Control flow not formed when using consts

**TypeScript Version:** 2.0.3 **Code** ``` ts interface Releasable { release(): void; } const typeOfNumber: string = 'number'; function release(releasable: number | Releasable): void { if(typeof releasable === typeOfNumber) { allocated.splice(allocated.indexOf(releasable), 1); } else { releasable.release(); } } ``` **Expected behavior:** ``` ts interface Releasable { release(): void; } const typeOfNumber: string = 'number'; function release(releasable: number | Releasable): void { if(typeof releasable === typeOfNumber) { allocated.splice(allocated.indexOf(releasable), 1); // Ok, typeof releasable is number here } else { releasable.release(); // Ok, typeof releasable implements Releasable here } } ``` **Actual behavior:** ``` ts interface Releasable { release(): void; } const typeOfNumber: string = 'number'; function release(releasable: number | Releasable): void { if(typeof releasable === typeOfNumber) { allocated.splice(allocated.indexOf(releasable), 1); // [ts] Argument of type 'number | Releasable' is not assignable to parameter of type 'number'. Type 'Releasable' is not assignable to type 'number'. } else { releasable.release(); // [ts] Property 'release' does not exist on type 'number | Releasable'. } } ``` Currently type guards are only limited to literals. Type guards are consumed at compile time and from this taken in mind variables defined with `let` or `var` seems natural to not result in proper control flow but type guards using constants defined with `const` should result in a proper type guard. Since the compiler already knows that `const`s will not change their value ans so their value should be checked dose it evaluate to known `typeof` return value to form a proper control flow else to result in a `[ts] error` ...