"Used before assigned" error when assigned in a function

[KoltesDigital]

TypeScript Version: 3.0.0-dev.20180712

Search Terms: "Used before assigned"

Code

let angle: number;

function compute() {
	angle = 0;
}

compute();
angle += 2;

Expected behavior:

Passes.

Actual behavior:

error TS2454: Variable 'angle' is used before being assigned.
angle += 2;

[j-oliveras]

Duplicate of #9998.

[KoltesDigital]

Thanks.