Make == for associative arrays test for equality, not identity. _aaEq was added to runtime/internal/aaA.d which forwards to TypeInfo_AssociativeArray.equals in genobj.d. On the codegen side, DtoAAEquals was added to gen/aa.cpp and is called from EqualExp::toElem in gen/toir.cpp. I assume that the frontend will produce an error if == is used on associative arrays of different type. This fixes DMD bug 1429.

class A(T)
{
   void foo(void delegate (T) d) {}

   void bar()
   {
     foo(delegate void (T t) {});
   }
}

class B: A!(B) {}

class C: A!(C) {}