Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

10 files changed, 1133 insertions, 0 deletions

diff --git a/third_party/rust/static_assertions/src/assert_cfg.rs b/third_party/rust/static_assertions/src/assert_cfg.rs
new file mode 100644
index 0000000000..24282c1f32
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_cfg.rs
@@ -0,0 +1,49 @@
+/// Asserts that a given configuration is set.
+///
+/// # Examples
+///
+/// A project will simply fail to compile if the given configuration is not set.
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// // We're not masochists
+/// # #[cfg(not(target_pointer_width = "16"))] // Just in case
+/// assert_cfg!(not(target_pointer_width = "16"));
+/// ```
+///
+/// If a project does not support a set of configurations, you may want to
+/// report why. There is the option of providing a compile error message string:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// # #[cfg(any(unix, windows))]
+/// assert_cfg!(any(unix, windows), "There is only support for Unix or Windows");
+///
+/// // User needs to specify a database back-end
+/// # #[cfg(target_pointer_width = "0")] // Impossible
+/// assert_cfg!(all(not(all(feature = "mysql", feature = "mongodb")),
+///                 any(    feature = "mysql", feature = "mongodb")),
+///             "Must exclusively use MySQL or MongoDB as database back-end");
+/// ```
+///
+/// Some configurations are impossible. For example, we can't be compiling for
+/// both macOS _and_ Windows simultaneously:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_cfg!(all(target_os = "macos",
+///                 target_os = "windows"),
+///             "No, that's not how it works! ಠ_ಠ");
+/// ```
+#[macro_export]
+macro_rules! assert_cfg {
+    () => {};
+    ($($cfg:meta)+, $msg:expr $(,)?) => {
+        #[cfg(not($($cfg)+))]
+        compile_error!($msg);
+    };
+    ($($cfg:tt)*) => {
+        #[cfg(not($($cfg)*))]
+        compile_error!(concat!("Cfg does not pass: ", stringify!($($cfg)*)));
+    };
+}
diff --git a/third_party/rust/static_assertions/src/assert_eq_align.rs b/third_party/rust/static_assertions/src/assert_eq_align.rs
new file mode 100644
index 0000000000..69412daefb
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_eq_align.rs
@@ -0,0 +1,45 @@
+/// Asserts that types are equal in alignment.
+///
+/// This is useful when ensuring that pointer arithmetic is done correctly, or
+/// when [FFI] requires a type to have the same alignment as some foreign type.
+///
+/// # Examples
+///
+/// A `usize` has the same alignment as any pointer type:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_eq_align!(usize, *const u8, *mut u8);
+/// ```
+///
+/// The following passes because `[i32; 4]` has the same alignment as `i32`:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_eq_align!([i32; 4], i32);
+/// ```
+///
+/// The following example fails to compile because `i32x4` explicitly has 4
+/// times the alignment as `[i32; 4]`:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// # #[allow(non_camel_case_types)]
+/// #[repr(align(16))]
+/// struct i32x4([i32; 4]);
+///
+/// assert_eq_align!(i32x4, [i32; 4]);
+/// ```
+///
+/// [FFI]: https://en.wikipedia.org/wiki/Foreign_function_interface
+#[macro_export]
+macro_rules! assert_eq_align {
+    ($x:ty, $($xs:ty),+ $(,)?) => {
+        const _: fn() = || {
+            // Assigned instance must match the annotated type or else it will
+            // fail to compile
+            use $crate::_core::mem::align_of;
+            $(let _: [(); align_of::<$x>()] = [(); align_of::<$xs>()];)+
+        };
+    };
+}
diff --git a/third_party/rust/static_assertions/src/assert_eq_size.rs b/third_party/rust/static_assertions/src/assert_eq_size.rs
new file mode 100644
index 0000000000..9c3c4901c7
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_eq_size.rs
@@ -0,0 +1,123 @@
+/// Asserts that types are equal in size.
+///
+/// When performing operations such as pointer casts or dealing with [`usize`]
+/// versus [`u64`] versus [`u32`], the size of your types matter. That is where
+/// this macro comes into play.
+///
+/// # Alternatives
+///
+/// There also exists [`assert_eq_size_val`](macro.assert_eq_size_val.html) and
+/// [`assert_eq_size_ptr`](macro.assert_eq_size_ptr.html). Instead of specifying
+/// types to compare, values' sizes can be directly compared against each other.
+///
+/// # Examples
+///
+/// These three types, despite being very different, all have the same size:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_eq_size!([u8; 4], (u16, u16), u32);
+/// ```
+///
+/// The following example fails to compile because `u32` has 4 times the size of
+/// `u8`:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_eq_size!(u32, u8);
+/// ```
+///
+/// [`usize`]: https://doc.rust-lang.org/std/primitive.usize.html
+/// [`u64`]: https://doc.rust-lang.org/std/primitive.u64.html
+/// [`u32`]: https://doc.rust-lang.org/std/primitive.u32.html
+#[macro_export]
+macro_rules! assert_eq_size {
+    ($x:ty, $($xs:ty),+ $(,)?) => {
+        const _: fn() = || {
+            $(let _ = $crate::_core::mem::transmute::<$x, $xs>;)+
+        };
+    };
+}
+
+/// Asserts that values pointed to are equal in size.
