runtime: await Promise.all([...]) never resumes when inputs settle via executor-captured resolvers — program silently exits 0 #6328

Summary

await Promise.all([...]) never resumes when the input promises are settled through executor-captured resolvers. The program does not hang — it silently exits 0 having printed nothing, which is worse: no crash, no diagnostic, just a missing result.

The .then() form of the same code works. Confirmed on clean origin/main (0960415ad).

Repro

async function main() {
  const resolvers: ((v: number) => void)[] = [];
  const ps = Array.from({ length: 100 }, () => new Promise<number>((res) => { resolvers.push(res); }));
  const all = Promise.all(ps);
  for (let i = 0; i < 100; i++) resolvers[i](i);
  const r = await all;               // never resumes
  console.log("awaited", r.length);
}
main();

Notes

• The resolvers are captured out of the new Promise executor and invoked synchronously, after Promise.all(ps) has already been constructed.
• Replacing await all with all.then(r => console.log("awaited", r.length)) works, so the combinator itself settles — it is the await resumption that is lost.
• A variant where the resolvers are invoked later from a setTimeout does work, so the synchronous-settle-after-construction ordering appears to be load-bearing.

Surfaced while working on #6084 (PR #6327, promise side-table O(N^2)); that PR does not touch this and the bug reproduces identically without it. Filed separately so the perf work isn't blocked.

Silent wrong answer with a zero exit code — an async entry point can evaporate and CI would call it a pass.