assert() vs. enforce(), invariant() vs. ... ?

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> I believe typedef was deprecated due to no-one being able to 
> agree on the semantics (although it's a bit before my time). I 
> think it needs to come back as a very simple concept:
>
> A type duplication. e.g. typedef int myInt; (or typedef myInt = 
> int;) creates a new type that is exactly identical to int, but 
> is a distinct type in the type system.
>
> It should provide *exactly* identical behaviour to e.g. having 
> two structs with identical contents but different names. E.g.
>
> struct A{}
>
> typedef A tA;
> alias A aA;
> alias tA atA;
> typedef aA taA;
>
> assert(!is(tA == A));
> assert(is(aA == A));
> assert(is(atA == tA));
> assert(!is(taA == atA));
> etc....
>
> It's a really basic feature that D ought to have.

I don't understand the difference to alias myInt = int;
Isn't it the same?