super simple code, super slow to compile

[Basile B.]

I've found this yesterday while exploring issues:

---
import std.typecons: Typedef;
alias Matrix = double[260][260];
alias Foo = Typedef!Matrix;
void main() {}
---

It's super slow to compile, here 2 seconds. Change the dimension 
of the 2nd static array type to 10 and it's more acceptable.

At first glance I'd say that the compiler is doing something 
stupid.