+///
+/// # Examples
+///
+/// This especially is useful for when coercing pointers between different types
+/// and ensuring the underlying values are the same size.
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// fn operation(x: &(u32, u32), y: &[u16; 4]) {
+///     assert_eq_size_ptr!(x, y);
+///     // ...
+/// }
+/// ```
+///
+/// The following example fails to compile because byte arrays of different
+/// lengths have different sizes:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions;
+/// # fn main() {
+/// static BYTES: &[u8; 4] = &[
+///     /* ... */
+///     # 0; 4
+/// ];
+///
+/// static TABLE: &[u8; 16] = &[
+///     /* ... */
+///     # 0; 16
+/// ];
+///
+/// assert_eq_size_ptr!(BYTES, TABLE);
+/// ```
+#[macro_export]
+macro_rules! assert_eq_size_ptr {
+    ($x:expr, $($xs:expr),+ $(,)?) => {
+        #[allow(unknown_lints, unsafe_code, forget_copy, useless_transmute)]
+        let _ = || unsafe {
+            use $crate::_core::{mem, ptr};
+            let mut copy = ptr::read($x);
+            $(ptr::write(&mut copy, mem::transmute(ptr::read($xs)));)+
+            mem::forget(copy);
+        };
+    }
+}
+
+/// Asserts that values are equal in size.
+///
+/// This macro doesn't consume its arguments and thus works for
+/// non-[`Clone`]able values.
+///
+/// # Examples
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions;
+/// # fn main() {
+/// struct Byte(u8);
+///
+/// let x = 10u8;
+/// let y = Byte(42); // Works for non-cloneable types
+///
+/// assert_eq_size_val!(x, y);
+/// assert_eq_size_val!(x, y, 0u8);
+/// # }
+/// ```
+///
+/// Even though both values are 0, they are of types with different sizes:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions;
+/// # fn main() {
+/// assert_eq_size_val!(0u8, 0u32);
+/// # }
+/// ```
+///
+/// [`Clone`]: https://doc.rust-lang.org/std/clone/trait.Clone.html
+#[macro_export(local_inner_macros)]
+macro_rules! assert_eq_size_val {
+    ($x:expr, $($xs:expr),+ $(,)?) => {
+        assert_eq_size_ptr!(&$x, $(&$xs),+);
+    }
+}
diff --git a/third_party/rust/static_assertions/src/assert_fields.rs b/third_party/rust/static_assertions/src/assert_fields.rs
new file mode 100644
index 0000000000..00f6242775
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_fields.rs
@@ -0,0 +1,72 @@
+/// Asserts that the type has the given fields.
+///
+/// # Examples
+///
+/// One common use case is when types have fields defined multiple times as a
+/// result of `#[cfg]`. This can be an issue when exposing a public API.
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions;
+/// pub struct Ty {
+///     #[cfg(windows)]
+///     pub val1: u8,
+///     #[cfg(not(windows))]
+///     pub val1: usize,
+///
+///     #[cfg(unix)]
+///     pub val2: u32,
+///     #[cfg(not(unix))]
+///     pub val2: usize,
+/// }
+///
+/// // Always have `val2` regardless of OS
+/// assert_fields!(Ty: val2);
+/// ```
+///
+/// This macro even works with `enum` variants:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// enum Data {
+///     Val {
+///         id: i32,
+///         name: String,
+///         bytes: [u8; 128],
+///     },
+///     Ptr(*const u8),
+/// }
+///
+/// assert_fields!(Data::Val: id, bytes);
+/// ```
+///
+/// The following example fails to compile because [`Range`] does not have a field named `middle`:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// use std::ops::Range;
+///
+/// assert_fields!(Range<u32>: middle);
+/// ```
+///
+/// [`Range`]: https://doc.rust-lang.org/std/ops/struct.Range.html
+#[macro_export]
+macro_rules! assert_fields {
+    ($t:ident::$v:ident: $($f:ident),+) => {
+        #[allow(unknown_lints, unneeded_field_pattern)]
+        const _: fn() = || {
+            #[allow(dead_code, unreachable_patterns)]
+            fn assert(value: $t) {
+                match value {
+                    $($t::$v { $f: _, .. } => {},)+
+                    _ => {}
+                }
+            }
+        };
+    };
+    ($t:path: $($f:ident),+) => {
+        #[allow(unknown_lints, unneeded_field_pattern)]
+        const _: fn() = || {
+            $(let $t { $f: _, .. };)+
+        };
+    };
+}
diff --git a/third_party/rust/static_assertions/src/assert_impl.rs b/third_party/rust/static_assertions/src/assert_impl.rs
new file mode 100644
index 0000000000..480b6b6c61
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_impl.rs
@@ -0,0 +1,356 @@
+/// Asserts that the type implements exactly one in a set of traits.
