TypeVars Attempt #2

TypeVars-Attempt-#2.py

from typing import TypeVar
from typing import Tuple
from dataclasses import dataclass


class A:
    def __init__(self, a1): ...

@dataclass
class BBuilder:
    foo: int

    def build(self) -> tuple:
        T = TypeVar('T', bound='B')
        a1_i_dont_want_to_be_changeable = 123

        class B(A):
            def __init__(self, a2):
                super().__init__(a1=a1_i_dont_want_to_be_changeable)

        return (T, B)

my_b_builder = BBuilder(foo=456)

BBuilt: Tuple[TypeVar, ...] = my_b_builder.build()

T2 = TypeVar('T2', bound=BBuilt[0]) # Expected type expression but received "tuple[Unknown, ...]"

BBuiltForReal: T2 = BBuilt[1] # Type variable "T2" has no meaning in this context

my_b: T2 = BBuilt(a2='foo') # Type variable "T2" has no meaning in this context # Object of type "tuple[Unknown, ...]" is not callable