[
    ReturnType, ...ArgTypes, Imp
    | Imp == CCodePointer[(Id, SEL, ...ArgTypes), ReturnType]
]
addMethod(
    class,
    selector: Selector[ReturnType, ...ArgTypes],
    imp: Imp
) {
    class_addMethod(
        class,
        selector.sel,
        RawPointer(imp),
        cstring(encode(ReturnType, Id, SEL, ...ArgTypes))
    );
}