
+    }
+
+    pub fn canonical_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(codetype.canonical_name(oracle()))
+    }
+
+    pub fn ffi_converter_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(codetype.ffi_converter_name(oracle()))
+    }
+
+    pub fn lower_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lower", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn allocation_size_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!(
+            "{}.allocationSize",
+            codetype.ffi_converter_name(oracle())
+        ))
+    }
+
+    pub fn write_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.write", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn lift_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lift", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn read_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.read", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn render_literal(
+        literal: &Literal,
+        codetype: &impl CodeType,
+    ) -> Result<String, askama::Error> {
+        Ok(codetype.literal(oracle(), literal))
+    }
+
+    /// Get the Kotlin syntax for representing a given low-level `FFIType`.
+    pub fn ffi_type_name(type_: &FFIType) -> Result<String, askama::Error> {
+        Ok(oracle().ffi_type_label(type_))
+    }
+
+    /// Get the idiomatic Kotlin rendering of a class name (for enums, records, errors, etc).
+    pub fn class_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().class_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of a function name.
+    pub fn fn_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().fn_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of a variable name.
+    pub fn var_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().var_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of an individual enum variant.
+    pub fn enum_variant(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().enum_variant_name(nm))
+    }
+
+    /// Get the idiomatic Kotlin rendering of an exception name, replacing
+    /// `Error` with `Exception`.
+    pub fn exception_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().error_name(nm))
+    }
+
+    /// Remove the "`" chars we put around function/variable names
+    ///
+    /// These are used to avoid name clashes with kotlin identifiers, but sometimes you want to
+    /// render the name unquoted.  One example is the message property for errors where we want to
+    /// display the name for the user.
+    pub fn unquote(nm: &str) -> Result<String, askama::Error> {
+        Ok(nm.trim_matches('`').to_string())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/object.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/object.rs
new file mode 100644
index 0000000000..7a1cddbafd
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/object.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ObjectCodeType {
+    id: String,
+}
+
+impl ObjectCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ObjectCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/primitives.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/primitives.rs
new file mode 100644
index 0000000000..b41f7cb49d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/primitives.rs
@@ -0,0 +1,79 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+use crate::interface::{types::Type, Radix};
+use paste::paste;
+
+fn render_literal(_oracle: &dyn CodeOracle, literal: &Literal) -> String {
+    fn typed_number(type_: &Type, num_str: String) -> String {
+        match type_ {
+            // Bytes, Shorts and Ints can all be inferred from the type.
+            Type::Int8 | Type::Int16 | Type::Int32 => num_str,
+            Type::Int64 => format!("{}L", num_str),
+
+            Type::UInt8 | Type::UInt16 | Type::UInt32 => format!("{}u", num_str),
+            Type::UInt64 => format!("{}uL", num_str),
+
+            Type::Float32 => format!("{}f", num_str),
+            Type::Float64 => num_str,
+            _ => panic!("Unexpected literal: {} is not a number", num_str),
+        }
+    }
+
+    match literal {
+        Literal::Boolean(v) => format!("{}", v),
+        Literal::String(s) => format!("\"{}\"", s),
+        Literal::Int(i, radix, type_) => typed_number(
+            type_,
+            match radix {
+                Radix::Octal => format!("{:#x}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+        ),
+        Literal::UInt(i, radix, type_) => typed_number(
+            type_,
+            match radix {
+                Radix::Octal => format!("{:#x}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+        ),
+        Literal::Float(string, type_) => typed_number(type_, string.clone()),
+
+        _ => unreachable!("Literal"),
+    }
+}
+
+macro_rules! impl_code_type_for_primitive {
+    ($T:ty, $class_name:literal) => {
+        paste! {
+            pub struct $T;
+
+            impl CodeType for $T  {
+                fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+                    $class_name.into()
+                }
+
+                fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+                    render_literal(oracle, &literal)
+                }
+            }
+        }
+    };
+}
+
+impl_code_type_for_primitive!(BooleanCodeType, "Boolean");
+impl_code_type_for_primitive!(StringCodeType, "String");
+impl_code_type_for_primitive!(Int8CodeType, "Byte");
+impl_code_type_for_primitive!(Int16CodeType, "Short");
+impl_code_type_for_primitive!(Int32CodeType, "Int");
+impl_code_type_for_primitive!(Int64CodeType, "Long");
+impl_code_type_for_primitive!(UInt8CodeType, "UByte");
+impl_code_type_for_primitive!(UInt16CodeType, "UShort");
+impl_code_type_for_primitive!(UInt32CodeType, "UInt");
+impl_code_type_for_primitive!(UInt64CodeType, "ULong");
+impl_code_type_for_primitive!(Float32CodeType, "Float");
+impl_code_type_for_primitive!(Float64CodeType, "Double");
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/record.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/record.rs
new file mode 100644
index 0000000000..f923f102c4
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/gen_kotlin/record.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct RecordCodeType {
+    id: String,
+}
+
+impl RecordCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for RecordCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/mod.rs
new file mode 100644
index 0000000000..c80b4be93a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/mod.rs
@@ -0,0 +1,117 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use anyhow::{bail, Context, Result};
+use camino::{Utf8Path, Utf8PathBuf};
+use fs_err::{self as fs, File};
+use std::{env, ffi::OsString, io::Write, process::Command};
+
+pub mod gen_kotlin;
+pub use gen_kotlin::{generate_bindings, Config};
+
+use super::super::interface::ComponentInterface;
+
+pub fn write_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+    try_format_code: bool,
+) -> Result<()> {
+    let mut kt_file = full_bindings_path(config, out_dir);
+    fs::create_dir_all(&kt_file)?;
+    kt_file.push(format!("{}.kt", ci.namespace()));
+    let mut f = File::create(&kt_file)?;
+    write!(f, "{}", generate_bindings(config, ci)?)?;
+    if try_format_code {
+        if let Err(e) = Command::new("ktlint").arg("-F").arg(&kt_file).output() {
+            println!(
+                "Warning: Unable to auto-format {} using ktlint: {:?}",
+                kt_file.file_name().unwrap(),
+                e
+            )
+        }
+    }
+    Ok(())
+}
+
+fn full_bindings_path(config: &Config, out_dir: &Utf8Path) -> Utf8PathBuf {
+    let package_path: Utf8PathBuf = config.package_name().split('.').collect();
+    Utf8PathBuf::from(out_dir).join(package_path)
+}
+
+/// Generate kotlin bindings for the given namespace, then use the kotlin
+/// command-line tools to compile them into a .jar file.
+pub fn compile_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+) -> Result<()> {
+    let mut kt_file = full_bindings_path(config, out_dir);
+    kt_file.push(format!("{}.kt", ci.namespace()));
+    let jar_file = out_dir.join(format!("{}.jar", ci.namespace()));
+    let status = Command::new("kotlinc")
+        // Our generated bindings should not produce any warnings; fail tests if they do.
+        .arg("-Werror")
+        .arg("-classpath")
+        .arg(classpath_for_testing(out_dir)?)
+        .arg(&kt_file)
+        .arg("-d")
+        .arg(jar_file)
+        .spawn()
+        .context("Failed to spawn `kotlinc` to compile the bindings")?
+        .wait()
+        .context("Failed to wait for `kotlinc` when compiling the bindings")?;
+    if !status.success() {
+        bail!("running `kotlinc` failed")
+    }
+    Ok(())
+}
+
+/// Execute the specifed kotlin script, with classpath based on the generated
+// artifacts in the given output directory.
+pub fn run_script(out_dir: &Utf8Path, script_file: &Utf8Path) -> Result<()> {
+    let mut cmd = Command::new("kotlinc");
+    // Make sure it can load the .jar and its dependencies.
+    cmd.arg("-classpath").arg(classpath_for_testing(out_dir)?);
+    // Enable runtime assertions, for easy testing etc.
+    cmd.arg("-J-ea");
+    // Our test scripts should not produce any warnings.
+    cmd.arg("-Werror");
+    cmd.arg("-script").arg(script_file);
+    let status = cmd
+        .spawn()
+        .context("Failed to spawn `kotlinc` to run Kotlin script")?
+        .wait()
+        .context("Failed to wait for `kotlinc` when running Kotlin script")?;
+    if !status.success() {
+        bail!("running `kotlinc` failed")
+    }
+    Ok(())
+}
+
+// Calculate the classpath string to use for testing
+pub fn classpath_for_testing(out_dir: &Utf8Path) -> Result<OsString> {
+    let mut classpath = env::var_os("CLASSPATH").unwrap_or_default();
+    // This lets java find the compiled library for the rust component.
+    classpath.push(":");
+    classpath.push(out_dir);
+    // This lets java use any generated .jar files from the output directory.
+    //
+    // Including all .jar files is needed for tests like ext-types that use multiple UDL files.
+    // TODO: Instead of including all .jar files, we should only include jar files that we
+    // previously built for this test.
+    for entry in out_dir
+        .read_dir()
+        .context("Failed to list target directory when running Kotlin script")?
+    {
+        let entry = entry.context("Directory listing failed while running Kotlin script")?;
+        if let Some(ext) = entry.path().extension() {
+            if ext == "jar" {
+                classpath.push(":");
+                classpath.push(entry.path());
+            }
+        }
+    }
+    Ok(classpath)
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/BooleanHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/BooleanHelper.kt
new file mode 100644
index 0000000000..8cfa2ce000
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/BooleanHelper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterBoolean: FfiConverter<Boolean, Byte> {
+    override fun lift(value: Byte): Boolean {
+        return value.toInt() != 0
+    }
+
+    override fun read(buf: ByteBuffer): Boolean {
+        return lift(buf.get())
+    }
+
+    override fun lower(value: Boolean): Byte {
+        return if (value) 1.toByte() else 0.toByte()
+    }
+
+    override fun allocationSize(value: Boolean) = 1
+
+    override fun write(value: Boolean, buf: ByteBuffer) {
+        buf.put(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceRuntime.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceRuntime.kt
new file mode 100644
index 0000000000..3f5d72a608
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceRuntime.kt
@@ -0,0 +1,74 @@
+internal typealias Handle = Long
+internal class ConcurrentHandleMap<T>(
+    private val leftMap: MutableMap<Handle, T> = mutableMapOf(),
+    private val rightMap: MutableMap<T, Handle> = mutableMapOf()
+) {
+    private val lock = java.util.concurrent.locks.ReentrantLock()
+    private val currentHandle = AtomicLong(0L)
+    private val stride = 1L
+
+    fun insert(obj: T): Handle =
+        lock.withLock {
+            rightMap[obj] ?:
+                currentHandle.getAndAdd(stride)
+                    .also { handle ->
+                        leftMap[handle] = obj
+                        rightMap[obj] = handle
+                    }
+            }
+
+    fun get(handle: Handle) = lock.withLock {
+        leftMap[handle]
+    }
+
+    fun delete(handle: Handle) {
+        this.remove(handle)
+    }
+
+    fun remove(handle: Handle): T? =
+        lock.withLock {
+            leftMap.remove(handle)?.let { obj ->
+                rightMap.remove(obj)
+                obj
+            }
+        }
+}
+
+interface ForeignCallback : com.sun.jna.Callback {
+    public fun invoke(handle: Handle, method: Int, args: RustBuffer.ByValue, outBuf: RustBufferByReference): Int
+}
+
+// Magic number for the Rust proxy to call using the same mechanism as every other method,
+// to free the callback once it's dropped by Rust.
+internal const val IDX_CALLBACK_FREE = 0
+
+public abstract class FfiConverterCallbackInterface<CallbackInterface>(
+    protected val foreignCallback: ForeignCallback
+): FfiConverter<CallbackInterface, Handle> {
+    private val handleMap = ConcurrentHandleMap<CallbackInterface>()
+
+    // Registers the foreign callback with the Rust side.
+    // This method is generated for each callback interface.
+    internal abstract fun register(lib: _UniFFILib)
+
+    fun drop(handle: Handle): RustBuffer.ByValue {
+        return handleMap.remove(handle).let { RustBuffer.ByValue() }
+    }
+
+    override fun lift(value: Handle): CallbackInterface {
+        return handleMap.get(value) ?: throw InternalException("No callback in handlemap; this is a Uniffi bug")
+    }
+
+    override fun read(buf: ByteBuffer) = lift(buf.getLong())
+
+    override fun lower(value: CallbackInterface) =
+        handleMap.insert(value).also {
+            assert(handleMap.get(it) === value) { "Handle map is not returning the object we just placed there. This is a bug in the HandleMap." }
+        }
+
+    override fun allocationSize(value: CallbackInterface) = 8
+
+    override fun write(value: CallbackInterface, buf: ByteBuffer) {
+        buf.putLong(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceTemplate.kt
new file mode 100644
index 0000000000..5e18797345
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceTemplate.kt
@@ -0,0 +1,130 @@
+{%- let cbi = ci.get_callback_interface_definition(name).unwrap() %}
+{%- let type_name = cbi|type_name %}
+{%- let foreign_callback = format!("ForeignCallback{}", canonical_type_name) %}
+
+{% if self.include_once_check("CallbackInterfaceRuntime.kt") %}{% include "CallbackInterfaceRuntime.kt" %}{% endif %}
+{{- self.add_import("java.util.concurrent.atomic.AtomicLong") }}
+{{- self.add_import("java.util.concurrent.locks.ReentrantLock") }}
+{{- self.add_import("kotlin.concurrent.withLock") }}
+
+// Declaration and FfiConverters for {{ type_name }} Callback Interface
+
+public interface {{ type_name }} {
+    {% for meth in cbi.methods() -%}
+    fun {{ meth.name()|fn_name }}({% call kt::arg_list_decl(meth) %})
+    {%- match meth.return_type() -%}
+    {%- when Some with (return_type) %}: {{ return_type|type_name -}}
+    {%- else -%}
+    {%- endmatch %}
+    {% endfor %}
+}
+
+// The ForeignCallback that is passed to Rust.
+internal class {{ foreign_callback }} : ForeignCallback {
+    @Suppress("TooGenericExceptionCaught")
+    override fun invoke(handle: Handle, method: Int, args: RustBuffer.ByValue, outBuf: RustBufferByReference): Int {
+        val cb = {{ ffi_converter_name }}.lift(handle)
+        return when (method) {
+            IDX_CALLBACK_FREE -> {
+                {{ ffi_converter_name }}.drop(handle)
+                // No return value.
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+                0
+            }
+            {% for meth in cbi.methods() -%}
+            {% let method_name = format!("invoke_{}", meth.name())|fn_name -%}
+            {{ loop.index }} -> {
+                // Call the method, write to outBuf and return a status code
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs` for info
+                try {
+                    {%- match meth.throws_type() %}
+                    {%- when Some(error_type) %}
+                    try {
+                        val buffer = this.{{ method_name }}(cb, args)
+                        // Success
+                        outBuf.setValue(buffer)
+                        1
+                    } catch (e: {{ error_type|type_name }}) {
+                        // Expected error
+                        val buffer = {{ error_type|ffi_converter_name }}.lowerIntoRustBuffer(e)
+                        outBuf.setValue(buffer)
+                        -2
+                    }
+                    {%- else %} 
+                    val buffer = this.{{ method_name }}(cb, args)
+                    // Success
+                    outBuf.setValue(buffer)
+                    1
+                    {%- endmatch %}
+                } catch (e: Throwable) {
+                    // Unexpected error
+                    try {
+                        // Try to serialize the error into a string
+                        outBuf.setValue({{ Type::String.borrow()|ffi_converter_name }}.lower(e.toString()))
+                    } catch (e: Throwable) {
+                        // If that fails, then it's time to give up and just return
+                    }
+                    -1
+                }
+            }
+            {% endfor %}
+            else -> {
+                // An unexpected error happened.
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+                try {
+                    // Try to serialize the error into a string
+                    outBuf.setValue({{ Type::String.borrow()|ffi_converter_name }}.lower("Invalid Callaback index"))
+                } catch (e: Throwable) {
+                    // If that fails, then it's time to give up and just return
+                }
+                -1
+            }
+        }
+    }
+
+    {% for meth in cbi.methods() -%}
+    {% let method_name = format!("invoke_{}", meth.name())|fn_name %}
+    private fun {{ method_name }}(kotlinCallbackInterface: {{ type_name }}, args: RustBuffer.ByValue): RustBuffer.ByValue =
+        try {
+        {#- Unpacking args from the RustBuffer #}
+            {%- if meth.arguments().len() != 0 -%}
+            {#- Calling the concrete callback object #}
+            val buf = args.asByteBuffer() ?: throw InternalException("No ByteBuffer in RustBuffer; this is a Uniffi bug")
+            kotlinCallbackInterface.{{ meth.name()|fn_name }}(
+                    {% for arg in meth.arguments() -%}
+                    {{ arg|read_fn }}(buf)
+                    {%- if !loop.last %}, {% endif %}
+                    {% endfor -%}
+                )
+            {% else %}
+            kotlinCallbackInterface.{{ meth.name()|fn_name }}()
+            {% endif -%}
+
+        {#- Packing up the return value into a RustBuffer #}
+                {%- match meth.return_type() -%}
+                {%- when Some with (return_type) -%}
+                .let {
+                    {{ return_type|ffi_converter_name }}.lowerIntoRustBuffer(it)
+                }
+                {%- else -%}
+                .let { RustBuffer.ByValue() }
+                {% endmatch -%}
+                // TODO catch errors and report them back to Rust.
+                // https://github.com/mozilla/uniffi-rs/issues/351
+        } finally {
+            RustBuffer.free(args)
+        }
+
+    {% endfor %}
+}
+
+// The ffiConverter which transforms the Callbacks in to Handles to pass to Rust.
+public object {{ ffi_converter_name }}: FfiConverterCallbackInterface<{{ type_name }}>(
+    foreignCallback = {{ foreign_callback }}()
+) {
+    override fun register(lib: _UniFFILib) {
+        rustCall() { status ->
+            lib.{{ cbi.ffi_init_callback().name() }}(this.foreignCallback, status)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CustomTypeTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CustomTypeTemplate.kt
new file mode 100644
index 0000000000..c7807f2f33
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/CustomTypeTemplate.kt
@@ -0,0 +1,62 @@
+{%- match kotlin_config.custom_types.get(name.as_str())  %}
+{%- when None %}
+{#- Define the type using typealiases to the builtin #}
+/**
+ * Typealias from the type name used in the UDL file to the builtin type.  This
+ * is needed because the UDL type name is used in function/method signatures.
+ * It's also what we have an external type that references a custom type.
+ */
+public typealias {{ name }} = {{ builtin|type_name }}
+public typealias {{ ffi_converter_name }} = {{ builtin|ffi_converter_name }}
+
+{%- when Some with (config) %}
+
+{%- let ffi_type_name=builtin.ffi_type().borrow()|ffi_type_name %}
+
+{# When the config specifies a different type name, create a typealias for it #}
+{%- match config.type_name %}
+{%- when Some(concrete_type_name) %}
+/**
+ * Typealias from the type name used in the UDL file to the custom type.  This
+ * is needed because the UDL type name is used in function/method signatures.
+ * It's also what we have an external type that references a custom type.
+ */
+public typealias {{ name }} = {{ concrete_type_name }}
+{%- else %}
+{%- endmatch %}
+
+{%- match config.imports %}
+{%- when Some(imports) %}
+{%- for import_name in imports %}
+{{ self.add_import(import_name) }}
+{%- endfor %}
+{%- else %}
+{%- endmatch %}
+
+public object {{ ffi_converter_name }}: FfiConverter<{{ name }}, {{ ffi_type_name }}> {
+    override fun lift(value: {{ ffi_type_name }}): {{ name }} {
+        val builtinValue = {{ builtin|lift_fn }}(value)
+        return {{ config.into_custom.render("builtinValue") }}
+    }
+
+    override fun lower(value: {{ name }}): {{ ffi_type_name }} {
+        val builtinValue = {{ config.from_custom.render("value") }}
+        return {{ builtin|lower_fn }}(builtinValue)
+    }
+
+    override fun read(buf: ByteBuffer): {{ name }} {
+        val builtinValue = {{ builtin|read_fn }}(buf)
+        return {{ config.into_custom.render("builtinValue") }}
+    }
+
+    override fun allocationSize(value: {{ name }}): Int {
+        val builtinValue = {{ config.from_custom.render("value") }}
+        return {{ builtin|allocation_size_fn }}(builtinValue)
+    }
+
+    override fun write(value: {{ name }}, buf: ByteBuffer) {
+        val builtinValue = {{ config.from_custom.render("value") }}
+        {{ builtin|write_fn }}(builtinValue, buf)
+    }
+}
+{%- endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/DurationHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/DurationHelper.kt
new file mode 100644
index 0000000000..4237c6f9a8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/DurationHelper.kt
@@ -0,0 +1,36 @@
+public object FfiConverterDuration: FfiConverterRustBuffer<java.time.Duration> {
+    override fun read(buf: ByteBuffer): java.time.Duration {
+        // Type mismatch (should be u64) but we check for overflow/underflow below
+        val seconds = buf.getLong()
+        // Type mismatch (should be u32) but we check for overflow/underflow below
+        val nanoseconds = buf.getInt().toLong()
+        if (seconds < 0) {
+            throw java.time.DateTimeException("Duration exceeds minimum or maximum value supported by uniffi")
+        }
+        if (nanoseconds < 0) {
+            throw java.time.DateTimeException("Duration nanoseconds exceed minimum or maximum supported by uniffi")
+        }
+        return java.time.Duration.ofSeconds(seconds, nanoseconds)
+    }
+
+    // 8 bytes for seconds, 4 bytes for nanoseconds
+    override fun allocationSize(value: java.time.Duration) = 12
+
+    override fun write(value: java.time.Duration, buf: ByteBuffer) {
+        if (value.seconds < 0) {
+            // Rust does not support negative Durations
+            throw IllegalArgumentException("Invalid duration, must be non-negative")
+        }
+
+        if (value.nano < 0) {
+            // Java docs provide guarantee that nano will always be positive, so this should be impossible
+            // See: https://docs.oracle.com/javase/8/docs/api/java/time/Duration.html
+            throw IllegalArgumentException("Invalid duration, nano value must be non-negative")
+        }
+
+        // Type mismatch (should be u64) but since Rust doesn't support negative durations we should be OK
+        buf.putLong(value.seconds)
+        // Type mismatch (should be u32) but since values will always be between 0 and 999,999,999 it should be OK
+        buf.putInt(value.nano)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/EnumTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/EnumTemplate.kt
new file mode 100644
index 0000000000..2422046e37
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/EnumTemplate.kt
@@ -0,0 +1,107 @@
+{#
+// Kotlin's `enum class` constuct doesn't support variants with associated data,
+// but is a little nicer for consumers than its `sealed class` enum pattern.
+// So, we switch here, using `enum class` for enums with no associated data
+// and `sealed class` for the general case.
+#}
+{%- let e = ci.get_enum_definition(name).unwrap() %}
+
+{%- if e.is_flat() %}
+
+enum class {{ type_name }} {
+    {% for variant in e.variants() -%}
+    {{ variant.name()|enum_variant }}{% if loop.last %};{% else %},{% endif %}
+    {%- endfor %}
+}
+
+public object {{ e|ffi_converter_name }}: FfiConverterRustBuffer<{{ type_name }}> {
+    override fun read(buf: ByteBuffer) = try {
+        {{ type_name }}.values()[buf.getInt() - 1]
+    } catch (e: IndexOutOfBoundsException) {
+        throw RuntimeException("invalid enum value, something is very wrong!!", e)
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = 4
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        buf.putInt(value.ordinal + 1)
+    }
+}
+
+{% else %}
+
+sealed class {{ type_name }}{% if contains_object_references %}: Disposable {% endif %} {
+    {% for variant in e.variants() -%}
+    {% if !variant.has_fields() -%}
+    object {{ variant.name()|class_name }} : {{ type_name }}()
+    {% else -%}
+    data class {{ variant.name()|class_name }}(
+        {% for field in variant.fields() -%}
+        val {{ field.name()|var_name }}: {{ field|type_name}}{% if loop.last %}{% else %}, {% endif %}
+        {% endfor -%}
+    ) : {{ type_name }}()
+    {%- endif %}
+    {% endfor %}
+
+    {% if contains_object_references %}
+    @Suppress("UNNECESSARY_SAFE_CALL") // codegen is much simpler if we unconditionally emit safe calls here
+    override fun destroy() {
+        when(this) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|class_name }} -> {
+                {%- if variant.has_fields() %}
+                {% call kt::destroy_fields(variant) %}
+                {% else -%}
+                // Nothing to destroy
+                {%- endif %}
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+    {% endif %}
+}
+
+public object {{ e|ffi_converter_name }} : FfiConverterRustBuffer<{{ type_name }}>{
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        return when(buf.getInt()) {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} -> {{ type_name }}.{{ variant.name()|class_name }}{% if variant.has_fields() %}(
+                {% for field in variant.fields() -%}
+                {{ field|read_fn }}(buf),
+                {% endfor -%}
+            ){%- endif -%}
+            {%- endfor %}
+            else -> throw RuntimeException("invalid enum value, something is very wrong!!")
+        }
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = when(value) {
+        {%- for variant in e.variants() %}
+        is {{ type_name }}.{{ variant.name()|class_name }} -> {
+            // Add the size for the Int that specifies the variant plus the size needed for all fields
+            (
+                4
+                {%- for field in variant.fields() %}
+                + {{ field|allocation_size_fn }}(value.{{ field.name()|var_name }})
+                {%- endfor %}
+            )
+        }
+        {%- endfor %}
+    }
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        when(value) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|class_name }} -> {
+                buf.putInt({{ loop.index }})
+                {%- for field in variant.fields() %}
+                {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+                {%- endfor %}
+                Unit
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+}
+
+{% endif %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ErrorTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ErrorTemplate.kt
new file mode 100644
index 0000000000..9ddef9bb73
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ErrorTemplate.kt
@@ -0,0 +1,109 @@
+{%- let e = ci.get_error_definition(name).unwrap() %}
+
+{% if e.is_flat() %}
+sealed class {{ type_name }}(message: String): Exception(message){% if contains_object_references %}, Disposable {% endif %} {
+        // Each variant is a nested class
+        // Flat enums carries a string error message, so no special implementation is necessary.
+        {% for variant in e.variants() -%}
+        class {{ variant.name()|exception_name }}(message: String) : {{ type_name }}(message)
+        {% endfor %}
+
+    companion object ErrorHandler : CallStatusErrorHandler<{{ type_name }}> {
+        override fun lift(error_buf: RustBuffer.ByValue): {{ type_name }} = {{ e|lift_fn }}(error_buf)
+    }
+}
+{%- else %}
+sealed class {{ type_name }}: Exception(){% if contains_object_references %}, Disposable {% endif %} {
+    // Each variant is a nested class
+    {% for variant in e.variants() -%}
+    {%- let variant_name = variant.name()|exception_name %}
+    class {{ variant_name }}(
+        {% for field in variant.fields() -%}
+        val {{ field.name()|var_name }}: {{ field|type_name}}{% if loop.last %}{% else %}, {% endif %}
+        {% endfor -%}
+    ) : {{ type_name }}() {
+        override val message
+            get() = "{%- for field in variant.fields() %}{{ field.name()|var_name|unquote }}=${ {{field.name()|var_name }} }{% if !loop.last %}, {% endif %}{% endfor %}"
+    }
+    {% endfor %}
+
+    companion object ErrorHandler : CallStatusErrorHandler<{{ type_name }}> {
+        override fun lift(error_buf: RustBuffer.ByValue): {{ type_name }} = {{ e|lift_fn }}(error_buf)
+    }
+
+    {% if contains_object_references %}
+    @Suppress("UNNECESSARY_SAFE_CALL") // codegen is much simpler if we unconditionally emit safe calls here
+    override fun destroy() {
+        when(this) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|exception_name }} -> {
+                {%- if variant.has_fields() %}
+                {% call kt::destroy_fields(variant) %}
+                {% else -%}
+                // Nothing to destroy
+                {%- endif %}
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+    {% endif %}
+}
+{%- endif %}
+
+public object {{ e|ffi_converter_name }} : FfiConverterRustBuffer<{{ type_name }}> {
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        {% if e.is_flat() %}
+            return when(buf.getInt()) {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} -> {{ type_name }}.{{ variant.name()|exception_name }}({{ TypeIdentifier::String.borrow()|read_fn }}(buf))
+            {%- endfor %}
+            else -> throw RuntimeException("invalid error enum value, something is very wrong!!")
+        }
+        {% else %}
+
+        return when(buf.getInt()) {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} -> {{ type_name }}.{{ variant.name()|exception_name }}({% if variant.has_fields() %}
+                {% for field in variant.fields() -%}
+                {{ field|read_fn }}(buf),
+                {% endfor -%}
+            {%- endif -%})
+            {%- endfor %}
+            else -> throw RuntimeException("invalid error enum value, something is very wrong!!")
+        }
+        {%- endif %}
+    }
+
+    override fun allocationSize(value: {{ type_name }}): Int {
+        {%- if e.is_flat() %}
+        return 4
+        {%- else %}
+        return when(value) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|exception_name }} -> (
+                // Add the size for the Int that specifies the variant plus the size needed for all fields
+                4
+                {%- for field in variant.fields() %}
+                + {{ field|allocation_size_fn }}(value.{{ field.name()|var_name }})
+                {%- endfor %}
+            )
+            {%- endfor %}
+        }
+        {%- endif %}
+    }
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        when(value) {
+            {%- for variant in e.variants() %}
+            is {{ type_name }}.{{ variant.name()|exception_name }} -> {
+                buf.putInt({{ loop.index }})
+                {%- for field in variant.fields() %}
+                {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+                {%- endfor %}
+                Unit
+            }
+            {%- endfor %}
+        }.let { /* this makes the `when` an expression, which ensures it is exhaustive */ }
+    }
+
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ExternalTypeTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ExternalTypeTemplate.kt
new file mode 100644
index 0000000000..6d10c37e31
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ExternalTypeTemplate.kt
@@ -0,0 +1,6 @@
+{%- let package_name=self.external_type_package_name(crate_name) %}
+{%- let fully_qualified_type_name = "{}.{}"|format(package_name, name) %}
+{%- let fully_qualified_ffi_converter_name = "{}.FfiConverterType{}"|format(package_name, name) %}
+
+{{- self.add_import(fully_qualified_type_name) }}
+{{ self.add_import(fully_qualified_ffi_converter_name) }}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/FfiConverterTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/FfiConverterTemplate.kt
new file mode 100644
index 0000000000..3b2c9d225a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/FfiConverterTemplate.kt
@@ -0,0 +1,71 @@
+// The FfiConverter interface handles converter types to and from the FFI
+//
+// All implementing objects should be public to support external types.  When a
+// type is external we need to import it's FfiConverter.
+public interface FfiConverter<KotlinType, FfiType> {
+    // Convert an FFI type to a Kotlin type
+    fun lift(value: FfiType): KotlinType
+
+    // Convert an Kotlin type to an FFI type
+    fun lower(value: KotlinType): FfiType
+
+    // Read a Kotlin type from a `ByteBuffer`
+    fun read(buf: ByteBuffer): KotlinType
+
+    // Calculate bytes to allocate when creating a `RustBuffer`
+    //
+    // This must return at least as many bytes as the write() function will
+    // write. It can return more bytes than needed, for example when writing
+    // Strings we can't know the exact bytes needed until we the UTF-8
+    // encoding, so we pessimistically allocate the largest size possible (3
+    // bytes per codepoint).  Allocating extra bytes is not really a big deal
+    // because the `RustBuffer` is short-lived.
+    fun allocationSize(value: KotlinType): Int
+
+    // Write a Kotlin type to a `ByteBuffer`
+    fun write(value: KotlinType, buf: ByteBuffer)
+
+    // Lower a value into a `RustBuffer`
+    //
+    // This method lowers a value into a `RustBuffer` rather than the normal
+    // FfiType.  It's used by the callback interface code.  Callback interface
+    // returns are always serialized into a `RustBuffer` regardless of their
+    // normal FFI type.
+    fun lowerIntoRustBuffer(value: KotlinType): RustBuffer.ByValue {
+        val rbuf = RustBuffer.alloc(allocationSize(value))
+        try {
+            val bbuf = rbuf.data!!.getByteBuffer(0, rbuf.capacity.toLong()).also {
+                it.order(ByteOrder.BIG_ENDIAN)
+            }
+            write(value, bbuf)
+            rbuf.writeField("len", bbuf.position())
+            return rbuf
+        } catch (e: Throwable) {
+            RustBuffer.free(rbuf)
+            throw e
+        }
+    }
+
+    // Lift a value from a `RustBuffer`.
+    //
+    // This here mostly because of the symmetry with `lowerIntoRustBuffer()`.
+    // It's currently only used by the `FfiConverterRustBuffer` class below.
+    fun liftFromRustBuffer(rbuf: RustBuffer.ByValue): KotlinType {
+        val byteBuf = rbuf.asByteBuffer()!!
+        try {
+           val item = read(byteBuf)
+           if (byteBuf.hasRemaining()) {
+               throw RuntimeException("junk remaining in buffer after lifting, something is very wrong!!")
+           }
+           return item
+        } finally {
+            RustBuffer.free(rbuf)
+        }
+    }
+}
+
+// FfiConverter that uses `RustBuffer` as the FfiType
+public interface FfiConverterRustBuffer<KotlinType>: FfiConverter<KotlinType, RustBuffer.ByValue> {
+    override fun lift(value: RustBuffer.ByValue) = liftFromRustBuffer(value)
+    override fun lower(value: KotlinType) = lowerIntoRustBuffer(value)
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float32Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float32Helper.kt
new file mode 100644
index 0000000000..eafec5d122
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float32Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterFloat: FfiConverter<Float, Float> {
+    override fun lift(value: Float): Float {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Float {
+        return buf.getFloat()
+    }
+
+    override fun lower(value: Float): Float {
+        return value
+    }
+
+    override fun allocationSize(value: Float) = 4
+
+    override fun write(value: Float, buf: ByteBuffer) {
+        buf.putFloat(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float64Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float64Helper.kt
new file mode 100644
index 0000000000..9fc2892c95
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Float64Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterDouble: FfiConverter<Double, Double> {
+    override fun lift(value: Double): Double {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Double {
+        return buf.getDouble()
+    }
+
+    override fun lower(value: Double): Double {
+        return value
+    }
+
+    override fun allocationSize(value: Double) = 8
+
+    override fun write(value: Double, buf: ByteBuffer) {
+        buf.putDouble(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Helpers.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Helpers.kt
new file mode 100644
index 0000000000..d7e61ef4c7
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Helpers.kt
@@ -0,0 +1,66 @@
+// A handful of classes and functions to support the generated data structures.
+// This would be a good candidate for isolating in its own ffi-support lib.
+// Error runtime.
+@Structure.FieldOrder("code", "error_buf")
+internal open class RustCallStatus : Structure() {
+    @JvmField var code: Int = 0
+    @JvmField var error_buf: RustBuffer.ByValue = RustBuffer.ByValue()
+
+    fun isSuccess(): Boolean {
+        return code == 0
+    }
+
+    fun isError(): Boolean {
+        return code == 1
+    }
+
+    fun isPanic(): Boolean {
+        return code == 2
+    }
+}
+
+class InternalException(message: String) : Exception(message)
+
+// Each top-level error class has a companion object that can lift the error from the call status's rust buffer
+interface CallStatusErrorHandler<E> {
+    fun lift(error_buf: RustBuffer.ByValue): E;
+}
+
+// Helpers for calling Rust
+// In practice we usually need to be synchronized to call this safely, so it doesn't
+// synchronize itself
+
+// Call a rust function that returns a Result<>.  Pass in the Error class companion that corresponds to the Err
+private inline fun <U, E: Exception> rustCallWithError(errorHandler: CallStatusErrorHandler<E>, callback: (RustCallStatus) -> U): U {
+    var status = RustCallStatus();
+    val return_value = callback(status)
+    if (status.isSuccess()) {
+        return return_value
+    } else if (status.isError()) {
+        throw errorHandler.lift(status.error_buf)
+    } else if (status.isPanic()) {
+        // when the rust code sees a panic, it tries to construct a rustbuffer
+        // with the message.  but if that code panics, then it just sends back
+        // an empty buffer.
+        if (status.error_buf.len > 0) {
+            throw InternalException({{ TypeIdentifier::String.borrow()|lift_fn }}(status.error_buf))
+        } else {
+            throw InternalException("Rust panic")
+        }
+    } else {
+        throw InternalException("Unknown rust call status: $status.code")
+    }
+}
+
+// CallStatusErrorHandler implementation for times when we don't expect a CALL_ERROR
+object NullCallStatusErrorHandler: CallStatusErrorHandler<InternalException> {
+    override fun lift(error_buf: RustBuffer.ByValue): InternalException {
+        RustBuffer.free(error_buf)
+        return InternalException("Unexpected CALL_ERROR")
+    }
+}
+
+// Call a rust function that returns a plain value
+private inline fun <U> rustCall(callback: (RustCallStatus) -> U): U {
+    return rustCallWithError(NullCallStatusErrorHandler, callback);
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int16Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int16Helper.kt
new file mode 100644
index 0000000000..75564276be
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int16Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterShort: FfiConverter<Short, Short> {
+    override fun lift(value: Short): Short {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Short {
+        return buf.getShort()
+    }
+
+    override fun lower(value: Short): Short {
+        return value
+    }
+
+    override fun allocationSize(value: Short) = 2
+
+    override fun write(value: Short, buf: ByteBuffer) {
+        buf.putShort(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int32Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int32Helper.kt
new file mode 100644
index 0000000000..b7a8131c8b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int32Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterInt: FfiConverter<Int, Int> {
+    override fun lift(value: Int): Int {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Int {
+        return buf.getInt()
+    }
+
+    override fun lower(value: Int): Int {
+        return value
+    }
+
+    override fun allocationSize(value: Int) = 4
+
+    override fun write(value: Int, buf: ByteBuffer) {
+        buf.putInt(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int64Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int64Helper.kt
new file mode 100644
index 0000000000..601cfc7c2c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int64Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterLong: FfiConverter<Long, Long> {
+    override fun lift(value: Long): Long {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Long {
+        return buf.getLong()
+    }
+
+    override fun lower(value: Long): Long {
+        return value
+    }
+
+    override fun allocationSize(value: Long) = 8
+
+    override fun write(value: Long, buf: ByteBuffer) {
+        buf.putLong(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int8Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int8Helper.kt
new file mode 100644
index 0000000000..9237768dbf
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Int8Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterByte: FfiConverter<Byte, Byte> {
+    override fun lift(value: Byte): Byte {
+        return value
+    }
+
+    override fun read(buf: ByteBuffer): Byte {
+        return buf.get()
+    }
+
+    override fun lower(value: Byte): Byte {
+        return value
+    }
+
+    override fun allocationSize(value: Byte) = 1
+
+    override fun write(value: Byte, buf: ByteBuffer) {
+        buf.put(value)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/MapTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/MapTemplate.kt
new file mode 100644
index 0000000000..c8cbecb68b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/MapTemplate.kt
@@ -0,0 +1,35 @@
+{%- let key_type_name = key_type|type_name %}
+{%- let value_type_name = value_type|type_name %}
+public object {{ ffi_converter_name }}: FfiConverterRustBuffer<Map<{{ key_type_name }}, {{ value_type_name }}>> {
+    override fun read(buf: ByteBuffer): Map<{{ key_type_name }}, {{ value_type_name }}> {
+        // TODO: Once Kotlin's `buildMap` API is stabilized we should use it here.
+        val items : MutableMap<{{ key_type_name }}, {{ value_type_name }}> = mutableMapOf()
+        val len = buf.getInt()
+        repeat(len) {
+            val k = {{ key_type|read_fn }}(buf)
+            val v = {{ value_type|read_fn }}(buf)
+            items[k] = v
+        }
+        return items
+    }
+
+    override fun allocationSize(value: Map<{{ key_type_name }}, {{ value_type_name }}>): Int {
+        val spaceForMapSize = 4
+        val spaceForChildren = value.map { (k, v) ->
+            {{ key_type|allocation_size_fn }}(k) +
+            {{ value_type|allocation_size_fn }}(v)
+        }.sum()
+        return spaceForMapSize + spaceForChildren
+    }
+
+    override fun write(value: Map<{{ key_type_name }}, {{ value_type_name }}>, buf: ByteBuffer) {
+        buf.putInt(value.size)
+        // The parens on `(k, v)` here ensure we're calling the right method,
+        // which is important for compatibility with older android devices.
+        // Ref https://blog.danlew.net/2017/03/16/kotlin-puzzler-whose-line-is-it-anyways/
+        value.forEach { (k, v) ->
+            {{ key_type|write_fn }}(k, buf)
+            {{ value_type|write_fn }}(v, buf)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/NamespaceLibraryTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/NamespaceLibraryTemplate.kt
new file mode 100644
index 0000000000..df96ee5cbb
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/NamespaceLibraryTemplate.kt
@@ -0,0 +1,40 @@
+@Synchronized
+private fun findLibraryName(componentName: String): String {
+    val libOverride = System.getProperty("uniffi.component.$componentName.libraryOverride")
+    if (libOverride != null) {
+        return libOverride
+    }
+    return "{{ config.cdylib_name() }}"
+}
+
+private inline fun <reified Lib : Library> loadIndirect(
+    componentName: String
+): Lib {
+    return Native.load<Lib>(findLibraryName(componentName), Lib::class.java)
+}
+
+// A JNA Library to expose the extern-C FFI definitions.
+// This is an implementation detail which will be called internally by the public API.
+
+internal interface _UniFFILib : Library {
+    companion object {
+        internal val INSTANCE: _UniFFILib by lazy {
+            loadIndirect<_UniFFILib>(componentName = "{{ ci.namespace() }}")
+            {% let initialization_fns = self.initialization_fns() %}
+            {%- if !initialization_fns.is_empty() -%}
+            .also { lib: _UniFFILib ->
+                {% for fn in initialization_fns -%}
+                {{ fn }}(lib)
+                {% endfor -%}
+            }
+            {% endif %}
+        }
+    }
+
+    {% for func in ci.iter_ffi_function_definitions() -%}
+    fun {{ func.name() }}(
+        {%- call kt::arg_list_ffi_decl(func) %}
+    ){%- match func.return_type() -%}{%- when Some with (type_) %}: {{ type_.borrow()|ffi_type_name }}{% when None %}: Unit{% endmatch %}
+
+    {% endfor %}
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectRuntime.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectRuntime.kt
new file mode 100644
index 0000000000..5265c09441
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectRuntime.kt
@@ -0,0 +1,161 @@
+// Interface implemented by anything that can contain an object reference.
+//
+// Such types expose a `destroy()` method that must be called to cleanly
+// dispose of the contained objects. Failure to call this method may result
+// in memory leaks.
+//
+// The easiest way to ensure this method is called is to use the `.use`
+// helper method to execute a block and destroy the object at the end.
+interface Disposable {
+    fun destroy()
+    companion object {
+        fun destroy(vararg args: Any?) {
+            args.filterIsInstance<Disposable>()
+                .forEach(Disposable::destroy)
+        }
+    }
+}
+
+inline fun <T : Disposable?, R> T.use(block: (T) -> R) =
+    try {
+        block(this)
+    } finally {
+        try {
+            // N.B. our implementation is on the nullable type `Disposable?`.
+            this?.destroy()
+        } catch (e: Throwable) {
+            // swallow
+        }
+    }
+
+// The base class for all UniFFI Object types.
+//
+// This class provides core operations for working with the Rust `Arc<T>` pointer to
+// the live Rust struct on the other side of the FFI.
+//
+// There's some subtlety here, because we have to be careful not to operate on a Rust
+// struct after it has been dropped, and because we must expose a public API for freeing
+// the Kotlin wrapper object in lieu of reliable finalizers. The core requirements are:
+//
+//   * Each `FFIObject` instance holds an opaque pointer to the underlying Rust struct.
+//     Method calls need to read this pointer from the object's state and pass it in to
+//     the Rust FFI.
+//
+//   * When an `FFIObject` is no longer needed, its pointer should be passed to a
+//     special destructor function provided by the Rust FFI, which will drop the
+//     underlying Rust struct.
+//
+//   * Given an `FFIObject` instance, calling code is expected to call the special
+//     `destroy` method in order to free it after use, either by calling it explicitly
+//     or by using a higher-level helper like the `use` method. Failing to do so will
+//     leak the underlying Rust struct.
+//
+//   * We can't assume that calling code will do the right thing, and must be prepared
+//     to handle Kotlin method calls executing concurrently with or even after a call to
+//     `destroy`, and to handle multiple (possibly concurrent!) calls to `destroy`.
+//
+//   * We must never allow Rust code to operate on the underlying Rust struct after
+//     the destructor has been called, and must never call the destructor more than once.
+//     Doing so may trigger memory unsafety.
+//
+// If we try to implement this with mutual exclusion on access to the pointer, there is the
+// possibility of a race between a method call and a concurrent call to `destroy`:
+//
+//    * Thread A starts a method call, reads the value of the pointer, but is interrupted
+//      before it can pass the pointer over the FFI to Rust.
+//    * Thread B calls `destroy` and frees the underlying Rust struct.
+//    * Thread A resumes, passing the already-read pointer value to Rust and triggering
+//      a use-after-free.
+//
+// One possible solution would be to use a `ReadWriteLock`, with each method call taking
+// a read lock (and thus allowed to run concurrently) and the special `destroy` method
+// taking a write lock (and thus blocking on live method calls). However, we aim not to
+// generate methods with any hidden blocking semantics, and a `destroy` method that might
+// block if called incorrectly seems to meet that bar.
+//
+// So, we achieve our goals by giving each `FFIObject` an associated `AtomicLong` counter to track
+// the number of in-flight method calls, and an `AtomicBoolean` flag to indicate whether `destroy`
+// has been called. These are updated according to the following rules:
+//
+//    * The initial value of the counter is 1, indicating a live object with no in-flight calls.
+//      The initial value for the flag is false.
+//
+//    * At the start of each method call, we atomically check the counter.
+//      If it is 0 then the underlying Rust struct has already been destroyed and the call is aborted.
+//      If it is nonzero them we atomically increment it by 1 and proceed with the method call.
+//
+//    * At the end of each method call, we atomically decrement and check the counter.
+//      If it has reached zero then we destroy the underlying Rust struct.
+//
+//    * When `destroy` is called, we atomically flip the flag from false to true.
+//      If the flag was already true we silently fail.
+//      Otherwise we atomically decrement and check the counter.
+//      If it has reached zero then we destroy the underlying Rust struct.
+//
+// Astute readers may observe that this all sounds very similar to the way that Rust's `Arc<T>` works,
+// and indeed it is, with the addition of a flag to guard against multiple calls to `destroy`.
+//
+// The overall effect is that the underlying Rust struct is destroyed only when `destroy` has been
+// called *and* all in-flight method calls have completed, avoiding violating any of the expectations
+// of the underlying Rust code.
+//
+// In the future we may be able to replace some of this with automatic finalization logic, such as using
+// the new "Cleaner" functionaility in Java 9. The above scheme has been designed to work even if `destroy` is
+// invoked by garbage-collection machinery rather than by calling code (which by the way, it's apparently also
+// possible for the JVM to finalize an object while there is an in-flight call to one of its methods [1],
+// so there would still be some complexity here).
+//
+// Sigh...all of this for want of a robust finalization mechanism.
+//
+// [1] https://stackoverflow.com/questions/24376768/can-java-finalize-an-object-when-it-is-still-in-scope/24380219
+//
+abstract class FFIObject(
+    protected val pointer: Pointer
+): Disposable, AutoCloseable {
+
+    private val wasDestroyed = AtomicBoolean(false)
+    private val callCounter = AtomicLong(1)
+
+    open protected fun freeRustArcPtr() {
+        // To be overridden in subclasses.
+    }
+
+    override fun destroy() {
+        // Only allow a single call to this method.
+        // TODO: maybe we should log a warning if called more than once?
+        if (this.wasDestroyed.compareAndSet(false, true)) {
+            // This decrement always matches the initial count of 1 given at creation time.
+            if (this.callCounter.decrementAndGet() == 0L) {
+                this.freeRustArcPtr()
+            }
+        }
+    }
+
+    @Synchronized
+    override fun close() {
+        this.destroy()
+    }
+
+    internal inline fun <R> callWithPointer(block: (ptr: Pointer) -> R): R {
+        // Check and increment the call counter, to keep the object alive.
+        // This needs a compare-and-set retry loop in case of concurrent updates.
+        do {
+            val c = this.callCounter.get()
+            if (c == 0L) {
+                throw IllegalStateException("${this.javaClass.simpleName} object has already been destroyed")
+            }
+            if (c == Long.MAX_VALUE) {
+                throw IllegalStateException("${this.javaClass.simpleName} call counter would overflow")
+            }
+        } while (! this.callCounter.compareAndSet(c, c + 1L))
+        // Now we can safely do the method call without the pointer being freed concurrently.
+        try {
+            return block(this.pointer)
+        } finally {
+            // This decrement aways matches the increment we performed above.
+            if (this.callCounter.decrementAndGet() == 0L) {
+                this.freeRustArcPtr()
+            }
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectTemplate.kt
new file mode 100644
index 0000000000..5d654d9fae
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/ObjectTemplate.kt
@@ -0,0 +1,100 @@
+{%- let obj = ci.get_object_definition(name).unwrap() %}
+{%- if self.include_once_check("ObjectRuntime.kt") %}{% include "ObjectRuntime.kt" %}{% endif %}
+{{- self.add_import("java.util.concurrent.atomic.AtomicLong") }}
+{{- self.add_import("java.util.concurrent.atomic.AtomicBoolean") }}
+
+public interface {{ type_name }}Interface {
+    {% for meth in obj.methods() -%}
+    {%- match meth.throws_type() -%}
+    {%- when Some with (throwable) %}
+    @Throws({{ throwable|type_name }}::class)
+    {%- else -%}
+    {%- endmatch %}
+    fun {{ meth.name()|fn_name }}({% call kt::arg_list_decl(meth) %})
+    {%- match meth.return_type() -%}
+    {%- when Some with (return_type) %}: {{ return_type|type_name -}}
+    {%- else -%}
+    {%- endmatch %}
+    {% endfor %}
+}
+
+class {{ type_name }}(
+    pointer: Pointer
+) : FFIObject(pointer), {{ type_name }}Interface {
+
+    {%- match obj.primary_constructor() %}
+    {%- when Some with (cons) %}
+    constructor({% call kt::arg_list_decl(cons) -%}) :
+        this({% call kt::to_ffi_call(cons) %})
+    {%- when None %}
+    {%- endmatch %}
+
+    /**
+     * Disconnect the object from the underlying Rust object.
+     *
+     * It can be called more than once, but once called, interacting with the object
+     * causes an `IllegalStateException`.
+     *
+     * Clients **must** call this method once done with the object, or cause a memory leak.
+     */
+    override protected fun freeRustArcPtr() {
+        rustCall() { status ->
+            _UniFFILib.INSTANCE.{{ obj.ffi_object_free().name() }}(this.pointer, status)
+        }
+    }
+
+    {% for meth in obj.methods() -%}
+    {%- match meth.throws_type() -%}
+    {%- when Some with (throwable) %}
+    @Throws({{ throwable|type_name }}::class)
+    {%- else -%}
+    {%- endmatch %}
+    {%- match meth.return_type() -%}
+
+    {%- when Some with (return_type) -%}
+    override fun {{ meth.name()|fn_name }}({% call kt::arg_list_protocol(meth) %}): {{ return_type|type_name }} =
+        callWithPointer {
+            {%- call kt::to_ffi_call_with_prefix("it", meth) %}
+        }.let {
+            {{ return_type|lift_fn }}(it)
+        }
+
+    {%- when None -%}
+    override fun {{ meth.name()|fn_name }}({% call kt::arg_list_protocol(meth) %}) =
+        callWithPointer {
+            {%- call kt::to_ffi_call_with_prefix("it", meth) %}
+        }
+    {% endmatch %}
+    {% endfor %}
+
+    {% if !obj.alternate_constructors().is_empty() -%}
+    companion object {
+        {% for cons in obj.alternate_constructors() -%}
+        fun {{ cons.name()|fn_name }}({% call kt::arg_list_decl(cons) %}): {{ type_name }} =
+            {{ type_name }}({% call kt::to_ffi_call(cons) %})
+        {% endfor %}
+    }
+    {% endif %}
+}
+
+public object {{ obj|ffi_converter_name }}: FfiConverter<{{ type_name }}, Pointer> {
+    override fun lower(value: {{ type_name }}): Pointer = value.callWithPointer { it }
+
+    override fun lift(value: Pointer): {{ type_name }} {
+        return {{ type_name }}(value)
+    }
+
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        // The Rust code always writes pointers as 8 bytes, and will
+        // fail to compile if they don't fit.
+        return lift(Pointer(buf.getLong()))
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = 8
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        // The Rust code always expects pointers written as 8 bytes,
+        // and will fail to compile if they don't fit.
+        buf.putLong(Pointer.nativeValue(lower(value)))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/OptionalTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/OptionalTemplate.kt
new file mode 100644
index 0000000000..6830b51863
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/OptionalTemplate.kt
@@ -0,0 +1,27 @@
+{%- let inner_type_name = inner_type|type_name %}
+
+public object {{ ffi_converter_name }}: FfiConverterRustBuffer<{{ inner_type_name }}?> {
+    override fun read(buf: ByteBuffer): {{ inner_type_name }}? {
+        if (buf.get().toInt() == 0) {
+            return null
+        }
+        return {{ inner_type|read_fn }}(buf)
+    }
+
+    override fun allocationSize(value: {{ inner_type_name }}?): Int {
+        if (value == null) {
+            return 1
+        } else {
+            return 1 + {{ inner_type|allocation_size_fn }}(value)
+        }
+    }
+
+    override fun write(value: {{ inner_type_name }}?, buf: ByteBuffer) {
+        if (value == null) {
+            buf.put(0)
+        } else {
+            buf.put(1)
+            {{ inner_type|write_fn }}(value, buf)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RecordTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RecordTemplate.kt
new file mode 100644
index 0000000000..a17f4d42eb
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RecordTemplate.kt
@@ -0,0 +1,41 @@
+{%- let rec = ci.get_record_definition(name).unwrap() %}
+
+data class {{ type_name }} (
+    {%- for field in rec.fields() %}
+    var {{ field.name()|var_name }}: {{ field|type_name -}}
+    {%- match field.default_value() %}
+        {%- when Some with(literal) %} = {{ literal|render_literal(field) }}
+        {%- else %}
+    {%- endmatch -%}
+    {% if !loop.last %}, {% endif %}
+    {%- endfor %}
+) {% if contains_object_references %}: Disposable {% endif %}{
+    {% if contains_object_references %}
+    @Suppress("UNNECESSARY_SAFE_CALL") // codegen is much simpler if we unconditionally emit safe calls here
+    override fun destroy() {
+        {% call kt::destroy_fields(rec) %}
+    }
+    {% endif %}
+}
+
+public object {{ rec|ffi_converter_name }}: FfiConverterRustBuffer<{{ type_name }}> {
+    override fun read(buf: ByteBuffer): {{ type_name }} {
+        return {{ type_name }}(
+        {%- for field in rec.fields() %}
+            {{ field|read_fn }}(buf),
+        {%- endfor %}
+        )
+    }
+
+    override fun allocationSize(value: {{ type_name }}) = (
+        {%- for field in rec.fields() %}
+            {{ field|allocation_size_fn }}(value.{{ field.name()|var_name }}){% if !loop.last %} +{% endif%}
+        {%- endfor %}
+    )
+
+    override fun write(value: {{ type_name }}, buf: ByteBuffer) {
+        {%- for field in rec.fields() %}
+            {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+        {%- endfor %}
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RustBufferTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RustBufferTemplate.kt
new file mode 100644
index 0000000000..6cc218e940
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/RustBufferTemplate.kt
@@ -0,0 +1,66 @@
+// This is a helper for safely working with byte buffers returned from the Rust code.
+// A rust-owned buffer is represented by its capacity, its current length, and a
+// pointer to the underlying data.
+
+@Structure.FieldOrder("capacity", "len", "data")
+open class RustBuffer : Structure() {
+    @JvmField var capacity: Int = 0
+    @JvmField var len: Int = 0
+    @JvmField var data: Pointer? = null
+
+    class ByValue : RustBuffer(), Structure.ByValue
+    class ByReference : RustBuffer(), Structure.ByReference
+
+    companion object {
+        internal fun alloc(size: Int = 0) = rustCall() { status ->
+            _UniFFILib.INSTANCE.{{ ci.ffi_rustbuffer_alloc().name() }}(size, status).also {
+                if(it.data == null) {
+                   throw RuntimeException("RustBuffer.alloc() returned null data pointer (size=${size})")
+               }
+            }
+        }
+
+        internal fun free(buf: RustBuffer.ByValue) = rustCall() { status ->
+            _UniFFILib.INSTANCE.{{ ci.ffi_rustbuffer_free().name() }}(buf, status)
+        }
+    }
+
+    @Suppress("TooGenericExceptionThrown")
+    fun asByteBuffer() =
+        this.data?.getByteBuffer(0, this.len.toLong())?.also {
+            it.order(ByteOrder.BIG_ENDIAN)
+        }
+}
+
+/**
+ * The equivalent of the `*mut RustBuffer` type.
+ * Required for callbacks taking in an out pointer.
+ *
+ * Size is the sum of all values in the struct.
+ */
+class RustBufferByReference : ByReference(16) {
+    /**
+     * Set the pointed-to `RustBuffer` to the given value.
+     */
+    fun setValue(value: RustBuffer.ByValue) {
+        // NOTE: The offsets are as they are in the C-like struct.
+        val pointer = getPointer()
+        pointer.setInt(0, value.capacity)
+        pointer.setInt(4, value.len)
+        pointer.setPointer(8, value.data)
+    }
+}
+
+// This is a helper for safely passing byte references into the rust code.
+// It's not actually used at the moment, because there aren't many things that you
+// can take a direct pointer to in the JVM, and if we're going to copy something
+// then we might as well copy it into a `RustBuffer`. But it's here for API
+// completeness.
+
+@Structure.FieldOrder("len", "data")
+open class ForeignBytes : Structure() {
+    @JvmField var len: Int = 0
+    @JvmField var data: Pointer? = null
+
+    class ByValue : ForeignBytes(), Structure.ByValue
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/SequenceTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/SequenceTemplate.kt
new file mode 100644
index 0000000000..b5c699ba3b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/SequenceTemplate.kt
@@ -0,0 +1,23 @@
+{%- let inner_type_name = inner_type|type_name %}
+
+public object {{ ffi_converter_name }}: FfiConverterRustBuffer<List<{{ inner_type_name }}>> {
+    override fun read(buf: ByteBuffer): List<{{ inner_type_name }}> {
+        val len = buf.getInt()
+        return List<{{ inner_type_name }}>(len) {
+            {{ inner_type|read_fn }}(buf)
+        }
+    }
+
+    override fun allocationSize(value: List<{{ inner_type_name }}>): Int {
+        val sizeForLength = 4
+        val sizeForItems = value.map { {{ inner_type|allocation_size_fn }}(it) }.sum()
+        return sizeForLength + sizeForItems
+    }
+
+    override fun write(value: List<{{ inner_type_name }}>, buf: ByteBuffer) {
+        buf.putInt(value.size)
+        value.forEach {
+            {{ inner_type|write_fn }}(it, buf)
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/StringHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/StringHelper.kt
new file mode 100644
index 0000000000..d3443215c1
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/StringHelper.kt
@@ -0,0 +1,45 @@
+public object FfiConverterString: FfiConverter<String, RustBuffer.ByValue> {
+    // Note: we don't inherit from FfiConverterRustBuffer, because we use a
+    // special encoding when lowering/lifting.  We can use `RustBuffer.len` to
+    // store our length and avoid writing it out to the buffer.
+    override fun lift(value: RustBuffer.ByValue): String {
+        try {
+            val byteArr = ByteArray(value.len)
+            value.asByteBuffer()!!.get(byteArr)
+            return byteArr.toString(Charsets.UTF_8)
+        } finally {
+            RustBuffer.free(value)
+        }
+    }
+
+    override fun read(buf: ByteBuffer): String {
+        val len = buf.getInt()
+        val byteArr = ByteArray(len)
+        buf.get(byteArr)
+        return byteArr.toString(Charsets.UTF_8)
+    }
+
+    override fun lower(value: String): RustBuffer.ByValue {
+        val byteArr = value.toByteArray(Charsets.UTF_8)
+        // Ideally we'd pass these bytes to `ffi_bytebuffer_from_bytes`, but doing so would require us
+        // to copy them into a JNA `Memory`. So we might as well directly copy them into a `RustBuffer`.
+        val rbuf = RustBuffer.alloc(byteArr.size)
+        rbuf.asByteBuffer()!!.put(byteArr)
+        return rbuf
+    }
+
+    // We aren't sure exactly how many bytes our string will be once it's UTF-8
+    // encoded.  Allocate 3 bytes per unicode codepoint which will always be
+    // enough.
+    override fun allocationSize(value: String): Int {
+        val sizeForLength = 4
+        val sizeForString = value.length * 3
+        return sizeForLength + sizeForString
+    }
+
+    override fun write(value: String, buf: ByteBuffer) {
+        val byteArr = value.toByteArray(Charsets.UTF_8)
+        buf.putInt(byteArr.size)
+        buf.put(byteArr)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TimestampHelper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TimestampHelper.kt
new file mode 100644
index 0000000000..21069d7ce8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TimestampHelper.kt
@@ -0,0 +1,38 @@
+public object FfiConverterTimestamp: FfiConverterRustBuffer<java.time.Instant> {
+    override fun read(buf: ByteBuffer): java.time.Instant {
+        val seconds = buf.getLong()
+        // Type mismatch (should be u32) but we check for overflow/underflow below
+        val nanoseconds = buf.getInt().toLong()
+        if (nanoseconds < 0) {
+            throw java.time.DateTimeException("Instant nanoseconds exceed minimum or maximum supported by uniffi")
+        }
+        if (seconds >= 0) {
+            return java.time.Instant.EPOCH.plus(java.time.Duration.ofSeconds(seconds, nanoseconds))
+        } else {
+            return java.time.Instant.EPOCH.minus(java.time.Duration.ofSeconds(-seconds, nanoseconds))
+        }
+    }
+
+    // 8 bytes for seconds, 4 bytes for nanoseconds
+    override fun allocationSize(value: java.time.Instant) = 12
+
+    override fun write(value: java.time.Instant, buf: ByteBuffer) {
+        var epochOffset = java.time.Duration.between(java.time.Instant.EPOCH, value)
+
+        var sign = 1
+        if (epochOffset.isNegative()) {
+            sign = -1
+            epochOffset = epochOffset.negated()
+        }
+
+        if (epochOffset.nano < 0) {
+            // Java docs provide guarantee that nano will always be positive, so this should be impossible
+            // See: https://docs.oracle.com/javase/8/docs/api/java/time/Instant.html
+            throw IllegalArgumentException("Invalid timestamp, nano value must be non-negative")
+        }
+
+        buf.putLong(sign * epochOffset.seconds)
+        // Type mismatch (should be u32) but since values will always be between 0 and 999,999,999 it should be OK
+        buf.putInt(epochOffset.nano)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TopLevelFunctionTemplate.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TopLevelFunctionTemplate.kt
new file mode 100644
index 0000000000..180a64066a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/TopLevelFunctionTemplate.kt
@@ -0,0 +1,17 @@
+{%- match func.throws_type() -%}
+{%- when Some with (throwable) %}
+@Throws({{ throwable|type_name }}::class)
+{%- else -%}
+{%- endmatch %}
+{%- match func.return_type() -%}
+{%- when Some with (return_type) %}
+
+fun {{ func.name()|fn_name }}({%- call kt::arg_list_decl(func) -%}): {{ return_type|type_name }} {
+    return {{ return_type|lift_fn }}({% call kt::to_ffi_call(func) %})
+}
+
+{% when None %}
+
+fun {{ func.name()|fn_name }}({% call kt::arg_list_decl(func) %}) =
+    {% call kt::to_ffi_call(func) %}
+{% endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Types.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Types.kt
new file mode 100644
index 0000000000..6379971b76
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/Types.kt
@@ -0,0 +1,94 @@
+{%- import "macros.kt" as kt %}
+
+{%- for type_ in ci.iter_types() %}
+{%- let type_name = type_|type_name %}
+{%- let ffi_converter_name = type_|ffi_converter_name %}
+{%- let canonical_type_name = type_|canonical_name %}
+{%- let contains_object_references = ci.item_contains_object_references(type_) %}
+
+{#
+ # Map `Type` instances to an include statement for that type.
+ #
+ # There is a companion match in `KotlinCodeOracle::create_code_type()` which performs a similar function for the
+ # Rust code.
+ #
+ #   - When adding additional types here, make sure to also add a match arm to that function.
+ #   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+ #}
+{%- match type_ %}
+
+{%- when Type::Boolean %}
+{%- include "BooleanHelper.kt" %}
+
+{%- when Type::Int8 %}
+{%- include "Int8Helper.kt" %}
+
+{%- when Type::Int16 %}
+{%- include "Int16Helper.kt" %}
+
+{%- when Type::Int32 %}
+{%- include "Int32Helper.kt" %}
+
+{%- when Type::Int64 %}
+{%- include "Int64Helper.kt" %}
+
+{%- when Type::UInt8 %}
+{%- include "UInt8Helper.kt" %}
+
+{%- when Type::UInt16 %}
+{%- include "UInt16Helper.kt" %}
+
+{%- when Type::UInt32 %}
+{%- include "UInt32Helper.kt" %}
+
+{%- when Type::UInt64 %}
+{%- include "UInt64Helper.kt" %}
+
+{%- when Type::Float32 %}
+{%- include "Float32Helper.kt" %}
+
+{%- when Type::Float64 %}
+{%- include "Float64Helper.kt" %}
+
+{%- when Type::String %}
+{%- include "StringHelper.kt" %}
+
+{%- when Type::Enum(name) %}
+{% include "EnumTemplate.kt" %}
+
+{%- when Type::Error(name) %}
+{% include "ErrorTemplate.kt" %}
+
+{%- when Type::Object(name) %}
+{% include "ObjectTemplate.kt" %}
+
+{%- when Type::Record(name) %}
+{% include "RecordTemplate.kt" %}
+
+{%- when Type::Optional(inner_type) %}
+{% include "OptionalTemplate.kt" %}
+
+{%- when Type::Sequence(inner_type) %}
+{% include "SequenceTemplate.kt" %}
+
+{%- when Type::Map(key_type, value_type) %}
+{% include "MapTemplate.kt" %}
+
+{%- when Type::CallbackInterface(name) %}
+{% include "CallbackInterfaceTemplate.kt" %}
+
+{%- when Type::Timestamp %}
+{% include "TimestampHelper.kt" %}
+
+{%- when Type::Duration %}
+{% include "DurationHelper.kt" %}
+
+{%- when Type::Custom { name, builtin } %}
+{% include "CustomTypeTemplate.kt" %}
+
+{%- when Type::External { crate_name, name } %}
+{% include "ExternalTypeTemplate.kt" %}
+
+{%- else %}
+{%- endmatch %}
+{%- endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt16Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt16Helper.kt
new file mode 100644
index 0000000000..279a8fa91b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt16Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterUShort: FfiConverter<UShort, Short> {
+    override fun lift(value: Short): UShort {
+        return value.toUShort()
+    }
+
+    override fun read(buf: ByteBuffer): UShort {
+        return lift(buf.getShort())
+    }
+
+    override fun lower(value: UShort): Short {
+        return value.toShort()
+    }
+
+    override fun allocationSize(value: UShort) = 2
+
+    override fun write(value: UShort, buf: ByteBuffer) {
+        buf.putShort(value.toShort())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt32Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt32Helper.kt
new file mode 100644
index 0000000000..da7b5b28d6
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt32Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterUInt: FfiConverter<UInt, Int> {
+    override fun lift(value: Int): UInt {
+        return value.toUInt()
+    }
+
+    override fun read(buf: ByteBuffer): UInt {
+        return lift(buf.getInt())
+    }
+
+    override fun lower(value: UInt): Int {
+        return value.toInt()
+    }
+
+    override fun allocationSize(value: UInt) = 4
+
+    override fun write(value: UInt, buf: ByteBuffer) {
+        buf.putInt(value.toInt())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt64Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt64Helper.kt
new file mode 100644
index 0000000000..44d27ad36b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt64Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterULong: FfiConverter<ULong, Long> {
+    override fun lift(value: Long): ULong {
+        return value.toULong()
+    }
+
+    override fun read(buf: ByteBuffer): ULong {
+        return lift(buf.getLong())
+    }
+
+    override fun lower(value: ULong): Long {
+        return value.toLong()
+    }
+
+    override fun allocationSize(value: ULong) = 8
+
+    override fun write(value: ULong, buf: ByteBuffer) {
+        buf.putLong(value.toLong())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt8Helper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt8Helper.kt
new file mode 100644
index 0000000000..b6d176603e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/UInt8Helper.kt
@@ -0,0 +1,19 @@
+public object FfiConverterUByte: FfiConverter<UByte, Byte> {
+    override fun lift(value: Byte): UByte {
+        return value.toUByte()
+    }
+
+    override fun read(buf: ByteBuffer): UByte {
+        return lift(buf.get())
+    }
+
+    override fun lower(value: UByte): Byte {
+        return value.toByte()
+    }
+
+    override fun allocationSize(value: UByte) = 1
+
+    override fun write(value: UByte, buf: ByteBuffer) {
+        buf.put(value.toByte())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/macros.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/macros.kt
new file mode 100644
index 0000000000..2888b23873
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/macros.kt
@@ -0,0 +1,82 @@
+{#
+// Template to call into rust. Used in several places.
