https://issues.dlang.org/show_bug.cgi?id=13875

          Issue ID: 13875
           Summary: extern(C++) interfaces cannot be used as associative
                    array keys
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: DMD
          Assignee: nobody@puremagic.com
          Reporter: redballoon36@gmail.com

Example code:
test.cpp:
class Inter
{
    virtual ~Inter() { }
};

Inter * newInter()
{
    return new Inter;
}

test.d:
extern(C++) interface Inter
{
}

extern(C++) Inter newInter();

void main()
{
    int[Inter] map;
    Inter i = newInter();
    map[i] = 5;
}

Compiling these two files succeeds.  The generated code segmentation faults in:
#0  0x000000000041aac9 in object.TypeInfo_Interface.getHash(const(void*)) ()
#1  0x000000000041b1a2 in _aaGetX ()
#2  0x000000000041a50a in D main () at test.d:11

If this is not supposed to be allowed, since Inter does not have the right toHash or something, then I think that int[Inter] should produce an error.

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