Rollup merge of #112868 - compiler-errors:liberate-afit-sugg, r=WaffleLapkin

Liberate bound vars properly when suggesting missing async-fn-in-trait

Fixes #112848

Author: GuillaumeGomez

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -470,19 +470,16 @@ fn suggestion_signature<'tcx>(
     );
 
     match assoc.kind {
-        ty::AssocKind::Fn => {
-            // We skip the binder here because the binder would deanonymize all
-            // late-bound regions, and we don't want method signatures to show up
-            // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
-            // regions just fine, showing `fn(&MyType)`.
-            fn_sig_suggestion(
-                tcx,
-                tcx.fn_sig(assoc.def_id).subst(tcx, substs).skip_binder(),
-                assoc.ident(tcx),
-                tcx.predicates_of(assoc.def_id).instantiate_own(tcx, substs),
-                assoc,
-            )
-        }
+        ty::AssocKind::Fn => fn_sig_suggestion(
+            tcx,
+            tcx.liberate_late_bound_regions(
+                assoc.def_id,
+                tcx.fn_sig(assoc.def_id).subst(tcx, substs),
+            ),
+            assoc.ident(tcx),
+            tcx.predicates_of(assoc.def_id).instantiate_own(tcx, substs),
+            assoc,
+        ),
         ty::AssocKind::Type => {
             let (generics, where_clauses) = bounds_from_generic_predicates(
                 tcx,

tests/ui/impl-trait/in-trait/suggest-missing-item.fixed

@@ -9,11 +9,14 @@ trait Trait {
     async fn bar() -> i32;
 
     fn test(&self) -> impl Sized + '_;
+
+    async fn baz(&self) -> &i32;
 }
 
 struct S;
 
-impl Trait for S {fn test(&self) -> impl Sized + '_ { todo!() }
+impl Trait for S {async fn baz(&self) -> &i32 { todo!() }
+fn test(&self) -> impl Sized + '_ { todo!() }
 async fn bar() -> i32 { todo!() }
 async fn foo() { todo!() }
 }

tests/ui/impl-trait/in-trait/suggest-missing-item.rs

@@ -9,6 +9,8 @@ trait Trait {
     async fn bar() -> i32;
 
     fn test(&self) -> impl Sized + '_;
+
+    async fn baz(&self) -> &i32;
 }
 
 struct S;

tests/ui/impl-trait/in-trait/suggest-missing-item.stderr

@@ -1,5 +1,5 @@
-error[E0046]: not all trait items implemented, missing: `foo`, `bar`, `test`
-  --> $DIR/suggest-missing-item.rs:16:1
+error[E0046]: not all trait items implemented, missing: `foo`, `bar`, `test`, `baz`
+  --> $DIR/suggest-missing-item.rs:18:1
    |
 LL |     async fn foo();
    |     --------------- `foo` from trait
@@ -9,9 +9,12 @@ LL |     async fn bar() -> i32;
 LL |
 LL |     fn test(&self) -> impl Sized + '_;
    |     ---------------------------------- `test` from trait
+LL |
+LL |     async fn baz(&self) -> &i32;
+   |     ---------------------------- `baz` from trait
 ...
 LL | impl Trait for S {}
-   | ^^^^^^^^^^^^^^^^ missing `foo`, `bar`, `test` in implementation
+   | ^^^^^^^^^^^^^^^^ missing `foo`, `bar`, `test`, `baz` in implementation
 
 error: aborting due to previous error