AsyncDestructor: replace fields with impl_did

compiler/rustc_middle/src/ty/mod.rs

@@ -1124,10 +1124,8 @@ pub struct Destructor {
 // FIXME: consider combining this definition with regular `Destructor`
 #[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
 pub struct AsyncDestructor {
-    /// The `DefId` of the async destructor future constructor
-    pub ctor: DefId,
-    /// The `DefId` of the async destructor future type
-    pub future: DefId,
+    /// The `DefId` of the `impl AsyncDrop`
+    pub impl_did: LocalDefId,
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]

compiler/rustc_middle/src/ty/significant_drop_order.rs

@@ -154,7 +154,7 @@ pub fn ty_dtor_span<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<Span> {
             let dtor = if let Some(dtor) = tcx.adt_destructor(did) {
                 dtor.did
             } else if let Some(dtor) = tcx.adt_async_destructor(did) {
-                dtor.future
+                return Some(tcx.source_span(dtor.impl_did));
             } else {
                 return Some(try_local_did_span(did));
             };

compiler/rustc_middle/src/ty/util.rs

@@ -450,26 +450,17 @@ impl<'tcx> TyCtxt<'tcx> {
                 continue;
             }
 
-            let [future, ctor] = self.associated_item_def_ids(impl_did) else {
-                self.dcx().span_delayed_bug(
-                    self.def_span(impl_did),
-                    "AsyncDrop impl without async_drop function or Dropper type",
-                );
-                continue;
-            };
-
-            if let Some((_, _, old_impl_did)) = dtor_candidate {
+            if let Some(old_impl_did) = dtor_candidate {
                 self.dcx()
                     .struct_span_err(self.def_span(impl_did), "multiple async drop impls found")
                     .with_span_note(self.def_span(old_impl_did), "other impl here")
                     .delay_as_bug();
             }
 
-            dtor_candidate = Some((*future, *ctor, impl_did));
+            dtor_candidate = Some(impl_did);
         }
 
-        let (future, ctor, _) = dtor_candidate?;
-        Some(ty::AsyncDestructor { future, ctor })
+        Some(ty::AsyncDestructor { impl_did: dtor_candidate? })
     }
 
     /// Returns async drop glue morphology for a definition. To get async drop