+///
+/// Related:
+/// - [`assert_impl_any!`]
+/// - [`assert_impl_all!`]
+/// - [`assert_not_impl_all!`]
+/// - [`assert_not_impl_any!`]
+///
+/// # Examples
+///
+/// Given some type `Foo`, it is expected to implement either `Snap`, `Crackle`,
+/// or `Pop`:
+///
+/// ```compile_fail
+/// # use static_assertions::assert_impl_one; fn main() {}
+/// struct Foo;
+///
+/// trait Snap {}
+/// trait Crackle {}
+/// trait Pop {}
+///
+/// assert_impl_one!(Foo: Snap, Crackle, Pop);
+/// ```
+///
+/// If _only_ `Crackle` is implemented, the assertion passes:
+///
+/// ```
+/// # use static_assertions::assert_impl_one; fn main() {}
+/// # struct Foo;
+/// # trait Snap {}
+/// # trait Crackle {}
+/// # trait Pop {}
+/// impl Crackle for Foo {}
+///
+/// assert_impl_one!(Foo: Snap, Crackle, Pop);
+/// ```
+///
+/// If `Snap` or `Pop` is _also_ implemented, the assertion fails:
+///
+/// ```compile_fail
+/// # use static_assertions::assert_impl_one; fn main() {}
+/// # struct Foo;
+/// # trait Snap {}
+/// # trait Crackle {}
+/// # trait Pop {}
+/// # impl Crackle for Foo {}
+/// impl Pop for Foo {}
+///
+/// assert_impl_one!(Foo: Snap, Crackle, Pop);
+/// ```
+///
+/// [`assert_impl_any!`]:     macro.assert_impl_any.html
+/// [`assert_impl_all!`]:     macro.assert_impl_all.html
+/// [`assert_not_impl_all!`]: macro.assert_not_impl_all.html
+/// [`assert_not_impl_any!`]: macro.assert_not_impl_any.html
+#[macro_export]
+macro_rules! assert_impl_one {
+    ($x:ty: $($t:path),+ $(,)?) => {
+        const _: fn() = || {
+            // Generic trait that must be implemented for `$x` exactly once.
+            trait AmbiguousIfMoreThanOne<A> {
+                // Required for actually being able to reference the trait.
+                fn some_item() {}
+            }
+
+            // Creates multiple scoped `Token` types for each trait `$t`, over
+            // which a specialized `AmbiguousIfMoreThanOne<Token>` is
+            // implemented for every type that implements `$t`.
+            $({
+                #[allow(dead_code)]
+                struct Token;
+
+                impl<T: ?Sized + $t> AmbiguousIfMoreThanOne<Token> for T {}
+            })+
+
+            // If there is only one specialized trait impl, type inference with
+            // `_` can be resolved and this can compile. Fails to compile if
+            // `$x` implements more than one `AmbiguousIfMoreThanOne<Token>` or
+            // does not implement any at all.
+            let _ = <$x as AmbiguousIfMoreThanOne<_>>::some_item;
+        };
+    };
+}
+
+/// Asserts that the type implements _all_ of the given traits.
+///
+/// See [`assert_not_impl_all!`] for achieving the opposite effect.
+///
+/// # Examples
+///
+/// This can be used to ensure types implement auto traits such as [`Send`] and
+/// [`Sync`], as well as traits with [blanket `impl`s][blanket].
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_impl_all!(u32: Copy, Send);
+/// assert_impl_all!(&str: Into<String>);
+/// ```
+///
+/// The following example fails to compile because raw pointers do not implement
+/// [`Send`] since they cannot be moved between threads safely:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_impl_all!(*const u8: Send);
+/// ```
+///
+/// [`assert_not_impl_all!`]: macro.assert_not_impl_all.html
+/// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
+/// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html
+/// [blanket]: https://doc.rust-lang.org/book/ch10-02-traits.html#using-trait-bounds-to-conditionally-implement-methods
+#[macro_export]
+macro_rules! assert_impl_all {
+    ($type:ty: $($trait:path),+ $(,)?) => {
+        const _: fn() = || {
+            // Only callable when `$type` implements all traits in `$($trait)+`.
+            fn assert_impl_all<T: ?Sized $(+ $trait)+>() {}
+            assert_impl_all::<$type>();
+        };
+    };
+}
+
+/// Asserts that the type implements _any_ of the given traits.
+///
+/// See [`assert_not_impl_any!`] for achieving the opposite effect.
