await in a switch inside a labeled for-of hangs at runtime #9198

An await inside a switch nested in a labeled for…of loop compiles, then hangs forever at runtime.

async function f(xs: number[]) {
  const out: string[] = [];
  outer: for (const x of xs) {
    switch (x % 4) {
      case 0: out.push("z" + x); break;
      case 1: await Promise.resolve(); out.push("a" + x); break;
      case 2: if (x > 5) break outer; out.push("b" + x); break;
      default: await Promise.resolve(); if (x > 10) continue outer; out.push("d" + x);
    }
    out.push("|");
  }
  return out.join("");
}
(async () => { console.log(await f([0,1,2,3,4,5,6,7,11,12])); })();

The loop label is doing the work here: the same body without outer: and without break outer/continue outer terminates. Both abrupt completions target the enclosing labeled loop from inside a switch that also contains an await, so the case bodies are split across generator states.

Confirmed pre-existing on main, by rebuilding the compiler with crates/perry-transform/src/generator/linearize.rs reverted to main and re-running: identical hang, exit 124 both ways. Found while auditing #9189, which is adjacent (it routes labeled breaks through yielding switches, #9186) but does not address this — its own case is a labeled switch, not a labeled for…of containing one.

Sibling: the async-generator form fails differently and is filed separately.