Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

20 files changed, 1562 insertions, 0 deletions

diff --git a/third_party/rust/proc-macro-hack/.cargo-checksum.json b/third_party/rust/proc-macro-hack/.cargo-checksum.json
new file mode 100644
index 0000000000..135de5575c
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"Cargo.toml":"1833d37aad8fa07e58d16c840b2815da2114c6d92d3625de45baa66b986a68cc","LICENSE-APACHE":"a60eea817514531668d7e00765731449fe14d059d3249e0bc93b36de45f759f2","LICENSE-MIT":"d59d2723bbc1627b629429a9c779d5dcfde579c9723e6ded1052931c4e8efa0a","README.md":"ca7e8118aeda26c39cbeaeb0a4cbf5d44bdf17eedc89abbff5d307e4abffdf33","build.rs":"eae956d2a2de606f0c26741fbc849f3c9db89bf14f743d76a452b85c7904860c","src/error.rs":"d31547fe853819b03cf1a485827ceaa7ebffbd45a8d5ef066e94cc862f499583","src/iter.rs":"8d4b817b9abc4e817105b673e15f29ef9bb8284a010ce01ac2d83387fe136947","src/lib.rs":"4b966fffe1e74857e902f0417bfc6f59d063f48f24bc12f0fec3d35e9882365f","src/parse.rs":"53f45dff0aa345644e6cf56619704d413ed732d30f353b966cbf39dd0c00e093","src/quote.rs":"2f8c5ff5174f8869f4fd317156396be6d90b0af566f44840a2cadb2d1180fb45","tests/compiletest.rs":"0a52a44786aea1c299c695bf948b2ed2081e4cc344e5c2cadceab4eb03d0010d","tests/ui/private.rs":"f58d9fafe29bb624cbd8b2fbfce4e0ba9526d5e7a7bcb4366ebe02a192d742e4","tests/ui/private.stderr":"ef4b8437d818a0e037ad23b19ef6d2971e46a4cfe94707d9c5dd402e390ef595","tests/ui/unexpected-arg.rs":"27f8baf78620673ce49eb4a376dd2210e446d2fbc33a4160aa72c40f597a599a","tests/ui/unexpected-arg.stderr":"79e6ff168baf87576c95821d11ec48e7701d50c8c93811aaf9715c1de8e77ce0","tests/ui/unexpected.rs":"157afd8323c9226a8f9ac1f1623a7747d8b9563e95b66d0208020d2d15781adc","tests/ui/unexpected.stderr":"7478c6e53832e3fe5fd6be30aad2824e920780d9b6355b95ca35ffcd2522c3b0","tests/ui/unknown-arg.rs":"724aeb6614c96e925856fb0e73ec38312cc9abc918094188d928e41626fbe512","tests/ui/unknown-arg.stderr":"379cb35e501c17091dd999f0bb889c25596d94838ff5a1437407d4f97f8c13b1"},"package":"dc375e1527247fe1a97d8b7156678dfe7c1af2fc075c9a4db3690ecd2a148068"}
\ No newline at end of file
diff --git a/third_party/rust/proc-macro-hack/Cargo.toml b/third_party/rust/proc-macro-hack/Cargo.toml
new file mode 100644
index 0000000000..ec46c31a94
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/Cargo.toml
@@ -0,0 +1,47 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+rust-version = "1.31"
+name = "proc-macro-hack"
+version = "0.5.20+deprecated"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+description = "Procedural macros in expression position"
+readme = "README.md"
+categories = ["development-tools::procedural-macro-helpers"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/dtolnay/proc-macro-hack"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[lib]
+proc-macro = true
+
+[dev-dependencies.demo-hack]
+version = "0.0.5"
+
+[dev-dependencies.demo-hack-impl]
+version = "0.0.5"
+
+[dev-dependencies.quote]
+version = "1.0"
+
+[dev-dependencies.rustversion]
+version = "1.0"
+
+[dev-dependencies.syn]
+version = "1.0.5"
+
+[dev-dependencies.trybuild]
+version = "1.0.49"
+features = ["diff"]
diff --git a/third_party/rust/proc-macro-hack/LICENSE-APACHE b/third_party/rust/proc-macro-hack/LICENSE-APACHE
new file mode 100644
index 0000000000..16fe87b06e
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
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diff --git a/third_party/rust/proc-macro-hack/LICENSE-MIT b/third_party/rust/proc-macro-hack/LICENSE-MIT
new file mode 100644
index 0000000000..f2675cdf1e
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2018 David Tolnay
+
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+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
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+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
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+DEALINGS IN THE SOFTWARE.
diff --git a/third_party/rust/proc-macro-hack/README.md b/third_party/rust/proc-macro-hack/README.md
new file mode 100644
index 0000000000..b72b8ef9dd
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/README.md
@@ -0,0 +1,155 @@
+Procedural macros in expression position
+========================================
+
+[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/proc--macro--hack-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/proc-macro-hack)
+[<img alt="crates.io" src="https://img.shields.io/crates/v/proc-macro-hack.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/proc-macro-hack)
+[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-proc--macro--hack-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/proc-macro-hack)
+[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/proc-macro-hack/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/proc-macro-hack/actions?query=branch%3Amaster)
+
+<table><tr><td><hr>
+<b>Note:</b> <i>As of Rust 1.45 this crate is superseded by native support for
+#[proc_macro] in expression position. Only consider using this crate if you care
+about supporting compilers between 1.31 and 1.45.</i>
+<hr></td></tr></table>
+
+Since Rust 1.30, the language supports user-defined function-like procedural
+macros. However these can only be invoked in item position, not in statements or
+expressions.
+
+This crate implements an alternative type of procedural macro that can be
+invoked in statement or expression position.
+
+This approach works with any Rust version 1.31+.
+
+## Defining procedural macros
+
+Two crates are required to define a procedural macro.
+
+### The implementation crate
+
+This crate must contain nothing but procedural macros. Private helper
+functions and private modules are fine but nothing can be public.
+
+[&raquo; example of an implementation crate][demo-hack-impl]
+
+Just like you would use a #\[proc_macro\] attribute to define a natively
+supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
+attribute to define a procedural macro that works in expression position.
+The function signature is the same as for ordinary function-like procedural
+macros.
