Consider the following code

function test4(value: 1 | 2) {
    let x: string;
    switch (value) {
    case 1: x = "one"; break;
    case 2: x = "two"; break;
    }
    return x; //There is no path through the switch so x is alwayes assigned here.
}

Expected behavior:
The code should type check under --strict

Actual behavior:
Definite assignment does not realize that the switch is exhaustive and that all paths assign to x, so we get an error.

Checked with 2143a3f