Rollup merge of #120402 - compiler-errors:async-closure-def-tree, r=cjgillot

Make the coroutine def id of an async closure the child of the closure def id

Adjust def collection to make the (inner) coroutine returned by an async closure be a def id child of the (outer) closure. This makes it easy to map from coroutine -> closure by using `tcx.parent`, since currently it's not trivial to do this.

compiler/rustc_resolve/src/def_collector.rs

@@ -289,12 +289,18 @@ impl<'a, 'b, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'b, 'tcx> {
                 // we must create two defs.
                 let closure_def = self.create_def(expr.id, kw::Empty, DefKind::Closure, expr.span);
                 match closure.coroutine_kind {
-                    Some(coroutine_kind) => self.create_def(
-                        coroutine_kind.closure_id(),
-                        kw::Empty,
-                        DefKind::Closure,
-                        expr.span,
-                    ),
+                    Some(coroutine_kind) => {
+                        self.with_parent(closure_def, |this| {
+                            let coroutine_def = this.create_def(
+                                coroutine_kind.closure_id(),
+                                kw::Empty,
+                                DefKind::Closure,
+                                expr.span,
+                            );
+                            this.with_parent(coroutine_def, |this| visit::walk_expr(this, expr));
+                        });
+                        return;
+                    }
                     None => closure_def,
                 }
             }

tests/ui/async-await/async-closures/def-path.rs

@@ -0,0 +1,14 @@
+// compile-flags: -Zverbose-internals
+// edition:2021
+
+#![feature(async_closure)]
+
+fn main() {
+    let x = async || {};
+    //~^ NOTE the expected `async` closure body
+    let () = x();
+    //~^ ERROR mismatched types
+    //~| NOTE this expression has type `{static main::{closure#0}::{closure#0} upvar_tys=
+    //~| NOTE expected `async` closure body, found `()`
+    //~| NOTE expected `async` closure body `{static main::{closure#0}::{closure#0}
+}

tests/ui/async-await/async-closures/def-path.stderr

@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+  --> $DIR/def-path.rs:9:9
+   |
+LL |     let x = async || {};
+   |                      -- the expected `async` closure body
+LL |
+LL |     let () = x();
+   |         ^^   --- this expression has type `{static main::{closure#0}::{closure#0} upvar_tys=?7t witness=?8t}`
+   |         |
+   |         expected `async` closure body, found `()`
+   |
+   = note: expected `async` closure body `{static main::{closure#0}::{closure#0} upvar_tys=?7t witness=?8t}`
+                         found unit type `()`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.