Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

10 files changed, 1456 insertions, 0 deletions

diff --git a/third_party/rust/id-arena/.cargo-checksum.json b/third_party/rust/id-arena/.cargo-checksum.json
new file mode 100644
index 0000000000..f28430a787
--- /dev/null
+++ b/third_party/rust/id-arena/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"CHANGELOG.md":"44d2bc9ae9829b9d80bbd64cf758a29c5b7a136e8049bde601f25b504ff5daf8","Cargo.toml":"68ffe09814502adc81ab77dacc5d76e5f439435a71b48ec9c575289193945cb7","LICENSE-APACHE":"a60eea817514531668d7e00765731449fe14d059d3249e0bc93b36de45f759f2","LICENSE-MIT":"378f5840b258e2779c39418f3f2d7b2ba96f1c7917dd6be0713f88305dbda397","README.md":"74619b782c5085d5e12762a2a209555e90770d0e08048d95a31f95febac0b4c6","README.tpl":"ec385000e14590a306855e7893daed0168102f33166bdc1e5cf5fa5599dac03f","src/lib.rs":"ee705a8a93ccfa0f958e421a1e27440e5b92afd422ee6579f66282287cb9abe8","src/rayon.rs":"48807a5563e6c248bab2731b60b00148084db9c071cf3c47cdb12dc7ecfa84e0","tests/readme_up_to_date.rs":"8db3e41d803e2a10307e7e35cb2afa6733e1c39ad34789752a927564bf6795b6"},"package":"25a2bc672d1148e28034f176e01fffebb08b35768468cc954630da77a1449005"}
\ No newline at end of file
diff --git a/third_party/rust/id-arena/CHANGELOG.md b/third_party/rust/id-arena/CHANGELOG.md
new file mode 100644
index 0000000000..0f3ecde738
--- /dev/null
+++ b/third_party/rust/id-arena/CHANGELOG.md
@@ -0,0 +1,65 @@
+# 2.2.1
+
+Released 2019-02-15.
+
+* Make sure our rayon parallel iterators are exported. Previously instances of
+  them were returned by `pub` methods but the types themselves were not
+  exported.
+
+# 2.2.0
+
+Released 2019-01-30.
+
+* Add the `Arena::alloc_with_id` method. This is better than using
+  `Arena::next_id` directly most of the time (but is also not *quite* as
+  flexible). See [#9](https://github.com/fitzgen/id-arena/issues/9) and
+  [#10](https://github.com/fitzgen/id-arena/pull/10).
+
+--------------------------------------------------------------------------------
+
+# 2.1.0
+
+Released 2019-01-25.
+
+* Added optional support for `rayon` parallel iteration. Enable the `rayon`
+  Cargo feature to get access.
+
+--------------------------------------------------------------------------------
+
+# 2.0.1
+
+Released 2019-01-09.
+
+* Implemented `Ord` and `PartialOrd` for `Id<T>`.
+* Added an `Arena::with_capacity` constructor.
+* Added `Arena::next_id` to get the id that will be used for the next
+  allocation.
+
+--------------------------------------------------------------------------------
+
+# 2.0.0
+
+Released 2018-11-28.
+
+* Introduces the `ArenaBehavior` trait, which allows one to customize identifier
+  types and do things like implement space optimizations or use identifiers for
+  many arenas at once.
+* Implements `Clone`, `PartialEq` and `Eq` for arenas.
+
+--------------------------------------------------------------------------------
+
+# 1.0.2
+
+Released 2018-11-25.
+
+* `Id<T>` now implements `Send` and `Sync`
+* The `PartialEq` implementation for `Id<T>` now correctly checks that two ids
+  are for the same arena when checking equality.
+
+--------------------------------------------------------------------------------
+
+# 1.0.1
+
+--------------------------------------------------------------------------------
+
+# 1.0.0
diff --git a/third_party/rust/id-arena/Cargo.toml b/third_party/rust/id-arena/Cargo.toml
new file mode 100644
index 0000000000..c8566221d4
--- /dev/null
+++ b/third_party/rust/id-arena/Cargo.toml
@@ -0,0 +1,31 @@
+# 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 believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+name = "id-arena"
+version = "2.2.1"
+authors = ["Nick Fitzgerald <fitzgen@gmail.com>", "Aleksey Kladov <aleksey.kladov@gmail.com>"]
+description = "A simple, id-based arena."