+
+```rust
+use proc_macro::TokenStream;
+use proc_macro_hack::proc_macro_hack;
+use quote::quote;
+use syn::{parse_macro_input, Expr};
+
+#[proc_macro_hack]
+pub fn add_one(input: TokenStream) -> TokenStream {
+    let expr = parse_macro_input!(input as Expr);
+    TokenStream::from(quote! {
+        1 + (#expr)
+    })
+}
+```
+
+### The declaration crate
+
+This crate is allowed to contain other public things if you need, for
+example traits or functions or ordinary macros.
+
+[&raquo; example of a declaration crate][demo-hack]
+
+Within the declaration crate there needs to be a re-export of your
+procedural macro from the implementation crate. The re-export also carries a
+\#\[proc_macro_hack\] attribute.
+
+```rust
+use proc_macro_hack::proc_macro_hack;
+
+/// Add one to an expression.
+///
+/// (Documentation goes here on the re-export, not in the other crate.)
+#[proc_macro_hack]
+pub use demo_hack_impl::add_one;
+```
+
+Both crates depend on `proc-macro-hack`:
+
+```toml
+[dependencies]
+proc-macro-hack = "0.5"
+```
+
+Additionally, your implementation crate (but not your declaration crate) is
+a proc macro crate:
+
+```toml
+[lib]
+proc-macro = true
+```
+
+## Using procedural macros
+
+Users of your crate depend on your declaration crate (not your
+implementation crate), then use your procedural macros as usual.
+
+[&raquo; example of a downstream crate][example]
+
+```rust
+use demo_hack::add_one;
+
+fn main() {
+    let two = 2;
+    let nine = add_one!(two) + add_one!(2 + 3);
+    println!("nine = {}", nine);
+}
+```
+
+[demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
+[demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
+[example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
+
+## Limitations
+
+- Only proc macros in expression position are supported. Proc macros in pattern
+  position ([#20]) are not supported.
+
+- By default, nested invocations are not supported i.e. the code emitted by a
+  proc-macro-hack macro invocation cannot contain recursive calls to the same
+  proc-macro-hack macro nor calls to any other proc-macro-hack macros. Use
+  [`proc-macro-nested`] if you require support for nested invocations.
+
+- By default, hygiene is structured such that the expanded code can't refer to
+  local variables other than those passed by name somewhere in the macro input.
+  If your macro must refer to *local* variables that don't get named in the
+  macro input, use `#[proc_macro_hack(fake_call_site)]` on the re-export in your
+  declaration crate. *Most macros won't need this.*
+
+- On compilers that are new enough to natively support proc macros in expression
+  position, proc-macro-hack does not automatically use that support, since the
+  hygiene can be subtly different between the two implementations. To opt in to
+  compiling your macro to native `#[proc_macro]` on sufficiently new compilers,
+  use `#[proc_macro_hack(only_hack_old_rustc)]` on the re-export in your
+  declaration crate.
+
+[#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
+[#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
+[`proc-macro-nested`]: https://docs.rs/proc-macro-nested
+
+<br>
+
+#### License
+
+<sup>
+Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
+2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
+</sup>
+
+<br>
+
+<sub>
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in this hack by you, as defined in the Apache-2.0 license, shall
+be dual licensed as above, without any additional terms or conditions.
+</sub>
diff --git a/third_party/rust/proc-macro-hack/build.rs b/third_party/rust/proc-macro-hack/build.rs
new file mode 100644
index 0000000000..6ab40985b6
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/build.rs
@@ -0,0 +1,31 @@
+use std::env;
+use std::process::Command;
+use std::str;
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let minor = match rustc_minor_version() {
+        Some(minor) => minor,
+        None => return,
+    };
+
+    // Function-like procedural macros in expressions, patterns, and statements
+    // stabilized in Rust 1.45:
+    // https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#stabilizing-function-like-procedural-macros-in-expressions-patterns-and-statements
+    if minor < 45 {
+        println!("cargo:rustc-cfg=need_proc_macro_hack");
+    }
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = env::var_os("RUSTC")?;
+    let output = Command::new(rustc).arg("--version").output().ok()?;
+    let version = str::from_utf8(&output.stdout).ok()?;
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+    pieces.next()?.parse().ok()
+}
diff --git a/third_party/rust/proc-macro-hack/src/error.rs b/third_party/rust/proc-macro-hack/src/error.rs
new file mode 100644
index 0000000000..7334a53d9a
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/src/error.rs
@@ -0,0 +1,39 @@
+use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
+use std::iter::FromIterator;
+
+pub struct Error {
+    span: Span,
+    msg: String,
+}
+
+impl Error {
+    pub fn new(span: Span, msg: impl Into<String>) -> Self {
+        Error {
+            span,
+            msg: msg.into(),
+        }
+    }
+}
+
+pub fn compile_error(err: Error) -> TokenStream {
+    // compile_error!($msg)
+    TokenStream::from_iter(vec![
+        TokenTree::Ident(Ident::new("compile_error", err.span)),
+        TokenTree::Punct({
+            let mut punct = Punct::new('!', Spacing::Alone);
+            punct.set_span(err.span);
+            punct
+        }),
+        TokenTree::Group({
+            let mut group = Group::new(Delimiter::Brace, {
+                TokenStream::from_iter(vec![TokenTree::Literal({
+                    let mut string = Literal::string(&err.msg);
+                    string.set_span(err.span);
+                    string
+                })])
+            });
+            group.set_span(err.span);
+            group
+        }),
+    ])
+}
diff --git a/third_party/rust/proc-macro-hack/src/iter.rs b/third_party/rust/proc-macro-hack/src/iter.rs
new file mode 100644
index 0000000000..722013c7d6
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/src/iter.rs
@@ -0,0 +1,42 @@
+use proc_macro::{token_stream, Delimiter, TokenStream, TokenTree};
+
+pub type Iter<'a> = &'a mut IterImpl;
+
+pub struct IterImpl {
+    stack: Vec<token_stream::IntoIter>,
+    peeked: Option<TokenTree>,
+}
+
+pub fn new(tokens: TokenStream) -> IterImpl {
+    IterImpl {
+        stack: vec![tokens.into_iter()],
+        peeked: None,
+    }
+}
+
+impl IterImpl {
+    pub fn peek(&mut self) -> Option<&TokenTree> {
+        self.peeked = self.next();
+        self.peeked.as_ref()
+    }
+}
+
+impl Iterator for IterImpl {
+    type Item = TokenTree;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(tt) = self.peeked.take() {
+            return Some(tt);
+        }
+        loop {
+            let top = self.stack.last_mut()?;
+            match top.next() {
+                None => drop(self.stack.pop()),
+                Some(TokenTree::Group(ref group)) if group.delimiter() == Delimiter::None => {
+                    self.stack.push(group.stream().into_iter());
+                }
+                Some(tt) => return Some(tt),
+            }
+        }
+    }
+}
diff --git a/third_party/rust/proc-macro-hack/src/lib.rs b/third_party/rust/proc-macro-hack/src/lib.rs
new file mode 100644
index 0000000000..9a5a8ac432
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/src/lib.rs
@@ -0,0 +1,599 @@
+//! [![github]](https://github.com/dtolnay/proc-macro-hack)&ensp;[![crates-io]](https://crates.io/crates/proc-macro-hack)&ensp;[![docs-rs]](https://docs.rs/proc-macro-hack)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
+//!