+// Variable names in `arg_list_decl` should match up with arg lists
+// passed to rust via `_arg_list_ffi_call`
+#}
+
+{%- macro to_ffi_call(func) -%}
+    {%- match func.throws_type() %}
+    {%- when Some with (e) %}
+    rustCallWithError({{ e|type_name}})
+    {%- else %}
+    rustCall()
+    {%- endmatch %} { _status ->
+    _UniFFILib.INSTANCE.{{ func.ffi_func().name() }}({% call _arg_list_ffi_call(func) -%}{% if func.arguments().len() > 0 %},{% endif %} _status)
+}
+{%- endmacro -%}
+
+{%- macro to_ffi_call_with_prefix(prefix, func) %}
+    {%- match func.throws_type() %}
+    {%- when Some with (e) %}
+    rustCallWithError({{ e|type_name}})
+    {%- else %}
+    rustCall()
+    {%- endmatch %} { _status ->
+    _UniFFILib.INSTANCE.{{ func.ffi_func().name() }}(
+        {{- prefix }}, {% call _arg_list_ffi_call(func) %}{% if func.arguments().len() > 0 %}, {% endif %} _status)
+}
+{%- endmacro %}
+
+{%- macro _arg_list_ffi_call(func) %}
+    {%- for arg in func.arguments() %}
+        {{- arg|lower_fn }}({{ arg.name()|var_name }})
+        {%- if !loop.last %}, {% endif %}
+    {%- endfor %}
+{%- endmacro -%}
+
+{#-
+// Arglist as used in kotlin declarations of methods, functions and constructors.
+// Note the var_name and type_name filters.
+-#}
+
+{% macro arg_list_decl(func) %}
+    {%- for arg in func.arguments() -%}
+        {{ arg.name()|var_name }}: {{ arg|type_name -}}
+        {%- match arg.default_value() %}
+        {%- when Some with(literal) %} = {{ literal|render_literal(arg) }}
+        {%- else %}
+        {%- endmatch %}
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+
+{% macro arg_list_protocol(func) %}
+    {%- for arg in func.arguments() -%}
+        {{ arg.name()|var_name }}: {{ arg|type_name -}}
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+{#-
+// Arglist as used in the _UniFFILib function declations.
+// Note unfiltered name but ffi_type_name filters.
+-#}
+{%- macro arg_list_ffi_decl(func) %}
+    {%- for arg in func.arguments() %}
+        {{- arg.name()|var_name }}: {{ arg.type_().borrow()|ffi_type_name -}},
+    {%- endfor %}
+    _uniffi_out_err: RustCallStatus
+{%- endmacro -%}
+
+// Macro for destroying fields
+{%- macro destroy_fields(member) %}
+    Disposable.destroy(
+    {%- for field in member.fields() %}
+        this.{{ field.name()|var_name }}{%- if !loop.last %}, {% endif -%}
+    {% endfor -%})
+{%- endmacro -%}
+
+{%- macro ffi_function_definition(func) %}
+fun {{ func.name()|fn_name }}(
+    {%- call arg_list_ffi_decl(func) %}
+){%- match func.return_type() -%}{%- when Some with (type_) %}: {{ type_|ffi_type_name }}{% when None %}: Unit{% endmatch %}
+{% endmacro %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/wrapper.kt b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/wrapper.kt
new file mode 100644
index 0000000000..9cb104292c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/kotlin/templates/wrapper.kt
@@ -0,0 +1,48 @@
+// This file was autogenerated by some hot garbage in the `uniffi` crate.
+// Trust me, you don't want to mess with it!
+
+@file:Suppress("NAME_SHADOWING")
+
+package {{ config.package_name() }};
+
+// Common helper code.
+//
+// Ideally this would live in a separate .kt file where it can be unittested etc
+// in isolation, and perhaps even published as a re-useable package.
+//
+// However, it's important that the detils of how this helper code works (e.g. the
+// way that different builtin types are passed across the FFI) exactly match what's
+// expected by the Rust code on the other side of the interface. In practice right
+// now that means coming from the exact some version of `uniffi` that was used to
+// compile the Rust component. The easiest way to ensure this is to bundle the Kotlin
+// helpers directly inline like we're doing here.
+
+import com.sun.jna.Library
+import com.sun.jna.Native
+import com.sun.jna.Pointer
+import com.sun.jna.Structure
+import com.sun.jna.ptr.ByReference
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+
+{%- for imported_class in self.imports() %}
+import {{ imported_class }}
+{%- endfor %}
+
+{% include "RustBufferTemplate.kt" %}
+{% include "FfiConverterTemplate.kt" %}
+{% include "Helpers.kt" %}
+
+// Contains loading, initialization code,
+// and the FFI Function declarations in a com.sun.jna.Library.
+{% include "NamespaceLibraryTemplate.kt" %}
+
+// Public interface members begin here.
+{{ type_helper_code }}
+
+{%- for func in ci.function_definitions() %}
+{%- include "TopLevelFunctionTemplate.kt" %}
+{%- endfor %}
+
+
+{% import "macros.kt" as kt %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/mod.rs
new file mode 100644
index 0000000000..5aca641340
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/mod.rs
@@ -0,0 +1,158 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Generate foreign language bindings for a uniffi component.
+//!
+//! This module contains all the code for generating foreign language bindings,
+//! along with some helpers for executing foreign language scripts or tests.
+
+use anyhow::{bail, Result};
+use camino::Utf8Path;
+use serde::{Deserialize, Serialize};
+
+use crate::interface::ComponentInterface;
+use crate::MergeWith;
+
+pub mod kotlin;
+pub mod python;
+pub mod ruby;
+pub mod swift;
+
+/// Enumeration of all foreign language targets currently supported by this crate.
+///
+/// The functions in this module will delegate to a language-specific backend based
+/// on the provided `TargetLanguage`. For convenience of calling code we also provide
+/// a few `TryFrom` implementations to help guess the correct target language from
+/// e.g. a file extension of command-line argument.
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+pub enum TargetLanguage {
+    Kotlin,
+    Swift,
+    Python,
+    Ruby,
+}
+
+impl TryFrom<&str> for TargetLanguage {
+    type Error = anyhow::Error;
+    fn try_from(value: &str) -> Result<Self> {
+        Ok(match value.to_ascii_lowercase().as_str() {
+            "kotlin" | "kt" | "kts" => TargetLanguage::Kotlin,
+            "swift" => TargetLanguage::Swift,
+            "python" | "py" => TargetLanguage::Python,
+            "ruby" | "rb" => TargetLanguage::Ruby,
+            _ => bail!("Unknown or unsupported target language: \"{}\"", value),
+        })
+    }
+}
+
+impl TryFrom<&std::ffi::OsStr> for TargetLanguage {
+    type Error = anyhow::Error;
+    fn try_from(value: &std::ffi::OsStr) -> Result<Self> {
+        match value.to_str() {
+            None => bail!("Unreadable target language"),
+            Some(s) => s.try_into(),
+        }
+    }
+}
+
+impl TryFrom<String> for TargetLanguage {
+    type Error = anyhow::Error;
+    fn try_from(value: String) -> Result<Self> {
+        TryFrom::try_from(value.as_str())
+    }
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct Config {
+    #[serde(default)]
+    kotlin: kotlin::Config,
+    #[serde(default)]
+    swift: swift::Config,
+    #[serde(default)]
+    python: python::Config,
+    #[serde(default)]
+    ruby: ruby::Config,
+}
+
+impl From<&ComponentInterface> for Config {
+    fn from(ci: &ComponentInterface) -> Self {
+        Config {
+            kotlin: ci.into(),
+            swift: ci.into(),
+            python: ci.into(),
+            ruby: ci.into(),
+        }
+    }
+}
+
+impl MergeWith for Config {
+    fn merge_with(&self, other: &Self) -> Self {
+        Config {
+            kotlin: self.kotlin.merge_with(&other.kotlin),
+            swift: self.swift.merge_with(&other.swift),
+            python: self.python.merge_with(&other.python),
+            ruby: self.ruby.merge_with(&other.ruby),
+        }
+    }
+}
+
+/// Generate foreign language bindings from a compiled `uniffi` library.
+pub fn write_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+    language: TargetLanguage,
+    try_format_code: bool,
+) -> Result<()> {
+    match language {
+        TargetLanguage::Kotlin => {
+            kotlin::write_bindings(&config.kotlin, ci, out_dir, try_format_code)?
+        }
+        TargetLanguage::Swift => {
+            swift::write_bindings(&config.swift, ci, out_dir, try_format_code)?
+        }
+        TargetLanguage::Python => {
+            python::write_bindings(&config.python, ci, out_dir, try_format_code)?
+        }
+        TargetLanguage::Ruby => ruby::write_bindings(&config.ruby, ci, out_dir, try_format_code)?,
+    }
+    Ok(())
+}
+
+/// Compile generated foreign language bindings so they're ready for use.
+///
+/// Note: This function is only used for compiling the unit tests. See #1169 for plans to refactor
+/// it.
+pub fn compile_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+    language: TargetLanguage,
+) -> Result<()> {
+    match language {
+        TargetLanguage::Kotlin => kotlin::compile_bindings(&config.kotlin, ci, out_dir)?,
+        TargetLanguage::Swift => swift::compile_bindings(&config.swift, ci, out_dir)?,
+        TargetLanguage::Python => (),
+        TargetLanguage::Ruby => (),
+    }
+    Ok(())
+}
+
+/// Execute the given script via foreign language interpreter/shell.
+///
+/// Note: This function is only used for compiling the unit tests. See #1169 for plans to refactor
+/// it.
+pub fn run_script(
+    out_dir: &Utf8Path,
+    script_file: &Utf8Path,
+    language: TargetLanguage,
+) -> Result<()> {
+    match language {
+        TargetLanguage::Kotlin => kotlin::run_script(out_dir, script_file)?,
+        TargetLanguage::Swift => swift::run_script(out_dir, script_file)?,
+        TargetLanguage::Python => python::run_script(out_dir, script_file)?,
+        TargetLanguage::Ruby => ruby::run_script(out_dir, script_file)?,
+    }
+    Ok(())
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/callback_interface.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/callback_interface.rs
new file mode 100644
index 0000000000..9359fbaeae
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/callback_interface.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct CallbackInterfaceCodeType {
+    id: String,
+}
+
+impl CallbackInterfaceCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for CallbackInterfaceCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("CallbackInterface{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+
+    fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+        nm.to_string()
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/compounds.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/compounds.rs
new file mode 100644
index 0000000000..80b1da040d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/compounds.rs
@@ -0,0 +1,122 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal, TypeIdentifier};
+
+pub struct OptionalCodeType {
+    inner: TypeIdentifier,
+}
+
+impl OptionalCodeType {
+    pub fn new(inner: TypeIdentifier) -> Self {
+        Self { inner }
+    }
+}
+
+impl CodeType for OptionalCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.find(&self.inner).type_label(oracle)
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Optional{}",
+            oracle.find(&self.inner).canonical_name(oracle),
+        )
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        match literal {
+            Literal::Null => "None".into(),
+            _ => oracle.find(&self.inner).literal(oracle, literal),
+        }
+    }
+
+    fn coerce(&self, oracle: &dyn CodeOracle, nm: &str) -> String {
+        format!(
+            "(None if {} is None else {})",
+            nm,
+            oracle.find(&self.inner).coerce(oracle, nm)
+        )
+    }
+}
+
+pub struct SequenceCodeType {
+    inner: TypeIdentifier,
+}
+
+impl SequenceCodeType {
+    pub fn new(inner: TypeIdentifier) -> Self {
+        Self { inner }
+    }
+}
+
+impl CodeType for SequenceCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        "list".to_string()
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Sequence{}",
+            oracle.find(&self.inner).canonical_name(oracle),
+        )
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        match literal {
+            Literal::EmptySequence => "[]".into(),
+            _ => unimplemented!(),
+        }
+    }
+
+    fn coerce(&self, oracle: &dyn CodeOracle, nm: &str) -> String {
+        format!(
+            "list({} for x in {})",
+            oracle.find(&self.inner).coerce(oracle, "x"),
+            nm
+        )
+    }
+}
+
+pub struct MapCodeType {
+    key: TypeIdentifier,
+    value: TypeIdentifier,
+}
+
+impl MapCodeType {
+    pub fn new(key: TypeIdentifier, value: TypeIdentifier) -> Self {
+        Self { key, value }
+    }
+}
+
+impl CodeType for MapCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        "dict".to_string()
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Map{}{}",
+            oracle.find(&self.key).canonical_name(oracle),
+            oracle.find(&self.value).canonical_name(oracle),
+        )
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        match literal {
+            Literal::EmptyMap => "{}".into(),
+            _ => unimplemented!(),
+        }
+    }
+
+    fn coerce(&self, oracle: &dyn CodeOracle, nm: &str) -> String {
+        format!(
+            "dict(({}, {}) for (k, v) in {}.items())",
+            self.key.coerce(oracle, "k"),
+            self.value.coerce(oracle, "v"),
+            nm
+        )
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/custom.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/custom.rs
new file mode 100644
index 0000000000..d53a946947
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/custom.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct CustomCodeType {
+    name: String,
+}
+
+impl CustomCodeType {
+    pub fn new(name: String) -> Self {
+        Self { name }
+    }
+}
+
+impl CodeType for CustomCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        self.name.clone()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.name)
+    }
+
+    fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+        nm.to_string()
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/enum_.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/enum_.rs
new file mode 100644
index 0000000000..9a86076770
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/enum_.rs
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct EnumCodeType {
+    id: String,
+}
+
+impl EnumCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for EnumCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        if let Literal::Enum(v, _) = literal {
+            format!(
+                "{}.{}",
+                self.type_label(oracle),
+                oracle.enum_variant_name(v)
+            )
+        } else {
+            unreachable!();
+        }
+    }
+
+    fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+        nm.to_string()
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/error.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/error.rs
new file mode 100644
index 0000000000..f1567281f2
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/error.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ErrorCodeType {
+    id: String,
+}
+
+impl ErrorCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ErrorCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+
+    fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+        nm.to_string()
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/external.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/external.rs
new file mode 100644
index 0000000000..50cafabbbc
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/external.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct ExternalCodeType {
+    name: String,
+}
+
+impl ExternalCodeType {
+    pub fn new(name: String) -> Self {
+        Self { name }
+    }
+}
+
+impl CodeType for ExternalCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        self.name.clone()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.name)
+    }
+
+    fn coerce(&self, _oracle: &dyn CodeOracle, _nm: &str) -> String {
+        panic!("should not be necessary to coerce External types");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/miscellany.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/miscellany.rs
new file mode 100644
index 0000000000..c885428bc3
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/miscellany.rs
@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+use paste::paste;
+
+macro_rules! impl_code_type_for_miscellany {
+    ($T:ty, $canonical_name:literal) => {
+        paste! {
+            pub struct $T;
+
+            impl CodeType for $T  {
+                fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+                    format!("{}", $canonical_name)
+                }
+
+                fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+                    format!("{}", $canonical_name)
+                }
+
+                fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+                    unreachable!()
+                }
+
+                fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+                    nm.to_string()
+                }
+            }
+        }
+    };
+}
+
+impl_code_type_for_miscellany!(TimestampCodeType, "Timestamp");
+
+impl_code_type_for_miscellany!(DurationCodeType, "Duration");
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/mod.rs
new file mode 100644
index 0000000000..3bd879c068
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/mod.rs
@@ -0,0 +1,386 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use anyhow::{Context, Result};
+use askama::Template;
+use heck::{ToShoutySnakeCase, ToSnakeCase, ToUpperCamelCase};
+use once_cell::sync::Lazy;
+use serde::{Deserialize, Serialize};
+use std::borrow::Borrow;
+use std::cell::RefCell;
+use std::collections::{BTreeSet, HashMap, HashSet};
+
+use crate::backend::{CodeOracle, CodeType, TemplateExpression, TypeIdentifier};
+use crate::interface::*;
+use crate::MergeWith;
+
+mod callback_interface;
+mod compounds;
+mod custom;
+mod enum_;
+mod error;
+mod external;
+mod miscellany;
+mod object;
+mod primitives;
+mod record;
+
+// Taken from Python's `keyword.py` module.
+static KEYWORDS: Lazy<HashSet<String>> = Lazy::new(|| {
+    let kwlist = vec![
+        "False",
+        "None",
+        "True",
+        "__peg_parser__",
+        "and",
+        "as",
+        "assert",
+        "async",
+        "await",
+        "break",
+        "class",
+        "continue",
+        "def",
+        "del",
+        "elif",
+        "else",
+        "except",
+        "finally",
+        "for",
+        "from",
+        "global",
+        "if",
+        "import",
+        "in",
+        "is",
+        "lambda",
+        "nonlocal",
+        "not",
+        "or",
+        "pass",
+        "raise",
+        "return",
+        "try",
+        "while",
+        "with",
+        "yield",
+    ];
+    HashSet::from_iter(kwlist.into_iter().map(|s| s.to_string()))
+});
+
+// Config options to customize the generated python.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct Config {
+    cdylib_name: Option<String>,
+    #[serde(default)]
+    custom_types: HashMap<String, CustomTypeConfig>,
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct CustomTypeConfig {
+    // This `CustomTypeConfig` doesn't have a `type_name` like the others -- which is why we have
+    // separate structs rather than a shared one.
+    imports: Option<Vec<String>>,
+    into_custom: TemplateExpression,
+    from_custom: TemplateExpression,
+}
+
+impl Config {
+    pub fn cdylib_name(&self) -> String {
+        if let Some(cdylib_name) = &self.cdylib_name {
+            cdylib_name.clone()
+        } else {
+            "uniffi".into()
+        }
+    }
+}
+
+impl From<&ComponentInterface> for Config {
+    fn from(ci: &ComponentInterface) -> Self {
+        Config {
+            cdylib_name: Some(format!("uniffi_{}", ci.namespace())),
+            custom_types: HashMap::new(),
+        }
+    }
+}
+
+impl MergeWith for Config {
+    fn merge_with(&self, other: &Self) -> Self {
+        Config {
+            cdylib_name: self.cdylib_name.merge_with(&other.cdylib_name),
+            custom_types: self.custom_types.merge_with(&other.custom_types),
+        }
+    }
+}
+
+// Generate python bindings for the given ComponentInterface, as a string.
+pub fn generate_python_bindings(config: &Config, ci: &ComponentInterface) -> Result<String> {
+    PythonWrapper::new(config.clone(), ci)
+        .render()
+        .context("failed to render python bindings")
+}
+
+/// Renders Python helper code for all types
+///
+/// This template is a bit different than others in that it stores internal state from the render
+/// process.  Make sure to only call `render()` once.
+#[derive(Template)]
+#[template(syntax = "py", escape = "none", path = "Types.py")]
+pub struct TypeRenderer<'a> {
+    python_config: &'a Config,
+    ci: &'a ComponentInterface,
+    // Track included modules for the `include_once()` macro
+    include_once_names: RefCell<HashSet<String>>,
+    // Track imports added with the `add_import()` macro
+    imports: RefCell<BTreeSet<String>>,
+}
+
+impl<'a> TypeRenderer<'a> {
+    fn new(python_config: &'a Config, ci: &'a ComponentInterface) -> Self {
+        Self {
+            python_config,
+            ci,
+            include_once_names: RefCell::new(HashSet::new()),
+            imports: RefCell::new(BTreeSet::new()),
+        }
+    }
+
+    // The following methods are used by the `Types.py` macros.
+
+    // Helper for the including a template, but only once.
+    //
+    // The first time this is called with a name it will return true, indicating that we should
+    // include the template.  Subsequent calls will return false.
+    fn include_once_check(&self, name: &str) -> bool {
+        self.include_once_names
+            .borrow_mut()
+            .insert(name.to_string())
+    }
+
+    // Helper to add an import statement
+    //
+    // Call this inside your template to cause an import statement to be added at the top of the
+    // file.  Imports will be sorted and de-deuped.
+    //
+    // Returns an empty string so that it can be used inside an askama `{{ }}` block.
+    fn add_import(&self, name: &str) -> &str {
+        self.imports.borrow_mut().insert(name.to_owned());
+        ""
+    }
+}
+
+#[derive(Template)]
+#[template(syntax = "py", escape = "none", path = "wrapper.py")]
+pub struct PythonWrapper<'a> {
+    ci: &'a ComponentInterface,
+    config: Config,
+    type_helper_code: String,
+    type_imports: BTreeSet<String>,
+}
+impl<'a> PythonWrapper<'a> {
+    pub fn new(config: Config, ci: &'a ComponentInterface) -> Self {
+        let type_renderer = TypeRenderer::new(&config, ci);
+        let type_helper_code = type_renderer.render().unwrap();
+        let type_imports = type_renderer.imports.into_inner();
+        Self {
+            config,
+            ci,
+            type_helper_code,
+            type_imports,
+        }
+    }
+
+    pub fn imports(&self) -> Vec<String> {
+        self.type_imports.iter().cloned().collect()
+    }
+}
+
+fn fixup_keyword(name: String) -> String {
+    if KEYWORDS.contains(&name) {
+        format!("_{}", name)
+    } else {
+        name
+    }
+}
+
+#[derive(Clone, Default)]
+pub struct PythonCodeOracle;
+
+impl PythonCodeOracle {
+    // Map `Type` instances to a `Box<dyn CodeType>` for that type.
+    //
+    // There is a companion match in `templates/Types.py` which performs a similar function for the
+    // template code.
+    //
+    //   - When adding additional types here, make sure to also add a match arm to the `Types.py` template.
+    //   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+    fn create_code_type(&self, type_: TypeIdentifier) -> Box<dyn CodeType> {
+        match type_ {
+            Type::UInt8 => Box::new(primitives::UInt8CodeType),
+            Type::Int8 => Box::new(primitives::Int8CodeType),
+            Type::UInt16 => Box::new(primitives::UInt16CodeType),
+            Type::Int16 => Box::new(primitives::Int16CodeType),
+            Type::UInt32 => Box::new(primitives::UInt32CodeType),
+            Type::Int32 => Box::new(primitives::Int32CodeType),
+            Type::UInt64 => Box::new(primitives::UInt64CodeType),
+            Type::Int64 => Box::new(primitives::Int64CodeType),
+            Type::Float32 => Box::new(primitives::Float32CodeType),
+            Type::Float64 => Box::new(primitives::Float64CodeType),
+            Type::Boolean => Box::new(primitives::BooleanCodeType),
+            Type::String => Box::new(primitives::StringCodeType),
+
+            Type::Timestamp => Box::new(miscellany::TimestampCodeType),
+            Type::Duration => Box::new(miscellany::DurationCodeType),
+
+            Type::Enum(id) => Box::new(enum_::EnumCodeType::new(id)),
+            Type::Object(id) => Box::new(object::ObjectCodeType::new(id)),
+            Type::Record(id) => Box::new(record::RecordCodeType::new(id)),
+            Type::Error(id) => Box::new(error::ErrorCodeType::new(id)),
+            Type::CallbackInterface(id) => {
+                Box::new(callback_interface::CallbackInterfaceCodeType::new(id))
+            }
+
+            Type::Optional(inner) => Box::new(compounds::OptionalCodeType::new(*inner)),
+            Type::Sequence(inner) => Box::new(compounds::SequenceCodeType::new(*inner)),
+            Type::Map(key, value) => Box::new(compounds::MapCodeType::new(*key, *value)),
+            Type::External { name, .. } => Box::new(external::ExternalCodeType::new(name)),
+            Type::Custom { name, .. } => Box::new(custom::CustomCodeType::new(name)),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling create_code_type")
+            }
+        }
+    }
+}
+
+impl CodeOracle for PythonCodeOracle {
+    fn find(&self, type_: &TypeIdentifier) -> Box<dyn CodeType> {
+        self.create_code_type(type_.clone())
+    }
+
+    /// Get the idiomatic Python rendering of a class name (for enums, records, errors, etc).
+    fn class_name(&self, nm: &str) -> String {
+        fixup_keyword(nm.to_string().to_upper_camel_case())
+    }
+
+    /// Get the idiomatic Python rendering of a function name.
+    fn fn_name(&self, nm: &str) -> String {
+        fixup_keyword(nm.to_string().to_snake_case())
+    }
+
+    /// Get the idiomatic Python rendering of a variable name.
+    fn var_name(&self, nm: &str) -> String {
+        fixup_keyword(nm.to_string().to_snake_case())
+    }
+
+    /// Get the idiomatic Python rendering of an individual enum variant.
+    fn enum_variant_name(&self, nm: &str) -> String {
+        fixup_keyword(nm.to_string().to_shouty_snake_case())
+    }
+
+    /// Get the idiomatic Python rendering of an exception name
+    /// This replaces "Error" at the end of the name with "Exception".
+    fn error_name(&self, nm: &str) -> String {
+        let name = fixup_keyword(self.class_name(nm));
+        match name.strip_suffix("Error") {
+            None => name,
+            Some(stripped) => format!("{}Exception", stripped),
+        }
+    }
+
+    fn ffi_type_label(&self, ffi_type: &FFIType) -> String {
+        match ffi_type {
+            FFIType::Int8 => "ctypes.c_int8".to_string(),
+            FFIType::UInt8 => "ctypes.c_uint8".to_string(),
+            FFIType::Int16 => "ctypes.c_int16".to_string(),
+            FFIType::UInt16 => "ctypes.c_uint16".to_string(),
+            FFIType::Int32 => "ctypes.c_int32".to_string(),
+            FFIType::UInt32 => "ctypes.c_uint32".to_string(),
+            FFIType::Int64 => "ctypes.c_int64".to_string(),
+            FFIType::UInt64 => "ctypes.c_uint64".to_string(),
+            FFIType::Float32 => "ctypes.c_float".to_string(),
+            FFIType::Float64 => "ctypes.c_double".to_string(),
+            FFIType::RustArcPtr(_) => "ctypes.c_void_p".to_string(),
+            FFIType::RustBuffer => "RustBuffer".to_string(),
+            FFIType::ForeignBytes => "ForeignBytes".to_string(),
+            FFIType::ForeignCallback => "FOREIGN_CALLBACK_T".to_string(),
+        }
+    }
+}
+
+pub mod filters {
+    use super::*;
+
+    fn oracle() -> &'static PythonCodeOracle {
+        &PythonCodeOracle
+    }
+
+    pub fn type_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(codetype.type_label(oracle))
+    }
+
+    pub fn ffi_converter_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(codetype.ffi_converter_name(oracle))
+    }
+
+    pub fn canonical_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(codetype.canonical_name(oracle))
+    }
+
+    pub fn lift_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lift", ffi_converter_name(codetype)?))
+    }
+
+    pub fn lower_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lower", ffi_converter_name(codetype)?))
+    }
+
+    pub fn read_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.read", ffi_converter_name(codetype)?))
+    }
+
+    pub fn write_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.write", ffi_converter_name(codetype)?))
+    }
+
+    pub fn literal_py(
+        literal: &Literal,
+        codetype: &impl CodeType,
+    ) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(codetype.literal(oracle, literal))
+    }
+
+    /// Get the Python syntax for representing a given low-level `FFIType`.
+    pub fn ffi_type_name(type_: &FFIType) -> Result<String, askama::Error> {
+        Ok(oracle().ffi_type_label(type_))
+    }
+
+    /// Get the idiomatic Python rendering of a class name (for enums, records, errors, etc).
+    pub fn class_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().class_name(nm))
+    }
+
+    /// Get the idiomatic Python rendering of a function name.
+    pub fn fn_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().fn_name(nm))
+    }
+
+    /// Get the idiomatic Python rendering of a variable name.
+    pub fn var_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().var_name(nm))
+    }
+
+    /// Get the idiomatic Python rendering of an individual enum variant.
+    pub fn enum_variant_py(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().enum_variant_name(nm))
+    }
+
+    pub fn coerce_py(nm: &str, type_: &Type) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(oracle.find(type_).coerce(oracle, nm))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/object.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/object.rs
new file mode 100644
index 0000000000..7744865ec0
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/object.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct ObjectCodeType {
+    id: String,
+}
+
+impl ObjectCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ObjectCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+
+    fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+        nm.to_string()
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/primitives.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/primitives.rs
new file mode 100644
index 0000000000..948047fdd0
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/primitives.rs
@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+use crate::interface::Radix;
+use paste::paste;
+
+fn render_literal(_oracle: &dyn CodeOracle, literal: &Literal) -> String {
+    match literal {
+        Literal::Boolean(v) => {
+            if *v {
+                "True".into()
+            } else {
+                "False".into()
+            }
+        }
+        Literal::String(s) => format!("\"{}\"", s),
+        // https://docs.python.org/3/reference/lexical_analysis.html#integer-literals
+        Literal::Int(i, radix, _) => match radix {
+            Radix::Octal => format!("int(0o{:o})", i),
+            Radix::Decimal => format!("{}", i),
+            Radix::Hexadecimal => format!("{:#x}", i),
+        },
+        Literal::UInt(i, radix, _) => match radix {
+            Radix::Octal => format!("0o{:o}", i),
+            Radix::Decimal => format!("{}", i),
+            Radix::Hexadecimal => format!("{:#x}", i),
+        },
+        Literal::Float(string, _type_) => string.clone(),
+
+        _ => unreachable!("Literal"),
+    }
+}
+
+macro_rules! impl_code_type_for_primitive {
+    ($T:ty, $class_name:literal, $coerce_code:expr) => {
+        paste! {
+            pub struct $T;
+
+            impl CodeType for $T  {
+                fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+                    $class_name.into()
+                }
+
+                fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+                    render_literal(oracle, &literal)
+                }
+
+                fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+                    format!($coerce_code, nm)
+                }
+            }
+        }
+    };
+}
+
+impl_code_type_for_primitive!(BooleanCodeType, "Bool", "bool({})");
+impl_code_type_for_primitive!(StringCodeType, "String", "{}");
+impl_code_type_for_primitive!(Int8CodeType, "Int8", "int({})");
+impl_code_type_for_primitive!(Int16CodeType, "Int16", "int({})");
+impl_code_type_for_primitive!(Int32CodeType, "Int32", "int({})");
+impl_code_type_for_primitive!(Int64CodeType, "Int64", "int({})");
+impl_code_type_for_primitive!(UInt8CodeType, "UInt8", "int({})");
+impl_code_type_for_primitive!(UInt16CodeType, "UInt16", "int({})");
+impl_code_type_for_primitive!(UInt32CodeType, "UInt32", "int({})");
+impl_code_type_for_primitive!(UInt64CodeType, "UInt64", "int({})");
+impl_code_type_for_primitive!(Float32CodeType, "Float", "float({})");
+impl_code_type_for_primitive!(Float64CodeType, "Double", "float({})");
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/record.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/record.rs
new file mode 100644
index 0000000000..1dba8e49fe
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/gen_python/record.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct RecordCodeType {
+    id: String,
+}
+
+impl RecordCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for RecordCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, _literal: &Literal) -> String {
+        unreachable!();
+    }
+
+    fn coerce(&self, _oracle: &dyn CodeOracle, nm: &str) -> String {
+        nm.to_string()
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/python/mod.rs
new file mode 100644
index 0000000000..73245db86b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/mod.rs
@@ -0,0 +1,61 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::{env, io::Write, process::Command};
+
+use anyhow::{bail, Context, Result};
+use fs_err::File;
+
+pub mod gen_python;
+use camino::Utf8Path;
+pub use gen_python::{generate_python_bindings, Config};
+
+use super::super::interface::ComponentInterface;
+
+// Generate python bindings for the given ComponentInterface, in the given output directory.
+pub fn write_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+    try_format_code: bool,
+) -> Result<()> {
+    let py_file = out_dir.join(format!("{}.py", ci.namespace()));
+    let mut f = File::create(&py_file)?;
+    write!(f, "{}", generate_python_bindings(config, ci)?)?;
+
+    if try_format_code {
+        if let Err(e) = Command::new("yapf").arg(&py_file).output() {
+            println!(
+                "Warning: Unable to auto-format {} using yapf: {:?}",
+                py_file.file_name().unwrap(),
+                e
+            )
+        }
+    }
+
+    Ok(())
+}
+
+/// Execute the specifed python script, with environment based on the generated
+/// artifacts in the given output directory.
+pub fn run_script(out_dir: &Utf8Path, script_file: &Utf8Path) -> Result<()> {
+    let mut cmd = Command::new("python3");
+    // This helps python find the generated .py wrapper for rust component.
+    let pythonpath = env::var_os("PYTHONPATH").unwrap_or_default();
+    let pythonpath = env::join_paths(
+        env::split_paths(&pythonpath).chain(vec![out_dir.as_std_path().to_owned()]),
+    )?;
+    cmd.env("PYTHONPATH", pythonpath);
+    // We should now be able to execute the tests successfully.
+    cmd.arg(script_file);
+    let status = cmd
+        .spawn()
+        .context("Failed to spawn `python` when running script")?
+        .wait()
+        .context("Failed to wait for `python` when running script")?;
+    if !status.success() {
+        bail!("running `python` failed")
+    }
+    Ok(())
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/BooleanHelper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/BooleanHelper.py
new file mode 100644
index 0000000000..d7b64b91f7
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/BooleanHelper.py
@@ -0,0 +1,16 @@
+class FfiConverterBool:
+    @classmethod
+    def read(cls, buf):
+        return cls.lift(buf.readU8())
+
+    @classmethod
+    def write(cls, value, buf):
+        buf.writeU8(cls.lower(value))
+
+    @staticmethod
+    def lift(value):
+        return int(value) != 0
+
+    @staticmethod
+    def lower(value):
+        return 1 if value else 0
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CallbackInterfaceRuntime.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CallbackInterfaceRuntime.py
new file mode 100644
index 0000000000..e8a0ec56d9
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CallbackInterfaceRuntime.py
@@ -0,0 +1,73 @@
+import threading
+
+class ConcurrentHandleMap:
+    """
+    A map where inserting, getting and removing data is synchronized with a lock.
+    """
+
+    def __init__(self):
+        # type Handle = int
+        self._left_map = {}  # type: Dict[Handle, Any]
+        self._right_map = {}  # type: Dict[Any, Handle]
+
+        self._lock = threading.Lock()
+        self._current_handle = 0
+        self._stride = 1
+
+
+    def insert(self, obj):
+        with self._lock:
+            if obj in self._right_map:
+                return self._right_map[obj]
+            else:
+                handle = self._current_handle
+                self._current_handle += self._stride
+                self._left_map[handle] = obj
+                self._right_map[obj] = handle
+                return handle
+
+    def get(self, handle):
+        with self._lock:
+            return self._left_map.get(handle)
+
+    def remove(self, handle):
+        with self._lock:
+            if handle in self._left_map:
+                obj = self._left_map.pop(handle)
+                del self._right_map[obj]
+                return obj
+
+# Magic number for the Rust proxy to call using the same mechanism as every other method,
+# to free the callback once it's dropped by Rust.
+IDX_CALLBACK_FREE = 0
+
+class FfiConverterCallbackInterface:
+    _handle_map = ConcurrentHandleMap()
+
+    def __init__(self, cb):
+        self._foreign_callback = cb
+
+    def drop(self, handle):
+        self.__class__._handle_map.remove(handle)
+
+    @classmethod
+    def lift(cls, handle):
+        obj = cls._handle_map.get(handle)
+        if not obj:
+            raise InternalError("The object in the handle map has been dropped already")
+
+        return obj
+
+    @classmethod
+    def read(cls, buf):
+        handle = buf.readU64()
+        cls.lift(handle)
+
+    @classmethod
+    def lower(cls, cb):
+        handle = cls._handle_map.insert(cb)
+        return handle
+
+    @classmethod
+    def write(cls, cb, buf):
+        buf.writeU64(cls.lower(cb))
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CallbackInterfaceTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CallbackInterfaceTemplate.py
new file mode 100644
index 0000000000..de33d97fba
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CallbackInterfaceTemplate.py
@@ -0,0 +1,104 @@
+{%- let cbi = ci.get_callback_interface_definition(id).unwrap() %}
+{%- let foreign_callback = format!("foreignCallback{}", canonical_type_name) %}
+
+{% if self.include_once_check("CallbackInterfaceRuntime.py") %}{% include "CallbackInterfaceRuntime.py" %}{% endif %}
+
+# Declaration and FfiConverters for {{ type_name }} Callback Interface
+
+class {{ type_name }}:
+    {% for meth in cbi.methods() -%}
+    def {{ meth.name()|fn_name }}({% call py::arg_list_decl(meth) %}):
+        raise NotImplementedError
+
+    {% endfor %}
+
+def py_{{ foreign_callback }}(handle, method, args, buf_ptr):
+    {% for meth in cbi.methods() -%}
+    {% let method_name = format!("invoke_{}", meth.name())|fn_name %}
+    def {{ method_name }}(python_callback, args):
+        {#- Unpacking args from the RustBuffer #}
+        {%- if meth.arguments().len() != 0 -%}
+        {#- Calling the concrete callback object #}
+        with args.consumeWithStream() as buf:
+            rval = python_callback.{{ meth.name()|fn_name }}(
+                {% for arg in meth.arguments() -%}
+                {{ arg|read_fn }}(buf)
+                {%- if !loop.last %}, {% endif %}
+                {% endfor -%}
+            )
+        {% else %}
+        rval = python_callback.{{ meth.name()|fn_name }}()
+        {% endif -%}
+
+        {#- Packing up the return value into a RustBuffer #}
+        {%- match meth.return_type() -%}
+        {%- when Some with (return_type) -%}
+        with RustBuffer.allocWithBuilder() as builder:
+            {{ return_type|write_fn }}(rval, builder)
+            return builder.finalize()
+        {%- else -%}
+        return RustBuffer.alloc(0)
+        {% endmatch -%}
+    {% endfor %}
+
+    cb = {{ ffi_converter_name }}.lift(handle)
+    if not cb:
+        raise InternalError("No callback in handlemap; this is a Uniffi bug")
+
+    if method == IDX_CALLBACK_FREE:
+        {{ ffi_converter_name }}.drop(handle)
+        # No return value.
+        # See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+        return 0
+
+    {% for meth in cbi.methods() -%}
+    {% let method_name = format!("invoke_{}", meth.name())|fn_name -%}
+    if method == {{ loop.index }}:
+        # Call the method and handle any errors
+        # See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs` for details
+        try:
+            {%- match meth.throws_type() %}
+            {%- when Some(err) %}
+            try:
+                # Sucessful return
+                buf_ptr[0] = {{ method_name }}(cb, args)
+                return 1
+            except {{ err|type_name }} as e:
+                # Catch errors declared in the UDL file
+                with RustBuffer.allocWithBuilder() as builder:
+                    {{ err|write_fn }}(e, builder)
+                    buf_ptr[0] = builder.finalize()
+                return -2
+            {%- else %}
+            # Sucessful return
+            buf_ptr[0] = {{ method_name }}(cb, args)
+            return 1
+            {%- endmatch %}
+        except BaseException as e:
+            # Catch unexpected errors
+            try:
+                # Try to serialize the exception into a String
+                buf_ptr[0] = {{ Type::String.borrow()|lower_fn }}(repr(e))
+            except:
+                # If that fails, just give up
+                pass
+            return -1
+    {% endfor %}
+
+    # This should never happen, because an out of bounds method index won't
+    # ever be used. Once we can catch errors, we should return an InternalException.
+    # https://github.com/mozilla/uniffi-rs/issues/351
+
+    # An unexpected error happened.
+    # See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+    return -1
+
+# We need to keep this function reference alive:
+# if they get GC'd while in use then UniFFI internals could attempt to call a function
+# that is in freed memory.
+# That would be...uh...bad. Yeah, that's the word. Bad.
+{{ foreign_callback }} = FOREIGN_CALLBACK_T(py_{{ foreign_callback }})
+
+# The FfiConverter which transforms the Callbacks in to Handles to pass to Rust.
+rust_call(lambda err: _UniFFILib.{{ cbi.ffi_init_callback().name() }}({{ foreign_callback }}, err))
+{{ ffi_converter_name }} = FfiConverterCallbackInterface({{ foreign_callback }})
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CustomType.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CustomType.py
new file mode 100644
index 0000000000..9ce6a21ced
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/CustomType.py
@@ -0,0 +1,52 @@
+{%- match python_config.custom_types.get(name.as_str())  %}
+{% when None %}
+{#- No custom type config, just forward all methods to our builtin type #}
+class FfiConverterType{{ name }}:
+    @staticmethod
+    def write(value, buf):
+        {{ builtin|ffi_converter_name }}.write(value, buf)
+
+    @staticmethod
+    def read(buf):
+        return {{ builtin|ffi_converter_name }}.read(buf)
+
+    @staticmethod
+    def lift(value):
+        return {{ builtin|ffi_converter_name }}.lift(value)
+
+    @staticmethod
+    def lower(value):
+        return {{ builtin|ffi_converter_name }}.lower(value)
+
+{%- when Some(config) %}
+
+{%- match config.imports %}
+{%- when Some(imports) %}
+{%- for import_name in imports %}
+{{ self.add_import(import_name) }}
+{%- endfor %}
+{%- else %}
+{%- endmatch %}
+
+{#- Custom type config supplied, use it to convert the builtin type #}
+class FfiConverterType{{ name }}:
+    @staticmethod
+    def write(value, buf):
+        builtin_value = {{ config.from_custom.render("value") }}
+        {{ builtin|write_fn }}(builtin_value, buf)
+
+    @staticmethod
+    def read(buf):
+        builtin_value = {{ builtin|read_fn }}(buf)
+        return {{ config.into_custom.render("builtin_value") }}
+
+    @staticmethod
+    def lift(value):
+        builtin_value = {{ builtin|lift_fn }}(value)
+        return {{ config.into_custom.render("builtin_value") }}
+
+    @staticmethod
+    def lower(value):
+        builtin_value = {{ config.from_custom.render("value") }}
+        return {{ builtin|lower_fn }}(builtin_value)
+{%- endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/DurationHelper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/DurationHelper.py
new file mode 100644
index 0000000000..16fdd986f3
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/DurationHelper.py
@@ -0,0 +1,19 @@
+# The Duration type.
+# There is a loss of precision when converting from Rust durations,
+# which are accurate to the nanosecond,
+# to Python durations, which are only accurate to the microsecond.
+class FfiConverterDuration(FfiConverterRustBuffer):
+    @staticmethod
+    def read(buf):
+        seconds = buf.readU64()
+        microseconds = buf.readU32() / 1.0e3
+        return datetime.timedelta(seconds=seconds, microseconds=microseconds)
+
+    @staticmethod
+    def write(value, buf):
+        seconds = value.seconds + value.days * 24 * 3600
+        nanoseconds = value.microseconds * 1000
+        if seconds < 0:
+            raise ValueError("Invalid duration, must be non-negative")
+        buf.writeI64(seconds)
+        buf.writeU32(nanoseconds)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/EnumTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/EnumTemplate.py
new file mode 100644
index 0000000000..5c366d8855
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/EnumTemplate.py
@@ -0,0 +1,93 @@
+{#
+# Python has a built-in `enum` module which is nice to use, but doesn't support
+# variants with associated data. So, we switch here, and generate a stdlib `enum`
+# when none of the variants have associated data, or a generic nested-class
+# construct when they do.
+#}
+{%- let e = ci.get_enum_definition(name).unwrap() %}
+{% if e.is_flat() %}
+
+class {{ type_name }}(enum.Enum):
+    {% for variant in e.variants() -%}
+    {{ variant.name()|enum_variant_py }} = {{ loop.index }}
+    {% endfor %}
+{% else %}
+
+class {{ type_name }}:
+    def __init__(self):
+        raise RuntimeError("{{ type_name }} cannot be instantiated directly")
+
+    # Each enum variant is a nested class of the enum itself.
+    {% for variant in e.variants() -%}
+    class {{ variant.name()|enum_variant_py }}(object):
+        def __init__(self,{% for field in variant.fields() %}{{ field.name()|var_name }}{% if loop.last %}{% else %}, {% endif %}{% endfor %}):
+            {% if variant.has_fields() %}
+            {%- for field in variant.fields() %}
+            self.{{ field.name()|var_name }} = {{ field.name()|var_name }}
+            {%- endfor %}
+            {% else %}
+            pass
+            {% endif %}
+
+        def __str__(self):
+            return "{{ type_name }}.{{ variant.name()|enum_variant_py }}({% for field in variant.fields() %}{{ field.name()|var_name }}={}{% if loop.last %}{% else %}, {% endif %}{% endfor %})".format({% for field in variant.fields() %}self.{{ field.name()|var_name }}{% if loop.last %}{% else %}, {% endif %}{% endfor %})
+
+        def __eq__(self, other):
+            if not other.is_{{ variant.name()|var_name }}():
+                return False
+            {%- for field in variant.fields() %}
+            if self.{{ field.name()|var_name }} != other.{{ field.name()|var_name }}:
+                return False
+            {%- endfor %}
+            return True
+    {% endfor %}
+
+    # For each variant, we have an `is_NAME` method for easily checking
+    # whether an instance is that variant.
+    {% for variant in e.variants() -%}
+    def is_{{ variant.name()|var_name }}(self):
+        return isinstance(self, {{ type_name }}.{{ variant.name()|enum_variant_py }})
+    {% endfor %}
+
+# Now, a little trick - we make each nested variant class be a subclass of the main
+# enum class, so that method calls and instance checks etc will work intuitively.
+# We might be able to do this a little more neatly with a metaclass, but this'll do.
+{% for variant in e.variants() -%}
+{{ type_name }}.{{ variant.name()|enum_variant_py }} = type("{{ type_name }}.{{ variant.name()|enum_variant_py }}", ({{ type_name }}.{{variant.name()|enum_variant_py}}, {{ type_name }},), {})
+{% endfor %}
+
+{% endif %}
+
+class {{ ffi_converter_name }}(FfiConverterRustBuffer):
+    @staticmethod
+    def read(buf):
+        variant = buf.readI32()
+
+        {%- for variant in e.variants() %}
+        if variant == {{ loop.index }}:
+            {%- if e.is_flat() %}
+            return {{ type_name }}.{{variant.name()|enum_variant_py}}
+            {%- else %}
+            return {{ type_name }}.{{variant.name()|enum_variant_py}}(
+                {%- for field in variant.fields() %}
+                {{ field|read_fn }}(buf),
+                {%- endfor %}
+            )
+            {%- endif %}
+        {%- endfor %}
+        raise InternalError("Raw enum value doesn't match any cases")
+
+    def write(value, buf):
+        {%- for variant in e.variants() %}
+        {%- if e.is_flat() %}
+        if value == {{ type_name }}.{{ variant.name()|enum_variant_py }}:
+            buf.writeI32({{ loop.index }})
+        {%- else %}
+        if value.is_{{ variant.name()|var_name }}():
+            buf.writeI32({{ loop.index }})
+            {%- for field in variant.fields() %}
+            {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+            {%- endfor %}
+        {%- endif %}
+        {%- endfor %}
+
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ErrorTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ErrorTemplate.py
new file mode 100644
index 0000000000..305ae88618
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ErrorTemplate.py
@@ -0,0 +1,75 @@
+{%- let e = ci.get_error_definition(name).unwrap() %}
+
+# {{ type_name }}
+# We want to define each variant as a nested class that's also a subclass,
+# which is tricky in Python.  To accomplish this we're going to create each
+# class separated, then manually add the child classes to the base class's
+# __dict__.  All of this happens in dummy class to avoid polluting the module
+# namespace.
+class UniFFIExceptionTmpNamespace:
+    class {{ type_name }}(Exception):
+        pass
+    {% for variant in e.variants() %}
+    {%- let variant_type_name = variant.name()|class_name %}
+
+    {%- if e.is_flat() %}
+    class {{ variant_type_name }}({{ type_name }}):
+        def __str__(self):
+            return "{{ type_name }}.{{ variant_type_name }}({})".format(repr(super().__str__()))
+    {%- else %}
+    class {{ variant_type_name }}({{ type_name }}):
+        def __init__(self{% for field in variant.fields() %}, {{ field.name()|var_name }}{% endfor %}):
+            {%- if variant.has_fields() %}
+            {%- for field in variant.fields() %}
+            self.{{ field.name()|var_name }} = {{ field.name()|var_name }}
+            {%- endfor %}
+            {%- else %}
+            pass
+            {%- endif %}
+
+        def __str__(self):
+            {%- if variant.has_fields() %}
+            field_parts = [
+                {%- for field in variant.fields() %}
+                '{{ field.name()|var_name }}={!r}'.format(self.{{ field.name()|var_name }}),
+                {%- endfor %}
+            ]
+            return "{{ type_name }}.{{ variant_type_name }}({})".format(', '.join(field_parts))
+            {%- else %}
+            return "{{ type_name }}.{{ variant_type_name }}()"
+            {%- endif %}
+    {%- endif %}
+
+    {{ type_name }}.{{ variant_type_name }} = {{ variant_type_name }}
+    {%- endfor %}
+{{ type_name }} = UniFFIExceptionTmpNamespace.{{ type_name }}
+del UniFFIExceptionTmpNamespace
+
+
+class {{ ffi_converter_name }}(FfiConverterRustBuffer):
+    @staticmethod
+    def read(buf):
+        variant = buf.readI32()
+        {%- for variant in e.variants() %}
+        if variant == {{ loop.index }}:
+            return {{ type_name }}.{{ variant.name()|class_name }}(
+                {%- if e.is_flat() %}
+                {{ Type::String.borrow()|read_fn }}(buf),
+                {%- else %}
+                {%- for field in variant.fields() %}
+                {{ field.name()|var_name }}={{ field|read_fn }}(buf),
+                {%- endfor %}
+                {%- endif %}
+            )
+        {%- endfor %}
+        raise InternalError("Raw enum value doesn't match any cases")
+
+    @staticmethod
+    def write(value, buf):
+        {%- for variant in e.variants() %}
+        if isinstance(value, {{ type_name }}.{{ variant.name()|class_name }}):
+            buf.writeI32({{ loop.index }})
+            {%- for field in variant.fields() %}
+            {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+            {%- endfor %}
+        {%- endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ExternalTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ExternalTemplate.py
new file mode 100644
index 0000000000..b3acc5b2d1
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ExternalTemplate.py
@@ -0,0 +1 @@
+from {{ crate_name|fn_name }} import FfiConverterType{{ name }}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Float32Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Float32Helper.py
new file mode 100644
index 0000000000..e5783dd158
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Float32Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterFloat(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readFloat()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeFloat(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Float64Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Float64Helper.py
new file mode 100644
index 0000000000..57c2131eb8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Float64Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterDouble(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readDouble()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeDouble(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Helpers.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Helpers.py
new file mode 100644
index 0000000000..397d5e98f0
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Helpers.py
@@ -0,0 +1,67 @@
+# A handful of classes and functions to support the generated data structures.
+# This would be a good candidate for isolating in its own ffi-support lib.
+
+class InternalError(Exception):
+    pass
+
+class RustCallStatus(ctypes.Structure):
+    """
+    Error runtime.
+    """
+    _fields_ = [
+        ("code", ctypes.c_int8),
+        ("error_buf", RustBuffer),
+    ]
+
+    # These match the values from the uniffi::rustcalls module
+    CALL_SUCCESS = 0
+    CALL_ERROR = 1
+    CALL_PANIC = 2
+
+    def __str__(self):
+        if self.code == RustCallStatus.CALL_SUCCESS:
+            return "RustCallStatus(CALL_SUCCESS)"
+        elif self.code == RustCallStatus.CALL_ERROR:
+            return "RustCallStatus(CALL_ERROR)"
+        elif self.code == RustCallStatus.CALL_PANIC:
+            return "RustCallStatus(CALL_PANIC)"
+        else:
+            return "RustCallStatus(<invalid code>)"
+
+def rust_call(fn, *args):
+    # Call a rust function
+    return rust_call_with_error(None, fn, *args)
+
+def rust_call_with_error(error_ffi_converter, fn, *args):
+    # Call a rust function and handle any errors
+    #
+    # This function is used for rust calls that return Result<> and therefore can set the CALL_ERROR status code.
+    # error_ffi_converter must be set to the FFIConverter for the error class that corresponds to the result.
+    call_status = RustCallStatus(code=RustCallStatus.CALL_SUCCESS, error_buf=RustBuffer(0, 0, None))
+
+    args_with_error = args + (ctypes.byref(call_status),)
+    result = fn(*args_with_error)
+    if call_status.code == RustCallStatus.CALL_SUCCESS:
+        return result
+    elif call_status.code == RustCallStatus.CALL_ERROR:
+        if error_ffi_converter is None:
+            call_status.err_buf.contents.free()
+            raise InternalError("rust_call_with_error: CALL_ERROR, but error_ffi_converter is None")
+        else:
+            raise error_ffi_converter.lift(call_status.error_buf)
+    elif call_status.code == RustCallStatus.CALL_PANIC:
+        # When the rust code sees a panic, it tries to construct a RustBuffer
+        # with the message.  But if that code panics, then it just sends back
+        # an empty buffer.
+        if call_status.error_buf.len > 0:
+            msg = FfiConverterString.lift(call_status.error_buf)
+        else:
+            msg = "Unknown rust panic"
+        raise InternalError(msg)
+    else:
+        raise InternalError("Invalid RustCallStatus code: {}".format(
+            call_status.code))
+
+# A function pointer for a callback as defined by UniFFI.
+# Rust definition `fn(handle: u64, method: u32, args: RustBuffer, buf_ptr: *mut RustBuffer) -> int`
+FOREIGN_CALLBACK_T = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_ulonglong, ctypes.c_ulong, RustBuffer, ctypes.POINTER(RustBuffer))
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int16Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int16Helper.py
new file mode 100644
index 0000000000..b3d9602746
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int16Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterInt16(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readI16()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeI16(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int32Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int32Helper.py
new file mode 100644
index 0000000000..47a54d8c4a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int32Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterInt32(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readI32()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeI32(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int64Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int64Helper.py
new file mode 100644
index 0000000000..471b9967ce
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int64Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterInt64(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readI64()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeI64(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int8Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int8Helper.py
new file mode 100644
index 0000000000..524fea7ea9
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Int8Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterInt8(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readI8()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeI8(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/MapTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/MapTemplate.py
new file mode 100644
index 0000000000..7f42daa7a9
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/MapTemplate.py
@@ -0,0 +1,27 @@
+{%- let key_ffi_converter = key_type|ffi_converter_name %}
+{%- let value_ffi_converter = value_type|ffi_converter_name %}
+
+class {{ ffi_converter_name }}(FfiConverterRustBuffer):
+    @classmethod
+    def write(cls, items, buf):
+        buf.writeI32(len(items))
+        for (key, value) in items.items():
+            {{ key_ffi_converter }}.write(key, buf)
+            {{ value_ffi_converter }}.write(value, buf)
+
+    @classmethod
+    def read(cls, buf):
+        count = buf.readI32()
+        if count < 0:
+            raise InternalError("Unexpected negative map size")
+
+        # It would be nice to use a dict comprehension,
+        # but in Python 3.7 and before the evaluation order is not according to spec,
+        # so we we're reading the value before the key.
+        # This loop makes the order explicit: first reading the key, then the value.
+        d = {}
+        for i in range(count):
+            key = {{ key_ffi_converter }}.read(buf)
+            val = {{ value_ffi_converter }}.read(buf)
+            d[key] = val
+        return d
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/NamespaceLibraryTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/NamespaceLibraryTemplate.py
new file mode 100644
index 0000000000..4867ecb9b4
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/NamespaceLibraryTemplate.py
@@ -0,0 +1,39 @@
+# This is how we find and load the dynamic library provided by the component.
+# For now we just look it up by name.
+#
+# XXX TODO: This will probably grow some magic for resolving megazording in future.
+# E.g. we might start by looking for the named component in `libuniffi.so` and if
+# that fails, fall back to loading it separately from `lib${componentName}.so`.
+
+from pathlib import Path
+
+def loadIndirect():
+    if sys.platform == "darwin":
+        libname = "lib{}.dylib"
+    elif sys.platform.startswith("win"):
+        # As of python3.8, ctypes does not seem to search $PATH when loading DLLs.
+        # We could use `os.add_dll_directory` to configure the search path, but
+        # it doesn't feel right to mess with application-wide settings. Let's
+        # assume that the `.dll` is next to the `.py` file and load by full path.
+        libname = os.path.join(
+            os.path.dirname(__file__),
+            "{}.dll",
+        )
+    else:
+        # Anything else must be an ELF platform - Linux, *BSD, Solaris/illumos
+        libname = "lib{}.so"
+
+    lib = libname.format("{{ config.cdylib_name() }}")
+    path = str(Path(__file__).parent / lib)
+    return ctypes.cdll.LoadLibrary(path)
+
+# A ctypes library to expose the extern-C FFI definitions.
+# This is an implementation detail which will be called internally by the public API.
+
+_UniFFILib = loadIndirect()
+{%- for func in ci.iter_ffi_function_definitions() %}
+_UniFFILib.{{ func.name() }}.argtypes = (
+    {%- call py::arg_list_ffi_decl(func) -%}
+)
+_UniFFILib.{{ func.name() }}.restype = {% match func.return_type() %}{% when Some with (type_) %}{{ type_|ffi_type_name }}{% when None %}None{% endmatch %}
+{%- endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ObjectTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ObjectTemplate.py
new file mode 100644
index 0000000000..cc4cc35b4e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/ObjectTemplate.py
@@ -0,0 +1,74 @@
+{%- let obj = ci.get_object_definition(name).unwrap() %}
+
+class {{ type_name }}(object):
+    {%- match obj.primary_constructor() %}
+    {%- when Some with (cons) %}
+    def __init__(self, {% call py::arg_list_decl(cons) -%}):
+        {%- call py::setup_args_extra_indent(cons) %}
+        self._pointer = {% call py::to_ffi_call(cons) %}
+    {%- when None %}
+    {%- endmatch %}
+
+    def __del__(self):
+        # In case of partial initialization of instances.
+        pointer = getattr(self, "_pointer", None)
+        if pointer is not None:
+            rust_call(_UniFFILib.{{ obj.ffi_object_free().name() }}, pointer)
+
+    # Used by alternative constructors or any methods which return this type.
+    @classmethod
+    def _make_instance_(cls, pointer):
+        # Lightly yucky way to bypass the usual __init__ logic
+        # and just create a new instance with the required pointer.
+        inst = cls.__new__(cls)
+        inst._pointer = pointer
+        return inst
+
+    {% for cons in obj.alternate_constructors() -%}
+    @classmethod
+    def {{ cons.name()|fn_name }}(cls, {% call py::arg_list_decl(cons) %}):
+        {%- call py::setup_args_extra_indent(cons) %}
+        # Call the (fallible) function before creating any half-baked object instances.
+        pointer = {% call py::to_ffi_call(cons) %}
+        return cls._make_instance_(pointer)
+    {% endfor %}
+
+    {% for meth in obj.methods() -%}
+    {%- match meth.return_type() -%}
+
+    {%- when Some with (return_type) -%}
+    def {{ meth.name()|fn_name }}(self, {% call py::arg_list_decl(meth) %}):
+        {%- call py::setup_args_extra_indent(meth) %}
+        return {{ return_type|lift_fn }}(
+            {% call py::to_ffi_call_with_prefix("self._pointer", meth) %}
+        )
+
+    {%- when None -%}
+    def {{ meth.name()|fn_name }}(self, {% call py::arg_list_decl(meth) %}):
+        {%- call py::setup_args_extra_indent(meth) %}
+        {% call py::to_ffi_call_with_prefix("self._pointer", meth) %}
+    {% endmatch %}
+    {% endfor %}
+
+
+class {{ ffi_converter_name }}:
+    @classmethod
+    def read(cls, buf):
+        ptr = buf.readU64()
+        if ptr == 0:
+            raise InternalError("Raw pointer value was null")
+        return cls.lift(ptr)
+
+    @classmethod
+    def write(cls, value, buf):
+        if not isinstance(value, {{ type_name }}):
+            raise TypeError("Expected {{ type_name }} instance, {} found".format(value.__class__.__name__))
+        buf.writeU64(cls.lower(value))
+
+    @staticmethod
+    def lift(value):
+        return {{ type_name }}._make_instance_(value)
+
+    @staticmethod
+    def lower(value):
+        return value._pointer
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/OptionalTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/OptionalTemplate.py
new file mode 100644
index 0000000000..70f705362f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/OptionalTemplate.py
@@ -0,0 +1,21 @@
+{%- let inner_ffi_converter = inner_type|ffi_converter_name %}
+
+class {{ ffi_converter_name }}(FfiConverterRustBuffer):
+    @classmethod
+    def write(cls, value, buf):
+        if value is None:
+            buf.writeU8(0)
+            return
+
+        buf.writeU8(1)
+        {{ inner_ffi_converter }}.write(value, buf)
+
+    @classmethod
+    def read(cls, buf):
+        flag = buf.readU8()
+        if flag == 0:
+            return None
+        elif flag == 1:
+            return {{ inner_ffi_converter }}.read(buf)
+        else:
+            raise InternalError("Unexpected flag byte for optional type")
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RecordTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RecordTemplate.py
new file mode 100644
index 0000000000..2009d59e8a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RecordTemplate.py
@@ -0,0 +1,45 @@
+{%- let rec = ci.get_record_definition(name).unwrap() %}
+class {{ type_name }}:
+
+    def __init__(self, {% for field in rec.fields() %}
+    {{- field.name()|var_name }}
+    {%- if field.default_value().is_some() %} = DEFAULT{% endif %}
+    {%- if !loop.last %}, {% endif %}
+    {%- endfor %}):
+        {%- for field in rec.fields() %}
+        {%- let field_name = field.name()|var_name %}
+        {%- match field.default_value() %}
+        {%- when None %}
+        self.{{ field_name }} = {{ field_name }}
+        {%- when Some with(literal) %}
+        if {{ field_name }} is DEFAULT:
+            self.{{ field_name }} = {{ literal|literal_py(field) }}
+        else:
+            self.{{ field_name }} = {{ field_name }}
+        {%- endmatch %}
+        {%- endfor %}
+
+    def __str__(self):
+        return "{{ type_name }}({% for field in rec.fields() %}{{ field.name()|var_name }}={}{% if loop.last %}{% else %}, {% endif %}{% endfor %})".format({% for field in rec.fields() %}self.{{ field.name()|var_name }}{% if loop.last %}{% else %}, {% endif %}{% endfor %})
+
+    def __eq__(self, other):
+        {%- for field in rec.fields() %}
+        if self.{{ field.name()|var_name }} != other.{{ field.name()|var_name }}:
+            return False
+        {%- endfor %}
+        return True
+
+class {{ ffi_converter_name }}(FfiConverterRustBuffer):
+    @staticmethod
+    def read(buf):
+        return {{ type_name }}(
+            {%- for field in rec.fields() %}
+            {{ field.name()|var_name }}={{ field|read_fn }}(buf),
+            {%- endfor %}
+        )
+
+    @staticmethod
+    def write(value, buf):
+        {%- for field in rec.fields() %}
+        {{ field|write_fn }}(value.{{ field.name()|var_name }}, buf)
+        {%- endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RustBufferHelper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RustBufferHelper.py
new file mode 100644
index 0000000000..eafd2346bb
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RustBufferHelper.py
@@ -0,0 +1,23 @@
+# Types conforming to `FfiConverterPrimitive` pass themselves directly over the FFI.
+class FfiConverterPrimitive:
+    @classmethod
+    def lift(cls, value):
+        return value
+
+    @classmethod
+    def lower(cls, value):
+        return value
+
+# Helper class for wrapper types that will always go through a RustBuffer.
+# Classes should inherit from this and implement the `read` and `write` static methods.
+class FfiConverterRustBuffer:
+    @classmethod
+    def lift(cls, rbuf):
+        with rbuf.consumeWithStream() as stream:
+            return cls.read(stream)
+
+    @classmethod
+    def lower(cls, value):
+        with RustBuffer.allocWithBuilder() as builder:
+            cls.write(value, builder)
+            return builder.finalize()
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RustBufferTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RustBufferTemplate.py
new file mode 100644
index 0000000000..95a3b1f706
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/RustBufferTemplate.py
@@ -0,0 +1,190 @@
+
+class RustBuffer(ctypes.Structure):
+    _fields_ = [
+        ("capacity", ctypes.c_int32),
+        ("len", ctypes.c_int32),
+        ("data", ctypes.POINTER(ctypes.c_char)),
+    ]
+
+    @staticmethod
+    def alloc(size):
+        return rust_call(_UniFFILib.{{ ci.ffi_rustbuffer_alloc().name() }}, size)
+
+    @staticmethod
+    def reserve(rbuf, additional):
+        return rust_call(_UniFFILib.{{ ci.ffi_rustbuffer_reserve().name() }}, rbuf, additional)
+
+    def free(self):
+        return rust_call(_UniFFILib.{{ ci.ffi_rustbuffer_free().name() }}, self)
+
+    def __str__(self):
+        return "RustBuffer(capacity={}, len={}, data={})".format(
+            self.capacity,
+            self.len,
+            self.data[0:self.len]
+        )
+
+    @contextlib.contextmanager
+    def allocWithBuilder():
+        """Context-manger to allocate a buffer using a RustBufferBuilder.
+
+        The allocated buffer will be automatically freed if an error occurs, ensuring that
+        we don't accidentally leak it.
+        """
+        builder = RustBufferBuilder()
+        try:
+            yield builder
+        except:
+            builder.discard()
+            raise
+
+    @contextlib.contextmanager
+    def consumeWithStream(self):
+        """Context-manager to consume a buffer using a RustBufferStream.
+
+        The RustBuffer will be freed once the context-manager exits, ensuring that we don't
+        leak it even if an error occurs.
