Dead code is not detected after a never returning function call

[3n-mb]

Related to #13957

TypeScript Version: 2.1.4
"strictNullChecks": true

Code

function justThrow(): never {
	throw new Error('We throw');
}

function makeString(n: number): string {
	justThrow();
	return `This is a dead code`;
}

Expected behavior:
Report that there is an unreachable (dead) code after a call to never returning function.

Actual behavior:
Dead code is not detected.

[RyanCavanaugh]

Flow control and function type analysis are done in two passes that don't fully interact with each other yet. Tons of open issues on this already, see #12825 as a starting point.