+//! <br>
+//!
+//! <table><tr><td><hr>
+//! <b>Note:</b> <i>As of Rust 1.45 this crate is superseded by native support
+//! for #[proc_macro] in expression position. Only consider using this crate if
+//! you care about supporting compilers between 1.31 and 1.45.</i>
+//! <hr></td></tr></table>
+//!
+//! Since Rust 1.30, the language supports user-defined function-like procedural
+//! macros. However these can only be invoked in item position, not in
+//! statements or expressions.
+//!
+//! This crate implements an alternative type of procedural macro that can be
+//! invoked in statement or expression position.
+//!
+//! # Defining procedural macros
+//!
+//! Two crates are required to define a procedural macro.
+//!
+//! ## The implementation crate
+//!
+//! This crate must contain nothing but procedural macros. Private helper
+//! functions and private modules are fine but nothing can be public.
+//!
+//! [&raquo; example of an implementation crate][demo-hack-impl]
+//!
+//! Just like you would use a #\[proc_macro\] attribute to define a natively
+//! supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
+//! attribute to define a procedural macro that works in expression position.
+//! The function signature is the same as for ordinary function-like procedural
+//! macros.
+//!
+//! ```
+//! # extern crate proc_macro;
+//! #
+//! use proc_macro::TokenStream;
+//! use proc_macro_hack::proc_macro_hack;
+//! use quote::quote;
+//! use syn::{parse_macro_input, Expr};
+//!
+//! # const IGNORE: &str = stringify! {
+//! #[proc_macro_hack]
+//! # };
+//! pub fn add_one(input: TokenStream) -> TokenStream {
+//!     let expr = parse_macro_input!(input as Expr);
+//!     TokenStream::from(quote! {
+//!         1 + (#expr)
+//!     })
+//! }
+//! #
+//! # fn main() {}
+//! ```
+//!
+//! ## The declaration crate
+//!
+//! This crate is allowed to contain other public things if you need, for
+//! example traits or functions or ordinary macros.
+//!
+//! [&raquo; example of a declaration crate][demo-hack]
+//!
+//! Within the declaration crate there needs to be a re-export of your
+//! procedural macro from the implementation crate. The re-export also carries a
+//! \#\[proc_macro_hack\] attribute.
+//!
+//! ```
+//! use proc_macro_hack::proc_macro_hack;
+//!
+//! /// Add one to an expression.
+//! ///
+//! /// (Documentation goes here on the re-export, not in the other crate.)
+//! #[proc_macro_hack]
+//! pub use demo_hack_impl::add_one;
+//! #
+//! # fn main() {}
+//! ```
+//!
+//! Both crates depend on `proc-macro-hack`:
+//!
+//! ```toml
+//! [dependencies]
+//! proc-macro-hack = "0.5"
+//! ```
+//!
+//! Additionally, your implementation crate (but not your declaration crate) is
+//! a proc macro crate:
+//!
+//! ```toml
+//! [lib]
+//! proc-macro = true
+//! ```
+//!
+//! # Using procedural macros
+//!
+//! Users of your crate depend on your declaration crate (not your
+//! implementation crate), then use your procedural macros as usual.
+//!
+//! [&raquo; example of a downstream crate][example]
+//!
+//! ```
+//! use demo_hack::add_one;
+//!
+//! fn main() {
+//!     let two = 2;
+//!     let nine = add_one!(two) + add_one!(2 + 3);
+//!     println!("nine = {}", nine);
+//! }
+//! ```
+//!
+//! [demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
+//! [demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
+//! [example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
+//!
+//! # Limitations
+//!
+//! - Only proc macros in expression position are supported. Proc macros in
+//!   pattern position ([#20]) are not supported.
+//!
+//! - By default, nested invocations are not supported i.e. the code emitted by
+//!   a proc-macro-hack macro invocation cannot contain recursive calls to the
+//!   same proc-macro-hack macro nor calls to any other proc-macro-hack macros.
+//!   Use [`proc-macro-nested`] if you require support for nested invocations.
+//!
+//! - By default, hygiene is structured such that the expanded code can't refer
+//!   to local variables other than those passed by name somewhere in the macro
+//!   input. If your macro must refer to *local* variables that don't get named
+//!   in the macro input, use `#[proc_macro_hack(fake_call_site)]` on the
+//!   re-export in your declaration crate. *Most macros won't need this.*
+//!
+//! - On compilers that are new enough to natively support proc macros in
+//!   expression position, proc-macro-hack does not automatically use that
+//!   support, since the hygiene can be subtly different between the two
+//!   implementations. To opt in to compiling your macro to native
+//!   `#[proc_macro]` on sufficiently new compilers, use
+//!   `#[proc_macro_hack(only_hack_old_rustc)]` on the re-export in your
+//!   declaration crate.
+//!