+        """
+        try:
+            s = RustBufferStream(self)
+            yield s
+            if s.remaining() != 0:
+                raise RuntimeError("junk data left in buffer after consuming")
+        finally:
+            self.free()
+
+
+class ForeignBytes(ctypes.Structure):
+    _fields_ = [
+        ("len", ctypes.c_int32),
+        ("data", ctypes.POINTER(ctypes.c_char)),
+    ]
+
+    def __str__(self):
+        return "ForeignBytes(len={}, data={})".format(self.len, self.data[0:self.len])
+
+
+class RustBufferStream(object):
+    """
+    Helper for structured reading of bytes from a RustBuffer
+    """
+
+    def __init__(self, rbuf):
+        self.rbuf = rbuf
+        self.offset = 0
+
+    def remaining(self):
+        return self.rbuf.len - self.offset
+
+    def _unpack_from(self, size, format):
+        if self.offset + size > self.rbuf.len:
+            raise InternalError("read past end of rust buffer")
+        value = struct.unpack(format, self.rbuf.data[self.offset:self.offset+size])[0]
+        self.offset += size
+        return value
+
+    def read(self, size):
+        if self.offset + size > self.rbuf.len:
+            raise InternalError("read past end of rust buffer")
+        data = self.rbuf.data[self.offset:self.offset+size]
+        self.offset += size
+        return data
+
+    def readI8(self):
+        return self._unpack_from(1, ">b")
+
+    def readU8(self):
+        return self._unpack_from(1, ">B")
+
+    def readI16(self):
+        return self._unpack_from(2, ">h")
+
+    def readU16(self):
+        return self._unpack_from(2, ">H")
+
+    def readI32(self):
+        return self._unpack_from(4, ">i")
+
+    def readU32(self):
+        return self._unpack_from(4, ">I")
+
+    def readI64(self):
+        return self._unpack_from(8, ">q")
+
+    def readU64(self):
+        return self._unpack_from(8, ">Q")
+
+    def readFloat(self):
+        v = self._unpack_from(4, ">f")
+        return v
+
+    def readDouble(self):
+        return self._unpack_from(8, ">d")
+
+
+class RustBufferBuilder(object):
+    """
+    Helper for structured writing of bytes into a RustBuffer.
+    """
+
+    def __init__(self):
+        self.rbuf = RustBuffer.alloc(16)
+        self.rbuf.len = 0
+
+    def finalize(self):
+        rbuf = self.rbuf
+        self.rbuf = None
+        return rbuf
+
+    def discard(self):
+        if self.rbuf is not None:
+            rbuf = self.finalize()
+            rbuf.free()
+
+    @contextlib.contextmanager
+    def _reserve(self, numBytes):
+        if self.rbuf.len + numBytes > self.rbuf.capacity:
+            self.rbuf = RustBuffer.reserve(self.rbuf, numBytes)
+        yield None
+        self.rbuf.len += numBytes
+
+    def _pack_into(self, size, format, value):
+        with self._reserve(size):
+            # XXX TODO: I feel like I should be able to use `struct.pack_into` here but can't figure it out.
+            for i, byte in enumerate(struct.pack(format, value)):
+                self.rbuf.data[self.rbuf.len + i] = byte
+
+    def write(self, value):
+        with self._reserve(len(value)):
+            for i, byte in enumerate(value):
+                self.rbuf.data[self.rbuf.len + i] = byte
+
+    def writeI8(self, v):
+        self._pack_into(1, ">b", v)
+
+    def writeU8(self, v):
+        self._pack_into(1, ">B", v)
+
+    def writeI16(self, v):
+        self._pack_into(2, ">h", v)
+
+    def writeU16(self, v):
+        self._pack_into(2, ">H", v)
+
+    def writeI32(self, v):
+        self._pack_into(4, ">i", v)
+
+    def writeU32(self, v):
+        self._pack_into(4, ">I", v)
+
+    def writeI64(self, v):
+        self._pack_into(8, ">q", v)
+
+    def writeU64(self, v):
+        self._pack_into(8, ">Q", v)
+
+    def writeFloat(self, v):
+        self._pack_into(4, ">f", v)
+
+    def writeDouble(self, v):
+        self._pack_into(8, ">d", v)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/SequenceTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/SequenceTemplate.py
new file mode 100644
index 0000000000..6de7bf2d4d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/SequenceTemplate.py
@@ -0,0 +1,19 @@
+{%- let inner_ffi_converter = inner_type|ffi_converter_name %}
+
+class {{ ffi_converter_name}}(FfiConverterRustBuffer):
+    @classmethod
+    def write(cls, value, buf):
+        items = len(value)
+        buf.writeI32(items)
+        for item in value:
+            {{ inner_ffi_converter }}.write(item, buf)
+
+    @classmethod
+    def read(cls, buf):
+        count = buf.readI32()
+        if count < 0:
+            raise InternalError("Unexpected negative sequence length")
+
+        return [
+            {{ inner_ffi_converter }}.read(buf) for i in range(count)
+        ]
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/StringHelper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/StringHelper.py
new file mode 100644
index 0000000000..f205f7c746
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/StringHelper.py
@@ -0,0 +1,25 @@
+class FfiConverterString:
+    @staticmethod
+    def read(buf):
+        size = buf.readI32()
+        if size < 0:
+            raise InternalError("Unexpected negative string length")
+        utf8Bytes = buf.read(size)
+        return utf8Bytes.decode("utf-8")
+
+    @staticmethod
+    def write(value, buf):
+        utf8Bytes = value.encode("utf-8")
+        buf.writeI32(len(utf8Bytes))
+        buf.write(utf8Bytes)
+
+    @staticmethod
+    def lift(buf):
+        with buf.consumeWithStream() as stream:
+            return stream.read(stream.remaining()).decode("utf-8")
+
+    @staticmethod
+    def lower(value):
+        with RustBuffer.allocWithBuilder() as builder:
+            builder.write(value.encode("utf-8"))
+            return builder.finalize()
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/TimestampHelper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/TimestampHelper.py
new file mode 100644
index 0000000000..ac87697551
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/TimestampHelper.py
@@ -0,0 +1,30 @@
+# The Timestamp type.
+# There is a loss of precision when converting from Rust timestamps,
+# which are accurate to the nanosecond,
+# to Python datetimes, which have a variable precision due to the use of float as representation.
+class FfiConverterTimestamp(FfiConverterRustBuffer):
+    @staticmethod
+    def read(buf):
+        seconds = buf.readI64()
+        microseconds = buf.readU32() / 1000
+        # Use fromtimestamp(0) then add the seconds using a timedelta.  This
+        # ensures that we get OverflowError rather than ValueError when
+        # seconds is too large.
+        if seconds >= 0:
+            return datetime.datetime.fromtimestamp(0, tz=datetime.timezone.utc) + datetime.timedelta(seconds=seconds, microseconds=microseconds)
+        else:
+            return datetime.datetime.fromtimestamp(0, tz=datetime.timezone.utc) - datetime.timedelta(seconds=-seconds, microseconds=microseconds)
+
+    @staticmethod
+    def write(value, buf):
+        if value >= datetime.datetime.fromtimestamp(0, datetime.timezone.utc):
+            sign = 1
+            delta = value - datetime.datetime.fromtimestamp(0, datetime.timezone.utc)
+        else:
+            sign = -1
+            delta = datetime.datetime.fromtimestamp(0, datetime.timezone.utc) - value
+
+        seconds = delta.seconds + delta.days * 24 * 3600
+        nanoseconds = delta.microseconds * 1000
+        buf.writeI64(sign * seconds)
+        buf.writeU32(nanoseconds)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/TopLevelFunctionTemplate.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/TopLevelFunctionTemplate.py
new file mode 100644
index 0000000000..2d0e09f22d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/TopLevelFunctionTemplate.py
@@ -0,0 +1,13 @@
+{%- match func.return_type() -%}
+{%- when Some with (return_type) %}
+
+def {{ func.name()|fn_name }}({%- call py::arg_list_decl(func) -%}):
+    {%- call py::setup_args(func) %}
+    return {{ return_type|lift_fn }}({% call py::to_ffi_call(func) %})
+
+{% when None %}
+
+def {{ func.name()|fn_name }}({%- call py::arg_list_decl(func) -%}):
+    {%- call py::setup_args(func) %}
+    {% call py::to_ffi_call(func) %}
+{% endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Types.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Types.py
new file mode 100644
index 0000000000..eb9502083e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/Types.py
@@ -0,0 +1,93 @@
+{%- import "macros.py" as py %}
+
+{%- for type_ in ci.iter_types() %}
+{%- let type_name = type_|type_name %}
+{%- let ffi_converter_name = type_|ffi_converter_name %}
+{%- let canonical_type_name = type_|canonical_name %}
+
+{#
+ # Map `Type` instances to an include statement for that type.
+ #
+ # There is a companion match in `PythonCodeOracle::create_code_type()` which performs a similar function for the
+ # Rust code.
+ #
+ #   - When adding additional types here, make sure to also add a match arm to that function.
+ #   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+ #}
+{%- match type_ %}
+
+{%- when Type::Boolean %}
+{%- include "BooleanHelper.py" %}
+
+{%- when Type::Int8 %}
+{%- include "Int8Helper.py" %}
+
+{%- when Type::Int16 %}
+{%- include "Int16Helper.py" %}
+
+{%- when Type::Int32 %}
+{%- include "Int32Helper.py" %}
+
+{%- when Type::Int64 %}
+{%- include "Int64Helper.py" %}
+
+{%- when Type::UInt8 %}
+{%- include "UInt8Helper.py" %}
+
+{%- when Type::UInt16 %}
+{%- include "UInt16Helper.py" %}
+
+{%- when Type::UInt32 %}
+{%- include "UInt32Helper.py" %}
+
+{%- when Type::UInt64 %}
+{%- include "UInt64Helper.py" %}
+
+{%- when Type::Float32 %}
+{%- include "Float32Helper.py" %}
+
+{%- when Type::Float64 %}
+{%- include "Float64Helper.py" %}
+
+{%- when Type::String %}
+{%- include "StringHelper.py" %}
+
+{%- when Type::Enum(name) %}
+{%- include "EnumTemplate.py" %}
+
+{%- when Type::Error(name) %}
+{%- include "ErrorTemplate.py" %}
+
+{%- when Type::Record(name) %}
+{%- include "RecordTemplate.py" %}
+
+{%- when Type::Object(name) %}
+{%- include "ObjectTemplate.py" %}
+
+{%- when Type::Timestamp %}
+{%- include "TimestampHelper.py" %}
+
+{%- when Type::Duration %}
+{%- include "DurationHelper.py" %}
+
+{%- when Type::Optional(inner_type) %}
+{%- include "OptionalTemplate.py" %}
+
+{%- when Type::Sequence(inner_type) %}
+{%- include "SequenceTemplate.py" %}
+
+{%- when Type::Map(key_type, value_type) %}
+{%- include "MapTemplate.py" %}
+
+{%- when Type::CallbackInterface(id) %}
+{%- include "CallbackInterfaceTemplate.py" %}
+
+{%- when Type::Custom { name, builtin } %}
+{%- include "CustomType.py" %}
+
+{%- when Type::External { name, crate_name } %}
+{%- include "ExternalTemplate.py" %}
+
+{%- else %}
+{%- endmatch %}
+{%- endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt16Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt16Helper.py
new file mode 100644
index 0000000000..f1cd114c0c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt16Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterUInt16(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readU16()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeU16(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt32Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt32Helper.py
new file mode 100644
index 0000000000..290cd5fe82
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt32Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterUInt32(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readU32()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeU32(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt64Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt64Helper.py
new file mode 100644
index 0000000000..f57dec1d92
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt64Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterUInt64(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readU64()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeU64(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt8Helper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt8Helper.py
new file mode 100644
index 0000000000..3a1582351b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/UInt8Helper.py
@@ -0,0 +1,8 @@
+class FfiConverterUInt8(FfiConverterPrimitive):
+    @staticmethod
+    def read(buf):
+        return buf.readU8()
+
+    @staticmethod
+    def write(value, buf):
+        buf.writeU8(value)
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/macros.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/macros.py
new file mode 100644
index 0000000000..e81ec1a6e9
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/macros.py
@@ -0,0 +1,101 @@
+{#
+// Template to call into rust. Used in several places.
+// Variable names in `arg_list_decl` should match up with arg lists
+// passed to rust via `_arg_list_ffi_call`
+#}
+
+{%- macro to_ffi_call(func) -%}
+    {%- match func.throws_type() -%}
+    {%- when Some with (e) -%}
+rust_call_with_error({{ e|ffi_converter_name }},
+    {%- else -%}
+rust_call(
+    {%- endmatch -%}
+    _UniFFILib.{{ func.ffi_func().name() }},
+    {%- call _arg_list_ffi_call(func) -%}
+)
+{%- endmacro -%}
+
+{%- macro to_ffi_call_with_prefix(prefix, func) -%}
+    {%- match func.throws_type() -%}
+    {%- when Some with (e) -%}
+rust_call_with_error(
+    {{ e|ffi_converter_name }},
+    {%- else -%}
+rust_call(
+    {%- endmatch -%}
+    _UniFFILib.{{ func.ffi_func().name() }},
+    {{- prefix }},
+    {%- call _arg_list_ffi_call(func) -%}
+)
+{%- endmacro -%}
+
+{%- macro _arg_list_ffi_call(func) %}
+    {%- for arg in func.arguments() %}
+        {{ arg|lower_fn }}({{ arg.name()|var_name }})
+        {%- if !loop.last %},{% endif %}
+    {%- endfor %}
+{%- endmacro -%}
+
+{#-
+// Arglist as used in Python declarations of methods, functions and constructors.
+// Note the var_name and type_name filters.
+-#}
+
+{% macro arg_list_decl(func) %}
+    {%- for arg in func.arguments() -%}
+        {{ arg.name()|var_name }}
+        {%- match arg.default_value() %}
+        {%- when Some with(literal) %} = DEFAULT
+        {%- else %}
+        {%- endmatch %}
+        {%- if !loop.last %},{% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+
+{#-
+// Arglist as used in the _UniFFILib function declations.
+// Note unfiltered name but ffi_type_name filters.
+-#}
+{%- macro arg_list_ffi_decl(func) %}
+    {%- for arg in func.arguments() %}
+    {{ arg.type_().borrow()|ffi_type_name }},
+    {%- endfor %}
+    ctypes.POINTER(RustCallStatus),
+{% endmacro -%}
+
+{#
+ # Setup function arguments by initializing default values and passing other
+ # values through coerce.
+ #}
+{%- macro setup_args(func) %}
+    {%- for arg in func.arguments() %}
+    {%- match arg.default_value() %}
+    {%- when None %}
+    {{ arg.name()|var_name }} = {{ arg.name()|var_name|coerce_py(arg.type_().borrow()) -}}
+    {%- when Some with(literal) %}
+    if {{ arg.name()|var_name }} is DEFAULT:
+        {{ arg.name()|var_name }} = {{ literal|literal_py(arg.type_().borrow()) }}
+    else:
+        {{ arg.name()|var_name }} = {{ arg.name()|var_name|coerce_py(arg.type_().borrow()) -}}
+    {%- endmatch %}
+    {% endfor -%}
+{%- endmacro -%}
+
+{#
+ # Exactly the same thing as `setup_args()` but with an extra 4 spaces of
+ # indent so that it works with object methods.
+ #}
+{%- macro setup_args_extra_indent(func) %}
+        {%- for arg in func.arguments() %}
+        {%- match arg.default_value() %}
+        {%- when None %}
+        {{ arg.name()|var_name }} = {{ arg.name()|var_name|coerce_py(arg.type_().borrow()) -}}
+        {%- when Some with(literal) %}
+        if {{ arg.name()|var_name }} is DEFAULT:
+            {{ arg.name()|var_name }} = {{ literal|literal_py(arg.type_().borrow()) }}
+        else:
+            {{ arg.name()|var_name }} = {{ arg.name()|var_name|coerce_py(arg.type_().borrow()) -}}
+        {%- endmatch %}
+        {% endfor -%}
+{%- endmacro -%}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/python/templates/wrapper.py b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/wrapper.py
new file mode 100644
index 0000000000..01695244db
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/python/templates/wrapper.py
@@ -0,0 +1,71 @@
+# This file was autogenerated by some hot garbage in the `uniffi` crate.
+# Trust me, you don't want to mess with it!
+
+# Tell mypy (a type checker) to ignore all errors from this file.
+# See https://mypy.readthedocs.io/en/stable/config_file.html?highlight=ignore-errors#confval-ignore_errors
+# mypy: ignore-errors
+
+# Common helper code.
+#
+# Ideally this would live in a separate .py file where it can be unittested etc
+# in isolation, and perhaps even published as a re-useable package.
+#
+# However, it's important that the details of how this helper code works (e.g. the
+# way that different builtin types are passed across the FFI) exactly match what's
+# expected by the rust code on the other side of the interface. In practice right
+# now that means coming from the exact some version of `uniffi` that was used to
+# compile the rust component. The easiest way to ensure this is to bundle the Python
+# helpers directly inline like we're doing here.
+
+import os
+import sys
+import ctypes
+import enum
+import struct
+import contextlib
+import datetime
+{%- for module_name in self.imports() %}
+import {{ module_name }}
+{%- endfor %}
+
+# Used for default argument values
+DEFAULT = object()
+
+{% include "RustBufferTemplate.py" %}
+{% include "Helpers.py" %}
+{% include "RustBufferHelper.py" %}
+
+# Contains loading, initialization code,
+# and the FFI Function declarations in a com.sun.jna.Library.
+{% include "NamespaceLibraryTemplate.py" %}
+
+# Public interface members begin here.
+{{ type_helper_code }}
+
+{%- for func in ci.function_definitions() %}
+{%- include "TopLevelFunctionTemplate.py" %}
+{%- endfor %}
+
+__all__ = [
+    "InternalError",
+    {%- for e in ci.enum_definitions() %}
+    "{{ e|type_name }}",
+    {%- endfor %}
+    {%- for record in ci.record_definitions() %}
+    "{{ record|type_name }}",
+    {%- endfor %}
+    {%- for func in ci.function_definitions() %}
+    "{{ func.name()|fn_name }}",
+    {%- endfor %}
+    {%- for obj in ci.object_definitions() %}
+    "{{ obj|type_name }}",
+    {%- endfor %}
+    {%- for e in ci.error_definitions() %}
+    "{{ e|type_name }}",
+    {%- endfor %}
+    {%- for c in ci.callback_interface_definitions() %}
+    "{{ c.name()|class_name }}",
+    {%- endfor %}
+]
+
+{% import "macros.py" as py %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/gen_ruby/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/ruby/gen_ruby/mod.rs
new file mode 100644
index 0000000000..415307bc63
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/gen_ruby/mod.rs
@@ -0,0 +1,273 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use anyhow::Result;
+use askama::Template;
+use heck::{ToShoutySnakeCase, ToSnakeCase, ToUpperCamelCase};
+use serde::{Deserialize, Serialize};
+use std::borrow::Borrow;
+
+use crate::interface::*;
+use crate::MergeWith;
+
+const RESERVED_WORDS: &[&str] = &[
+    "alias", "and", "BEGIN", "begin", "break", "case", "class", "def", "defined?", "do", "else",
+    "elsif", "END", "end", "ensure", "false", "for", "if", "module", "next", "nil", "not", "or",
+    "redo", "rescue", "retry", "return", "self", "super", "then", "true", "undef", "unles",
+    "until", "when", "while", "yield", "__FILE__", "__LINE__",
+];
+
+fn is_reserved_word(word: &str) -> bool {
+    RESERVED_WORDS.contains(&word)
+}
+
+// Some config options for it the caller wants to customize the generated ruby.
+// Note that this can only be used to control details of the ruby *that do not affect the underlying component*,
+// since the details of the underlying component are entirely determined by the `ComponentInterface`.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct Config {
+    cdylib_name: Option<String>,
+    cdylib_path: Option<String>,
+}
+
+impl Config {
+    pub fn cdylib_name(&self) -> String {
+        self.cdylib_name
+            .clone()
+            .unwrap_or_else(|| "uniffi".to_string())
+    }
+
+    pub fn custom_cdylib_path(&self) -> bool {
+        self.cdylib_path.is_some()
+    }
+
+    pub fn cdylib_path(&self) -> String {
+        self.cdylib_path.clone().unwrap_or_default()
+    }
+}
+
+impl From<&ComponentInterface> for Config {
+    fn from(ci: &ComponentInterface) -> Self {
+        Config {
+            cdylib_name: Some(format!("uniffi_{}", ci.namespace())),
+            cdylib_path: None,
+        }
+    }
+}
+
+impl MergeWith for Config {
+    fn merge_with(&self, other: &Self) -> Self {
+        Config {
+            cdylib_name: self.cdylib_name.merge_with(&other.cdylib_name),
+            cdylib_path: self.cdylib_path.merge_with(&other.cdylib_path),
+        }
+    }
+}
+
+#[derive(Template)]
+#[template(syntax = "rb", escape = "none", path = "wrapper.rb")]
+pub struct RubyWrapper<'a> {
+    config: Config,
+    ci: &'a ComponentInterface,
+}
+impl<'a> RubyWrapper<'a> {
+    pub fn new(config: Config, ci: &'a ComponentInterface) -> Self {
+        Self { config, ci }
+    }
+}
+
+mod filters {
+    use super::*;
+
+    pub fn type_ffi(type_: &FFIType) -> Result<String, askama::Error> {
+        Ok(match type_ {
+            FFIType::Int8 => ":int8".to_string(),
+            FFIType::UInt8 => ":uint8".to_string(),
+            FFIType::Int16 => ":int16".to_string(),
+            FFIType::UInt16 => ":uint16".to_string(),
+            FFIType::Int32 => ":int32".to_string(),
+            FFIType::UInt32 => ":uint32".to_string(),
+            FFIType::Int64 => ":int64".to_string(),
+            FFIType::UInt64 => ":uint64".to_string(),
+            FFIType::Float32 => ":float".to_string(),
+            FFIType::Float64 => ":double".to_string(),
+            FFIType::RustArcPtr(_) => ":pointer".to_string(),
+            FFIType::RustBuffer => "RustBuffer.by_value".to_string(),
+            FFIType::ForeignBytes => "ForeignBytes".to_string(),
+            FFIType::ForeignCallback => unimplemented!("Callback interfaces are not implemented"),
+        })
+    }
+
+    pub fn literal_rb(literal: &Literal) -> Result<String, askama::Error> {
+        Ok(match literal {
+            Literal::Boolean(v) => {
+                if *v {
+                    "true".into()
+                } else {
+                    "false".into()
+                }
+            }
+            // use the double-quote form to match with the other languages, and quote escapes.
+            Literal::String(s) => format!("\"{}\"", s),
+            Literal::Null => "nil".into(),
+            Literal::EmptySequence => "[]".into(),
+            Literal::EmptyMap => "{}".into(),
+            Literal::Enum(v, type_) => match type_ {
+                Type::Enum(name) => format!("{}::{}", class_name_rb(name)?, enum_name_rb(v)?),
+                _ => panic!("Unexpected type in enum literal: {:?}", type_),
+            },
+            // https://docs.ruby-lang.org/en/2.0.0/syntax/literals_rdoc.html
+            Literal::Int(i, radix, _) => match radix {
+                Radix::Octal => format!("0o{:o}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+            Literal::UInt(i, radix, _) => match radix {
+                Radix::Octal => format!("0o{:o}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+            Literal::Float(string, _type_) => string.clone(),
+        })
+    }
+
+    pub fn class_name_rb(nm: &str) -> Result<String, askama::Error> {
+        Ok(nm.to_string().to_upper_camel_case())
+    }
+
+    pub fn fn_name_rb(nm: &str) -> Result<String, askama::Error> {
+        Ok(nm.to_string().to_snake_case())
+    }
+
+    pub fn var_name_rb(nm: &str) -> Result<String, askama::Error> {
+        let nm = nm.to_string();
+        let prefix = if is_reserved_word(&nm) { "_" } else { "" };
+
+        Ok(format!("{}{}", prefix, nm.to_snake_case()))
+    }
+
+    pub fn enum_name_rb(nm: &str) -> Result<String, askama::Error> {
+        Ok(nm.to_string().to_shouty_snake_case())
+    }
+
+    pub fn coerce_rb(nm: &str, type_: &Type) -> Result<String, askama::Error> {
+        Ok(match type_ {
+            Type::Int8
+            | Type::UInt8
+            | Type::Int16
+            | Type::UInt16
+            | Type::Int32
+            | Type::UInt32
+            | Type::Int64
+            | Type::UInt64 => format!("{}.to_i", nm), // TODO: check max/min value
+            Type::Float32 | Type::Float64 => format!("{}.to_f", nm),
+            Type::Boolean => format!("{} ? true : false", nm),
+            Type::Object(_) | Type::Enum(_) | Type::Error(_) | Type::Record(_) => nm.to_string(),
+            Type::String => format!("{}.to_s", nm),
+            Type::Timestamp | Type::Duration => nm.to_string(),
+            Type::CallbackInterface(_) => panic!("No support for coercing callback interfaces yet"),
+            Type::Optional(t) => format!("({} ? {} : nil)", nm, coerce_rb(nm, t)?),
+            Type::Sequence(t) => {
+                let coerce_code = coerce_rb("v", t)?;
+                if coerce_code == "v" {
+                    nm.to_string()
+                } else {
+                    format!("{}.map {{ |v| {} }}", nm, coerce_code)
+                }
+            }
+            Type::Map(_k, t) => {
+                let k_coerce_code = coerce_rb("k", &Type::String)?;
+                let v_coerce_code = coerce_rb("v", t)?;
+
+                if k_coerce_code == "k" && v_coerce_code == "v" {
+                    nm.to_string()
+                } else {
+                    format!(
+                        "{}.each.with_object({{}}) {{ |(k, v), res| res[{}] = {} }}",
+                        nm, k_coerce_code, v_coerce_code,
+                    )
+                }
+            }
+            Type::External { .. } => panic!("No support for external types, yet"),
+            Type::Custom { .. } => panic!("No support for custom types, yet"),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling coerce_rb")
+            }
+        })
+    }
+
+    pub fn lower_rb(nm: &str, type_: &Type) -> Result<String, askama::Error> {
+        Ok(match type_ {
+            Type::Int8
+            | Type::UInt8
+            | Type::Int16
+            | Type::UInt16
+            | Type::Int32
+            | Type::UInt32
+            | Type::Int64
+            | Type::UInt64
+            | Type::Float32
+            | Type::Float64 => nm.to_string(),
+            Type::Boolean => format!("({} ? 1 : 0)", nm),
+            Type::String => format!("RustBuffer.allocFromString({})", nm),
+            Type::Object(name) => format!("({}._uniffi_lower {})", class_name_rb(name)?, nm),
+            Type::CallbackInterface(_) => panic!("No support for lowering callback interfaces yet"),
+            Type::Error(_) => panic!("No support for lowering errors, yet"),
+            Type::Enum(_)
+            | Type::Record(_)
+            | Type::Optional(_)
+            | Type::Sequence(_)
+            | Type::Timestamp
+            | Type::Duration
+            | Type::Map(_, _) => format!(
+                "RustBuffer.alloc_from_{}({})",
+                class_name_rb(&type_.canonical_name())?,
+                nm
+            ),
+            Type::External { .. } => panic!("No support for lowering external types, yet"),
+            Type::Custom { .. } => panic!("No support for lowering custom types, yet"),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling lower_rb")
+            }
+        })
+    }
+
+    pub fn lift_rb(nm: &str, type_: &Type) -> Result<String, askama::Error> {
+        Ok(match type_ {
+            Type::Int8
+            | Type::UInt8
+            | Type::Int16
+            | Type::UInt16
+            | Type::Int32
+            | Type::UInt32
+            | Type::Int64
+            | Type::UInt64 => format!("{}.to_i", nm),
+            Type::Float32 | Type::Float64 => format!("{}.to_f", nm),
+            Type::Boolean => format!("1 == {}", nm),
+            Type::String => format!("{}.consumeIntoString", nm),
+            Type::Object(name) => format!("{}._uniffi_allocate({})", class_name_rb(name)?, nm),
+            Type::CallbackInterface(_) => panic!("No support for lifting callback interfaces, yet"),
+            Type::Error(_) => panic!("No support for lowering errors, yet"),
+            Type::Enum(_)
+            | Type::Record(_)
+            | Type::Optional(_)
+            | Type::Sequence(_)
+            | Type::Timestamp
+            | Type::Duration
+            | Type::Map(_, _) => format!(
+                "{}.consumeInto{}",
+                nm,
+                class_name_rb(&type_.canonical_name())?
+            ),
+            Type::External { .. } => panic!("No support for lifting external types, yet"),
+            Type::Custom { .. } => panic!("No support for lifting custom types, yet"),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling lift_rb")
+            }
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/gen_ruby/tests.rs b/third_party/rust/uniffi_bindgen/src/bindings/ruby/gen_ruby/tests.rs
new file mode 100644
index 0000000000..9ae5d1816f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/gen_ruby/tests.rs
@@ -0,0 +1,47 @@
+use super::{is_reserved_word, Config};
+
+#[test]
+fn when_reserved_word() {
+    assert!(is_reserved_word("end"));
+}
+
+#[test]
+fn when_not_reserved_word() {
+    assert!(!is_reserved_word("ruby"));
+}
+
+#[test]
+fn cdylib_name() {
+    let config = Config {
+        cdylib_name: None,
+        cdylib_path: None,
+    };
+
+    assert_eq!("uniffi", config.cdylib_name());
+
+    let config = Config {
+        cdylib_name: Some("todolist".to_string()),
+        cdylib_path: None,
+    };
+
+    assert_eq!("todolist", config.cdylib_name());
+}
+
+#[test]
+fn cdylib_path() {
+    let config = Config {
+        cdylib_name: None,
+        cdylib_path: None,
+    };
+
+    assert_eq!("", config.cdylib_path());
+    assert!(!config.custom_cdylib_path());
+
+    let config = Config {
+        cdylib_name: None,
+        cdylib_path: Some("/foo/bar".to_string()),
+    };
+
+    assert_eq!("/foo/bar", config.cdylib_path());
+    assert!(config.custom_cdylib_path());
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/ruby/mod.rs
new file mode 100644
index 0000000000..5e5b267719
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/mod.rs
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::{env, io::Write, process::Command};
+
+use anyhow::{bail, Context, Result};
+use fs_err::File;
+
+pub mod gen_ruby;
+use camino::Utf8Path;
+pub use gen_ruby::{Config, RubyWrapper};
+
+use super::super::interface::ComponentInterface;
+
+// Generate ruby bindings for the given ComponentInterface, in the given output directory.
+
+pub fn write_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+    try_format_code: bool,
+) -> Result<()> {
+    let rb_file = out_dir.join(format!("{}.rb", ci.namespace()));
+    let mut f = File::create(&rb_file)?;
+    write!(f, "{}", generate_ruby_bindings(config, ci)?)?;
+
+    if try_format_code {
+        if let Err(e) = Command::new("rubocop").arg("-A").arg(&rb_file).output() {
+            println!(
+                "Warning: Unable to auto-format {} using rubocop: {:?}",
+                rb_file.file_name().unwrap(),
+                e
+            )
+        }
+    }
+
+    Ok(())
+}
+
+// Generate ruby bindings for the given ComponentInterface, as a string.
+
+pub fn generate_ruby_bindings(config: &Config, ci: &ComponentInterface) -> Result<String> {
+    use askama::Template;
+    RubyWrapper::new(config.clone(), ci)
+        .render()
+        .context("failed to render ruby bindings")
+}
+
+/// Execute the specifed ruby script, with environment based on the generated
+/// artifacts in the given output directory.
+pub fn run_script(out_dir: &Utf8Path, script_file: &Utf8Path) -> Result<()> {
+    let mut cmd = Command::new("ruby");
+    // This helps ruby find the generated .rb wrapper for rust component.
+    let rubypath = env::var_os("RUBYLIB").unwrap_or_default();
+    let rubypath =
+        env::join_paths(env::split_paths(&rubypath).chain(vec![out_dir.as_std_path().to_owned()]))?;
+
+    cmd.env("RUBYLIB", rubypath);
+    // We should now be able to execute the tests successfully.
+    cmd.arg(script_file);
+    let status = cmd
+        .spawn()
+        .context("Failed to spawn `ruby` when running script")?
+        .wait()
+        .context("Failed to wait for `ruby` when running script")?;
+    if !status.success() {
+        bail!("running `ruby` failed")
+    }
+    Ok(())
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/EnumTemplate.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/EnumTemplate.rb
new file mode 100644
index 0000000000..23b701f6a7
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/EnumTemplate.rb
@@ -0,0 +1,59 @@
+{% if e.is_flat() %}
+
+class {{ e.name()|class_name_rb }}
+  {% for variant in e.variants() -%}
+  {{ variant.name()|enum_name_rb }} = {{ loop.index }}
+  {% endfor %}
+end
+
+{% else %}
+
+class {{ e.name()|class_name_rb }}
+  def initialize
+    raise RuntimeError, '{{ e.name()|class_name_rb }} cannot be instantiated directly'
+  end
+
+  # Each enum variant is a nested class of the enum itself.
+  {% for variant in e.variants() -%}
+  class {{ variant.name()|enum_name_rb }}
+    {% if variant.has_fields() %}
+    attr_reader {% for field in variant.fields() %}:{{ field.name()|var_name_rb }}{% if loop.last %}{% else %}, {% endif %}{%- endfor %}
+    {% endif %}
+    def initialize({% for field in variant.fields() %}{{ field.name()|var_name_rb }}{% if loop.last %}{% else %}, {% endif %}{% endfor %})
+      {% if variant.has_fields() %}
+      {%- for field in variant.fields() %}
+      @{{ field.name()|var_name_rb }} = {{ field.name()|var_name_rb }}
+      {%- endfor %}
+      {% else %}
+      {% endif %}
+    end
+
+    def to_s
+      "{{ e.name()|class_name_rb }}::{{ variant.name()|enum_name_rb }}({% for field in variant.fields() %}{{ field.name() }}=#{@{{ field.name() }}}{% if loop.last %}{% else %}, {% endif %}{% endfor %})"
+    end
+
+    def ==(other)
+      if !other.{{ variant.name()|var_name_rb }}?
+        return false
+      end
+      {%- for field in variant.fields() %}
+      if @{{ field.name()|var_name_rb }} != other.{{ field.name()|var_name_rb }}
+        return false
+      end
+      {%- endfor %}
+
+      true
+    end
+
+    # For each variant, we have an `NAME?` method for easily checking
+    # whether an instance is that variant.
+    {% for variant in e.variants() %}
+    def {{ variant.name()|var_name_rb }}?
+      instance_of? {{ e.name()|class_name_rb }}::{{ variant.name()|enum_name_rb }}
+    end
+    {% endfor %}
+  end
+  {% endfor %}
+end
+
+{% endif %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/ErrorTemplate.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/ErrorTemplate.rb
new file mode 100644
index 0000000000..3a64e9ffeb
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/ErrorTemplate.rb
@@ -0,0 +1,117 @@
+class RustCallStatus < FFI::Struct
+  layout :code,    :int8,
+         :error_buf, RustBuffer
+
+  def code
+    self[:code]
+  end
+
+  def error_buf
+    self[:error_buf]
+  end
+
+  def to_s
+    "RustCallStatus(code=#{self[:code]})"
+  end
+end
+
+# These match the values from the uniffi::rustcalls module
+CALL_SUCCESS = 0
+CALL_ERROR = 1
+CALL_PANIC = 2
+{%- for e in ci.error_definitions() %}
+{% if e.is_flat() %}
+class {{ e.name()|class_name_rb }}
+    {%- for variant in e.variants() %}
+    {{ variant.name()|class_name_rb }} = Class.new StandardError
+    {%- endfor %}
+{% else %}
+module {{ e.name()|class_name_rb }}
+  {%- for variant in e.variants() %}
+  class {{ variant.name()|class_name_rb }} < StandardError
+    def initialize({% for field in variant.fields() %}{{ field.name()|var_name_rb }}{% if !loop.last %}, {% endif %}{% endfor %})
+        {%- for field in variant.fields() %}
+        @{{ field.name()|var_name_rb }} = {{ field.name()|var_name_rb }}
+        {%- endfor %}
+        super()
+      end
+    {%- if variant.has_fields() %}
+
+    attr_reader {% for field in variant.fields() %}:{{ field.name()|var_name_rb }}{% if !loop.last %}, {% endif %}{% endfor %}
+    {% endif %}
+
+    def to_s
+     "#{self.class.name}({% for field in variant.fields() %}{{ field.name()|var_name_rb }}=#{@{{ field.name()|var_name_rb }}.inspect}{% if !loop.last %}, {% endif %}{% endfor %})"
+    end
+  end
+  {%- endfor %}
+{% endif %}
+end
+{%- endfor %}
+
+# Map error modules to the RustBuffer method name that reads them
+ERROR_MODULE_TO_READER_METHOD = {
+{%- for e in ci.error_definitions() %}
+{%- let typ=ci.get_type(e.name()).unwrap() %}
+{%- let canonical_type_name = typ.canonical_name().borrow()|class_name_rb %}
+  {{ e.name()|class_name_rb }} => :read{{ canonical_type_name }},
+{%- endfor %}
+}
+
+private_constant :ERROR_MODULE_TO_READER_METHOD, :CALL_SUCCESS, :CALL_ERROR, :CALL_PANIC,
+                 :RustCallStatus
+
+def self.consume_buffer_into_error(error_module, rust_buffer)
+  rust_buffer.consumeWithStream do |stream|
+    reader_method = ERROR_MODULE_TO_READER_METHOD[error_module]
+    return stream.send(reader_method)
+  end
+end
+
+class InternalError < StandardError
+end
+
+def self.rust_call(fn_name, *args)
+  # Call a rust function
+  rust_call_with_error(nil, fn_name, *args)
+end
+
+def self.rust_call_with_error(error_module, fn_name, *args)
+  # Call a rust function and handle errors
+  #
+  # Use this when the rust function returns a Result<>.  error_module must be the error_module that corresponds to that Result.
+
+
+  # Note: RustCallStatus.new zeroes out the struct, which is exactly what we
+  # want to pass to Rust (code=0, error_buf=RustBuffer(len=0, capacity=0,
+  # data=NULL))
+  status = RustCallStatus.new
+  args << status
+
+  result = UniFFILib.public_send(fn_name, *args)
+
+  case status.code
+  when CALL_SUCCESS
+    result
+  when CALL_ERROR
+    if error_module.nil?
+      status.error_buf.free
+      raise InternalError, "CALL_ERROR with no error_module set"
+    else
+      raise consume_buffer_into_error(error_module, status.error_buf)
+    end
+  when CALL_PANIC
+    # When the rust code sees a panic, it tries to construct a RustBuffer
+    # with the message.  But if that code panics, then it just sends back
+    # an empty buffer.
+    if status.error_buf.len > 0
+      raise InternalError, status.error_buf.consumeIntoString()
+    else
+      raise InternalError, "Rust panic"
+    end
+  else
+    raise InternalError, "Unknown call status: #{status.code}"
+  end
+end
+
+private_class_method :consume_buffer_into_error
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/NamespaceLibraryTemplate.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/NamespaceLibraryTemplate.rb
new file mode 100644
index 0000000000..858b42bf91
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/NamespaceLibraryTemplate.rb
@@ -0,0 +1,17 @@
+# This is how we find and load the dynamic library provided by the component.
+# For now we just look it up by name.
+module UniFFILib
+  extend FFI::Library
+
+  {% if config.custom_cdylib_path() %}
+  ffi_lib {{ config.cdylib_path() }}
+  {% else %}
+  ffi_lib '{{ config.cdylib_name() }}'
+  {% endif %}
+
+  {% for func in ci.iter_ffi_function_definitions() -%}
+  attach_function :{{ func.name() }},
+    {%- call rb::arg_list_ffi_decl(func) %},
+    {% match func.return_type() %}{% when Some with (type_) %}{{ type_|type_ffi }}{% when None %}:void{% endmatch %}
+  {% endfor %}
+end
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/ObjectTemplate.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/ObjectTemplate.rb
new file mode 100644
index 0000000000..6072bb309a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/ObjectTemplate.rb
@@ -0,0 +1,73 @@
+class {{ obj.name()|class_name_rb }}
+
+  # A private helper for initializing instances of the class from a raw pointer,
+  # bypassing any initialization logic and ensuring they are GC'd properly.
+  def self._uniffi_allocate(pointer)
+    pointer.autorelease = false
+    inst = allocate
+    inst.instance_variable_set :@pointer, pointer
+    ObjectSpace.define_finalizer(inst, _uniffi_define_finalizer_by_pointer(pointer, inst.object_id))
+    return inst
+  end
+
+  # A private helper for registering an object finalizer.
+  # N.B. it's important that this does not capture a reference
+  # to the actual instance, only its underlying pointer.
+  def self._uniffi_define_finalizer_by_pointer(pointer, object_id)
+    Proc.new do |_id|
+      {{ ci.namespace()|class_name_rb }}.rust_call(
+        :{{ obj.ffi_object_free().name() }},
+        pointer
+      )
+    end
+  end
+
+  # A private helper for lowering instances into a raw pointer.
+  # This does an explicit typecheck, because accidentally lowering a different type of
+  # object in a place where this type is expected, could lead to memory unsafety.
+  def self._uniffi_lower(inst)
+    if not inst.is_a? self
+      raise TypeError.new "Expected a {{ obj.name()|class_name_rb }} intance, got #{inst}"
+    end
+    return inst.instance_variable_get :@pointer
+  end
+
+  {%- match obj.primary_constructor() %}
+  {%- when Some with (cons) %}
+  def initialize({% call rb::arg_list_decl(cons) -%})
+    {%- call rb::coerce_args_extra_indent(cons) %}
+    pointer = {% call rb::to_ffi_call(cons) %}
+    @pointer = pointer
+    ObjectSpace.define_finalizer(self, self.class._uniffi_define_finalizer_by_pointer(pointer, self.object_id))
+  end
+  {%- when None %}
+  {%- endmatch %}
+
+  {% for cons in obj.alternate_constructors() -%}
+  def self.{{ cons.name()|fn_name_rb }}({% call rb::arg_list_decl(cons) %})
+    {%- call rb::coerce_args_extra_indent(cons) %}
+    # Call the (fallible) function before creating any half-baked object instances.
+    # Lightly yucky way to bypass the usual "initialize" logic
+    # and just create a new instance with the required pointer.
+    return _uniffi_allocate({% call rb::to_ffi_call(cons) %})
+  end
+  {% endfor %}
+
+  {% for meth in obj.methods() -%}
+  {%- match meth.return_type() -%}
+
+  {%- when Some with (return_type) -%}
+  def {{ meth.name()|fn_name_rb }}({% call rb::arg_list_decl(meth) %})
+    {%- call rb::coerce_args_extra_indent(meth) %}
+    result = {% call rb::to_ffi_call_with_prefix("@pointer", meth) %}
+    return {{ "result"|lift_rb(return_type) }}
+  end
+
+  {%- when None -%}
+  def {{ meth.name()|fn_name_rb }}({% call rb::arg_list_decl(meth) %})
+      {%- call rb::coerce_args_extra_indent(meth) %}
+      {% call rb::to_ffi_call_with_prefix("@pointer", meth) %}
+  end
+  {% endmatch %}
+  {% endfor %}
+end
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RecordTemplate.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RecordTemplate.rb
new file mode 100644
index 0000000000..c940b31060
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RecordTemplate.rb
@@ -0,0 +1,20 @@
+# Record type {{ rec.name() }}
+class {{ rec.name()|class_name_rb }}
+  attr_reader {% for field in rec.fields() %}:{{ field.name()|var_name_rb }}{% if loop.last %}{% else %}, {% endif %}{%- endfor %}
+
+  def initialize({% for field in rec.fields() %}{{ field.name()|var_name_rb }}{% if loop.last %}{% else %}, {% endif %}{% endfor %})
+    {%- for field in rec.fields() %}
+    @{{ field.name()|var_name_rb }} = {{ field.name()|var_name_rb }}
+    {%- endfor %}
+  end
+
+  def ==(other)
+    {%- for field in rec.fields() %}
+    if @{{ field.name()|var_name_rb }} != other.{{ field.name()|var_name_rb }}
+      return false
+    end
+    {%- endfor %}
+
+    true
+  end
+end
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferBuilder.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferBuilder.rb
new file mode 100644
index 0000000000..ee05badc64
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferBuilder.rb
@@ -0,0 +1,237 @@
+
+# Helper for structured writing of values into a RustBuffer.
+class RustBufferBuilder
+  def initialize
+    @rust_buf = RustBuffer.alloc 16
+    @rust_buf.len = 0
+  end
+
+  def finalize
+    rbuf = @rust_buf
+
+    @rust_buf = nil
+
+    rbuf
+  end
+
+  def discard
+    return if @rust_buf.nil?
+
+    rbuf = finalize
+    rbuf.free
+  end
+
+  def write(value)
+    reserve(value.bytes.size) do
+      @rust_buf.data.put_array_of_char @rust_buf.len, value.bytes
+    end
+  end
+
+  {% for typ in ci.iter_types() -%}
+  {%- let canonical_type_name = typ.canonical_name().borrow()|class_name_rb -%}
+  {%- match typ -%}
+
+  {% when Type::Int8 -%}
+
+  def write_I8(v)
+    pack_into(1, 'c', v)
+  end
+
+  {% when Type::UInt8 -%}
+
+  def write_U8(v)
+    pack_into(1, 'c', v)
+  end
+
+  {% when Type::Int16 -%}
+
+  def write_I16(v)
+    pack_into(2, 's>', v)
+  end
+
+  {% when Type::UInt16 -%}
+
+  def write_U16(v)
+    pack_into(2, 'S>', v)
+  end
+
+  {% when Type::Int32 -%}
+
+  def write_I32(v)
+    pack_into(4, 'l>', v)
+  end
+
+  {% when Type::UInt32 -%}
+
+  def write_U32(v)
+    pack_into(4, 'L>', v)
+  end
+
+  {% when Type::Int64 -%}
+
+  def write_I64(v)
+    pack_into(8, 'q>', v)
+  end
+
+  {% when Type::UInt64 -%}
+
+  def write_U64(v)
+    pack_into(8, 'Q>', v)
+  end
+
+  {% when Type::Float32 -%}
+
+  def write_F32(v)
+    pack_into(4, 'g', v)
+  end
+
+  {% when Type::Float64 -%}
+
+  def write_F64(v)
+    pack_into(8, 'G', v)
+  end
+
+  {% when Type::Boolean -%}
+
+  def write_Bool(v)
+    pack_into(1, 'c', v ? 1 : 0)
+  end
+
+  {% when Type::String -%}
+
+  def write_String(v)
+    v = v.to_s
+    pack_into 4, 'l>', v.bytes.size
+    write v
+  end
+
+  {% when Type::Timestamp -%}
+  # The Timestamp type.
+  ONE_SECOND_IN_NANOSECONDS = 10**9
+
+  def write_{{ canonical_type_name }}(v)
+    seconds = v.tv_sec
+    nanoseconds = v.tv_nsec
+
+    if seconds < 0
+      nanoseconds = ONE_SECOND_IN_NANOSECONDS - nanoseconds
+    end
+
+    pack_into 8, 'q>', seconds
+    pack_into 4, 'L>', nanoseconds
+  end
+
+  {% when Type::Duration -%}
+  # The Duration type.
+
+  def write_{{ canonical_type_name }}(v)
+    seconds = v.tv_sec
+    nanoseconds = v.tv_nsec
+
+    raise ArgumentError, 'Invalid duration, must be non-negative' if seconds < 0
+
+    pack_into 8, 'Q>', seconds
+    pack_into 4, 'L>', nanoseconds
+  end
+
+  {% when Type::Object with (object_name) -%}
+  # The Object type {{ object_name }}.
+
+  def write_{{ canonical_type_name }}(obj)
+    pointer = {{ object_name|class_name_rb}}._uniffi_lower obj
+    pack_into(8, 'Q>', pointer.address)
+  end
+
+  {% when Type::Enum with (enum_name) -%}
+  {%- let e = ci.get_enum_definition(enum_name).unwrap() -%}
+  # The Enum type {{ enum_name }}.
+
+  def write_{{ canonical_type_name }}(v)
+    {%- if e.is_flat() %}
+    pack_into(4, 'l>', v)
+    {%- else -%}
+    {%- for variant in e.variants() %}
+    if v.{{ variant.name()|var_name_rb }}?
+      pack_into(4, 'l>', {{ loop.index }})
+      {%- for field in variant.fields() %}
+      self.write_{{ field.type_().canonical_name().borrow()|class_name_rb }}(v.{{ field.name() }})
+      {%- endfor %}
+    end
+    {%- endfor %}
+    {%- endif %}
+ end
+
+  {% when Type::Record with (record_name) -%}
+  {%- let rec = ci.get_record_definition(record_name).unwrap() -%}
+  # The Record type {{ record_name }}.
+
+  def write_{{ canonical_type_name }}(v)
+    {%- for field in rec.fields() %}
+    self.write_{{ field.type_().canonical_name().borrow()|class_name_rb }}(v.{{ field.name()|var_name_rb }})
+    {%- endfor %}
+  end
+
+  {% when Type::Optional with (inner_type) -%}
+  # The Optional<T> type for {{ inner_type.canonical_name() }}.
+
+  def write_{{ canonical_type_name }}(v)
+    if v.nil?
+      pack_into(1, 'c', 0)
+    else
+      pack_into(1, 'c', 1)
+      self.write_{{ inner_type.canonical_name().borrow()|class_name_rb }}(v)
+    end
+  end
+
+  {% when Type::Sequence with (inner_type) -%}
+  # The Sequence<T> type for {{ inner_type.canonical_name() }}.
+
+  def write_{{ canonical_type_name }}(items)
+    pack_into(4, 'l>', items.size)
+
+    items.each do |item|
+      self.write_{{ inner_type.canonical_name().borrow()|class_name_rb }}(item)
+    end
+  end
+
+  {% when Type::Map with (k, inner_type) -%}
+  # The Map<T> type for {{ inner_type.canonical_name() }}.
+
+  def write_{{ canonical_type_name }}(items)
+    pack_into(4, 'l>', items.size)
+
+    items.each do |k, v|
+      write_String(k)
+      self.write_{{ inner_type.canonical_name().borrow()|class_name_rb }}(v)
+    end
+  end
+
+  {%- else -%}
+  # This type is not yet supported in the Ruby backend.
+  def write_{{ canonical_type_name }}(v)
+    raise InternalError('RustBufferStream.write() not implemented yet for {{ canonical_type_name }}')
+  end
+
+  {%- endmatch -%}
+  {%- endfor %}
+
+  private
+
+  def reserve(num_bytes)
+    if @rust_buf.len + num_bytes > @rust_buf.capacity
+      @rust_buf = RustBuffer.reserve(@rust_buf, num_bytes)
+    end
+
+    yield
+
+    @rust_buf.len += num_bytes
+  end
+
+  def pack_into(size, format, value)
+    reserve(size) do
+      @rust_buf.data.put_array_of_char @rust_buf.len, [value].pack(format).bytes
+    end
+  end
+end
+
+private_constant :RustBufferBuilder
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferStream.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferStream.rb
new file mode 100644
index 0000000000..7f6a7e23c8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferStream.rb
@@ -0,0 +1,292 @@
+
+# Helper for structured reading of values from a RustBuffer.
+class RustBufferStream
+
+  def initialize(rbuf)
+    @rbuf = rbuf
+    @offset = 0
+  end
+
+  def remaining
+    @rbuf.len - @offset
+  end
+
+  def read(size)
+    raise InternalError, 'read past end of rust buffer' if @offset + size > @rbuf.len
+
+    data = @rbuf.data.get_bytes @offset, size
+
+    @offset += size
+
+    data
+  end
+
+  {% for typ in ci.iter_types() -%}
+  {%- let canonical_type_name = typ.canonical_name().borrow()|class_name_rb -%}
+  {%- match typ -%}
+
+  {% when Type::Int8 -%}
+
+  def readI8
+    unpack_from 1, 'c'
+  end
+
+  {% when Type::UInt8 -%}
+
+  def readU8
+    unpack_from 1, 'c'
+  end
+
+  {% when Type::Int16 -%}
+
+  def readI16
+    unpack_from 2, 's>'
+  end
+
+  {% when Type::UInt16 -%}
+
+  def readU16
+    unpack_from 2, 'S>'
+  end
+
+  {% when Type::Int32 -%}
+
+  def readI32
+    unpack_from 4, 'l>'
+  end
+
+  {% when Type::UInt32 -%}
+
+  def readU32
+    unpack_from 4, 'L>'
+  end
+
+  {% when Type::Int64 -%}
+
+  def readI64
+    unpack_from 8, 'q>'
+  end
+
+  {% when Type::UInt64 -%}
+
+  def readU64
+    unpack_from 8, 'Q>'
+  end
+
+  {% when Type::Float32 -%}
+
+  def readF32
+    unpack_from 4, 'g'
+  end
+
+  {% when Type::Float64 -%}
+
+  def readF64
+    unpack_from 8, 'G'
+  end
+
+  {% when Type::Boolean -%}
+
+  def readBool
+    v = unpack_from 1, 'c'
+
+    return false if v == 0
+    return true if v == 1
+
+    raise InternalError, 'Unexpected byte for Boolean type'
+  end
+
+  {% when Type::String -%}
+
+  def readString
+    size = unpack_from 4, 'l>'
+
+    raise InternalError, 'Unexpected negative string length' if size.negative?
+
+    read(size).force_encoding(Encoding::UTF_8)
+  end
+
+  {% when Type::Timestamp -%}
+  # The Timestamp type.
+  ONE_SECOND_IN_NANOSECONDS = 10**9
+
+  def read{{ canonical_type_name }}
+    seconds = unpack_from 8, 'q>'
+    nanoseconds = unpack_from 4, 'L>'
+
+    if seconds < 0
+      nanoseconds = ONE_SECOND_IN_NANOSECONDS - nanoseconds
+    end
+
+    Time.at(seconds, nanoseconds, :nanosecond, in: '+00:00').utc
+  end
+
+  {% when Type::Duration -%}
+  # The Duration type.
+
+  def read{{ canonical_type_name }}
+    seconds = unpack_from 8, 'q>'
+    nanoseconds = unpack_from 4, 'L>'
+
+    Time.at(seconds, nanoseconds, :nanosecond, in: '+00:00').utc
+  end
+
+  {% when Type::Object with (object_name) -%}
+  # The Object type {{ object_name }}.
+
+  def read{{ canonical_type_name }}
+    pointer = FFI::Pointer.new unpack_from 8, 'Q>'
+    return {{ object_name|class_name_rb }}._uniffi_allocate(pointer)
+  end
+
+  {% when Type::Enum with (enum_name) -%}
+  {%- let e = ci.get_enum_definition(enum_name).unwrap() -%}
+  # The Enum type {{ enum_name }}.
+
+  def read{{ canonical_type_name }}
+    variant = unpack_from 4, 'l>'
+    {% if e.is_flat() -%}
+    {%- for variant in e.variants() %}
+    if variant == {{ loop.index }}
+      return {{ enum_name|class_name_rb }}::{{ variant.name()|enum_name_rb }}
+    end
+    {%- endfor %}
+
+    raise InternalError, 'Unexpected variant tag for {{ canonical_type_name }}'
+    {%- else -%}
+    {%- for variant in e.variants() %}
+    if variant == {{ loop.index }}
+        {%- if variant.has_fields() %}
+        return {{ enum_name|class_name_rb }}::{{ variant.name()|enum_name_rb }}.new(
+            {%- for field in variant.fields() %}
+            self.read{{ field.type_().canonical_name().borrow()|class_name_rb }}(){% if loop.last %}{% else %},{% endif %}
+            {%- endfor %}
+        )
+        {%- else %}
+        return {{ enum_name|class_name_rb }}::{{ variant.name()|enum_name_rb }}.new
+        {% endif %}
+    end
+    {%- endfor %}
+    raise InternalError, 'Unexpected variant tag for {{ canonical_type_name }}'
+    {%- endif %}
+  end
+
+  {% when Type::Error with (error_name) -%}
+  {%- let e = ci.get_error_definition(error_name).unwrap().wrapped_enum() %}
+
+  # The Error type {{ error_name }}
+
+  def read{{ canonical_type_name }}
+    variant = unpack_from 4, 'l>'
+    {% if e.is_flat() -%}
+    {%- for variant in e.variants() %}
+    if variant == {{ loop.index }}
+      return {{ error_name|class_name_rb }}::{{ variant.name()|class_name_rb }}.new(
+        readString()
+      )
+    end
+    {%- endfor %}
+
+    raise InternalError, 'Unexpected variant tag for {{ canonical_type_name }}'
+    {%- else -%}
+    {%- for variant in e.variants() %}
+    if variant == {{ loop.index }}
+        {%- if variant.has_fields() %}
+        return {{ error_name|class_name_rb }}::{{ variant.name()|class_name_rb }}.new(
+            {%- for field in variant.fields() %}
+            read{{ field.type_().canonical_name().borrow()|class_name_rb }}(){% if loop.last %}{% else %},{% endif %}
+            {%- endfor %}
+        )
+        {%- else %}
+        return {{ error_name|class_name_rb }}::{{ variant.name()|class_name_rb }}.new
+        {%- endif %}
+    end
+    {%- endfor %}
+
+    raise InternalError, 'Unexpected variant tag for {{ canonical_type_name }}'
+    {%- endif %}
+  end
+
+  {% when Type::Record with (record_name) -%}
+  {%- let rec = ci.get_record_definition(record_name).unwrap() -%}
+  # The Record type {{ record_name }}.
+
+  def read{{ canonical_type_name }}
+    {{ rec.name()|class_name_rb }}.new(
+      {%- for field in rec.fields() %}
+      read{{ field.type_().canonical_name().borrow()|class_name_rb }}{% if loop.last %}{% else %},{% endif %}
+      {%- endfor %}
+    )
+  end
+
+  {% when Type::Optional with (inner_type) -%}
+  # The Optional<T> type for {{ inner_type.canonical_name() }}.
+
+  def read{{ canonical_type_name }}
+    flag = unpack_from 1, 'c'
+
+    if flag == 0
+      return nil
+    elsif flag == 1
+      return read{{ inner_type.canonical_name().borrow()|class_name_rb }}
+    else
+      raise InternalError, 'Unexpected flag byte for {{ canonical_type_name }}'
+    end
+  end
+
+  {% when Type::Sequence with (inner_type) -%}
+  # The Sequence<T> type for {{ inner_type.canonical_name() }}.
+
+  def read{{ canonical_type_name }}
+    count = unpack_from 4, 'l>'
+
+    raise InternalError, 'Unexpected negative sequence length' if count.negative?
+
+    items = []
+
+    count.times do
+      items.append read{{ inner_type.canonical_name().borrow()|class_name_rb }}
+    end
+
+    items
+  end
+
+  {% when Type::Map with (k, inner_type) -%}
+  # The Map<T> type for {{ inner_type.canonical_name() }}.
+
+  def read{{ canonical_type_name }}
+    count = unpack_from 4, 'l>'
+    raise InternalError, 'Unexpected negative map size' if count.negative?
+
+    items = {}
+    count.times do
+      key = readString
+      items[key] = read{{ inner_type.canonical_name().borrow()|class_name_rb }}
+    end
+
+    items
+  end
+  {%- else -%}
+  # This type is not yet supported in the Ruby backend.
+  def read{{ canonical_type_name }}
+    raise InternalError, 'RustBufferStream.read not implemented yet for {{ canonical_type_name }}'
+  end
+
+  {%- endmatch -%}
+  {%- endfor %}
+
+  def unpack_from(size, format)
+    raise InternalError, 'read past end of rust buffer' if @offset + size > @rbuf.len
+
+    value = @rbuf.data.get_bytes(@offset, size).unpack format
+
+    @offset += size
+
+    # TODO: verify this
+    raise 'more than one element!!!' if value.size > 1
+
+    value[0]
+  end
+end
+
+private_constant :RustBufferStream
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferTemplate.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferTemplate.rb
new file mode 100644
index 0000000000..deed864572
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/RustBufferTemplate.rb
@@ -0,0 +1,218 @@
+class RustBuffer < FFI::Struct
+  layout :capacity, :int32,
+         :len,      :int32,
+         :data,     :pointer
+
+  def self.alloc(size)
+    return {{ ci.namespace()|class_name_rb }}.rust_call(:{{ ci.ffi_rustbuffer_alloc().name() }}, size)
+  end
+
+  def self.reserve(rbuf, additional)
+    return {{ ci.namespace()|class_name_rb }}.rust_call(:{{ ci.ffi_rustbuffer_reserve().name() }}, rbuf, additional)
+  end
+
+  def free
+    {{ ci.namespace()|class_name_rb }}.rust_call(:{{ ci.ffi_rustbuffer_free().name() }}, self)
+  end
+
+  def capacity
+    self[:capacity]
+  end
+
+  def len
+    self[:len]
+  end
+
+  def len=(value)
+    self[:len] = value
+  end
+
+  def data
+    self[:data]
+  end
+
+  def to_s
+    "RustBuffer(capacity=#{capacity}, len=#{len}, data=#{data.read_bytes len})"
+  end
+
+  # The allocated buffer will be automatically freed if an error occurs, ensuring that
+  # we don't accidentally leak it.
+  def self.allocWithBuilder
+    builder = RustBufferBuilder.new
+
+    begin
+      yield builder
+    rescue => e
+      builder.discard
+      raise e
+    end
+  end
+
+  # The RustBuffer will be freed once the context-manager exits, ensuring that we don't
+  # leak it even if an error occurs.
+  def consumeWithStream
+    stream = RustBufferStream.new self
+
+    yield stream
+
+    raise RuntimeError, 'junk data left in buffer after consuming' if stream.remaining != 0
+  ensure
+    free
+  end
+
+  {%- for typ in ci.iter_types() -%}
+  {%- let canonical_type_name = typ.canonical_name() -%}
+  {%- match typ -%}
+
+  {% when Type::String -%}
+  # The primitive String type.
+
+  def self.allocFromString(value)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write value.encode('utf-8')
+      return builder.finalize
+    end
+  end
+
+  def consumeIntoString
+    consumeWithStream do |stream|
+      return stream.read(stream.remaining).force_encoding(Encoding::UTF_8)
+    end
+  end
+
+  {% when Type::Timestamp -%}
+  def self.alloc_from_{{ canonical_type_name }}(v)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write_{{ canonical_type_name }}(v)
+      return builder.finalize
+    end
+  end
+
+  def consumeInto{{ canonical_type_name }}
+    consumeWithStream do |stream|
+      return stream.read{{ canonical_type_name }}
+    end
+  end
+
+  {% when Type::Duration -%}
+  def self.alloc_from_{{ canonical_type_name }}(v)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write_{{ canonical_type_name }}(v)
+      return builder.finalize
+    end
+  end
+
+  def consumeInto{{ canonical_type_name }}
+    consumeWithStream do |stream|
+      return stream.read{{ canonical_type_name }}
+    end
+  end
+
+  {% when Type::Record with (record_name) -%}
+  {%- let rec = ci.get_record_definition(record_name).unwrap() -%}
+  # The Record type {{ record_name }}.
+
+  def self.alloc_from_{{ canonical_type_name }}(v)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write_{{ canonical_type_name }}(v)
+      return builder.finalize
+    end
+  end
+
+  def consumeInto{{ canonical_type_name }}
+    consumeWithStream do |stream|
+      return stream.read{{ canonical_type_name }}
+    end
+  end
+
+  {% when Type::Enum with (enum_name) -%}
+  {%- let e = ci.get_enum_definition(enum_name).unwrap() -%}
+  # The Enum type {{ enum_name }}.
+
+  def self.alloc_from_{{ canonical_type_name }}(v)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write_{{ canonical_type_name }}(v)
+      return builder.finalize
+    end
+  end
+
+  def consumeInto{{ canonical_type_name }}
+    consumeWithStream do |stream|
+      return stream.read{{ canonical_type_name }}
+    end
+  end
+
+  {% when Type::Optional with (inner_type) -%}
+  # The Optional<T> type for {{ inner_type.canonical_name() }}.
+
+  def self.alloc_from_{{ canonical_type_name }}(v)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write_{{ canonical_type_name }}(v)
+      return builder.finalize()
+    end
+  end
+
+  def consumeInto{{ canonical_type_name }}
+    consumeWithStream do |stream|
+      return stream.read{{ canonical_type_name }}
+    end
+  end
+
+  {% when Type::Sequence with (inner_type) -%}
+  # The Sequence<T> type for {{ inner_type.canonical_name() }}.
+
+  def self.alloc_from_{{ canonical_type_name }}(v)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write_{{ canonical_type_name }}(v)
+      return builder.finalize()
+    end
+  end
+
+  def consumeInto{{ canonical_type_name }}
+    consumeWithStream do |stream|
+      return stream.read{{ canonical_type_name }}
+    end
+  end
+
+  {% when Type::Map with (k, inner_type) -%}
+  # The Map<T> type for {{ inner_type.canonical_name() }}.
+
+  def self.alloc_from_{{ canonical_type_name }}(v)
+    RustBuffer.allocWithBuilder do |builder|
+      builder.write_{{ canonical_type_name }}(v)
+      return builder.finalize
+    end
+  end
+
+  def consumeInto{{ canonical_type_name }}
+    consumeWithStream do |stream|
+      return stream.read{{ canonical_type_name }}
+    end
+  end
+
+  {%- else -%}
+  {#- No code emitted for types that don't lower into a RustBuffer -#}
+  {%- endmatch -%}
+  {%- endfor %}
+end
+
+module UniFFILib
+  class ForeignBytes < FFI::Struct
+    layout :len,      :int32,
+           :data,     :pointer
+
+    def len
+      self[:len]
+    end
+
+    def data
+      self[:data]
+    end
+
+    def to_s
+      "ForeignBytes(len=#{len}, data=#{data.read_bytes(len)})"
+    end
+  end
+end
+
+private_constant :UniFFILib
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/TopLevelFunctionTemplate.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/TopLevelFunctionTemplate.rb
new file mode 100644
index 0000000000..13214cf31b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/TopLevelFunctionTemplate.rb
@@ -0,0 +1,16 @@
+{%- match func.return_type() -%}
+{%- when Some with (return_type) %}
+
+def self.{{ func.name()|fn_name_rb }}({%- call rb::arg_list_decl(func) -%})
+  {%- call rb::coerce_args(func) %}
+  result = {% call rb::to_ffi_call(func) %}
+  return {{ "result"|lift_rb(return_type) }}
+end
+
+{% when None %}
+
+def self.{{ func.name()|fn_name_rb }}({%- call rb::arg_list_decl(func) -%})
+  {%- call rb::coerce_args(func) %}
+  {% call rb::to_ffi_call(func) %}
+end
+{% endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/macros.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/macros.rb
new file mode 100644
index 0000000000..0ec50df2c8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/macros.rb
@@ -0,0 +1,73 @@
+{#
+// Template to call into rust. Used in several places.
