Compiler bug? Addition/subtraction code

[Era Scarecrow via D.gnu]

Passes in DMD compiler, but breaks in GDC during assert tests.

B4S1L3 suggested it might be an old compiler bug. I need 
confirmation if this is an old (not yet caught up) or a new one 
(to which I'll have to write or have a work-around until the bug 
is fixed).

// http://dpaste.com/0M7M8NK
uint[] sub(uint[] lhs, const (uint)[] rhs) {
     long t;    //temporary, doubles as carry

     foreach(i, ref v; lhs) {
         t += v;
         t -= rhs[i];
         v = cast(uint) t;
         //reset carry
         t >>= uint.sizeof*8;
     }

     return lhs;
}

unittest {
     uint[3] lhs = [99, 201, 300],
             rhs = [-1, 0, 0];

     assert(sub(lhs, rhs) == [100, 200, 300]);
}