This code behaves correctly when compiling with DMD v2.072.0 on Win7. It behaves incorrectly with the same DMD version on OSX.

    import std.stdio;

    auto fn(in cdouble value){
        writeln(value.re + 0i); // Prints 64+0i
        return value.re + 0i;
    }

    unittest{
        writeln(fn(64 + 0i)); // Prints 64+64i, should print 64+0i
    }

It behaves correctly if:

If writeln is removed from fn (In the case where I encountered this bug, there was other essential code but no writeln, I don't think this is related to writeln specifically)

If an empty out contract is added to fn