Use built-in Self type in __init__.pyi when available

[adriengcql]

Starting in python 3.11 the typing module has a Self type that does the equivalent of the SelfT typevar.

This integrate a bit better with type checkers.
Seen with ty in class inheritance (it is essentially a problem in ty but is a sounds like a good occasion to make the update):

from frozendict import frozendict

class MyDict(frozendict[int, int]):
    pass


a = MyDict()
b = a.set(1, 1)

test.py:8:5: error[no-matching-overload] No overload of function `__new__` matches arguments
test.py:9:5: error[no-matching-overload] No overload of bound method `set` matches arguments

[Marco-Sulla]

Failed for Python 3.8 - 3.10:

  typed.py:24: error: Expression is of type "Any", not "frozendict[str, int]"  [assert-type]
  typed.py:25: error: Expression is of type "Any", not "frozendict[str, int]"  [assert-type]
  typed.py:40: error: Expression is of type "Any", not "frozendict[str, int]"  [assert-type]
  typed.py:42: error: Expression is of type "Any", not "frozendict[str, int]"  [assert-type]
  typed.py:47: error: Expression is of type "Any", not "frozendict[str, int]"  [assert-type]
  typed.py:56: error: Expression is of type "Any", not "frozendict[str, int]"  [assert-type]

Notice that it doesn't fail on every archs because type checking is only enabled for the primary workflow. Furthermore it doesn't fail on 3.6 - 3.7 because typing_extension is only available for 3.8+.

It's quite strange it doesn't work. Maybe it's a stupid idea, but try moving the import at the same level of the other imports, just before K = TypeVar("K"). It's also desired for a matter of style.

[adriengcql]

Thanks for the insight, it seems not to work well with ImportError so I switched to a condition on the python version.

[Marco-Sulla]

It's odd. It works for TypeVar, for example, and not for Self. Mah. Typing in Python gives me an headache every time. There should be a more obvious way to do typing in py, but I'm not Dutch.

[Marco-Sulla]

Anyway, ty for the improvement.