Safety comment

ivarflakstad · oli-obk · web-flow · commit 852c332c3679 · 2025-07-23T17:59:57.000+02:00
Co-authored-by: Oli Scherer &lt;github35764891676564198441@oli-obk.de&gt;
diff --git a/library/core/src/any.rs b/library/core/src/any.rs
@@ -910,6 +910,8 @@ pub const fn downcast_trait<
     match vtable {
         Some(dyn_metadata) => {
             let pointer = ptr::from_raw_parts(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 { &*pointer })
         }
         None => None,

Original file line number	Diff line number	Diff line change
`@@ -910,6 +910,8 @@ pub const fn downcast_trait<`
`910`	`910`	`match vtable {`
`911`	`911`	`Some(dyn_metadata) => {`
`912`	`912`	`let pointer = ptr::from_raw_parts(t, dyn_metadata);`
	`913`	+ // SAFETY: `t` is a reference to a type, so we know it is valid.
	`914`	+ // `dyn_metadata` is a vtable for T, implementing the trait of `U`.
`913`	`915`	`Some(unsafe { &*pointer })`
`914`	`916`	`}`
`915`	`917`	`None => None,`