+///
+/// # Examples
+///
+/// `u8` cannot be converted from `u16`, but it can be converted into `u16`:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_impl_any!(u8: From<u16>, Into<u16>);
+/// ```
+///
+/// The unit type cannot be converted from `u8` or `u16`, but it does implement
+/// [`Send`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_impl_any!((): From<u8>, From<u16>, Send);
+/// ```
+///
+/// The following example fails to compile because raw pointers do not implement
+/// [`Send`] or [`Sync`] since they cannot be moved or shared between threads
+/// safely:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_impl_any!(*const u8: Send, Sync);
+/// ```
+///
+/// [`assert_not_impl_any!`]: macro.assert_not_impl_any.html
+/// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
+/// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html
+#[macro_export]
+macro_rules! assert_impl_any {
+    ($x:ty: $($t:path),+ $(,)?) => {
+        const _: fn() = || {
+            use $crate::_core::marker::PhantomData;
+            use $crate::_core::ops::Deref;
+
+            // Fallback to use as the first iterative assignment to `previous`.
+            let previous = AssertImplAnyFallback;
+            struct AssertImplAnyFallback;
+
+            // Ensures that blanket traits can't impersonate the method. This
+            // prevents a false positive attack where---if a blanket trait is in
+            // scope that has `_static_assertions_impl_any`---the macro will
+            // compile when it shouldn't.
+            //
+            // See https://github.com/nvzqz/static-assertions-rs/issues/19 for
+            // more info.
+            struct ActualAssertImplAnyToken;
+            trait AssertImplAnyToken {}
+            impl AssertImplAnyToken for ActualAssertImplAnyToken {}
+            fn assert_impl_any_token<T: AssertImplAnyToken>(_: T) {}
+
+            $(let previous = {
+                struct Wrapper<T, N>(PhantomData<T>, N);
+
+                // If the method for this wrapper can't be called then the
+                // compiler will insert a deref and try again. This forwards the
+                // compiler's next attempt to the previous wrapper.
+                impl<T, N> Deref for Wrapper<T, N> {
+                    type Target = N;
+
+                    fn deref(&self) -> &Self::Target {
+                        &self.1
+                    }
+                }
+
+                // This impl is bounded on the `$t` trait, so the method can
+                // only be called if `$x` implements `$t`. This is why a new
+                // `Wrapper` is defined for each `previous`.
+                impl<T: $t, N> Wrapper<T, N> {
+                    fn _static_assertions_impl_any(&self) -> ActualAssertImplAnyToken {
+                        ActualAssertImplAnyToken
+                    }
+                }
+
+                Wrapper::<$x, _>(PhantomData, previous)
+            };)+
+
+            // Attempt to find the method that can actually be called. The found
+            // method must return a type that implements the sealed `Token`
+            // trait, this ensures that blanket trait methods can't cause this
+            // macro to compile.
+            assert_impl_any_token(previous._static_assertions_impl_any());
+        };
+    };
+}
+
+/// Asserts that the type does **not** implement _all_ of the given traits.
+///
+/// This can be used to ensure types do not implement auto traits such as
+/// [`Send`] and [`Sync`], as well as traits with [blanket `impl`s][blanket].
+///
+/// Note that the combination of all provided traits is required to not be
+/// implemented. If you want to check that none of multiple traits are
+/// implemented you should invoke [`assert_not_impl_any!`] instead.
+///
+/// # Examples
+///
+/// Although `u32` implements `From<u16>`, it does not implement `Into<usize>`:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_not_impl_all!(u32: From<u16>, Into<usize>);
+/// ```
+///
+/// The following example fails to compile since `u32` can be converted into
+/// `u64`.
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_not_impl_all!(u32: Into<u64>);
+/// ```
+///
+/// The following compiles because [`Cell`] is not both [`Sync`] _and_ [`Send`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// use std::cell::Cell;
+///
+/// assert_not_impl_all!(Cell<u32>: Sync, Send);
+/// ```
+///
+/// But it is [`Send`], so this fails to compile:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// # std::cell::Cell;
+/// assert_not_impl_all!(Cell<u32>: Send);
+/// ```
+///
+/// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
+/// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html
+/// [`assert_not_impl_any!`]: macro.assert_not_impl_any.html
+/// [`Cell`]: https://doc.rust-lang.org/std/cell/struct.Cell.html
+/// [blanket]: https://doc.rust-lang.org/book/ch10-02-traits.html#using-trait-bounds-to-conditionally-implement-methods
+#[macro_export]
+macro_rules! assert_not_impl_all {
+    ($x:ty: $($t:path),+ $(,)?) => {
+        const _: fn() = || {
+            // Generic trait with a blanket impl over `()` for all types.
+            trait AmbiguousIfImpl<A> {
+                // Required for actually being able to reference the trait.
+                fn some_item() {}
+            }
+
+            impl<T: ?Sized> AmbiguousIfImpl<()> for T {}
+
+            // Used for the specialized impl when *all* traits in
+            // `$($t)+` are implemented.
+            #[allow(dead_code)]
+            struct Invalid;
+
+            impl<T: ?Sized $(+ $t)+> AmbiguousIfImpl<Invalid> for T {}
+
+            // If there is only one specialized trait impl, type inference with
+            // `_` can be resolved and this can compile. Fails to compile if
+            // `$x` implements `AmbiguousIfImpl<Invalid>`.