+//! [#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
+//! [#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
+//! [`proc-macro-nested`]: https://docs.rs/proc-macro-nested
+
+#![recursion_limit = "512"]
+#![allow(
+    clippy::doc_markdown,
+    clippy::manual_strip,
+    clippy::module_name_repetitions,
+    clippy::needless_doctest_main,
+    clippy::needless_pass_by_value,
+    clippy::too_many_lines,
+    clippy::toplevel_ref_arg
+)]
+
+extern crate proc_macro;
+
+#[macro_use]
+mod quote;
+
+mod error;
+mod iter;
+mod parse;
+
+use crate::error::{compile_error, Error};
+use crate::iter::Iter;
+use crate::parse::{
+    parse_define_args, parse_enum_hack, parse_export_args, parse_fake_call_site, parse_input,
+};
+use proc_macro::{Ident, Punct, Spacing, Span, TokenStream, TokenTree};
+use std::fmt::Write;
+
+type Visibility = Option<Ident>;
+
+enum Input {
+    Export(Export),
+    Define(Define),
+}
+
+// pub use demo_hack_impl::{m1, m2 as qrst};
+struct Export {
+    attrs: TokenStream,
+    vis: Visibility,
+    from: Ident,
+    macros: Vec<Macro>,
+}
+
+// pub fn m1(input: TokenStream) -> TokenStream { ... }
+struct Define {
+    attrs: TokenStream,
+    name: Ident,
+    body: TokenStream,
+}
+
+struct Macro {
+    name: Ident,
+    export_as: Ident,
+}
+
+#[proc_macro_attribute]
+pub fn proc_macro_hack(args: TokenStream, input: TokenStream) -> TokenStream {
+    let ref mut args = iter::new(args);
+    let ref mut input = iter::new(input);
+    expand_proc_macro_hack(args, input).unwrap_or_else(compile_error)
+}
+
+fn expand_proc_macro_hack(args: Iter, input: Iter) -> Result<TokenStream, Error> {
+    match parse_input(input)? {
+        Input::Export(export) => {
+            let args = parse_export_args(args)?;
+            Ok(expand_export(export, args))
+        }
+        Input::Define(define) => {
+            parse_define_args(args)?;
+            Ok(expand_define(define))
+        }
+    }
+}
+
+#[doc(hidden)]
+#[proc_macro_derive(ProcMacroHack)]
+pub fn enum_hack(input: TokenStream) -> TokenStream {
+    let ref mut input = iter::new(input);
+    parse_enum_hack(input).unwrap_or_else(compile_error)
+}
+
+struct FakeCallSite {
+    derive: Ident,
+    rest: TokenStream,
+}
+
+#[doc(hidden)]
+#[proc_macro_attribute]
+pub fn fake_call_site(args: TokenStream, input: TokenStream) -> TokenStream {
+    let ref mut args = iter::new(args);
+    let ref mut input = iter::new(input);
+    expand_fake_call_site(args, input).unwrap_or_else(compile_error)
+}
+
+fn expand_fake_call_site(args: Iter, input: Iter) -> Result<TokenStream, Error> {
+    let span = match args.next() {
+        Some(token) => token.span(),
+        None => return Ok(input.collect()),
+    };
+
+    let input = parse_fake_call_site(input)?;
+    let mut derive = input.derive;
+    derive.set_span(span);
+    let rest = input.rest;
+
+    Ok(quote! {
+        #[derive(#derive)]
+        #rest
+    })
+}
+
+struct ExportArgs {
+    support_nested: bool,
+    internal_macro_calls: u16,
+    fake_call_site: bool,
+    only_hack_old_rustc: bool,
+}
+
+fn expand_export(export: Export, args: ExportArgs) -> TokenStream {
+    if args.only_hack_old_rustc && cfg!(not(need_proc_macro_hack)) {
+        return expand_export_nohack(export);
+    }
+
+    let dummy = dummy_name_for_export(&export);
+
+    let attrs = export.attrs;
+    let vis = export.vis;
+    let macro_export = match vis {
+        Some(_) => quote!(#[macro_export]),
+        None => quote!(),
+    };
+    let crate_prefix = vis.as_ref().map(|_| quote!($crate::));
+    let enum_variant = if args.support_nested {
+        if args.internal_macro_calls == 0 {
+            Ident::new("Nested", Span::call_site())
+        } else {
+            let name = format!("Nested{}", args.internal_macro_calls);
+            Ident::new(&name, Span::call_site())
+        }
+    } else {
+        Ident::new("Value", Span::call_site())
+    };
+
+    let from = export.from;
+    let mut actual_names = TokenStream::new();
+    let mut export_dispatch = TokenStream::new();
+    let mut export_call_site = TokenStream::new();
+    let mut macro_rules = TokenStream::new();
+    for Macro { name, export_as } in &export.macros {
+        let hacked = hacked_proc_macro_name(name);
+        let dispatch = dispatch_macro_name(name);
+        let call_site = call_site_macro_name(name);
+
+        if !actual_names.is_empty() {
+            actual_names.extend(quote!(,));
+        }
+        actual_names.extend(quote!(#hacked));
+
+        if !export_dispatch.is_empty() {
+            export_dispatch.extend(quote!(,));
+        }
+        export_dispatch.extend(quote!(dispatch as #dispatch));
+
+        if !export_call_site.is_empty() {
+            export_call_site.extend(quote!(,));
+        }
+        export_call_site.extend(quote!(fake_call_site as #call_site));
+
+        let do_derive = if !args.fake_call_site {
+            quote! {
+                #[derive(#crate_prefix #hacked)]
+            }
+        } else if crate_prefix.is_some() {
+            quote! {
+                use #crate_prefix #hacked;
+                #[#crate_prefix #call_site ($($proc_macro)*)]
+                #[derive(#hacked)]
+            }
+        } else {
+            quote! {
+                #[#call_site ($($proc_macro)*)]
+                #[derive(#hacked)]
+            }
+        };
+
+        let proc_macro_call = if args.support_nested {
+            let extra_bangs = (0..args.internal_macro_calls)
+                .map(|_| TokenTree::Punct(Punct::new('!', Spacing::Alone)))
+                .collect::<TokenStream>();
+            quote! {
+                #crate_prefix #dispatch! { ($($proc_macro)*) #extra_bangs }
+            }
