from typing import Tuple, Optional


def foo(value: Optional[int]) -> None:
    """"Optional argument of type int with default value set in runtime."""
    if value is None:
        value = 42
    reveal_type(value)  # builtins.int
    value.bit_length()  # no error


def bar(value: Tuple[int, list]) -> None:
    """Argument of a tuple type."""
    reveal_type(value)     # Tuple[builtins.int, builtins.list[Any]]
    reveal_type(value[0])  # builtins.int
    reveal_type(value[1])  # builtins.list[Any]
    value[1].sort()  # no errors


def baz(value: Optional[Tuple[int, list]]) -> None:
    """mypy loses actual type of argument after setting default value in runtime."""
    if value is None:
        value = (0, [])  # no errors here, types match
    # unexpected Union type below, notice both elements are identical
    reveal_type(value)     # Union[Tuple[builtins.int, builtins.list[Any]], Tuple[builtins.int, builtins.list[Any]]]
    # now we have only garbage
    reveal_type(value[0])  # Union[builtins.object*, Any]
    reveal_type(value[1])  # Union[builtins.object*, Any]
    value[1].sort()  # error: Item "object" of "Union[object, Any]" has no attribute "sort"