One of my projects started mysteriously throwing segfaults. I managed to narrow it down to a line in one of my interface's out contracts that compared the result with a value returned by a property method defined on the interface. Even doing `debug stderr.writeln(this);` threw a segfault; GDB says its from the `_d_interface_cast` function.

The full code is too big to post here, but I think I narrowed it down:


	import std.stdio;
	interface A {
		int* aField() @property pure;
		
		int foo()
		out(v) {
			debug stderr.writeln(this.aField);
		}
	}

	class F : A{
		this() {}
		
		int myField;
		
		int* aField() @property pure { return &myField; }
		int foo() {
			debug stderr.writeln(this.aField);
			return 0;
		}
	}

	void main() {
		auto f = new F();
		f.foo();
	}

I expect that this function would print the same address twice; it prints out `aField`, a simple function that returns a pointer to a class member, once in a function body and once in the interface's out contract. Running it with `rdmd -debug test.d` results in the following output:

    7F21F379F010
    6

The first address differs with each run (as expected with memory addresses) but the second line is consistently a 6. Moving the out contract to the implementation of foo method in class F results in the correct output (the same address printed twice).

I suspect that the pointer adjustment that happens with `this` in an out contract is being done incorrectly, but I don't have the skills to diagnose it further.

Using dmd v2.069.1 on x64 XUbuntu