Rollup merge of #99576 - compiler-errors:foreign-fundamental-drop-is-bad, r=TaKO8Ki

Do not allow `Drop` impl on foreign fundamental types

`Drop` should not be implemented on `Pin<T>` even if `T` is local.

This does not trigger regular orphan rules is because `Pin` is `#[fundamental]`... but we don't allow specialized `Drop` impls anyways, so these rules are not sufficient to prevent this impl on stable. Let's just choose even stricter rules, since we shouldn't be implementing `Drop` on a foreign ADT ever.

Fixes #99575

compiler/rustc_error_messages/locales/en-US/typeck.ftl

@@ -24,8 +24,8 @@ typeck_lifetimes_or_bounds_mismatch_on_trait =
     .generics_label = lifetimes in impl do not match this {$item_kind} in trait
 
 typeck_drop_impl_on_wrong_item =
-    the `Drop` trait may only be implemented for structs, enums, and unions
-    .label = must be a struct, enum, or union
+    the `Drop` trait may only be implemented for local structs, enums, and unions
+    .label = must be a struct, enum, or union in the current crate
 
 typeck_field_already_declared =
     field `{$field_name}` is already declared

compiler/rustc_typeck/src/coherence/builtin.rs

@@ -47,9 +47,11 @@ impl<'tcx> Checker<'tcx> {
 }
 
 fn visit_implementation_of_drop(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
-    // Destructors only work on nominal types.
-    if let ty::Adt(..) | ty::Error(_) = tcx.type_of(impl_did).kind() {
-        return;
+    // Destructors only work on local ADT types.
+    match tcx.type_of(impl_did).kind() {
+        ty::Adt(def, _) if def.did().is_local() => return,
+        ty::Error(_) => return,
+        _ => {}
     }
 
     let sp = match tcx.hir().expect_item(impl_did).kind {