+        } else {
+            quote! {
+                proc_macro_call!()
+            }
+        };
+
+        macro_rules.extend(quote! {
+            #attrs
+            #macro_export
+            macro_rules! #export_as {
+                ($($proc_macro:tt)*) => {{
+                    #do_derive
+                    #[allow(dead_code)]
+                    enum ProcMacroHack {
+                        #enum_variant = (stringify! { $($proc_macro)* }, 0).1,
+                    }
+                    #proc_macro_call
+                }};
+            }
+        });
+    }
+
+    if export.macros.len() != 1 {
+        export_dispatch = quote!({#export_dispatch});
+        export_call_site = quote!({#export_call_site});
+        actual_names = quote!({#actual_names});
+    }
+
+    let export_dispatch = if args.support_nested {
+        quote! {
+            #[doc(hidden)]
+            #vis use proc_macro_nested::#export_dispatch;
+        }
+    } else {
+        quote!()
+    };
+
+    let export_call_site = if args.fake_call_site {
+        quote! {
+            #[doc(hidden)]
+            #vis use proc_macro_hack::#export_call_site;
+        }
+    } else {
+        quote!()
+    };
+
+    let expanded = quote! {
+        #[doc(hidden)]
+        #vis use #from::#actual_names;
+
+        #export_dispatch
+        #export_call_site
+
+        #macro_rules
+    };
+
+    wrap_in_enum_hack(dummy, expanded)
+}
+
+fn expand_export_nohack(export: Export) -> TokenStream {
+    let attrs = export.attrs;
+    let vis = export.vis;
+    let from = export.from;
+    let mut names = TokenStream::new();
+
+    for Macro { name, export_as } in &export.macros {
+        let pub_name = pub_proc_macro_name(name);
+        if !names.is_empty() {
+            names.extend(quote!(,));
+        }
+        names.extend(quote!(#pub_name as #export_as));
+    }
+
+    if export.macros.len() != 1 {
+        names = quote!({#names});
+    }
+
+    quote! {
+        #attrs
+        #vis use #from::#names;
+    }
+}
+
+fn expand_define(define: Define) -> TokenStream {
+    let attrs = define.attrs;
+    let name = define.name;
+    let pub_name = pub_proc_macro_name(&name);
+    let hacked = hacked_proc_macro_name(&name);
+    let body = define.body;
+
+    quote! {
+        mod #pub_name {
+            extern crate proc_macro;
+            pub use self::proc_macro::*;
+        }
+
+        #attrs
+        #[doc(hidden)]
+        #[proc_macro_derive(#hacked)]
+        pub fn #hacked(input: #pub_name::TokenStream) -> #pub_name::TokenStream {
+            use std::iter::FromIterator;
+
+            let mut iter = input.into_iter();
+            iter.next().unwrap(); // `enum`
+            iter.next().unwrap(); // `ProcMacroHack`
+            iter.next().unwrap(); // `#`
+            iter.next().unwrap(); // `[allow(dead_code)]`
+
+            let mut braces = match iter.next().unwrap() {
+                #pub_name::TokenTree::Group(group) => group.stream().into_iter(),
+                _ => unimplemented!(),
+            };
+            let variant = braces.next().unwrap(); // `Value` or `Nested`
+            let varname = variant.to_string();
+            let support_nested = varname.starts_with("Nested");
+            braces.next().unwrap(); // `=`
+
+            let mut parens = match braces.next().unwrap() {
+                #pub_name::TokenTree::Group(group) => group.stream().into_iter(),
+                _ => unimplemented!(),
+            };
+            parens.next().unwrap(); // `stringify`
+            parens.next().unwrap(); // `!`
+
+            let inner = match parens.next().unwrap() {
+                #pub_name::TokenTree::Group(group) => group.stream(),
+                _ => unimplemented!(),
+            };
+
+            let output: #pub_name::TokenStream = #name(inner.clone());
+
+            fn count_bangs(input: #pub_name::TokenStream) -> usize {
+                let mut count = 0;
+                for token in input {
+                    match token {
+                        #pub_name::TokenTree::Punct(punct) => {
+                            if punct.as_char() == '!' {
+                                count += 1;
+                            }
+                        }
+                        #pub_name::TokenTree::Group(group) => {
+                            count += count_bangs(group.stream());
+                        }
+                        _ => {}
+                    }
+                }
+                count
+            }
+
+            // macro_rules! proc_macro_call {
+            //     () => { #output }
+            // }
+            #pub_name::TokenStream::from_iter(vec![
+                #pub_name::TokenTree::Ident(
+                    #pub_name::Ident::new("macro_rules", #pub_name::Span::call_site()),
+                ),
+                #pub_name::TokenTree::Punct(
+                    #pub_name::Punct::new('!', #pub_name::Spacing::Alone),
+                ),
+                #pub_name::TokenTree::Ident(
+                    #pub_name::Ident::new(
+                        &if support_nested {
+                            let extra_bangs = if varname == "Nested" {
+                                0
+                            } else {
+                                varname["Nested".len()..].parse().unwrap()
+                            };
+                            format!("proc_macro_call_{}", extra_bangs + count_bangs(inner))
+                        } else {
+                            String::from("proc_macro_call")
+                        },
+                        #pub_name::Span::call_site(),
+                    ),
+                ),
+                #pub_name::TokenTree::Group(
