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Tuple vs arrays casting mismatch #16391
Description
TypeScript Version: 2.2.1 / nightly (2.2.0-dev.201xxxxx)
export interface Vector {
x:number;
y:number;
}
type Point = [number, number];
const Vectors: Vector[] = [];
// Error in the affectation
const points:Array<Point> = Vectors.map((Vector) => {
return [Vector.x, Vector.y];
});
// This is working
const pointsOk:Array<Point> = Vectors.map((Vector) => {
return <Point>[Vector.x, Vector.y];
});Expected behavior:
The compiler should understand I am returning a tuple and not an array of values
Actual behavior:
I get an error and need to cast the conversion to get the right behaviour
Activity
w0rp commentedon Jul 25, 2017
I have just encountered this same issue myself.
I think the compiler should infer
[1, 2]as[number, number], and allow[number, number]to be assigned tonumber[]. The same should hold for[1, 'a']being inferred as[number, string]which should be allowed to be assigned to(number | string)[].RyanCavanaugh commentedon Jul 25, 2017
See #11924 (comment) / #10195