Functions with never return type as the only call

[sebdoucet]

TypeScript Version: 2.1.4

Code

function foo(): string {
    throwError();
}

function throwError(): never {
    throw new Error();
}

Expected behavior:
Compiling perfectly :)

Actual behavior:
Expect a return value but we already know that the throwError() function never gonna step after.

[RyanCavanaugh]

Discussed at #12825, #8655, #12883, etc