map() type inference incomplete

[ithinkihaveacat]

Code

const foo = [1, 2, 3].map(() => [1, 2]);
const bar = new Map<number, number>(foo)

Expected behavior:

No error.

Actual behavior:

Type error: Argument of type 'number[][]' is not assignable to parameter of type '[number, number][]'. In this case, foo will always be of the form [number, number][].

[kitsonk]

Essentially duplicate of #16360 (and several other related issues). At the moment, tuple types are never inferred and have to be asserted.

[aluanhaddad]

In the case of Array.prototype.map, you can write

interface Array<T> {
  map<U, V>(callbackfn: (value: T, index: number, array: T[]) => [U, V], thisArg?: {}): [U, V][];
}
const foo = [1, 2, 3].map(() => [1, 2]);
const bar = new Map(foo);

which will resolve this specific error.

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.