(function* (){}).__proto__[Symbol.iterator] = function(){ return this(); };
function* f(){ yield 0; yield 1; }
for (let x of f) console.log(x);

concretely: how do you correctly pass a generator to (e.g.)

function take(n, iterable) {
  if (typeof n !== 'number' || n < 0) throw new TypeError;
  let result = [];
  for (let item of iterable) {
    if (result.length >= n) break;
    result.push(item);
  }
  return result;  
}

?

Just doing take(n, gen()) is wrong: if you do that the generator will never get closed if n is invalid. So... take(n, { [Symbol.iterator]: () => gen() }), I guess? that's dumb.

I notice a mention of a JavaScriptCore bug at https://github.com/lydell/js-tokens?tab=readme-ov-file#safari-warning, and I wonder if it's even possible to test it in test262.

When running let res = /(#)(?:a|b)+/.exec("#" + "a".repeat(1e7)); print(res?.length),

• V8 and SM throw an error (maximum call stack exceeded)
• XS correctly prints 2
• JSC incorrectly prints undefined

It is possible to test something in test262 that in practice in half of the engines throws due to the call stack size?

I would say that it's practical with try..catch that admits only success or RangeError, but also unnecessary here if the scale is reduced a bit:

$ eshost -sx '
  let res = /(#)(?:a|b)+/.exec("#" + "a".repeat(1e6)); 
  if (Array.isArray(res)) {
    print(JSON.stringify(res.map(s => s.length > 9 ? s.slice(0, 3) + "…" + s.slice(-3) : s)));
  } else {
    print(res);
  }
'
#### engine262

RangeError: Maximum call stack size exceeded

#### GraalJS, Hermes, Moddable XS, QuickJS, SpiderMonkey, V8
["#aa…aaa","#"]

#### JavaScriptCore
null