Promise.all() does not seem to work

Interesting! You're right that wrapping into a function works, thanks!

This works:

function go() {
  var p1 = new Promise(function (res, rej) {
    setTimeout(() => res(1), 250);
  });

  var p2 = new Promise(function (res, rej) {
    setTimeout(() => res(2), 300);
  });

  Promise.all([p1, p2]).then(function () {
    console.log('done', arguments);
  }).catch(function () {
    console.log('FAIL');
  });

  console.log('Promise test');
}

go();

Output:

Promise test
=undefined
done [
  [ 1, 2 ]
 ]

But attempting to use ES6 arrow functions as the Promise executor causes the Puck to completely stop responding and require a powercycle before I can interact with it?

function go() {
var p1 = new Promise((res, rej) => {
    setTimeout(() => res(1), 250);
  });

  var p2 = new Promise((res, rej) => {
    setTimeout(() => res(2), 300);
  });

  Promise.all([p1, p2]).then(function () {
    console.log('done', arguments);
  }).catch(function () {
    console.log('FAIL');
  });

  console.log('Promise test');
}

go();

There's no output after the Espruino logo and version text, the console on the left stops working (can't type any text), and attempting to upload code seems to work, but doesn't execute.
I can disconnect and attempt to reconnect via BLE, which hangs at "Connecting..." – super weird!