+// Variable names in `arg_list_decl` should match up with arg lists
+// passed to rust via `_arg_list_ffi_call` (we use  `var_name_rb` in `lower_rb`)
+#}
+
+{%- macro to_ffi_call(func) -%}
+    {%- match func.throws_name() -%}
+    {%- when Some with (e) -%}
+      {{ ci.namespace()|class_name_rb }}.rust_call_with_error({{ e|class_name_rb }},
+    {%- else -%}
+      {{ ci.namespace()|class_name_rb }}.rust_call(
+    {%- endmatch -%}
+    :{{ func.ffi_func().name() }},
+    {%- call _arg_list_ffi_call(func) -%}
+)
+{%- endmacro -%}
+
+{%- macro to_ffi_call_with_prefix(prefix, func) -%}
+    {%- match func.throws_name() -%}
+    {%- when Some with (e) -%}
+      {{ ci.namespace()|class_name_rb }}.rust_call_with_error({{ e|class_name_rb }},
+    {%- else -%}
+      {{ ci.namespace()|class_name_rb }}.rust_call(
+    {%- endmatch -%}
+    :{{ func.ffi_func().name() }},
+    {{- prefix }},
+    {%- call _arg_list_ffi_call(func) -%}
+)
+{%- endmacro -%}
+
+{%- macro _arg_list_ffi_call(func) %}
+    {%- for arg in func.arguments() %}
+        {{- arg.name()|lower_rb(arg.type_().borrow()) }}
+        {%- if !loop.last %},{% endif %}
+    {%- endfor %}
+{%- endmacro -%}
+
+{#-
+// Arglist as used in Ruby declarations of methods, functions and constructors.
+// Note the var_name_rb and type_rb filters.
+-#}
+
+{% macro arg_list_decl(func) %}
+    {%- for arg in func.arguments() -%}
+        {{ arg.name()|var_name_rb }}
+        {%- match arg.default_value() %}
+        {%- when Some with(literal) %} = {{ literal|literal_rb }}
+        {%- else %}
+        {%- endmatch %}
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+
+{#-
+// Arglist as used in the UniFFILib function declations.
+// Note unfiltered name but type_ffi filters.
+-#}
+{%- macro arg_list_ffi_decl(func) %}
+    [{%- for arg in func.arguments() -%}{{ arg.type_().borrow()|type_ffi }}, {% endfor -%} RustCallStatus.by_ref]
+{%- endmacro -%}
+
+{%- macro coerce_args(func) %}
+    {%- for arg in func.arguments() %}
+    {{ arg.name() }} = {{ arg.name()|coerce_rb(arg.type_().borrow()) -}}
+    {% endfor -%}
+{%- endmacro -%}
+
+{%- macro coerce_args_extra_indent(func) %}
+        {%- for arg in func.arguments() %}
+        {{ arg.name() }} = {{ arg.name()|coerce_rb(arg.type_().borrow()) }}
+        {%- endfor %}
+{%- endmacro -%}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/wrapper.rb b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/wrapper.rb
new file mode 100644
index 0000000000..72cb60f73f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/ruby/templates/wrapper.rb
@@ -0,0 +1,47 @@
+# This file was autogenerated by some hot garbage in the `uniffi` crate.
+# Trust me, you don't want to mess with it!
+
+# Common helper code.
+#
+# Ideally this would live in a separate .rb file where it can be unittested etc
+# in isolation, and perhaps even published as a re-useable package.
+#
+# However, it's important that the detils of how this helper code works (e.g. the
+# way that different builtin types are passed across the FFI) exactly match what's
+# expected by the rust code on the other side of the interface. In practice right
+# now that means coming from the exact some version of `uniffi` that was used to
+# compile the rust component. The easiest way to ensure this is to bundle the Ruby
+# helpers directly inline like we're doing here.
+
+require 'ffi'
+
+module {{ ci.namespace()|class_name_rb }}
+  {% include "RustBufferTemplate.rb" %}
+  {% include "RustBufferStream.rb" %}
+  {% include "RustBufferBuilder.rb" %}
+
+  # Error definitions
+  {% include "ErrorTemplate.rb" %}
+
+  {% include "NamespaceLibraryTemplate.rb" %}
+
+  # Public interface members begin here.
+
+  {% for e in ci.enum_definitions() %}
+  {% include "EnumTemplate.rb" %}
+  {%- endfor -%}
+
+  {%- for rec in ci.record_definitions() %}
+  {% include "RecordTemplate.rb" %}
+  {% endfor %}
+
+  {% for func in ci.function_definitions() %}
+  {% include "TopLevelFunctionTemplate.rb" %}
+  {% endfor %}
+
+  {% for obj in ci.object_definitions() %}
+  {% include "ObjectTemplate.rb" %}
+  {% endfor %}
+end
+
+{% import "macros.rb" as rb %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/callback_interface.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/callback_interface.rs
new file mode 100644
index 0000000000..828a8823ee
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/callback_interface.rs
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct CallbackInterfaceCodeType {
+    id: String,
+}
+
+impl CallbackInterfaceCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for CallbackInterfaceCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!("CallbackInterface{}", self.type_label(oracle))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/compounds.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/compounds.rs
new file mode 100644
index 0000000000..f91be9ce54
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/compounds.rs
@@ -0,0 +1,98 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal, TypeIdentifier};
+
+pub struct OptionalCodeType {
+    inner: TypeIdentifier,
+}
+
+impl OptionalCodeType {
+    pub fn new(inner: TypeIdentifier) -> Self {
+        Self { inner }
+    }
+}
+
+impl CodeType for OptionalCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        format!("{}?", oracle.find(&self.inner).type_label(oracle))
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!("Option{}", oracle.find(&self.inner).canonical_name(oracle))
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        match literal {
+            Literal::Null => "nil".into(),
+            _ => oracle.find(&self.inner).literal(oracle, literal),
+        }
+    }
+}
+
+pub struct SequenceCodeType {
+    inner: TypeIdentifier,
+}
+
+impl SequenceCodeType {
+    pub fn new(inner: TypeIdentifier) -> Self {
+        Self { inner }
+    }
+}
+
+impl CodeType for SequenceCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        format!("[{}]", oracle.find(&self.inner).type_label(oracle))
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Sequence{}",
+            oracle.find(&self.inner).canonical_name(oracle)
+        )
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        match literal {
+            Literal::EmptySequence => "[]".into(),
+            _ => unreachable!(),
+        }
+    }
+}
+
+pub struct MapCodeType {
+    key: TypeIdentifier,
+    value: TypeIdentifier,
+}
+
+impl MapCodeType {
+    pub fn new(key: TypeIdentifier, value: TypeIdentifier) -> Self {
+        Self { key, value }
+    }
+}
+
+impl CodeType for MapCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "[{}: {}]",
+            oracle.find(&self.key).type_label(oracle),
+            oracle.find(&self.value).type_label(oracle)
+        )
+    }
+
+    fn canonical_name(&self, oracle: &dyn CodeOracle) -> String {
+        format!(
+            "Dictionary{}{}",
+            oracle.find(&self.key).canonical_name(oracle),
+            oracle.find(&self.value).canonical_name(oracle)
+        )
+    }
+
+    fn literal(&self, _oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        match literal {
+            Literal::EmptyMap => "[:]".into(),
+            _ => unreachable!(),
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/custom.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/custom.rs
new file mode 100644
index 0000000000..bf1806e5e2
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/custom.rs
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct CustomCodeType {
+    name: String,
+}
+
+impl CustomCodeType {
+    pub fn new(name: String) -> Self {
+        CustomCodeType { name }
+    }
+}
+
+impl CodeType for CustomCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        self.name.clone()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.name)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/enum_.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/enum_.rs
new file mode 100644
index 0000000000..04d8422f6a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/enum_.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+
+pub struct EnumCodeType {
+    id: String,
+}
+
+impl EnumCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for EnumCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+
+    fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+        if let Literal::Enum(v, _) = literal {
+            format!(".{}", oracle.enum_variant_name(v))
+        } else {
+            unreachable!();
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/error.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/error.rs
new file mode 100644
index 0000000000..4219f24c39
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/error.rs
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct ErrorCodeType {
+    id: String,
+}
+
+impl ErrorCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ErrorCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/miscellany.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/miscellany.rs
new file mode 100644
index 0000000000..4f57734934
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/miscellany.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct TimestampCodeType;
+
+impl CodeType for TimestampCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        "Date".into()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        "Timestamp".into()
+    }
+}
+
+pub struct DurationCodeType;
+
+impl CodeType for DurationCodeType {
+    fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+        "TimeInterval".into()
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        "Duration".into()
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/mod.rs
new file mode 100644
index 0000000000..bf55f37bee
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/mod.rs
@@ -0,0 +1,475 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::borrow::Borrow;
+use std::cell::RefCell;
+use std::collections::{BTreeSet, HashMap, HashSet};
+
+use anyhow::{Context, Result};
+use askama::Template;
+use heck::{ToLowerCamelCase, ToUpperCamelCase};
+use serde::{Deserialize, Serialize};
+
+use super::Bindings;
+use crate::backend::{CodeOracle, CodeType, TemplateExpression, TypeIdentifier};
+use crate::interface::*;
+use crate::MergeWith;
+
+mod callback_interface;
+mod compounds;
+mod custom;
+mod enum_;
+mod error;
+mod miscellany;
+mod object;
+mod primitives;
+mod record;
+
+/// Config options for the caller to customize the generated Swift.
+///
+/// Note that this can only be used to control details of the Swift *that do not affect the underlying component*,
+/// since the details of the underlying component are entirely determined by the `ComponentInterface`.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct Config {
+    cdylib_name: Option<String>,
+    module_name: Option<String>,
+    ffi_module_name: Option<String>,
+    ffi_module_filename: Option<String>,
+    generate_module_map: Option<bool>,
+    omit_argument_labels: Option<bool>,
+    #[serde(default)]
+    custom_types: HashMap<String, CustomTypeConfig>,
+}
+
+#[derive(Debug, Default, Clone, Serialize, Deserialize)]
+pub struct CustomTypeConfig {
+    imports: Option<Vec<String>>,
+    type_name: Option<String>,
+    into_custom: TemplateExpression,
+    from_custom: TemplateExpression,
+}
+
+impl Config {
+    /// The name of the Swift module containing the high-level foreign-language bindings.
+    pub fn module_name(&self) -> String {
+        match self.module_name.as_ref() {
+            Some(name) => name.clone(),
+            None => "uniffi".into(),
+        }
+    }
+
+    /// The name of the lower-level C module containing the FFI declarations.
+    pub fn ffi_module_name(&self) -> String {
+        match self.ffi_module_name.as_ref() {
+            Some(name) => name.clone(),
+            None => format!("{}FFI", self.module_name()),
+        }
+    }
+
+    /// The filename stem for the lower-level C module containing the FFI declarations.
+    pub fn ffi_module_filename(&self) -> String {
+        match self.ffi_module_filename.as_ref() {
+            Some(name) => name.clone(),
+            None => self.ffi_module_name(),
+        }
+    }
+
+    /// The name of the `.modulemap` file for the lower-level C module with FFI declarations.
+    pub fn modulemap_filename(&self) -> String {
+        format!("{}.modulemap", self.ffi_module_filename())
+    }
+
+    /// The name of the `.h` file for the lower-level C module with FFI declarations.
+    pub fn header_filename(&self) -> String {
+        format!("{}.h", self.ffi_module_filename())
+    }
+
+    /// The name of the compiled Rust library containing the FFI implementation.
+    pub fn cdylib_name(&self) -> String {
+        if let Some(cdylib_name) = &self.cdylib_name {
+            cdylib_name.clone()
+        } else {
+            "uniffi".into()
+        }
+    }
+
+    /// Whether to generate a `.modulemap` file for the lower-level C module with FFI declarations.
+    pub fn generate_module_map(&self) -> bool {
+        self.generate_module_map.unwrap_or(true)
+    }
+
+    /// Whether to omit argument labels in Swift function definitions.
+    pub fn omit_argument_labels(&self) -> bool {
+        self.omit_argument_labels.unwrap_or(false)
+    }
+}
+
+impl From<&ComponentInterface> for Config {
+    fn from(ci: &ComponentInterface) -> Self {
+        Config {
+            module_name: Some(ci.namespace().into()),
+            cdylib_name: Some(format!("uniffi_{}", ci.namespace())),
+            ..Default::default()
+        }
+    }
+}
+
+impl MergeWith for Config {
+    fn merge_with(&self, other: &Self) -> Self {
+        Config {
+            module_name: self.module_name.merge_with(&other.module_name),
+            ffi_module_name: self.ffi_module_name.merge_with(&other.ffi_module_name),
+            cdylib_name: self.cdylib_name.merge_with(&other.cdylib_name),
+            ffi_module_filename: self
+                .ffi_module_filename
+                .merge_with(&other.ffi_module_filename),
+            generate_module_map: self
+                .generate_module_map
+                .merge_with(&other.generate_module_map),
+            omit_argument_labels: self
+                .omit_argument_labels
+                .merge_with(&other.omit_argument_labels),
+            custom_types: self.custom_types.merge_with(&other.custom_types),
+        }
+    }
+}
+
+/// Generate UniFFI component bindings for Swift, as strings in memory.
+///
+pub fn generate_bindings(config: &Config, ci: &ComponentInterface) -> Result<Bindings> {
+    let header = BridgingHeader::new(config, ci)
+        .render()
+        .context("failed to render Swift bridging header")?;
+    let library = SwiftWrapper::new(config.clone(), ci)
+        .render()
+        .context("failed to render Swift library")?;
+    let modulemap = if config.generate_module_map() {
+        Some(
+            ModuleMap::new(config, ci)
+                .render()
+                .context("failed to render Swift modulemap")?,
+        )
+    } else {
+        None
+    };
+    Ok(Bindings {
+        library,
+        header,
+        modulemap,
+    })
+}
+
+/// Renders Swift helper code for all types
+///
+/// This template is a bit different than others in that it stores internal state from the render
+/// process.  Make sure to only call `render()` once.
+#[derive(Template)]
+#[template(syntax = "kt", escape = "none", path = "Types.swift")]
+pub struct TypeRenderer<'a> {
+    config: &'a Config,
+    ci: &'a ComponentInterface,
+    // Track included modules for the `include_once()` macro
+    include_once_names: RefCell<HashSet<String>>,
+    // Track imports added with the `add_import()` macro
+    imports: RefCell<BTreeSet<String>>,
+}
+
+impl<'a> TypeRenderer<'a> {
+    fn new(config: &'a Config, ci: &'a ComponentInterface) -> Self {
+        Self {
+            config,
+            ci,
+            include_once_names: RefCell::new(HashSet::new()),
+            imports: RefCell::new(BTreeSet::new()),
+        }
+    }
+
+    // The following methods are used by the `Types.kt` macros.
+
+    // Helper for the including a template, but only once.
+    //
+    // The first time this is called with a name it will return true, indicating that we should
+    // include the template.  Subsequent calls will return false.
+    fn include_once_check(&self, name: &str) -> bool {
+        self.include_once_names
+            .borrow_mut()
+            .insert(name.to_string())
+    }
+
+    // Helper to add an import statement
+    //
+    // Call this inside your template to cause an import statement to be added at the top of the
+    // file.  Imports will be sorted and de-deuped.
+    //
+    // Returns an empty string so that it can be used inside an askama `{{ }}` block.
+    fn add_import(&self, name: &str) -> &str {
+        self.imports.borrow_mut().insert(name.to_owned());
+        ""
+    }
+}
+
+/// Template for generating the `.h` file that defines the low-level C FFI.
+///
+/// This file defines only the low-level structs and functions that are exposed
+/// by the compiled Rust code. It gets wrapped into a higher-level API by the
+/// code from [`SwiftWrapper`].
+#[derive(Template)]
+#[template(syntax = "c", escape = "none", path = "BridgingHeaderTemplate.h")]
+pub struct BridgingHeader<'config, 'ci> {
+    _config: &'config Config,
+    ci: &'ci ComponentInterface,
+}
+
+impl<'config, 'ci> BridgingHeader<'config, 'ci> {
+    pub fn new(config: &'config Config, ci: &'ci ComponentInterface) -> Self {
+        Self {
+            _config: config,
+            ci,
+        }
+    }
+}
+
+/// Template for generating the `.modulemap` file that exposes the low-level C FFI.
+///
+/// This file defines how the low-level C FFI from [`BridgingHeader`] gets exposed
+/// as a Swift module that can be called by other Swift code. In our case, its only
+/// job is to define the *name* of the Swift module that will contain the FFI functions
+/// so that it can be imported by the higher-level code in from [`SwiftWrapper`].
+#[derive(Template)]
+#[template(syntax = "c", escape = "none", path = "ModuleMapTemplate.modulemap")]
+pub struct ModuleMap<'config, 'ci> {
+    config: &'config Config,
+    _ci: &'ci ComponentInterface,
+}
+
+impl<'config, 'ci> ModuleMap<'config, 'ci> {
+    pub fn new(config: &'config Config, _ci: &'ci ComponentInterface) -> Self {
+        Self { config, _ci }
+    }
+}
+
+#[derive(Template)]
+#[template(syntax = "swift", escape = "none", path = "wrapper.swift")]
+pub struct SwiftWrapper<'a> {
+    config: Config,
+    ci: &'a ComponentInterface,
+    type_helper_code: String,
+    type_imports: BTreeSet<String>,
+}
+impl<'a> SwiftWrapper<'a> {
+    pub fn new(config: Config, ci: &'a ComponentInterface) -> Self {
+        let type_renderer = TypeRenderer::new(&config, ci);
+        let type_helper_code = type_renderer.render().unwrap();
+        let type_imports = type_renderer.imports.into_inner();
+        Self {
+            config,
+            ci,
+            type_helper_code,
+            type_imports,
+        }
+    }
+
+    pub fn imports(&self) -> Vec<String> {
+        self.type_imports.iter().cloned().collect()
+    }
+
+    pub fn initialization_fns(&self) -> Vec<String> {
+        self.ci
+            .iter_types()
+            .into_iter()
+            .filter_map(|t| t.initialization_fn(&SwiftCodeOracle))
+            .collect()
+    }
+}
+
+#[derive(Clone)]
+pub struct SwiftCodeOracle;
+
+impl SwiftCodeOracle {
+    // Map `Type` instances to a `Box<dyn CodeType>` for that type.
+    //
+    // There is a companion match in `templates/Types.swift` which performs a similar function for the
+    // template code.
+    //
+    //   - When adding additional types here, make sure to also add a match arm to the `Types.swift` template.
+    //   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+    fn create_code_type(&self, type_: TypeIdentifier) -> Box<dyn CodeType> {
+        match type_ {
+            Type::UInt8 => Box::new(primitives::UInt8CodeType),
+            Type::Int8 => Box::new(primitives::Int8CodeType),
+            Type::UInt16 => Box::new(primitives::UInt16CodeType),
+            Type::Int16 => Box::new(primitives::Int16CodeType),
+            Type::UInt32 => Box::new(primitives::UInt32CodeType),
+            Type::Int32 => Box::new(primitives::Int32CodeType),
+            Type::UInt64 => Box::new(primitives::UInt64CodeType),
+            Type::Int64 => Box::new(primitives::Int64CodeType),
+            Type::Float32 => Box::new(primitives::Float32CodeType),
+            Type::Float64 => Box::new(primitives::Float64CodeType),
+            Type::Boolean => Box::new(primitives::BooleanCodeType),
+            Type::String => Box::new(primitives::StringCodeType),
+
+            Type::Timestamp => Box::new(miscellany::TimestampCodeType),
+            Type::Duration => Box::new(miscellany::DurationCodeType),
+
+            Type::Enum(id) => Box::new(enum_::EnumCodeType::new(id)),
+            Type::Object(id) => Box::new(object::ObjectCodeType::new(id)),
+            Type::Record(id) => Box::new(record::RecordCodeType::new(id)),
+            Type::Error(id) => Box::new(error::ErrorCodeType::new(id)),
+            Type::CallbackInterface(id) => {
+                Box::new(callback_interface::CallbackInterfaceCodeType::new(id))
+            }
+
+            Type::Optional(inner) => Box::new(compounds::OptionalCodeType::new(*inner)),
+            Type::Sequence(inner) => Box::new(compounds::SequenceCodeType::new(*inner)),
+            Type::Map(key, value) => Box::new(compounds::MapCodeType::new(*key, *value)),
+            Type::External { .. } => panic!("no support for external types yet"),
+            Type::Custom { name, .. } => Box::new(custom::CustomCodeType::new(name)),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling create_code_type")
+            }
+        }
+    }
+}
+
+impl CodeOracle for SwiftCodeOracle {
+    fn find(&self, type_: &TypeIdentifier) -> Box<dyn CodeType> {
+        self.create_code_type(type_.clone())
+    }
+
+    /// Get the idiomatic Swift rendering of a class name (for enums, records, errors, etc).
+    fn class_name(&self, nm: &str) -> String {
+        nm.to_string().to_upper_camel_case()
+    }
+
+    /// Get the idiomatic Swift rendering of a function name.
+    fn fn_name(&self, nm: &str) -> String {
+        format!("`{}`", nm.to_string().to_lower_camel_case())
+    }
+
+    /// Get the idiomatic Swift rendering of a variable name.
+    fn var_name(&self, nm: &str) -> String {
+        format!("`{}`", nm.to_string().to_lower_camel_case())
+    }
+
+    /// Get the idiomatic Swift rendering of an individual enum variant.
+    fn enum_variant_name(&self, nm: &str) -> String {
+        format!("`{}`", nm.to_string().to_lower_camel_case())
+    }
+
+    /// Get the idiomatic Swift rendering of an exception name.
+    fn error_name(&self, nm: &str) -> String {
+        format!("`{}`", self.class_name(nm))
+    }
+
+    fn ffi_type_label(&self, ffi_type: &FFIType) -> String {
+        match ffi_type {
+            FFIType::Int8 => "int8_t".into(),
+            FFIType::UInt8 => "uint8_t".into(),
+            FFIType::Int16 => "int16_t".into(),
+            FFIType::UInt16 => "uint16_t".into(),
+            FFIType::Int32 => "int32_t".into(),
+            FFIType::UInt32 => "uint32_t".into(),
+            FFIType::Int64 => "int64_t".into(),
+            FFIType::UInt64 => "uint64_t".into(),
+            FFIType::Float32 => "float".into(),
+            FFIType::Float64 => "double".into(),
+            FFIType::RustArcPtr(_) => "void*_Nonnull".into(),
+            FFIType::RustBuffer => "RustBuffer".into(),
+            FFIType::ForeignBytes => "ForeignBytes".into(),
+            FFIType::ForeignCallback => "ForeignCallback  _Nonnull".to_string(),
+        }
+    }
+}
+
+pub mod filters {
+    use super::*;
+
+    fn oracle() -> &'static SwiftCodeOracle {
+        &SwiftCodeOracle
+    }
+
+    pub fn type_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(codetype.type_label(oracle))
+    }
+
+    pub fn canonical_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(codetype.canonical_name(oracle))
+    }
+
+    pub fn ffi_converter_name(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(codetype.ffi_converter_name(oracle()))
+    }
+
+    pub fn lower_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lower", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn write_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.write", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn lift_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.lift", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn read_fn(codetype: &impl CodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.read", codetype.ffi_converter_name(oracle())))
+    }
+
+    pub fn literal_swift(
+        literal: &Literal,
+        codetype: &impl CodeType,
+    ) -> Result<String, askama::Error> {
+        let oracle = oracle();
+        Ok(codetype.literal(oracle, literal))
+    }
+
+    /// Get the Swift syntax for representing a given low-level `FFIType`.
+    pub fn ffi_type_name(type_: &FFIType) -> Result<String, askama::Error> {
+        Ok(oracle().ffi_type_label(type_))
+    }
+
+    /// Get the type that a type is lowered into.  This is subtly different than `type_ffi`, see
+    /// #1106 for details
+    pub fn type_ffi_lowered(ffi_type: &FFIType) -> Result<String, askama::Error> {
+        Ok(match ffi_type {
+            FFIType::Int8 => "Int8".into(),
+            FFIType::UInt8 => "UInt8".into(),
+            FFIType::Int16 => "Int16".into(),
+            FFIType::UInt16 => "UInt16".into(),
+            FFIType::Int32 => "Int32".into(),
+            FFIType::UInt32 => "UInt32".into(),
+            FFIType::Int64 => "Int64".into(),
+            FFIType::UInt64 => "UInt64".into(),
+            FFIType::Float32 => "float".into(),
+            FFIType::Float64 => "double".into(),
+            FFIType::RustArcPtr(_) => "void*_Nonnull".into(),
+            FFIType::RustBuffer => "RustBuffer".into(),
+            FFIType::ForeignBytes => "ForeignBytes".into(),
+            FFIType::ForeignCallback => "ForeignCallback  _Nonnull".to_string(),
+        })
+    }
+
+    /// Get the idiomatic Swift rendering of a class name (for enums, records, errors, etc).
+    pub fn class_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().class_name(nm))
+    }
+
+    /// Get the idiomatic Swift rendering of a function name.
+    pub fn fn_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().fn_name(nm))
+    }
+
+    /// Get the idiomatic Swift rendering of a variable name.
+    pub fn var_name(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().var_name(nm))
+    }
+
+    /// Get the idiomatic Swift rendering of an individual enum variant.
+    pub fn enum_variant_swift(nm: &str) -> Result<String, askama::Error> {
+        Ok(oracle().enum_variant_name(nm))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/object.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/object.rs
new file mode 100644
index 0000000000..d227f8e7cd
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/object.rs
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct ObjectCodeType {
+    id: String,
+}
+
+impl ObjectCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for ObjectCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/primitives.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/primitives.rs
new file mode 100644
index 0000000000..4a9051fcef
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/primitives.rs
@@ -0,0 +1,87 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType, Literal};
+use crate::interface::{types::Type, Radix};
+use paste::paste;
+
+fn render_literal(oracle: &dyn CodeOracle, literal: &Literal) -> String {
+    fn typed_number(oracle: &dyn CodeOracle, type_: &Type, num_str: String) -> String {
+        match type_ {
+            // special case Int32.
+            Type::Int32 => num_str,
+            // otherwise use constructor e.g. UInt8(x)
+            Type::Int8
+            | Type::UInt8
+            | Type::Int16
+            | Type::UInt16
+            | Type::UInt32
+            | Type::Int64
+            | Type::UInt64
+            | Type::Float32
+            | Type::Float64 =>
+            // XXX we should pass in the codetype itself.
+            {
+                format!("{}({})", oracle.find(type_).type_label(oracle), num_str)
+            }
+            _ => panic!("Unexpected literal: {} is not a number", num_str),
+        }
+    }
+
+    match literal {
+        Literal::Boolean(v) => format!("{}", v),
+        Literal::String(s) => format!("\"{}\"", s),
+        Literal::Int(i, radix, type_) => typed_number(
+            oracle,
+            type_,
+            match radix {
+                Radix::Octal => format!("0o{:o}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+        ),
+        Literal::UInt(i, radix, type_) => typed_number(
+            oracle,
+            type_,
+            match radix {
+                Radix::Octal => format!("0o{:o}", i),
+                Radix::Decimal => format!("{}", i),
+                Radix::Hexadecimal => format!("{:#x}", i),
+            },
+        ),
+        Literal::Float(string, type_) => typed_number(oracle, type_, string.clone()),
+        _ => unreachable!("Literal"),
+    }
+}
+
+macro_rules! impl_code_type_for_primitive {
+    ($T:ty, $class_name:literal) => {
+        paste! {
+            pub struct $T;
+
+            impl CodeType for $T  {
+                fn type_label(&self, _oracle: &dyn CodeOracle) -> String {
+                    $class_name.into()
+                }
+
+                fn literal(&self, oracle: &dyn CodeOracle, literal: &Literal) -> String {
+                    render_literal(oracle, &literal)
+                }
+            }
+        }
+    };
+}
+
+impl_code_type_for_primitive!(BooleanCodeType, "Bool");
+impl_code_type_for_primitive!(StringCodeType, "String");
+impl_code_type_for_primitive!(Int8CodeType, "Int8");
+impl_code_type_for_primitive!(Int16CodeType, "Int16");
+impl_code_type_for_primitive!(Int32CodeType, "Int32");
+impl_code_type_for_primitive!(Int64CodeType, "Int64");
+impl_code_type_for_primitive!(UInt8CodeType, "UInt8");
+impl_code_type_for_primitive!(UInt16CodeType, "UInt16");
+impl_code_type_for_primitive!(UInt32CodeType, "UInt32");
+impl_code_type_for_primitive!(UInt64CodeType, "UInt64");
+impl_code_type_for_primitive!(Float32CodeType, "Float");
+impl_code_type_for_primitive!(Float64CodeType, "Double");
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/record.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/record.rs
new file mode 100644
index 0000000000..0943bcaada
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/gen_swift/record.rs
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::backend::{CodeOracle, CodeType};
+
+pub struct RecordCodeType {
+    id: String,
+}
+
+impl RecordCodeType {
+    pub fn new(id: String) -> Self {
+        Self { id }
+    }
+}
+
+impl CodeType for RecordCodeType {
+    fn type_label(&self, oracle: &dyn CodeOracle) -> String {
+        oracle.class_name(&self.id)
+    }
+
+    fn canonical_name(&self, _oracle: &dyn CodeOracle) -> String {
+        format!("Type{}", self.id)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/mod.rs b/third_party/rust/uniffi_bindgen/src/bindings/swift/mod.rs
new file mode 100644
index 0000000000..740759acbf
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/mod.rs
@@ -0,0 +1,198 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Swift bindings backend for UniFFI
+//!
+//! This module generates Swift bindings from a [`ComponentInterface`] definition,
+//! using Swift's builtin support for loading C header files.
+//!
+//! Conceptually, the generated bindings are split into two Swift modules, one for the low-level
+//! C FFI layer and one for the higher-level Swift bindings. For a UniFFI component named "example"
+//! we generate:
+//!
+//!   * A C header file `exampleFFI.h` declaring the low-level structs and functions for calling
+//!    into Rust, along with a corresponding `exampleFFI.modulemap` to expose them to Swift.
+//!
+//!   * A Swift source file `example.swift` that imports the `exampleFFI` module and wraps it
+//!    to provide the higher-level Swift API.
+//!
+//! Most of the concepts in a [`ComponentInterface`] have an obvious counterpart in Swift,
+//! with the details documented in inline comments where appropriate.
+//!
+//! To handle lifting/lowering/serializing types across the FFI boundary, the Swift code
+//! defines a `protocol ViaFfi` that is analogous to the `uniffi::ViaFfi` Rust trait.
+//! Each type that can traverse the FFI conforms to the `ViaFfi` protocol, which specifies:
+//!
+//!  * The corresponding low-level type.
+//!  * How to lift from and lower into into that type.
+//!  * How to read from and write into a byte buffer.
+//!
+
+use std::{ffi::OsString, io::Write, process::Command};
+
+use anyhow::{bail, Context, Result};
+use camino::Utf8Path;
+use fs_err::File;
+
+pub mod gen_swift;
+pub use gen_swift::{generate_bindings, Config};
+
+use super::super::interface::ComponentInterface;
+
+/// The Swift bindings generated from a [`ComponentInterface`].
+///
+pub struct Bindings {
+    /// The contents of the generated `.swift` file, as a string.
+    library: String,
+    /// The contents of the generated `.h` file, as a string.
+    header: String,
+    /// The contents of the generated `.modulemap` file, as a string.
+    modulemap: Option<String>,
+}
+
+/// Write UniFFI component bindings for Swift as files on disk.
+///
+/// Unlike other target languages, binding to Rust code from Swift involves more than just
+/// generating a `.swift` file. We also need to produce a `.h` file with the C-level API
+/// declarations, and a `.modulemap` file to tell Swift how to use it.
+pub fn write_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+    try_format_code: bool,
+) -> Result<()> {
+    let Bindings {
+        header,
+        library,
+        modulemap,
+    } = generate_bindings(config, ci)?;
+
+    let source_file = out_dir.join(format!("{}.swift", config.module_name()));
+    let mut l = File::create(&source_file)?;
+    write!(l, "{}", library)?;
+
+    let mut h = File::create(out_dir.join(config.header_filename()))?;
+    write!(h, "{}", header)?;
+
+    if let Some(modulemap) = modulemap {
+        let mut m = File::create(out_dir.join(config.modulemap_filename()))?;
+        write!(m, "{}", modulemap)?;
+    }
+
+    if try_format_code {
+        if let Err(e) = Command::new("swiftformat")
+            .arg(source_file.as_str())
+            .output()
+        {
+            println!(
+                "Warning: Unable to auto-format {} using swiftformat: {:?}",
+                source_file.file_name().unwrap(),
+                e
+            )
+        }
+    }
+
+    Ok(())
+}
+
+/// Compile UniFFI component bindings for Swift for use from the `swift` command-line.
+///
+/// This is a utility function to help with running Swift tests. While the `swift` command-line
+/// tool is able to execute Swift code from source, that code can only load other Swift modules
+/// if they have been pre-compiled into a `.dylib` and corresponding `.swiftmodule`. Since our
+/// test scripts need to be able to import the generated bindings, we have to compile them
+/// ahead of time before running the tests.
+///
+pub fn compile_bindings(
+    config: &Config,
+    ci: &ComponentInterface,
+    out_dir: &Utf8Path,
+) -> Result<()> {
+    if !config.generate_module_map() {
+        bail!("Cannot compile Swift bindings when `generate_module_map` is `false`")
+    }
+
+    let module_map_file = out_dir.join(config.modulemap_filename());
+    let mut module_map_file_option = OsString::from("-fmodule-map-file=");
+    module_map_file_option.push(module_map_file.as_os_str());
+
+    let source_file = out_dir.join(format!("{}.swift", config.module_name()));
+    let dylib_file = out_dir.join(format!("lib{}.dylib", config.module_name()));
+
+    // `-emit-library -o <path>` generates a `.dylib`, so that we can use the
+    // Swift module from the REPL. Otherwise, we'll get "Couldn't lookup
+    // symbols" when we try to import the module.
+    // See https://bugs.swift.org/browse/SR-1191.
+
+    let status = Command::new("swiftc")
+        .arg("-module-name")
+        .arg(ci.namespace())
+        .arg("-emit-library")
+        .arg("-o")
+        .arg(dylib_file)
+        .arg("-emit-module")
+        .arg("-emit-module-path")
+        .arg(out_dir)
+        .arg("-parse-as-library")
+        .arg("-L")
+        .arg(out_dir)
+        .arg(format!("-l{}", config.cdylib_name()))
+        .arg("-Xcc")
+        .arg(module_map_file_option)
+        .arg(source_file)
+        .spawn()
+        .context("Failed to spawn `swiftc` when compiling bindings")?
+        .wait()
+        .context("Failed to wait for `swiftc` when compiling bindings")?;
+    if !status.success() {
+        bail!("running `swiftc` failed")
+    }
+    Ok(())
+}
+
+/// Run a Swift script, allowing it to load modules from the given output directory.
+///
+/// This executes the given Swift script file in a way that allows it to import any other
+/// Swift modules in the given output directory. The modules must have been pre-compiled
+/// using the [`compile_bindings`] function.
+///
+pub fn run_script(out_dir: &Utf8Path, script_file: &Utf8Path) -> Result<()> {
+    let mut cmd = Command::new("swift");
+
+    // Find any module maps and/or dylibs in the target directory, and tell swift to use them.
+    // Listing the directory like this is a little bit hacky - it would be nicer if we could tell
+    // Swift to load only the module(s) for the component under test, but the way we're calling
+    // this test function doesn't allow us to pass that name in to the call.
+
+    cmd.arg("-I").arg(out_dir);
+    for entry in out_dir
+        .read_dir()
+        .context("Failed to list target directory when running script")?
+    {
+        let entry = entry.context("Failed to list target directory when running script")?;
+        if let Some(ext) = entry.path().extension() {
+            if ext == "modulemap" {
+                let mut option = OsString::from("-fmodule-map-file=");
+                option.push(entry.path());
+                cmd.arg("-Xcc");
+                cmd.arg(option);
+            } else if ext == "dylib" || ext == "so" {
+                let mut option = OsString::from("-l");
+                option.push(entry.path());
+                cmd.arg(option);
+            }
+        }
+    }
+    cmd.arg(script_file);
+
+    let status = cmd
+        .spawn()
+        .context("Failed to spawn `swift` when running script")?
+        .wait()
+        .context("Failed to wait for `swift` when running script")?;
+    if !status.success() {
+        bail!("running `swift` failed")
+    }
+    Ok(())
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/BooleanHelper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/BooleanHelper.swift
new file mode 100644
index 0000000000..231ca258ff
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/BooleanHelper.swift
@@ -0,0 +1,20 @@
+fileprivate struct FfiConverterBool : FfiConverter {
+    typealias FfiType = Int8
+    typealias SwiftType = Bool
+
+    static func lift(_ value: Int8) throws -> Bool {
+        return value != 0
+    }
+
+    static func lower(_ value: Bool) -> Int8 {
+        return value ? 1 : 0
+    }
+
+    static func read(from buf: Reader) throws -> Bool {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: Bool, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/BridgingHeaderTemplate.h b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/BridgingHeaderTemplate.h
new file mode 100644
index 0000000000..50b95d96e8
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/BridgingHeaderTemplate.h
@@ -0,0 +1,55 @@
+// This file was autogenerated by some hot garbage in the `uniffi` crate.
+// Trust me, you don't want to mess with it!
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+// The following structs are used to implement the lowest level
+// of the FFI, and thus useful to multiple uniffied crates.
+// We ensure they are declared exactly once, with a header guard, UNIFFI_SHARED_H.
+#ifdef UNIFFI_SHARED_H
+    // We also try to prevent mixing versions of shared uniffi header structs.
+    // If you add anything to the #else block, you must increment the version suffix in UNIFFI_SHARED_HEADER_V4
+    #ifndef UNIFFI_SHARED_HEADER_V4
+        #error Combining helper code from multiple versions of uniffi is not supported
+    #endif // ndef UNIFFI_SHARED_HEADER_V4
+#else
+#define UNIFFI_SHARED_H
+#define UNIFFI_SHARED_HEADER_V4
+// ⚠️ Attention: If you change this #else block (ending in `#endif // def UNIFFI_SHARED_H`) you *must* ⚠️
+// ⚠️ increment the version suffix in all instances of UNIFFI_SHARED_HEADER_V4 in this file.           ⚠️
+
+typedef struct RustBuffer
+{
+    int32_t capacity;
+    int32_t len;
+    uint8_t *_Nullable data;
+} RustBuffer;
+
+typedef int32_t (*ForeignCallback)(uint64_t, int32_t, RustBuffer, RustBuffer *_Nonnull);
+
+typedef struct ForeignBytes
+{
+    int32_t len;
+    const uint8_t *_Nullable data;
+} ForeignBytes;
+
+// Error definitions
+typedef struct RustCallStatus {
+    int8_t code;
+    RustBuffer errorBuf;
+} RustCallStatus;
+
+// ⚠️ Attention: If you change this #else block (ending in `#endif // def UNIFFI_SHARED_H`) you *must* ⚠️
+// ⚠️ increment the version suffix in all instances of UNIFFI_SHARED_HEADER_V4 in this file.           ⚠️
+#endif // def UNIFFI_SHARED_H
+
+{% for func in ci.iter_ffi_function_definitions() -%}
+    {%- match func.return_type() -%}{%- when Some with (type_) %}{{ type_|ffi_type_name }}{% when None %}void{% endmatch %} {{ func.name() }}(
+      {% call swift::arg_list_ffi_decl(func) %}
+    );
+{% endfor -%}
+
+{% import "macros.swift" as swift %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceRuntime.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceRuntime.swift
new file mode 100644
index 0000000000..9db2ee4f4f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceRuntime.swift
@@ -0,0 +1,60 @@
+fileprivate extension NSLock {
+    func withLock<T>(f: () throws -> T) rethrows -> T {
+        self.lock()
+        defer { self.unlock() }
+        return try f()
+    }
+}
+
+fileprivate typealias Handle = UInt64
+fileprivate class ConcurrentHandleMap<T> {
+    private var leftMap: [Handle: T] = [:]
+    private var counter: [Handle: UInt64] = [:]
+    private var rightMap: [ObjectIdentifier: Handle] = [:]
+
+    private let lock = NSLock()
+    private var currentHandle: Handle = 0
+    private let stride: Handle = 1
+
+    func insert(obj: T) -> Handle {
+        lock.withLock {
+            let id = ObjectIdentifier(obj as AnyObject)
+            let handle = rightMap[id] ?? {
+                currentHandle += stride
+                let handle = currentHandle
+                leftMap[handle] = obj
+                rightMap[id] = handle
+                return handle
+            }()
+            counter[handle] = (counter[handle] ?? 0) + 1
+            return handle
+        }
+    }
+
+    func get(handle: Handle) -> T? {
+        lock.withLock {
+            leftMap[handle]
+        }
+    }
+
+    func delete(handle: Handle) {
+        remove(handle: handle)
+    }
+
+    @discardableResult
+    func remove(handle: Handle) -> T? {
+        lock.withLock {
+            defer { counter[handle] = (counter[handle] ?? 1) - 1 }
+            guard counter[handle] == 1 else { return leftMap[handle] }
+            let obj = leftMap.removeValue(forKey: handle)
+            if let obj = obj {
+                rightMap.removeValue(forKey: ObjectIdentifier(obj as AnyObject))
+            }
+            return obj
+        }
+    }
+}
+
+// Magic number for the Rust proxy to call using the same mechanism as every other method,
+// to free the callback once it's dropped by Rust.
+private let IDX_CALLBACK_FREE: Int32 = 0
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceTemplate.swift
new file mode 100644
index 0000000000..4acbf0599d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceTemplate.swift
@@ -0,0 +1,154 @@
+{%- let cbi = ci.get_callback_interface_definition(name).unwrap() %}
+{%- let foreign_callback = format!("foreignCallback{}", canonical_type_name) %}
+{%- if self.include_once_check("CallbackInterfaceRuntime.swift") %}{%- include "CallbackInterfaceRuntime.swift" %}{%- endif %}
+
+// Declaration and FfiConverters for {{ type_name }} Callback Interface
+
+public protocol {{ type_name }} : AnyObject {
+    {% for meth in cbi.methods() -%}
+    func {{ meth.name()|fn_name }}({% call swift::arg_list_protocol(meth) %}) {% call swift::throws(meth) -%}
+    {%- match meth.return_type() -%}
+    {%- when Some with (return_type) %} -> {{ return_type|type_name -}}
+    {%- else -%}
+    {%- endmatch %}
+    {% endfor %}
+}
+
+// The ForeignCallback that is passed to Rust.
+fileprivate let {{ foreign_callback }} : ForeignCallback =
+    { (handle: Handle, method: Int32, args: RustBuffer, out_buf: UnsafeMutablePointer<RustBuffer>) -> Int32 in
+        {% for meth in cbi.methods() -%}
+    {%- let method_name = format!("invoke_{}", meth.name())|fn_name -%}
+
+    func {{ method_name }}(_ swiftCallbackInterface: {{ type_name }}, _ args: RustBuffer) throws -> RustBuffer {
+        defer { args.deallocate() }
+        {#- Unpacking args from the RustBuffer #}
+            {%- if meth.arguments().len() != 0 -%}
+            {#- Calling the concrete callback object #}
+
+            let reader = Reader(data: Data(rustBuffer: args))
+            {% if meth.return_type().is_some() %}let result = {% endif -%}
+            {% if meth.throws() %}try {% endif -%}
+            swiftCallbackInterface.{{ meth.name()|fn_name }}(
+                    {% for arg in meth.arguments() -%}
+                    {% if !config.omit_argument_labels() %}{{ arg.name()|var_name }}: {% endif %} try {{ arg|read_fn }}(from: reader)
+                    {%- if !loop.last %}, {% endif %}
+                    {% endfor -%}
+                )
+            {% else %}
+            {% if meth.return_type().is_some() %}let result = {% endif -%}
+            {% if meth.throws() %}try {% endif -%}
+            swiftCallbackInterface.{{ meth.name()|fn_name }}()
+            {% endif -%}
+
+        {#- Packing up the return value into a RustBuffer #}
+                {%- match meth.return_type() -%}
+                {%- when Some with (return_type) -%}
+                let writer = Writer()
+                {{ return_type|write_fn }}(result, into: writer)
+                return RustBuffer(bytes: writer.bytes)
+                {%- else -%}
+                return RustBuffer()
+                {% endmatch -%}
+                // TODO catch errors and report them back to Rust.
+                // https://github.com/mozilla/uniffi-rs/issues/351
+
+        }
+        {% endfor %}
+
+        let cb: {{ cbi|type_name }}
+        do {
+            cb = try {{ ffi_converter_name }}.lift(handle)
+        } catch {
+            out_buf.pointee = {{ Type::String.borrow()|lower_fn }}("{{ cbi.name() }}: Invalid handle")
+            return -1
+        }
+
+        switch method {
+            case IDX_CALLBACK_FREE:
+                {{ ffi_converter_name }}.drop(handle: handle)
+                // No return value.
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+                return 0
+            {% for meth in cbi.methods() -%}
+            {% let method_name = format!("invoke_{}", meth.name())|fn_name -%}
+            case {{ loop.index }}:
+                do {
+                    out_buf.pointee = try {{ method_name }}(cb, args)
+                    // Value written to out buffer.
+                    // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+                    return 1
+                {%- match meth.throws_type() %}
+                {%- when Some(error_type) %}
+                } catch let error as {{ error_type|type_name }} {
+                    out_buf.pointee = {{ error_type|lower_fn }}(error)
+                    return -2
+                {%- else %}
+                {%- endmatch %}
+                } catch let error {
+                    out_buf.pointee = {{ Type::String.borrow()|lower_fn }}(String(describing: error))
+                    return -1
+                }
+            {% endfor %}
+            // This should never happen, because an out of bounds method index won't
+            // ever be used. Once we can catch errors, we should return an InternalError.
+            // https://github.com/mozilla/uniffi-rs/issues/351
+            default:
+                // An unexpected error happened.
+                // See docs of ForeignCallback in `uniffi/src/ffi/foreigncallbacks.rs`
+                return -1
+        }
+    }
+
+// FFIConverter protocol for callback interfaces
+fileprivate struct {{ ffi_converter_name }} {
+    // Initialize our callback method with the scaffolding code
+    private static var callbackInitialized = false
+    private static func initCallback() {
+        try! rustCall { (err: UnsafeMutablePointer<RustCallStatus>) in
+                {{ cbi.ffi_init_callback().name() }}({{ foreign_callback }}, err)
+        }
+    }
+    private static func ensureCallbackinitialized() {
+        if !callbackInitialized {
+            initCallback()
+            callbackInitialized = true
+        }
+    }
+
+    static func drop(handle: Handle) {
+        handleMap.remove(handle: handle)
+    }
+
+    private static var handleMap = ConcurrentHandleMap<{{ type_name }}>()
+}
+
+extension {{ ffi_converter_name }} : FfiConverter {
+    typealias SwiftType = {{ type_name }}
+    // We can use Handle as the FFIType because it's a typealias to UInt64
+    typealias FfiType = Handle
+
+    static func lift(_ handle: Handle) throws -> SwiftType {
+        ensureCallbackinitialized();
+        guard let callback = handleMap.get(handle: handle) else {
+            throw UniffiInternalError.unexpectedStaleHandle
+        }
+        return callback
+    }
+
+    static func read(from buf: Reader) throws -> SwiftType {
+        ensureCallbackinitialized();
+        let handle: Handle = try buf.readInt()
+        return try lift(handle)
+    }
+
+    static func lower(_ v: SwiftType) -> Handle {
+        ensureCallbackinitialized();
+        return handleMap.insert(obj: v)
+    }
+
+    static func write(_ v: SwiftType, into buf: Writer) {
+        ensureCallbackinitialized();
+        buf.writeInt(lower(v))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CustomType.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CustomType.swift
new file mode 100644
index 0000000000..741d8d631c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/CustomType.swift
@@ -0,0 +1,58 @@
+{%- let ffi_type_name=builtin.ffi_type().borrow()|ffi_type_name %}
+{%- match config.custom_types.get(name.as_str())  %}
+{%- when None %}
+{#- No config, just forward all methods to our builtin type #}
+/**
+ * Typealias from the type name used in the UDL file to the builtin type.  This
+ * is needed because the UDL type name is used in function/method signatures.
+ */
+public typealias {{ name }} = {{ builtin|type_name }}
+fileprivate typealias FfiConverterType{{ name }} = {{ builtin|ffi_converter_name }}
+
+{%- when Some with (config) %}
+
+{# When the config specifies a different type name, create a typealias for it #}
+{%- match config.type_name %}
+{%- when Some with (concrete_type_name) %}
+/**
+ * Typealias from the type name used in the UDL file to the custom type.  This
+ * is needed because the UDL type name is used in function/method signatures.
+ */
+public typealias {{ name }} = {{ concrete_type_name }}
+{%- else %}
+{%- endmatch %}
+
+{%- match config.imports %}
+{%- when Some(imports) %}
+{%- for import_name in imports %}
+{{ self.add_import(import_name) }}
+{%- endfor %}
+{%- else %}
+{%- endmatch %}
+
+fileprivate struct FfiConverterType{{ name }} {
+    {#- Custom type config supplied, use it to convert the builtin type #}
+
+    static func read(from buf: Reader) throws -> {{ name }} {
+        let builtinValue = try {{ builtin|read_fn }}(from: buf)
+        return {{ config.into_custom.render("builtinValue") }}
+    }
+
+    static func write(_ value: {{ name }}, into buf: Writer) {
+        let builtinValue = {{ config.from_custom.render("value") }}
+        return {{ builtin|write_fn }}(builtinValue, into: buf)
+    }
+
+    static func lift(_ value: {{ ffi_type_name }}) throws -> {{ name }} {
+        let builtinValue = try {{ builtin|lift_fn }}(value)
+        return {{ config.into_custom.render("builtinValue") }}
+    }
+
+    static func lower(_ value: {{ name }}) -> {{ ffi_type_name }} {
+        let builtinValue = {{ config.from_custom.render("value") }}
+        return {{ builtin|lower_fn }}(builtinValue)
+    }
+
+}
+{%- endmatch %}
+
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/DurationHelper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/DurationHelper.swift
new file mode 100644
index 0000000000..f4371a079c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/DurationHelper.swift
@@ -0,0 +1,24 @@
+fileprivate struct FfiConverterDuration: FfiConverterRustBuffer {
+    typealias SwiftType = TimeInterval
+
+    static func read(from buf: Reader) throws -> TimeInterval {
+        let seconds: UInt64 = try buf.readInt()
+        let nanoseconds: UInt32 = try buf.readInt()
+        return Double(seconds) + (Double(nanoseconds) / 1.0e9)
+    }
+
+    static func write(_ value: TimeInterval, into buf: Writer) {
+        if value.rounded(.down) > Double(Int64.max) {
+            fatalError("Duration overflow, exceeds max bounds supported by Uniffi")
+        }
+
+        if value < 0 {
+            fatalError("Invalid duration, must be non-negative")
+        }
+
+        let seconds = UInt64(value)
+        let nanoseconds = UInt32((value - Double(seconds)) * 1.0e9)
+        buf.writeInt(seconds)
+        buf.writeInt(nanoseconds)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/EnumTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/EnumTemplate.swift
new file mode 100644
index 0000000000..2feca61b1f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/EnumTemplate.swift
@@ -0,0 +1,48 @@
+// Note that we don't yet support `indirect` for enums.
+// See https://github.com/mozilla/uniffi-rs/issues/396 for further discussion.
+{%- let e = ci.get_enum_definition(name).unwrap() %}
+public enum {{ type_name }} {
+    {% for variant in e.variants() %}
+    case {{ variant.name()|enum_variant_swift }}{% if variant.fields().len() > 0 %}({% call swift::field_list_decl(variant) %}){% endif -%}
+    {% endfor %}
+}
+
+fileprivate struct {{ ffi_converter_name }}: FfiConverterRustBuffer {
+    typealias SwiftType = {{ type_name }}
+
+    static func read(from buf: Reader) throws -> {{ type_name }} {
+        let variant: Int32 = try buf.readInt()
+        switch variant {
+        {% for variant in e.variants() %}
+        case {{ loop.index }}: return .{{ variant.name()|enum_variant_swift }}{% if variant.has_fields() %}(
+            {%- for field in variant.fields() %}
+            {{ field.name()|var_name }}: try {{ field|read_fn }}(from: buf)
+            {%- if !loop.last %}, {% endif %}
+            {%- endfor %}
+        ){%- endif %}
+        {% endfor %}
+        default: throw UniffiInternalError.unexpectedEnumCase
+        }
+    }
+
+    static func write(_ value: {{ type_name }}, into buf: Writer) {
+        switch value {
+        {% for variant in e.variants() %}
+        {% if variant.has_fields() %}
+        case let .{{ variant.name()|enum_variant_swift }}({% for field in variant.fields() %}{{ field.name()|var_name }}{%- if loop.last -%}{%- else -%},{%- endif -%}{% endfor %}):
+            buf.writeInt(Int32({{ loop.index }}))
+            {% for field in variant.fields() -%}
+            {{ field|write_fn }}({{ field.name()|var_name }}, into: buf)
+            {% endfor -%}
+        {% else %}
+        case .{{ variant.name()|enum_variant_swift }}:
+            buf.writeInt(Int32({{ loop.index }}))
+        {% endif %}
+        {%- endfor %}
+        }
+    }
+}
+
+{% if !contains_object_references %}
+extension {{ type_name }}: Equatable, Hashable {}
+{% endif %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ErrorTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ErrorTemplate.swift
new file mode 100644
index 0000000000..2a1c298686
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ErrorTemplate.swift
@@ -0,0 +1,83 @@
+{%- let e = ci.get_error_definition(name).unwrap() %}
+public enum {{ type_name }} {
+
+    {% if e.is_flat() %}
+    {% for variant in e.variants() %}
+    // Simple error enums only carry a message
+    case {{ variant.name()|class_name }}(message: String)
+    {% endfor %}
+
+    {%- else %}
+    {% for variant in e.variants() %}
+    case {{ variant.name()|class_name }}{% if variant.fields().len() > 0 %}({% call swift::field_list_decl(variant) %}){% endif -%}
+    {% endfor %}
+
+    {%- endif %}
+}
+
+fileprivate struct {{ ffi_converter_name }}: FfiConverterRustBuffer {
+    typealias SwiftType = {{ type_name }}
+
+    static func read(from buf: Reader) throws -> {{ type_name }} {
+        let variant: Int32 = try buf.readInt()
+        switch variant {
+
+        {% if e.is_flat() %}
+
+        {% for variant in e.variants() %}
+        case {{ loop.index }}: return .{{ variant.name()|class_name }}(
+            message: try {{ Type::String.borrow()|read_fn }}(from: buf)
+        )
+        {% endfor %}
+
+        {% else %}
+
+        {% for variant in e.variants() %}
+        case {{ loop.index }}: return .{{ variant.name()|class_name }}{% if variant.has_fields() -%}(
+            {% for field in variant.fields() -%}
+            {{ field.name()|var_name }}: try {{ field|read_fn }}(from: buf)
+            {%- if !loop.last %}, {% endif %}
+            {% endfor -%}
+        ){% endif -%}
+        {% endfor %}
+
+         {% endif -%}
+        default: throw UniffiInternalError.unexpectedEnumCase
+        }
+    }
+
+    static func write(_ value: {{ type_name }}, into buf: Writer) {
+        switch value {
+
+        {% if e.is_flat() %}
+
+        {% for variant in e.variants() %}
+        case let .{{ variant.name()|class_name }}(message):
+            buf.writeInt(Int32({{ loop.index }}))
+            {{ Type::String.borrow()|write_fn }}(message, into: buf)
+        {%- endfor %}
+
+        {% else %}
+
+        {% for variant in e.variants() %}
+        {% if variant.has_fields() %}
+        case let .{{ variant.name()|class_name }}({% for field in variant.fields() %}{{ field.name()|var_name }}{%- if loop.last -%}{%- else -%},{%- endif -%}{% endfor %}):
+            buf.writeInt(Int32({{ loop.index }}))
+            {% for field in variant.fields() -%}
+            {{ field|write_fn }}({{ field.name()|var_name }}, into: buf)
+            {% endfor -%}
+        {% else %}
+        case .{{ variant.name()|class_name }}:
+            buf.writeInt(Int32({{ loop.index }}))
+        {% endif %}
+        {%- endfor %}
+
+        {%- endif %}
+        }
+    }
+}
+
+{% if !contains_object_references %}
+extension {{ type_name }}: Equatable, Hashable {}
+{% endif %}
+extension {{ type_name }}: Error { }
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Float32Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Float32Helper.swift
new file mode 100644
index 0000000000..5800ca6754
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Float32Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterFloat: FfiConverterPrimitive {
+    typealias FfiType = Float
+    typealias SwiftType = Float
+
+    static func read(from buf: Reader) throws -> Float {
+        return try lift(buf.readFloat())
+    }
+
+    static func write(_ value: Float, into buf: Writer) {
+        buf.writeFloat(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Float64Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Float64Helper.swift
new file mode 100644
index 0000000000..b96dcd24a0
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Float64Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterDouble: FfiConverterPrimitive {
+    typealias FfiType = Double
+    typealias SwiftType = Double
+
+    static func read(from buf: Reader) throws -> Double {
+        return try lift(buf.readDouble())
+    }
+
+    static func write(_ value: Double, into buf: Writer) {
+        buf.writeDouble(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Helpers.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Helpers.swift
new file mode 100644
index 0000000000..18e2397733
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Helpers.swift
@@ -0,0 +1,84 @@
+// An error type for FFI errors. These errors occur at the UniFFI level, not
+// the library level.
+fileprivate enum UniffiInternalError: LocalizedError {
+    case bufferOverflow
+    case incompleteData
+    case unexpectedOptionalTag
+    case unexpectedEnumCase
+    case unexpectedNullPointer
+    case unexpectedRustCallStatusCode
+    case unexpectedRustCallError
+    case unexpectedStaleHandle
+    case rustPanic(_ message: String)
+
+    public var errorDescription: String? {
+        switch self {
+        case .bufferOverflow: return "Reading the requested value would read past the end of the buffer"
+        case .incompleteData: return "The buffer still has data after lifting its containing value"
+        case .unexpectedOptionalTag: return "Unexpected optional tag; should be 0 or 1"
+        case .unexpectedEnumCase: return "Raw enum value doesn't match any cases"
+        case .unexpectedNullPointer: return "Raw pointer value was null"
+        case .unexpectedRustCallStatusCode: return "Unexpected RustCallStatus code"
+        case .unexpectedRustCallError: return "CALL_ERROR but no errorClass specified"
+        case .unexpectedStaleHandle: return "The object in the handle map has been dropped already"
+        case let .rustPanic(message): return message
+        }
+    }
+}
+
+fileprivate let CALL_SUCCESS: Int8 = 0
+fileprivate let CALL_ERROR: Int8 = 1
+fileprivate let CALL_PANIC: Int8 = 2
+
+fileprivate extension RustCallStatus {
+    init() {
+        self.init(
+            code: CALL_SUCCESS,
+            errorBuf: RustBuffer.init(
+                capacity: 0,
+                len: 0,
+                data: nil
+            )
+        )
+    }
+}
+
+private func rustCall<T>(_ callback: (UnsafeMutablePointer<RustCallStatus>) -> T) throws -> T {
+    try makeRustCall(callback, errorHandler: {
+        $0.deallocate()
+        return UniffiInternalError.unexpectedRustCallError
+    })
+}
+
+private func rustCallWithError<T, F: FfiConverter>
+    (_ errorFfiConverter: F.Type, _ callback: (UnsafeMutablePointer<RustCallStatus>) -> T) throws -> T
+    where F.SwiftType: Error, F.FfiType == RustBuffer
+    {
+    try makeRustCall(callback, errorHandler: { return try errorFfiConverter.lift($0) })
+}
+
+private func makeRustCall<T>(_ callback: (UnsafeMutablePointer<RustCallStatus>) -> T, errorHandler: (RustBuffer) throws -> Error) throws -> T {
+    var callStatus = RustCallStatus.init()
+    let returnedVal = callback(&callStatus)
+    switch callStatus.code {
+        case CALL_SUCCESS:
+            return returnedVal
+
+        case CALL_ERROR:
+            throw try errorHandler(callStatus.errorBuf)
+
+        case CALL_PANIC:
+            // When the rust code sees a panic, it tries to construct a RustBuffer
+            // with the message.  But if that code panics, then it just sends back
+            // an empty buffer.
+            if callStatus.errorBuf.len > 0 {
+                throw UniffiInternalError.rustPanic(try {{ Type::String.borrow()|lift_fn }}(callStatus.errorBuf))
+            } else {
+                callStatus.errorBuf.deallocate()
+                throw UniffiInternalError.rustPanic("Rust panic")
+            }
+
+        default:
+            throw UniffiInternalError.unexpectedRustCallStatusCode
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int16Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int16Helper.swift
new file mode 100644
index 0000000000..e924b3fa45
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int16Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterInt16: FfiConverterPrimitive {
+    typealias FfiType = Int16
+    typealias SwiftType = Int16
+
+    static func read(from buf: Reader) throws -> Int16 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: Int16, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int32Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int32Helper.swift
new file mode 100644
index 0000000000..e6f20773ba
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int32Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterInt32: FfiConverterPrimitive {
+    typealias FfiType = Int32
+    typealias SwiftType = Int32
+
+    static func read(from buf: Reader) throws -> Int32 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: Int32, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int64Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int64Helper.swift
new file mode 100644
index 0000000000..ef60f5224a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int64Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterInt64: FfiConverterPrimitive {
+    typealias FfiType = Int64
+    typealias SwiftType = Int64
+
+    static func read(from buf: Reader) throws -> Int64 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: Int64, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int8Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int8Helper.swift
new file mode 100644
index 0000000000..5990068c48
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Int8Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterInt8: FfiConverterPrimitive {
+    typealias FfiType = Int8
+    typealias SwiftType = Int8
+
+    static func read(from buf: Reader) throws -> Int8 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: Int8, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/MapTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/MapTemplate.swift
new file mode 100644
index 0000000000..20a99a11a9
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/MapTemplate.swift
@@ -0,0 +1,22 @@
+fileprivate struct {{ ffi_converter_name }}: FfiConverterRustBuffer {
+    fileprivate static func write(_ value: {{ type_name }}, into buf: Writer) {
+        let len = Int32(value.count)
+        buf.writeInt(len)
+        for (key, value) in value {
+            {{ key_type|write_fn }}(key, into: buf)
+            {{ value_type|write_fn }}(value, into: buf)
+        }
+    }
+
+    fileprivate static func read(from buf: Reader) throws -> {{ type_name }} {
+        let len: Int32 = try buf.readInt()
+        var dict = {{ type_name }}()
+        dict.reserveCapacity(Int(len))
+        for _ in 0..<len {
+            let key = try {{ key_type|read_fn }}(from: buf)
+            let value = try {{ value_type|read_fn }}(from: buf)
+            dict[key] = value
+        }
+        return dict
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ModuleMapTemplate.modulemap b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ModuleMapTemplate.modulemap
new file mode 100644
index 0000000000..f5f73ceb1b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ModuleMapTemplate.modulemap
@@ -0,0 +1,6 @@
+// This file was autogenerated by some hot garbage in the `uniffi` crate.
+// Trust me, you don't want to mess with it!
+module {{ config.ffi_module_name() }} {
+    header "{{ config.header_filename() }}"
+    export *
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ObjectTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ObjectTemplate.swift
new file mode 100644
index 0000000000..de2b5b8660
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/ObjectTemplate.swift
@@ -0,0 +1,88 @@
+{%- let obj = ci.get_object_definition(name).unwrap() %}
+public protocol {{ obj.name() }}Protocol {
+    {% for meth in obj.methods() -%}
+    func {{ meth.name()|fn_name }}({% call swift::arg_list_protocol(meth) %}) {% call swift::throws(meth) -%}
+    {%- match meth.return_type() -%}
+    {%- when Some with (return_type) %} -> {{ return_type|type_name -}}
+    {%- else -%}
+    {%- endmatch %}
+    {% endfor %}
+}
+
+public class {{ type_name }}: {{ obj.name() }}Protocol {
+    fileprivate let pointer: UnsafeMutableRawPointer
+
+    // TODO: We'd like this to be `private` but for Swifty reasons,
+    // we can't implement `FfiConverter` without making this `required` and we can't
+    // make it `required` without making it `public`.
+    required init(unsafeFromRawPointer pointer: UnsafeMutableRawPointer) {
+        self.pointer = pointer
+    }
+
+    {%- match obj.primary_constructor() %}
+    {%- when Some with (cons) %}
+    public convenience init({% call swift::arg_list_decl(cons) -%}) {% call swift::throws(cons) %} {
+        self.init(unsafeFromRawPointer: {% call swift::to_ffi_call(cons) %})
+    }
+    {%- when None %}
+    {%- endmatch %}
+
+    deinit {
+        try! rustCall { {{ obj.ffi_object_free().name() }}(pointer, $0) }
+    }
+
+    {% for cons in obj.alternate_constructors() %}
+    public static func {{ cons.name()|fn_name }}({% call swift::arg_list_decl(cons) %}) {% call swift::throws(cons) %} -> {{ type_name }} {
+        return {{ type_name }}(unsafeFromRawPointer: {% call swift::to_ffi_call(cons) %})
+    }
+    {% endfor %}
+
+    {# // TODO: Maybe merge the two templates (i.e the one with a return type and the one without) #}
+    {% for meth in obj.methods() -%}
+    {%- match meth.return_type() -%}
+
+    {%- when Some with (return_type) -%}
+    public func {{ meth.name()|fn_name }}({% call swift::arg_list_decl(meth) %}) {% call swift::throws(meth) %} -> {{ return_type|type_name }} {
+        return {% call swift::try(meth) %} {{ return_type|lift_fn }}(
+            {% call swift::to_ffi_call_with_prefix("self.pointer", meth) %}
+        )
+    }
+
+    {%- when None -%}
+    public func {{ meth.name()|fn_name }}({% call swift::arg_list_decl(meth) %}) {% call swift::throws(meth) %} {
+        {% call swift::to_ffi_call_with_prefix("self.pointer", meth) %}
+    }
+    {%- endmatch %}
+    {% endfor %}
+}
+
+
+fileprivate struct {{ ffi_converter_name }}: FfiConverter {
+    typealias FfiType = UnsafeMutableRawPointer
+    typealias SwiftType = {{ type_name }}
+
+    static func read(from buf: Reader) throws -> {{ type_name }} {
+        let v: UInt64 = try buf.readInt()
+        // The Rust code won't compile if a pointer won't fit in a UInt64.
+        // We have to go via `UInt` because that's the thing that's the size of a pointer.
+        let ptr = UnsafeMutableRawPointer(bitPattern: UInt(truncatingIfNeeded: v))
+        if (ptr == nil) {
+            throw UniffiInternalError.unexpectedNullPointer
+        }
+        return try lift(ptr!)
+    }
+
+    static func write(_ value: {{ type_name }}, into buf: Writer) {
+        // This fiddling is because `Int` is the thing that's the same size as a pointer.
+        // The Rust code won't compile if a pointer won't fit in a `UInt64`.
