How DMD's -w *Prevents* Me From Seeing My Warnings

[strtr]

or: Why does dmd keep on crashing on my code :)
(I blame it on the average D programming; they don't write enough crappy code ) 

After reading the -w post I tried using the -w switch again and it also prevents me from seeing all my warning, but for a different reason : it crashes dmd :(

Before crashing a few correct warnings are shown :
warning - tests.d(232): Error: implicit conversion of expression (i1) of type uint to ubyte can cause loss of data

Somehow I used size_t like this:
struct S {
  ubyte[4] ub;
  void opIndex(size_t i1, size_t i2, size_t i3, size_t i4) {
    ub[0] = i1;
...
}
I have no clue as to why I put size_t there but replacing them with ubyte seems to fix the crashing problem. 

I can't replicate the crash in something small using only the struct or something  :(
Somehow it only works when at least twenty modules are imported in (indirectly) and a lot of them have circular dependencies.