"is" expression and type tuples

[Jack Applegame via Digitalmars-d-learn]

Seems like "is" expression doesn't support type tuples:

> pragma(msg, is(short : int));                 // true
>
> enum Test(ARGS...) = is(ARGS[0..2] : ARGS[2..4]);
> pragma(msg, is(Test!(int, int, int, int)));   // false
> pragma(msg, Test!(int, short, int, int));     // false

Is it by design, or just not implemented?