+            let _ = <$x as AmbiguousIfImpl<_>>::some_item;
+        };
+    };
+}
+
+/// Asserts that the type does **not** implement _any_ of the given traits.
+///
+/// This can be used to ensure types do not implement auto traits such as
+/// [`Send`] and [`Sync`], as well as traits with [blanket `impl`s][blanket].
+///
+/// This macro causes a compilation failure if any of the provided individual
+/// traits are implemented for the type. If you want to check that a combination
+/// of traits is not implemented you should invoke [`assert_not_impl_all!`]
+/// instead. For single traits both macros behave the same.
+///
+/// # Examples
+///
+/// If `u32` were to implement `Into` conversions for `usize` _and_ for `u8`,
+/// the following would fail to compile:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_not_impl_any!(u32: Into<usize>, Into<u8>);
+/// ```
+///
+/// This is also good for simple one-off cases:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_not_impl_any!(&'static mut u8: Copy);
+/// ```
+///
+/// The following example fails to compile since `u32` can be converted into
+/// `u64` even though it can not be converted into a `u16`:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_not_impl_any!(u32: Into<u64>, Into<u16>);
+/// ```
+///
+/// [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
+/// [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html
+/// [`assert_not_impl_all!`]: macro.assert_not_impl_all.html
+/// [blanket]: https://doc.rust-lang.org/book/ch10-02-traits.html#using-trait-bounds-to-conditionally-implement-methods
+#[macro_export]
+macro_rules! assert_not_impl_any {
+    ($x:ty: $($t:path),+ $(,)?) => {
+        const _: fn() = || {
+            // Generic trait with a blanket impl over `()` for all types.
+            trait AmbiguousIfImpl<A> {
+                // Required for actually being able to reference the trait.
+                fn some_item() {}
+            }
+
+            impl<T: ?Sized> AmbiguousIfImpl<()> for T {}
+
+            // Creates multiple scoped `Invalid` types for each trait `$t`, over
+            // which a specialized `AmbiguousIfImpl<Invalid>` is implemented for
+            // every type that implements `$t`.
+            $({
+                #[allow(dead_code)]
+                struct Invalid;
+
+                impl<T: ?Sized + $t> AmbiguousIfImpl<Invalid> for T {}
+            })+
+
+            // If there is only one specialized trait impl, type inference with
+            // `_` can be resolved and this can compile. Fails to compile if
+            // `$x` implements any `AmbiguousIfImpl<Invalid>`.
+            let _ = <$x as AmbiguousIfImpl<_>>::some_item;
+        };
+    };
+}
diff --git a/third_party/rust/static_assertions/src/assert_obj_safe.rs b/third_party/rust/static_assertions/src/assert_obj_safe.rs
new file mode 100644
index 0000000000..ecbba96475
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_obj_safe.rs
@@ -0,0 +1,76 @@
+// FIXME: Link below is required to render in index
+/// Asserts that the traits support dynamic dispatch
+/// ([object-safety](https://doc.rust-lang.org/book/ch17-02-trait-objects.html#object-safety-is-required-for-trait-objects)).
+///
+/// This is useful for when changes are made to a trait that accidentally
+/// prevent it from being used as an [object]. Such a case would be adding a
+/// generic method and forgetting to add `where Self: Sized` after it. If left
+/// unnoticed, that mistake will affect crate users and break both forward and
+/// backward compatibility.
+///
+/// # Examples
+///
+/// When exposing a public API, it's important that traits that could previously
+/// use dynamic dispatch can still do so in future compatible crate versions.
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// trait MySafeTrait {
+///     fn foo(&self) -> u32;
+/// }
+///
+/// assert_obj_safe!(std::fmt::Write, MySafeTrait);
+/// ```
+///
+/// Works with traits that are not in the calling module:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// mod inner {
+///     pub trait BasicTrait {
+///         fn bar(&self);
+///     }
+///     assert_obj_safe!(BasicTrait);
+/// }
+///
+/// assert_obj_safe!(inner::BasicTrait);
+/// ```
+///
+/// The following example fails to compile because raw pointers cannot be sent
+///  between threads safely:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_impl!(*const u8, Send);
+/// ```
+///
+/// The following example fails to compile because generics without
+/// `where Self: Sized` are not allowed in [object-safe][object] trait methods:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// trait MyUnsafeTrait {
+///     fn baz<T>(&self) -> T;
+/// }
+///
+/// assert_obj_safe!(MyUnsafeTrait);
+/// ```
+///
+/// When we fix that, the previous code will compile:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// trait MyUnsafeTrait {
+///     fn baz<T>(&self) -> T where Self: Sized;
+/// }
+///
+/// assert_obj_safe!(MyUnsafeTrait);
+/// ```
+///
+/// [object]: https://doc.rust-lang.org/book/ch17-02-trait-objects.html#object-safety-is-required-for-trait-objects
+#[macro_export]
+macro_rules! assert_obj_safe {
+    ($($xs:path),+ $(,)?) => {
+        $(const _: Option<&$xs> = None;)+
+    };
+}
diff --git a/third_party/rust/static_assertions/src/assert_trait.rs b/third_party/rust/static_assertions/src/assert_trait.rs
new file mode 100644
index 0000000000..c231492fda
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_trait.rs
@@ -0,0 +1,105 @@
+/// Asserts that the trait is a child of all of the other traits.
