Point at the right enclosing scope when using await in non-async fn

src/librustc/hir/lowering/expr.rs

@@ -677,6 +677,7 @@ impl LoweringContext<'_> {
         let fn_decl = self.lower_fn_decl(decl, None, false, None);
 
         self.with_new_scopes(|this| {
+            let prev = this.current_item;
             this.current_item = Some(fn_decl_span);
             let mut generator_kind = None;
             let body_id = this.lower_fn_body(decl, |this| {
@@ -690,8 +691,10 @@ impl LoweringContext<'_> {
                 generator_kind,
                 movability,
             );
+            let capture_clause = this.lower_capture_clause(capture_clause);
+            this.current_item = prev;
             hir::ExprKind::Closure(
-                this.lower_capture_clause(capture_clause),
+                capture_clause,
                 fn_decl,
                 body_id,
                 fn_decl_span,

src/test/ui/issues/issue-63398.rs

@@ -0,0 +1,11 @@
+// edition:2018
+#![feature(async_await)]
+
+async fn do_the_thing() -> u8 {
+    8
+}
+
+fn main() {
+    let x = move || {};
+    let y = do_the_thing().await; //~ ERROR `await` is only allowed inside `async` functions
+}

src/test/ui/issues/issue-63398.stderr

@@ -0,0 +1,11 @@
+error[E0728]: `await` is only allowed inside `async` functions and blocks
+  --> $DIR/issue-63398.rs:10:13
+   |
+LL | fn main() {
+   |    ---- this is not `async`
+LL |     let x = move || {};
+LL |     let y = do_the_thing().await;
+   |             ^^^^^^^^^^^^^^^^^^^^ only allowed inside `async` functions and blocks
+
+error: aborting due to previous error
+