+documentation = "https://docs.rs/id-arena"
+readme = "README.md"
+categories = ["memory-management", "rust-patterns", "no-std"]
+license = "MIT/Apache-2.0"
+repository = "https://github.com/fitzgen/id-arena"
+[package.metadata.docs.rs]
+features = ["rayon"]
+[dependencies.rayon]
+version = "1.0.3"
+optional = true
+
+[features]
+default = ["std"]
+std = []
diff --git a/third_party/rust/id-arena/LICENSE-APACHE b/third_party/rust/id-arena/LICENSE-APACHE
new file mode 100644
index 0000000000..16fe87b06e
--- /dev/null
+++ b/third_party/rust/id-arena/LICENSE-APACHE
@@ -0,0 +1,201 @@
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diff --git a/third_party/rust/id-arena/LICENSE-MIT b/third_party/rust/id-arena/LICENSE-MIT
new file mode 100644
index 0000000000..39e0ed6602
--- /dev/null
+++ b/third_party/rust/id-arena/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2014 Alex Crichton
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
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+publish, distribute, sublicense, and/or sell copies of
+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
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/third_party/rust/id-arena/README.md b/third_party/rust/id-arena/README.md
new file mode 100644
index 0000000000..a783f1ce0b
--- /dev/null
+++ b/third_party/rust/id-arena/README.md
@@ -0,0 +1,100 @@
+# `id-arena`
+
+[![](https://img.shields.io/crates/v/id-arena.svg)](https://crates.io/crates/id-arena)
+[![](https://img.shields.io/crates/d/id-arena.svg)](https://crates.io/crates/id-arena)
+[![Travis CI Build Status](https://travis-ci.org/fitzgen/id-arena.svg?branch=master)](https://travis-ci.org/fitzgen/id-arena)
+
+A simple, id-based arena.
+
+### Id-based
+
+Allocate objects and get an identifier for that object back, *not* a
+reference to the allocated object. Given an id, you can get a shared or
+exclusive reference to the allocated object from the arena. This id-based
+approach is useful for constructing mutable graph data structures.
+
+If you want allocation to return a reference, consider [the `typed-arena`
+crate](https://github.com/SimonSapin/rust-typed-arena/) instead.
+
+### No Deletion
+
+This arena does not support deletion, which makes its implementation simple
+and allocation fast. If you want deletion, you need a way to solve the ABA
+problem. Consider using [the `generational-arena`
+crate](https://github.com/fitzgen/generational-arena) instead.
+
+### Homogeneous
+
+This crate's arenas can only contain objects of a single type `T`. If you
+need an arena of objects with heterogeneous types, consider another crate.
+
+### `#![no_std]` Support
+
+Requires the `alloc` nightly feature. Disable the on-by-default `"std"` feature:
+
+```toml
+[dependencies.id-arena]
+version = "2"
+default-features = false
+```
+
+### `rayon` Support
+
+If the `rayon` feature of this crate is activated:
+
+```toml
+[dependencies]
+id-arena = { version = "2", features = ["rayon"] }
+```
+
+then you can use [`rayon`](https://crates.io/crates/rayon)'s support for
+parallel iteration. The `Arena` type will have a `par_iter` family of
+methods where appropriate.
+
+### Example
+
+```rust
+use id_arena::{Arena, Id};
+
+type AstNodeId = Id<AstNode>;
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum AstNode {
+    Const(i64),
+    Var(String),
+    Add {
+        lhs: AstNodeId,
+        rhs: AstNodeId,
+    },
+    Sub {
+        lhs: AstNodeId,
+        rhs: AstNodeId,
+    },
+    Mul {
+        lhs: AstNodeId,
+        rhs: AstNodeId,
+    },
+    Div {
+        lhs: AstNodeId,
+        rhs: AstNodeId,
+    },
+}
+
+let mut ast_nodes = Arena::<AstNode>::new();
+
+// Create the AST for `a * (b + 3)`.
+let three = ast_nodes.alloc(AstNode::Const(3));
+let b = ast_nodes.alloc(AstNode::Var("b".into()));
+let b_plus_three = ast_nodes.alloc(AstNode::Add {
+    lhs: b,
+    rhs: three,
+});
+let a = ast_nodes.alloc(AstNode::Var("a".into()));
+let a_times_b_plus_three = ast_nodes.alloc(AstNode::Mul {
+    lhs: a,
+    rhs: b_plus_three,
+});
+
+// Can use indexing to access allocated nodes.
