https://issues.dlang.org/show_bug.cgi?id=14612
--- Comment #8 from Rainer Schuetze <r.sagita...@gmx.de> --- > Actually _d_interface_cast is not so high cost so Object has no > base class and implements no interfaces. It's still a lot more than just a null check and reading a vtbl entry an another indirection. If the instance is from a deeply derived class, _d_interface_cast walks through all base classes to find Object. --