mypy-play

from typing import Literal, reveal_type

def sign(x: int) -> Literal[-1, 0, 1]:
    """Extracts the sign of x."""
    s = -1 if x < 0 else (0 if x == 0 else 1)
    reveal_type(s)  # int
    match s:
        case -1 | 0 | 1:
            reveal_type(s)  # narrowed to Literal[-1, 0, 1]
            return s

mypy-play

from typing import Any, cast, Generic, overload, Self, TypeVar

T = TypeVar('T')

class CustomProperty(property, Generic[T]):
    @overload
    def __get__(self, instance: None, owner: type | None = None, /) -> Self: ...

    @overload
    def __get__(self, instance: Any, owner: type | None = None, /) -> T: ...

mypy-play

from typing import Any, cast, Generic, overload, Self, TypeVar

T = TypeVar('T')

class CustomProperty(property, Generic[T]):
    @overload  # type: ignore[override]
    def __get__(self, instance: None, owner: type[Any] | None, /) -> Self: ...

    @overload
    def __get__(self, instance: Any, owner: type[Any] | None, /) -> T: ...

mypy-play

from typing import Any, cast, Generic, overload, Self, TypeVar

T = TypeVar('T')

class CustomProperty(property, Generic[T]):
    @overload  # type: ignore[override]
    def __get__(self, instance: None, owner: type[Any] | None, /) -> Self: ...

    @overload
    def __get__(self, instance: Any, owner: type[Any] | None, /) -> T: ...

mypy-play

t1 = ()
t2 = tuple()

reveal_type(t1)   # tuple[()]
reveal_type(t2)   # tuple[Any, ...]


foo = lambda: list(t1)
bar = lambda: list(t2)
qux = lambda: list(tuple())

mypy-play

# mypy: no-strict-optional
from typing import overload, Protocol

class Descriptor:
    @overload
    def __get__(self, instance: None, owner: type) -> int: ...

    @overload
    def __get__(self, instance: object, owner: type) -> str: ...

mypy-play

from typing import Protocol, final

@final
class Inter(Protocol):
    x: int
    
    def y(self) -> int:
        ...

mypy-play

from typing import Protocol, final

@final
class Inter(Protocol):
    x: int
    
    def y(self) -> int:
        ...

    @property

mypy-play

class X:
    val: object
    
class Y(X):
    @property
    def val(self) -> object:
        return object()
    @val.setter
    def val(self, value):
        self.x = True

mypy-play

from typing import Protocol, final

@final
class Inter(Protocol):
    x: int
    
    def y(self) -> int:
        ...

    @property