+        buf.writeInt(UInt64(bitPattern: Int64(Int(bitPattern: lower(value)))))
+    }
+
+    static func lift(_ pointer: UnsafeMutableRawPointer) throws -> {{ type_name }} {
+        return {{ type_name}}(unsafeFromRawPointer: pointer)
+    }
+
+    static func lower(_ value: {{ type_name }}) -> UnsafeMutableRawPointer {
+        return value.pointer
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/OptionalTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/OptionalTemplate.swift
new file mode 100644
index 0000000000..b4cd751d9d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/OptionalTemplate.swift
@@ -0,0 +1,20 @@
+fileprivate struct {{ ffi_converter_name }}: FfiConverterRustBuffer {
+    typealias SwiftType = {{ type_name }}
+
+    static func write(_ value: SwiftType, into buf: Writer) {
+        guard let value = value else {
+            buf.writeInt(Int8(0))
+            return
+        }
+        buf.writeInt(Int8(1))
+        {{ inner_type|write_fn }}(value, into: buf)
+    }
+
+    static func read(from buf: Reader) throws -> SwiftType {
+        switch try buf.readInt() as Int8 {
+        case 0: return nil
+        case 1: return try {{ inner_type|read_fn }}(from: buf)
+        default: throw UniffiInternalError.unexpectedOptionalTag
+        }
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/RecordTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/RecordTemplate.swift
new file mode 100644
index 0000000000..d7ed69d272
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/RecordTemplate.swift
@@ -0,0 +1,50 @@
+{%- let rec = ci.get_record_definition(name).unwrap() %}
+public struct {{ type_name }} {
+    {%- for field in rec.fields() %}
+    public var {{ field.name()|var_name }}: {{ field|type_name }}
+    {%- endfor %}
+
+    // Default memberwise initializers are never public by default, so we
+    // declare one manually.
+    public init({% call swift::field_list_decl(rec) %}) {
+        {%- for field in rec.fields() %}
+        self.{{ field.name()|var_name }} = {{ field.name()|var_name }}
+        {%- endfor %}
+    }
+}
+
+{% if !contains_object_references %}
+extension {{ type_name }}: Equatable, Hashable {
+    public static func ==(lhs: {{ type_name }}, rhs: {{ type_name }}) -> Bool {
+        {%- for field in rec.fields() %}
+        if lhs.{{ field.name()|var_name }} != rhs.{{ field.name()|var_name }} {
+            return false
+        }
+        {%- endfor %}
+        return true
+    }
+
+    public func hash(into hasher: inout Hasher) {
+        {%- for field in rec.fields() %}
+        hasher.combine({{ field.name()|var_name }})
+        {%- endfor %}
+    }
+}
+{% endif %}
+
+fileprivate struct {{ ffi_converter_name }}: FfiConverterRustBuffer {
+    fileprivate static func read(from buf: Reader) throws -> {{ type_name }} {
+        return try {{ type_name }}(
+            {%- for field in rec.fields() %}
+            {{ field.name()|var_name }}: {{ field|read_fn }}(from: buf)
+            {%- if !loop.last %}, {% endif %}
+            {%- endfor %}
+        )
+    }
+
+    fileprivate static func write(_ value: {{ type_name }}, into buf: Writer) {
+        {%- for field in rec.fields() %}
+        {{ field|write_fn }}(value.{{ field.name()|var_name }}, into: buf)
+        {%- endfor %}
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/RustBufferTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/RustBufferTemplate.swift
new file mode 100644
index 0000000000..79ed74c50a
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/RustBufferTemplate.swift
@@ -0,0 +1,184 @@
+fileprivate extension RustBuffer {
+    // Allocate a new buffer, copying the contents of a `UInt8` array.
+    init(bytes: [UInt8]) {
+        let rbuf = bytes.withUnsafeBufferPointer { ptr in
+            RustBuffer.from(ptr)
+        }
+        self.init(capacity: rbuf.capacity, len: rbuf.len, data: rbuf.data)
+    }
+
+    static func from(_ ptr: UnsafeBufferPointer<UInt8>) -> RustBuffer {
+        try! rustCall { {{ ci.ffi_rustbuffer_from_bytes().name() }}(ForeignBytes(bufferPointer: ptr), $0) }
+    }
+
+    // Frees the buffer in place.
+    // The buffer must not be used after this is called.
+    func deallocate() {
+        try! rustCall { {{ ci.ffi_rustbuffer_free().name() }}(self, $0) }
+    }
+}
+
+fileprivate extension ForeignBytes {
+    init(bufferPointer: UnsafeBufferPointer<UInt8>) {
+        self.init(len: Int32(bufferPointer.count), data: bufferPointer.baseAddress)
+    }
+}
+
+// For every type used in the interface, we provide helper methods for conveniently
+// lifting and lowering that type from C-compatible data, and for reading and writing
+// values of that type in a buffer.
+
+// Helper classes/extensions that don't change.
+// Someday, this will be in a libray of its own.
+
+fileprivate extension Data {
+    init(rustBuffer: RustBuffer) {
+        // TODO: This copies the buffer. Can we read directly from a
+        // Rust buffer?
+        self.init(bytes: rustBuffer.data!, count: Int(rustBuffer.len))
+    }
+}
+
+// A helper class to read values out of a byte buffer.
+fileprivate class Reader {
+    let data: Data
+    var offset: Data.Index
+
+    init(data: Data) {
+        self.data = data
+        self.offset = 0
+    }
+
+    // Reads an integer at the current offset, in big-endian order, and advances
+    // the offset on success. Throws if reading the integer would move the
+    // offset past the end of the buffer.
+    func readInt<T: FixedWidthInteger>() throws -> T {
+        let range = offset..<offset + MemoryLayout<T>.size
+        guard data.count >= range.upperBound else {
+            throw UniffiInternalError.bufferOverflow
+        }
+        if T.self == UInt8.self {
+            let value = data[offset]
+            offset += 1
+            return value as! T
+        }
+        var value: T = 0
+        let _ = withUnsafeMutableBytes(of: &value, { data.copyBytes(to: $0, from: range)})
+        offset = range.upperBound
+        return value.bigEndian
+    }
+
+    // Reads an arbitrary number of bytes, to be used to read
+    // raw bytes, this is useful when lifting strings
+    func readBytes(count: Int) throws -> Array<UInt8> {
+        let range = offset..<(offset+count)
+        guard data.count >= range.upperBound else {
+            throw UniffiInternalError.bufferOverflow
+        }
+        var value = [UInt8](repeating: 0, count: count)
+        value.withUnsafeMutableBufferPointer({ buffer in
+            data.copyBytes(to: buffer, from: range)
+        })
+        offset = range.upperBound
+        return value
+    }
+
+    // Reads a float at the current offset.
+    @inlinable
+    func readFloat() throws -> Float {
+        return Float(bitPattern: try readInt())
+    }
+
+    // Reads a float at the current offset.
+    @inlinable
+    func readDouble() throws -> Double {
+        return Double(bitPattern: try readInt())
+    }
+
+    // Indicates if the offset has reached the end of the buffer.
+    @inlinable
+    func hasRemaining() -> Bool {
+        return offset < data.count
+    }
+}
+
+// A helper class to write values into a byte buffer.
+fileprivate class Writer {
+    var bytes: [UInt8]
+    var offset: Array<UInt8>.Index
+
+    init() {
+        self.bytes = []
+        self.offset = 0
+    }
+
+    func writeBytes<S>(_ byteArr: S) where S: Sequence, S.Element == UInt8 {
+        bytes.append(contentsOf: byteArr)
+    }
+
+    // Writes an integer in big-endian order.
+    //
+    // Warning: make sure what you are trying to write
+    // is in the correct type!
+    func writeInt<T: FixedWidthInteger>(_ value: T) {
+        var value = value.bigEndian
+        withUnsafeBytes(of: &value) { bytes.append(contentsOf: $0) }
+    }
+
+    @inlinable
+    func writeFloat(_ value: Float) {
+        writeInt(value.bitPattern)
+    }
+
+    @inlinable
+    func writeDouble(_ value: Double) {
+        writeInt(value.bitPattern)
+    }
+}
+
+// Protocol for types that transfer other types across the FFI. This is
+// analogous go the Rust trait of the same name.
+fileprivate protocol FfiConverter {
+    associatedtype FfiType
+    associatedtype SwiftType
+
+    static func lift(_ value: FfiType) throws -> SwiftType
+    static func lower(_ value: SwiftType) -> FfiType
+    static func read(from buf: Reader) throws -> SwiftType
+    static func write(_ value: SwiftType, into buf: Writer)
+}
+
+// Types conforming to `Primitive` pass themselves directly over the FFI.
+fileprivate protocol FfiConverterPrimitive: FfiConverter where FfiType == SwiftType { }
+
+extension FfiConverterPrimitive {
+    static func lift(_ value: FfiType) throws -> SwiftType {
+        return value
+    }
+
+    static func lower(_ value: SwiftType) -> FfiType {
+        return value
+    }
+}
+
+// Types conforming to `FfiConverterRustBuffer` lift and lower into a `RustBuffer`.
+// Used for complex types where it's hard to write a custom lift/lower.
+fileprivate protocol FfiConverterRustBuffer: FfiConverter where FfiType == RustBuffer {}
+
+extension FfiConverterRustBuffer {
+    static func lift(_ buf: RustBuffer) throws -> SwiftType {
+        let reader = Reader(data: Data(rustBuffer: buf))
+        let value = try read(from: reader)
+        if reader.hasRemaining() {
+            throw UniffiInternalError.incompleteData
+        }
+        buf.deallocate()
+        return value
+    }
+
+    static func lower(_ value: SwiftType) -> RustBuffer {
+          let writer = Writer()
+          write(value, into: writer)
+          return RustBuffer(bytes: writer.bytes)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/SequenceTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/SequenceTemplate.swift
new file mode 100644
index 0000000000..4cd104f5dd
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/SequenceTemplate.swift
@@ -0,0 +1,21 @@
+fileprivate struct {{ ffi_converter_name }}: FfiConverterRustBuffer {
+    typealias SwiftType = {{ type_name }}
+
+    static func write(_ value: {{ type_name }}, into buf: Writer) {
+        let len = Int32(value.count)
+        buf.writeInt(len)
+        for item in value {
+            {{ inner_type|write_fn }}(item, into: buf)
+        }
+    }
+
+    static func read(from buf: Reader) throws -> {{ type_name }} {
+        let len: Int32 = try buf.readInt()
+        var seq = {{ type_name }}()
+        seq.reserveCapacity(Int(len))
+        for _ in 0 ..< len {
+            seq.append(try {{ inner_type|read_fn }}(from: buf))
+        }
+        return seq
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/StringHelper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/StringHelper.swift
new file mode 100644
index 0000000000..c6ca0ad981
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/StringHelper.swift
@@ -0,0 +1,37 @@
+fileprivate struct FfiConverterString: FfiConverter {
+    typealias SwiftType = String
+    typealias FfiType = RustBuffer
+
+    static func lift(_ value: RustBuffer) throws -> String {
+        defer {
+            value.deallocate()
+        }
+        if value.data == nil {
+            return String()
+        }
+        let bytes = UnsafeBufferPointer<UInt8>(start: value.data!, count: Int(value.len))
+        return String(bytes: bytes, encoding: String.Encoding.utf8)!
+    }
+
+    static func lower(_ value: String) -> RustBuffer {
+        return value.utf8CString.withUnsafeBufferPointer { ptr in
+            // The swift string gives us int8_t, we want uint8_t.
+            ptr.withMemoryRebound(to: UInt8.self) { ptr in
+                // The swift string gives us a trailing null byte, we don't want it.
+                let buf = UnsafeBufferPointer(rebasing: ptr.prefix(upTo: ptr.count - 1))
+                return RustBuffer.from(buf)
+            }
+        }
+    }
+
+    static func read(from buf: Reader) throws -> String {
+        let len: Int32 = try buf.readInt()
+        return String(bytes: try buf.readBytes(count: Int(len)), encoding: String.Encoding.utf8)!
+    }
+
+    static func write(_ value: String, into buf: Writer) {
+        let len = Int32(value.utf8.count)
+        buf.writeInt(len)
+        buf.writeBytes(value.utf8)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/TimestampHelper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/TimestampHelper.swift
new file mode 100644
index 0000000000..05aaade2d2
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/TimestampHelper.swift
@@ -0,0 +1,34 @@
+fileprivate struct FfiConverterTimestamp: FfiConverterRustBuffer {
+    typealias SwiftType = Date
+
+    static func read(from buf: Reader) throws -> Date {
+        let seconds: Int64 = try buf.readInt()
+        let nanoseconds: UInt32 = try buf.readInt()
+        if seconds >= 0 {
+            let delta = Double(seconds) + (Double(nanoseconds) / 1.0e9)
+            return Date.init(timeIntervalSince1970: delta)
+        } else {
+            let delta = Double(seconds) - (Double(nanoseconds) / 1.0e9)
+            return Date.init(timeIntervalSince1970: delta)
+        }
+    }
+
+    static func write(_ value: Date, into buf: Writer) {
+        var delta = value.timeIntervalSince1970
+        var sign: Int64 = 1
+        if delta < 0 {
+            // The nanoseconds portion of the epoch offset must always be
+            // positive, to simplify the calculation we will use the absolute
+            // value of the offset.
+            sign = -1
+            delta = -delta
+        }
+        if delta.rounded(.down) > Double(Int64.max) {
+            fatalError("Timestamp overflow, exceeds max bounds supported by Uniffi")
+        }
+        let seconds = Int64(delta)
+        let nanoseconds = UInt32((delta - Double(seconds)) * 1.0e9)
+        buf.writeInt(sign * seconds)
+        buf.writeInt(nanoseconds)
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/TopLevelFunctionTemplate.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/TopLevelFunctionTemplate.swift
new file mode 100644
index 0000000000..5ce762d2a0
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/TopLevelFunctionTemplate.swift
@@ -0,0 +1,15 @@
+{%- match func.return_type() -%}
+{%- when Some with (return_type) %}
+
+public func {{ func.name()|fn_name }}({%- call swift::arg_list_decl(func) -%}) {% call swift::throws(func) %} -> {{ return_type|type_name }} {
+    return {% call swift::try(func) %} {{ return_type|lift_fn }}(
+        {% call swift::to_ffi_call(func) %}
+    )
+}
+
+{% when None %}
+
+public func {{ func.name()|fn_name }}({% call swift::arg_list_decl(func) %}) {% call swift::throws(func) %} {
+    {% call swift::to_ffi_call(func) %}
+}
+{% endmatch %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Types.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Types.swift
new file mode 100644
index 0000000000..0940413b2c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Types.swift
@@ -0,0 +1,91 @@
+{%- import "macros.swift" as swift %}
+{%- for type_ in ci.iter_types() %}
+{%- let type_name = type_|type_name %}
+{%- let ffi_converter_name = type_|ffi_converter_name %}
+{%- let canonical_type_name = type_|canonical_name %}
+{%- let contains_object_references = ci.item_contains_object_references(type_) %}
+
+{#
+ # Map `Type` instances to an include statement for that type.
+ #
+ # There is a companion match in `KotlinCodeOracle::create_code_type()` which performs a similar function for the
+ # Rust code.
+ #
+ #   - When adding additional types here, make sure to also add a match arm to that function.
+ #   - To keep things managable, let's try to limit ourselves to these 2 mega-matches
+ #}
+{%- match type_ %}
+
+{%- when Type::Boolean %}
+{%- include "BooleanHelper.swift" %}
+
+{%- when Type::String %}
+{%- include "StringHelper.swift" %}
+
+{%- when Type::Int8 %}
+{%- include "Int8Helper.swift" %}
+
+{%- when Type::Int16 %}
+{%- include "Int16Helper.swift" %}
+
+{%- when Type::Int32 %}
+{%- include "Int32Helper.swift" %}
+
+{%- when Type::Int64 %}
+{%- include "Int64Helper.swift" %}
+
+{%- when Type::UInt8 %}
+{%- include "UInt8Helper.swift" %}
+
+{%- when Type::UInt16 %}
+{%- include "UInt16Helper.swift" %}
+
+{%- when Type::UInt32 %}
+{%- include "UInt32Helper.swift" %}
+
+{%- when Type::UInt64 %}
+{%- include "UInt64Helper.swift" %}
+
+{%- when Type::Float32 %}
+{%- include "Float32Helper.swift" %}
+
+{%- when Type::Float64 %}
+{%- include "Float64Helper.swift" %}
+
+{%- when Type::Timestamp %}
+{%- include "TimestampHelper.swift" %}
+
+{%- when Type::Duration %}
+{%- include "DurationHelper.swift" %}
+
+{%- when Type::CallbackInterface(name) %}
+{%- include "CallbackInterfaceTemplate.swift" %}
+
+{%- when Type::Custom { name, builtin } %}
+{%- include "CustomType.swift" %}
+
+{%- when Type::Enum(name) %}
+{%- include "EnumTemplate.swift" %}
+
+{%- when Type::Error(name) %}
+{%- include "ErrorTemplate.swift" %}
+
+{%- when Type::Object(name) %}
+{%- include "ObjectTemplate.swift" %}
+
+{%- when Type::Record(name) %}
+{%- include "RecordTemplate.swift" %}
+
+{%- when Type::Optional(inner_type) %}
+{%- include "OptionalTemplate.swift" %}
+
+{%- when Type::Sequence(inner_type) %}
+{%- include "SequenceTemplate.swift" %}
+
+{%- when Type::Map(key_type, value_type) %}
+{%- include "MapTemplate.swift" %}
+
+
+{%- else %}
+{%- endmatch %}
+{%- endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt16Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt16Helper.swift
new file mode 100644
index 0000000000..cab25cb354
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt16Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterUInt16: FfiConverterPrimitive {
+    typealias FfiType = UInt16
+    typealias SwiftType = UInt16
+
+    static func read(from buf: Reader) throws -> UInt16 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: SwiftType, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt32Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt32Helper.swift
new file mode 100644
index 0000000000..829f3e498e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt32Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterUInt32: FfiConverterPrimitive {
+    typealias FfiType = UInt32
+    typealias SwiftType = UInt32
+
+    static func read(from buf: Reader) throws -> UInt32 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: SwiftType, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt64Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt64Helper.swift
new file mode 100644
index 0000000000..64019d5191
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt64Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterUInt64: FfiConverterPrimitive {
+    typealias FfiType = UInt64
+    typealias SwiftType = UInt64
+
+    static func read(from buf: Reader) throws -> UInt64 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: SwiftType, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt8Helper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt8Helper.swift
new file mode 100644
index 0000000000..84aa33473d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/UInt8Helper.swift
@@ -0,0 +1,12 @@
+fileprivate struct FfiConverterUInt8: FfiConverterPrimitive {
+    typealias FfiType = UInt8
+    typealias SwiftType = UInt8
+
+    static func read(from buf: Reader) throws -> UInt8 {
+        return try lift(buf.readInt())
+    }
+
+    static func write(_ value: UInt8, into buf: Writer) {
+        buf.writeInt(lower(value))
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/macros.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/macros.swift
new file mode 100644
index 0000000000..8efc651ed3
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/macros.swift
@@ -0,0 +1,97 @@
+{#
+// Template to call into rust. Used in several places.
+// Variable names in `arg_list_decl` should match up with arg lists
+// passed to rust via `_arg_list_ffi_call`
+#}
+
+{%- macro to_ffi_call(func) -%}
+{% call try(func) %}
+    {% match func.throws_type() %}
+    {% when Some with (e) %}
+    rustCallWithError({{ e|ffi_converter_name }}.self) {
+    {% else %}
+    rustCall() {
+    {% endmatch %}
+    {{ func.ffi_func().name() }}({% call _arg_list_ffi_call(func) -%}{% if func.arguments().len() > 0 %}, {% endif %}$0)
+}
+{%- endmacro -%}
+
+{%- macro to_ffi_call_with_prefix(prefix, func) -%}
+{% call try(func) %}
+    {%- match func.throws_type() %}
+    {%- when Some with (e) %}
+    rustCallWithError({{ e|ffi_converter_name }}.self) {
+    {%- else %}
+    rustCall() {
+    {% endmatch %}
+    {{ func.ffi_func().name() }}(
+        {{- prefix }}, {% call _arg_list_ffi_call(func) -%}{% if func.arguments().len() > 0 %}, {% endif %}$0
+    )
+}
+{%- endmacro %}
+
+{%- macro _arg_list_ffi_call(func) %}
+    {%- for arg in func.arguments() %}
+        {{ arg|lower_fn }}({{ arg.name()|var_name }})
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro -%}
+
+{#-
+// Arglist as used in Swift declarations of methods, functions and constructors.
+// Note the var_name and type_name filters.
+-#}
+
+{% macro arg_list_decl(func) %}
+    {%- for arg in func.arguments() -%}
+        {% if config.omit_argument_labels() %}_ {% endif %}{{ arg.name()|var_name }}: {{ arg|type_name -}}
+        {%- match arg.default_value() %}
+        {%- when Some with(literal) %} = {{ literal|literal_swift(arg) }}
+        {%- else %}
+        {%- endmatch %}
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+
+{#-
+// Field lists as used in Swift declarations of Records and Enums.
+// Note the var_name and type_name filters.
+-#}
+{% macro field_list_decl(item) %}
+    {%- for field in item.fields() -%}
+        {{ field.name()|var_name }}: {{ field|type_name -}}
+        {%- match field.default_value() %}
+            {%- when Some with(literal) %} = {{ literal|literal_swift(field) }}
+            {%- else %}
+        {%- endmatch -%}
+        {% if !loop.last %}, {% endif %}
+    {%- endfor %}
+{%- endmacro %}
+
+
+{% macro arg_list_protocol(func) %}
+    {%- for arg in func.arguments() -%}
+        {% if config.omit_argument_labels() %}_ {% endif %}{{ arg.name()|var_name }}: {{ arg|type_name -}}
+        {%- if !loop.last %}, {% endif -%}
+    {%- endfor %}
+{%- endmacro %}
+
+
+{#-
+// Arglist as used in the _UniFFILib function declations.
+// Note unfiltered name but ffi_type_name filters.
+-#}
+{%- macro arg_list_ffi_decl(func) %}
+    {%- for arg in func.arguments() %}
+        {{- arg.type_().borrow()|ffi_type_name }} {{ arg.name() -}},
+    {%- endfor %}
+    RustCallStatus *_Nonnull out_status
+{%- endmacro -%}
+
+{%- macro throws(func) %}
+{%- if func.throws() %}throws{% endif %}
+{%- endmacro -%}
+
+{%- macro try(func) %}
+{%- if func.throws() %}try{% else %}try!{% endif %}
+{%- endmacro -%}
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/wrapper.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/wrapper.swift
new file mode 100644
index 0000000000..ac0557912e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/wrapper.swift
@@ -0,0 +1,40 @@
+// This file was autogenerated by some hot garbage in the `uniffi` crate.
+// Trust me, you don't want to mess with it!
+{%- import "macros.swift" as swift %}
+import Foundation
+{%- for imported_class in self.imports() %}
+import {{ imported_class }}
+{%- endfor %}
+
+// Depending on the consumer's build setup, the low-level FFI code
+// might be in a separate module, or it might be compiled inline into
+// this module. This is a bit of light hackery to work with both.
+#if canImport({{ config.ffi_module_name() }})
+import {{ config.ffi_module_name() }}
+#endif
+
+{% include "RustBufferTemplate.swift" %}
+{% include "Helpers.swift" %}
+
+// Public interface members begin here.
+{{ type_helper_code }}
+
+{%- for func in ci.function_definitions() %}
+{%- include "TopLevelFunctionTemplate.swift" %}
+{%- endfor %}
+
+/**
+ * Top level initializers and tear down methods.
+ *
+ * This is generated by uniffi.
+ */
+public enum {{ config.module_name().borrow()|class_name }}Lifecycle {
+    /**
+     * Initialize the FFI and Rust library. This should be only called once per application.
+     */
+    func initialize() {
+        {%- for initialization_fn in self.initialization_fns() %}
+        {{ initialization_fn }}()
+        {%- endfor %}
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/attributes.rs b/third_party/rust/uniffi_bindgen/src/interface/attributes.rs
new file mode 100644
index 0000000000..3c9bd522b1
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/attributes.rs
@@ -0,0 +1,747 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Attribute definitions for a `ComponentInterface`.
+//!
+//! This module provides some conveniences for working with attribute definitions
+//! from WebIDL. When encountering a weedle `ExtendedAttribute` node, use `TryFrom`
+//! to convert it into an [`Attribute`] representing one of the attributes that we
+//! support. You can also use the [`parse_attributes`] function to parse an
+//! `ExtendedAttributeList` into a vec of same.
+//!
+//! We only support a small number of attributes, so it's manageable to have them
+//! all handled by a single abstraction. This might need to be refactored in future
+//! if we grow significantly more complicated attribute handling.
+
+use anyhow::{bail, Result};
+use uniffi_meta::Checksum;
+
+/// Represents an attribute parsed from UDL, like `[ByRef]` or `[Throws]`.
+///
+/// This is a convenience enum for parsing UDL attributes and erroring out if we encounter
+/// any unsupported ones. These don't convert directly into parts of a `ComponentInterface`, but
+/// may influence the properties of things like functions and arguments.
+#[derive(Debug, Clone, Checksum)]
+pub(super) enum Attribute {
+    ByRef,
+    Enum,
+    Error,
+    Name(String),
+    SelfType(SelfType),
+    Threadsafe, // N.B. the `[Threadsafe]` attribute is deprecated and will be removed
+    Throws(String),
+    // `[External="crate_name"]` - We can `use crate_name::...` for the type.
+    External(String),
+    // Custom type on the scaffolding side
+    Custom,
+}
+
+impl Attribute {
+    pub fn is_error(&self) -> bool {
+        matches!(self, Attribute::Error)
+    }
+    pub fn is_enum(&self) -> bool {
+        matches!(self, Attribute::Enum)
+    }
+}
+
+/// Convert a weedle `ExtendedAttribute` into an `Attribute` for a `ComponentInterface` member,
+/// or error out if the attribute is not supported.
+impl TryFrom<&weedle::attribute::ExtendedAttribute<'_>> for Attribute {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attribute: &weedle::attribute::ExtendedAttribute<'_>,
+    ) -> Result<Self, anyhow::Error> {
+        match weedle_attribute {
+            // Matches plain named attributes like "[ByRef"].
+            weedle::attribute::ExtendedAttribute::NoArgs(attr) => match (attr.0).0 {
+                "ByRef" => Ok(Attribute::ByRef),
+                "Enum" => Ok(Attribute::Enum),
+                "Error" => Ok(Attribute::Error),
+                "Threadsafe" => Ok(Attribute::Threadsafe),
+                "Custom" => Ok(Attribute::Custom),
+                _ => anyhow::bail!("ExtendedAttributeNoArgs not supported: {:?}", (attr.0).0),
+            },
+            // Matches assignment-style attributes like ["Throws=Error"]
+            weedle::attribute::ExtendedAttribute::Ident(identity) => {
+                match identity.lhs_identifier.0 {
+                    "Name" => Ok(Attribute::Name(name_from_id_or_string(&identity.rhs))),
+                    "Throws" => Ok(Attribute::Throws(name_from_id_or_string(&identity.rhs))),
+                    "Self" => Ok(Attribute::SelfType(SelfType::try_from(&identity.rhs)?)),
+                    "External" => Ok(Attribute::External(name_from_id_or_string(&identity.rhs))),
+                    _ => anyhow::bail!(
+                        "Attribute identity Identifier not supported: {:?}",
+                        identity.lhs_identifier.0
+                    ),
+                }
+            }
+            _ => anyhow::bail!("Attribute not supported: {:?}", weedle_attribute),
+        }
+    }
+}
+
+fn name_from_id_or_string(nm: &weedle::attribute::IdentifierOrString<'_>) -> String {
+    match nm {
+        weedle::attribute::IdentifierOrString::Identifier(identifier) => identifier.0.to_string(),
+        weedle::attribute::IdentifierOrString::String(str_lit) => str_lit.0.to_string(),
+    }
+}
+
+/// Parse a weedle `ExtendedAttributeList` into a list of `Attribute`s,
+/// erroring out on duplicates.
+fn parse_attributes<F>(
+    weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    validator: F,
+) -> Result<Vec<Attribute>>
+where
+    F: Fn(&Attribute) -> Result<()>,
+{
+    let attrs = &weedle_attributes.body.list;
+
+    let mut hash_set = std::collections::HashSet::new();
+    for attr in attrs {
+        if !hash_set.insert(attr) {
+            anyhow::bail!("Duplicated ExtendedAttribute: {:?}", attr);
+        }
+    }
+
+    let attrs = attrs
+        .iter()
+        .map(Attribute::try_from)
+        .collect::<Result<Vec<_>, _>>()?;
+
+    for attr in &attrs {
+        validator(attr)?;
+    }
+
+    Ok(attrs)
+}
+
+/// Attributes that can be attached to an `enum` definition in the UDL.
+/// There's only one case here: using `[Error]` to mark an enum as an error class.
+#[derive(Debug, Clone, Checksum, Default)]
+pub(super) struct EnumAttributes(Vec<Attribute>);
+
+impl EnumAttributes {
+    pub fn contains_error_attr(&self) -> bool {
+        self.0.iter().any(|attr| attr.is_error())
+    }
+}
+
+impl TryFrom<&weedle::attribute::ExtendedAttributeList<'_>> for EnumAttributes {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    ) -> Result<Self, Self::Error> {
+        let attrs = parse_attributes(weedle_attributes, |attr| match attr {
+            Attribute::Error => Ok(()),
+            _ => bail!(format!("{:?} not supported for enums", attr)),
+        })?;
+        Ok(Self(attrs))
+    }
+}
+
+impl<T: TryInto<EnumAttributes, Error = anyhow::Error>> TryFrom<Option<T>> for EnumAttributes {
+    type Error = anyhow::Error;
+    fn try_from(value: Option<T>) -> Result<Self, Self::Error> {
+        match value {
+            None => Ok(Default::default()),
+            Some(v) => v.try_into(),
+        }
+    }
+}
+
+/// Represents UDL attributes that might appear on a function.
+///
+/// This supports the `[Throws=ErrorName]` attribute for functions that
+/// can produce an error.
+#[derive(Debug, Clone, Checksum, Default)]
+pub(super) struct FunctionAttributes(Vec<Attribute>);
+
+impl FunctionAttributes {
+    pub(super) fn get_throws_err(&self) -> Option<&str> {
+        self.0.iter().find_map(|attr| match attr {
+            // This will hopefully return a helpful compilation error
+            // if the error is not defined.
+            Attribute::Throws(inner) => Some(inner.as_ref()),
+            _ => None,
+        })
+    }
+}
+
+impl TryFrom<&weedle::attribute::ExtendedAttributeList<'_>> for FunctionAttributes {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    ) -> Result<Self, Self::Error> {
+        let attrs = parse_attributes(weedle_attributes, |attr| match attr {
+            Attribute::Throws(_) => Ok(()),
+            _ => bail!(format!("{:?} not supported for functions", attr)),
+        })?;
+        Ok(Self(attrs))
+    }
+}
+
+impl<T: TryInto<FunctionAttributes, Error = anyhow::Error>> TryFrom<Option<T>>
+    for FunctionAttributes
+{
+    type Error = anyhow::Error;
+    fn try_from(value: Option<T>) -> Result<Self, Self::Error> {
+        match value {
+            None => Ok(Default::default()),
+            Some(v) => v.try_into(),
+        }
+    }
+}
+
+/// Represents UDL attributes that might appear on a function argument.
+///
+/// This supports the `[ByRef]` attribute for arguments that should be passed
+/// by reference in the generated Rust scaffolding.
+#[derive(Debug, Clone, Checksum, Default)]
+pub(super) struct ArgumentAttributes(Vec<Attribute>);
+
+impl ArgumentAttributes {
+    pub fn by_ref(&self) -> bool {
+        self.0.iter().any(|attr| matches!(attr, Attribute::ByRef))
+    }
+}
+
+impl TryFrom<&weedle::attribute::ExtendedAttributeList<'_>> for ArgumentAttributes {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    ) -> Result<Self, Self::Error> {
+        let attrs = parse_attributes(weedle_attributes, |attr| match attr {
+            Attribute::ByRef => Ok(()),
+            _ => bail!(format!("{:?} not supported for arguments", attr)),
+        })?;
+        Ok(Self(attrs))
+    }
+}
+
+impl<T: TryInto<ArgumentAttributes, Error = anyhow::Error>> TryFrom<Option<T>>
+    for ArgumentAttributes
+{
+    type Error = anyhow::Error;
+    fn try_from(value: Option<T>) -> Result<Self, Self::Error> {
+        match value {
+            None => Ok(Default::default()),
+            Some(v) => v.try_into(),
+        }
+    }
+}
+
+/// Represents UDL attributes that might appear on an `interface` definition.
+#[derive(Debug, Clone, Checksum, Default)]
+pub(super) struct InterfaceAttributes(Vec<Attribute>);
+
+impl InterfaceAttributes {
+    pub fn contains_enum_attr(&self) -> bool {
+        self.0.iter().any(|attr| attr.is_enum())
+    }
+
+    pub fn contains_error_attr(&self) -> bool {
+        self.0.iter().any(|attr| attr.is_error())
+    }
+
+    pub fn threadsafe(&self) -> bool {
+        self.0
+            .iter()
+            .any(|attr| matches!(attr, Attribute::Threadsafe))
+    }
+}
+
+impl TryFrom<&weedle::attribute::ExtendedAttributeList<'_>> for InterfaceAttributes {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    ) -> Result<Self, Self::Error> {
+        let attrs = parse_attributes(weedle_attributes, |attr| match attr {
+            Attribute::Enum => Ok(()),
+            Attribute::Error => Ok(()),
+            Attribute::Threadsafe => Ok(()),
+            _ => bail!(format!("{:?} not supported for interface definition", attr)),
+        })?;
+        // Can't be both `[Threadsafe]` and an `[Enum]`.
+        if attrs.len() > 1 {
+            bail!("conflicting attributes on interface definition");
+        }
+        Ok(Self(attrs))
+    }
+}
+
+impl<T: TryInto<InterfaceAttributes, Error = anyhow::Error>> TryFrom<Option<T>>
+    for InterfaceAttributes
+{
+    type Error = anyhow::Error;
+    fn try_from(value: Option<T>) -> Result<Self, Self::Error> {
+        match value {
+            None => Ok(Default::default()),
+            Some(v) => v.try_into(),
+        }
+    }
+}
+
+/// Represents UDL attributes that might appear on a constructor.
+///
+/// This supports the `[Throws=ErrorName]` attribute for constructors that can produce
+/// an error, and the `[Name=MethodName]` for non-default constructors.
+#[derive(Debug, Clone, Checksum, Default)]
+pub(super) struct ConstructorAttributes(Vec<Attribute>);
+
+impl ConstructorAttributes {
+    pub(super) fn get_throws_err(&self) -> Option<&str> {
+        self.0.iter().find_map(|attr| match attr {
+            // This will hopefully return a helpful compilation error
+            // if the error is not defined.
+            Attribute::Throws(inner) => Some(inner.as_ref()),
+            _ => None,
+        })
+    }
+
+    pub(super) fn get_name(&self) -> Option<&str> {
+        self.0.iter().find_map(|attr| match attr {
+            Attribute::Name(inner) => Some(inner.as_ref()),
+            _ => None,
+        })
+    }
+}
+
+impl TryFrom<&weedle::attribute::ExtendedAttributeList<'_>> for ConstructorAttributes {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    ) -> Result<Self, Self::Error> {
+        let attrs = parse_attributes(weedle_attributes, |attr| match attr {
+            Attribute::Throws(_) => Ok(()),
+            Attribute::Name(_) => Ok(()),
+            _ => bail!(format!("{:?} not supported for constructors", attr)),
+        })?;
+        Ok(Self(attrs))
+    }
+}
+
+/// Represents UDL attributes that might appear on a method.
+///
+/// This supports the `[Throws=ErrorName]` attribute for methods that can produce
+/// an error, and the `[Self=ByArc]` attribute for methods that take `Arc<Self>` as receiver.
+#[derive(Debug, Clone, Checksum, Default)]
+pub(super) struct MethodAttributes(Vec<Attribute>);
+
+impl MethodAttributes {
+    pub(super) fn get_throws_err(&self) -> Option<&str> {
+        self.0.iter().find_map(|attr| match attr {
+            // This will hopefully return a helpful compilation error
+            // if the error is not defined.
+            Attribute::Throws(inner) => Some(inner.as_ref()),
+            _ => None,
+        })
+    }
+
+    pub(super) fn get_self_by_arc(&self) -> bool {
+        self.0
+            .iter()
+            .any(|attr| matches!(attr, Attribute::SelfType(SelfType::ByArc)))
+    }
+}
+
+impl TryFrom<&weedle::attribute::ExtendedAttributeList<'_>> for MethodAttributes {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    ) -> Result<Self, Self::Error> {
+        let attrs = parse_attributes(weedle_attributes, |attr| match attr {
+            Attribute::SelfType(_) => Ok(()),
+            Attribute::Throws(_) => Ok(()),
+            _ => bail!(format!("{:?} not supported for methods", attr)),
+        })?;
+        Ok(Self(attrs))
+    }
+}
+
+impl<T: TryInto<MethodAttributes, Error = anyhow::Error>> TryFrom<Option<T>> for MethodAttributes {
+    type Error = anyhow::Error;
+    fn try_from(value: Option<T>) -> Result<Self, Self::Error> {
+        match value {
+            None => Ok(Default::default()),
+            Some(v) => v.try_into(),
+        }
+    }
+}
+
+/// Represents the different possible types of method call receiver.
+///
+/// Actually we only support one of these right now, `[Self=ByArc]`.
+/// We might add more in future, e.g. a `[Self=ByRef]` if there are cases
+/// where we need to force the receiver to be taken by reference.
+#[derive(Debug, Clone, Checksum)]
+pub(super) enum SelfType {
+    ByArc, // Method receiver is `Arc<Self>`.
+}
+
+impl TryFrom<&weedle::attribute::IdentifierOrString<'_>> for SelfType {
+    type Error = anyhow::Error;
+    fn try_from(nm: &weedle::attribute::IdentifierOrString<'_>) -> Result<Self, Self::Error> {
+        Ok(match nm {
+            weedle::attribute::IdentifierOrString::Identifier(identifier) => match identifier.0 {
+                "ByArc" => SelfType::ByArc,
+                _ => bail!("Unsupported Self Type: {:?}", identifier.0),
+            },
+            weedle::attribute::IdentifierOrString::String(_) => {
+                bail!("Unsupported Self Type: {:?}", nm)
+            }
+        })
+    }
+}
+
+/// Represents UDL attributes that might appear on a typedef
+///
+/// This supports the `[External="crate_name"]` and `[Custom]` attributes for types.
+#[derive(Debug, Clone, Checksum, Default)]
+pub(super) struct TypedefAttributes(Vec<Attribute>);
+
+impl TypedefAttributes {
+    pub(super) fn get_crate_name(&self) -> String {
+        self.0
+            .iter()
+            .find_map(|attr| match attr {
+                Attribute::External(crate_name) => Some(crate_name.clone()),
+                _ => None,
+            })
+            .expect("must have a crate name")
+    }
+
+    pub(super) fn is_custom(&self) -> bool {
+        self.0
+            .iter()
+            .any(|attr| matches!(attr, Attribute::Custom { .. }))
+    }
+}
+
+impl TryFrom<&weedle::attribute::ExtendedAttributeList<'_>> for TypedefAttributes {
+    type Error = anyhow::Error;
+    fn try_from(
+        weedle_attributes: &weedle::attribute::ExtendedAttributeList<'_>,
+    ) -> Result<Self, Self::Error> {
+        let attrs = parse_attributes(weedle_attributes, |attr| match attr {
+            Attribute::External { .. } | Attribute::Custom => Ok(()),
+            _ => bail!(format!("{:?} not supported for typedefs", attr)),
+        })?;
+        Ok(Self(attrs))
+    }
+}
+
+impl<T: TryInto<TypedefAttributes, Error = anyhow::Error>> TryFrom<Option<T>>
+    for TypedefAttributes
+{
+    type Error = anyhow::Error;
+    fn try_from(value: Option<T>) -> Result<Self, Self::Error> {
+        match value {
+            None => Ok(Default::default()),
+            Some(v) => v.try_into(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use weedle::Parse;
+
+    #[test]
+    fn test_byref() -> Result<()> {
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("ByRef").unwrap();
+        let attr = Attribute::try_from(&node)?;
+        assert!(matches!(attr, Attribute::ByRef));
+        Ok(())
+    }
+
+    #[test]
+    fn test_enum() -> Result<()> {
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Enum").unwrap();
+        let attr = Attribute::try_from(&node)?;
+        assert!(matches!(attr, Attribute::Enum));
+        assert!(attr.is_enum());
+        Ok(())
+    }
+
+    #[test]
+    fn test_error() -> Result<()> {
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Error").unwrap();
+        let attr = Attribute::try_from(&node)?;
+        assert!(matches!(attr, Attribute::Error));
+        assert!(attr.is_error());
+        Ok(())
+    }
+
+    #[test]
+    fn test_name() -> Result<()> {
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Name=Value").unwrap();
+        let attr = Attribute::try_from(&node)?;
+        assert!(matches!(attr, Attribute::Name(nm) if nm == "Value"));
+
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Name").unwrap();
+        let err = Attribute::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "ExtendedAttributeNoArgs not supported: \"Name\""
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_selftype() -> Result<()> {
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Self=ByArc").unwrap();
+        let attr = Attribute::try_from(&node)?;
+        assert!(matches!(attr, Attribute::SelfType(SelfType::ByArc)));
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Self=ByMistake").unwrap();
+        let err = Attribute::try_from(&node).unwrap_err();
+        assert_eq!(err.to_string(), "Unsupported Self Type: \"ByMistake\"");
+        Ok(())
+    }
+
+    #[test]
+    fn test_threadsafe() -> Result<()> {
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Threadsafe").unwrap();
+        let attr = Attribute::try_from(&node)?;
+        assert!(matches!(attr, Attribute::Threadsafe));
+        Ok(())
+    }
+
+    #[test]
+    fn test_throws() -> Result<()> {
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Throws=Name").unwrap();
+        let attr = Attribute::try_from(&node)?;
+        assert!(matches!(attr, Attribute::Throws(nm) if nm == "Name"));
+
+        let (_, node) = weedle::attribute::ExtendedAttribute::parse("Throws").unwrap();
+        let err = Attribute::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "ExtendedAttributeNoArgs not supported: \"Throws\""
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_unsupported() {
+        let (_, node) =
+            weedle::attribute::ExtendedAttribute::parse("UnsupportedAttribute").unwrap();
+        let err = Attribute::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "ExtendedAttributeNoArgs not supported: \"UnsupportedAttribute\""
+        );
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttribute::parse("Unsupported=Attribute").unwrap();
+        let err = Attribute::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Attribute identity Identifier not supported: \"Unsupported\""
+        );
+    }
+
+    #[test]
+    fn test_other_attributes_not_supported_for_enums() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Error, ByRef]").unwrap();
+        let err = EnumAttributes::try_from(&node).unwrap_err();
+        assert_eq!(err.to_string(), "ByRef not supported for enums");
+    }
+
+    #[test]
+    fn test_throws_attribute() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Throws=Error]").unwrap();
+        let attrs = FunctionAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.get_throws_err(), Some("Error")));
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[]").unwrap();
+        let attrs = FunctionAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.get_throws_err(), None));
+    }
+
+    #[test]
+    fn test_other_attributes_not_supported_for_functions() {
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Throws=Error, ByRef]").unwrap();
+        let err = FunctionAttributes::try_from(&node).unwrap_err();
+        assert_eq!(err.to_string(), "ByRef not supported for functions");
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Throws=Error, Self=ByArc]").unwrap();
+        let err = FunctionAttributes::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "SelfType(ByArc) not supported for functions"
+        );
+    }
+
+    #[test]
+    fn test_method_attributes() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Throws=Error]").unwrap();
+        let attrs = MethodAttributes::try_from(&node).unwrap();
+        assert!(!attrs.get_self_by_arc());
+        assert!(matches!(attrs.get_throws_err(), Some("Error")));
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[]").unwrap();
+        let attrs = MethodAttributes::try_from(&node).unwrap();
+        assert!(!attrs.get_self_by_arc());
+        assert!(attrs.get_throws_err().is_none());
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Self=ByArc, Throws=Error]").unwrap();
+        let attrs = MethodAttributes::try_from(&node).unwrap();
+        assert!(attrs.get_self_by_arc());
+        assert!(attrs.get_throws_err().is_some());
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Self=ByArc]").unwrap();
+        let attrs = MethodAttributes::try_from(&node).unwrap();
+        assert!(attrs.get_self_by_arc());
+        assert!(attrs.get_throws_err().is_none());
+    }
+
+    #[test]
+    fn test_constructor_attributes() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Throws=Error]").unwrap();
+        let attrs = ConstructorAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.get_throws_err(), Some("Error")));
+        assert!(matches!(attrs.get_name(), None));
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Name=MyFactory]").unwrap();
+        let attrs = ConstructorAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.get_throws_err(), None));
+        assert!(matches!(attrs.get_name(), Some("MyFactory")));
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Throws=Error, Name=MyFactory]")
+                .unwrap();
+        let attrs = ConstructorAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.get_throws_err(), Some("Error")));
+        assert!(matches!(attrs.get_name(), Some("MyFactory")));
+    }
+
+    #[test]
+    fn test_other_attributes_not_supported_for_constructors() {
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Throws=Error, ByRef]").unwrap();
+        let err = ConstructorAttributes::try_from(&node).unwrap_err();
+        assert_eq!(err.to_string(), "ByRef not supported for constructors");
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Throws=Error, Self=ByArc]").unwrap();
+        let err = ConstructorAttributes::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "SelfType(ByArc) not supported for constructors"
+        );
+    }
+
+    #[test]
+    fn test_byref_attribute() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[ByRef]").unwrap();
+        let attrs = ArgumentAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.by_ref(), true));
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[]").unwrap();
+        let attrs = ArgumentAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.by_ref(), false));
+    }
+
+    #[test]
+    fn test_other_attributes_not_supported_for_arguments() {
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Throws=Error, ByRef]").unwrap();
+        let err = ArgumentAttributes::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Throws(\"Error\") not supported for arguments"
+        );
+    }
+
+    #[test]
+    fn test_threadsafe_attribute() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Threadsafe]").unwrap();
+        let attrs = InterfaceAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.threadsafe(), true));
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[]").unwrap();
+        let attrs = InterfaceAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.threadsafe(), false));
+    }
+
+    #[test]
+    fn test_enum_attribute() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Enum]").unwrap();
+        let attrs = InterfaceAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.contains_enum_attr(), true));
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[]").unwrap();
+        let attrs = InterfaceAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.contains_enum_attr(), false));
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Threadsafe]").unwrap();
+        let attrs = InterfaceAttributes::try_from(&node).unwrap();
+        assert!(matches!(attrs.contains_enum_attr(), false));
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Threadsafe, Enum]").unwrap();
+        let err = InterfaceAttributes::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "conflicting attributes on interface definition"
+        );
+    }
+
+    #[test]
+    fn test_other_attributes_not_supported_for_interfaces() {
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[Threadsafe, ByRef]").unwrap();
+        let err = InterfaceAttributes::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "ByRef not supported for interface definition"
+        );
+    }
+
+    #[test]
+    fn test_typedef_attribute() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Custom]").unwrap();
+        let attrs = TypedefAttributes::try_from(&node).unwrap();
+        assert!(attrs.is_custom());
+
+        let (_, node) =
+            weedle::attribute::ExtendedAttributeList::parse("[External=crate_name]").unwrap();
+        let attrs = TypedefAttributes::try_from(&node).unwrap();
+        assert!(!attrs.is_custom());
+        assert_eq!(attrs.get_crate_name(), "crate_name");
+    }
+
+    #[test]
+    fn test_typedef_attributes_malformed() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[Custom=foo]").unwrap();
+        let err = TypedefAttributes::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Attribute identity Identifier not supported: \"Custom\""
+        );
+
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[External]").unwrap();
+        let err = TypedefAttributes::try_from(&node).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "ExtendedAttributeNoArgs not supported: \"External\""
+        );
+    }
+
+    #[test]
+    fn test_other_attributes_not_supported_for_typedef() {
+        let (_, node) = weedle::attribute::ExtendedAttributeList::parse("[ByRef]").unwrap();
+        let err = TypedefAttributes::try_from(&node).unwrap_err();
+        assert_eq!(err.to_string(), "ByRef not supported for typedefs");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/callbacks.rs b/third_party/rust/uniffi_bindgen/src/interface/callbacks.rs
new file mode 100644
index 0000000000..0bbbd4cb05
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/callbacks.rs
@@ -0,0 +1,169 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Callback Interface definitions for a `ComponentInterface`.
+//!
+//! This module converts callback interface definitions from UDL into structures that
+//! can be added to a `ComponentInterface`. A declaration in the UDL like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! callback interface Example {
+//!   string hello();
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in a [`CallbackInterface`] member being added to the resulting
+//! [`ComponentInterface`]:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # callback interface Example {
+//! #  string hello();
+//! # };
+//! # "##)?;
+//! let callback = ci.get_callback_interface_definition("Example").unwrap();
+//! assert_eq!(callback.name(), "Example");
+//! assert_eq!(callback.methods()[0].name(), "hello");
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+
+use anyhow::{bail, Result};
+use uniffi_meta::Checksum;
+
+use super::ffi::{FFIArgument, FFIFunction, FFIType};
+use super::object::Method;
+use super::types::{Type, TypeIterator};
+use super::{APIConverter, ComponentInterface};
+
+#[derive(Debug, Clone, Checksum)]
+pub struct CallbackInterface {
+    pub(super) name: String,
+    pub(super) methods: Vec<Method>,
+    // We don't include the FFIFunc in the hash calculation, because:
+    //  - it is entirely determined by the other fields,
+    //    so excluding it is safe.
+    //  - its `name` property includes a checksum derived from  the very
+    //    hash value we're trying to calculate here, so excluding it
+    //    avoids a weird circular depenendency in the calculation.
+    #[checksum_ignore]
+    pub(super) ffi_init_callback: FFIFunction,
+}
+
+impl CallbackInterface {
+    fn new(name: String) -> CallbackInterface {
+        CallbackInterface {
+            name,
+            methods: Default::default(),
+            ffi_init_callback: Default::default(),
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn type_(&self) -> Type {
+        Type::CallbackInterface(self.name.clone())
+    }
+
+    pub fn methods(&self) -> Vec<&Method> {
+        self.methods.iter().collect()
+    }
+
+    pub fn ffi_init_callback(&self) -> &FFIFunction {
+        &self.ffi_init_callback
+    }
+
+    pub(super) fn derive_ffi_funcs(&mut self, ci_prefix: &str) {
+        self.ffi_init_callback.name = format!("ffi_{ci_prefix}_{}_init_callback", self.name);
+        self.ffi_init_callback.arguments = vec![FFIArgument {
+            name: "callback_stub".to_string(),
+            type_: FFIType::ForeignCallback,
+        }];
+        self.ffi_init_callback.return_type = None;
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        Box::new(self.methods.iter().flat_map(Method::iter_types))
+    }
+}
+
+impl APIConverter<CallbackInterface> for weedle::CallbackInterfaceDefinition<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<CallbackInterface> {
+        if self.attributes.is_some() {
+            bail!("callback interface attributes are not supported yet");
+        }
+        if self.inheritance.is_some() {
+            bail!("callback interface inheritence is not supported");
+        }
+        let mut object = CallbackInterface::new(self.identifier.0.to_string());
+        for member in &self.members.body {
+            match member {
+                weedle::interface::InterfaceMember::Operation(t) => {
+                    let mut method: Method = t.convert(ci)?;
+                    method.object_name = object.name.clone();
+                    object.methods.push(method);
+                }
+                _ => bail!(
+                    "no support for callback interface member type {:?} yet",
+                    member
+                ),
+            }
+        }
+        Ok(object)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_empty_interface() {
+        const UDL: &str = r#"
+            namespace test{};
+            // Weird, but allowed.
+            callback interface Testing {};
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.callback_interface_definitions().len(), 1);
+        assert_eq!(
+            ci.get_callback_interface_definition("Testing")
+                .unwrap()
+                .methods()
+                .len(),
+            0
+        );
+    }
+
+    #[test]
+    fn test_multiple_interfaces() {
+        const UDL: &str = r#"
+            namespace test{};
+            callback interface One {
+                void one();
+            };
+            callback interface Two {
+                u32 two();
+                u64 too();
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.callback_interface_definitions().len(), 2);
+
+        let callbacks_one = ci.get_callback_interface_definition("One").unwrap();
+        assert_eq!(callbacks_one.methods().len(), 1);
+        assert_eq!(callbacks_one.methods()[0].name(), "one");
+
+        let callbacks_two = ci.get_callback_interface_definition("Two").unwrap();
+        assert_eq!(callbacks_two.methods().len(), 2);
+        assert_eq!(callbacks_two.methods()[0].name(), "two");
+        assert_eq!(callbacks_two.methods()[1].name(), "too");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/enum_.rs b/third_party/rust/uniffi_bindgen/src/interface/enum_.rs
new file mode 100644
index 0000000000..b8fe0ddd73
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/enum_.rs
@@ -0,0 +1,415 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Enum definitions for a `ComponentInterface`.
+//!
+//! This module converts enum definition from UDL into structures that can be
+//! added to a `ComponentInterface`. A declaration in the UDL like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! enum Example {
+//!   "one",
+//!   "two"
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in a [`Enum`] member being added to the resulting [`ComponentInterface`]:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # enum Example {
+//! #   "one",
+//! #   "two"
+//! # };
+//! # "##)?;
+//! let e = ci.get_enum_definition("Example").unwrap();
+//! assert_eq!(e.name(), "Example");
+//! assert_eq!(e.variants().len(), 2);
+//! assert_eq!(e.variants()[0].name(), "one");
+//! assert_eq!(e.variants()[1].name(), "two");
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Like in Rust, UniFFI enums can contain associated data, but this needs to be
+//! declared with a different syntax in order to work within the restrictions of
+//! WebIDL. A declaration like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! [Enum]
+//! interface Example {
+//!   Zero();
+//!   One(u32 first);
+//!   Two(u32 first, string second);
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in an [`Enum`] member whose variants have associated fields:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # [Enum]
+//! # interface ExampleWithData {
+//! #   Zero();
+//! #   One(u32 first);
+//! #   Two(u32 first, string second);
+//! # };
+//! # "##)?;
+//! let e = ci.get_enum_definition("ExampleWithData").unwrap();
+//! assert_eq!(e.name(), "ExampleWithData");
+//! assert_eq!(e.variants().len(), 3);
+//! assert_eq!(e.variants()[0].name(), "Zero");
+//! assert_eq!(e.variants()[0].fields().len(), 0);
+//! assert_eq!(e.variants()[1].name(), "One");
+//! assert_eq!(e.variants()[1].fields().len(), 1);
+//! assert_eq!(e.variants()[1].fields()[0].name(), "first");
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+
+use anyhow::{bail, Result};
+use uniffi_meta::Checksum;
+
+use super::record::Field;
+use super::types::{Type, TypeIterator};
+use super::{APIConverter, ComponentInterface};
+
+/// Represents an enum with named variants, each of which may have named
+/// and typed fields.
+///
+/// Enums are passed across the FFI by serializing to a bytebuffer, with a
+/// i32 indicating the variant followed by the serialization of each field.
+#[derive(Debug, Clone, Checksum)]
+pub struct Enum {
+    pub(super) name: String,
+    pub(super) variants: Vec<Variant>,
+    // "Flat" enums do not have, and will never have, variants with associated data.
+    pub(super) flat: bool,
+}
+
+impl Enum {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn type_(&self) -> Type {
+        // *sigh* at the clone here, the relationship between a ComponentInterace
+        // and its contained types could use a bit of a cleanup.
+        Type::Enum(self.name.clone())
+    }
+
+    pub fn variants(&self) -> Vec<&Variant> {
+        self.variants.iter().collect()
+    }
+
+    pub fn is_flat(&self) -> bool {
+        self.flat
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        Box::new(self.variants.iter().flat_map(Variant::iter_types))
+    }
+}
+
+// Note that we have two `APIConverter` impls here - one for the `enum` case
+// and one for the `[Enum] interface` case.
+
+impl APIConverter<Enum> for weedle::EnumDefinition<'_> {
+    fn convert(&self, _ci: &mut ComponentInterface) -> Result<Enum> {
+        Ok(Enum {
+            name: self.identifier.0.to_string(),
+            variants: self
+                .values
+                .body
+                .list
+                .iter()
+                .map::<Result<_>, _>(|v| {
+                    Ok(Variant {
+                        name: v.0.to_string(),
+                        ..Default::default()
+                    })
+                })
+                .collect::<Result<Vec<_>>>()?,
+            // Enums declared using the `enum` syntax can never have variants with fields.
+            flat: true,
+        })
+    }
+}
+
+impl APIConverter<Enum> for weedle::InterfaceDefinition<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Enum> {
+        if self.inheritance.is_some() {
+            bail!("interface inheritence is not supported for enum interfaces");
+        }
+        // We don't need to check `self.attributes` here; if calling code has dispatched
+        // to this impl then we already know there was an `[Enum]` attribute.
+        Ok(Enum {
+            name: self.identifier.0.to_string(),
+            variants: self
+                .members
+                .body
+                .iter()
+                .map::<Result<Variant>, _>(|member| match member {
+                    weedle::interface::InterfaceMember::Operation(t) => Ok(t.convert(ci)?),
+                    _ => bail!(
+                        "interface member type {:?} not supported in enum interface",
+                        member
+                    ),
+                })
+                .collect::<Result<Vec<_>>>()?,
+            // Enums declared using the `[Enum] interface` syntax might have variants with fields.
+            flat: false,
+        })
+    }
+}
+
+/// Represents an individual variant in an Enum.
+///
+/// Each variant has a name and zero or more fields.
+#[derive(Debug, Clone, Default, Checksum)]
+pub struct Variant {
+    pub(super) name: String,
+    pub(super) fields: Vec<Field>,
+}
+
+impl Variant {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+    pub fn fields(&self) -> Vec<&Field> {
+        self.fields.iter().collect()
+    }
+
+    pub fn has_fields(&self) -> bool {
+        !self.fields.is_empty()
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        Box::new(self.fields.iter().flat_map(Field::iter_types))
+    }
+}
+
+impl APIConverter<Variant> for weedle::interface::OperationInterfaceMember<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Variant> {
+        if self.special.is_some() {
+            bail!("special operations not supported");
+        }
+        if let Some(weedle::interface::StringifierOrStatic::Stringifier(_)) = self.modifier {
+            bail!("stringifiers are not supported");
+        }
+        // OK, so this is a little weird.
+        // The syntax we use for enum interface members is `Name(type arg, ...);`, which parses
+        // as an anonymous operation where `Name` is the return type. We re-interpret it to
+        // use `Name` as the name of the variant.
+        if self.identifier.is_some() {
+            bail!("enum interface members must not have a method name");
+        }
+        let name: String = {
+            use weedle::types::{
+                NonAnyType::Identifier, ReturnType, SingleType::NonAny, Type::Single,
+            };
+            match &self.return_type {
+                ReturnType::Type(Single(NonAny(Identifier(id)))) => id.type_.0.to_owned(),
+                _ => bail!("enum interface members must have plain identifers as names"),
+            }
+        };
+        Ok(Variant {
+            name,
+            fields: self
+                .args
+                .body
+                .list
+                .iter()
+                .map(|arg| arg.convert(ci))
+                .collect::<Result<Vec<_>>>()?,
+        })
+    }
+}
+
+impl APIConverter<Field> for weedle::argument::Argument<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Field> {
+        match self {
+            weedle::argument::Argument::Single(t) => t.convert(ci),
+            weedle::argument::Argument::Variadic(_) => bail!("variadic arguments not supported"),
+        }
+    }
+}
+
+impl APIConverter<Field> for weedle::argument::SingleArgument<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Field> {
+        let type_ = ci.resolve_type_expression(&self.type_)?;
+        if let Type::Object(_) = type_ {
+            bail!("Objects cannot currently be used in enum variant data");
+        }
+        if self.default.is_some() {
+            bail!("enum interface variant fields must not have default values");
+        }
+        if self.attributes.is_some() {
+            bail!("enum interface variant fields must not have attributes");
+        }
+        // TODO: maybe we should use our own `Field` type here with just name and type,
+        // rather than appropriating record::Field..?
+        Ok(Field {
+            name: self.identifier.0.to_string(),
+            type_,
+            required: false,
+            default: None,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::super::ffi::FFIType;
+    use super::*;
+
+    #[test]
+    fn test_duplicate_variants() {
+        const UDL: &str = r#"
+            namespace test{};
+            // Weird, but currently allowed!
+            // We should probably disallow this...
+            enum Testing { "one", "two", "one" };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.enum_definitions().len(), 1);
+        assert_eq!(
+            ci.get_enum_definition("Testing").unwrap().variants().len(),
+            3
+        );
+    }
+
+    #[test]
+    fn test_associated_data() {
+        const UDL: &str = r##"
+            namespace test {
+                void takes_an_enum(TestEnum e);
+                void takes_an_enum_with_data(TestEnumWithData ed);
+                TestEnum returns_an_enum();
+                TestEnumWithData returns_an_enum_with_data();
+            };
+
+            enum TestEnum { "one", "two" };
+
+            [Enum]
+            interface TestEnumWithData {
+                Zero();
+                One(u32 first);
+                Two(u32 first, string second);
+            };
+
+            [Enum]
+            interface TestEnumWithoutData {
+                One();
+                Two();
+            };
+        "##;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.enum_definitions().len(), 3);
+        assert_eq!(ci.function_definitions().len(), 4);
+
+        // The "flat" enum with no associated data.
+        let e = ci.get_enum_definition("TestEnum").unwrap();
+        assert!(e.is_flat());
+        assert_eq!(e.variants().len(), 2);
+        assert_eq!(
+            e.variants().iter().map(|v| v.name()).collect::<Vec<_>>(),
+            vec!["one", "two"]
+        );
+        assert_eq!(e.variants()[0].fields().len(), 0);
+        assert_eq!(e.variants()[1].fields().len(), 0);
+
+        // The enum with associated data.
+        let ed = ci.get_enum_definition("TestEnumWithData").unwrap();
+        assert!(!ed.is_flat());
+        assert_eq!(ed.variants().len(), 3);
+        assert_eq!(
+            ed.variants().iter().map(|v| v.name()).collect::<Vec<_>>(),
+            vec!["Zero", "One", "Two"]
+        );
+        assert_eq!(ed.variants()[0].fields().len(), 0);
+        assert_eq!(
+            ed.variants()[1]
+                .fields()
+                .iter()
+                .map(|f| f.name())
+                .collect::<Vec<_>>(),
+            vec!["first"]
+        );
+        assert_eq!(
+            ed.variants()[1]
+                .fields()
+                .iter()
+                .map(|f| f.type_())
+                .collect::<Vec<_>>(),
+            vec![&Type::UInt32]
+        );
+        assert_eq!(
+            ed.variants()[2]
+                .fields()
+                .iter()
+                .map(|f| f.name())
+                .collect::<Vec<_>>(),
+            vec!["first", "second"]
+        );
+        assert_eq!(
+            ed.variants()[2]
+                .fields()
+                .iter()
+                .map(|f| f.type_())
+                .collect::<Vec<_>>(),
+            vec![&Type::UInt32, &Type::String]
+        );
+
+        // The enum declared via interface, but with no associated data.
+        let ewd = ci.get_enum_definition("TestEnumWithoutData").unwrap();
+        assert!(!ewd.is_flat());
+        assert_eq!(ewd.variants().len(), 2);
+        assert_eq!(
+            ewd.variants().iter().map(|v| v.name()).collect::<Vec<_>>(),
+            vec!["One", "Two"]
+        );
+        assert_eq!(ewd.variants()[0].fields().len(), 0);
+        assert_eq!(ewd.variants()[1].fields().len(), 0);
+
+        // Flat enums pass over the FFI as bytebuffers.
+        // (It might be nice to optimize these to pass as plain integers, but that's
+        // difficult atop the current factoring of `ComponentInterface` and friends).
+        let farg = ci.get_function_definition("takes_an_enum").unwrap();
+        assert_eq!(*farg.arguments()[0].type_(), Type::Enum("TestEnum".into()));
+        assert_eq!(farg.ffi_func().arguments()[0].type_(), FFIType::RustBuffer);
+        let fret = ci.get_function_definition("returns_an_enum").unwrap();
+        assert!(matches!(fret.return_type(), Some(Type::Enum(nm)) if nm == "TestEnum"));
+        assert!(matches!(
+            fret.ffi_func().return_type(),
+            Some(FFIType::RustBuffer)
+        ));
+
+        // Enums with associated data pass over the FFI as bytebuffers.
+        let farg = ci
+            .get_function_definition("takes_an_enum_with_data")
+            .unwrap();
+        assert_eq!(
+            *farg.arguments()[0].type_(),
+            Type::Enum("TestEnumWithData".into())
+        );
+        assert_eq!(farg.ffi_func().arguments()[0].type_(), FFIType::RustBuffer);
+        let fret = ci
+            .get_function_definition("returns_an_enum_with_data")
+            .unwrap();
+        assert!(matches!(fret.return_type(), Some(Type::Enum(nm)) if nm == "TestEnumWithData"));
+        assert!(matches!(
+            fret.ffi_func().return_type(),
+            Some(FFIType::RustBuffer)
+        ));
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/error.rs b/third_party/rust/uniffi_bindgen/src/interface/error.rs
new file mode 100644
index 0000000000..adae769f01
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/error.rs
@@ -0,0 +1,217 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Error definitions for a `ComponentInterface`.
+//!
+//! This module converts error definition from UDL into structures that can be
+//! added to a `ComponentInterface`. A declaration in the UDL like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! [Error]
+//! enum Example {
+//!   "one",
+//!   "two"
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in an [`Error`] member with fieldless variants being added to the resulting [`ComponentInterface`]:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # [Error]
+//! # enum Example {
+//! #   "one",
+//! #   "two"
+//! # };
+//! # "##)?;
+//! let err = ci.get_error_definition("Example").unwrap();
+//! assert_eq!(err.name(), "Example");
+//! assert_eq!(err.variants().len(), 2);
+//! assert_eq!(err.variants()[0].name(), "one");
+//! assert_eq!(err.variants()[1].name(), "two");
+//! assert_eq!(err.is_flat(), true);
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! A declaration in the UDL like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! [Error]
+//! interface Example {
+//!   one(i16 code);
+//!   two(string reason);
+//!   three(i32 x, i32 y);
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in an [`Error`] member with variants that have fields being added to the resulting [`ComponentInterface`]:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # [Error]
+//! # interface Example {
+//! #   one();
+//! #   two(string reason);
+//! #   three(i32 x, i32 y);
+//! # };
+//! # "##)?;
+//! let err = ci.get_error_definition("Example").unwrap();
+//! assert_eq!(err.name(), "Example");
+//! assert_eq!(err.variants().len(), 3);
+//! assert_eq!(err.variants()[0].name(), "one");
+//! assert_eq!(err.variants()[1].name(), "two");
+//! assert_eq!(err.variants()[2].name(), "three");
+//! assert_eq!(err.variants()[0].fields().len(), 0);
+//! assert_eq!(err.variants()[1].fields().len(), 1);
+//! assert_eq!(err.variants()[1].fields()[0].name(), "reason");
+//! assert_eq!(err.variants()[2].fields().len(), 2);
+//! assert_eq!(err.variants()[2].fields()[0].name(), "x");
+//! assert_eq!(err.variants()[2].fields()[1].name(), "y");
+//! assert_eq!(err.is_flat(), false);
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+
+use anyhow::Result;
+use uniffi_meta::Checksum;
+
+use super::enum_::{Enum, Variant};
+use super::types::{Type, TypeIterator};
+use super::{APIConverter, ComponentInterface};
+
+/// Represents an Error that might be thrown by functions/methods in the component interface.
+///
+/// Errors are represented in the UDL as enums with the special `[Error]` attribute, but
+/// they're handled in the FFI very differently. We create them in `uniffi::call_with_result()` if
+/// the wrapped function returns an `Err` value
+/// struct and assign an integer error code to each variant.
