From dc794f18a425a20563943ea4201b34ebea2aa017 Mon Sep 17 00:00:00 2001
From: Andrew Zhogin <andrew.zhogin@gmail.com>
Date: Wed, 21 May 2025 15:21:01 +0700
Subject: When AsyncDrop impl is empty, sync drop generated in elaborator
 (Fixes #140974)

---
 compiler/rustc_mir_transform/src/elaborate_drop.rs | 24 +++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

(limited to 'compiler/rustc_mir_transform/src')

diff --git a/compiler/rustc_mir_transform/src/elaborate_drop.rs b/compiler/rustc_mir_transform/src/elaborate_drop.rs
index 73a58160a6a..5d86b1353c0 100644
--- a/compiler/rustc_mir_transform/src/elaborate_drop.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_drop.rs
@@ -251,7 +251,29 @@ where
                     span_bug!(span, "invalid `AsyncDrop` impl_source: {:?}", impl_source);
                 }
             };
-            let drop_fn_def_id = tcx.associated_item_def_ids(drop_trait)[0];
+            // impl_item_refs may be empty if drop fn is not implemented in 'impl AsyncDrop for ...'
+            // (#140974).
+            // Such code will report error, so just generate sync drop here and return
+            let Some(drop_fn_def_id) =
+                tcx.associated_item_def_ids(drop_trait).into_iter().nth(0).copied()
+            else {
+                tcx.dcx().span_delayed_bug(
+                    self.elaborator.body().span,
+                    "AsyncDrop type without correct `async fn drop(...)`.",
+                );
+                self.elaborator.patch().patch_terminator(
+                    pin_obj_bb,
+                    TerminatorKind::Drop {
+                        place,
+                        target: succ,
+                        unwind: unwind.into_action(),
+                        replace: false,
+                        drop: None,
+                        async_fut: None,
+                    },
+                );
+                return pin_obj_bb;
+            };
             let drop_fn = Ty::new_fn_def(tcx, drop_fn_def_id, trait_args);
             let sig = drop_fn.fn_sig(tcx);
             let sig = tcx.instantiate_bound_regions_with_erased(sig);
-- 
cgit 1.4.1-3-g733a5


From 7c38b6fd28b1972659b662683866c359f198a6f7 Mon Sep 17 00:00:00 2001
From: Andrew Zhogin <andrew.zhogin@gmail.com>
Date: Tue, 20 May 2025 22:36:03 +0700
Subject: Async drop fix for 'broken mir in AsyncDropGlue, place has deref as a
 later projection' (#140975)

---
 compiler/rustc_mir_transform/src/elaborate_drop.rs | 21 ++++++++++-------
 tests/crashes/140975.rs                            | 22 ------------------
 .../async-drop/deref-later-projection.rs           | 26 ++++++++++++++++++++++
 3 files changed, 39 insertions(+), 30 deletions(-)
 delete mode 100644 tests/crashes/140975.rs
 create mode 100644 tests/ui/async-await/async-drop/deref-later-projection.rs

(limited to 'compiler/rustc_mir_transform/src')

diff --git a/compiler/rustc_mir_transform/src/elaborate_drop.rs b/compiler/rustc_mir_transform/src/elaborate_drop.rs
index 73a58160a6a..61312eb7d1a 100644
--- a/compiler/rustc_mir_transform/src/elaborate_drop.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_drop.rs
@@ -318,15 +318,20 @@ 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 addr = Rvalue::RawPtr(
-                RawPtrKind::Mut,
-                pin_obj_place.project_deeper(
-                    &[ProjectionElem::Field(FieldIdx::ZERO, unwrap_ty), ProjectionElem::Deref],
-                    tcx,
-                ),
-            );
+            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, tcx.mk_place_deref(obj_ref_place));
             call_statements.push(self.assign(obj_ptr_place, addr));
             obj_ptr_place
         };
diff --git a/tests/crashes/140975.rs b/tests/crashes/140975.rs
deleted file mode 100644
index e11dd40612c..00000000000
--- a/tests/crashes/140975.rs
+++ /dev/null
@@ -1,22 +0,0 @@
-//@ known-bug: #140975
-//@ compile-flags: --crate-type lib -Zvalidate-mir
-//@ edition: 2021
-#![feature(async_drop)]
-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
-   };
-}
diff --git a/tests/ui/async-await/async-drop/deref-later-projection.rs b/tests/ui/async-await/async-drop/deref-later-projection.rs
new file mode 100644
index 00000000000..baf81daf766
--- /dev/null
+++ b/tests/ui/async-await/async-drop/deref-later-projection.rs
@@ -0,0 +1,26 @@
+// Ex-ICE: #140975
+//@ compile-flags: -Zvalidate-mir
+//@ build-pass
+//@ edition:2021
+#![crate_type = "lib"]
+#![feature(async_drop)]
+#![allow(incomplete_features)]
+
+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
+   };
+}
-- 
cgit 1.4.1-3-g733a5