+///
+/// Related:
+/// - [`assert_trait_super_all!`]
+///
+/// # Examples
+///
+/// All types that implement [`Copy`] must implement [`Clone`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_trait_sub_all!(Copy: Clone);
+/// ```
+///
+/// All types that implement [`Ord`] must implement [`PartialEq`], [`Eq`], and
+/// [`PartialOrd`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_trait_sub_all!(Ord: PartialEq, Eq, PartialOrd);
+/// ```
+///
+/// The following example fails to compile because [`Eq`] is not required for
+/// [`PartialOrd`]:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_trait_sub_all!(PartialOrd: Eq);
+/// ```
+///
+/// [`assert_trait_super_all!`]: macro.assert_trait_super_all.html
+///
+/// [`Copy`]:       https://doc.rust-lang.org/std/marker/trait.Copy.html
+/// [`Clone`]:      https://doc.rust-lang.org/std/clone/trait.Clone.html
+/// [`Ord`]:        https://doc.rust-lang.org/std/cmp/trait.Ord.html
+/// [`PartialOrd`]: https://doc.rust-lang.org/std/cmp/trait.PartialOrd.html
+/// [`Eq`]:         https://doc.rust-lang.org/std/cmp/trait.Eq.html
+/// [`PartialEq`]:  https://doc.rust-lang.org/std/cmp/trait.PartialEq.html
+#[macro_export]
+macro_rules! assert_trait_sub_all {
+    ($sub:path: $($super:path),+ $(,)?) => {
+        const _: () = {
+            // One scope per super-trait.
+            $({
+                #[allow(non_camel_case_types)]
+                trait __Impl_Implication: $super {}
+
+                // Can only be implemented for `$sub` types if `$super` is
+                // also implemented.
+                impl<T: $sub> __Impl_Implication for T {}
+            })+
+        };
+    };
+}
+
+/// Asserts that the trait is a parent of all of the other traits.
+///
+/// Related:
+/// - [`assert_trait_sub_all!`]
+///
+/// # Examples
+///
+/// With this, traits `A` and `B` can both be tested to require [`Copy`] on a
+/// single line:
+///
+/// ```
+/// # use static_assertions::assert_trait_super_all;
+/// trait A: Copy {}
+/// trait B: Copy {}
+///
+/// assert_trait_super_all!(Copy: A, B);
+/// ```
+///
+/// Otherwise, each sub-trait would require its own call to
+/// [`assert_trait_sub_all!`]:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// # trait A: Copy {}
+/// # trait B: Copy {}
+/// assert_trait_sub_all!(A: Copy);
+/// assert_trait_sub_all!(B: Copy);
+/// ```
+///
+/// The following example fails to compile because trait `C` does not require
+/// [`Copy`]:
+///
+/// ```compile_fail
+/// # use static_assertions::assert_trait_super_all;
+/// # trait A: Copy {}
+/// # trait B: Copy {}
+/// trait C {}
+///
+/// assert_trait_super_all!(Copy: A, B, C);
+/// ```
+///
+/// [`assert_trait_sub_all!`]: macro.assert_trait_sub_all.html
+///
+/// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
+#[macro_export(local_inner_macros)]
+macro_rules! assert_trait_super_all {
+    ($super:path: $($sub:path),+ $(,)?) => {
+        $(assert_trait_sub_all!($sub: $super);)+
+    };
+}
diff --git a/third_party/rust/static_assertions/src/assert_type.rs b/third_party/rust/static_assertions/src/assert_type.rs
new file mode 100644
index 0000000000..dd2dc2a6f7
--- /dev/null
+++ b/third_party/rust/static_assertions/src/assert_type.rs
@@ -0,0 +1,101 @@
+/// Asserts that _all_ types in a list are equal to each other.
+///
+/// # Examples
+///
+/// Often times, type aliases are used to express usage semantics via naming. In
+/// some cases, the underlying type may differ based on platform. However, other
+/// types like [`c_float`] will always alias the same type.
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// use std::os::raw::c_float;
+///
+/// assert_type_eq_all!(c_float, f32);
+/// ```
+///
+/// This macro can also be used to compare types that involve lifetimes! Just
+/// use `'static` in that case:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions;
+/// # fn main() {
+/// type Buf<'a> = &'a [u8];
+///
+/// assert_type_eq_all!(Buf<'static>, &'static [u8]);
+/// # }
+/// ```
+///
+/// The following example fails to compile because `String` and `str` do not
+/// refer to the same type:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_type_eq_all!(String, str);
+/// ```
+///
+/// This should also work the other way around, regardless of [`Deref`]
+/// implementations.