+                    #pub_name::Group::new(#pub_name::Delimiter::Brace, #pub_name::TokenStream::from_iter(vec![
+                        #pub_name::TokenTree::Group(
+                            #pub_name::Group::new(#pub_name::Delimiter::Parenthesis, #pub_name::TokenStream::new()),
+                        ),
+                        #pub_name::TokenTree::Punct(
+                            #pub_name::Punct::new('=', #pub_name::Spacing::Joint),
+                        ),
+                        #pub_name::TokenTree::Punct(
+                            #pub_name::Punct::new('>', #pub_name::Spacing::Alone),
+                        ),
+                        #pub_name::TokenTree::Group(
+                            #pub_name::Group::new(#pub_name::Delimiter::Brace, output),
+                        ),
+                    ])),
+                ),
+            ])
+        }
+
+        #attrs
+        #[proc_macro]
+        pub fn #pub_name(input: #pub_name::TokenStream) -> #pub_name::TokenStream {
+            #name(input)
+        }
+
+        fn #name #body
+    }
+}
+
+fn pub_proc_macro_name(conceptual: &Ident) -> Ident {
+    Ident::new(
+        &format!("proc_macro_hack_{}", conceptual),
+        conceptual.span(),
+    )
+}
+
+fn hacked_proc_macro_name(conceptual: &Ident) -> Ident {
+    Ident::new(
+        &format!("_proc_macro_hack_{}", conceptual),
+        conceptual.span(),
+    )
+}
+
+fn dispatch_macro_name(conceptual: &Ident) -> Ident {
+    Ident::new(
+        &format!("proc_macro_call_{}", conceptual),
+        conceptual.span(),
+    )
+}
+
+fn call_site_macro_name(conceptual: &Ident) -> Ident {
+    Ident::new(
+        &format!("proc_macro_fake_call_site_{}", conceptual),
+        conceptual.span(),
+    )
+}
+
+fn dummy_name_for_export(export: &Export) -> String {
+    let mut dummy = String::new();
+    let from = unraw(&export.from).to_string();
+    write!(dummy, "_{}{}", from.len(), from).unwrap();
+    for m in &export.macros {
+        let name = unraw(&m.name).to_string();
+        write!(dummy, "_{}{}", name.len(), name).unwrap();
+    }
+    dummy
+}
+
+fn unraw(ident: &Ident) -> Ident {
+    let string = ident.to_string();
+    if string.starts_with("r#") {
+        Ident::new(&string[2..], ident.span())
+    } else {
+        ident.clone()
+    }
+}
+
+fn wrap_in_enum_hack(dummy: String, inner: TokenStream) -> TokenStream {
+    let dummy = Ident::new(&dummy, Span::call_site());
+    quote! {
+        #[derive(proc_macro_hack::ProcMacroHack)]
+        enum #dummy {
+            Value = (stringify! { #inner }, 0).1,
+        }
+    }
+}
diff --git a/third_party/rust/proc-macro-hack/src/parse.rs b/third_party/rust/proc-macro-hack/src/parse.rs
new file mode 100644
index 0000000000..f9c3b80290
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/src/parse.rs
@@ -0,0 +1,254 @@
+use crate::iter::{self, Iter, IterImpl};
+use crate::{Define, Error, Export, ExportArgs, FakeCallSite, Input, Macro, Visibility};
+use proc_macro::Delimiter::{Brace, Bracket, Parenthesis};
+use proc_macro::{Delimiter, Ident, Span, TokenStream, TokenTree};
+
+pub(crate) fn parse_input(tokens: Iter) -> Result<Input, Error> {
+    let attrs = parse_attributes(tokens)?;
+    let vis = parse_visibility(tokens);
+    let kw = parse_ident(tokens)?;
+    if kw.to_string() == "use" {
+        parse_export(attrs, vis, tokens).map(Input::Export)
+    } else if kw.to_string() == "fn" {
+        parse_define(attrs, vis, kw.span(), tokens).map(Input::Define)
+    } else {
+        Err(Error::new(
+            kw.span(),
+            "unexpected input to #[proc_macro_hack]",
+        ))
+    }
+}
+
+fn parse_export(attrs: TokenStream, vis: Visibility, tokens: Iter) -> Result<Export, Error> {
+    let _ = parse_punct(tokens, ':');
+    let _ = parse_punct(tokens, ':');
+    let from = parse_ident(tokens)?;
+    parse_punct(tokens, ':')?;
+    parse_punct(tokens, ':')?;
+
+    let mut macros = Vec::new();
+    match tokens.peek() {
+        Some(TokenTree::Group(group)) if group.delimiter() == Brace => {
+            let ref mut content = iter::new(group.stream());
+            loop {
+                macros.push(parse_macro(content)?);
+                if content.peek().is_none() {
+                    break;
+                }
+                parse_punct(content, ',')?;
+                if content.peek().is_none() {
+                    break;
+                }
+            }
+            tokens.next().unwrap();
+        }
+        _ => macros.push(parse_macro(tokens)?),
+    }
+
+    parse_punct(tokens, ';')?;
+    Ok(Export {
+        attrs,
+        vis,
+        from,
+        macros,
+    })
+}
+
+fn parse_punct(tokens: Iter, ch: char) -> Result<(), Error> {
+    match tokens.peek() {
+        Some(TokenTree::Punct(punct)) if punct.as_char() == ch => {
+            tokens.next().unwrap();
+            Ok(())
+        }
+        tt => Err(Error::new(
+            tt.map_or_else(Span::call_site, TokenTree::span),
+            format!("expected `{}`", ch),
+        )),
+    }
+}
+
+fn parse_define(
+    attrs: TokenStream,
+    vis: Visibility,
+    fn_token: Span,
+    tokens: Iter,
+) -> Result<Define, Error> {
+    if vis.is_none() {
+        return Err(Error::new(
+            fn_token,
+            "functions tagged with `#[proc_macro_hack]` must be `pub`",
+        ));
+    }
+    let name = parse_ident(tokens)?;
+    let body = tokens.collect();
+    Ok(Define { attrs, name, body })
+}
+
+fn parse_macro(tokens: Iter) -> Result<Macro, Error> {
+    let name = parse_ident(tokens)?;
+    let export_as = match tokens.peek() {
+        Some(TokenTree::Ident(ident)) if ident.to_string() == "as" => {
+            tokens.next().unwrap();
+            parse_ident(tokens)?