+assert_eq!(ast_nodes[three], AstNode::Const(3));
+```
diff --git a/third_party/rust/id-arena/README.tpl b/third_party/rust/id-arena/README.tpl
new file mode 100644
index 0000000000..56c38d5f08
--- /dev/null
+++ b/third_party/rust/id-arena/README.tpl
@@ -0,0 +1,3 @@
+# `{{crate}}`
+
+{{readme}}
diff --git a/third_party/rust/id-arena/src/lib.rs b/third_party/rust/id-arena/src/lib.rs
new file mode 100644
index 0000000000..0c0edd4e60
--- /dev/null
+++ b/third_party/rust/id-arena/src/lib.rs
@@ -0,0 +1,726 @@
+//! [![](https://img.shields.io/crates/v/id-arena.svg)](https://crates.io/crates/id-arena)
+//! [![](https://img.shields.io/crates/d/id-arena.svg)](https://crates.io/crates/id-arena)
+//! [![Travis CI Build Status](https://travis-ci.org/fitzgen/id-arena.svg?branch=master)](https://travis-ci.org/fitzgen/id-arena)
+//!
+//! A simple, id-based arena.
+//!
+//! ## Id-based
+//!
+//! Allocate objects and get an identifier for that object back, *not* a
+//! reference to the allocated object. Given an id, you can get a shared or
+//! exclusive reference to the allocated object from the arena. This id-based
+//! approach is useful for constructing mutable graph data structures.
+//!
+//! If you want allocation to return a reference, consider [the `typed-arena`
+//! crate](https://github.com/SimonSapin/rust-typed-arena/) instead.
+//!
+//! ## No Deletion
+//!
+//! This arena does not support deletion, which makes its implementation simple
+//! and allocation fast. If you want deletion, you need a way to solve the ABA
+//! problem. Consider using [the `generational-arena`
+//! crate](https://github.com/fitzgen/generational-arena) instead.
+//!
+//! ## Homogeneous
+//!
+//! This crate's arenas can only contain objects of a single type `T`. If you
+//! need an arena of objects with heterogeneous types, consider another crate.
+//!
+//! ## `#![no_std]` Support
+//!
+//! Requires the `alloc` nightly feature. Disable the on-by-default `"std"` feature:
+//!
+//! ```toml
+//! [dependencies.id-arena]
+//! version = "2"
+//! default-features = false
+//! ```
+//!
+//! ## `rayon` Support
+//!
+//! If the `rayon` feature of this crate is activated:
+//!
+//! ```toml
+//! [dependencies]
+//! id-arena = { version = "2", features = ["rayon"] }
+//! ```
+//!
+//! then you can use [`rayon`](https://crates.io/crates/rayon)'s support for
+//! parallel iteration. The `Arena` type will have a `par_iter` family of
+//! methods where appropriate.
+//!
+//! ## Example
+//!
+//! ```rust
+//! use id_arena::{Arena, Id};
+//!
+//! type AstNodeId = Id<AstNode>;
+//!
+//! #[derive(Debug, Eq, PartialEq)]
+//! pub enum AstNode {
+//!     Const(i64),
+//!     Var(String),
+//!     Add {
+//!         lhs: AstNodeId,
+//!         rhs: AstNodeId,
+//!     },
+//!     Sub {
+//!         lhs: AstNodeId,
+//!         rhs: AstNodeId,
+//!     },
+//!     Mul {
+//!         lhs: AstNodeId,
+//!         rhs: AstNodeId,
+//!     },
+//!     Div {
+//!         lhs: AstNodeId,
+//!         rhs: AstNodeId,
+//!     },
+//! }
+//!
+//! let mut ast_nodes = Arena::<AstNode>::new();
+//!
+//! // Create the AST for `a * (b + 3)`.
+//! let three = ast_nodes.alloc(AstNode::Const(3));
+//! let b = ast_nodes.alloc(AstNode::Var("b".into()));
+//! let b_plus_three = ast_nodes.alloc(AstNode::Add {
+//!     lhs: b,
+//!     rhs: three,
+//! });
+//! let a = ast_nodes.alloc(AstNode::Var("a".into()));
+//! let a_times_b_plus_three = ast_nodes.alloc(AstNode::Mul {
+//!     lhs: a,
+//!     rhs: b_plus_three,
+//! });
+//!
+//! // Can use indexing to access allocated nodes.
+//! assert_eq!(ast_nodes[three], AstNode::Const(3));
+//! ```
+
+#![forbid(unsafe_code)]
+#![deny(missing_debug_implementations)]
+#![deny(missing_docs)]
+// In no-std mode, use the alloc crate to get `Vec`.
+#![no_std]
+#![cfg_attr(not(feature = "std"), feature(alloc))]
+
+use core::cmp::Ordering;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::iter;
+use core::marker::PhantomData;
+use core::ops;
+use core::slice;
+use core::sync::atomic::{self, AtomicUsize, ATOMIC_USIZE_INIT};
+
+#[cfg(not(feature = "std"))]
+extern crate alloc;
+#[cfg(not(feature = "std"))]
+use alloc::vec::{self, Vec};
+
+#[cfg(feature = "std")]
+extern crate std;
+#[cfg(feature = "std")]
+use std::vec::{self, Vec};
+
+#[cfg(feature = "rayon")]
+mod rayon;
+#[cfg(feature = "rayon")]
+pub use rayon::*;
+
+/// A trait representing the implementation behavior of an arena and how
+/// identifiers are represented.