+#[derive(Debug, Clone, Checksum)]
+pub struct Error {
+    pub name: String,
+    enum_: Enum,
+}
+
+impl Error {
+    pub fn from_enum(enum_: Enum) -> Self {
+        Self {
+            name: enum_.name.clone(),
+            enum_,
+        }
+    }
+
+    pub fn type_(&self) -> Type {
+        // *sigh* at the clone here, the relationship between a ComponentInterace
+        // and its contained types could use a bit of a cleanup.
+        Type::Error(self.name.clone())
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn wrapped_enum(&self) -> &Enum {
+        &self.enum_
+    }
+
+    pub fn variants(&self) -> Vec<&Variant> {
+        self.enum_.variants()
+    }
+
+    pub fn is_flat(&self) -> bool {
+        self.enum_.is_flat()
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        self.wrapped_enum().iter_types()
+    }
+}
+
+impl APIConverter<Error> for weedle::EnumDefinition<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Error> {
+        Ok(Error::from_enum(APIConverter::<Enum>::convert(self, ci)?))
+    }
+}
+
+impl APIConverter<Error> for weedle::InterfaceDefinition<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Error> {
+        Ok(Error::from_enum(APIConverter::<Enum>::convert(self, ci)?))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_variants() {
+        const UDL: &str = r#"
+            namespace test{};
+            [Error]
+            enum Testing { "one", "two", "three" };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.error_definitions().len(), 1);
+        let error = ci.get_error_definition("Testing").unwrap();
+        assert_eq!(
+            error
+                .variants()
+                .iter()
+                .map(|v| v.name())
+                .collect::<Vec<&str>>(),
+            vec!("one", "two", "three")
+        );
+        assert!(error.is_flat());
+    }
+
+    #[test]
+    fn test_duplicate_variants() {
+        const UDL: &str = r#"
+            namespace test{};
+            // Weird, but currently allowed!
+            // We should probably disallow this...
+            [Error]
+            enum Testing { "one", "two", "one" };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.error_definitions().len(), 1);
+        assert_eq!(
+            ci.get_error_definition("Testing").unwrap().variants().len(),
+            3
+        );
+    }
+
+    #[test]
+    fn test_variant_data() {
+        const UDL: &str = r#"
+            namespace test{};
+
+            [Error]
+            interface Testing {
+                One(string reason);
+                Two(u8 code);
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.error_definitions().len(), 1);
+        let error: &Error = ci.get_error_definition("Testing").unwrap();
+        assert_eq!(
+            error
+                .variants()
+                .iter()
+                .map(|v| v.name())
+                .collect::<Vec<&str>>(),
+            vec!("One", "Two")
+        );
+        assert!(!error.is_flat());
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/ffi.rs b/third_party/rust/uniffi_bindgen/src/interface/ffi.rs
new file mode 100644
index 0000000000..0ae98c9eab
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/ffi.rs
@@ -0,0 +1,100 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Low-level typesystem for the FFI layer of a component interface.
+//!
+//! This module provides the "FFI-level" typesystem of a UniFFI Rust Component, that is,
+//! the C-style functions and structs and primitive datatypes that are used to interface
+//! between the Rust component code and the foreign-language bindings.
+//!
+//! These types are purely an implementation detail of UniFFI, so consumers shouldn't
+//! need to know about them. But as a developer working on UniFFI itself, you're likely
+//! to spend a lot of time thinking about how these low-level types are used to represent
+//! the higher-level "interface types" from the [`super::types::Type`] enum.
+/// Represents the restricted set of low-level types that can be used to construct
+/// the C-style FFI layer between a rust component and its foreign language bindings.
+///
+/// For the types that involve memory allocation, we make a distinction between
+/// "owned" types (the recipient must free it, or pass it to someone else) and
+/// "borrowed" types (the sender must keep it alive for the duration of the call).
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
+pub enum FFIType {
+    // N.B. there are no booleans at this layer, since they cause problems for JNA.
+    UInt8,
+    Int8,
+    UInt16,
+    Int16,
+    UInt32,
+    Int32,
+    UInt64,
+    Int64,
+    Float32,
+    Float64,
+    /// A `*const c_void` pointer to a rust-owned `Arc<T>`.
+    /// If you've got one of these, you must call the appropriate rust function to free it.
+    /// The templates will generate a unique `free` function for each T.
+    /// The inner string references the name of the `T` type.
+    RustArcPtr(String),
+    /// A byte buffer allocated by rust, and owned by whoever currently holds it.
+    /// If you've got one of these, you must either call the appropriate rust function to free it
+    /// or pass it to someone that will.
+    RustBuffer,
+    /// A borrowed reference to some raw bytes owned by foreign language code.
+    /// The provider of this reference must keep it alive for the duration of the receiving call.
+    ForeignBytes,
+    /// A pointer to a single function in to the foreign language.
+    /// This function contains all the machinery to make callbacks work on the foreign language side.
+    ForeignCallback,
+    // TODO: you can imagine a richer structural typesystem here, e.g. `Ref<String>` or something.
+    // We don't need that yet and it's possible we never will, so it isn't here for now.
+}
+
+/// Represents an "extern C"-style function that will be part of the FFI.
+///
+/// These can't be declared explicitly in the UDL, but rather, are derived automatically
+/// from the high-level interface. Each callable thing in the component API will have a
+/// corresponding `FFIFunction` through which it can be invoked, and UniFFI also provides
+/// some built-in `FFIFunction` helpers for use in the foreign language bindings.
+#[derive(Debug, Default, Clone)]
+pub struct FFIFunction {
+    pub(super) name: String,
+    pub(super) arguments: Vec<FFIArgument>,
+    pub(super) return_type: Option<FFIType>,
+}
+
+impl FFIFunction {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+    pub fn arguments(&self) -> Vec<&FFIArgument> {
+        self.arguments.iter().collect()
+    }
+    pub fn return_type(&self) -> Option<&FFIType> {
+        self.return_type.as_ref()
+    }
+}
+
+/// Represents an argument to an FFI function.
+///
+/// Each argument has a name and a type.
+#[derive(Debug, Clone)]
+pub struct FFIArgument {
+    pub(super) name: String,
+    pub(super) type_: FFIType,
+}
+
+impl FFIArgument {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+    pub fn type_(&self) -> FFIType {
+        self.type_.clone()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    // There's not really much to test here to be honest,
+    // it's mostly type declarations.
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/function.rs b/third_party/rust/uniffi_bindgen/src/interface/function.rs
new file mode 100644
index 0000000000..30c2132e82
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/function.rs
@@ -0,0 +1,291 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Function definitions for a `ComponentInterface`.
+//!
+//! This module converts function definitions from UDL into structures that
+//! can be added to a `ComponentInterface`. A declaration in the UDL like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! namespace example {
+//!     string hello();
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in a [`Function`] member being added to the resulting [`ComponentInterface`]:
+//!
+//! ```
+//! # use uniffi_bindgen::interface::Type;
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {
+//! #     string hello();
+//! # };
+//! # "##)?;
+//! let func = ci.get_function_definition("hello").unwrap();
+//! assert_eq!(func.name(), "hello");
+//! assert!(matches!(func.return_type(), Some(Type::String)));
+//! assert_eq!(func.arguments().len(), 0);
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+use std::convert::TryFrom;
+
+use anyhow::{bail, Result};
+use uniffi_meta::Checksum;
+
+use super::ffi::{FFIArgument, FFIFunction};
+use super::literal::{convert_default_value, Literal};
+use super::types::{Type, TypeIterator};
+use super::{
+    attributes::{ArgumentAttributes, FunctionAttributes},
+    convert_type,
+};
+use super::{APIConverter, ComponentInterface};
+
+/// Represents a standalone function.
+///
+/// Each `Function` corresponds to a standalone function in the rust module,
+/// and has a corresponding standalone function in the foreign language bindings.
+///
+/// In the FFI, this will be a standalone function with appropriately lowered types.
+#[derive(Debug, Clone, Checksum)]
+pub struct Function {
+    pub(super) name: String,
+    pub(super) arguments: Vec<Argument>,
+    pub(super) return_type: Option<Type>,
+    // We don't include the FFIFunc in the hash calculation, because:
+    //  - it is entirely determined by the other fields,
+    //    so excluding it is safe.
+    //  - its `name` property includes a checksum derived from  the very
+    //    hash value we're trying to calculate here, so excluding it
+    //    avoids a weird circular depenendency in the calculation.
+    #[checksum_ignore]
+    pub(super) ffi_func: FFIFunction,
+    pub(super) attributes: FunctionAttributes,
+}
+
+impl Function {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn arguments(&self) -> Vec<&Argument> {
+        self.arguments.iter().collect()
+    }
+
+    pub fn full_arguments(&self) -> Vec<Argument> {
+        self.arguments.to_vec()
+    }
+
+    pub fn return_type(&self) -> Option<&Type> {
+        self.return_type.as_ref()
+    }
+
+    pub fn ffi_func(&self) -> &FFIFunction {
+        &self.ffi_func
+    }
+
+    pub fn throws(&self) -> bool {
+        self.attributes.get_throws_err().is_some()
+    }
+
+    pub fn throws_name(&self) -> Option<&str> {
+        self.attributes.get_throws_err()
+    }
+
+    pub fn throws_type(&self) -> Option<Type> {
+        self.attributes
+            .get_throws_err()
+            .map(|name| Type::Error(name.to_owned()))
+    }
+
+    pub fn derive_ffi_func(&mut self, ci_prefix: &str) -> Result<()> {
+        // The name is already set if the function is defined through a proc-macro invocation
+        // rather than in UDL. Don't overwrite it in that case.
+        if self.ffi_func.name.is_empty() {
+            self.ffi_func.name = format!("{ci_prefix}_{}", self.name);
+        }
+
+        self.ffi_func.arguments = self.arguments.iter().map(|arg| arg.into()).collect();
+        self.ffi_func.return_type = self.return_type.as_ref().map(|rt| rt.into());
+        Ok(())
+    }
+}
+
+impl From<uniffi_meta::FnParamMetadata> for Argument {
+    fn from(meta: uniffi_meta::FnParamMetadata) -> Self {
+        Argument {
+            name: meta.name,
+            type_: convert_type(&meta.ty),
+            by_ref: false,
+            optional: false,
+            default: None,
+        }
+    }
+}
+
+impl From<uniffi_meta::FnMetadata> for Function {
+    fn from(meta: uniffi_meta::FnMetadata) -> Self {
+        let ffi_name = meta.ffi_symbol_name();
+
+        let return_type = meta.return_type.map(|out| convert_type(&out));
+        let arguments = meta.inputs.into_iter().map(Into::into).collect();
+
+        let ffi_func = FFIFunction {
+            name: ffi_name,
+            ..FFIFunction::default()
+        };
+
+        Self {
+            name: meta.name,
+            arguments,
+            return_type,
+            ffi_func,
+            attributes: Default::default(),
+        }
+    }
+}
+
+impl APIConverter<Function> for weedle::namespace::NamespaceMember<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Function> {
+        match self {
+            weedle::namespace::NamespaceMember::Operation(f) => f.convert(ci),
+            _ => bail!("no support for namespace member type {:?} yet", self),
+        }
+    }
+}
+
+impl APIConverter<Function> for weedle::namespace::OperationNamespaceMember<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Function> {
+        let return_type = ci.resolve_return_type_expression(&self.return_type)?;
+        Ok(Function {
+            name: match self.identifier {
+                None => bail!("anonymous functions are not supported {:?}", self),
+                Some(id) => id.0.to_string(),
+            },
+            return_type,
+            arguments: self.args.body.list.convert(ci)?,
+            ffi_func: Default::default(),
+            attributes: FunctionAttributes::try_from(self.attributes.as_ref())?,
+        })
+    }
+}
+
+/// Represents an argument to a function/constructor/method call.
+///
+/// Each argument has a name and a type, along with some optional metadata.
+#[derive(Debug, Clone, Checksum)]
+pub struct Argument {
+    pub(super) name: String,
+    pub(super) type_: Type,
+    pub(super) by_ref: bool,
+    pub(super) optional: bool,
+    pub(super) default: Option<Literal>,
+}
+
+impl Argument {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn type_(&self) -> &Type {
+        &self.type_
+    }
+
+    pub fn by_ref(&self) -> bool {
+        self.by_ref
+    }
+
+    pub fn default_value(&self) -> Option<&Literal> {
+        self.default.as_ref()
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        self.type_.iter_types()
+    }
+}
+
+impl From<&Argument> for FFIArgument {
+    fn from(a: &Argument) -> FFIArgument {
+        FFIArgument {
+            name: a.name.clone(),
+            type_: (&a.type_).into(),
+        }
+    }
+}
+
+impl APIConverter<Argument> for weedle::argument::Argument<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Argument> {
+        match self {
+            weedle::argument::Argument::Single(t) => t.convert(ci),
+            weedle::argument::Argument::Variadic(_) => bail!("variadic arguments not supported"),
+        }
+    }
+}
+
+impl APIConverter<Argument> for weedle::argument::SingleArgument<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Argument> {
+        let type_ = ci.resolve_type_expression(&self.type_)?;
+        let default = match self.default {
+            None => None,
+            Some(v) => Some(convert_default_value(&v.value, &type_)?),
+        };
+        let by_ref = ArgumentAttributes::try_from(self.attributes.as_ref())?.by_ref();
+        Ok(Argument {
+            name: self.identifier.0.to_string(),
+            type_,
+            by_ref,
+            optional: self.optional.is_some(),
+            default,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_minimal_and_rich_function() -> Result<()> {
+        let ci = ComponentInterface::from_webidl(
+            r##"
+            namespace test {
+                void minimal();
+                [Throws=TestError]
+                sequence<string?> rich(u32 arg1, TestDict arg2);
+            };
+            [Error]
+            enum TestError { "err" };
+            dictionary TestDict {
+                u32 field;
+            };
+        "##,
+        )?;
+
+        let func1 = ci.get_function_definition("minimal").unwrap();
+        assert_eq!(func1.name(), "minimal");
+        assert!(func1.return_type().is_none());
+        assert!(func1.throws_type().is_none());
+        assert_eq!(func1.arguments().len(), 0);
+
+        let func2 = ci.get_function_definition("rich").unwrap();
+        assert_eq!(func2.name(), "rich");
+        assert_eq!(
+            func2.return_type().unwrap().canonical_name(),
+            "SequenceOptionalstring"
+        );
+        assert!(matches!(func2.throws_type(), Some(Type::Error(s)) if s == "TestError"));
+        assert_eq!(func2.arguments().len(), 2);
+        assert_eq!(func2.arguments()[0].name(), "arg1");
+        assert_eq!(func2.arguments()[0].type_().canonical_name(), "u32");
+        assert_eq!(func2.arguments()[1].name(), "arg2");
+        assert_eq!(
+            func2.arguments()[1].type_().canonical_name(),
+            "TypeTestDict"
+        );
+        Ok(())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/literal.rs b/third_party/rust/uniffi_bindgen/src/interface/literal.rs
new file mode 100644
index 0000000000..976b3bda9c
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/literal.rs
@@ -0,0 +1,186 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Support for literal values.
+//!
+//! This module provides support for interpreting literal values from the UDL,
+//! which appear in places such as default arguments.
+
+use anyhow::{bail, Result};
+use uniffi_meta::Checksum;
+
+use super::types::Type;
+
+// Represents a literal value.
+// Used for e.g. default argument values.
+#[derive(Debug, Clone, Checksum)]
+pub enum Literal {
+    Boolean(bool),
+    String(String),
+    // Integers are represented as the widest representation we can.
+    // Number formatting vary with language and radix, so we avoid a lot of parsing and
+    // formatting duplication by using only signed and unsigned variants.
+    UInt(u64, Radix, Type),
+    Int(i64, Radix, Type),
+    // Pass the string representation through as typed in the UDL.
+    // This avoids a lot of uncertainty around precision and accuracy,
+    // though bindings for languages less sophisticated number parsing than WebIDL
+    // will have to do extra work.
+    Float(String, Type),
+    Enum(String, Type),
+    EmptySequence,
+    EmptyMap,
+    Null,
+}
+
+// Represent the radix of integer literal values.
+// We preserve the radix into the generated bindings for readability reasons.
+#[derive(Debug, Clone, Copy, Checksum)]
+pub enum Radix {
+    Decimal = 10,
+    Octal = 8,
+    Hexadecimal = 16,
+}
+
+pub(super) fn convert_default_value(
+    default_value: &weedle::literal::DefaultValue<'_>,
+    type_: &Type,
+) -> Result<Literal> {
+    fn convert_integer(literal: &weedle::literal::IntegerLit<'_>, type_: &Type) -> Result<Literal> {
+        let (string, radix) = match literal {
+            weedle::literal::IntegerLit::Dec(v) => (v.0, Radix::Decimal),
+            weedle::literal::IntegerLit::Hex(v) => (v.0, Radix::Hexadecimal),
+            weedle::literal::IntegerLit::Oct(v) => (v.0, Radix::Octal),
+        };
+        // This is the radix of the parsed number, passed to `from_str_radix`.
+        let src_radix = radix as u32;
+        // This radix tells the backends how to represent the number in the output languages.
+        let dest_radix = if string == "0" || string.starts_with('-') {
+            // 1. weedle parses "0" as an octal literal, but we most likely want to treat this as a decimal.
+            // 2. Explicitly negatively signed hex numbers won't convert via i64 very well if they're not 64 bit.
+            //    For ease of implementation, output will use decimal.
+            Radix::Decimal
+        } else {
+            radix
+        };
+
+        // Clippy seems to think we should be using `strip_prefix` here, but
+        // it seems confused as to what this is actually doing.
+        #[allow(clippy::manual_strip)]
+        let string = if string.starts_with('-') {
+            ("-".to_string() + string[1..].trim_start_matches("0x")).to_lowercase()
+        } else {
+            string.trim_start_matches("0x").to_lowercase()
+        };
+
+        Ok(match type_ {
+            Type::Int8 | Type::Int16 | Type::Int32 | Type::Int64 => Literal::Int(
+                i64::from_str_radix(&string, src_radix)?,
+                dest_radix,
+                type_.clone(),
+            ),
+            Type::UInt8 | Type::UInt16 | Type::UInt32 | Type::UInt64 => Literal::UInt(
+                u64::from_str_radix(&string, src_radix)?,
+                dest_radix,
+                type_.clone(),
+            ),
+
+            _ => bail!("Cannot coerce literal {} into a non-integer type", string),
+        })
+    }
+
+    fn convert_float(literal: &weedle::literal::FloatLit<'_>, type_: &Type) -> Result<Literal> {
+        let string = match literal {
+            weedle::literal::FloatLit::Value(v) => v.0,
+
+            _ => bail!("Infinity and NaN is not currently supported"),
+        };
+
+        Ok(match type_ {
+            Type::Float32 | Type::Float64 => Literal::Float(string.to_string(), type_.clone()),
+            _ => bail!("Cannot coerce literal {} into a non-float type", string),
+        })
+    }
+
+    Ok(match (default_value, type_) {
+        (weedle::literal::DefaultValue::Boolean(b), Type::Boolean) => Literal::Boolean(b.0),
+        (weedle::literal::DefaultValue::String(s), Type::String) => {
+            // Note that weedle doesn't parse escaped double quotes.
+            // Keeping backends using double quotes (possible for all to date)
+            // means we don't need to escape single quotes. But we haven't spent a lot of time
+            // trying to break default values with weird escapes and quotes.
+            Literal::String(s.0.to_string())
+        }
+        (weedle::literal::DefaultValue::EmptyArray(_), Type::Sequence(_)) => Literal::EmptySequence,
+        (weedle::literal::DefaultValue::String(s), Type::Enum(_)) => {
+            Literal::Enum(s.0.to_string(), type_.clone())
+        }
+        (weedle::literal::DefaultValue::Null(_), Type::Optional(_)) => Literal::Null,
+        (_, Type::Optional(inner_type)) => convert_default_value(default_value, inner_type)?,
+
+        // We'll ensure the type safety in the convert_* number methods.
+        (weedle::literal::DefaultValue::Integer(i), _) => convert_integer(i, type_)?,
+        (weedle::literal::DefaultValue::Float(i), _) => convert_float(i, type_)?,
+
+        _ => bail!("No support for {:?} literal yet", default_value),
+    })
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use weedle::Parse;
+
+    fn parse_and_convert(expr: &str, t: Type) -> Result<Literal> {
+        let (_, node) = weedle::literal::DefaultValue::parse(expr).unwrap();
+        convert_default_value(&node, &t)
+    }
+
+    #[test]
+    fn test_default_value_conversion() -> Result<()> {
+        assert!(matches!(
+            parse_and_convert("0", Type::UInt8)?,
+            Literal::UInt(0, Radix::Decimal, Type::UInt8)
+        ));
+        assert!(matches!(
+            parse_and_convert("-12", Type::Int32)?,
+            Literal::Int(-12, Radix::Decimal, Type::Int32)
+        ));
+        assert!(
+            matches!(parse_and_convert("3.14", Type::Float32)?, Literal::Float(v, Type::Float32) if v == "3.14")
+        );
+        assert!(matches!(
+            parse_and_convert("false", Type::Boolean)?,
+            Literal::Boolean(false)
+        ));
+        assert!(
+            matches!(parse_and_convert("\"TEST\"", Type::String)?, Literal::String(v) if v == "TEST")
+        );
+        assert!(
+            matches!(parse_and_convert("\"one\"", Type::Enum("E".into()))?, Literal::Enum(v, Type::Enum(e)) if v == "one" && e == "E")
+        );
+        assert!(matches!(
+            parse_and_convert("[]", Type::Sequence(Box::new(Type::String)))?,
+            Literal::EmptySequence
+        ));
+        assert!(matches!(
+            parse_and_convert("null", Type::Optional(Box::new(Type::String)))?,
+            Literal::Null
+        ));
+        Ok(())
+    }
+    #[test]
+    fn test_error_on_type_mismatch() {
+        assert_eq!(
+            parse_and_convert("0", Type::Boolean)
+                .unwrap_err()
+                .to_string(),
+            "Cannot coerce literal 0 into a non-integer type"
+        );
+        assert!(parse_and_convert("{}", Type::Boolean)
+            .unwrap_err()
+            .to_string()
+            .starts_with("No support for"));
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/mod.rs b/third_party/rust/uniffi_bindgen/src/interface/mod.rs
new file mode 100644
index 0000000000..e72c69a36b
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/mod.rs
@@ -0,0 +1,1108 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Component Interface Definition.
+//!
+//! This module provides an abstract representation of the interface provided by a UniFFI Rust Component,
+//! in high-level terms suitable for translation into target consumer languages such as Kotlin
+//! and Swift. It also provides facilities for parsing a WebIDL interface definition file into such a
+//! representation.
+//!
+//! The entrypoint to this crate is the `ComponentInterface` struct, which holds a complete definition
+//! of the interface provided by a component, in two parts:
+//!
+//!    * The high-level consumer API, in terms of objects and records and methods and so-on
+//!    * The low-level FFI contract through which the foreign language code can call into Rust.
+//!
+//! That's really the key concept of this crate so it's worth repeating: a `ComponentInterface` completely
+//! defines the shape and semantics of an interface between the Rust-based implementation of a component
+//! and its foreign language consumers, including details like:
+//!
+//!    * The names of all symbols in the compiled object file
+//!    * The type and arity of all exported functions
+//!    * The layout and conventions used for all arguments and return types
+//!
+//! If you have a dynamic library compiled from a Rust Component using this crate, and a foreign
+//! language binding generated from the same `ComponentInterface` using the same version of this
+//! module, then there should be no opportunities for them to disagree on how the two sides should
+//! interact.
+//!
+//! General and incomplete TODO list for this thing:
+//!
+//!   * It should prevent user error and the possibility of generating bad code by doing (at least)
+//!     the following checks:
+//!       * No duplicate names (types, methods, args, etc)
+//!       * No shadowing of builtin names, or names we use in code generation
+//!     We expect that if the user actually does one of these things, then they *should* get a compile
+//!     error when trying to build the component, because the codegen will be invalid. But we can't
+//!     guarantee that there's not some edge-case where it produces valid-but-incorrect code.
+//!
+//!   * There is a *lot* of cloning going on, in the spirit of "first make it work". There's probably
+//!     a good opportunity here for e.g. interned strings, but we're nowhere near the point were we need
+//!     that kind of optimization just yet.
+//!
+//!   * Error messages and general developer experience leave a lot to be desired.
+
+use std::{collections::HashSet, convert::TryFrom, iter};
+
+use anyhow::{bail, Result};
+
+pub mod types;
+pub use types::Type;
+use types::{TypeIterator, TypeUniverse};
+
+mod attributes;
+mod callbacks;
+pub use callbacks::CallbackInterface;
+mod enum_;
+pub use enum_::Enum;
+mod error;
+pub use error::Error;
+mod function;
+pub use function::{Argument, Function};
+mod literal;
+pub use literal::{Literal, Radix};
+mod namespace;
+pub use namespace::Namespace;
+mod object;
+pub use object::{Constructor, Method, Object};
+mod record;
+pub use record::{Field, Record};
+
+pub mod ffi;
+pub use ffi::{FFIArgument, FFIFunction, FFIType};
+use uniffi_meta::{Checksum, MethodMetadata, ObjectMetadata};
+
+/// The main public interface for this module, representing the complete details of an interface exposed
+/// by a rust component and the details of consuming it via an extern-C FFI layer.
+///
+#[derive(Debug, Default, Checksum)]
+pub struct ComponentInterface {
+    /// Every ComponentInterface gets tagged with the version of uniffi used to create it.
+    /// This helps us avoid using a lib compiled with one version together with bindings created
+    /// using a different version, which might introduce unsafety.
+    uniffi_version: String,
+    /// All of the types used in the interface.
+    // We can't checksum `self.types`, but its contents are implied by the other fields
+    // anyway, so it's safe to ignore it.
+    #[checksum_ignore]
+    pub(super) types: TypeUniverse,
+    /// The unique prefix that we'll use for namespacing when exposing this component's API.
+    namespace: String,
+    /// The internal unique prefix used to namespace FFI symbols
+    #[checksum_ignore]
+    ffi_namespace: String,
+    /// The high-level API provided by the component.
+    enums: Vec<Enum>,
+    records: Vec<Record>,
+    functions: Vec<Function>,
+    objects: Vec<Object>,
+    callback_interfaces: Vec<CallbackInterface>,
+    errors: Vec<Error>,
+}
+
+impl ComponentInterface {
+    /// Parse a `ComponentInterface` from a string containing a WebIDL definition.
+    pub fn from_webidl(idl: &str) -> Result<Self> {
+        let mut ci = Self {
+            uniffi_version: "0.21.0".to_string(),
+            ..Default::default()
+        };
+        // There's some lifetime thing with the errors returned from weedle::Definitions::parse
+        // that my own lifetime is too short to worry about figuring out; unwrap and move on.
+
+        // Note we use `weedle::Definitions::parse` instead of `weedle::parse` so
+        // on parse errors we can see how far weedle got, which helps locate the problem.
+        use weedle::Parse; // this trait must be in scope for parse to work.
+        let (remaining, defns) = weedle::Definitions::parse(idl.trim()).unwrap();
+        if !remaining.is_empty() {
+            println!("Error parsing the IDL. Text remaining to be parsed is:");
+            println!("{remaining}");
+            bail!("parse error");
+        }
+        // Unconditionally add the String type, which is used by the panic handling
+        ci.types.add_known_type(&Type::String);
+        // We process the WebIDL definitions in two passes.
+        // First, go through and look for all the named types.
+        ci.types.add_type_definitions_from(defns.as_slice())?;
+        // With those names resolved, we can build a complete representation of the API.
+        APIBuilder::process(&defns, &mut ci)?;
+
+        // The FFI namespace must not be computed on the fly because it could otherwise be
+        // influenced by things added later from proc-macro metadata. Those have their own
+        // namespacing mechanism.
+        assert!(!ci.namespace.is_empty());
+        ci.ffi_namespace = format!("{}_{:x}", ci.namespace, ci.checksum());
+
+        // The following two methods will be called later anyways, but we call them here because
+        // it's convenient for UDL-only tests.
+        ci.check_consistency()?;
+        // Now that the high-level API is settled, we can derive the low-level FFI.
+        ci.derive_ffi_funcs()?;
+
+        Ok(ci)
+    }
+
+    /// The string namespace within which this API should be presented to the caller.
+    ///
+    /// This string would typically be used to prefix function names in the FFI, to build
+    /// a package or module name for the foreign language, etc.
+    pub fn namespace(&self) -> &str {
+        self.namespace.as_str()
+    }
+
+    /// Get the definitions for every Enum type in the interface.
+    pub fn enum_definitions(&self) -> &[Enum] {
+        &self.enums
+    }
+
+    /// Get an Enum definition by name, or None if no such Enum is defined.
+    pub fn get_enum_definition(&self, name: &str) -> Option<&Enum> {
+        // TODO: probably we could store these internally in a HashMap to make this easier?
+        self.enums.iter().find(|e| e.name == name)
+    }
+
+    /// Get the definitions for every Record type in the interface.
+    pub fn record_definitions(&self) -> &[Record] {
+        &self.records
+    }
+
+    /// Get a Record definition by name, or None if no such Record is defined.
+    pub fn get_record_definition(&self, name: &str) -> Option<&Record> {
+        // TODO: probably we could store these internally in a HashMap to make this easier?
+        self.records.iter().find(|r| r.name == name)
+    }
+
+    /// Get the definitions for every Function in the interface.
+    pub fn function_definitions(&self) -> &[Function] {
+        &self.functions
+    }
+
+    /// Get a Function definition by name, or None if no such Function is defined.
+    pub fn get_function_definition(&self, name: &str) -> Option<&Function> {
+        // TODO: probably we could store these internally in a HashMap to make this easier?
+        self.functions.iter().find(|f| f.name == name)
+    }
+
+    /// Get the definitions for every Object type in the interface.
+    pub fn object_definitions(&self) -> &[Object] {
+        &self.objects
+    }
+
+    /// Get an Object definition by name, or None if no such Object is defined.
+    pub fn get_object_definition(&self, name: &str) -> Option<&Object> {
+        // TODO: probably we could store these internally in a HashMap to make this easier?
+        self.objects.iter().find(|o| o.name == name)
+    }
+
+    /// Get the definitions for every Callback Interface type in the interface.
+    pub fn callback_interface_definitions(&self) -> &[CallbackInterface] {
+        &self.callback_interfaces
+    }
+
+    /// Get a Callback interface definition by name, or None if no such interface is defined.
+    pub fn get_callback_interface_definition(&self, name: &str) -> Option<&CallbackInterface> {
+        // TODO: probably we could store these internally in a HashMap to make this easier?
+        self.callback_interfaces.iter().find(|o| o.name == name)
+    }
+
+    /// Get the definitions for every Error type in the interface.
+    pub fn error_definitions(&self) -> &[Error] {
+        &self.errors
+    }
+
+    /// Get an Error definition by name, or None if no such Error is defined.
+    pub fn get_error_definition(&self, name: &str) -> Option<&Error> {
+        // TODO: probably we could store these internally in a HashMap to make this easier?
+        self.errors.iter().find(|e| e.name == name)
+    }
+
+    /// Should we generate read (and lift) functions for errors?
+    ///
+    /// This is a workaround for the fact that lower/write can't be generated for some errors,
+    /// specifically errors that are defined as flat in the UDL, but actually have fields in the
+    /// Rust source.
+    pub fn should_generate_error_read(&self, error: &Error) -> bool {
+        // We can and should always generate read() methods for fielded errors
+        let fielded = !error.is_flat();
+        // For flat errors, we should only generate read() methods if we need them to support
+        // callback interface errors
+        let used_in_callback_interface = self
+            .callback_interface_definitions()
+            .iter()
+            .flat_map(|cb| cb.methods())
+            .any(|m| m.throws_type() == Some(error.type_()));
+
+        fielded || used_in_callback_interface
+    }
+
+    /// Get details about all `Type::External` types
+    pub fn iter_external_types(&self) -> impl Iterator<Item = (&String, &String)> {
+        self.types.iter_known_types().filter_map(|t| match t {
+            Type::External { name, crate_name } => Some((name, crate_name)),
+            _ => None,
+        })
+    }
+
+    /// Get details about all `Type::Custom` types
+    pub fn iter_custom_types(&self) -> impl Iterator<Item = (&String, &Type)> {
+        self.types.iter_known_types().filter_map(|t| match t {
+            Type::Custom { name, builtin } => Some((name, &**builtin)),
+            _ => None,
+        })
+    }
+
+    /// Iterate over all known types in the interface.
+    pub fn iter_types(&self) -> impl Iterator<Item = &Type> {
+        self.types.iter_known_types()
+    }
+
+    /// Get a specific type
+    pub fn get_type(&self, name: &str) -> Option<Type> {
+        self.types.get_type_definition(name)
+    }
+
+    /// Iterate over all types contained in the given item.
+    ///
+    /// This method uses `iter_types` to iterate over the types contained within the given type,
+    /// but additionally recurses into the definition of user-defined types like records and enums
+    /// to yield the types that *they* contain.
+    fn iter_types_in_item<'a>(&'a self, item: &'a Type) -> impl Iterator<Item = &'a Type> + 'a {
+        RecursiveTypeIterator::new(self, item)
+    }
+
+    /// Check whether the given item contains any (possibly nested) Type::Object references.
+    ///
+    /// This is important to know in language bindings that cannot integrate object types
+    /// tightly with the host GC, and hence need to perform manual destruction of objects.
+    pub fn item_contains_object_references(&self, item: &Type) -> bool {
+        self.iter_types_in_item(item)
+            .any(|t| matches!(t, Type::Object(_)))
+    }
+
+    /// Check whether the given item contains any (possibly nested) unsigned types
+    pub fn item_contains_unsigned_types(&self, item: &Type) -> bool {
+        self.iter_types_in_item(item)
+            .any(|t| matches!(t, Type::UInt8 | Type::UInt16 | Type::UInt32 | Type::UInt64))
+    }
+
+    /// Check whether the interface contains any optional types
+    pub fn contains_optional_types(&self) -> bool {
+        self.types
+            .iter_known_types()
+            .any(|t| matches!(t, Type::Optional(_)))
+    }
+
+    /// Check whether the interface contains any sequence types
+    pub fn contains_sequence_types(&self) -> bool {
+        self.types
+            .iter_known_types()
+            .any(|t| matches!(t, Type::Sequence(_)))
+    }
+
+    /// Check whether the interface contains any map types
+    pub fn contains_map_types(&self) -> bool {
+        self.types
+            .iter_known_types()
+            .any(|t| matches!(t, Type::Map(_, _)))
+    }
+
+    /// Calculate a numeric checksum for this ComponentInterface.
+    ///
+    /// The checksum can be used to guard against accidentally using foreign-language bindings
+    /// generated from one version of an interface with the compiled Rust code from a different
+    /// version of that interface. It offers the following properties:
+    ///
+    ///   - Two ComponentIntefaces generated from the same WebIDL file, using the same version of uniffi
+    ///     and the same version of Rust, will always have the same checksum value.
+    ///   - Two ComponentInterfaces will, with high probability, have different checksum values if:
+    ///         - They were generated from two different WebIDL files.
+    ///         - They were generated by two different versions of uniffi
+    ///
+    /// Note that this is designed to prevent accidents, not attacks, so there is no need for the
+    /// checksum to be cryptographically secure.
+    pub fn checksum(&self) -> u16 {
+        uniffi_meta::checksum(self)
+    }
+
+    /// The namespace to use in FFI-level function definitions.
+    ///
+    /// The value returned by this method is used as a prefix to namespace all UDL-defined FFI
+    /// functions used in this ComponentInterface.
+    ///
+    /// Since these names are an internal implementation detail that is not typically visible to
+    /// consumers, we take the opportunity to add an additional safety guard by including a 4-hex-char
+    /// checksum in each name. If foreign-language bindings attempt to load and use a version of the
+    /// Rust code compiled from a different UDL definition than the one used for the bindings themselves,
+    /// then there is a high probability of checksum mismatch and they will fail to link against the
+    /// compiled Rust code. The result will be an ugly inscrutable link-time error, but that is a lot
+    /// better than triggering potentially arbitrary memory unsafety!
+    pub fn ffi_namespace(&self) -> &str {
+        assert!(!self.ffi_namespace.is_empty());
+        &self.ffi_namespace
+    }
+
+    /// Builtin FFI function for allocating a new `RustBuffer`.
+    /// This is needed so that the foreign language bindings can create buffers in which to pass
+    /// complex data types across the FFI.
+    pub fn ffi_rustbuffer_alloc(&self) -> FFIFunction {
+        FFIFunction {
+            name: format!("ffi_{}_rustbuffer_alloc", self.ffi_namespace()),
+            arguments: vec![FFIArgument {
+                name: "size".to_string(),
+                type_: FFIType::Int32,
+            }],
+            return_type: Some(FFIType::RustBuffer),
+        }
+    }
+
+    /// Builtin FFI function for copying foreign-owned bytes
+    /// This is needed so that the foreign language bindings can create buffers in which to pass
+    /// complex data types across the FFI.
+    pub fn ffi_rustbuffer_from_bytes(&self) -> FFIFunction {
+        FFIFunction {
+            name: format!("ffi_{}_rustbuffer_from_bytes", self.ffi_namespace()),
+            arguments: vec![FFIArgument {
+                name: "bytes".to_string(),
+                type_: FFIType::ForeignBytes,
+            }],
+            return_type: Some(FFIType::RustBuffer),
+        }
+    }
+
+    /// Builtin FFI function for freeing a `RustBuffer`.
+    /// This is needed so that the foreign language bindings can free buffers in which they received
+    /// complex data types returned across the FFI.
+    pub fn ffi_rustbuffer_free(&self) -> FFIFunction {
+        FFIFunction {
+            name: format!("ffi_{}_rustbuffer_free", self.ffi_namespace()),
+            arguments: vec![FFIArgument {
+                name: "buf".to_string(),
+                type_: FFIType::RustBuffer,
+            }],
+            return_type: None,
+        }
+    }
+
+    /// Builtin FFI function for reserving extra space in a `RustBuffer`.
+    /// This is needed so that the foreign language bindings can grow buffers used for passing
+    /// complex data types across the FFI.
+    pub fn ffi_rustbuffer_reserve(&self) -> FFIFunction {
+        FFIFunction {
+            name: format!("ffi_{}_rustbuffer_reserve", self.ffi_namespace()),
+            arguments: vec![
+                FFIArgument {
+                    name: "buf".to_string(),
+                    type_: FFIType::RustBuffer,
+                },
+                FFIArgument {
+                    name: "additional".to_string(),
+                    type_: FFIType::Int32,
+                },
+            ],
+            return_type: Some(FFIType::RustBuffer),
+        }
+    }
+
+    /// List the definitions of all FFI functions in the interface.
+    ///
+    /// The set of FFI functions is derived automatically from the set of higher-level types
+    /// along with the builtin FFI helper functions.
+    pub fn iter_ffi_function_definitions(&self) -> impl Iterator<Item = FFIFunction> + '_ {
+        self.iter_user_ffi_function_definitions()
+            .cloned()
+            .chain(self.iter_rust_buffer_ffi_function_definitions())
+    }
+
+    /// List all FFI functions definitions for user-defined interfaces
+    ///
+    /// This includes FFI functions for:
+    ///   - Top-level functions
+    ///   - Object methods
+    ///   - Callback interfaces
+    pub fn iter_user_ffi_function_definitions(&self) -> impl Iterator<Item = &FFIFunction> + '_ {
+        iter::empty()
+            .chain(
+                self.objects
+                    .iter()
+                    .flat_map(|obj| obj.iter_ffi_function_definitions()),
+            )
+            .chain(
+                self.callback_interfaces
+                    .iter()
+                    .map(|cb| cb.ffi_init_callback()),
+            )
+            .chain(self.functions.iter().map(|f| &f.ffi_func))
+    }
+
+    /// List all FFI functions definitions for RustBuffer functionality
+    pub fn iter_rust_buffer_ffi_function_definitions(&self) -> impl Iterator<Item = FFIFunction> {
+        [
+            self.ffi_rustbuffer_alloc(),
+            self.ffi_rustbuffer_from_bytes(),
+            self.ffi_rustbuffer_free(),
+            self.ffi_rustbuffer_reserve(),
+        ]
+        .into_iter()
+    }
+
+    //
+    // Private methods for building a ComponentInterface.
+    //
+
+    /// Resolve a weedle type expression into a `Type`.
+    ///
+    /// This method uses the current state of our `TypeUniverse` to turn a weedle type expression
+    /// into a concrete `Type` (or error if the type expression is not well defined). It abstracts
+    /// away the complexity of walking weedle's type struct heirarchy by dispatching to the `TypeResolver`
+    /// trait.
+    fn resolve_type_expression<T: types::TypeResolver>(&mut self, expr: T) -> Result<Type> {
+        self.types.resolve_type_expression(expr)
+    }
+
+    /// Resolve a weedle `ReturnType` expression into an optional `Type`.
+    ///
+    /// This method is similar to `resolve_type_expression`, but tailored specifically for return types.
+    /// It can return `None` to represent a non-existent return value.
+    fn resolve_return_type_expression(
+        &mut self,
+        expr: &weedle::types::ReturnType<'_>,
+    ) -> Result<Option<Type>> {
+        Ok(match expr {
+            weedle::types::ReturnType::Undefined(_) => None,
+            weedle::types::ReturnType::Type(t) => {
+                // Older versions of WebIDL used `void` for functions that don't return a value,
+                // while newer versions have replaced it with `undefined`. Special-case this for
+                // backwards compatibility for our consumers.
+                use weedle::types::{NonAnyType::Identifier, SingleType::NonAny, Type::Single};
+                match t {
+                    Single(NonAny(Identifier(id))) if id.type_.0 == "void" => None,
+                    _ => Some(self.resolve_type_expression(t)?),
+                }
+            }
+        })
+    }
+
+    /// Called by `APIBuilder` impls to add a newly-parsed namespace definition to the `ComponentInterface`.
+    fn add_namespace_definition(&mut self, defn: Namespace) -> Result<()> {
+        if !self.namespace.is_empty() {
+            bail!("duplicate namespace definition");
+        }
+        self.namespace = defn.name;
+        Ok(())
+    }
+
+    /// Called by `APIBuilder` impls to add a newly-parsed enum definition to the `ComponentInterface`.
+    fn add_enum_definition(&mut self, defn: Enum) {
+        // Note that there will be no duplicates thanks to the previous type-finding pass.
+        self.enums.push(defn);
+    }
+
+    /// Called by `APIBuilder` impls to add a newly-parsed record definition to the `ComponentInterface`.
+    pub(super) fn add_record_definition(&mut self, defn: Record) {
+        // Note that there will be no duplicates thanks to the previous type-finding pass.
+        self.records.push(defn);
+    }
+
+    /// Called by `APIBuilder` impls to add a newly-parsed function definition to the `ComponentInterface`.
+    pub(super) fn add_function_definition(&mut self, defn: Function) -> Result<()> {
+        for arg in &defn.arguments {
+            self.types.add_known_type(&arg.type_);
+        }
+        if let Some(ty) = &defn.return_type {
+            self.types.add_known_type(ty);
+        }
+
+        // Since functions are not a first-class type, we have to check for duplicates here
+        // rather than relying on the type-finding pass to catch them.
+        if self.functions.iter().any(|f| f.name == defn.name) {
+            bail!("duplicate function definition: \"{}\"", defn.name);
+        }
+        if !matches!(self.types.get_type_definition(defn.name()), None) {
+            bail!("Conflicting type definition for \"{}\"", defn.name());
+        }
+        self.functions.push(defn);
+        Ok(())
+    }
+
+    pub(super) fn add_method_definition(&mut self, meta: MethodMetadata) {
+        let object = get_or_insert_object(&mut self.objects, &meta.self_name);
+
+        let defn: Method = meta.into();
+        for arg in &defn.arguments {
+            self.types.add_known_type(&arg.type_);
+        }
+        if let Some(ty) = &defn.return_type {
+            self.types.add_known_type(ty);
+        }
+        object.methods.push(defn);
+    }
+
+    pub(super) fn add_object_free_fn(&mut self, meta: ObjectMetadata) {
+        let object = get_or_insert_object(&mut self.objects, &meta.name);
+        object.ffi_func_free.name = meta.free_ffi_symbol_name();
+    }
+
+    /// Called by `APIBuilder` impls to add a newly-parsed object definition to the `ComponentInterface`.
+    fn add_object_definition(&mut self, defn: Object) {
+        // Note that there will be no duplicates thanks to the previous type-finding pass.
+        self.objects.push(defn);
+    }
+
+    /// Called by `APIBuilder` impls to add a newly-parsed callback interface definition to the `ComponentInterface`.
+    fn add_callback_interface_definition(&mut self, defn: CallbackInterface) {
+        // Note that there will be no duplicates thanks to the previous type-finding pass.
+        self.callback_interfaces.push(defn);
+    }
+
+    /// Called by `APIBuilder` impls to add a newly-parsed error definition to the `ComponentInterface`.
+    fn add_error_definition(&mut self, defn: Error) {
+        // Note that there will be no duplicates thanks to the previous type-finding pass.
+        self.errors.push(defn);
+    }
+
+    /// Resolve unresolved types within proc-macro function / method signatures.
+    pub fn resolve_types(&mut self) -> Result<()> {
+        fn handle_unresolved_in(
+            ty: &mut Type,
+            f: impl Fn(&str) -> Result<Type> + Clone,
+        ) -> Result<()> {
+            match ty {
+                Type::Unresolved { name } => {
+                    *ty = f(name)?;
+                }
+                Type::Optional(inner) => {
+                    handle_unresolved_in(inner, f)?;
+                }
+                Type::Sequence(inner) => {
+                    handle_unresolved_in(inner, f)?;
+                }
+                Type::Map(k, v) => {
+                    handle_unresolved_in(k, f.clone())?;
+                    handle_unresolved_in(v, f)?;
+                }
+                _ => {}
+            }
+
+            Ok(())
+        }
+
+        let fn_sig_types = self.functions.iter_mut().flat_map(|fun| {
+            fun.arguments
+                .iter_mut()
+                .map(|arg| &mut arg.type_)
+                .chain(&mut fun.return_type)
+        });
+        let method_sig_types = self.objects.iter_mut().flat_map(|obj| {
+            obj.methods.iter_mut().flat_map(|m| {
+                m.arguments
+                    .iter_mut()
+                    .map(|arg| &mut arg.type_)
+                    .chain(&mut m.return_type)
+            })
+        });
+
+        for ty in fn_sig_types.chain(method_sig_types) {
+            handle_unresolved_in(ty, |unresolved_ty_name| {
+                match self.types.get_type_definition(unresolved_ty_name) {
+                    Some(def) => {
+                        assert!(
+                            !matches!(&def, Type::Unresolved { .. }),
+                            "unresolved types must not be part of TypeUniverse"
+                        );
+                        Ok(def)
+                    }
+                    None => bail!("Failed to resolve type `{unresolved_ty_name}`"),
+                }
+            })?;
+        }
+
+        Ok(())
+    }
+
+    /// Perform global consistency checks on the declared interface.
+    ///
+    /// This method checks for consistency problems in the declared interface
+    /// as a whole, and which can only be detected after we've finished defining
+    /// the entire interface.
+    pub fn check_consistency(&self) -> Result<()> {
+        if self.namespace.is_empty() {
+            bail!("missing namespace definition");
+        }
+        // To keep codegen tractable, enum variant names must not shadow type names.
+        for e in &self.enums {
+            for variant in &e.variants {
+                if self.types.get_type_definition(variant.name()).is_some() {
+                    bail!(
+                        "Enum variant names must not shadow type names: \"{}\"",
+                        variant.name()
+                    )
+                }
+            }
+        }
+        Ok(())
+    }
+
+    /// Automatically derive the low-level FFI functions from the high-level types in the interface.
+    ///
+    /// This should only be called after the high-level types have been completed defined, otherwise
+    /// the resulting set will be missing some entries.
+    pub fn derive_ffi_funcs(&mut self) -> Result<()> {
+        let ci_prefix = self.ffi_namespace().to_owned();
+        for func in self.functions.iter_mut() {
+            func.derive_ffi_func(&ci_prefix)?;
+        }
+        for obj in self.objects.iter_mut() {
+            obj.derive_ffi_funcs(&ci_prefix)?;
+        }
+        for callback in self.callback_interfaces.iter_mut() {
+            callback.derive_ffi_funcs(&ci_prefix);
+        }
+        Ok(())
+    }
+}
+
+fn get_or_insert_object<'a>(objects: &'a mut Vec<Object>, name: &str) -> &'a mut Object {
+    // The find-based way of writing this currently runs into a borrow checker
+    // error, so we use position
+    match objects.iter_mut().position(|o| o.name == name) {
+        Some(idx) => &mut objects[idx],
+        None => {
+            objects.push(Object::new(name.to_owned()));
+            objects.last_mut().unwrap()
+        }
+    }
+}
+
+/// Stateful iterator for yielding all types contained in a given type.
+///
+/// This struct is the implementation of [`ComponentInterface::iter_types_in_item`] and should be
+/// considered an opaque implementation detail. It's a separate struct because I couldn't
+/// figure out a way to implement it using iterators and closures that would make the lifetimes
+/// work out correctly.
+///
+/// The idea here is that we want to yield all the types from `iter_types` on a given type, and
+/// additionally we want to recurse into the definition of any user-provided types like records,
+/// enums, etc so we can also yield the types contained therein.
+///
+/// To guard against infinite recursion, we maintain a list of previously-seen user-defined
+/// types, ensuring that we recurse into the definition of those types only once. To simplify
+/// the implementation, we maintain a queue of pending user-defined types that we have seen
+/// but not yet recursed into. (Ironically, the use of an explicit queue means our implementation
+/// is not actually recursive...)
+struct RecursiveTypeIterator<'a> {
+    /// The [`ComponentInterface`] from which this iterator was created.
+    ci: &'a ComponentInterface,
+    /// The currently-active iterator from which we're yielding.
+    current: TypeIterator<'a>,
+    /// A set of names of user-defined types that we have already seen.
+    seen: HashSet<&'a str>,
+    /// A queue of user-defined types that we need to recurse into.
+    pending: Vec<&'a Type>,
+}
+
+impl<'a> RecursiveTypeIterator<'a> {
+    /// Allocate a new `RecursiveTypeIterator` over the given item.
+    fn new(ci: &'a ComponentInterface, item: &'a Type) -> RecursiveTypeIterator<'a> {
+        RecursiveTypeIterator {
+            ci,
+            // We begin by iterating over the types from the item itself.
+            current: item.iter_types(),
+            seen: Default::default(),
+            pending: Default::default(),
+        }
+    }
+
+    /// Add a new type to the queue of pending types, if not previously seen.
+    fn add_pending_type(&mut self, type_: &'a Type) {
+        match type_ {
+            Type::Record(nm)
+            | Type::Enum(nm)
+            | Type::Error(nm)
+            | Type::Object(nm)
+            | Type::CallbackInterface(nm) => {
+                if !self.seen.contains(nm.as_str()) {
+                    self.pending.push(type_);
+                    self.seen.insert(nm.as_str());
+                }
+            }
+            _ => (),
+        }
+    }
+
+    /// Advance the iterator to recurse into the next pending type, if any.
+    ///
+    /// This method is called when the current iterator is empty, and it will select
+    /// the next pending type from the queue and start iterating over its contained types.
+    /// The return value will be the first item from the new iterator.
+    fn advance_to_next_type(&mut self) -> Option<&'a Type> {
+        if let Some(next_type) = self.pending.pop() {
+            // This is a little awkward because the various definition lookup methods return an `Option<T>`.
+            // In the unlikely event that one of them returns `None` then, rather than trying to advance
+            // to a non-existent type, we just leave the existing iterator in place and allow the recursive
+            // call to `next()` to try again with the next pending type.
+            let next_iter = match next_type {
+                Type::Record(nm) => self.ci.get_record_definition(nm).map(Record::iter_types),
+                Type::Enum(nm) => self.ci.get_enum_definition(nm).map(Enum::iter_types),
+                Type::Error(nm) => self.ci.get_error_definition(nm).map(Error::iter_types),
+                Type::Object(nm) => self.ci.get_object_definition(nm).map(Object::iter_types),
+                Type::CallbackInterface(nm) => self
+                    .ci
+                    .get_callback_interface_definition(nm)
+                    .map(CallbackInterface::iter_types),
+                _ => None,
+            };
+            if let Some(next_iter) = next_iter {
+                self.current = next_iter;
+            }
+            // Advance the new iterator to its first item. If the new iterator happens to be empty,
+            // this will recurse back in to `advance_to_next_type` until we find one that isn't.
+            self.next()
+        } else {
+            // We've completely finished the iteration over all pending types.
+            None
+        }
+    }
+}
+
+impl<'a> Iterator for RecursiveTypeIterator<'a> {
+    type Item = &'a Type;
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(type_) = self.current.next() {
+            self.add_pending_type(type_);
+            Some(type_)
+        } else {
+            self.advance_to_next_type()
+        }
+    }
+}
+
+/// Trait to help build a `ComponentInterface` from WedIDL syntax nodes.
+///
+/// This trait does structural matching on the various weedle AST nodes and
+/// uses them to build up the records, enums, objects etc in the provided
+/// `ComponentInterface`.
+trait APIBuilder {
+    fn process(&self, ci: &mut ComponentInterface) -> Result<()>;
+}
+
+/// Add to a `ComponentInterface` from a list of weedle definitions,
+/// by processing each in turn.
+impl<T: APIBuilder> APIBuilder for Vec<T> {
+    fn process(&self, ci: &mut ComponentInterface) -> Result<()> {
+        for item in self {
+            item.process(ci)?;
+        }
+        Ok(())
+    }
+}
+
+/// Add to a `ComponentInterface` from a weedle definition.
+/// This is conceptually the root of the parser, and dispatches to implementations
+/// for the various specific WebIDL types that we support.
+impl APIBuilder for weedle::Definition<'_> {
+    fn process(&self, ci: &mut ComponentInterface) -> Result<()> {
+        match self {
+            weedle::Definition::Namespace(d) => d.process(ci)?,
+            weedle::Definition::Enum(d) => {
+                // We check if the enum represents an error...
+                let attrs = attributes::EnumAttributes::try_from(d.attributes.as_ref())?;
+                if attrs.contains_error_attr() {
+                    let err = d.convert(ci)?;
+                    ci.add_error_definition(err);
+                } else {
+                    let e = d.convert(ci)?;
+                    ci.add_enum_definition(e);
+                }
+            }
+            weedle::Definition::Dictionary(d) => {
+                let rec = d.convert(ci)?;
+                ci.add_record_definition(rec);
+            }
+            weedle::Definition::Interface(d) => {
+                let attrs = attributes::InterfaceAttributes::try_from(d.attributes.as_ref())?;
+                if attrs.contains_enum_attr() {
+                    let e = d.convert(ci)?;
+                    ci.add_enum_definition(e);
+                } else if attrs.contains_error_attr() {
+                    let e = d.convert(ci)?;
+                    ci.add_error_definition(e);
+                } else {
+                    let obj = d.convert(ci)?;
+                    ci.add_object_definition(obj);
+                }
+            }
+            weedle::Definition::CallbackInterface(d) => {
+                let obj = d.convert(ci)?;
+                ci.add_callback_interface_definition(obj);
+            }
+            // everything needed for typedefs is done in finder.rs.
+            weedle::Definition::Typedef(_) => {}
+            _ => bail!("don't know how to deal with {:?}", self),
+        }
+        Ok(())
+    }
+}
+
+/// Trait to help convert WedIDL syntax nodes into `ComponentInterface` objects.
+///
+/// This trait does structural matching on the various weedle AST nodes and converts
+/// them into appropriate structs that we can use to build up the contents of a
+/// `ComponentInterface`. It is basically the `TryFrom` trait except that the conversion
+/// always happens in the context of a given `ComponentInterface`, which is used for
+/// resolving e.g. type definitions.
+///
+/// The difference between this trait and `APIBuilder` is that `APIConverter` treats the
+/// `ComponentInterface` as a read-only data source for resolving types, while `APIBuilder`
+/// actually mutates the `ComponentInterface` to add new definitions.
+trait APIConverter<T> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<T>;
+}
+
+/// Convert a list of weedle items into a list of `ComponentInterface` items,
+/// by doing a direct item-by-item mapping.
+impl<U, T: APIConverter<U>> APIConverter<Vec<U>> for Vec<T> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Vec<U>> {
+        self.iter().map(|v| v.convert(ci)).collect::<Result<_>>()
+    }
+}
+
+fn convert_type(s: &uniffi_meta::Type) -> Type {
+    use uniffi_meta::Type as Ty;
+
+    match s {
+        Ty::U8 => Type::UInt8,
+        Ty::U16 => Type::UInt16,
+        Ty::U32 => Type::UInt32,
+        Ty::U64 => Type::UInt64,
+        Ty::I8 => Type::Int8,
+        Ty::I16 => Type::Int16,
+        Ty::I32 => Type::Int32,
+        Ty::I64 => Type::Int64,
+        Ty::F32 => Type::Float32,
+        Ty::F64 => Type::Float64,
+        Ty::Bool => Type::Boolean,
+        Ty::String => Type::String,
+        Ty::Option { inner_type } => Type::Optional(convert_type(inner_type).into()),
+        Ty::Vec { inner_type } => Type::Sequence(convert_type(inner_type).into()),
+        Ty::HashMap {
+            key_type,
+            value_type,
+        } => Type::Map(
+            convert_type(key_type).into(),
+            convert_type(value_type).into(),
+        ),
+        Ty::ArcObject { object_name } => Type::Object(object_name.clone()),
+        Ty::Unresolved { name } => Type::Unresolved { name: name.clone() },
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    // Note that much of the functionality of `ComponentInterface` is tested via its interactions
+    // with specific member types, in the sub-modules defining those member types.
+
+    const UDL1: &str = r#"
+        namespace foobar{};
+        enum Test {
+            "test_me",
+        };
+    "#;
+
+    const UDL2: &str = r#"
+        namespace hello {
+            u64 world();
+        };
+        dictionary Test {
+            boolean me;
+        };
+    "#;
+
+    #[test]
+    fn test_checksum_always_matches_for_same_webidl() {
+        for udl in &[UDL1, UDL2] {
+            let ci1 = ComponentInterface::from_webidl(udl).unwrap();
+            let ci2 = ComponentInterface::from_webidl(udl).unwrap();
+            assert_eq!(ci1.checksum(), ci2.checksum());
+        }
+    }
+
+    #[test]
+    fn test_checksum_differs_for_different_webidl() {
+        // There is a small probability of this test spuriously failing due to hash collision.
+        // If it happens often enough to be a problem, probably this whole "checksum" thing
+        // is not working out as intended.
+        let ci1 = ComponentInterface::from_webidl(UDL1).unwrap();
+        let ci2 = ComponentInterface::from_webidl(UDL2).unwrap();
+        assert_ne!(ci1.checksum(), ci2.checksum());
+    }
+
+    #[test]
+    fn test_checksum_differs_for_different_uniffi_version() {
+        // There is a small probability of this test spuriously failing due to hash collision.
+        // If it happens often enough to be a problem, probably this whole "checksum" thing
+        // is not working out as intended.
+        for udl in &[UDL1, UDL2] {
+            let ci1 = ComponentInterface::from_webidl(udl).unwrap();
+            let mut ci2 = ComponentInterface::from_webidl(udl).unwrap();
+            ci2.uniffi_version = String::from("fake-version");
+            assert_ne!(ci1.checksum(), ci2.checksum());
+        }
+    }
+
+    #[test]
+    fn test_duplicate_type_names_are_an_error() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                constructor();
+            };
+            dictionary Testing {
+                u32 field;
+            };
+        "#;
+        let err = ComponentInterface::from_webidl(UDL).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Conflicting type definition for \"Testing\""
+        );
+
+        const UDL2: &str = r#"
+            namespace test{};
+            enum Testing {
+                "one", "two"
+            };
+            [Error]
+            enum Testing { "three", "four" };
+        "#;
+        let err = ComponentInterface::from_webidl(UDL2).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Conflicting type definition for \"Testing\""
+        );
+
+        const UDL3: &str = r#"
+            namespace test{
+                u32 Testing();
+            };
+            enum Testing {
+                "one", "two"
+            };
+        "#;
+        let err = ComponentInterface::from_webidl(UDL3).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Conflicting type definition for \"Testing\""
+        );
+    }
+
+    #[test]
+    fn test_enum_variant_names_dont_shadow_types() {
+        // There are some edge-cases during codegen where we don't know how to disambiguate
+        // between an enum variant reference and a top-level type reference, so we
+        // disallow it in order to give a more scrutable error to the consumer.
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                constructor();
+            };
+            [Enum]
+            interface HardToCodegenFor {
+                Testing();
+                OtherVariant(u32 field);
+            };
+        "#;
+        let err = ComponentInterface::from_webidl(UDL).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Enum variant names must not shadow type names: \"Testing\""
+        );
+    }
+
+    #[test]
+    fn test_contains_optional_types() {
+        let mut ci = ComponentInterface {
+            ..Default::default()
+        };
+
+        // check that `contains_optional_types` returns false when there is no Optional type in the interface
+        assert!(!ci.contains_optional_types());
+
+        // check that `contains_optional_types` returns true when there is an Optional type in the interface
+        assert!(ci
+            .types
+            .add_type_definition("TestOptional{}", Type::Optional(Box::new(Type::String)))
+            .is_ok());
+        assert!(ci.contains_optional_types());
+    }
+
+    #[test]
+    fn test_contains_sequence_types() {
+        let mut ci = ComponentInterface {
+            ..Default::default()
+        };
+
+        // check that `contains_sequence_types` returns false when there is no Sequence type in the interface
+        assert!(!ci.contains_sequence_types());
+
+        // check that `contains_sequence_types` returns true when there is a Sequence type in the interface
+        assert!(ci
+            .types
+            .add_type_definition("TestSequence{}", Type::Sequence(Box::new(Type::UInt64)))
+            .is_ok());
+        assert!(ci.contains_sequence_types());
+    }
+
+    #[test]
+    fn test_contains_map_types() {
+        let mut ci = ComponentInterface {
+            ..Default::default()
+        };
+
+        // check that `contains_map_types` returns false when there is no Map type in the interface
+        assert!(!ci.contains_map_types());
+
+        // check that `contains_map_types` returns true when there is a Map type in the interface
+        assert!(ci
+            .types
+            .add_type_definition(
+                "Map{}",
+                Type::Map(Box::new(Type::String), Box::new(Type::Boolean))
+            )
+            .is_ok());
+        assert!(ci.contains_map_types());
+    }
+
+    #[test]
+    fn test_no_infinite_recursion_when_walking_types() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                void tester(Testing foo);
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert!(!ci.item_contains_unsigned_types(&Type::Object("Testing".into())));
+    }
+
+    #[test]
+    fn test_correct_recursion_when_walking_types() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface TestObj {
+                void tester(TestRecord foo);
+            };
+            dictionary TestRecord {
+                NestedRecord bar;
+            };
+            dictionary NestedRecord {
+                u64 baz;
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert!(ci.item_contains_unsigned_types(&Type::Object("TestObj".into())));
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/namespace.rs b/third_party/rust/uniffi_bindgen/src/interface/namespace.rs
new file mode 100644
index 0000000000..4a57d0ff41
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/namespace.rs
@@ -0,0 +1,132 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Namespace definition for a `ComponentInterface`.
+//!
+//! This module converts a namespace definition from UDL into structures that
+//! can be added to a `ComponentInterface`.
+//!
+//! In WebIDL proper, each `namespace` declares a set of functions and attributes that
+//! are exposed as a global object of that name, and there can be any number of such
+//! namespace definitions.
+//!
+//! For our purposes with UDL, we expect just a single `namespace` declaration, which
+//! defines properties of the component as a whole (currently just the name). It also
+//! contains the functions that will be exposed as individual plain functions exported by
+//! the component, if any. So something like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! namespace example {
+//!   string hello();
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Declares a component named "example" with a single exported function named "hello":
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {
+//! #   string hello();
+//! # };
+//! # "##)?;
+//! assert_eq!(ci.namespace(), "example");
+//! assert_eq!(ci.get_function_definition("hello").unwrap().name(), "hello");
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! While this awkward-looking syntax:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! namespace example {};
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Declares a component named "example" with no exported functions:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # "##)?;
+//! assert_eq!(ci.namespace(), "example");
+//! assert_eq!(ci.function_definitions().len(), 0);
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Yeah, it's a bit of an awkward fit syntactically, but it's enough
+//! to get us up and running for a first version of this tool.
+
+use anyhow::{bail, Result};
+
+use super::{APIBuilder, APIConverter, ComponentInterface};
+
+/// A namespace is currently just a name, but might hold more metadata about
+/// the component in future.
+///
+#[derive(Debug, Clone, Hash)]
+pub struct Namespace {
+    pub(super) name: String,
+}
+
+impl APIBuilder for weedle::NamespaceDefinition<'_> {
+    fn process(&self, ci: &mut ComponentInterface) -> Result<()> {
+        if self.attributes.is_some() {
+            bail!("namespace attributes are not supported yet");
+        }
+        ci.add_namespace_definition(Namespace {
+            name: self.identifier.0.to_string(),
+        })?;
+        for func in self.members.body.convert(ci)? {
+            ci.add_function_definition(func)?;
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_empty_namespace() {
+        const UDL: &str = r#"
+            namespace foobar{};
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.namespace(), "foobar");
+    }
+
+    #[test]
+    fn test_namespace_with_functions() {
+        const UDL: &str = r#"
+            namespace foobar{
+                boolean hello();
+                void world();
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.namespace(), "foobar");
+        assert_eq!(ci.function_definitions().len(), 2);
+        assert!(ci.get_function_definition("hello").is_some());
+        assert!(ci.get_function_definition("world").is_some());
+        assert!(ci.get_function_definition("potato").is_none());
+    }
+
+    #[test]
+    fn test_rejects_duplicate_namespaces() {
+        const UDL: &str = r#"
+            namespace foobar{
+                boolean hello();
+                void world();
+            };
+            namespace something_else{};
+        "#;
+        let err = ComponentInterface::from_webidl(UDL).unwrap_err();
+        assert_eq!(err.to_string(), "duplicate namespace definition");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/object.rs b/third_party/rust/uniffi_bindgen/src/interface/object.rs
new file mode 100644
index 0000000000..d6b26db0ec
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/object.rs
@@ -0,0 +1,602 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Object definitions for a `ComponentInterface`.
+//!
+//! This module converts "interface" definitions from UDL into [`Object`] structures
+//! that can be added to a `ComponentInterface`, which are the main way we define stateful
+//! objects with behaviour for a UniFFI Rust Component. An [`Object`] is an opaque handle
+//! to some state on which methods can be invoked.
+//!
+//! (The terminology mismatch between "interface" and "object" is a historical artifact of
+//! this tool prior to committing to WebIDL syntax).
+//!
+//! A declaration in the UDL like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! interface Example {
+//!   constructor(string? name);
+//!   string my_name();
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in an [`Object`] member with one [`Constructor`] and one [`Method`] being added
+//! to the resulting [`ComponentInterface`]:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # interface Example {
+//! #   constructor(string? name);
+//! #   string my_name();
+//! # };
+//! # "##)?;
+//! let obj = ci.get_object_definition("Example").unwrap();
+//! assert_eq!(obj.name(), "Example");
+//! assert_eq!(obj.constructors().len(), 1);
+//! assert_eq!(obj.constructors()[0].arguments()[0].name(), "name");
+//! assert_eq!(obj.methods().len(),1 );
+//! assert_eq!(obj.methods()[0].name(), "my_name");
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! It's not necessary for all interfaces to have constructors.