+        }
+        _ => name.clone(),
+    };
+    Ok(Macro { name, export_as })
+}
+
+fn parse_ident(tokens: Iter) -> Result<Ident, Error> {
+    match tokens.next() {
+        Some(TokenTree::Ident(ident)) => Ok(ident),
+        tt => Err(Error::new(
+            tt.as_ref().map_or_else(Span::call_site, TokenTree::span),
+            "expected identifier",
+        )),
+    }
+}
+
+fn parse_keyword(tokens: Iter, kw: &'static str) -> Result<(), Error> {
+    match &tokens.next() {
+        Some(TokenTree::Ident(ident)) if ident.to_string() == kw => Ok(()),
+        tt => Err(Error::new(
+            tt.as_ref().map_or_else(Span::call_site, TokenTree::span),
+            format!("expected `{}`", kw),
+        )),
+    }
+}
+
+fn parse_int(tokens: Iter) -> Result<u16, Span> {
+    match tokens.next() {
+        Some(TokenTree::Literal(lit)) => lit.to_string().parse().map_err(|_| lit.span()),
+        Some(tt) => Err(tt.span()),
+        None => Err(Span::call_site()),
+    }
+}
+
+fn parse_group(tokens: Iter, delimiter: Delimiter) -> Result<IterImpl, Error> {
+    match &tokens.next() {
+        Some(TokenTree::Group(group)) if group.delimiter() == delimiter => {
+            Ok(iter::new(group.stream()))
+        }
+        tt => Err(Error::new(
+            tt.as_ref().map_or_else(Span::call_site, TokenTree::span),
+            "expected delimiter",
+        )),
+    }
+}
+
+fn parse_visibility(tokens: Iter) -> Visibility {
+    if let Some(TokenTree::Ident(ident)) = tokens.peek() {
+        if ident.to_string() == "pub" {
+            match tokens.next().unwrap() {
+                TokenTree::Ident(vis) => return Some(vis),
+                _ => unreachable!(),
+            }
+        }
+    }
+    None
+}
+
+fn parse_attributes(tokens: Iter) -> Result<TokenStream, Error> {
+    let mut attrs = TokenStream::new();
+    while let Some(TokenTree::Punct(punct)) = tokens.peek() {
+        if punct.as_char() != '#' {
+            break;
+        }
+        let span = punct.span();
+        attrs.extend(tokens.next());
+        match tokens.peek() {
+            Some(TokenTree::Group(group)) if group.delimiter() == Bracket => {
+                attrs.extend(tokens.next());
+            }
+            _ => return Err(Error::new(span, "unexpected input")),
+        }
+    }
+    Ok(attrs)
+}
+
+pub(crate) fn parse_export_args(tokens: Iter) -> Result<ExportArgs, Error> {
+    let mut args = ExportArgs {
+        support_nested: false,
+        internal_macro_calls: 0,
+        fake_call_site: false,
+        only_hack_old_rustc: false,
+    };
+
+    while let Some(tt) = tokens.next() {
+        match &tt {
+            TokenTree::Ident(ident) if ident.to_string() == "support_nested" => {
+                args.support_nested = true;
+            }
+            TokenTree::Ident(ident) if ident.to_string() == "internal_macro_calls" => {
+                parse_punct(tokens, '=')?;
+                let calls = parse_int(tokens).map_err(|span| {
+                    Error::new(span, "expected integer value for internal_macro_calls")
+                })?;
+                args.internal_macro_calls = calls;
+            }
+            TokenTree::Ident(ident) if ident.to_string() == "fake_call_site" => {
+                args.fake_call_site = true;
+            }
+            TokenTree::Ident(ident) if ident.to_string() == "only_hack_old_rustc" => {
+                args.only_hack_old_rustc = true;
+            }
+            _ => {
+                return Err(Error::new(
+                    tt.span(),
+                    "expected one of: `support_nested`, `internal_macro_calls`, `fake_call_site`, `only_hack_old_rustc`",
+                ));
+            }
+        }
+        if tokens.peek().is_none() {
+            break;
+        }
+        parse_punct(tokens, ',')?;
+    }
+
+    Ok(args)
+}
+
+pub(crate) fn parse_define_args(tokens: Iter) -> Result<(), Error> {
+    match tokens.peek() {
+        None => Ok(()),
+        Some(token) => Err(Error::new(
+            token.span(),
+            "unexpected argument to proc_macro_hack macro implementation; args are only accepted on the macro declaration (the `pub use`)",
+        )),
+    }
+}
+
+pub(crate) fn parse_enum_hack(tokens: Iter) -> Result<TokenStream, Error> {
+    parse_keyword(tokens, "enum")?;
+    parse_ident(tokens)?;
+
+    let ref mut braces = parse_group(tokens, Brace)?;
+    parse_ident(braces)?;
+    parse_punct(braces, '=')?;
+
+    let ref mut parens = parse_group(braces, Parenthesis)?;
+    parse_ident(parens)?;
+    parse_punct(parens, '!')?;
+
+    let ref mut inner = parse_group(parens, Brace)?;
+    let token_stream = inner.collect();
+
+    parse_punct(parens, ',')?;
+    let _ = parens.next();
+    parse_punct(braces, '.')?;
+    let _ = braces.next();
+    parse_punct(braces, ',')?;
+
+    Ok(token_stream)
+}
+
+pub(crate) fn parse_fake_call_site(tokens: Iter) -> Result<FakeCallSite, Error> {
+    parse_punct(tokens, '#')?;
+    let ref mut attr = parse_group(tokens, Bracket)?;
+    parse_keyword(attr, "derive")?;
+    let ref mut path = parse_group(attr, Parenthesis)?;
+    Ok(FakeCallSite {
+        derive: parse_ident(path)?,
+        rest: tokens.collect(),
+    })
+}
diff --git a/third_party/rust/proc-macro-hack/src/quote.rs b/third_party/rust/proc-macro-hack/src/quote.rs
new file mode 100644
index 0000000000..a3d648d1a4
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/src/quote.rs
@@ -0,0 +1,114 @@
+use proc_macro::{Ident, TokenStream, TokenTree};
+use std::iter;
+
+macro_rules! quote {
+    () => {
+        ::proc_macro::TokenStream::new()
+    };
+    ($($tt:tt)*) => {{
+        let mut tokens = ::proc_macro::TokenStream::new();
+        quote_each_token!(tokens $($tt)*);
+        tokens
+    }};
+}
+
+macro_rules! quote_each_token {
+    ($tokens:ident # $var:ident $($rest:tt)*) => {
+        $crate::quote::Tokens::extend(&mut $tokens, &$var);
+        quote_each_token!($tokens $($rest)*);
+    };
+    ($tokens:ident $ident:ident $($rest:tt)*) => {
+        <::proc_macro::TokenStream as ::std::iter::Extend<_>>::extend(
+            &mut $tokens,
+            ::std::iter::once(
+                ::proc_macro::TokenTree::Ident(
+                    ::proc_macro::Ident::new(
+                        stringify!($ident),
+                        ::proc_macro::Span::call_site(),
+                    ),
+                ),
+            ),
+        );
+        quote_each_token!($tokens $($rest)*);