+///
+/// ## When should I implement `ArenaBehavior` myself?
+///
+/// Usually, you should just use `DefaultArenaBehavior`, which is simple and
+/// correct. However, there are some scenarios where you might want to implement
+/// `ArenaBehavior` yourself:
+///
+/// * **Space optimizations:** The default identifier is two words in size,
+/// which is larger than is usually necessary. For example, if you know that an
+/// arena *cannot* contain more than 256 items, you could make your own
+/// identifier type that stores the index as a `u8` and then you can save some
+/// space.
+///
+/// * **Trait Coherence:** If you need to implement an upstream crate's traits
+/// for identifiers, then defining your own identifier type allows you to work
+/// with trait coherence rules.
+///
+/// * **Share identifiers across arenas:** You can coordinate and share
+/// identifiers across different arenas to enable a "struct of arrays" style
+/// data representation.
+pub trait ArenaBehavior {
+    /// The identifier type.
+    type Id: Copy;
+
+    /// Construct a new object identifier from the given index and arena
+    /// identifier.
+    ///
+    /// ## Panics
+    ///
+    /// Implementations are allowed to panic if the given index is larger than
+    /// the underlying storage (e.g. the implementation uses a `u8` for storing
+    /// indices and the given index value is larger than 255).
+    fn new_id(arena_id: u32, index: usize) -> Self::Id;
+
+    /// Get the given identifier's index.
+    fn index(Self::Id) -> usize;
+
+    /// Get the given identifier's arena id.
+    fn arena_id(Self::Id) -> u32;
+
+    /// Construct a new arena identifier.
+    ///
+    /// This is used to disambiguate `Id`s across different arenas. To make
+    /// identifiers with the same index from different arenas compare false for
+    /// equality, return a unique `u32` on every invocation. This is the
+    /// default, provided implementation's behavior.
+    ///
+    /// To make identifiers with the same index from different arenas compare
+    /// true for equality, return the same `u32` on every invocation.
+    fn new_arena_id() -> u32 {
+        static ARENA_COUNTER: AtomicUsize = ATOMIC_USIZE_INIT;
+        ARENA_COUNTER.fetch_add(1, atomic::Ordering::SeqCst) as u32
+    }
+}
+
+/// An identifier for an object allocated within an arena.
+pub struct Id<T> {
+    idx: usize,
+    arena_id: u32,
+    _ty: PhantomData<fn() -> T>,
+}
+
+impl<T> fmt::Debug for Id<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Id").field("idx", &self.idx).finish()
+    }
+}
+
+impl<T> Copy for Id<T> {}
+
+impl<T> Clone for Id<T> {
+    #[inline]
+    fn clone(&self) -> Id<T> {
+        *self
+    }
+}
+
+impl<T> PartialEq for Id<T> {
+    #[inline]
+    fn eq(&self, rhs: &Self) -> bool {
+        self.arena_id == rhs.arena_id && self.idx == rhs.idx
+    }
+}
+
+impl<T> Eq for Id<T> {}
+
+impl<T> Hash for Id<T> {
+    #[inline]
+    fn hash<H: Hasher>(&self, h: &mut H) {
+        self.arena_id.hash(h);
+        self.idx.hash(h);
+    }
+}
+
+impl<T> PartialOrd for Id<T> {
+    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
+        Some(self.cmp(rhs))
+    }
+}
+
+impl<T> Ord for Id<T> {
+    fn cmp(&self, rhs: &Self) -> Ordering {
+        self.arena_id
+            .cmp(&rhs.arena_id)
+            .then(self.idx.cmp(&rhs.idx))
+    }
+}
+
+impl<T> Id<T> {
+    /// Get the index within the arena that this id refers to.
+    #[inline]
+    pub fn index(&self) -> usize {
+        self.idx
+    }
+}
+
+/// The default `ArenaBehavior` implementation.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DefaultArenaBehavior<T> {
+    _phantom: PhantomData<fn() -> T>,
+}
+
+impl<T> ArenaBehavior for DefaultArenaBehavior<T> {
+    type Id = Id<T>;
+
+    #[inline]
+    fn new_id(arena_id: u32, idx: usize) -> Self::Id {
+        Id {
+            idx,
+            arena_id,
+            _ty: PhantomData,
+        }
+    }
+
+    #[inline]
+    fn index(id: Self::Id) -> usize {
+        id.idx
+    }
+
+    #[inline]
+    fn arena_id(id: Self::Id) -> u32 {
+        id.arena_id
+    }
+}
+
+/// An arena of objects of type `T`.
