Strict object literal checking with union type

[Lenne231]

TypeScript Version: 1.8.0

Is this a bug or does it work as intended?

Code

type Test = { a: string; } | { b:number };

var t1 : Test = { a: '...', b: 3 }; // ok
var t2 : Test = { a: '...', b: '...' }; // ok but should be error!?
var t3 : Test = { a: '...', c: '...' }; // error

var a4 : { a: string; } = { a: '...', b: '...' }; // error

Expected behavior:
var t2 : Test = { a: '...', b: '...' }; should throw a compiler error as well because b is of type string and not number.

Actual behavior:
There is no compiler error.

[DanielRosenwasser]

Linking to a previous discussion at #4452.

[DanielRosenwasser]

@Lenne231 is there a specific scenario you were hit by this?

[Lenne231]

Not a specific scenario, i was just playing around with union types.