1 files changed, 108 insertions, 0 deletions
diff --git a/third_party/rust/yoke/src/macro_impls.rs b/third_party/rust/yoke/src/macro_impls.rs
new file mode 100644
index 0000000000..060061b209
--- /dev/null
+++ b/third_party/rust/yoke/src/macro_impls.rs
@@ -0,0 +1,108 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+// In this case consistency between impls is more important
+// than using pointer casts
+#![allow(clippy::transmute_ptr_to_ptr)]
+
+use crate::Yokeable;
+use core::{mem, ptr};
+
+macro_rules! copy_yoke_impl {
+    () => {
+        #[inline]
+        fn transform(&self) -> &Self::Output {
+            self
+        }
+        #[inline]
+        fn transform_owned(self) -> Self::Output {
+            self
+        }
+        #[inline]
+        unsafe fn make(this: Self::Output) -> Self {
+            this
+        }
+        #[inline]
+        fn transform_mut<F>(&'a mut self, f: F)
+        where
+            F: 'static + for<'b> FnOnce(&'b mut Self::Output),
+        {
+            f(self)
+        }
+    };
+}
+macro_rules! impl_copy_type {
+    ($ty:ident) => {
+        unsafe impl<'a> Yokeable<'a> for $ty {
+            type Output = Self;
+            copy_yoke_impl!();
+        }
+    };
+}
+
+impl_copy_type!(u8);
+impl_copy_type!(u16);
+impl_copy_type!(u32);
+impl_copy_type!(u64);
+impl_copy_type!(u128);
+impl_copy_type!(usize);
+impl_copy_type!(i8);
+impl_copy_type!(i16);
+impl_copy_type!(i32);
+impl_copy_type!(i64);
+impl_copy_type!(i128);
+impl_copy_type!(isize);
+impl_copy_type!(char);
+impl_copy_type!(bool);
+
+// This is for when we're implementing Yoke on a complex type such that it's not
+// obvious to the compiler that the lifetime is covariant
+macro_rules! unsafe_complex_yoke_impl {
+    () => {
+        fn transform(&'a self) -> &'a Self::Output {
+            unsafe { mem::transmute(self) }
+        }
+
+        fn transform_owned(self) -> Self::Output {
+            debug_assert!(mem::size_of::<Self::Output>() == mem::size_of::<Self>());
+            unsafe {
+                let ptr: *const Self::Output = (&self as *const Self).cast();
+                mem::forget(self);
+                ptr::read(ptr)
+            }
+        }
+
+        unsafe fn make(from: Self::Output) -> Self {
+            debug_assert!(mem::size_of::<Self::Output>() == mem::size_of::<Self>());
+            let ptr: *const Self = (&from as *const Self::Output).cast();
+            mem::forget(from);
+            ptr::read(ptr)
+        }
+
+        fn transform_mut<F>(&'a mut self, f: F)
+        where
+            F: 'static + for<'b> FnOnce(&'b mut Self::Output),
+        {
+            // Cast away the lifetime of Self
+            unsafe { f(mem::transmute::<&'a mut Self, &'a mut Self::Output>(self)) }
+        }
+    };
+}
+
+unsafe impl<'a, T: 'static + for<'b> Yokeable<'b>> Yokeable<'a> for Option<T> {
+    type Output = Option<<T as Yokeable<'a>>::Output>;
+    unsafe_complex_yoke_impl!();
+}
+
+unsafe impl<'a, T1: 'static + for<'b> Yokeable<'b>, T2: 'static + for<'b> Yokeable<'b>> Yokeable<'a>
+    for (T1, T2)
+{
+    type Output = (<T1 as Yokeable<'a>>::Output, <T2 as Yokeable<'a>>::Output);
+    unsafe_complex_yoke_impl!();
+}
+
+unsafe impl<'a, T: Yokeable<'a>, const N: usize> Yokeable<'a> for [T; N] {
+    type Output = [<T as Yokeable<'a>>::Output; N];
+    unsafe_complex_yoke_impl!();
+}