+///
+/// ```
+/// use id_arena::Arena;
+///
+/// let mut arena = Arena::<&str>::new();
+///
+/// let a = arena.alloc("Albert");
+/// assert_eq!(arena[a], "Albert");
+///
+/// arena[a] = "Alice";
+/// assert_eq!(arena[a], "Alice");
+/// ```
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Arena<T, A = DefaultArenaBehavior<T>> {
+    arena_id: u32,
+    items: Vec<T>,
+    _phantom: PhantomData<fn() -> A>,
+}
+
+impl<T, A> Default for Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    #[inline]
+    fn default() -> Arena<T, A> {
+        Arena {
+            arena_id: A::new_arena_id(),
+            items: Vec::new(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<T, A> Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    /// Construct a new, empty `Arena`.
+    ///
+    /// ```
+    /// use id_arena::Arena;
+    ///
+    /// let mut arena = Arena::<usize>::new();
+    /// arena.alloc(42);
+    /// ```
+    #[inline]
+    pub fn new() -> Arena<T, A> {
+        Default::default()
+    }
+
+    /// Construct a new, empty `Arena` with capacity for the given number of
+    /// elements.
+    ///
+    /// ```
+    /// use id_arena::Arena;
+    ///
+    /// let mut arena = Arena::<usize>::with_capacity(100);
+    /// for x in 0..100 {
+    ///     arena.alloc(x * x);
+    /// }
+    /// ```
+    #[inline]
+    pub fn with_capacity(capacity: usize) -> Arena<T, A> {
+        Arena {
+            arena_id: A::new_arena_id(),
+            items: Vec::with_capacity(capacity),
+            _phantom: PhantomData,
+        }
+    }
+
+    /// Allocate `item` within this arena and return its id.
+    ///
+    /// ```
+    /// use id_arena::Arena;
+    ///
+    /// let mut arena = Arena::<usize>::new();
+    /// let _id = arena.alloc(42);
+    /// ```
+    ///
+    /// ## Panics
+    ///
+    /// Panics if the number of elements in the arena overflows a `usize` or
+    /// `Id`'s index storage representation.
+    #[inline]
+    pub fn alloc(&mut self, item: T) -> A::Id {
+        let id = self.next_id();
+        self.items.push(item);
+        id
+    }
+
+    /// Allocate an item with the id that it will be assigned.
+    ///
+    /// This is useful for structures that want to store their id as their own
+    /// member.
+    ///
+    /// ```
+    /// use id_arena::{Arena, Id};
+    ///
+    /// struct Cat {
+    ///     id: Id<Cat>,
+    /// }
+    ///
+    /// let mut arena = Arena::<Cat>::new();
+    ///
+    /// let kitty = arena.alloc_with_id(|id| Cat { id });
+    /// assert_eq!(arena[kitty].id, kitty);
+    /// ```
+    #[inline]
+    pub fn alloc_with_id(&mut self, f: impl FnOnce(A::Id) -> T) -> A::Id {
+        let id = self.next_id();
+        let val = f(id);
+        self.alloc(val)
+    }
+
+    /// Get the id that will be used for the next item allocated into this
+    /// arena.
+    ///
+    /// If you are allocating a `struct` that wants to have its id as a member
+    /// of itself, prefer the less error-prone `Arena::alloc_with_id` method.
+    #[inline]
+    pub fn next_id(&self) -> A::Id {
+        let arena_id = self.arena_id;
+        let idx = self.items.len();
+        A::new_id(arena_id, idx)
+    }
+
+    /// Get a shared reference to the object associated with the given `id` if
+    /// it exists.
+    ///
+    /// If there is no object associated with `id` (for example, it might
+    /// reference an object allocated within a different arena) then return
+    /// `None`.
+    ///
+    /// ```
+    /// use id_arena::Arena;
+    ///
+    /// let mut arena = Arena::<usize>::new();
+    /// let id = arena.alloc(42);
+    /// assert!(arena.get(id).is_some());
+    ///
+    /// let other_arena = Arena::<usize>::new();
+    /// assert!(other_arena.get(id).is_none());
+    /// ```
+    #[inline]
+    pub fn get(&self, id: A::Id) -> Option<&T> {
+        if A::arena_id(id) != self.arena_id {
+            None
+        } else {
+            self.items.get(A::index(id))
+        }
+    }
+
+    /// Get an exclusive reference to the object associated with the given `id`
+    /// if it exists.
+    ///
+    /// If there is no object associated with `id` (for example, it might
+    /// reference an object allocated within a different arena) then return
+    /// `None`.
