Add SAFETY comment to the TrustedLen impl of vec::Drain

sdroege · sdroege · commit 2706ae1a926c · 2021-02-01T10:07:48.000+02:00
diff --git a/library/alloc/src/vec/drain.rs b/library/alloc/src/vec/drain.rs
@@ -149,6 +149,8 @@ impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {
 }
 
 #[unstable(feature = "trusted_len", issue = "37572")]
+// SAFETY: `Drain` simply forwards to the underlying slice iterator, which implements `TrustedLen`
+// so the required properties are all preserved.
 unsafe impl<T, A: Allocator> TrustedLen for Drain<'_, T, A> {}
 
 #[stable(feature = "fused", since = "1.26.0")]

Original file line number	Diff line number	Diff line change
`@@ -149,6 +149,8 @@ impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {`
`149`	`149`	`}`
`150`	`150`
`151`	`151`	`#[unstable(feature = "trusted_len", issue = "37572")]`
	`152`	+// SAFETY: `Drain` simply forwards to the underlying slice iterator, which implements `TrustedLen`
	`153`	`+// so the required properties are all preserved.`
`152`	`154`	`unsafe impl<T, A: Allocator> TrustedLen for Drain<'_, T, A> {}`
`153`	`155`
`154`	`156`	`#[stable(feature = "fused", since = "1.26.0")]`