or a subclass. This is not a simple process like “call the function at the given address specified by the type”. The runtime has to find out what kind of object add is. Maybe it’s just a function, or maybe it’s a property, or maybe it’s some custom descriptor protocol thing. There’s no way to just turn this into a call instruction! Runtime type information Though dynamic runtimes do not know ahead of time what types variables have at any given opcode, they do eventually find out when the code is run. The first time someone calls