[paugier]

I propose that args_m be a W_MetaArgs (a subtype of W_InterpTuple).

This has two advantages:

• STATIC_TYPE(args_m[0]) == MetaArg so that tup = (args_m[0], args_m[1]) just works.

• we can add helper attributes specific to args_m, like:

  • args_m.loc (useful for metafunc similar to Rust macros todo!(), unimplemented!(), file!() and line!()) and

  • args_m.types, which should be useful for metaprog, typically:

        @blue.metafunc
        def __new__(*args_m):

            def new(*args: *args_m.types) -> cls:  # PEP 646
                self = cls.__make__(gc_alloc[Data](1))
                self.__init__(*args)
                return self

            return OpSpec(new)