Self resolving vows cause infinite loop

[mhofman]

Describe the bug

Resolving a vow to itself, either directly or through intermediate promises and/or other vows, result in an infinite loop through shortening.

Unlike promise self resolution which at best result in a data lock when awaited, the consequence here is a full livelock (no other work ends up processed while in the infinite loop)

To Reproduce

test.failing('vow self resolution', async t => {
  const zone = makeHeapZone();
  const { watch, when, makeVowKit } = prepareVowTools(zone);

  // A direct self vow resolution
  const { vow: vow1, resolver: resolver1 } = makeVowKit();
  resolver1.resolve(vow1);

  // A self vow resolution through promise
  const { vow: vow2, resolver: resolver2 } = makeVowKit();
  const vow2P = Promise.resolve(vow2);
  resolver2.resolve(vow2P);

  // A 2 vow loop
  const { vow: vow3, resolver: resolver3 } = makeVowKit();
  const { vow: vow4, resolver: resolver4 } = makeVowKit();
  resolver3.resolve(vow4);
  resolver4.resolve(vow3);

  // A head pointing to a 2 vow loop (a lasso?)
  const { vow: vow5, resolver: resolver5 } = makeVowKit();
  resolver5.resolve(vow4);

  const turnTimeout = async n => {
    if (n > 0) {
      return Promise.resolve(n - 1).then(turnTimeout);
    }

    return 'timeout';
  };

  /**
   * @param {number} n
   * @param {Promise<any>} promise
   */
  const raceTurnTimeout = async (n, promise) =>
    Promise.race([promise, turnTimeout(n)]);

  await t.throwsAsync(raceTurnTimeout(20, when(watch(vow1))));

  await t.throwsAsync(raceTurnTimeout(20, when(watch(vow2))));

  await t.throwsAsync(raceTurnTimeout(20, when(watch(vow3))));

  await t.throwsAsync(raceTurnTimeout(20, when(watch(vow5))));
});

Expected behavior

No infinite loop

Platform Environment

Additional context

Screenshots