Type inference error for tuples

[jzhang1]

TypeScript Version: 2.0.0

Code

// A *self-contained* demonstration of the problem follows...
coords: [number, number][] = [[0,0], [1,1]];
transformed: [number, number][] = coords.map(([x, y]) => [x+1, y+1]);

Expected behavior:
This type checks

Actual behavior:
coords.map is infered to have type number[][] instead of [number, number][]

[kitsonk]

Dupe of #6574

[DanielRosenwasser]

In the mean time, you can easily fix this by adding a type annotation to map's callback.

coords.map(([x, y]): [number, number] => [x+1, y+1]);

[DanielRosenwasser]

Thanks for deduping @kitsonk!