1 files changed, 45 insertions, 0 deletions
diff --git a/vendor/static_assertions/src/assert_eq_align.rs b/vendor/static_assertions/src/assert_eq_align.rs
new file mode 100644
index 000000000..69412daef
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+++ b/vendor/static_assertions/src/assert_eq_align.rs
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+/// 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>()];)+
+        };
+    };
+}