+    ///
+    /// ```
+    /// use id_arena::Arena;
+    ///
+    /// let mut arena = Arena::<usize>::new();
+    /// let id = arena.alloc(42);
+    /// assert!(arena.get_mut(id).is_some());
+    ///
+    /// let mut other_arena = Arena::<usize>::new();
+    /// assert!(other_arena.get_mut(id).is_none());
+    /// ```
+    #[inline]
+    pub fn get_mut(&mut self, id: A::Id) -> Option<&mut T> {
+        if A::arena_id(id) != self.arena_id {
+            None
+        } else {
+            self.items.get_mut(A::index(id))
+        }
+    }
+
+    /// Iterate over this arena's items and their ids.
+    ///
+    /// ```
+    /// use id_arena::Arena;
+    ///
+    /// let mut arena = Arena::<&str>::new();
+    ///
+    /// arena.alloc("hello");
+    /// arena.alloc("hi");
+    /// arena.alloc("yo");
+    ///
+    /// for (id, s) in arena.iter() {
+    ///     assert_eq!(arena.get(id).unwrap(), s);
+    ///     println!("{:?} -> {}", id, s);
+    /// }
+    /// ```
+    #[inline]
+    pub fn iter(&self) -> Iter<T, A> {
+        IntoIterator::into_iter(self)
+    }
+
+    /// Iterate over this arena's items and their ids, allowing mutation of each
+    /// item.
+    #[inline]
+    pub fn iter_mut(&mut self) -> IterMut<T, A> {
+        IntoIterator::into_iter(self)
+    }
+
+    /// Get the number of objects allocated in this arena.
+    ///
+    /// ```
+    /// use id_arena::Arena;
+    ///
+    /// let mut arena = Arena::<&str>::new();
+    ///
+    /// arena.alloc("hello");
+    /// arena.alloc("hi");
+    ///
+    /// assert_eq!(arena.len(), 2);
+    /// ```
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.items.len()
+    }
+}
+
+impl<T, A> ops::Index<A::Id> for Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    type Output = T;
+
+    #[inline]
+    fn index(&self, id: A::Id) -> &T {
+        assert_eq!(self.arena_id, A::arena_id(id));
+        &self.items[A::index(id)]
+    }
+}
+
+impl<T, A> ops::IndexMut<A::Id> for Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    #[inline]
+    fn index_mut(&mut self, id: A::Id) -> &mut T {
+        assert_eq!(self.arena_id, A::arena_id(id));
+        &mut self.items[A::index(id)]
+    }
+}
+
+fn add_id<A, T>(item: Option<(usize, T)>, arena_id: u32) -> Option<(A::Id, T)>
+where
+    A: ArenaBehavior,
+{
+    item.map(|(idx, item)| (A::new_id(arena_id, idx), item))
+}
+
+/// An iterator over `(Id, &T)` pairs in an arena.
+///
+/// See [the `Arena::iter()` method](./struct.Arena.html#method.iter) for details.
+#[derive(Debug)]
+pub struct Iter<'a, T: 'a, A: 'a> {
+    arena_id: u32,
+    iter: iter::Enumerate<slice::Iter<'a, T>>,
+    _phantom: PhantomData<fn() -> A>,
+}
+
+impl<'a, T: 'a, A: 'a> Iterator for Iter<'a, T, A>
+where
+    A: ArenaBehavior,
+{
+    type Item = (A::Id, &'a T);
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        add_id::<A, _>(self.iter.next(), self.arena_id)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a, T: 'a, A: 'a> DoubleEndedIterator for Iter<'a, T, A>
+where
+    A: ArenaBehavior,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        add_id::<A, _>(self.iter.next_back(), self.arena_id)
+    }
+}
+
+impl<'a, T: 'a, A: 'a> ExactSizeIterator for Iter<'a, T, A>
+where
+    A: ArenaBehavior,
+{
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<'a, T, A> IntoIterator for &'a Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    type Item = (A::Id, &'a T);
+    type IntoIter = Iter<'a, T, A>;
+
+    #[inline]
+    fn into_iter(self) -> Iter<'a, T, A> {
+        Iter {
+            arena_id: self.arena_id,
+            iter: self.items.iter().enumerate(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+/// An iterator over `(Id, &mut T)` pairs in an arena.
+///
+/// See [the `Arena::iter_mut()` method](./struct.Arena.html#method.iter_mut)
+/// for details.
