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.

module constructors;

import tango.io.Console;

class C
{
    this()
    {
        Cout("C()").newline;
    }
    this(char[] str)
    {
        Cout("C(")(str)(")").newline;
    }
}

class D : C
{
    this()
    {
        super("D");
        Cout("D()").newline;
    }
}

void main()
{
    auto c1 = new C();
    auto c2 = new C("C");
    auto d = new D();
}