Async drop - type instead of async drop fn, fixes #140484

Author: azhogin

compiler/rustc_mir_transform/src/elaborate_drop.rs

@@ -1,6 +1,7 @@
 use std::{fmt, iter, mem};
 
 use rustc_abi::{FIRST_VARIANT, FieldIdx, VariantIdx};
+use rustc_hir::def::DefKind;
 use rustc_hir::lang_items::LangItem;
 use rustc_index::Idx;
 use rustc_middle::mir::*;
@@ -254,8 +255,13 @@ where
             // 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()
+            let Some(drop_fn_def_id) = tcx
+                .associated_item_def_ids(drop_trait)
+                .first()
+                .and_then(|def_id| {
+                    if tcx.def_kind(def_id) == DefKind::AssocFn { Some(def_id) } else { None }
+                })
+                .copied()
             else {
                 tcx.dcx().span_delayed_bug(
                     self.elaborator.body().span,

tests/ui/async-await/async-drop/unexpected-sort.rs

@@ -0,0 +1,18 @@
+// Ex-ice: #140484
+//@ edition: 2024
+#![crate_type = "lib"]
+#![allow(incomplete_features)]
+#![allow(non_camel_case_types)]
+#![feature(async_drop)]
+use std::future::AsyncDrop;
+struct a;
+impl Drop for a { //~ ERROR: not all trait items implemented, missing: `drop`
+    fn b() {} //~ ERROR: method `b` is not a member of trait `Drop`
+}
+impl AsyncDrop for a { //~ ERROR: not all trait items implemented, missing: `drop`
+    type c; //~ ERROR: associated type in `impl` without body
+    //~^ ERROR: type `c` is not a member of trait `AsyncDrop`
+}
+async fn bar() {
+    a;
+}

tests/ui/async-await/async-drop/unexpected-sort.stderr

@@ -0,0 +1,40 @@
+error: associated type in `impl` without body
+  --> $DIR/unexpected-sort.rs:13:5
+   |
+LL |     type c;
+   |     ^^^^^^-
+   |           |
+   |           help: provide a definition for the type: `= <type>;`
+
+error[E0407]: method `b` is not a member of trait `Drop`
+  --> $DIR/unexpected-sort.rs:10:5
+   |
+LL |     fn b() {}
+   |     ^^^^^^^^^ not a member of trait `Drop`
+
+error[E0437]: type `c` is not a member of trait `AsyncDrop`
+  --> $DIR/unexpected-sort.rs:13:5
+   |
+LL |     type c;
+   |     ^^^^^^^ not a member of trait `AsyncDrop`
+
+error[E0046]: not all trait items implemented, missing: `drop`
+  --> $DIR/unexpected-sort.rs:9:1
+   |
+LL | impl Drop for a {
+   | ^^^^^^^^^^^^^^^ missing `drop` in implementation
+   |
+   = help: implement the missing item: `fn drop(&mut self) { todo!() }`
+
+error[E0046]: not all trait items implemented, missing: `drop`
+  --> $DIR/unexpected-sort.rs:12:1
+   |
+LL | impl AsyncDrop for a {
+   | ^^^^^^^^^^^^^^^^^^^^ missing `drop` in implementation
+   |
+   = help: implement the missing item: `async fn drop(self: Pin<&mut Self>) { todo!() }`
+
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0046, E0407, E0437.
+For more information about an error, try `rustc --explain E0046`.