Overly strict type narrowing in tuple

[westonpace]

TypeScript Version: 3.2.0-dev.201xxxxx

Search Terms:
type narrowing tuple
type inference tuple

Code

const x: [number, number] = [0, 0];
if (x[0] === 0) {
    x[0] = -1;
}

Expected behavior:
The code should compile. The above code does compile with typescript@3.0.3.

Actual behavior:

error TS2322: Type '-1' is not assignable to type '0'.

Playground Link: http://www.typescriptlang.org/play/

Related Issues:

[ahejlsberg]

Duplicate of #27412.