Add SAFETY comment to downcast_trait_mut

ivarflakstad · ivarflakstad · commit 2919430a2aec · 2025-07-24T11:48:37.000+02:00
diff --git a/library/core/src/any.rs b/library/core/src/any.rs
@@ -931,6 +931,8 @@ pub const fn downcast_trait_mut<
     match vtable {
         Some(dyn_metadata) => {
             let pointer = ptr::from_raw_parts_mut(t, dyn_metadata);
+            // SAFETY: `t` is a reference to a type, so we know it is valid.
+            // `dyn_metadata` is a vtable for T, implementing the trait of `U`.
             Some(unsafe { &mut *pointer })
         }
         None => None,

Original file line number	Diff line number	Diff line change
`@@ -931,6 +931,8 @@ pub const fn downcast_trait_mut<`
`931`	`931`	`match vtable {`
`932`	`932`	`Some(dyn_metadata) => {`
`933`	`933`	`let pointer = ptr::from_raw_parts_mut(t, dyn_metadata);`
	`934`	+ // SAFETY: `t` is a reference to a type, so we know it is valid.
	`935`	+ // `dyn_metadata` is a vtable for T, implementing the trait of `U`.
`934`	`936`	`Some(unsafe { &mut *pointer })`
`935`	`937`	`}`
`936`	`938`	`None => None,`