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_type_eq_all!(str, String);
+/// ```
+///
+/// [`c_float`]: https://doc.rust-lang.org/std/os/raw/type.c_float.html
+/// [`Deref`]: https://doc.rust-lang.org/std/ops/trait.Deref.html
+#[macro_export]
+macro_rules! assert_type_eq_all {
+    ($x:ty, $($xs:ty),+ $(,)*) => {
+        const _: fn() = || { $({
+            trait TypeEq {
+                type This: ?Sized;
+            }
+
+            impl<T: ?Sized> TypeEq for T {
+                type This = Self;
+            }
+
+            fn assert_type_eq_all<T, U>()
+            where
+                T: ?Sized + TypeEq<This = U>,
+                U: ?Sized,
+            {}
+
+            assert_type_eq_all::<$x, $xs>();
+        })+ };
+    };
+}
+
+/// Asserts that _all_ types are **not** equal to each other.
+///
+/// # Examples
+///
+/// Rust has all sorts of slices, but they represent different types of data:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// assert_type_ne_all!([u8], [u16], str);
+/// ```
+///
+/// The following example fails to compile because [`c_uchar`] is a type alias
+/// for [`u8`]:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// use std::os::raw::c_uchar;
+///
+/// assert_type_ne_all!(c_uchar, u8, u32);
+/// ```
+///
+/// [`c_uchar`]: https://doc.rust-lang.org/std/os/raw/type.c_uchar.html
+/// [`u8`]: https://doc.rust-lang.org/std/primitive.u8.html
+#[macro_export]
+macro_rules! assert_type_ne_all {
+    ($x:ty, $($y:ty),+ $(,)?) => {
+        const _: fn() = || {
+            trait MutuallyExclusive {}
+            impl MutuallyExclusive for $x {}
+            $(impl MutuallyExclusive for $y {})+
+        };
+    };
+}
diff --git a/third_party/rust/static_assertions/src/const_assert.rs b/third_party/rust/static_assertions/src/const_assert.rs
new file mode 100644
index 0000000000..16ae4a6b42
--- /dev/null
+++ b/third_party/rust/static_assertions/src/const_assert.rs
@@ -0,0 +1,109 @@
+/// Asserts that constant expressions evaluate to `true`.
+///
+/// Constant expressions can be ensured to have certain properties via this
+/// macro If the expression evaluates to `false`, the file will fail to compile.
+/// This is synonymous to [`static_assert` in C++][static_assert].
+///
+/// # Alternatives
+///
+/// There also exists [`const_assert_eq`](macro.const_assert_eq.html) for
+/// validating whether a sequence of expressions are equal to one another.
+///
+/// # Examples
+///
+/// A common use case is to guarantee properties about a constant value that's
+/// generated via meta-programming.
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// const VALUE: i32 = // ...
+/// # 3;
+///
+/// const_assert!(VALUE >= 2);
+/// ```
+///
+/// Inputs are type-checked as booleans:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// const_assert!(!0);
+/// ```
+///
+/// Despite this being a macro, we see this produces a type error:
+///
+/// ```txt
+///   | const_assert!(!0);
+///   |               ^^ expected bool, found integral variable
+///   |
+///   = note: expected type `bool`
+///              found type `{integer}`
+/// ```
+///
+/// The following fails to compile because multiplying by 5 does not have an
+/// identity property:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// const_assert!(5 * 5 == 5);
+/// ```
+///
+/// [static_assert]: http://en.cppreference.com/w/cpp/language/static_assert
+#[macro_export]
+macro_rules! const_assert {
+    ($x:expr $(,)?) => {
+        #[allow(unknown_lints, eq_op)]
+        const _: [(); 0 - !{ const ASSERT: bool = $x; ASSERT } as usize] = [];
+    };
+}
+
+/// Asserts that constants are equal in value.
+///
+/// # Examples
+///
+/// This works as a shorthand for `const_assert!(a == b)`:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// const TWO: usize = 2;
+///
+/// const_assert_eq!(TWO * TWO, TWO + TWO);
+/// ```
+///
+/// Just because 2 × 2 = 2 + 2 doesn't mean it holds true for other numbers:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// const_assert_eq!(4 + 4, 4 * 4);
+/// ```
+#[macro_export(local_inner_macros)]
+macro_rules! const_assert_eq {
+    ($x:expr, $y:expr $(,)?) => {
+        const_assert!($x == $y);
+    };
+}
+
+/// Asserts that constants are **not** equal in value.
