generic subclasss and typevar with constraint

Not sure if this is a "bug" or I didn't understand generics, but

import typing

T = typing.TypeVar('T', str, int)


class Base(typing.Generic[T]):

    def __init__(self, bar: T):
        self.bar: T = bar


class Child(Base[T]):

    def __init__(self, bar: T):
        super().__init__(bar)

mypy 0.720 (on windows) says

> mypy.exe test\__init__.py
test\__init__.py:15: error: Argument 1 to "__init__" of "Base" has incompatible type "str"; expected "T"
test\__init__.py:15: error: Argument 1 to "__init__" of "Base" has incompatible type "int"; expected "T"

but if I change the T definition to T = typing.TypeVar('T') the errors go away

What I want is to specify that

• the "Base" constructor has a parameter that could be an int or a str
• the "Child" constructor has the same "signature" of the "Base" one (well, this is a simplified example, I want something more...)

is this a bug? di I misinterpreted the TypeVar usage?

Reproduisez l’exemple de test_init_.py avec mypy 0.720, en comparant le TypeVar contraint avec la version non contrainte. Examinez les chemins pertinents du code générique et de vérification de TypeVar, puis déterminez si le diagnostic signalé est attendu ; le travail est terminé lorsque le comportement est documenté ou qu’un test de régression est ajouté et que le problème est corrigé s’il s’agit d’un bug.