Array.prototype.filter misses undefined in returning value

[ezubarev]

TypeScript Version: 2.4.0

Code

const values = [1, 2];
values.filter((value) => value === 3)[0];

Expected behavior:
Object is possibly 'undefined'.

Actual behavior:
No errors.

[aluanhaddad]

The type of values is number[] not [number, number] or [1, 2]. Even if tuple types were used however, this still would not be an error.

See #6229

[ezubarev]

values.filter((value) => value === 3) is undefined in this case. It doesn't link with provided issue.

[kitsonk]

Duplicate of #13778

It is a conscious decision to favour usability over correctness, though the linked issue indicates it is open for further discussion.

[RyanCavanaugh]

We assume that you are bounds-checking yourself correctly since the alternative is quite a bit worse. See linked issues above.