+#[derive(Debug)]
+pub struct IterMut<'a, T: 'a, A: 'a> {
+    arena_id: u32,
+    iter: iter::Enumerate<slice::IterMut<'a, T>>,
+    _phantom: PhantomData<fn() -> A>,
+}
+
+impl<'a, T: 'a, A: 'a> Iterator for IterMut<'a, T, A>
+where
+    A: ArenaBehavior,
+{
+    type Item = (A::Id, &'a mut T);
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        add_id::<A, _>(self.iter.next(), self.arena_id)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a, T: 'a, A: 'a> DoubleEndedIterator for IterMut<'a, T, A>
+where
+    A: ArenaBehavior,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        add_id::<A, _>(self.iter.next_back(), self.arena_id)
+    }
+}
+
+impl<'a, T: 'a, A: 'a> ExactSizeIterator for IterMut<'a, T, A>
+where
+    A: ArenaBehavior,
+{
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<'a, T, A> IntoIterator for &'a mut Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    type Item = (A::Id, &'a mut T);
+    type IntoIter = IterMut<'a, T, A>;
+
+    #[inline]
+    fn into_iter(self) -> IterMut<'a, T, A> {
+        IterMut {
+            arena_id: self.arena_id,
+            iter: self.items.iter_mut().enumerate(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+/// An iterator over `(Id, T)` pairs in an arena.
+#[derive(Debug)]
+pub struct IntoIter<T, A> {
+    arena_id: u32,
+    iter: iter::Enumerate<vec::IntoIter<T>>,
+    _phantom: PhantomData<fn() -> A>,
+}
+
+impl<T, A> Iterator for IntoIter<T, A>
+where
+    A: ArenaBehavior,
+{
+    type Item = (A::Id, T);
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        add_id::<A, _>(self.iter.next(), self.arena_id)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<T, A> DoubleEndedIterator for IntoIter<T, A>
+where
+    A: ArenaBehavior,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        add_id::<A, _>(self.iter.next_back(), self.arena_id)
+    }
+}
+
+impl<T, A> ExactSizeIterator for IntoIter<T, A>
+where
+    A: ArenaBehavior,
+{
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<T, A> IntoIterator for Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    type Item = (A::Id, T);
+    type IntoIter = IntoIter<T, A>;
+
+    #[inline]
+    fn into_iter(self) -> IntoIter<T, A> {
+        IntoIter {
+            arena_id: self.arena_id,
+            iter: self.items.into_iter().enumerate(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn ids_are_send_sync() {
+        fn assert_send_sync<T: Send + Sync>() {}
+        struct Foo;
+        assert_send_sync::<Id<Foo>>();
+    }
+}
diff --git a/third_party/rust/id-arena/src/rayon.rs b/third_party/rust/id-arena/src/rayon.rs
new file mode 100644
index 0000000000..7bea702247
--- /dev/null
+++ b/third_party/rust/id-arena/src/rayon.rs
@@ -0,0 +1,282 @@
+extern crate rayon;
+
+use self::rayon::iter::plumbing::{Consumer, UnindexedConsumer};
+use self::rayon::iter::plumbing::ProducerCallback;
+use self::rayon::prelude::*;
+use super::*;
+
+impl<T, A> Arena<T, A>
+where
+    A: ArenaBehavior,
+{
+    /// Returns an iterator of shared references which can be used to iterate
+    /// over this arena in parallel with the `rayon` crate.
+    ///
+    /// # Features
+    ///
+    /// This API requires the `rayon` feature of this crate to be enabled.
+    pub fn par_iter(&self) -> ParIter<T, A>
+    where
+        T: Sync,
+        A::Id: Send,
+    {
+        ParIter {
+            arena_id: self.arena_id,
+            iter: self.items.par_iter().enumerate(),
+            _phantom: PhantomData,
+        }
+    }
+
+    /// Returns an iterator of mutable references which can be used to iterate
+    /// over this arena in parallel with the `rayon` crate.
+    ///
+    /// # Features
+    ///
+    /// This API requires the `rayon` feature of this crate to be enabled.
+    pub fn par_iter_mut(&mut self) -> ParIterMut<T, A>
+    where
+        T: Send + Sync,
+        A::Id: Send,
+    {
+        ParIterMut {
+            arena_id: self.arena_id,
+            iter: self.items.par_iter_mut().enumerate(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+/// A parallel iterator over shared references in an arena.
+///
+/// See `Arena::par_iter` for more information.