+    };
+    ($tokens:ident ( $($inner:tt)* ) $($rest:tt)*) => {
+        <::proc_macro::TokenStream as ::std::iter::Extend<_>>::extend(
+            &mut $tokens,
+            ::std::iter::once(
+                ::proc_macro::TokenTree::Group(
+                    ::proc_macro::Group::new(
+                        ::proc_macro::Delimiter::Parenthesis,
+                        quote!($($inner)*),
+                    ),
+                ),
+            ),
+        );
+        quote_each_token!($tokens $($rest)*);
+    };
+    ($tokens:ident [ $($inner:tt)* ] $($rest:tt)*) => {
+        <::proc_macro::TokenStream as ::std::iter::Extend<_>>::extend(
+            &mut $tokens,
+            ::std::iter::once(
+                ::proc_macro::TokenTree::Group(
+                    ::proc_macro::Group::new(
+                        ::proc_macro::Delimiter::Bracket,
+                        quote!($($inner)*),
+                    ),
+                ),
+            ),
+        );
+        quote_each_token!($tokens $($rest)*);
+    };
+    ($tokens:ident { $($inner:tt)* } $($rest:tt)*) => {
+        <::proc_macro::TokenStream as ::std::iter::Extend<_>>::extend(
+            &mut $tokens,
+            ::std::iter::once(
+                ::proc_macro::TokenTree::Group(
+                    ::proc_macro::Group::new(
+                        ::proc_macro::Delimiter::Brace,
+                        quote!($($inner)*),
+                    ),
+                ),
+            ),
+        );
+        quote_each_token!($tokens $($rest)*);
+    };
+    ($tokens:ident $punct:tt $($rest:tt)*) => {
+        <::proc_macro::TokenStream as ::std::iter::Extend<_>>::extend(
+            &mut $tokens,
+            stringify!($punct).parse::<::proc_macro::TokenStream>(),
+        );
+        quote_each_token!($tokens $($rest)*);
+    };
+    ($tokens:ident) => {};
+}
+
+pub trait Tokens {
+    fn extend(tokens: &mut TokenStream, var: &Self);
+}
+
+impl Tokens for Ident {
+    fn extend(tokens: &mut TokenStream, var: &Self) {
+        tokens.extend(iter::once(TokenTree::Ident(var.clone())));
+    }
+}
+
+impl Tokens for TokenStream {
+    fn extend(tokens: &mut TokenStream, var: &Self) {
+        tokens.extend(var.clone());
+    }
+}
+
+impl<T: Tokens> Tokens for Option<T> {
+    fn extend(tokens: &mut TokenStream, var: &Self) {
+        if let Some(var) = var {
+            T::extend(tokens, var);
+        }
+    }
+}
+
+impl<T: Tokens> Tokens for &T {
+    fn extend(tokens: &mut TokenStream, var: &Self) {
+        T::extend(tokens, var);
+    }
+}
diff --git a/third_party/rust/proc-macro-hack/tests/compiletest.rs b/third_party/rust/proc-macro-hack/tests/compiletest.rs
new file mode 100644
index 0000000000..f9aea23b51
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/compiletest.rs
@@ -0,0 +1,6 @@
+#[rustversion::attr(not(nightly), ignore)]
+#[test]
+fn ui() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/ui/*.rs");
+}
diff --git a/third_party/rust/proc-macro-hack/tests/ui/private.rs b/third_party/rust/proc-macro-hack/tests/ui/private.rs
new file mode 100644
index 0000000000..1ab84446c7
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/private.rs
@@ -0,0 +1,8 @@
+use proc_macro_hack::proc_macro_hack;
+
+#[proc_macro_hack]
+fn my_macro(input: TokenStream) -> TokenStream {
+    unimplemented!()
+}
+
+fn main() {}
diff --git a/third_party/rust/proc-macro-hack/tests/ui/private.stderr b/third_party/rust/proc-macro-hack/tests/ui/private.stderr
new file mode 100644
index 0000000000..d3a3ea7ed4
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/private.stderr
@@ -0,0 +1,5 @@
+error: functions tagged with `#[proc_macro_hack]` must be `pub`
+ --> tests/ui/private.rs:4:1
+  |
+4 | fn my_macro(input: TokenStream) -> TokenStream {
+  | ^^
diff --git a/third_party/rust/proc-macro-hack/tests/ui/unexpected-arg.rs b/third_party/rust/proc-macro-hack/tests/ui/unexpected-arg.rs
new file mode 100644
index 0000000000..376fc0d986
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/unexpected-arg.rs
@@ -0,0 +1,8 @@
+use proc_macro_hack::proc_macro_hack;
+
+#[proc_macro_hack(fake_call_site)]
+pub fn my_macro(input: TokenStream) -> TokenStream {
+    unimplemented!()
+}
+
+fn main() {}
diff --git a/third_party/rust/proc-macro-hack/tests/ui/unexpected-arg.stderr b/third_party/rust/proc-macro-hack/tests/ui/unexpected-arg.stderr
new file mode 100644
index 0000000000..f32f05a1cd
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/unexpected-arg.stderr
@@ -0,0 +1,5 @@
+error: unexpected argument to proc_macro_hack macro implementation; args are only accepted on the macro declaration (the `pub use`)
+ --> tests/ui/unexpected-arg.rs:3:19
+  |
+3 | #[proc_macro_hack(fake_call_site)]
+  |                   ^^^^^^^^^^^^^^
diff --git a/third_party/rust/proc-macro-hack/tests/ui/unexpected.rs b/third_party/rust/proc-macro-hack/tests/ui/unexpected.rs
new file mode 100644
index 0000000000..122ded5191
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/unexpected.rs
@@ -0,0 +1,6 @@
+use proc_macro_hack::proc_macro_hack;
+
+#[proc_macro_hack]
+pub struct What;
+
+fn main() {}
diff --git a/third_party/rust/proc-macro-hack/tests/ui/unexpected.stderr b/third_party/rust/proc-macro-hack/tests/ui/unexpected.stderr
new file mode 100644
index 0000000000..60761b5149
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/unexpected.stderr
@@ -0,0 +1,5 @@
+error: unexpected input to #[proc_macro_hack]
+ --> tests/ui/unexpected.rs:4:5
+  |
+4 | pub struct What;
+  |     ^^^^^^
diff --git a/third_party/rust/proc-macro-hack/tests/ui/unknown-arg.rs b/third_party/rust/proc-macro-hack/tests/ui/unknown-arg.rs
new file mode 100644
index 0000000000..aa9b82c8f4
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/unknown-arg.rs
@@ -0,0 +1,6 @@
+use proc_macro_hack::proc_macro_hack;
+
+#[proc_macro_hack(fake_call_site, support_nexted)]
+pub use demo::some_macro;
+
+fn main() {}
diff --git a/third_party/rust/proc-macro-hack/tests/ui/unknown-arg.stderr b/third_party/rust/proc-macro-hack/tests/ui/unknown-arg.stderr
new file mode 100644
index 0000000000..772e6673d0
--- /dev/null
+++ b/third_party/rust/proc-macro-hack/tests/ui/unknown-arg.stderr
@@ -0,0 +1,5 @@
+error: expected one of: `support_nested`, `internal_macro_calls`, `fake_call_site`, `only_hack_old_rustc`
+ --> tests/ui/unknown-arg.rs:3:35
+  |
+3 | #[proc_macro_hack(fake_call_site, support_nexted)]
+  |                                   ^^^^^^^^^^^^^^