Tweak expr.await desugaring Span

Fix #93074

Author: estebank

compiler/rustc_ast_lowering/src/expr.rs

@@ -630,18 +630,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ///     }
     /// }
     /// ```
-    fn lower_expr_await(&mut self, await_span: Span, expr: &Expr) -> hir::ExprKind<'hir> {
-        let dot_await_span = expr.span.shrink_to_hi().to(await_span);
+    fn lower_expr_await(&mut self, dot_await_span: Span, expr: &Expr) -> hir::ExprKind<'hir> {
+        let full_span = expr.span.to(dot_await_span);
         match self.generator_kind {
             Some(hir::GeneratorKind::Async(_)) => {}
             Some(hir::GeneratorKind::Gen) | None => {
                 let mut err = struct_span_err!(
                     self.sess,
-                    await_span,
+                    dot_await_span,
                     E0728,
                     "`await` is only allowed inside `async` functions and blocks"
                 );
-                err.span_label(await_span, "only allowed inside `async` functions and blocks");
+                err.span_label(dot_await_span, "only allowed inside `async` functions and blocks");
                 if let Some(item_sp) = self.current_item {
                     err.span_label(item_sp, "this is not `async`");
                 }
@@ -651,7 +651,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let span = self.mark_span_with_reason(DesugaringKind::Await, dot_await_span, None);
         let gen_future_span = self.mark_span_with_reason(
             DesugaringKind::Await,
-            await_span,
+            full_span,
             self.allow_gen_future.clone(),
         );
         let expr = self.lower_expr_mut(expr);
@@ -704,9 +704,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let loop_hir_id = self.lower_node_id(loop_node_id);
         let ready_arm = {
             let x_ident = Ident::with_dummy_span(sym::result);
-            let (x_pat, x_pat_hid) = self.pat_ident(span, x_ident);
-            let x_expr = self.expr_ident(span, x_ident, x_pat_hid);
-            let ready_field = self.single_pat_field(span, x_pat);
+            let (x_pat, x_pat_hid) = self.pat_ident(gen_future_span, x_ident);
+            let x_expr = self.expr_ident(gen_future_span, x_ident, x_pat_hid);
+            let ready_field = self.single_pat_field(gen_future_span, x_pat);
             let ready_pat = self.pat_lang_item_variant(
                 span,
                 hir::LangItem::PollReady,
@@ -716,7 +716,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let break_x = self.with_loop_scope(loop_node_id, move |this| {
                 let expr_break =
                     hir::ExprKind::Break(this.lower_loop_destination(None), Some(x_expr));
-                this.arena.alloc(this.expr(span, expr_break, ThinVec::new()))
+                this.arena.alloc(this.expr(gen_future_span, expr_break, ThinVec::new()))
             });
             self.arm(ready_pat, break_x)
         };
@@ -788,7 +788,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // `match ::std::future::IntoFuture::into_future(<expr>) { ... }`
         let into_future_span = self.mark_span_with_reason(
             DesugaringKind::Await,
-            await_span,
+            dot_await_span,
             self.allow_into_future.clone(),
         );
         let into_future_expr = self.expr_call_lang_item_fn(

src/test/ui/async-await/proper-span-for-type-error.fixed

@@ -0,0 +1,11 @@
+// edition:2021
+// run-rustfix
+#![allow(dead_code)]
+
+async fn a() {}
+
+async fn foo() -> Result<(), i32> {
+    Ok(a().await) //~ ERROR mismatched types
+}
+
+fn main() {}

src/test/ui/async-await/proper-span-for-type-error.rs

@@ -0,0 +1,11 @@
+// edition:2021
+// run-rustfix
+#![allow(dead_code)]
+
+async fn a() {}
+
+async fn foo() -> Result<(), i32> {
+    a().await //~ ERROR mismatched types
+}
+
+fn main() {}

src/test/ui/async-await/proper-span-for-type-error.stderr

@@ -0,0 +1,16 @@
+error[E0308]: mismatched types
+  --> $DIR/proper-span-for-type-error.rs:8:5
+   |
+LL |     a().await
+   |     ^^^^^^^^^ expected enum `Result`, found `()`
+   |
+   = note:   expected enum `Result<(), i32>`
+           found unit type `()`
+help: try wrapping the expression in `Ok`
+   |
+LL |     Ok(a().await)
+   |     +++         +
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.