Excess properties check does not occur for object literals in conditional expressions

[Knagis]

TypeScript Version: 2.1.4 / 2.1.4-insiders.20161201

Code

Code on playground

interface IFoo {
    foo?: number;
    bar?: number;
}

let a: IFoo = {
    foo: 1,
    asd: 2 // this line shows error
};

let b = true;
let c: IFoo =
    b ? {
        asd: 2 // this line shows error
    } : {
        foo: 1,
        asd: 2 // this line does NOT show an error
    }

Also this version fails:

let c: IFoo =
    b ? {
    } : {
        foo: 1,
        asd: 2 // this line does NOT show an error
    }

Expected behavior:
All asd:2 assignments should show an error

Actual behavior:
Only the first two show the error, the last one does not.

[mhegazy]

This is another manifestation of #12745. the result of the conditional operator is a union type, and thus the excess property check is ignored.