+///
+/// # Examples
+///
+/// This works as a shorthand for `const_assert!(a != b)`:
+///
+/// ```
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// const NUM: usize = 32;
+///
+/// const_assert_ne!(NUM * NUM, 64);
+/// ```
+///
+/// The following example fails to compile because 2 is magic and 2 × 2 = 2 + 2:
+///
+/// ```compile_fail
+/// # #[macro_use] extern crate static_assertions; fn main() {}
+/// const_assert_ne!(2 + 2, 2 * 2);
+/// ```
+#[macro_export(local_inner_macros)]
+macro_rules! const_assert_ne {
+    ($x:expr, $y:expr $(,)?) => {
+        const_assert!($x != $y);
+    };
+}
diff --git a/third_party/rust/static_assertions/src/lib.rs b/third_party/rust/static_assertions/src/lib.rs
new file mode 100644
index 0000000000..a43cc1f56d
--- /dev/null
+++ b/third_party/rust/static_assertions/src/lib.rs
@@ -0,0 +1,97 @@
+//! [![Banner](https://raw.githubusercontent.com/nvzqz/static-assertions-rs/assets/Banner.png)](https://github.com/nvzqz/static-assertions-rs)
+//!
+//! <div align="center">
+//!     <a href="https://crates.io/crates/static_assertions">
+//!         <img src="https://img.shields.io/crates/d/static_assertions.svg" alt="Downloads">
+//!     </a>
+//!     <a href="https://travis-ci.org/nvzqz/static-assertions-rs">
+//!         <img src="https://travis-ci.org/nvzqz/static-assertions-rs.svg?branch=master" alt="Build Status">
+//!     </a>
+//!     <img src="https://img.shields.io/badge/rustc-^1.37.0-blue.svg" alt="rustc ^1.37.0">
+//!     <br><br>
+//! </div>
+//!
+//! Assertions to ensure correct assumptions about constants, types, and more.
+//!
+//! _All_ checks provided by this crate are performed at [compile-time]. This
+//! allows for finding errors quickly and early when it comes to ensuring
+//! certain features or aspects of a codebase. These macros are especially
+//! important when exposing a public API that requires types to be the same size
+//! or implement certain traits.
+//!
+//! # Usage
+//!
+//! This crate is available [on crates.io][crate] and can be used by adding the
+//! following to your project's [`Cargo.toml`]:
+//!
+//! ```toml
+//! [dependencies]
+//! static_assertions = "1.1.0"
+//! ```
+//!
+//! and this to your crate root (`main.rs` or `lib.rs`):
+//!
+//! ```
+//! #[macro_use]
+//! extern crate static_assertions;
+//! # fn main() {}
+//! ```
+//!
+//! When using [Rust 2018 edition][2018], the following shorthand can help if
+//! having `#[macro_use]` is undesirable.
+//!
+//! ```edition2018
+//! extern crate static_assertions as sa;
+//!
+//! sa::const_assert!(true);
+//! ```
+//!
+//! # Examples
+//!
+//! Very thorough examples are provided in the docs for
+//! [each individual macro](#macros). Failure case examples are also documented.
+//!
+//! # Changes
+//!
+//! See [`CHANGELOG.md`](https://github.com/nvzqz/static-assertions-rs/blob/master/CHANGELOG.md)
+//! for an exhaustive list of what has changed from one version to another.
+//!
+//! # Donate
+//!
+//! This project is made freely available (as in free beer), but unfortunately
+//! not all beer is free! So, if you would like to buy me a beer (or coffee or
+//! *more*), then consider supporting my work that's benefited your project
+//! and thousands of others.
+//!
+//! <a href="https://www.patreon.com/nvzqz">
+//!     <img src="https://c5.patreon.com/external/logo/become_a_patron_button.png" alt="Become a Patron!" height="35">
+//! </a>
+//! <a href="https://www.paypal.me/nvzqz">
+//!     <img src="https://buymecoffee.intm.org/img/button-paypal-white.png" alt="Buy me a coffee" height="35">
+//! </a>
+//!
+//! [Rust 1.37]: https://blog.rust-lang.org/2019/08/15/Rust-1.37.0.html
+//! [2018]: https://blog.rust-lang.org/2018/12/06/Rust-1.31-and-rust-2018.html#rust-2018
+//! [crate]: https://crates.io/crates/static_assertions
+//! [compile-time]: https://en.wikipedia.org/wiki/Compile_time
+//! [`Cargo.toml`]: https://doc.rust-lang.org/cargo/reference/manifest.html
+
+#![doc(html_root_url = "https://docs.rs/static_assertions/1.1.0")]
+#![doc(html_logo_url = "https://raw.githubusercontent.com/nvzqz/static-assertions-rs/assets/Icon.png")]
+
+#![no_std]
+
+#![deny(unused_macros)]
+
+#[doc(hidden)]
+pub extern crate core as _core;
+
+mod assert_cfg;
+mod assert_eq_align;
+mod assert_eq_size;
+mod assert_fields;
+mod assert_impl;
+mod assert_obj_safe;
+mod assert_trait;
+mod assert_type;
+mod const_assert;