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # interface Example {};
+//! # "##)?;
+//! let obj = ci.get_object_definition("Example").unwrap();
+//! assert_eq!(obj.name(), "Example");
+//! assert_eq!(obj.constructors().len(), 0);
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+
+use std::convert::TryFrom;
+use std::{collections::HashSet, iter};
+
+use anyhow::{bail, Result};
+use uniffi_meta::Checksum;
+
+use super::ffi::{FFIArgument, FFIFunction, FFIType};
+use super::function::Argument;
+use super::types::{Type, TypeIterator};
+use super::{
+    attributes::{ConstructorAttributes, InterfaceAttributes, MethodAttributes},
+    convert_type,
+};
+use super::{APIConverter, ComponentInterface};
+
+/// An "object" is an opaque type that can be instantiated and passed around by reference,
+/// have methods called on it, and so on - basically your classic Object Oriented Programming
+/// type of deal, except without elaborate inheritence hierarchies.
+///
+/// In UDL these correspond to the `interface` keyword.
+///
+/// At the FFI layer, objects are represented by an opaque integer handle and a set of functions
+/// a common prefix. The object's constuctors are functions that return new objects by handle,
+/// and its methods are functions that take a handle as first argument. The foreign language
+/// binding code is expected to stitch these functions back together into an appropriate class
+/// definition (or that language's equivalent thereof).
+///
+/// TODO:
+///  - maybe "Class" would be a better name than "Object" here?
+#[derive(Debug, Clone, Checksum)]
+pub struct Object {
+    pub(super) name: String,
+    pub(super) constructors: Vec<Constructor>,
+    pub(super) methods: Vec<Method>,
+    // We don't include the FFIFunc in the hash calculation, because:
+    //  - it is entirely determined by the other fields,
+    //    so excluding it is safe.
+    //  - its `name` property includes a checksum derived from  the very
+    //    hash value we're trying to calculate here, so excluding it
+    //    avoids a weird circular depenendency in the calculation.
+    #[checksum_ignore]
+    pub(super) ffi_func_free: FFIFunction,
+    #[checksum_ignore]
+    pub(super) uses_deprecated_threadsafe_attribute: bool,
+}
+
+impl Object {
+    pub(super) fn new(name: String) -> Object {
+        Object {
+            name,
+            constructors: Default::default(),
+            methods: Default::default(),
+            ffi_func_free: Default::default(),
+            uses_deprecated_threadsafe_attribute: false,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn type_(&self) -> Type {
+        Type::Object(self.name.clone())
+    }
+
+    pub fn constructors(&self) -> Vec<&Constructor> {
+        self.constructors.iter().collect()
+    }
+
+    pub fn primary_constructor(&self) -> Option<&Constructor> {
+        self.constructors
+            .iter()
+            .find(|cons| cons.is_primary_constructor())
+    }
+
+    pub fn alternate_constructors(&self) -> Vec<&Constructor> {
+        self.constructors
+            .iter()
+            .filter(|cons| !cons.is_primary_constructor())
+            .collect()
+    }
+
+    pub fn methods(&self) -> Vec<&Method> {
+        self.methods.iter().collect()
+    }
+
+    pub fn get_method(&self, name: &str) -> Method {
+        let matches: Vec<_> = self.methods.iter().filter(|m| m.name() == name).collect();
+        match matches.len() {
+            1 => matches[0].clone(),
+            n => panic!("{n} methods named {name}"),
+        }
+    }
+
+    pub fn ffi_object_free(&self) -> &FFIFunction {
+        &self.ffi_func_free
+    }
+
+    pub fn uses_deprecated_threadsafe_attribute(&self) -> bool {
+        self.uses_deprecated_threadsafe_attribute
+    }
+
+    pub fn iter_ffi_function_definitions(&self) -> impl Iterator<Item = &FFIFunction> {
+        iter::once(&self.ffi_func_free)
+            .chain(self.constructors.iter().map(|f| &f.ffi_func))
+            .chain(self.methods.iter().map(|f| &f.ffi_func))
+    }
+
+    pub fn derive_ffi_funcs(&mut self, ci_prefix: &str) -> Result<()> {
+        // The name is already set if the function is defined through a proc-macro invocation
+        // rather than in UDL. Don't overwrite it in that case.
+        if self.ffi_func_free.name().is_empty() {
+            self.ffi_func_free.name = format!("ffi_{ci_prefix}_{}_object_free", self.name);
+        }
+        self.ffi_func_free.arguments = vec![FFIArgument {
+            name: "ptr".to_string(),
+            type_: FFIType::RustArcPtr(self.name().to_string()),
+        }];
+        self.ffi_func_free.return_type = None;
+
+        for cons in self.constructors.iter_mut() {
+            cons.derive_ffi_func(ci_prefix, &self.name);
+        }
+        for meth in self.methods.iter_mut() {
+            meth.derive_ffi_func(ci_prefix, &self.name)?;
+        }
+
+        Ok(())
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        Box::new(
+            self.methods
+                .iter()
+                .map(Method::iter_types)
+                .chain(self.constructors.iter().map(Constructor::iter_types))
+                .flatten(),
+        )
+    }
+}
+
+impl APIConverter<Object> for weedle::InterfaceDefinition<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Object> {
+        if self.inheritance.is_some() {
+            bail!("interface inheritence is not supported");
+        }
+        let mut object = Object::new(self.identifier.0.to_string());
+        let attributes = match &self.attributes {
+            Some(attrs) => InterfaceAttributes::try_from(attrs)?,
+            None => Default::default(),
+        };
+        object.uses_deprecated_threadsafe_attribute = attributes.threadsafe();
+        // Convert each member into a constructor or method, guarding against duplicate names.
+        let mut member_names = HashSet::new();
+        for member in &self.members.body {
+            match member {
+                weedle::interface::InterfaceMember::Constructor(t) => {
+                    let cons: Constructor = t.convert(ci)?;
+                    if !member_names.insert(cons.name.clone()) {
+                        bail!("Duplicate interface member name: \"{}\"", cons.name())
+                    }
+                    object.constructors.push(cons);
+                }
+                weedle::interface::InterfaceMember::Operation(t) => {
+                    let mut method: Method = t.convert(ci)?;
+                    if !member_names.insert(method.name.clone()) {
+                        bail!("Duplicate interface member name: \"{}\"", method.name())
+                    }
+                    method.object_name = object.name.clone();
+                    object.methods.push(method);
+                }
+                _ => bail!("no support for interface member type {:?} yet", member),
+            }
+        }
+        Ok(object)
+    }
+}
+
+// Represents a constructor for an object type.
+//
+// In the FFI, this will be a function that returns a pointer to an instance
+// of the corresponding object type.
+#[derive(Debug, Clone, Checksum)]
+pub struct Constructor {
+    pub(super) name: String,
+    pub(super) arguments: Vec<Argument>,
+    // We don't include the FFIFunc in the hash calculation, because:
+    //  - it is entirely determined by the other fields,
+    //    so excluding it is safe.
+    //  - its `name` property includes a checksum derived from  the very
+    //    hash value we're trying to calculate here, so excluding it
+    //    avoids a weird circular depenendency in the calculation.
+    #[checksum_ignore]
+    pub(super) ffi_func: FFIFunction,
+    pub(super) attributes: ConstructorAttributes,
+}
+
+impl Constructor {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn arguments(&self) -> Vec<&Argument> {
+        self.arguments.iter().collect()
+    }
+
+    pub fn full_arguments(&self) -> Vec<Argument> {
+        self.arguments.to_vec()
+    }
+
+    pub fn ffi_func(&self) -> &FFIFunction {
+        &self.ffi_func
+    }
+
+    pub fn throws(&self) -> bool {
+        self.attributes.get_throws_err().is_some()
+    }
+
+    pub fn throws_name(&self) -> Option<&str> {
+        self.attributes.get_throws_err()
+    }
+
+    pub fn throws_type(&self) -> Option<Type> {
+        self.attributes
+            .get_throws_err()
+            .map(|name| Type::Error(name.to_owned()))
+    }
+
+    pub fn is_primary_constructor(&self) -> bool {
+        self.name == "new"
+    }
+
+    fn derive_ffi_func(&mut self, ci_prefix: &str, obj_name: &str) {
+        self.ffi_func.name = format!("{ci_prefix}_{obj_name}_{}", self.name);
+        self.ffi_func.arguments = self.arguments.iter().map(Into::into).collect();
+        self.ffi_func.return_type = Some(FFIType::RustArcPtr(obj_name.to_string()));
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        Box::new(self.arguments.iter().flat_map(Argument::iter_types))
+    }
+}
+
+impl Default for Constructor {
+    fn default() -> Self {
+        Constructor {
+            name: String::from("new"),
+            arguments: Vec::new(),
+            ffi_func: Default::default(),
+            attributes: Default::default(),
+        }
+    }
+}
+
+impl APIConverter<Constructor> for weedle::interface::ConstructorInterfaceMember<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Constructor> {
+        let attributes = match &self.attributes {
+            Some(attr) => ConstructorAttributes::try_from(attr)?,
+            None => Default::default(),
+        };
+        Ok(Constructor {
+            name: String::from(attributes.get_name().unwrap_or("new")),
+            arguments: self.args.body.list.convert(ci)?,
+            ffi_func: Default::default(),
+            attributes,
+        })
+    }
+}
+
+// Represents an instance method for an object type.
+//
+// The FFI will represent this as a function whose first/self argument is a
+// `FFIType::RustArcPtr` to the instance.
+#[derive(Debug, Clone, Checksum)]
+pub struct Method {
+    pub(super) name: String,
+    pub(super) object_name: String,
+    pub(super) arguments: Vec<Argument>,
+    pub(super) return_type: Option<Type>,
+    // We don't include the FFIFunc in the hash calculation, because:
+    //  - it is entirely determined by the other fields,
+    //    so excluding it is safe.
+    //  - its `name` property includes a checksum derived from  the very
+    //    hash value we're trying to calculate here, so excluding it
+    //    avoids a weird circular depenendency in the calculation.
+    #[checksum_ignore]
+    pub(super) ffi_func: FFIFunction,
+    pub(super) attributes: MethodAttributes,
+}
+
+impl Method {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn arguments(&self) -> Vec<&Argument> {
+        self.arguments.iter().collect()
+    }
+
+    // Methods have a special implicit first argument for the object instance,
+    // hence `arguments` and `full_arguments` are different.
+    pub fn full_arguments(&self) -> Vec<Argument> {
+        vec![Argument {
+            name: "ptr".to_string(),
+            // TODO: ideally we'd get this via `ci.resolve_type_expression` so that it
+            // is contained in the proper `TypeUniverse`, but this works for now.
+            type_: Type::Object(self.object_name.clone()),
+            by_ref: !self.attributes.get_self_by_arc(),
+            optional: false,
+            default: None,
+        }]
+        .into_iter()
+        .chain(self.arguments.iter().cloned())
+        .collect()
+    }
+
+    pub fn return_type(&self) -> Option<&Type> {
+        self.return_type.as_ref()
+    }
+
+    pub fn ffi_func(&self) -> &FFIFunction {
+        &self.ffi_func
+    }
+
+    pub fn throws(&self) -> bool {
+        self.attributes.get_throws_err().is_some()
+    }
+
+    pub fn throws_name(&self) -> Option<&str> {
+        self.attributes.get_throws_err()
+    }
+
+    pub fn throws_type(&self) -> Option<Type> {
+        self.attributes
+            .get_throws_err()
+            .map(|name| Type::Error(name.to_owned()))
+    }
+
+    pub fn takes_self_by_arc(&self) -> bool {
+        self.attributes.get_self_by_arc()
+    }
+
+    pub fn derive_ffi_func(&mut self, ci_prefix: &str, obj_prefix: &str) -> Result<()> {
+        // The name is already set if the function is defined through a proc-macro invocation
+        // rather than in UDL. Don't overwrite it in that case.
+        if self.ffi_func.name.is_empty() {
+            self.ffi_func.name = format!("{ci_prefix}_{obj_prefix}_{}", self.name);
+        }
+
+        self.ffi_func.arguments = self.full_arguments().iter().map(Into::into).collect();
+        self.ffi_func.return_type = self.return_type.as_ref().map(Into::into);
+        Ok(())
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        Box::new(
+            self.arguments
+                .iter()
+                .flat_map(Argument::iter_types)
+                .chain(self.return_type.iter().flat_map(Type::iter_types)),
+        )
+    }
+}
+
+impl From<uniffi_meta::MethodMetadata> for Method {
+    fn from(meta: uniffi_meta::MethodMetadata) -> Self {
+        let ffi_name = meta.ffi_symbol_name();
+
+        let return_type = meta.return_type.map(|out| convert_type(&out));
+        let arguments = meta.inputs.into_iter().map(Into::into).collect();
+
+        let ffi_func = FFIFunction {
+            name: ffi_name,
+            ..FFIFunction::default()
+        };
+
+        Self {
+            name: meta.name,
+            object_name: meta.self_name,
+            arguments,
+            return_type,
+            ffi_func,
+            attributes: Default::default(),
+        }
+    }
+}
+
+impl APIConverter<Method> for weedle::interface::OperationInterfaceMember<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Method> {
+        if self.special.is_some() {
+            bail!("special operations not supported");
+        }
+        if self.modifier.is_some() {
+            bail!("method modifiers are not supported")
+        }
+        let return_type = ci.resolve_return_type_expression(&self.return_type)?;
+        Ok(Method {
+            name: match self.identifier {
+                None => bail!("anonymous methods are not supported {:?}", self),
+                Some(id) => {
+                    let name = id.0.to_string();
+                    if name == "new" {
+                        bail!("the method name \"new\" is reserved for the default constructor");
+                    }
+                    name
+                }
+            },
+            // We don't know the name of the containing `Object` at this point, fill it in later.
+            object_name: Default::default(),
+            arguments: self.args.body.list.convert(ci)?,
+            return_type,
+            ffi_func: Default::default(),
+            attributes: MethodAttributes::try_from(self.attributes.as_ref())?,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_that_all_argument_and_return_types_become_known() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                constructor(string? name, u16 age);
+                sequence<u32> code_points_of_name();
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.object_definitions().len(), 1);
+        ci.get_object_definition("Testing").unwrap();
+
+        assert_eq!(ci.iter_types().count(), 6);
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "u16"));
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "u32"));
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "Sequenceu32"));
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "string"));
+        assert!(ci
+            .iter_types()
+            .any(|t| t.canonical_name() == "Optionalstring"));
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "TypeTesting"));
+    }
+
+    #[test]
+    fn test_alternate_constructors() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                constructor();
+                [Name=new_with_u32]
+                constructor(u32 v);
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.object_definitions().len(), 1);
+
+        let obj = ci.get_object_definition("Testing").unwrap();
+        assert!(obj.primary_constructor().is_some());
+        assert_eq!(obj.alternate_constructors().len(), 1);
+        assert_eq!(obj.methods().len(), 0);
+
+        let cons = obj.primary_constructor().unwrap();
+        assert_eq!(cons.name(), "new");
+        assert_eq!(cons.arguments.len(), 0);
+        assert_eq!(cons.ffi_func.arguments.len(), 0);
+
+        let cons = obj.alternate_constructors()[0];
+        assert_eq!(cons.name(), "new_with_u32");
+        assert_eq!(cons.arguments.len(), 1);
+        assert_eq!(cons.ffi_func.arguments.len(), 1);
+    }
+
+    #[test]
+    fn test_the_name_new_identifies_the_primary_constructor() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                [Name=newish]
+                constructor();
+                [Name=new]
+                constructor(u32 v);
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.object_definitions().len(), 1);
+
+        let obj = ci.get_object_definition("Testing").unwrap();
+        assert!(obj.primary_constructor().is_some());
+        assert_eq!(obj.alternate_constructors().len(), 1);
+        assert_eq!(obj.methods().len(), 0);
+
+        let cons = obj.primary_constructor().unwrap();
+        assert_eq!(cons.name(), "new");
+        assert_eq!(cons.arguments.len(), 1);
+
+        let cons = obj.alternate_constructors()[0];
+        assert_eq!(cons.name(), "newish");
+        assert_eq!(cons.arguments.len(), 0);
+        assert_eq!(cons.ffi_func.arguments.len(), 0);
+    }
+
+    #[test]
+    fn test_the_name_new_is_reserved_for_constructors() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                constructor();
+                void new(u32 v);
+            };
+        "#;
+        let err = ComponentInterface::from_webidl(UDL).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "the method name \"new\" is reserved for the default constructor"
+        );
+    }
+
+    #[test]
+    fn test_duplicate_primary_constructors_not_allowed() {
+        const UDL: &str = r#"
+            namespace test{};
+            interface Testing {
+                constructor();
+                constructor(u32 v);
+            };
+        "#;
+        let err = ComponentInterface::from_webidl(UDL).unwrap_err();
+        assert_eq!(err.to_string(), "Duplicate interface member name: \"new\"");
+
+        const UDL2: &str = r#"
+            namespace test{};
+            interface Testing {
+                constructor();
+                [Name=new]
+                constructor(u32 v);
+            };
+        "#;
+        let err = ComponentInterface::from_webidl(UDL2).unwrap_err();
+        assert_eq!(err.to_string(), "Duplicate interface member name: \"new\"");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/record.rs b/third_party/rust/uniffi_bindgen/src/interface/record.rs
new file mode 100644
index 0000000000..dd6a48e2c6
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/record.rs
@@ -0,0 +1,250 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Record definitions for a `ComponentInterface`.
+//!
+//! This module converts "dictionary" definitions from UDL into [`Record`] structures
+//! that can be added to a `ComponentInterface`, which are the main way we define structured
+//! data types for a UniFFI Rust Component. A [`Record`] has a fixed set of named fields,
+//! each of a specific type.
+//!
+//! (The terminology mismatch between "dictionary" and "record" is a historical artifact
+//! due to this tool being loosely inspired by WebAssembly Interface Types, which used
+//! the term "record" for this sort of data).
+//!
+//! A declaration in the UDL like this:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! dictionary Example {
+//!   string name;
+//!   u32 value;
+//! };
+//! # "##)?;
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+//!
+//! Will result in a [`Record`] member with two [`Field`]s being added to the resulting
+//! [`ComponentInterface`]:
+//!
+//! ```
+//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
+//! # namespace example {};
+//! # dictionary Example {
+//! #   string name;
+//! #   u32 value;
+//! # };
+//! # "##)?;
+//! let record = ci.get_record_definition("Example").unwrap();
+//! assert_eq!(record.name(), "Example");
+//! assert_eq!(record.fields()[0].name(), "name");
+//! assert_eq!(record.fields()[1].name(), "value");
+//! # Ok::<(), anyhow::Error>(())
+//! ```
+
+use anyhow::{bail, Result};
+use uniffi_meta::Checksum;
+
+use super::types::{Type, TypeIterator};
+use super::{
+    convert_type,
+    literal::{convert_default_value, Literal},
+};
+use super::{APIConverter, ComponentInterface};
+
+/// Represents a "data class" style object, for passing around complex values.
+///
+/// In the FFI these are represented as a byte buffer, which one side explicitly
+/// serializes the data into and the other serializes it out of. So I guess they're
+/// kind of like "pass by clone" values.
+#[derive(Debug, Clone, Checksum)]
+pub struct Record {
+    pub(super) name: String,
+    pub(super) fields: Vec<Field>,
+}
+
+impl Record {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn type_(&self) -> Type {
+        // *sigh* at the clone here, the relationship between a ComponentInterace
+        // and its contained types could use a bit of a cleanup.
+        Type::Record(self.name.clone())
+    }
+
+    pub fn fields(&self) -> &[Field] {
+        &self.fields
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        Box::new(self.fields.iter().flat_map(Field::iter_types))
+    }
+}
+
+impl From<uniffi_meta::RecordMetadata> for Record {
+    fn from(meta: uniffi_meta::RecordMetadata) -> Self {
+        Self {
+            name: meta.name,
+            fields: meta.fields.into_iter().map(Into::into).collect(),
+        }
+    }
+}
+
+impl APIConverter<Record> for weedle::DictionaryDefinition<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Record> {
+        if self.attributes.is_some() {
+            bail!("dictionary attributes are not supported yet");
+        }
+        if self.inheritance.is_some() {
+            bail!("dictionary inheritence is not supported");
+        }
+        Ok(Record {
+            name: self.identifier.0.to_string(),
+            fields: self.members.body.convert(ci)?,
+        })
+    }
+}
+
+// Represents an individual field on a Record.
+#[derive(Debug, Clone, Checksum)]
+pub struct Field {
+    pub(super) name: String,
+    pub(super) type_: Type,
+    pub(super) required: bool,
+    pub(super) default: Option<Literal>,
+}
+
+impl Field {
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn type_(&self) -> &Type {
+        &self.type_
+    }
+
+    pub fn default_value(&self) -> Option<&Literal> {
+        self.default.as_ref()
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        self.type_.iter_types()
+    }
+}
+
+impl From<uniffi_meta::FieldMetadata> for Field {
+    fn from(meta: uniffi_meta::FieldMetadata) -> Self {
+        Self {
+            name: meta.name,
+            type_: convert_type(&meta.ty),
+            required: true,
+            default: None,
+        }
+    }
+}
+
+impl APIConverter<Field> for weedle::dictionary::DictionaryMember<'_> {
+    fn convert(&self, ci: &mut ComponentInterface) -> Result<Field> {
+        if self.attributes.is_some() {
+            bail!("dictionary member attributes are not supported yet");
+        }
+        let type_ = ci.resolve_type_expression(&self.type_)?;
+        let default = match self.default {
+            None => None,
+            Some(v) => Some(convert_default_value(&v.value, &type_)?),
+        };
+        Ok(Field {
+            name: self.identifier.0.to_string(),
+            type_,
+            required: self.required.is_some(),
+            default,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::super::literal::Radix;
+    use super::*;
+
+    #[test]
+    fn test_multiple_record_types() {
+        const UDL: &str = r#"
+            namespace test{};
+            dictionary Empty {};
+            dictionary Simple {
+                u32 field;
+            };
+            dictionary Complex {
+                string? key;
+                u32 value = 0;
+                required boolean spin;
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.record_definitions().len(), 3);
+
+        let record = ci.get_record_definition("Empty").unwrap();
+        assert_eq!(record.name(), "Empty");
+        assert_eq!(record.fields().len(), 0);
+
+        let record = ci.get_record_definition("Simple").unwrap();
+        assert_eq!(record.name(), "Simple");
+        assert_eq!(record.fields().len(), 1);
+        assert_eq!(record.fields()[0].name(), "field");
+        assert_eq!(record.fields()[0].type_().canonical_name(), "u32");
+        assert!(!record.fields()[0].required);
+        assert!(record.fields()[0].default_value().is_none());
+
+        let record = ci.get_record_definition("Complex").unwrap();
+        assert_eq!(record.name(), "Complex");
+        assert_eq!(record.fields().len(), 3);
+        assert_eq!(record.fields()[0].name(), "key");
+        assert_eq!(
+            record.fields()[0].type_().canonical_name(),
+            "Optionalstring"
+        );
+        assert!(!record.fields()[0].required);
+        assert!(record.fields()[0].default_value().is_none());
+        assert_eq!(record.fields()[1].name(), "value");
+        assert_eq!(record.fields()[1].type_().canonical_name(), "u32");
+        assert!(!record.fields()[1].required);
+        assert!(matches!(
+            record.fields()[1].default_value(),
+            Some(Literal::UInt(0, Radix::Decimal, Type::UInt32))
+        ));
+        assert_eq!(record.fields()[2].name(), "spin");
+        assert_eq!(record.fields()[2].type_().canonical_name(), "bool");
+        assert!(record.fields()[2].required);
+        assert!(record.fields()[2].default_value().is_none());
+    }
+
+    #[test]
+    fn test_that_all_field_types_become_known() {
+        const UDL: &str = r#"
+            namespace test{};
+            dictionary Testing {
+                string? maybe_name;
+                u32 value;
+            };
+        "#;
+        let ci = ComponentInterface::from_webidl(UDL).unwrap();
+        assert_eq!(ci.record_definitions().len(), 1);
+        let record = ci.get_record_definition("Testing").unwrap();
+        assert_eq!(record.fields().len(), 2);
+        assert_eq!(record.fields()[0].name(), "maybe_name");
+        assert_eq!(record.fields()[1].name(), "value");
+
+        assert_eq!(ci.iter_types().count(), 4);
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "u32"));
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "string"));
+        assert!(ci
+            .iter_types()
+            .any(|t| t.canonical_name() == "Optionalstring"));
+        assert!(ci.iter_types().any(|t| t.canonical_name() == "TypeTesting"));
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/types/finder.rs b/third_party/rust/uniffi_bindgen/src/interface/types/finder.rs
new file mode 100644
index 0000000000..c21f938d2f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/types/finder.rs
@@ -0,0 +1,244 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Helpers for finding the named types defined in a UDL interface.
+//!
+//! This module provides the [`TypeFinder`] trait, an abstraction for walking
+//! the weedle parse tree, looking for type definitions, and accumulating them
+//! in a [`TypeUniverse`].
+//!
+//! The type-finding process only discovers very basic information about names
+//! and their corresponding types. For example, it can discover that "Foobar"
+//! names a Record, but it won't discover anything about the fields of that
+//! record.
+//!
+//! Factoring this functionality out into a separate phase makes the subsequent
+//! work of more *detailed* parsing of the UDL a lot simpler, we know how to resolve
+//! names to types when building up the full interface definition.
+
+use std::convert::TryFrom;
+
+use anyhow::{bail, Result};
+
+use super::super::attributes::{EnumAttributes, InterfaceAttributes, TypedefAttributes};
+use super::{Type, TypeUniverse};
+
+/// Trait to help with an early "type discovery" phase when processing the UDL.
+///
+/// Ths trait does structural matching against weedle AST nodes from a parsed
+/// UDL file, looking for all the newly-defined types in the file and accumulating
+/// them in the given `TypeUniverse`.
+pub(in super::super) trait TypeFinder {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()>;
+}
+
+impl<T: TypeFinder> TypeFinder for &[T] {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()> {
+        for item in *self {
+            item.add_type_definitions_to(types)?;
+        }
+        Ok(())
+    }
+}
+
+impl TypeFinder for weedle::Definition<'_> {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()> {
+        match self {
+            weedle::Definition::Interface(d) => d.add_type_definitions_to(types),
+            weedle::Definition::Dictionary(d) => d.add_type_definitions_to(types),
+            weedle::Definition::Enum(d) => d.add_type_definitions_to(types),
+            weedle::Definition::Typedef(d) => d.add_type_definitions_to(types),
+            weedle::Definition::CallbackInterface(d) => d.add_type_definitions_to(types),
+            _ => Ok(()),
+        }
+    }
+}
+
+impl TypeFinder for weedle::InterfaceDefinition<'_> {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()> {
+        let name = self.identifier.0.to_string();
+        // Some enum types are defined using an `interface` with a special attribute.
+        if InterfaceAttributes::try_from(self.attributes.as_ref())?.contains_enum_attr() {
+            types.add_type_definition(self.identifier.0, Type::Enum(name))
+        } else if InterfaceAttributes::try_from(self.attributes.as_ref())?.contains_error_attr() {
+            types.add_type_definition(self.identifier.0, Type::Error(name))
+        } else {
+            types.add_type_definition(self.identifier.0, Type::Object(name))
+        }
+    }
+}
+
+impl TypeFinder for weedle::DictionaryDefinition<'_> {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()> {
+        let name = self.identifier.0.to_string();
+        types.add_type_definition(self.identifier.0, Type::Record(name))
+    }
+}
+
+impl TypeFinder for weedle::EnumDefinition<'_> {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()> {
+        let name = self.identifier.0.to_string();
+        // Our error types are defined using an `enum` with a special attribute.
+        if EnumAttributes::try_from(self.attributes.as_ref())?.contains_error_attr() {
+            types.add_type_definition(self.identifier.0, Type::Error(name))
+        } else {
+            types.add_type_definition(self.identifier.0, Type::Enum(name))
+        }
+    }
+}
+
+impl TypeFinder for weedle::TypedefDefinition<'_> {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()> {
+        let name = self.identifier.0;
+        let attrs = TypedefAttributes::try_from(self.attributes.as_ref())?;
+        // If we wanted simple `typedef`s, it would be as easy as:
+        // > let t = types.resolve_type_expression(&self.type_)?;
+        // > types.add_type_definition(name, t)
+        // But we don't - `typedef`s are reserved for external types.
+        if attrs.is_custom() {
+            // A local type which wraps a builtin and for which we will generate an
+            // `FfiConverter` implementation.
+            let builtin = types.resolve_type_expression(&self.type_)?;
+            types.add_type_definition(
+                name,
+                Type::Custom {
+                    name: name.to_string(),
+                    builtin: builtin.into(),
+                },
+            )
+        } else {
+            // A crate which can supply an `FfiConverter`.
+            // We don't reference `self._type`, so ideally we could insist on it being
+            // the literal 'extern' but that's tricky
+            types.add_type_definition(
+                name,
+                Type::External {
+                    name: name.to_string(),
+                    crate_name: attrs.get_crate_name(),
+                },
+            )
+        }
+    }
+}
+
+impl TypeFinder for weedle::CallbackInterfaceDefinition<'_> {
+    fn add_type_definitions_to(&self, types: &mut TypeUniverse) -> Result<()> {
+        if self.attributes.is_some() {
+            bail!("no typedef attributes are currently supported");
+        }
+        let name = self.identifier.0.to_string();
+        types.add_type_definition(self.identifier.0, Type::CallbackInterface(name))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    // A helper to take valid UDL and a closure to check what's in it.
+    fn test_a_finding<F>(udl: &str, tester: F)
+    where
+        F: FnOnce(TypeUniverse),
+    {
+        let idl = weedle::parse(udl).unwrap();
+        let mut types = TypeUniverse::default();
+        types.add_type_definitions_from(idl.as_ref()).unwrap();
+        tester(types);
+    }
+
+    #[test]
+    fn test_type_finding() {
+        test_a_finding(
+            r#"
+            callback interface TestCallbacks {
+                string hello(u32 count);
+            };
+        "#,
+            |types| {
+                assert!(
+                    matches!(types.get_type_definition("TestCallbacks").unwrap(), Type::CallbackInterface(nm) if nm == "TestCallbacks")
+                );
+            },
+        );
+
+        test_a_finding(
+            r#"
+            dictionary TestRecord {
+                u32 field;
+            };
+        "#,
+            |types| {
+                assert!(
+                    matches!(types.get_type_definition("TestRecord").unwrap(), Type::Record(nm) if nm == "TestRecord")
+                );
+            },
+        );
+
+        test_a_finding(
+            r#"
+            enum TestItems { "one", "two" };
+
+            [Error]
+            enum TestError { "ErrorOne", "ErrorTwo" };
+        "#,
+            |types| {
+                assert!(
+                    matches!(types.get_type_definition("TestItems").unwrap(), Type::Enum(nm) if nm == "TestItems")
+                );
+                assert!(
+                    matches!(types.get_type_definition("TestError").unwrap(), Type::Error(nm) if nm == "TestError")
+                );
+            },
+        );
+
+        test_a_finding(
+            r#"
+            interface TestObject {
+                constructor();
+            };
+        "#,
+            |types| {
+                assert!(
+                    matches!(types.get_type_definition("TestObject").unwrap(), Type::Object(nm) if nm == "TestObject")
+                );
+            },
+        );
+
+        test_a_finding(
+            r#"
+            [External="crate-name"]
+            typedef extern ExternalType;
+
+            [Custom]
+            typedef string CustomType;
+        "#,
+            |types| {
+                assert!(
+                    matches!(types.get_type_definition("ExternalType").unwrap(), Type::External { name, crate_name }
+                                                                                 if name == "ExternalType" && crate_name == "crate-name")
+                );
+                assert!(
+                    matches!(types.get_type_definition("CustomType").unwrap(), Type::Custom { name, builtin }
+                                                                                     if name == "CustomType" && builtin == Box::new(Type::String))
+                );
+            },
+        );
+    }
+
+    fn get_err(udl: &str) -> String {
+        let parsed = weedle::parse(udl).unwrap();
+        let mut types = TypeUniverse::default();
+        let err = types
+            .add_type_definitions_from(parsed.as_ref())
+            .unwrap_err();
+        err.to_string()
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_typedef_error_on_no_attr() {
+        // Sorry, still working out what we want for non-imported typedefs..
+        get_err("typedef string Custom;");
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/types/mod.rs b/third_party/rust/uniffi_bindgen/src/interface/types/mod.rs
new file mode 100644
index 0000000000..65426926f5
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/types/mod.rs
@@ -0,0 +1,320 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Basic typesystem for defining a component interface.
+//!
+//! This module provides the "API-level" typesystem of a UniFFI Rust Component, that is,
+//! the types provided by the Rust implementation and consumed callers of the foreign language
+//! bindings. Think "objects" and "enums" and "records".
+//!
+//! The [`Type`] enum represents high-level types that would appear in the public API of
+//! a component, such as enums and records as well as primitives like ints and strings.
+//! The Rust code that implements a component, and the foreign language bindings that consume it,
+//! will both typically deal with such types as their core concern.
+//!
+//! The set of all [`Type`]s used in a component interface is represented by a [`TypeUniverse`],
+//! which can be used by the bindings generator code to determine what type-related helper
+//! functions to emit for a given component.
+//!
+//! As a developer working on UniFFI itself, you're likely to spend a fair bit of time thinking
+//! about how these API-level types map into the lower-level types of the FFI layer as represented
+//! by the [`ffi::FFIType`](super::ffi::FFIType) enum, but that's a detail that is invisible to end users.
+
+use std::{collections::hash_map::Entry, collections::BTreeSet, collections::HashMap, iter};
+
+use anyhow::{bail, Result};
+use heck::ToUpperCamelCase;
+use uniffi_meta::Checksum;
+
+use super::ffi::FFIType;
+
+mod finder;
+pub(super) use finder::TypeFinder;
+mod resolver;
+pub(super) use resolver::{resolve_builtin_type, TypeResolver};
+
+/// Represents all the different high-level types that can be used in a component interface.
+/// At this level we identify user-defined types by name, without knowing any details
+/// of their internal structure apart from what type of thing they are (record, enum, etc).
+#[derive(Debug, Clone, Eq, PartialEq, Checksum, Ord, PartialOrd)]
+pub enum Type {
+    // Primitive types.
+    UInt8,
+    Int8,
+    UInt16,
+    Int16,
+    UInt32,
+    Int32,
+    UInt64,
+    Int64,
+    Float32,
+    Float64,
+    Boolean,
+    String,
+    Timestamp,
+    Duration,
+    // Types defined in the component API, each of which has a string name.
+    Object(String),
+    Record(String),
+    Enum(String),
+    Error(String),
+    CallbackInterface(String),
+    // Structurally recursive types.
+    Optional(Box<Type>),
+    Sequence(Box<Type>),
+    Map(Box<Type>, Box<Type>),
+    // An FfiConverter we `use` from an external crate
+    External { name: String, crate_name: String },
+    // Custom type on the scaffolding side
+    Custom { name: String, builtin: Box<Type> },
+    // An unresolved user-defined type inside a proc-macro exported function
+    // signature. Must be replaced by another type before bindings generation.
+    Unresolved { name: String },
+}
+
+impl Type {
+    /// Get the canonical, unique-within-this-component name for a type.
+    ///
+    /// When generating helper code for foreign language bindings, it's sometimes useful to be
+    /// able to name a particular type in order to e.g. call a helper function that is specific
+    /// to that type. We support this by defining a naming convention where each type gets a
+    /// unique canonical name, constructed recursively from the names of its component types (if any).
+    pub fn canonical_name(&self) -> String {
+        match self {
+            // Builtin primitive types, with plain old names.
+            Type::Int8 => "i8".into(),
+            Type::UInt8 => "u8".into(),
+            Type::Int16 => "i16".into(),
+            Type::UInt16 => "u16".into(),
+            Type::Int32 => "i32".into(),
+            Type::UInt32 => "u32".into(),
+            Type::Int64 => "i64".into(),
+            Type::UInt64 => "u64".into(),
+            Type::Float32 => "f32".into(),
+            Type::Float64 => "f64".into(),
+            Type::String => "string".into(),
+            Type::Boolean => "bool".into(),
+            // API defined types.
+            // Note that these all get unique names, and the parser ensures that the names do not
+            // conflict with a builtin type. We add a prefix to the name to guard against pathological
+            // cases like a record named `SequenceRecord` interfering with `sequence<Record>`.
+            // However, types that support importing all end up with the same prefix of "Type", so
+            // that the import handling code knows how to find the remote reference.
+            Type::Object(nm) => format!("Type{nm}"),
+            Type::Error(nm) => format!("Type{nm}"),
+            Type::Enum(nm) => format!("Type{nm}"),
+            Type::Record(nm) => format!("Type{nm}"),
+            Type::CallbackInterface(nm) => format!("CallbackInterface{nm}"),
+            Type::Timestamp => "Timestamp".into(),
+            Type::Duration => "Duration".into(),
+            // Recursive types.
+            // These add a prefix to the name of the underlying type.
+            // The component API definition cannot give names to recursive types, so as long as the
+            // prefixes we add here are all unique amongst themselves, then we have no chance of
+            // acccidentally generating name collisions.
+            Type::Optional(t) => format!("Optional{}", t.canonical_name()),
+            Type::Sequence(t) => format!("Sequence{}", t.canonical_name()),
+            Type::Map(k, v) => format!(
+                "Map{}{}",
+                k.canonical_name().to_upper_camel_case(),
+                v.canonical_name().to_upper_camel_case()
+            ),
+            // A type that exists externally.
+            Type::External { name, .. } | Type::Custom { name, .. } => format!("Type{name}"),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before calling canonical_name")
+            }
+        }
+    }
+
+    pub fn ffi_type(&self) -> FFIType {
+        self.into()
+    }
+
+    pub fn iter_types(&self) -> TypeIterator<'_> {
+        let nested_types = match self {
+            Type::Optional(t) | Type::Sequence(t) => t.iter_types(),
+            Type::Map(k, v) => Box::new(k.iter_types().chain(v.iter_types())),
+            _ => Box::new(iter::empty()),
+        };
+        Box::new(std::iter::once(self).chain(nested_types))
+    }
+}
+
+/// When passing data across the FFI, each `Type` value will be lowered into a corresponding
+/// `FFIType` value. This conversion tells you which one.
+///
+/// Note that the conversion is one-way - given an FFIType, it is not in general possible to
+/// tell what the corresponding Type is that it's being used to represent.
+impl From<&Type> for FFIType {
+    fn from(t: &Type) -> FFIType {
+        match t {
+            // Types that are the same map to themselves, naturally.
+            Type::UInt8 => FFIType::UInt8,
+            Type::Int8 => FFIType::Int8,
+            Type::UInt16 => FFIType::UInt16,
+            Type::Int16 => FFIType::Int16,
+            Type::UInt32 => FFIType::UInt32,
+            Type::Int32 => FFIType::Int32,
+            Type::UInt64 => FFIType::UInt64,
+            Type::Int64 => FFIType::Int64,
+            Type::Float32 => FFIType::Float32,
+            Type::Float64 => FFIType::Float64,
+            // Booleans lower into an Int8, to work around a bug in JNA.
+            Type::Boolean => FFIType::Int8,
+            // Strings are always owned rust values.
+            // We might add a separate type for borrowed strings in future.
+            Type::String => FFIType::RustBuffer,
+            // Objects are pointers to an Arc<>
+            Type::Object(name) => FFIType::RustArcPtr(name.to_owned()),
+            // Callback interfaces are passed as opaque integer handles.
+            Type::CallbackInterface(_) => FFIType::UInt64,
+            // Other types are serialized into a bytebuffer and deserialized on the other side.
+            Type::Enum(_)
+            | Type::Error(_)
+            | Type::Record(_)
+            | Type::Optional(_)
+            | Type::Sequence(_)
+            | Type::Map(_, _)
+            | Type::Timestamp
+            | Type::Duration
+            | Type::External { .. } => FFIType::RustBuffer,
+            Type::Custom { builtin, .. } => FFIType::from(builtin.as_ref()),
+            Type::Unresolved { .. } => {
+                unreachable!("Type must be resolved before lowering to FFIType")
+            }
+        }
+    }
+}
+
+// Needed for rust scaffolding askama template
+impl From<&&Type> for FFIType {
+    fn from(ty: &&Type) -> Self {
+        (*ty).into()
+    }
+}
+
+/// The set of all possible types used in a particular component interface.
+///
+/// Every component API uses a finite number of types, including primitive types, API-defined
+/// types like records and enums, and recursive types such as sequences of the above. Our
+/// component API doesn't support fancy generics so this is a finitely-enumerable set, which
+/// is useful to be able to operate on explicitly.
+///
+/// You could imagine this struct doing some clever interning of names and so-on in future,
+/// to reduce the overhead of passing around [Type] instances. For now we just do a whole
+/// lot of cloning.
+#[derive(Debug, Default)]
+pub(crate) struct TypeUniverse {
+    // Named type definitions (including aliases).
+    type_definitions: HashMap<String, Type>,
+    // All the types in the universe, by canonical type name, in a well-defined order.
+    all_known_types: BTreeSet<Type>,
+}
+
+impl TypeUniverse {
+    /// Add the definitions of all named [Type]s from a given WebIDL definition.
+    ///
+    /// This will fail if you try to add a name for which an existing type definition exists.
+    pub(super) fn add_type_definitions_from<T: TypeFinder>(&mut self, defn: T) -> Result<()> {
+        defn.add_type_definitions_to(self)
+    }
+
+    /// Add the definition of a named [Type].
+    ///
+    /// This will fail if you try to add a name for which an existing type definition exists.
+    pub fn add_type_definition(&mut self, name: &str, type_: Type) -> Result<()> {
+        if resolve_builtin_type(name).is_some() {
+            bail!(
+                "please don't shadow builtin types ({name}, {})",
+                type_.canonical_name(),
+            );
+        }
+        self.add_known_type(&type_);
+        match self.type_definitions.entry(name.to_string()) {
+            Entry::Occupied(_) => bail!("Conflicting type definition for \"{name}\""),
+            Entry::Vacant(e) => {
+                e.insert(type_);
+                Ok(())
+            }
+        }
+    }
+
+    /// Get the [Type] corresponding to a given name, if any.
+    pub(super) fn get_type_definition(&self, name: &str) -> Option<Type> {
+        self.type_definitions.get(name).cloned()
+    }
+
+    /// Get the [Type] corresponding to a given WebIDL type node.
+    ///
+    /// If the node is a structural type (e.g. a sequence) then this will also add
+    /// it to the set of all types seen in the component interface.
+    pub(crate) fn resolve_type_expression<T: TypeResolver>(&mut self, expr: T) -> Result<Type> {
+        expr.resolve_type_expression(self)
+    }
+
+    /// Add a [Type] to the set of all types seen in the component interface.
+    pub fn add_known_type(&mut self, type_: &Type) {
+        // Don't add unresolved types, they are only useful as placeholders
+        // inside function / method signatures.
+        if matches!(type_, Type::Unresolved { .. }) {
+            return;
+        }
+
+        // Types are more likely to already be known than not, so avoid unnecessary cloning.
+        if !self.all_known_types.contains(type_) {
+            self.all_known_types.insert(type_.to_owned());
+
+            // Add inner types. For UDL, this is actually pointless extra work (as is calling
+            // add_known_type from add_function_definition), but for the proc-macro frontend
+            // this is important if the inner type isn't ever mentioned outside one of these
+            // generic builtin types.
+            match type_ {
+                Type::Optional(t) => self.add_known_type(t),
+                Type::Sequence(t) => self.add_known_type(t),
+                Type::Map(k, v) => {
+                    self.add_known_type(k);
+                    self.add_known_type(v);
+                }
+                _ => {}
+            }
+        }
+    }
+
+    /// Iterator over all the known types in this universe.
+    pub fn iter_known_types(&self) -> impl Iterator<Item = &Type> {
+        self.all_known_types.iter()
+    }
+}
+
+/// An abstract type for an iterator over &Type references.
+///
+/// Ideally we would not need to name this type explicitly, and could just
+/// use an `impl Iterator<Item = &Type>` on any method that yields types.
+pub type TypeIterator<'a> = Box<dyn Iterator<Item = &'a Type> + 'a>;
+
+#[cfg(test)]
+mod test_type {
+    use super::*;
+
+    #[test]
+    fn test_canonical_names() {
+        // Non-exhaustive, but gives a bit of a flavour of what we want.
+        assert_eq!(Type::UInt8.canonical_name(), "u8");
+        assert_eq!(Type::String.canonical_name(), "string");
+        assert_eq!(
+            Type::Optional(Box::new(Type::Sequence(Box::new(Type::Object(
+                "Example".into()
+            )))))
+            .canonical_name(),
+            "OptionalSequenceTypeExample"
+        );
+    }
+}
+
+#[cfg(test)]
+mod test_type_universe {
+    // All the useful functionality of the `TypeUniverse` struct
+    // is tested as part of the `TypeFinder` and `TypeResolver` test suites.
+}
diff --git a/third_party/rust/uniffi_bindgen/src/interface/types/resolver.rs b/third_party/rust/uniffi_bindgen/src/interface/types/resolver.rs
new file mode 100644
index 0000000000..d6f18c51fd
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/interface/types/resolver.rs
@@ -0,0 +1,367 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! #  Helpers for resolving UDL type expressions into concrete types.
+//!
+//! This module provides the [`TypeResolver`] trait, an abstraction for walking
+//! the parse tree of a weedle type expression and using a [`TypeUniverse`] to
+//! convert it into a concrete type definition (so it assumes that you're already
+//! used a [`TypeFinder`](super::TypeFinder) to populate the universe).
+//!
+//! Perhaps most importantly, it knows how to error out if the UDL tries to reference
+//! an undefined or invalid type.
+
+use anyhow::{bail, Result};
+
+use super::{Type, TypeUniverse};
+
+/// Trait to help resolving an UDL type node to a [`Type`].
+///
+/// Ths trait does structural matching against type-related weedle AST nodes from
+/// a parsed UDL file, turning them into a corresponding [`Type`] struct. It uses the
+/// known type definitions in a [`TypeUniverse`] to resolve names to types.
+///
+/// As a side-effect, resolving a type expression will grow the type universe with
+/// references to the types seem during traversal. For example resolving the type
+/// expression "sequence<TestRecord>?" will:
+///
+///   * add `Optional<Sequence<TestRecord>` and `Sequence<TestRecord>` to the
+///     known types in the universe.
+///   * error out if the type name `TestRecord` is not already known.
+///
+pub(crate) trait TypeResolver {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type>;
+}
+
+impl TypeResolver for &weedle::types::Type<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        (*self).resolve_type_expression(types)
+    }
+}
+
+impl TypeResolver for weedle::types::Type<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        match self {
+            weedle::types::Type::Single(t) => match t {
+                weedle::types::SingleType::Any(_) => bail!("no support for `any` types"),
+                weedle::types::SingleType::NonAny(t) => t.resolve_type_expression(types),
+            },
+            weedle::types::Type::Union(_) => bail!("no support for union types yet"),
+        }
+    }
+}
+
+impl TypeResolver for weedle::types::NonAnyType<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        match self {
+            weedle::types::NonAnyType::Boolean(t) => t.resolve_type_expression(types),
+            weedle::types::NonAnyType::Identifier(t) => t.resolve_type_expression(types),
+            weedle::types::NonAnyType::Integer(t) => t.resolve_type_expression(types),
+            weedle::types::NonAnyType::FloatingPoint(t) => t.resolve_type_expression(types),
+            weedle::types::NonAnyType::Sequence(t) => t.resolve_type_expression(types),
+            weedle::types::NonAnyType::RecordType(t) => t.resolve_type_expression(types),
+            _ => bail!("no support for type {:?}", self),
+        }
+    }
+}
+
+impl TypeResolver for &weedle::types::AttributedNonAnyType<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        if self.attributes.is_some() {
+            bail!("type attributes are not supported yet");
+        }
+        self.type_.resolve_type_expression(types)
+    }
+}
+
+impl TypeResolver for &weedle::types::AttributedType<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        if self.attributes.is_some() {
+            bail!("type attributes are not supported yet");
+        }
+        self.type_.resolve_type_expression(types)
+    }
+}
+
+impl<T: TypeResolver> TypeResolver for weedle::types::MayBeNull<T> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        let type_ = self.type_.resolve_type_expression(types)?;
+        match self.q_mark {
+            None => Ok(type_),
+            Some(_) => {
+                let ty = Type::Optional(Box::new(type_));
+                types.add_known_type(&ty);
+                Ok(ty)
+            }
+        }
+    }
+}
+
+impl TypeResolver for weedle::types::IntegerType {
+    fn resolve_type_expression(&self, _types: &mut TypeUniverse) -> Result<Type> {
+        bail!(
+            "WebIDL integer types not implemented ({:?}); consider using u8, u16, u32 or u64",
+            self
+        )
+    }
+}
+
+impl TypeResolver for weedle::types::FloatingPointType {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        match self {
+            weedle::types::FloatingPointType::Float(t) => t.resolve_type_expression(types),
+            weedle::types::FloatingPointType::Double(t) => t.resolve_type_expression(types),
+        }
+    }
+}
+
+impl TypeResolver for weedle::types::SequenceType<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        let t = self.generics.body.as_ref().resolve_type_expression(types)?;
+        let ty = Type::Sequence(Box::new(t));
+        types.add_known_type(&ty);
+        Ok(ty)
+    }
+}
+
+impl TypeResolver for weedle::types::RecordKeyType<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        use weedle::types::RecordKeyType::*;
+        match self {
+            Byte(_) | USV(_) => bail!(
+                "WebIDL Byte or USV string type not implemented ({self:?}); \
+                 consider using DOMString or string",
+            ),
+            DOM(_) => {
+                types.add_known_type(&Type::String);
+                Ok(Type::String)
+            }
+            NonAny(t) => t.resolve_type_expression(types),
+        }
+    }
+}
+
+impl TypeResolver for weedle::types::RecordType<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        let key_type = self.generics.body.0.resolve_type_expression(types)?;
+        let value_type = self.generics.body.2.resolve_type_expression(types)?;
+        let map = Type::Map(Box::new(key_type), Box::new(value_type));
+        types.add_known_type(&map);
+        Ok(map)
+    }
+}
+
+impl TypeResolver for weedle::common::Identifier<'_> {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        match resolve_builtin_type(self.0) {
+            Some(type_) => {
+                types.add_known_type(&type_);
+                Ok(type_)
+            }
+            None => match types.get_type_definition(self.0) {
+                Some(type_) => {
+                    types.add_known_type(&type_);
+                    Ok(type_)
+                }
+                None => bail!("unknown type reference: {}", self.0),
+            },
+        }
+    }
+}
+
+impl TypeResolver for weedle::term::Boolean {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        types.add_known_type(&Type::Boolean);
+        Ok(Type::Boolean)
+    }
+}
+
+impl TypeResolver for weedle::types::FloatType {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        if self.unrestricted.is_some() {
+            bail!("we don't support `unrestricted float`");
+        }
+        types.add_known_type(&Type::Float32);
+        Ok(Type::Float32)
+    }
+}
+
+impl TypeResolver for weedle::types::DoubleType {
+    fn resolve_type_expression(&self, types: &mut TypeUniverse) -> Result<Type> {
+        if self.unrestricted.is_some() {
+            bail!("we don't support `unrestricted double`");
+        }
+        types.add_known_type(&Type::Float64);
+        Ok(Type::Float64)
+    }
+}
+
+/// Resolve built-in API types by name.
+///
+/// Given an identifier from the UDL, this will return `Some(Type)` if it names one of the
+/// built-in primitive types or `None` if it names something else.
+pub(in super::super) fn resolve_builtin_type(name: &str) -> Option<Type> {
+    match name {
+        "string" => Some(Type::String),
+        "u8" => Some(Type::UInt8),
+        "i8" => Some(Type::Int8),
+        "u16" => Some(Type::UInt16),
+        "i16" => Some(Type::Int16),
+        "u32" => Some(Type::UInt32),
+        "i32" => Some(Type::Int32),
+        "u64" => Some(Type::UInt64),
+        "i64" => Some(Type::Int64),
+        "f32" => Some(Type::Float32),
+        "f64" => Some(Type::Float64),
+        "timestamp" => Some(Type::Timestamp),
+        "duration" => Some(Type::Duration),
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use weedle::Parse;
+
+    #[test]
+    fn test_named_type_resolution() -> Result<()> {
+        let mut types = TypeUniverse::default();
+        types.add_type_definition("TestRecord", Type::Record("TestRecord".into()))?;
+        assert_eq!(types.iter_known_types().count(), 1);
+
+        let (_, expr) = weedle::types::Type::parse("TestRecord").unwrap();
+        let t = types.resolve_type_expression(expr).unwrap();
+        assert!(matches!(t, Type::Record(nm) if nm == "TestRecord"));
+        assert_eq!(types.iter_known_types().count(), 1);
+
+        let (_, expr) = weedle::types::Type::parse("TestRecord?").unwrap();
+        let t = types.resolve_type_expression(expr).unwrap();
+        assert!(matches!(t, Type::Optional(_)));
+        // Matching the Box<T> is hard, use names as a convenient workaround.
+        assert_eq!(t.canonical_name(), "OptionalTypeTestRecord");
+        assert_eq!(types.iter_known_types().count(), 2);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_resolving_optional_type_adds_inner_type() {
+        let mut types = TypeUniverse::default();
+        assert_eq!(types.iter_known_types().count(), 0);
+        let (_, expr) = weedle::types::Type::parse("u32?").unwrap();
+        let t = types.resolve_type_expression(expr).unwrap();
+        assert_eq!(t.canonical_name(), "Optionalu32");
+        assert_eq!(types.iter_known_types().count(), 2);
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "u32"));
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "Optionalu32"));
+    }
+
+    #[test]
+    fn test_resolving_sequence_type_adds_inner_type() {
+        let mut types = TypeUniverse::default();
+        assert_eq!(types.iter_known_types().count(), 0);
+        let (_, expr) = weedle::types::Type::parse("sequence<string>").unwrap();
+        let t = types.resolve_type_expression(expr).unwrap();
+        assert_eq!(t.canonical_name(), "Sequencestring");
+        assert_eq!(types.iter_known_types().count(), 2);
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "Sequencestring"));
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "string"));
+    }
+
+    #[test]
+    fn test_resolving_map_type_adds_string_and_inner_type() {
+        let mut types = TypeUniverse::default();
+        assert_eq!(types.iter_known_types().count(), 0);
+        let (_, expr) = weedle::types::Type::parse("record<DOMString, float>").unwrap();
+        let t = types.resolve_type_expression(expr).unwrap();
+        assert_eq!(t.canonical_name(), "MapStringF32");
+        assert_eq!(types.iter_known_types().count(), 3);
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "MapStringF32"));
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "string"));
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "f32"));
+    }
+
+    #[test]
+    fn test_resolving_map_type_adds_key_type_and_inner_type() {
+        let mut types = TypeUniverse::default();
+        assert_eq!(types.iter_known_types().count(), 0);
+        let (_, expr) = weedle::types::Type::parse("record<u64, float>").unwrap();
+        let t = types.resolve_type_expression(expr).unwrap();
+        assert_eq!(t.canonical_name(), "MapU64F32");
+        assert_eq!(types.iter_known_types().count(), 3);
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "MapU64F32"));
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "u64"));
+        assert!(types
+            .iter_known_types()
+            .any(|t| t.canonical_name() == "f32"));
+    }
+
+    #[test]
+    fn test_error_on_unknown_type() -> Result<()> {
+        let mut types = TypeUniverse::default();
+        types.add_type_definition("TestRecord", Type::Record("TestRecord".into()))?;
+        // Oh no, someone made a typo in the type-o...
+        let (_, expr) = weedle::types::Type::parse("TestRecrd").unwrap();
+        let err = types.resolve_type_expression(expr).unwrap_err();
+        assert_eq!(err.to_string(), "unknown type reference: TestRecrd");
+        Ok(())
+    }
+
+    #[test]
+    fn test_error_on_union_type() -> Result<()> {
+        let mut types = TypeUniverse::default();
+        types.add_type_definition("TestRecord", Type::Record("TestRecord".into()))?;
+        let (_, expr) = weedle::types::Type::parse("(TestRecord or u32)").unwrap();
+        let err = types.resolve_type_expression(expr).unwrap_err();
+        assert_eq!(err.to_string(), "no support for union types yet");
+        Ok(())
+    }
+
+    #[test]
+    fn test_type_set_is_well_ordered() -> Result<()> {
+        // The set (universe) of types should have a well-defined order. When
+        // the data structure does not guarantee the order of its elements, such as
+        // HashSet, then the resulting generated source code is likely not
+        // deterministic, and the compiled binary file may not be reproducible. We
+        // avoid this issue by using an implementation that defines the order of its
+        // elements. This test verifies that the elements are sorted as expected.
+        let mut types = TypeUniverse::default();
+        types.add_type_definition("TestRecord", Type::Record("TestRecord".into()))?;
+        assert_eq!(types.iter_known_types().count(), 1);
+        types.add_type_definition("TestRecord2", Type::Record("TestRecord2".into()))?;
+        assert_eq!(types.iter_known_types().count(), 2);
+        types.add_type_definition("TestInt64", Type::Int64)?;
+        types.add_type_definition("TestInt8", Type::Int8)?;
+        types.add_type_definition("TestUInt8", Type::UInt8)?;
+        types.add_type_definition("TestBoolean", Type::Boolean)?;
+        assert_eq!(types.iter_known_types().count(), 6);
+        let mut iter = types.iter_known_types();
+        assert_eq!(Some(&Type::UInt8), iter.next());
+        assert_eq!(Some(&Type::Int8), iter.next());
+        assert_eq!(Some(&Type::Int64), iter.next());
+        assert_eq!(Some(&Type::Boolean), iter.next());
+        assert_eq!(Some(&Type::Record("TestRecord".into())), iter.next());
+        assert_eq!(Some(&Type::Record("TestRecord2".into())), iter.next());
+        Ok(())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/lib.rs b/third_party/rust/uniffi_bindgen/src/lib.rs
new file mode 100644
index 0000000000..e6e44d9929
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/lib.rs
@@ -0,0 +1,661 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! # Uniffi: easily build cross-platform software components in Rust
+//!
+//! This is a highly-experimental crate for building cross-language software components
+//! in Rust, based on things we've learned and patterns we've developed in the
+//! [mozilla/application-services](https://github.com/mozilla/application-services) project.
+//!
+//! The idea is to let you write your code once, in Rust, and then re-use it from many
+//! other programming languages via Rust's C-compatible FFI layer and some automagically
+//! generated binding code. If you think of it as a kind of [wasm-bindgen](https://github.com/rustwasm/wasm-bindgen)
+//! wannabe, with a clunkier developer experience but support for more target languages,
+//! you'll be pretty close to the mark.
+//!
+//! Currently supported target languages include Kotlin, Swift and Python.
+//!
+//! ## Usage
+//
+//! To build a cross-language component using `uniffi`, follow these steps.
+//!
+//! ### 1) Specify your Component Interface
+//!
+//! Start by thinking about the interface you want to expose for use
+//! from other languages. Use the Interface Definition Language to specify your interface
+//! in a `.udl` file, where it can be processed by the tools from this crate.
+//! For example you might define an interface like this:
+//!
+//! ```text
+//! namespace example {
+//!   u32 foo(u32 bar);
+//! }
+//!
+//! dictionary MyData {
+//!   u32 num_foos;
+//!   bool has_a_bar;
+//! }
+//! ```
+//!
+//! ### 2) Implement the Component Interface as a Rust crate
+//!
+//! With the interface, defined, provide a corresponding implementation of that interface
+//! as a standard-looking Rust crate, using functions and structs and so-on. For example
+//! an implementation of the above Component Interface might look like this:
+//!
+//! ```text
+//! fn foo(bar: u32) -> u32 {
+//!     // TODO: a better example!
+//!     bar + 42
+//! }
+//!
+//! struct MyData {
+//!   num_foos: u32,
+//!   has_a_bar: bool
+//! }
+//! ```
+//!
+//! ### 3) Generate and include component scaffolding from the UDL file
+//!
+//! First you will need to install `uniffi-bindgen` on your system using `cargo install uniffi_bindgen`.
+//! Then add to your crate `uniffi_build` under `[build-dependencies]`.
+//! Finally, add a `build.rs` script to your crate and have it call `uniffi_build::generate_scaffolding`
+//! to process your `.udl` file. This will generate some Rust code to be included in the top-level source
+//! code of your crate. If your UDL file is named `example.udl`, then your build script would call:
+//!
+//! ```text
+//! uniffi_build::generate_scaffolding("./src/example.udl")
+//! ```
+//!
+//! This would output a rust file named `example.uniffi.rs`, ready to be
+//! included into the code of your rust crate like this:
+//!
+//! ```text
+//! include!(concat!(env!("OUT_DIR"), "/example.uniffi.rs"));
+//! ```
+//!
+//! ### 4) Generate foreign language bindings for the library
+//!
+//! The `uniffi-bindgen` utility provides a command-line tool that can produce code to
+//! consume the Rust library in any of several supported languages.
+//! It is done by calling (in kotlin for example):
+//!
+//! ```text
+//! uniffi-bindgen --language kotlin ./src/example.udl
+//! ```
+//!
+//! This will produce a file `example.kt` in the same directory as the .udl file, containing kotlin bindings
+//! to load and use the compiled rust code via its C-compatible FFI.
+//!
+
+#![warn(rust_2018_idioms, unused_qualifications)]
+#![allow(unknown_lints)]
+
+const BINDGEN_VERSION: &str = env!("CARGO_PKG_VERSION");
+
+use anyhow::{anyhow, bail, Context, Result};
+use camino::{Utf8Path, Utf8PathBuf};
+use clap::{Parser, Subcommand};
+use fs_err::{self as fs, File};
+use serde::{Deserialize, Serialize};
+use std::io::prelude::*;
+use std::io::ErrorKind;
+use std::{collections::HashMap, env, process::Command, str::FromStr};
+
+pub mod backend;
+pub mod bindings;
+pub mod interface;
+pub mod macro_metadata;
+pub mod scaffolding;
+
+use bindings::TargetLanguage;
+pub use interface::ComponentInterface;
+use scaffolding::RustScaffolding;
+
+/// A trait representing a Binding Generator Configuration
+///
+/// External crates that implement binding generators need to implement this trait and set it as
+/// the `BindingGenerator.config` associated type.  `generate_external_bindings()` then uses it to
+/// generate the config that's passed to `BindingGenerator.write_bindings()`
+pub trait BindingGeneratorConfig: for<'de> Deserialize<'de> {
+    /// Get the entry for this config from the `bindings` table.
+    fn get_entry_from_bindings_table(bindings: &toml::Value) -> Option<toml::Value>;
+
+    /// Get default config values from the `ComponentInterface`
+    ///
+    /// These will replace missing entries in the bindings-specific config
+    fn get_config_defaults(ci: &ComponentInterface) -> Vec<(String, toml::Value)>;
+}
+
+fn load_bindings_config<BC: BindingGeneratorConfig>(
+    ci: &ComponentInterface,
+    crate_root: &Utf8Path,
+    config_file_override: Option<&Utf8Path>,
+) -> Result<BC> {
+    // Load the config from the TOML value, falling back to an empty map if it doesn't exist
+    let mut config_map: toml::value::Table =
+        match load_bindings_config_toml::<BC>(crate_root, config_file_override)? {
+            Some(value) => value
+                .try_into()
+                .context("Bindings config must be a TOML table")?,
+            None => toml::map::Map::new(),
+        };
+
+    // Update it with the defaults from the component interface
+    for (key, value) in BC::get_config_defaults(ci) {
+        config_map.entry(key).or_insert(value);
+    }
+
+    // Leverage serde to convert toml::Value into the config type
+    toml::Value::from(config_map)
+        .try_into()
+        .context("Generating bindings config from toml::Value")
+}
+
+/// Binding generator config with no members
+#[derive(Clone, Debug, Hash, PartialEq, PartialOrd, Ord, Eq)]
+pub struct EmptyBindingGeneratorConfig;
+
+impl BindingGeneratorConfig for EmptyBindingGeneratorConfig {
+    fn get_entry_from_bindings_table(_bindings: &toml::Value) -> Option<toml::Value> {
+        None
+    }
+
+    fn get_config_defaults(_ci: &ComponentInterface) -> Vec<(String, toml::Value)> {
+        Vec::new()
+    }
+}
+
+// EmptyBindingGeneratorConfig is a unit struct, so the `derive(Deserialize)` implementation
+// expects a null value rather than the empty map that we pass it.  So we need to implement
+// `Deserialize` ourselves.
+impl<'de> Deserialize<'de> for EmptyBindingGeneratorConfig {
+    fn deserialize<D>(_deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        Ok(EmptyBindingGeneratorConfig)
+    }
+}
+
+// Load the binding-specific config
+//
+// This function calulates the location of the config TOML file, parses it, and returns the result
+// as a toml::Value
+//
+// If there is an error parsing the file then Err will be returned. If the file is missing or the
+// entry for the bindings is missing, then Ok(None) will be returned.
+fn load_bindings_config_toml<BC: BindingGeneratorConfig>(
+    crate_root: &Utf8Path,
+    config_file_override: Option<&Utf8Path>,
+) -> Result<Option<toml::Value>> {
+    let config_path = match config_file_override {
+        Some(cfg) => cfg.to_owned(),
+        None => crate_root.join("uniffi.toml"),
+    };
+
+    if !config_path.exists() {
+        return Ok(None);
+    }
+
+    let contents = fs::read_to_string(&config_path)
+        .with_context(|| format!("Failed to read config file from {config_path}"))?;
+    let full_config = toml::Value::from_str(&contents)
+        .with_context(|| format!("Failed to parse config file {config_path}"))?;
+
+    Ok(full_config
+        .get("bindings")
+        .and_then(BC::get_entry_from_bindings_table))
+}
+
+/// A trait representing a UniFFI Binding Generator
+///
+/// External crates that implement binding generators, should implement this type
+/// and call the [`generate_external_bindings`] using a type that implements this trait.
+pub trait BindingGenerator: Sized {
+    /// Associated type representing a the bindings-specifig configuration parsed from the
+    /// uniffi.toml
+    type Config: BindingGeneratorConfig;
+
+    /// Writes the bindings to the output directory
+    ///
+    /// # Arguments
+    /// - `ci`: A [`ComponentInterface`] representing the interface
+    /// - `config`: A instance of the BindingGeneratorConfig associated with this type
+    /// - `out_dir`: The path to where the binding generator should write the output bindings
+    fn write_bindings(
+        &self,
+        ci: ComponentInterface,
+        config: Self::Config,
+        out_dir: &Utf8Path,
+    ) -> Result<()>;
+}
+
+/// Generate bindings for an external binding generator
+/// Ideally, this should replace the [`generate_bindings`] function below
+///
+/// Implements an entry point for external binding generators.
+/// The function does the following:
+/// - It parses the `udl` in a [`ComponentInterface`]
+/// - Parses the `uniffi.toml` and loads it into the type that implements [`BindingGeneratorConfig`]
+/// - Creates an instance of [`BindingGenerator`], based on type argument `B`, and run [`BindingGenerator::write_bindings`] on it
+///
+/// # Arguments
+/// - `binding_generator`: Type that implements BindingGenerator
+/// - `udl_file`: The path to the UDL file
+/// - `config_file_override`: The path to the configuration toml file, most likely called `uniffi.toml`. If [`None`], the function will try to guess based on the crate's root.
