break label out of a switch in an async generator throws TypeError reading 'done'

[proggeramlug]

A break label targeting a labeled for…of from inside a switch, in an async generator, throws instead of breaking.

async function* gen(xs: number[]) {
  loop: for (const x of xs) {
    switch (x) { case 1: yield "y1"; break; case 2: break loop; default: yield "d" + x; }
  }
}
(async () => { const acc: string[] = []; for await (const v of gen([1,3,2,4])) acc.push(v); console.log(acc.join(",")); })();

	result
node 26.5.1	y1,d3
perry	Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'done')

The done read failing points at the async-iterator protocol: the labeled break appears to leave the generator state machine without producing a well-formed iterator result, so for await reads .done off undefined. The plain break in case 1 is fine — it is the labeled one that targets the enclosing for…of that fails.

Confirmed pre-existing on main by reverting crates/perry-transform/src/generator/linearize.rs to main and rebuilding: identical error, exit 1 both ways. Found while auditing #9189; that PR fixes the labeled-switch case (#9186) and this async-generator shape is not in its scope.

Sibling: the async function form with a labeled for…of hangs rather than throwing, filed separately.