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.

static foocalled = false;
static barcalled = false;
void foo() { foocalled = true; }
void bar() { barcalled = true; }

void f(bool b)
{
  return b ? foo() : bar();
}

void main()
{
  f(true);
  assert(foocalled && !barcalled);
  f(false);
  assert(foocalled && barcalled);
}