Restrict type 'T' to be the exact type passed to constraint()

type_constraint.py

from __future__ import annotations

class _ExactType[T]:
    def __init__(self, tp: type[T]) -> None:
        self.tp = tp

def constraint[T](tp: type[T]) -> _ExactType[T]:
    return _ExactType(tp)


class _Option[T]:
    ...

def make_option[T](tp: _ExactType[T], *, default: T) -> _Option[T]:
    raise NotImplementedError


class Animal():
    ...

class Cat(Animal):
    ...


# ok
make_option(constraint(str), default='')
make_option(constraint(int), default=0)
make_option(constraint(Animal), default=Cat())

# error
make_option(int, default=0)
make_option(constraint(str), default=0)
make_option(constraint(Cat), default=Animal())