[Python-Dev] Make __class_getitem__ a class method

[Yury Selivanov]

Shouldn't we optimize the usability for pure-Python first, and then for C API?

Right now we have the '__new__' magic method, which isn't a
@classmethod.  Making '__class_getitem__' a @classmethod will confuse
regular Python users.  For example:

   class Foo:
      def __new__(cls, ...): pass

      @classmethod
      def __class_getitem__(cls, item): pass

To me it makes sense that type methods that are supposed to be called
on type by the Python interpreter don't need the classmethod
decorator.

METH_STATIC is a public working API, and in my opinion it's totally
fine if we use it. It's not even hard to use it, it's just *mildly*
inconvenient at most.

Yury