Rollup merge of rust-lang#122680 - lqd:nested-await-args, r=compiler-errors

Do not eat nested expressions' results in `MayContainYieldPoint` format args visitor

rust-lang#121563 unintentionally changed the `MayContainYieldPoint` format args visitor behavior, now missing yield points in nested expressions, as seen in rust-lang#122674.

The walk can find a yield point in an expression but it was ignored.

r? `@petrochenkov` as the reviewer of rust-lang#121563
cc `@Jarcho` as the author

Fixes rust-lang#122674.
We're in the 1.77 release week. rust-lang#121563 will land on 1.78 but beta is still 1.77.9: this PR will likely need to be backported soon after beta is cut.

Author: matthiaskrgr

compiler/rustc_ast_lowering/src/format.rs

@@ -604,8 +604,7 @@ fn may_contain_yield_point(e: &ast::Expr) -> bool {
             if let ast::ExprKind::Await(_, _) | ast::ExprKind::Yield(_) = e.kind {
                 ControlFlow::Break(())
             } else {
-                visit::walk_expr(self, e);
-                ControlFlow::Continue(())
+                visit::walk_expr(self, e)
             }
         }
 

tests/ui/fmt/nested-awaits-issue-122674.rs

@@ -0,0 +1,22 @@
+// Non-regression test for issue #122674: a change in the format args visitor missed nested awaits.
+
+//@ edition: 2021
+//@ check-pass
+
+pub fn f1() -> impl std::future::Future<Output = Result<(), String>> + Send {
+    async {
+        should_work().await?;
+        Ok(())
+    }
+}
+
+async fn should_work() -> Result<String, String> {
+    let x = 1;
+    Err(format!("test: {}: {}", x, inner().await?))
+}
+
+async fn inner() -> Result<String, String> {
+    Ok("test".to_string())
+}
+
+fn main() {}