Use Tuples instead of ArrayLike types

[vecerek]

Assume the following code:

const loadResults = (): Promise<Array<Result | Error>> => {
  const [a, b] = loader.loadMany(["1", "2"]);

  // TypeError: "a" and "b" can both be undefined
  if (a.prop === b.prop) {
    return [a];
  }

  return [a, b];
}

In the above code, both a and b can be undefined because the ArrayLike type does not guarantee the presence of any element; basically, loadMany could still be an empty array (based on the type). However, based on the logic implemented in this library, I believe the number of results will always match the number of keys in the input. Hence, the use of tuples makes more sense, in my opinion.

What do you think?

[linux-foundation-easycla[bot]]

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[vecerek]

Closing this, my mistake. I thought variadic tuple types could express the relationship between the cardinality of arguments and the return type in a generic way but they can't 🙁