Async drop fix for 'broken mir in AsyncDropGlue, place has deref as a later projection' (#140975)

Author: azhogin

compiler/rustc_mir_transform/src/elaborate_drop.rs

@@ -318,14 +318,18 @@ where
                 bug!();
             };
             let obj_ptr_ty = Ty::new_mut_ptr(tcx, drop_ty);
-            let obj_ptr_place = Place::from(self.new_temp(obj_ptr_ty));
             let unwrap_ty = adt_def.non_enum_variant().fields[FieldIdx::ZERO].ty(tcx, adt_args);
+            let obj_ref_place = Place::from(self.new_temp(unwrap_ty));
+            call_statements.push(self.assign(obj_ref_place,
+                Rvalue::Use(Operand::Copy(
+                    tcx.mk_place_field(pin_obj_place, FieldIdx::ZERO, unwrap_ty)
+                ))
+            ));
+
+            let obj_ptr_place = Place::from(self.new_temp(obj_ptr_ty));
+
             let addr = Rvalue::RawPtr(
-                RawPtrKind::Mut,
-                pin_obj_place.project_deeper(
-                    &[ProjectionElem::Field(FieldIdx::ZERO, unwrap_ty), ProjectionElem::Deref],
-                    tcx,
-                ),
+                RawPtrKind::Mut, tcx.mk_place_deref(obj_ref_place)
             );
             call_statements.push(self.assign(obj_ptr_place, addr));
             obj_ptr_place

tests/ui/async-await/async-drop/deref-later-projection.rs

@@ -0,0 +1,26 @@
+//@ compile-flags: -Zvalidate-mir
+//@ build-pass
+//@ edition:2021
+#![crate_type = "lib"]
+#![feature(async_drop)]
+#![allow(incomplete_features)]
+#![allow(non_camel_case_types)]
+
+use std::{future::AsyncDrop, pin::Pin};
+
+struct HasAsyncDrop ;
+impl Drop for HasAsyncDrop {
+    fn drop(&mut self) {}
+}
+impl AsyncDrop for HasAsyncDrop {
+    async fn drop(self: Pin<&mut Self>) {}
+}
+
+struct Holder {
+    inner: HasAsyncDrop,
+}
+async fn bar() {
+    Holder {
+        inner: HasAsyncDrop
+   };
+}