+/// - `out_dir_override`: The path to write the bindings to. If [`None`], it will be the path to the parent directory of the `udl_file`
+pub fn generate_external_bindings(
+    binding_generator: impl BindingGenerator,
+    udl_file: impl AsRef<Utf8Path>,
+    config_file_override: Option<impl AsRef<Utf8Path>>,
+    out_dir_override: Option<impl AsRef<Utf8Path>>,
+) -> Result<()> {
+    let out_dir_override = out_dir_override.as_ref().map(|p| p.as_ref());
+    let config_file_override = config_file_override.as_ref().map(|p| p.as_ref());
+
+    let crate_root = guess_crate_root(udl_file.as_ref())?;
+    let out_dir = get_out_dir(udl_file.as_ref(), out_dir_override)?;
+    let component = parse_udl(udl_file.as_ref()).context("Error parsing UDL")?;
+    let bindings_config = load_bindings_config(&component, crate_root, config_file_override)?;
+    binding_generator.write_bindings(component, bindings_config, &out_dir)
+}
+
+// Generate the infrastructural Rust code for implementing the UDL interface,
+// such as the `extern "C"` function definitions and record data types.
+pub fn generate_component_scaffolding(
+    udl_file: &Utf8Path,
+    config_file_override: Option<&Utf8Path>,
+    out_dir_override: Option<&Utf8Path>,
+    format_code: bool,
+) -> Result<()> {
+    let component = parse_udl(udl_file)?;
+    let _config = get_config(
+        &component,
+        guess_crate_root(udl_file)?,
+        config_file_override,
+    );
+    let file_stem = udl_file.file_stem().context("not a file")?;
+    let filename = format!("{file_stem}.uniffi.rs");
+    let out_path = get_out_dir(udl_file, out_dir_override)?.join(filename);
+    let mut f = File::create(&out_path)?;
+    write!(f, "{}", RustScaffolding::new(&component)).context("Failed to write output file")?;
+    if format_code {
+        format_code_with_rustfmt(&out_path)?;
+    }
+    Ok(())
+}
+
+// Generate the bindings in the target languages that call the scaffolding
+// Rust code.
+pub fn generate_bindings(
+    udl_file: &Utf8Path,
+    config_file_override: Option<&Utf8Path>,
+    target_languages: Vec<&str>,
+    out_dir_override: Option<&Utf8Path>,
+    library_file: Option<&Utf8Path>,
+    try_format_code: bool,
+) -> Result<()> {
+    let mut component = parse_udl(udl_file)?;
+    if let Some(library_file) = library_file {
+        macro_metadata::add_to_ci_from_library(&mut component, library_file)?;
+    }
+    let crate_root = &guess_crate_root(udl_file)?;
+
+    let config = get_config(&component, crate_root, config_file_override)?;
+    let out_dir = get_out_dir(udl_file, out_dir_override)?;
+    for language in target_languages {
+        bindings::write_bindings(
+            &config.bindings,
+            &component,
+            &out_dir,
+            language.try_into()?,
+            try_format_code,
+        )?;
+    }
+
+    Ok(())
+}
+
+pub fn dump_json(library_path: &Utf8Path) -> Result<String> {
+    let metadata = macro_metadata::extract_from_library(library_path)?;
+    Ok(serde_json::to_string_pretty(&metadata)?)
+}
+
+pub fn print_json(library_path: &Utf8Path) -> Result<()> {
+    println!("{}", dump_json(library_path)?);
+    Ok(())
+}
+
+// Run tests against the foreign language bindings (generated and compiled at the same time).
+// Note that the cdylib we're testing against must be built already.
+pub fn run_tests(
+    library_file: impl AsRef<Utf8Path>,
+    udl_files: &[impl AsRef<Utf8Path>],
+    test_scripts: &[impl AsRef<Utf8Path>],
+    config_file_override: Option<&Utf8Path>,
+) -> Result<()> {
+    // XXX - this is just for tests, so one config_file_override for all .udl files doesn't really
+    // make sense, so we don't let tests do this.
+    // "Real" apps will build the .udl files one at a file and can therefore do whatever they want
+    // with overrides, so don't have this problem.
+    assert!(udl_files.len() == 1 || config_file_override.is_none());
+
+    let library_file = library_file.as_ref();
+    let cdylib_dir = library_file
+        .parent()
+        .context("Generated cdylib has no parent directory")?;
+
+    let metadata_items = macro_metadata::extract_from_library(library_file)?;
+
+    // Group the test scripts by language first.
+    let mut language_tests: HashMap<TargetLanguage, Vec<_>> = HashMap::new();
+
+    for test_script in test_scripts {
+        let test_script = test_script.as_ref();
+        let lang: TargetLanguage = test_script
+            .extension()
+            .context("File has no extension!")?
+            .try_into()?;
+        language_tests
+            .entry(lang)
+            .or_default()
+            .push(test_script.to_owned());
+    }
+
+    for (lang, test_scripts) in language_tests {
+        for udl_file in udl_files {
+            let udl_file = udl_file.as_ref();
+            let crate_root = guess_crate_root(udl_file)?;
+            let mut component = parse_udl(udl_file)?;
+            macro_metadata::add_to_ci(&mut component, metadata_items.clone())?;
+
+            let config = get_config(&component, crate_root, config_file_override)?;
+            bindings::write_bindings(&config.bindings, &component, cdylib_dir, lang, true)?;
+            bindings::compile_bindings(&config.bindings, &component, cdylib_dir, lang)?;
+        }
+
+        for test_script in test_scripts {
+            bindings::run_script(cdylib_dir, &test_script, lang)?;
+        }
+    }
+    Ok(())
+}
+
+/// Guess the root directory of the crate from the path of its UDL file.
+///
+/// For now, we assume that the UDL file is in `./src/something.udl` relative
+/// to the crate root. We might consider something more sophisticated in
+/// future.
+pub fn guess_crate_root(udl_file: &Utf8Path) -> Result<&Utf8Path> {
+    let path_guess = udl_file
+        .parent()
+        .context("UDL file has no parent folder!")?
+        .parent()
+        .context("UDL file has no grand-parent folder!")?;
+    if !path_guess.join("Cargo.toml").is_file() {
+        bail!("UDL file does not appear to be inside a crate")
+    }
+    Ok(path_guess)
+}
+
+fn get_config(
+    component: &ComponentInterface,
+    crate_root: &Utf8Path,
+    config_file_override: Option<&Utf8Path>,
+) -> Result<Config> {
+    let default_config: Config = component.into();
+
+    let config_file = match config_file_override {
+        Some(cfg) => Some(cfg.to_owned()),
+        None => crate_root.join("uniffi.toml").canonicalize_utf8().ok(),
+    };
+
+    match config_file {
+        Some(path) => {
+            let contents = fs::read_to_string(&path)
+                .with_context(|| format!("Failed to read config file from {path}"))?;
+            let loaded_config: Config = toml::de::from_str(&contents)
+                .with_context(|| format!("Failed to generate config from file {path}"))?;
+            Ok(loaded_config.merge_with(&default_config))
+        }
+        None => Ok(default_config),
+    }
+}
+
+fn get_out_dir(udl_file: &Utf8Path, out_dir_override: Option<&Utf8Path>) -> Result<Utf8PathBuf> {
+    Ok(match out_dir_override {
+        Some(s) => {
+            // Create the directory if it doesn't exist yet.
+            fs::create_dir_all(s)?;
+            s.canonicalize_utf8().context("Unable to find out-dir")?
+        }
+        None => udl_file
+            .parent()
+            .context("File has no parent directory")?
+            .to_owned(),
+    })
+}
+
+fn parse_udl(udl_file: &Utf8Path) -> Result<ComponentInterface> {
+    let udl = fs::read_to_string(udl_file)
+        .with_context(|| format!("Failed to read UDL from {udl_file}"))?;
+    ComponentInterface::from_webidl(&udl).context("Failed to parse UDL")
+}
+
+fn format_code_with_rustfmt(path: &Utf8Path) -> Result<()> {
+    let status = Command::new("rustfmt").arg(path).status().map_err(|e| {
+        let ctx = match e.kind() {
+            ErrorKind::NotFound => "formatting was requested, but rustfmt was not found",
+            _ => "unknown error when calling rustfmt",
+        };
+        anyhow!(e).context(ctx)
+    })?;
+    if !status.success() {
+        bail!("rustmt failed when formatting scaffolding. Note: --no-format can be used to skip formatting");
+    }
+    Ok(())
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+struct Config {
+    #[serde(default)]
+    bindings: bindings::Config,
+}
+
+impl From<&ComponentInterface> for Config {
+    fn from(ci: &ComponentInterface) -> Self {
+        Config {
+            bindings: ci.into(),
+        }
+    }
+}
+
+pub trait MergeWith {
+    fn merge_with(&self, other: &Self) -> Self;
+}
+
+impl MergeWith for Config {
+    fn merge_with(&self, other: &Self) -> Self {
+        Config {
+            bindings: self.bindings.merge_with(&other.bindings),
+        }
+    }
+}
+
+impl<T: Clone> MergeWith for Option<T> {
+    fn merge_with(&self, other: &Self) -> Self {
+        match (self, other) {
+            (Some(_), _) => self.clone(),
+            (None, Some(_)) => other.clone(),
+            (None, None) => None,
+        }
+    }
+}
+
+impl<V: Clone> MergeWith for HashMap<String, V> {
+    fn merge_with(&self, other: &Self) -> Self {
+        let mut merged = HashMap::new();
+        // Iterate through other first so our keys override theirs
+        for (key, value) in other.iter().chain(self) {
+            merged.insert(key.clone(), value.clone());
+        }
+        merged
+    }
+}
+
+// structs to help our cmdline parsing. Note that docstrings below form part
+// of the "help" output.
+/// Scaffolding and bindings generator for Rust
+#[derive(Parser)]
+#[clap(name = "uniffi-bindgen")]
+#[clap(version = clap::crate_version!())]
+#[clap(propagate_version = true)]
+struct Cli {
+    #[clap(subcommand)]
+    command: Commands,
+}
+
+#[derive(Subcommand)]
+enum Commands {
+    /// Generate foreign language bindings
+    Generate {
+        /// Foreign language(s) for which to build bindings.
+        #[clap(long, short, possible_values = &["kotlin", "python", "swift", "ruby"])]
+        language: Vec<String>,
+
+        /// Directory in which to write generated files. Default is same folder as .udl file.
+        #[clap(long, short)]
+        out_dir: Option<Utf8PathBuf>,
+
+        /// Do not try to format the generated bindings.
+        #[clap(long, short)]
+        no_format: bool,
+
+        /// Path to the optional uniffi config file. If not provided, uniffi-bindgen will try to guess it from the UDL's file location.
+        #[clap(long, short)]
+        config: Option<Utf8PathBuf>,
+
+        /// Extract proc-macro metadata from a native lib (cdylib or staticlib) for this crate.
+        #[clap(long)]
+        lib_file: Option<Utf8PathBuf>,
+
+        /// Path to the UDL file.
+        udl_file: Utf8PathBuf,
+    },
+
+    /// Generate Rust scaffolding code
+    Scaffolding {
+        /// Directory in which to write generated files. Default is same folder as .udl file.
+        #[clap(long, short)]
+        out_dir: Option<Utf8PathBuf>,
+
+        /// Path to the optional uniffi config file. If not provided, uniffi-bindgen will try to guess it from the UDL's file location.
+        #[clap(long, short)]
+        config: Option<Utf8PathBuf>,
+
+        /// Do not try to format the generated bindings.
+        #[clap(long, short)]
+        no_format: bool,
+
+        /// Path to the UDL file.
+        udl_file: Utf8PathBuf,
+    },
+
+    /// Run test scripts against foreign language bindings.
+    Test {
+        /// Path to the library the scripts will be testing against.
+        library_file: Utf8PathBuf,
+
+        /// Path to the UDL file.
+        udl_file: Utf8PathBuf,
+
+        /// Foreign language(s) test scripts to run.
+        test_scripts: Vec<Utf8PathBuf>,
+
+        /// Path to the optional uniffi config file. If not provided, uniffi-bindgen will try to guess it from the UDL's file location.
+        #[clap(long, short)]
+        config: Option<Utf8PathBuf>,
+    },
+
+    /// Print the JSON representation of the interface from a dynamic library
+    PrintJson {
+        /// Path to the library file (.so, .dll, .dylib, or .a)
+        path: Utf8PathBuf,
+    },
+}
+
+pub fn run_main() -> Result<()> {
+    let cli = Cli::parse();
+    match &cli.command {
+        Commands::Generate {
+            language,
+            out_dir,
+            no_format,
+            config,
+            lib_file,
+            udl_file,
+        } => generate_bindings(
+            udl_file,
+            config.as_deref(),
+            language.iter().map(String::as_str).collect(),
+            out_dir.as_deref(),
+            lib_file.as_deref(),
+            !no_format,
+        ),
+        Commands::Scaffolding {
+            out_dir,
+            config,
+            no_format,
+            udl_file,
+        } => generate_component_scaffolding(
+            udl_file,
+            config.as_deref(),
+            out_dir.as_deref(),
+            !no_format,
+        ),
+        Commands::Test {
+            library_file,
+            udl_file,
+            test_scripts,
+            config,
+        } => run_tests(library_file, &[udl_file], test_scripts, config.as_deref()),
+        Commands::PrintJson { path } => print_json(path),
+    }?;
+    Ok(())
+}
+
+// FIXME(HACK):
+// Include the askama config file into the build.
+// That way cargo tracks the file and other tools relying on file tracking see it as well.
+// See https://bugzilla.mozilla.org/show_bug.cgi?id=1774585
+// In the future askama should handle that itself by using the `track_path::path` API,
+// see https://github.com/rust-lang/rust/pull/84029
+#[allow(dead_code)]
+mod __unused {
+    const _: &[u8] = include_bytes!("../askama.toml");
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_guessing_of_crate_root_directory_from_udl_file() {
+        // When running this test, this will be the ./uniffi_bindgen directory.
+        let this_crate_root = Utf8PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap());
+
+        let example_crate_root = this_crate_root
+            .parent()
+            .expect("should have a parent directory")
+            .join("./examples/arithmetic");
+        assert_eq!(
+            guess_crate_root(&example_crate_root.join("./src/arthmetic.udl")).unwrap(),
+            example_crate_root
+        );
+
+        let not_a_crate_root = &this_crate_root.join("./src/templates");
+        assert!(guess_crate_root(&not_a_crate_root.join("./src/example.udl")).is_err());
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/macro_metadata/ci.rs b/third_party/rust/uniffi_bindgen/src/macro_metadata/ci.rs
new file mode 100644
index 0000000000..1ffde2542d
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/macro_metadata/ci.rs
@@ -0,0 +1,79 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::interface::{ComponentInterface, Record, Type};
+use anyhow::anyhow;
+use uniffi_meta::Metadata;
+
+/// Add Metadata items to the ComponentInterface
+///
+/// This function exists to support the transition period where the `uniffi::export` macro can only
+/// handle some components.  This means that crates need to continue using UDL files to define the
+/// parts of the components that aren't supported yet.
+///
+/// To make things work, we generate a `ComponentInterface` from the UDL file, then combine it with
+/// the `Metadata` items that the macro creates.
+pub fn add_to_ci(
+    iface: &mut ComponentInterface,
+    metadata_items: Vec<Metadata>,
+) -> anyhow::Result<()> {
+    for item in metadata_items {
+        let (item_desc, crate_name) = match &item {
+            Metadata::Func(meta) => (
+                format!("function `{}`", meta.name),
+                meta.module_path.first().unwrap(),
+            ),
+            Metadata::Method(meta) => (
+                format!("method `{}.{}`", meta.self_name, meta.name),
+                meta.module_path.first().unwrap(),
+            ),
+            Metadata::Record(meta) => (
+                format!("record `{}`", meta.name),
+                meta.module_path.first().unwrap(),
+            ),
+            Metadata::Object(meta) => (
+                format!("object `{}`", meta.name),
+                meta.module_path.first().unwrap(),
+            ),
+        };
+
+        let ns = iface.namespace();
+        if crate_name != ns {
+            return Err(anyhow!("Found {item_desc} from crate `{crate_name}`.")
+                .context(format!(
+                    "Main crate is expected to be named `{ns}` based on the UDL namespace."
+                ))
+                .context("Mixing symbols from multiple crates is not supported yet."));
+        }
+
+        match item {
+            Metadata::Func(meta) => {
+                iface.add_function_definition(meta.into())?;
+            }
+            Metadata::Method(meta) => {
+                iface.add_method_definition(meta);
+            }
+            Metadata::Record(meta) => {
+                let ty = Type::Record(meta.name.clone());
+                iface.types.add_known_type(&ty);
+                iface.types.add_type_definition(&meta.name, ty)?;
+
+                let record: Record = meta.into();
+                for field in record.fields() {
+                    iface.types.add_known_type(field.type_());
+                }
+                iface.add_record_definition(record);
+            }
+            Metadata::Object(meta) => {
+                iface.add_object_free_fn(meta);
+            }
+        }
+    }
+
+    iface.resolve_types()?;
+    iface.check_consistency()?;
+    iface.derive_ffi_funcs()?;
+
+    Ok(())
+}
diff --git a/third_party/rust/uniffi_bindgen/src/macro_metadata/extract.rs b/third_party/rust/uniffi_bindgen/src/macro_metadata/extract.rs
new file mode 100644
index 0000000000..3de10bd087
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/macro_metadata/extract.rs
@@ -0,0 +1,185 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use anyhow::{bail, Context};
+use camino::Utf8Path;
+use fs_err as fs;
+use goblin::{
+    archive::Archive,
+    elf::Elf,
+    mach::{segment::Section, symbols, Mach, MachO, SingleArch},
+    pe::PE,
+    Object,
+};
+use std::collections::HashSet;
+use uniffi_meta::Metadata;
+
+/// Extract metadata written by the `uniffi::export` macro from a library file
+///
+/// In addition to generating the scaffolding, that macro and also encodes the
+/// `uniffi_meta::Metadata` for the components which can be used to generate the bindings side of
+/// the interface.
+pub fn extract_from_library(path: &Utf8Path) -> anyhow::Result<Vec<Metadata>> {
+    extract_from_bytes(&fs::read(path)?)
+}
+
+fn extract_from_bytes(file_data: &[u8]) -> anyhow::Result<Vec<Metadata>> {
+    match Object::parse(file_data)? {
+        Object::Elf(elf) => extract_from_elf(elf, file_data),
+        Object::PE(pe) => extract_from_pe(pe, file_data),
+        Object::Mach(mach) => extract_from_mach(mach, file_data),
+        Object::Archive(archive) => extract_from_archive(archive, file_data),
+        Object::Unknown(_) => bail!("Unknown library format"),
+    }
+}
+
+pub fn extract_from_elf(elf: Elf<'_>, file_data: &[u8]) -> anyhow::Result<Vec<Metadata>> {
+    let mut extracted = ExtractedItems::new();
+    let iter = elf
+        .syms
+        .iter()
+        .filter_map(|sym| elf.section_headers.get(sym.st_shndx).map(|sh| (sym, sh)));
+
+    for (sym, sh) in iter {
+        let name = elf
+            .strtab
+            .get_at(sym.st_name)
+            .context("Error getting symbol name")?;
+        if is_metadata_symbol(name) {
+            // Offset relative to the start of the section.
+            let section_offset = sym.st_value - sh.sh_addr;
+            // Offset relative to the start of the file contents
+            extracted.extract_item(name, file_data, (sh.sh_offset + section_offset) as usize)?;
+        }
+    }
+    Ok(extracted.into_metadata())
+}
+
+pub fn extract_from_pe(pe: PE<'_>, file_data: &[u8]) -> anyhow::Result<Vec<Metadata>> {
+    let mut extracted = ExtractedItems::new();
+    for export in pe.exports {
+        if let Some(name) = export.name {
+            if is_metadata_symbol(name) {
+                extracted.extract_item(
+                    name,
+                    file_data,
+                    export.offset.context("Error getting symbol offset")?,
+                )?;
+            }
+        }
+    }
+    Ok(extracted.into_metadata())
+}
+
+pub fn extract_from_mach(mach: Mach<'_>, file_data: &[u8]) -> anyhow::Result<Vec<Metadata>> {
+    match mach {
+        Mach::Binary(macho) => extract_from_macho(macho, file_data),
+        // Multi-binary library, just extract the first one
+        Mach::Fat(multi_arch) => match multi_arch.get(0)? {
+            SingleArch::MachO(macho) => extract_from_macho(macho, file_data),
+            SingleArch::Archive(archive) => extract_from_archive(archive, file_data),
+        },
+    }
+}
+
+pub fn extract_from_macho(macho: MachO<'_>, file_data: &[u8]) -> anyhow::Result<Vec<Metadata>> {
+    let mut sections: Vec<Section> = Vec::new();
+    for sects in macho.segments.sections() {
+        sections.extend(sects.map(|r| r.expect("section").0));
+    }
+    let mut extracted = ExtractedItems::new();
+    sections.sort_by_key(|s| s.addr);
+
+    // Iterate through the symbols.  This picks up symbols from the .o files embedded in a Darwin
+    // archive.
+    for (name, nlist) in macho.symbols().flatten() {
+        // Check that the symbol:
+        //   - Is global (exported)
+        //   - Has type=N_SECT (it's regular data as opposed to something like
+        //     "undefined" or "indirect")
+        //   - Has a metadata symbol name
+        if nlist.is_global() && nlist.get_type() == symbols::N_SECT && is_metadata_symbol(name) {
+            let section = &sections[nlist.n_sect];
+            // `nlist.n_value` is an address, so we can calculating the offset inside the section
+            // using the difference between that and `section.addr`
+            let offset = section.offset as usize + nlist.n_value as usize - section.addr as usize;
+            extracted.extract_item(name, file_data, offset)?;
+        }
+    }
+
+    // Iterate through the exports.  This picks up symbols from .dylib files.
+    for export in macho.exports()? {
+        let name = &export.name;
+        if is_metadata_symbol(name) {
+            extracted.extract_item(name, file_data, export.offset as usize)?;
+        }
+    }
+    Ok(extracted.into_metadata())
+}
+
+pub fn extract_from_archive(
+    archive: Archive<'_>,
+    file_data: &[u8],
+) -> anyhow::Result<Vec<Metadata>> {
+    // Store the names of archive members that have metadata symbols in them
+    let mut members_to_check: HashSet<&str> = HashSet::new();
+    for (member_name, _, symbols) in archive.summarize() {
+        for name in symbols {
+            if is_metadata_symbol(name) {
+                members_to_check.insert(member_name);
+            }
+        }
+    }
+
+    let mut items = vec![];
+    for member_name in members_to_check {
+        items.append(&mut extract_from_bytes(
+            archive.extract(member_name, file_data)?,
+        )?);
+    }
+    Ok(items)
+}
+
+/// Container for extracted metadata items
+#[derive(Default)]
+struct ExtractedItems {
+    items: Vec<Metadata>,
+    /// symbol names for the extracted items, we use this to ensure that we don't extract the same
+    /// symbol twice
+    names: HashSet<String>,
+}
+
+impl ExtractedItems {
+    fn new() -> Self {
+        Self::default()
+    }
+
+    fn extract_item(&mut self, name: &str, file_data: &[u8], offset: usize) -> anyhow::Result<()> {
+        if self.names.contains(name) {
+            // Already extracted this item
+            return Ok(());
+        }
+
+        // Use the file data starting from offset, without specifying the end position.  We don't
+        // always know the end position, because goblin reports the symbol size as 0 for PE and
+        // MachO files.
+        //
+        // This works fine, because bincode knows when the serialized data is terminated and will
+        // just ignore the trailing data.
+        let data = &file_data[offset..];
+        self.items.push(bincode::deserialize::<Metadata>(data)?);
+        self.names.insert(name.to_string());
+        Ok(())
+    }
+
+    fn into_metadata(self) -> Vec<Metadata> {
+        self.items
+    }
+}
+
+fn is_metadata_symbol(name: &str) -> bool {
+    // Skip the "_" char that Darwin prepends, if present
+    let name = name.strip_prefix('_').unwrap_or(name);
+    name.starts_with("UNIFFI_META")
+}
diff --git a/third_party/rust/uniffi_bindgen/src/macro_metadata/mod.rs b/third_party/rust/uniffi_bindgen/src/macro_metadata/mod.rs
new file mode 100644
index 0000000000..d303418ece
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/macro_metadata/mod.rs
@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use super::ComponentInterface;
+use camino::Utf8Path;
+
+mod ci;
+mod extract;
+
+pub use ci::add_to_ci;
+pub use extract::extract_from_library;
+
+pub fn add_to_ci_from_library(
+    iface: &mut ComponentInterface,
+    library_path: &Utf8Path,
+) -> anyhow::Result<()> {
+    add_to_ci(iface, extract_from_library(library_path)?)
+}
diff --git a/third_party/rust/uniffi_bindgen/src/main.rs b/third_party/rust/uniffi_bindgen/src/main.rs
new file mode 100644
index 0000000000..8f4d553557
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/main.rs
@@ -0,0 +1,9 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use anyhow::Result;
+
+fn main() -> Result<()> {
+    uniffi_bindgen::run_main()
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/mod.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/mod.rs
new file mode 100644
index 0000000000..df170f240f
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/mod.rs
@@ -0,0 +1,152 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use anyhow::Result;
+use askama::Template;
+use std::borrow::Borrow;
+
+use super::interface::*;
+use heck::ToSnakeCase;
+
+#[derive(Template)]
+#[template(syntax = "rs", escape = "none", path = "scaffolding_template.rs")]
+pub struct RustScaffolding<'a> {
+    ci: &'a ComponentInterface,
+    uniffi_version: &'static str,
+}
+impl<'a> RustScaffolding<'a> {
+    pub fn new(ci: &'a ComponentInterface) -> Self {
+        Self {
+            ci,
+            uniffi_version: crate::BINDGEN_VERSION,
+        }
+    }
+}
+mod filters {
+    use super::*;
+
+    pub fn type_rs(type_: &Type) -> Result<String, askama::Error> {
+        Ok(match type_ {
+            Type::Int8 => "i8".into(),
+            Type::UInt8 => "u8".into(),
+            Type::Int16 => "i16".into(),
+            Type::UInt16 => "u16".into(),
+            Type::Int32 => "i32".into(),
+            Type::UInt32 => "u32".into(),
+            Type::Int64 => "i64".into(),
+            Type::UInt64 => "u64".into(),
+            Type::Float32 => "f32".into(),
+            Type::Float64 => "f64".into(),
+            Type::Boolean => "bool".into(),
+            Type::String => "String".into(),
+            Type::Timestamp => "std::time::SystemTime".into(),
+            Type::Duration => "std::time::Duration".into(),
+            Type::Enum(name) | Type::Record(name) | Type::Error(name) => format!("r#{}", name),
+            Type::Object(name) => format!("std::sync::Arc<r#{}>", name),
+            Type::CallbackInterface(name) => format!("Box<dyn r#{}>", name),
+            Type::Optional(t) => format!("std::option::Option<{}>", type_rs(t)?),
+            Type::Sequence(t) => format!("std::vec::Vec<{}>", type_rs(t)?),
+            Type::Map(k, v) => format!(
+                "std::collections::HashMap<{}, {}>",
+                type_rs(k)?,
+                type_rs(v)?
+            ),
+            Type::Custom { name, .. } => format!("r#{}", name),
+            Type::External { .. } => panic!("External types coming to a uniffi near you soon!"),
+            Type::Unresolved { .. } => {
+                unreachable!("UDL scaffolding code never contains unresolved types")
+            }
+        })
+    }
+
+    pub fn type_ffi(type_: &FFIType) -> Result<String, askama::Error> {
+        Ok(match type_ {
+            FFIType::Int8 => "i8".into(),
+            FFIType::UInt8 => "u8".into(),
+            FFIType::Int16 => "i16".into(),
+            FFIType::UInt16 => "u16".into(),
+            FFIType::Int32 => "i32".into(),
+            FFIType::UInt32 => "u32".into(),
+            FFIType::Int64 => "i64".into(),
+            FFIType::UInt64 => "u64".into(),
+            FFIType::Float32 => "f32".into(),
+            FFIType::Float64 => "f64".into(),
+            FFIType::RustArcPtr(_) => "*const std::os::raw::c_void".into(),
+            FFIType::RustBuffer => "uniffi::RustBuffer".into(),
+            FFIType::ForeignBytes => "uniffi::ForeignBytes".into(),
+            FFIType::ForeignCallback => "uniffi::ForeignCallback".into(),
+        })
+    }
+
+    /// Get the name of the FfiConverter implementation for this type
+    ///
+    /// - For primitives / standard types this is the type itself.
+    /// - For user-defined types, this is a unique generated name.  We then generate a unit-struct
+    ///   in the scaffolding code that implements FfiConverter.
+    pub fn ffi_converter_name(type_: &Type) -> askama::Result<String> {
+        Ok(match type_ {
+            // Timestamp/Duraration are handled by standard types
+            Type::Timestamp => "std::time::SystemTime".into(),
+            Type::Duration => "std::time::Duration".into(),
+            // Object is handled by Arc<T>
+            Type::Object(name) => format!("std::sync::Arc<r#{}>", name),
+            // Other user-defined types are handled by a unit-struct that we generate.  The
+            // FfiConverter implementation for this can be found in one of the scaffolding template code.
+            //
+            // We generate a unit-struct to sidestep Rust's orphan rules (ADR-0006).
+            //
+            // CallbackInterface is handled by special case code on both the scaffolding and
+            // bindings side.  It's not a unit-struct, but the same name generation code works.
+            Type::Enum(_) | Type::Record(_) | Type::Error(_) | Type::CallbackInterface(_) => {
+                format!("FfiConverter{}", type_.canonical_name())
+            }
+            // Wrapper types are implemented by generics that wrap the FfiConverter implementation of the
+            // inner type.
+            Type::Optional(inner) => {
+                format!("std::option::Option<{}>", ffi_converter_name(inner)?)
+            }
+            Type::Sequence(inner) => format!("std::vec::Vec<{}>", ffi_converter_name(inner)?),
+            Type::Map(k, v) => format!(
+                "std::collections::HashMap<{}, {}>",
+                ffi_converter_name(k)?,
+                ffi_converter_name(v)?
+            ),
+            // External and Wrapped bytes have FfiConverters with a predictable name based on the type name.
+            Type::Custom { name, .. } | Type::External { name, .. } => {
+                format!("FfiConverterType{}", name)
+            }
+            // Primitive types / strings are implemented by their rust type
+            Type::Int8 => "i8".into(),
+            Type::UInt8 => "u8".into(),
+            Type::Int16 => "i16".into(),
+            Type::UInt16 => "u16".into(),
+            Type::Int32 => "i32".into(),
+            Type::UInt32 => "u32".into(),
+            Type::Int64 => "i64".into(),
+            Type::UInt64 => "u64".into(),
+            Type::Float32 => "f32".into(),
+            Type::Float64 => "f64".into(),
+            Type::String => "String".into(),
+            Type::Boolean => "bool".into(),
+            Type::Unresolved { .. } => {
+                unreachable!("UDL scaffolding code never contains unresolved types")
+            }
+        })
+    }
+
+    // Map a type to Rust code that specifies the FfiConverter implementation.
+    //
+    // This outputs something like `<TheFfiConverterStruct as FfiConverter>`
+    pub fn ffi_converter(type_: &Type) -> Result<String, askama::Error> {
+        Ok(format!(
+            "<{} as uniffi::FfiConverter>",
+            ffi_converter_name(type_)?
+        ))
+    }
+
+    // Turns a `crate-name` into the `crate_name` the .rs code needs to specify.
+    pub fn crate_name_rs(nm: &str) -> Result<String, askama::Error> {
+        Ok(nm.to_string().to_snake_case())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/CallbackInterfaceTemplate.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/CallbackInterfaceTemplate.rs
new file mode 100644
index 0000000000..166da0d994
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/CallbackInterfaceTemplate.rs
@@ -0,0 +1,186 @@
+{#
+// For each Callback Interface definition, we assume that there is a corresponding trait defined in Rust client code.
+// If the UDL callback interface and Rust trait's methods don't match, the Rust compiler will complain.
+// We generate:
+//  * an init function to accept that `ForeignCallback` from the foreign language, and stores it.
+//  * a holder for a `ForeignCallback`, of type `uniffi::ForeignCallbackInternals`.
+//  * a proxy `struct` which implements the `trait` that the Callback Interface corresponds to. This
+//    is the object that client code interacts with.
+//    - for each method, arguments will be packed into a `RustBuffer` and sent over the `ForeignCallback` to be
+//      unpacked and called. The return value is packed into another `RustBuffer` and sent back to Rust.
+//    - a `Drop` `impl`, which tells the foreign language to forget about the real callback object.
+#}
+{% let trait_name = cbi.name() -%}
+{% let trait_impl = cbi.type_().borrow()|ffi_converter_name -%}
+{% let foreign_callback_internals = format!("foreign_callback_{}_internals", trait_name)|upper -%}
+
+// Register a foreign callback for getting across the FFI.
+#[doc(hidden)]
+static {{ foreign_callback_internals }}: uniffi::ForeignCallbackInternals = uniffi::ForeignCallbackInternals::new();
+
+#[doc(hidden)]
+#[no_mangle]
+pub extern "C" fn {{ cbi.ffi_init_callback().name() }}(callback: uniffi::ForeignCallback, _: &mut uniffi::RustCallStatus) {
+    {{ foreign_callback_internals }}.set_callback(callback);
+    // The call status should be initialized to CALL_SUCCESS, so no need to modify it.
+}
+
+// Make an implementation which will shell out to the foreign language.
+#[doc(hidden)]
+#[derive(Debug)]
+struct {{ trait_impl }} {
+  handle: u64
+}
+
+impl Drop for {{ trait_impl }} {
+    fn drop(&mut self) {
+        let callback = {{ foreign_callback_internals }}.get_callback().unwrap();
+        let mut rbuf = uniffi::RustBuffer::new();
+        unsafe { callback(self.handle, uniffi::IDX_CALLBACK_FREE, Default::default(), &mut rbuf) };
+    }
+}
+
+uniffi::deps::static_assertions::assert_impl_all!({{ trait_impl }}: Send);
+
+impl r#{{ trait_name }} for {{ trait_impl }} {
+    {%- for meth in cbi.methods() %}
+
+    {#- Method declaration #}
+    fn r#{{ meth.name() -}}
+    ({% call rs::arg_list_decl_with_prefix("&self", meth) %})
+    {%- match (meth.return_type(), meth.throws_type()) %}
+    {%- when (Some(return_type), None) %} -> {{ return_type.borrow()|type_rs }}
+    {%- when (Some(return_type), Some(err)) %} -> ::std::result::Result<{{ return_type.borrow()|type_rs }}, {{ err|type_rs }}>
+    {%- when (None, Some(err)) %} -> ::std::result::Result<(), {{ err|type_rs }}>
+    {% else -%}
+    {%- endmatch -%} {
+    {#- Method body #}
+        uniffi::deps::log::debug!("{{ cbi.name() }}.{{ meth.name() }}");
+
+    {#- Packing args into a RustBuffer #}
+        {% if meth.arguments().len() == 0 -%}
+        let args_buf = Vec::new();
+        {% else -%}
+        let mut args_buf = Vec::new();
+        {% endif -%}
+        {%- for arg in meth.arguments() %}
+        {{ arg.type_().borrow()|ffi_converter }}::write(r#{{ arg.name() }}, &mut args_buf);
+        {%- endfor -%}
+        let args_rbuf = uniffi::RustBuffer::from_vec(args_buf);
+
+    {#- Calling into foreign code. #}
+        let callback = {{ foreign_callback_internals }}.get_callback().unwrap();
+
+        unsafe {
+            // SAFETY:
+            // * We're passing in a pointer to an empty buffer.
+            //   * Nothing allocated, so nothing to drop.
+            // * We expect the callback to write into that a valid allocated instance of a
+            //   RustBuffer.
+            let mut ret_rbuf = uniffi::RustBuffer::new();
+            let ret = callback(self.handle, {{ loop.index }}, args_rbuf, &mut ret_rbuf);
+            #[allow(clippy::let_and_return, clippy::let_unit_value)]
+            match ret {
+                1 => {
+                    // 1 indicates success with the return value written to the RustBuffer for
+                    //   non-void calls.
+                    let result = {
+                        {% match meth.return_type() -%}
+                        {%- when Some(return_type) -%}
+                        let vec = ret_rbuf.destroy_into_vec();
+                        let mut ret_buf = vec.as_slice();
+                        {{ return_type|ffi_converter }}::try_read(&mut ret_buf).unwrap()
+                        {%- else %}
+                        uniffi::RustBuffer::destroy(ret_rbuf);
+                        {%- endmatch %}
+                    };
+                    {%- if meth.throws() %}
+                    Ok(result)
+                    {%- else %}
+                    result
+                    {%- endif %}
+                }
+                -2 => {
+                    // -2 indicates an error written to the RustBuffer
+                    {% match meth.throws_type() -%}
+                    {% when Some(error_type) -%}
+                    let vec = ret_rbuf.destroy_into_vec();
+                    let mut ret_buf = vec.as_slice();
+                    Err({{ error_type|ffi_converter }}::try_read(&mut ret_buf).unwrap())
+                    {%- else -%}
+                    panic!("Callback return -2, but throws_type() is None");
+                    {%- endmatch %}
+                }
+                // 0 is a deprecated method to indicates success for void returns
+                0 => {
+                    eprintln!("UniFFI: Callback interface returned 0.  Please update the bindings code to return 1 for all successfull calls");
+                    {% match (meth.return_type(), meth.throws()) %}
+                    {% when (Some(_), _) %}
+                    panic!("Callback returned 0 when we were expecting a return value");
+                    {% when (None, false) %}
+                    {% when (None, true) %}
+                    Ok(())
+                    {%- endmatch %}
+                }
+                // -1 indicates an unexpected error
+                {% match meth.throws_type() %}
+                {%- when Some(error_type) -%}
+                -1 => {
+                    let reason = if !ret_rbuf.is_empty() {
+                        match {{ Type::String.borrow()|ffi_converter }}::try_lift(ret_rbuf) {
+                            Ok(s) => s,
+                            Err(e) => {
+                                println!("{{ trait_name }} Error reading ret_buf: {e}");
+                                String::from("[Error reading reason]")
+                            }
+                        }
+                    } else {
+                        uniffi::RustBuffer::destroy(ret_rbuf);
+                        String::from("[Unknown Reason]")
+                    };
+                    let e: {{ error_type|type_rs }} = uniffi::UnexpectedUniFFICallbackError::from_reason(reason).into();
+                    Err(e)
+                }
+                {%- else %}
+                -1 => panic!("Callback failed"),
+                {%- endmatch %}
+                // Other values should never be returned
+                _ => panic!("Callback failed with unexpected return code"),
+            }
+        }
+    }
+    {%- endfor %}
+}
+
+unsafe impl uniffi::FfiConverter for {{ trait_impl }} {
+    // This RustType allows for rust code that inputs this type as a Box<dyn CallbackInterfaceTrait> param
+    type RustType = Box<dyn r#{{ trait_name }}>;
+    type FfiType = u64;
+
+    // Lower and write are tricky to implement because we have a dyn trait as our type.  There's
+    // probably a way to, but this carries lots of thread safety risks, down to impedence
+    // mismatches between Rust and foreign languages, and our uncertainty around implementations of
+    // concurrent handlemaps.
+    //
+    // The use case for them is also quite exotic: it's passing a foreign callback back to the foreign
+    // language.
+    //
+    // Until we have some certainty, and use cases, we shouldn't use them.
+    fn lower(_obj: Self::RustType) -> Self::FfiType {
+        panic!("Lowering CallbackInterface not supported")
+    }
+
+    fn write(_obj: Self::RustType, _buf: &mut std::vec::Vec<u8>) {
+        panic!("Writing CallbackInterface not supported")
+    }
+
+    fn try_lift(v: Self::FfiType) -> uniffi::deps::anyhow::Result<Self::RustType> {
+        Ok(Box::new(Self { handle: v }))
+    }
+
+    fn try_read(buf: &mut &[u8]) -> uniffi::deps::anyhow::Result<Self::RustType> {
+        use uniffi::deps::bytes::Buf;
+        uniffi::check_remaining(buf, 8)?;
+        <Self as uniffi::FfiConverter>::try_lift(buf.get_u64())
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/EnumTemplate.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/EnumTemplate.rs
new file mode 100644
index 0000000000..0d83a99b90
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/EnumTemplate.rs
@@ -0,0 +1,45 @@
+{#
+// For each enum declared in the UDL, we assume the caller has provided a corresponding
+// rust `enum`. We provide the traits for sending it across the FFI, which will fail to
+// compile if the provided struct has a different shape to the one declared in the UDL.
+//
+// We define a unit-struct to implement the trait to sidestep Rust's orphan rule (ADR-0006). It's
+// public so other crates can refer to it via an `[External='crate'] typedef`
+#}
+
+#[doc(hidden)]
+pub struct {{ e.type_().borrow()|ffi_converter_name }};
+
+#[doc(hidden)]
+impl uniffi::RustBufferFfiConverter for {{ e.type_().borrow()|ffi_converter_name }} {
+    type RustType = r#{{ e.name() }};
+
+    fn write(obj: Self::RustType, buf: &mut std::vec::Vec<u8>) {
+        use uniffi::deps::bytes::BufMut;
+        match obj {
+            {%- for variant in e.variants() %}
+            r#{{ e.name() }}::r#{{ variant.name() }} { {% for field in variant.fields() %}r#{{ field.name() }}, {%- endfor %} } => {
+                buf.put_i32({{ loop.index }});
+                {% for field in variant.fields() -%}
+                {{ field.type_().borrow()|ffi_converter }}::write(r#{{ field.name() }}, buf);
+                {%- endfor %}
+            },
+            {%- endfor %}
+        };
+    }
+
+    fn try_read(buf: &mut &[u8]) -> uniffi::deps::anyhow::Result<r#{{ e.name() }}> {
+        use uniffi::deps::bytes::Buf;
+        uniffi::check_remaining(buf, 4)?;
+        Ok(match buf.get_i32() {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} => r#{{ e.name() }}::r#{{ variant.name() }}{% if variant.has_fields() %} {
+                {% for field in variant.fields() %}
+                r#{{ field.name() }}: {{ field.type_().borrow()|ffi_converter }}::try_read(buf)?,
+                {%- endfor %}
+            }{% endif %},
+            {%- endfor %}
+            v => uniffi::deps::anyhow::bail!("Invalid {{ e.name() }} enum value: {}", v),
+        })
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ErrorTemplate.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ErrorTemplate.rs
new file mode 100644
index 0000000000..7ca1d104fe
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ErrorTemplate.rs
@@ -0,0 +1,95 @@
+{#
+// For each error declared in the UDL, we assume the caller has provided a corresponding
+// rust `enum`. We provide the traits for sending it across the FFI, which will fail to
+// compile if the provided struct has a different shape to the one declared in the UDL.
+//
+// We define a unit-struct to implement the trait to sidestep Rust's orphan rule (ADR-0006). It's
+// public so other crates can refer to it via an `[External='crate'] typedef`
+#}
+
+#[doc(hidden)]
+pub struct {{ e.type_().borrow()|ffi_converter_name }};
+
+#[doc(hidden)]
+impl uniffi::RustBufferFfiConverter for {{ e.type_().borrow()|ffi_converter_name }} {
+    type RustType = r#{{ e.name() }};
+
+    {% if e.is_flat() %}
+
+    // For "flat" error enums, we stringify the error on the Rust side and surface that
+    // as the error message in the foreign language.
+
+
+    fn write(obj: r#{{ e.name() }}, buf: &mut std::vec::Vec<u8>) {
+        use uniffi::deps::bytes::BufMut;
+        let msg = obj.to_string();
+        match obj {
+            {%- for variant in e.variants() %}
+            r#{{ e.name() }}::r#{{ variant.name() }}{..} => {
+                buf.put_i32({{ loop.index }});
+                <String as uniffi::FfiConverter>::write(msg, buf);
+            },
+            {%- endfor %}
+        };
+    }
+
+    {%- if ci.should_generate_error_read(e) %}
+    fn try_read(buf: &mut &[u8]) -> uniffi::deps::anyhow::Result<r#{{ e.name() }}> {
+        use uniffi::deps::bytes::Buf;
+        uniffi::check_remaining(buf, 4)?;
+        Ok(match buf.get_i32() {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} => r#{{ e.name() }}::r#{{ variant.name() }}{ },
+            {%- endfor %}
+            v => uniffi::deps::anyhow::bail!("Invalid {{ e.name() }} enum value: {}", v),
+        })
+    }
+    {%- else %}
+    fn try_read(_buf: &mut &[u8]) -> uniffi::deps::anyhow::Result<r#{{ e.name() }}> {
+        panic!("try_read not supported for flat errors");
+    }
+    {%- endif %}
+
+    {% else %}
+
+    // For rich structured enums, we map individual fields on the Rust side over to
+    // corresponding fields on the foreign-language side.
+    //
+    // If a variant doesn't have fields defined in the UDL, it's currently still possible that
+    // the Rust enum has fields and they're just not listed. In that case we use the `Variant{..}`
+    // syntax to match the variant while ignoring its fields.
+
+    fn write(obj: r#{{ e.name() }}, buf: &mut std::vec::Vec<u8>) {
+        use uniffi::deps::bytes::BufMut;
+        match obj {
+            {%- for variant in e.variants() %}
+            r#{{ e.name() }}::r#{{ variant.name() }}{% if variant.has_fields() %} { {% for field in variant.fields() %}r#{{ field.name() }}, {%- endfor %} }{% else %}{..}{% endif %} => {
+                buf.put_i32({{ loop.index }});
+                {% for field in variant.fields() -%}
+                {{ field.type_().borrow()|ffi_converter }}::write(r#{{ field.name() }}, buf);
+                {%- endfor %}
+            },
+            {%- endfor %}
+        };
+    }
+
+    fn try_read(buf: &mut &[u8]) -> uniffi::deps::anyhow::Result<r#{{ e.name() }}> {
+        // Note: no need to call should_generate_error_read here, since it is always true for
+        // non-flat errors
+        use uniffi::deps::bytes::Buf;
+        uniffi::check_remaining(buf, 4)?;
+        Ok(match buf.get_i32() {
+            {%- for variant in e.variants() %}
+            {{ loop.index }} => r#{{ e.name() }}::r#{{ variant.name() }}{% if variant.has_fields() %} {
+                {% for field in variant.fields() %}
+                r#{{ field.name() }}: {{ field.type_().borrow()|ffi_converter }}::try_read(buf)?,
+                {%- endfor %}
+            }{% endif %},
+            {%- endfor %}
+            v => uniffi::deps::anyhow::bail!("Invalid {{ e.name() }} enum value: {}", v),
+        })
+    }
+    {% endif %}
+}
+
+impl uniffi::FfiError for {{ e.type_().borrow()|ffi_converter_name }} { }
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ExternalTypesTemplate.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ExternalTypesTemplate.rs
new file mode 100644
index 0000000000..078c4e2462
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ExternalTypesTemplate.rs
@@ -0,0 +1,48 @@
+// Support for external types.
+
+// Types with an external `FfiConverter`...
+{% for (name, crate_name) in ci.iter_external_types() %}
+// `{{ name }}` is defined in `{{ crate_name }}`
+use {{ crate_name|crate_name_rs }}::FfiConverterType{{ name }};
+{% endfor %}
+
+// For custom scaffolding types we need to generate an FfiConverterType based on the
+// UniffiCustomTypeConverter implementation that the library supplies
+{% for (name, builtin) in ci.iter_custom_types() %}
+{% if loop.first %}
+
+// A trait that's in our crate for our external wrapped types to implement.
+trait UniffiCustomTypeConverter {
+    type Builtin;
+
+    fn into_custom(val: Self::Builtin) -> uniffi::Result<Self> where Self: Sized;
+    fn from_custom(obj: Self) -> Self::Builtin;
+}
+
+{%- endif -%}
+
+// Type `{{ name }}` wraps a `{{ builtin.canonical_name() }}`
+#[doc(hidden)]
+pub struct FfiConverterType{{ name }};
+
+unsafe impl uniffi::FfiConverter for FfiConverterType{{ name }} {
+    type RustType = r#{{ name }};
+    type FfiType = {{ FFIType::from(builtin).borrow()|type_ffi }};
+
+    fn lower(obj: {{ name }} ) -> Self::FfiType {
+        <{{ builtin|type_rs }} as uniffi::FfiConverter>::lower(<{{ name }} as UniffiCustomTypeConverter>::from_custom(obj))
+    }
+
+    fn try_lift(v: Self::FfiType) -> uniffi::Result<{{ name }}> {
+        <r#{{ name }} as UniffiCustomTypeConverter>::into_custom(<{{ builtin|type_rs }} as uniffi::FfiConverter>::try_lift(v)?)
+    }
+
+    fn write(obj: {{ name }}, buf: &mut Vec<u8>) {
+        <{{ builtin|type_rs }} as uniffi::FfiConverter>::write(<{{ name }} as UniffiCustomTypeConverter>::from_custom(obj), buf);
+    }
+
+    fn try_read(buf: &mut &[u8]) -> uniffi::Result<r#{{ name }}> {
+        <{{ name }} as UniffiCustomTypeConverter>::into_custom(<{{ builtin|type_rs }} as uniffi::FfiConverter>::try_read(buf)?)
+    }
+}
+{%- endfor -%}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ObjectTemplate.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ObjectTemplate.rs
new file mode 100644
index 0000000000..3834ad994e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ObjectTemplate.rs
@@ -0,0 +1,73 @@
+// For each Object definition, we assume the caller has provided an appropriately-shaped `struct T`
+// with an `impl` for each method on the object. We create an `Arc<T>` for "safely" handing out
+// references to these structs to foreign language code, and we provide a `pub extern "C"` function
+// corresponding to each method.
+//
+// (Note that "safely" is in "scare quotes" - that's because we use functions on an `Arc` that
+// that are inherently unsafe, but the code we generate is safe in practice.)
+//
+// If the caller's implementation of the struct does not match with the methods or types specified
+// in the UDL, then the rust compiler will complain with a (hopefully at least somewhat helpful!)
+// error message when processing this generated code.
+
+{% if obj.uses_deprecated_threadsafe_attribute() %}
+// We want to mark this as `deprecated` - long story short, the only way to
+// sanely do this using `#[deprecated(..)]` is to generate a function with that
+// attribute, then generate call to that function in the object constructors.
+#[deprecated(
+    since = "0.11.0",
+    note = "The `[Threadsafe]` attribute on interfaces is now the default and its use is deprecated - you should upgrade \
+            `{{ obj.name() }}` to remove the `[ThreadSafe]` attribute. \
+            See https://github.com/mozilla/uniffi-rs/#thread-safety for more details"
+)]
+#[allow(non_snake_case)]
+fn uniffi_note_threadsafe_deprecation_{{ obj.name() }}() {}
+{% endif %}
+
+
+// All Object structs must be `Sync + Send`. The generated scaffolding will fail to compile
+// if they are not, but unfortunately it fails with an unactionably obscure error message.
+// By asserting the requirement explicitly, we help Rust produce a more scrutable error message
+// and thus help the user debug why the requirement isn't being met.
+uniffi::deps::static_assertions::assert_impl_all!(r#{{ obj.name() }}: Sync, Send);
+
+{% let ffi_free = obj.ffi_object_free() -%}
+#[doc(hidden)]
+#[no_mangle]
+pub extern "C" fn {{ ffi_free.name() }}(ptr: *const std::os::raw::c_void, call_status: &mut uniffi::RustCallStatus) {
+    uniffi::call_with_output(call_status, || {
+        assert!(!ptr.is_null());
+        {#- turn it into an Arc and explicitly drop it. #}
+        drop(unsafe { std::sync::Arc::from_raw(ptr as *const r#{{ obj.name() }}) })
+    })
+}
+
+{%- for cons in obj.constructors() %}
+    #[doc(hidden)]
+    #[no_mangle]
+    pub extern "C" fn r#{{ cons.ffi_func().name() }}(
+        {%- call rs::arg_list_ffi_decl(cons.ffi_func()) %}) -> *const std::os::raw::c_void /* *const {{ obj.name() }} */ {
+        uniffi::deps::log::debug!("{{ cons.ffi_func().name() }}");
+        {% if obj.uses_deprecated_threadsafe_attribute() %}
+        uniffi_note_threadsafe_deprecation_{{ obj.name() }}();
+        {% endif %}
+
+        // If the constructor does not have the same signature as declared in the UDL, then
+        // this attempt to call it will fail with a (somewhat) helpful compiler error.
+        {% call rs::to_rs_constructor_call(obj, cons) %}
+    }
+{%- endfor %}
+
+{%- for meth in obj.methods() %}
+    #[doc(hidden)]
+    #[no_mangle]
+    #[allow(clippy::let_unit_value)] // Sometimes we generate code that binds `_retval` to `()`.
+    pub extern "C" fn r#{{ meth.ffi_func().name() }}(
+        {%- call rs::arg_list_ffi_decl(meth.ffi_func()) %}
+    ) {% call rs::return_signature(meth) %} {
+        uniffi::deps::log::debug!("{{ meth.ffi_func().name() }}");
+        // If the method does not have the same signature as declared in the UDL, then
+        // this attempt to call it will fail with a (somewhat) helpful compiler error.
+        {% call rs::to_rs_method_call(obj, meth) %}
+    }
+{% endfor %}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/RecordTemplate.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/RecordTemplate.rs
new file mode 100644
index 0000000000..6ec85ed036
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/RecordTemplate.rs
@@ -0,0 +1,33 @@
+{#
+// For each record declared in the UDL, we assume the caller has provided a corresponding
+// rust `struct` with the declared fields. We provide the traits for sending it across the FFI.
+// If the caller's struct does not match the shape and types declared in the UDL then the rust
+// compiler will complain with a type error.
+//
+// We define a unit-struct to implement the trait to sidestep Rust's orphan rule (ADR-0006). It's
+// public so other crates can refer to it via an `[External='crate'] typedef`
+#}
+
+#[doc(hidden)]
+pub struct {{ rec.type_().borrow()|ffi_converter_name }};
+
+#[doc(hidden)]
+impl uniffi::RustBufferFfiConverter for {{ rec.type_().borrow()|ffi_converter_name }} {
+    type RustType = r#{{ rec.name() }};
+
+    fn write(obj: r#{{ rec.name() }}, buf: &mut std::vec::Vec<u8>) {
+        // If the provided struct doesn't match the fields declared in the UDL, then
+        // the generated code here will fail to compile with somewhat helpful error.
+        {%- for field in rec.fields() %}
+        {{ field.type_().borrow()|ffi_converter }}::write(obj.r#{{ field.name() }}, buf);
+        {%- endfor %}
+    }
+
+    fn try_read(buf: &mut &[u8]) -> uniffi::deps::anyhow::Result<r#{{ rec.name() }}> {
+        Ok(r#{{ rec.name() }} {
+            {%- for field in rec.fields() %}
+                r#{{ field.name() }}: {{ field.type_().borrow()|ffi_converter }}::try_read(buf)?,
+            {%- endfor %}
+        })
+    }
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ReexportUniFFIScaffolding.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ReexportUniFFIScaffolding.rs
new file mode 100644
index 0000000000..668f1a2e63
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/ReexportUniFFIScaffolding.rs
@@ -0,0 +1,27 @@
+// Code to re-export the UniFFI scaffolding functions.
+//
+// Rust won't always re-export the functions from dependencies
+// ([rust-lang#50007](https://github.com/rust-lang/rust/issues/50007))
+//
+// A workaround for this is to have the dependent crate reference a function from its dependency in
+// an extern "C" function. This is clearly hacky and brittle, but at least we have some unittests
+// that check if this works (fixtures/reexport-scaffolding-macro).
+//
+// The main way we use this macro is for that contain multiple UniFFI components (libxul,
+// megazord).  The combined library has a cargo dependency for each component and calls
+// uniffi_reexport_scaffolding!() for each one.
+
+#[doc(hidden)]
+pub fn uniffi_reexport_hack() {
+}
+
+#[macro_export]
+macro_rules! uniffi_reexport_scaffolding {
+    () => {
+        #[doc(hidden)]
+        #[no_mangle]
+        pub extern "C" fn {{ ci.namespace() }}_uniffi_reexport_hack() {
+            $crate::uniffi_reexport_hack()
+        }
+    };
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/RustBuffer.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/RustBuffer.rs
new file mode 100644
index 0000000000..39d3f32dcc
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/RustBuffer.rs
@@ -0,0 +1,27 @@
+// Everybody gets basic buffer support, since it's needed for passing complex types over the FFI.
+//
+// See `uniffi/src/ffi/rustbuffer.rs` for documentation on these functions
+
+#[allow(clippy::missing_safety_doc)]
+#[no_mangle]
+pub extern "C" fn {{ ci.ffi_rustbuffer_alloc().name() }}(size: i32, call_status: &mut uniffi::RustCallStatus) -> uniffi::RustBuffer {
+    uniffi::ffi::uniffi_rustbuffer_alloc(size, call_status)
+}
+
+#[allow(clippy::missing_safety_doc)]
+#[no_mangle]
+pub unsafe extern "C" fn {{ ci.ffi_rustbuffer_from_bytes().name() }}(bytes: uniffi::ForeignBytes, call_status: &mut uniffi::RustCallStatus) -> uniffi::RustBuffer {
+    uniffi::ffi::uniffi_rustbuffer_from_bytes(bytes, call_status)
+}
+
+#[allow(clippy::missing_safety_doc)]
+#[no_mangle]
+pub unsafe extern "C" fn {{ ci.ffi_rustbuffer_free().name() }}(buf: uniffi::RustBuffer, call_status: &mut uniffi::RustCallStatus) {
+    uniffi::ffi::uniffi_rustbuffer_free(buf, call_status)
+}
+
+#[allow(clippy::missing_safety_doc)]
+#[no_mangle]
+pub unsafe extern "C" fn {{ ci.ffi_rustbuffer_reserve().name() }}(buf: uniffi::RustBuffer, additional: i32, call_status: &mut uniffi::RustCallStatus) -> uniffi::RustBuffer {
+    uniffi::ffi::uniffi_rustbuffer_reserve(buf, additional, call_status)
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/TopLevelFunctionTemplate.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/TopLevelFunctionTemplate.rs
new file mode 100644
index 0000000000..0c6d5a47de
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/TopLevelFunctionTemplate.rs
@@ -0,0 +1,17 @@
+{#
+// For each top-level function declared in the UDL, we assume the caller has provided a corresponding
+// rust function of the same name. We provide a `pub extern "C"` wrapper that does type conversions to
+// send data across the FFI, which will fail to compile if the provided function does not match what's
+// specified in the UDL.    
+#}
+#[doc(hidden)]
+#[no_mangle]
+#[allow(clippy::let_unit_value)] // Sometimes we generate code that binds `_retval` to `()`.
+pub extern "C" fn r#{{ func.ffi_func().name() }}(
+    {% call rs::arg_list_ffi_decl(func.ffi_func()) %}
+) {% call rs::return_signature(func) %} {
+    // If the provided function does not match the signature specified in the UDL
+    // then this attempt to call it will not compile, and will give guidance as to why.
+    uniffi::deps::log::debug!("{{ func.ffi_func().name() }}");
+    {% call rs::to_rs_function_call(func) %}
+}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/macros.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/macros.rs
new file mode 100644
index 0000000000..22ee543b3e
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/macros.rs
@@ -0,0 +1,118 @@
+{#
+// Template to receive calls into rust.
+#}
+
+{%- macro to_rs_call(func) -%}
+r#{{ func.name() }}({% call _arg_list_rs_call(func) -%})
+{%- endmacro -%}
+
+{%- macro _arg_list_rs_call(func) %}
+    {%- for arg in func.full_arguments() %}
+        match {{- arg.type_().borrow()|ffi_converter }}::try_lift(r#{{ arg.name() }}) {
+        {%- if arg.by_ref() %}
+            Ok(ref val) => val,
+        {% else %}
+            Ok(val) => val,
+        {% endif %}
+
+        {# If this function returns an error, we attempt to downcast errors doing arg
+            conversions to this error. If the downcast fails or the function doesn't
+            return an error, we just panic.
+        #}
+        {%- match func.throws_type() -%}
+        {%- when Some with (e) %}
+            Err(err) => return Err(uniffi::lower_anyhow_error_or_panic::<{{ e|ffi_converter_name }}>(err, "{{ arg.name() }}")),
+        {%- else %}
+            Err(err) => panic!("Failed to convert arg '{}': {}", "{{ arg.name() }}", err),
+        {%- endmatch %}
+        }
+        {%- if !loop.last %}, {% endif %}
+    {%- endfor %}
+{%- endmacro -%}
+
+{#-
+// Arglist as used in the _UniFFILib function declations.
+// Note unfiltered name but type_ffi filters.
+-#}
+{%- macro arg_list_ffi_decl(func) %}
+    {%- for arg in func.arguments() %}
+        r#{{- arg.name() }}: {{ arg.type_().borrow()|type_ffi -}},
+    {%- endfor %}
+    call_status: &mut uniffi::RustCallStatus
+{%- endmacro -%}
+
+{%- macro arg_list_decl_with_prefix(prefix, meth) %}
+    {{- prefix -}}
+    {%- if meth.arguments().len() > 0 %}, {# whitespace #}
+        {%- for arg in meth.arguments() %}
+            r#{{- arg.name() }}: {{ arg.type_().borrow()|type_rs -}}{% if loop.last %}{% else %},{% endif %}
+        {%- endfor %}
+    {%- endif %}
+{%- endmacro -%}
+
+{% macro return_signature(func) %}{% match func.ffi_func().return_type() %}{% when Some with (return_type) %} -> {% call return_type_func(func) %}{%- else -%}{%- endmatch -%}{%- endmacro -%}
+
+{% macro return_type_func(func) %}{% match func.ffi_func().return_type() %}{% when Some with (return_type) %}{{ return_type|type_ffi }}{%- else -%}(){%- endmatch -%}{%- endmacro -%}
+
+{% macro ret(func) %}{% match func.return_type() %}{% when Some with (return_type) %}{{ return_type|ffi_converter }}::lower(_retval){% else %}_retval{% endmatch %}{% endmacro %}
+
+{% macro construct(obj, cons) %}
+    r#{{- obj.name() }}::{% call to_rs_call(cons) -%}
+{% endmacro %}
+
+{% macro to_rs_constructor_call(obj, cons) %}
+{% match cons.throws_type() %}
+{% when Some with (e) %}
+    uniffi::call_with_result(call_status, || {
+        let _new = {% call construct(obj, cons) %}.map_err(Into::into).map_err({{ e|ffi_converter }}::lower)?;
+        let _arc = std::sync::Arc::new(_new);
+        Ok({{ obj.type_().borrow()|ffi_converter }}::lower(_arc))
+    })
+{% else %}
+    uniffi::call_with_output(call_status, || {
+        let _new = {% call construct(obj, cons) %};
+        let _arc = std::sync::Arc::new(_new);
+        {{ obj.type_().borrow()|ffi_converter }}::lower(_arc)
+    })
+{% endmatch %}
+{% endmacro %}
+
+{% macro to_rs_method_call(obj, meth) -%}
+{% match meth.throws_type() -%}
+{% when Some with (e) -%}
+uniffi::call_with_result(call_status, || {
+    let _retval =  r#{{ obj.name() }}::{% call to_rs_call(meth) %}.map_err(Into::into).map_err({{ e|ffi_converter }}::lower)?;
+    Ok({% call ret(meth) %})
+})
+{% else %}
+uniffi::call_with_output(call_status, || {
+    {% match meth.return_type() -%}
+    {% when Some with (return_type) -%}
+    let retval = r#{{ obj.name() }}::{% call to_rs_call(meth) %};
+    {{ return_type|ffi_converter }}::lower(retval)
+    {% else -%}
+    r#{{ obj.name() }}::{% call to_rs_call(meth) %}
+    {% endmatch -%}
+})
+{% endmatch -%}
+{% endmacro -%}
+
+{% macro to_rs_function_call(func) %}
+{% match func.throws_type() %}
+{% when Some with (e) %}
+uniffi::call_with_result(call_status, || {
+    let _retval = {% call to_rs_call(func) %}.map_err(Into::into).map_err({{ e|ffi_converter }}::lower)?;
+    Ok({% call ret(func) %})
+})
+{% else %}
+uniffi::call_with_output(call_status, || {
+    {% match func.return_type() -%}
+    {% when Some with (return_type) -%}
+    {{ return_type|ffi_converter }}::lower({% call to_rs_call(func) %})
+    {% else -%}
+    {% if func.full_arguments().is_empty() %}#[allow(clippy::redundant_closure)]{% endif %}
+    {% call to_rs_call(func) %}
+    {% endmatch -%}
+})
+{% endmatch %}
+{% endmacro %}
diff --git a/third_party/rust/uniffi_bindgen/src/scaffolding/templates/scaffolding_template.rs b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/scaffolding_template.rs
new file mode 100644
index 0000000000..11b6507e29
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/scaffolding/templates/scaffolding_template.rs
@@ -0,0 +1,58 @@
+// This file was autogenerated by some hot garbage in the `uniffi` crate.
+// Trust me, you don't want to mess with it!
+{% import "macros.rs" as rs %}
+
+// Check for compatibility between `uniffi` and `uniffi_bindgen` versions.
+// Note that we have an error message on the same line as the assertion.
+// This is important, because if the assertion fails, the compiler only
+// seems to show that single line as context for the user.
+uniffi::assert_compatible_version!("{{ uniffi_version }}"); // Please check that you depend on version {{ uniffi_version }} of the `uniffi` crate.
+
+{% for ty in ci.iter_types() %}
+{%- match ty %}
+{%- when Type::Map with (k, v) -%}
+{# Next comment MUST be after the line to be in the compiler output #}
+uniffi::deps::static_assertions::assert_impl_all!({{ k|type_rs }}: ::std::cmp::Eq, ::std::hash::Hash); // record<{{ k|type_rs }}, {{ v|type_rs }}>
+{%- else %}
+{%- endmatch %}
+{% endfor %}
+
+{% include "RustBuffer.rs" %}
+
+// Error definitions, corresponding to `error` in the UDL.
+{% for e in ci.error_definitions() %}
+{% include "ErrorTemplate.rs" %}
+{% endfor %}
+
+// Enum defitions, corresponding to `enum` in UDL.
+{% for e in ci.enum_definitions() %}
+{% include "EnumTemplate.rs" %}
+{% endfor %}
+
+// Record definitions, implemented as method-less structs, corresponding to `dictionary` objects.
+{% for rec in ci.record_definitions() %}
+{% include "RecordTemplate.rs" %}
+{% endfor %}
+
+// Top level functions, corresponding to UDL `namespace` functions.
+{%- for func in ci.function_definitions() %}
+{% include "TopLevelFunctionTemplate.rs" %}
+{% endfor -%}
+
+// Object definitions, corresponding to UDL `interface` definitions.
+{% for obj in ci.object_definitions() %}
+{% include "ObjectTemplate.rs" %}
+{% endfor %}
+
+// Callback Interface definitions, corresponding to UDL `callback interface` definitions.
+{% for cbi in ci.callback_interface_definitions() %}
+{% include "CallbackInterfaceTemplate.rs" %}
+{% endfor %}
+
+// External and Wrapped types
+{% include "ExternalTypesTemplate.rs" %}
+
+// The `reexport_uniffi_scaffolding` macro
+{% include "ReexportUniFFIScaffolding.rs" %}
+
+{%- import "macros.rs" as rs -%}