+#[derive(Debug)]
+pub struct ParIter<'a, T, A>
+where
+    T: Sync,
+{
+    arena_id: u32,
+    iter: rayon::iter::Enumerate<rayon::slice::Iter<'a, T>>,
+    _phantom: PhantomData<fn() -> A>,
+}
+
+impl<'a, T, A> ParallelIterator for ParIter<'a, T, A>
+where
+    T: Sync,
+    A: ArenaBehavior,
+    A::Id: Send,
+{
+    type Item = (A::Id, &'a T);
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .drive_unindexed(consumer)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        self.iter.opt_len()
+    }
+}
+
+impl<'a, T, A> IndexedParallelIterator for ParIter<'a, T, A>
+where
+    T: Sync,
+    A: ArenaBehavior,
+    A::Id: Send,
+{
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .drive(consumer)
+    }
+
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .with_producer(callback)
+    }
+}
+
+impl<'data, T, A> IntoParallelIterator for &'data Arena<T, A>
+    where A: ArenaBehavior,
+          A::Id: Send,
+          T: Sync,
+{
+    type Item = (A::Id, &'data T);
+    type Iter = ParIter<'data, T, A>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        self.par_iter()
+    }
+}
+
+/// A parallel iterator over mutable references in an arena.
+///
+/// See `Arena::par_iter_mut` for more information.
+#[derive(Debug)]
+pub struct ParIterMut<'a, T, A>
+where
+    T: Send + Sync,
+{
+    arena_id: u32,
+    iter: rayon::iter::Enumerate<rayon::slice::IterMut<'a, T>>,
+    _phantom: PhantomData<fn() -> A>,
+}
+
+impl<'a, T, A> ParallelIterator for ParIterMut<'a, T, A>
+where
+    T: Send + Sync,
+    A: ArenaBehavior,
+    A::Id: Send,
+{
+    type Item = (A::Id, &'a mut T);
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .drive_unindexed(consumer)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        self.iter.opt_len()
+    }
+}
+
+impl<'a, T, A> IndexedParallelIterator for ParIterMut<'a, T, A>
+where
+    T: Send + Sync,
+    A: ArenaBehavior,
+    A::Id: Send,
+{
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .drive(consumer)
+    }
+
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .with_producer(callback)
+    }
+}
+
+impl<'data, T, A> IntoParallelIterator for &'data mut Arena<T, A>
+    where A: ArenaBehavior,
+          A::Id: Send,
+          T: Send + Sync,
+{
+    type Item = (A::Id, &'data mut T);
+    type Iter = ParIterMut<'data, T, A>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        self.par_iter_mut()
+    }
+}
+
+/// A parallel iterator over items in an arena.
+///
+/// See `Arena::into_par_iter` for more information.
+#[derive(Debug)]
+pub struct IntoParIter<T, A>
+where
+    T: Send,
+{
+    arena_id: u32,
+    iter: rayon::iter::Enumerate<rayon::vec::IntoIter<T>>,
+    _phantom: PhantomData<fn() -> A>,
+}
+
+impl<T, A> ParallelIterator for IntoParIter<T, A>
+where
+    T: Send,
+    A: ArenaBehavior,
+    A::Id: Send,
+{
+    type Item = (A::Id, T);
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .drive_unindexed(consumer)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        self.iter.opt_len()
+    }
+}
+
+impl<T, A> IndexedParallelIterator for IntoParIter<T, A>
+where
+    T: Send,
+    A: ArenaBehavior,
+    A::Id: Send,
+{
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .drive(consumer)
+    }
+
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        let arena_id = self.arena_id;
+        self.iter.map(|(i, item)| (A::new_id(arena_id, i), item))
+            .with_producer(callback)
+    }
+}
+
+impl<T, A> IntoParallelIterator for Arena<T, A>
+    where A: ArenaBehavior,
+          A::Id: Send,
+          T: Send,
+{
+    type Item = (A::Id, T);
+    type Iter = IntoParIter<T, A>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        IntoParIter {
+            arena_id: self.arena_id,
+            iter: self.items.into_par_iter().enumerate(),
+            _phantom: PhantomData,
+        }
+    }
+}
diff --git a/third_party/rust/id-arena/tests/readme_up_to_date.rs b/third_party/rust/id-arena/tests/readme_up_to_date.rs
new file mode 100644
index 0000000000..38af909e31
--- /dev/null
+++ b/third_party/rust/id-arena/tests/readme_up_to_date.rs
@@ -0,0 +1,22 @@
+use std::fs;
+use std::process::Command;
+
+#[test]
+fn cargo_readme_up_to_date() {
+    println!("Checking that `cargo readme > README.md` is up to date...");
+
+    let expected = Command::new("cargo")
+        .arg("readme")
+        .current_dir(env!("CARGO_MANIFEST_DIR"))
+        .output()
+        .expect("should run `cargo readme` OK")
+        .stdout;
+    let expected = String::from_utf8_lossy(&expected);
+
+    let actual = fs::read_to_string(concat!(env!("CARGO_MANIFEST_DIR"), "/README.md"))
+        .expect("should read README.md OK");
+
+    if actual != expected {
+        panic!("Run `cargo readme > README.md` to update README.md");
+    }
+}