mypy-play

from typing import Any, Generic, TypeVarTuple, TypeVar, Concatenate, Tuple, Unpack, ParamSpec, Optional, TypedDict, Required, NotRequired

T = TypeVar('T')
TT = TypeVarTuple('TT')
TTF = TypeVarTuple('TTF')
P = ParamSpec('P')

class Base():
    @classmethod
    def do(cls, *args, **kwargs):

mypy-play

from typing import Never

def very_sound_function() -> float:
    y: list[Never] = []
    return next(iter(y)).startswith("xyz")  # type checker approved!
    #      ^^^^^^^^^^^^^ this may have been a good place to error
    #                    if we really believed Never was uninhabited.

def make_never() -> Never:
    while True:

mypy-play

from typing import Never

def foo() -> Never:
    while True:
        pass

def baz(arg: object) -> None: pass

def bar() -> None:
    return baz(foo())  # undetected unreachable code

mypy-play

from typing import Never

def foo() -> Never:
    while True:
        pass

def bar() -> tuple[int, ...]:
    return (foo(),)  # undetected unreachable code
    
x = bar()

mypy-play

from typing import Never

def foo() -> Never:
    while True:
        pass

def bar() -> tuple[int, ...]:
    return (foo(),)  # undetected unreachable
    
x = bar()

mypy-play

import sys
from typing import final

@final
class A: ...

@final
class B: ...

if sys.version_info >= (3, 14):

mypy-play

# mypy: disable-error-code=empty-body

from typing import Protocol, Any
from typing_extensions import Never
from collections.abc import Callable

class KWOnlyFactory(Protocol):
    def __call__(self, cls: type[Any], /, **kwargs: Any) -> Never: ...

class Shape(Protocol):

mypy-play

# mypy: disable-error-code=empty-body

from typing import Protocol, Any
from typing_extensions import Never
from collections.abc import Callable

class Factory(Protocol):
    def __call__(self, cls: type[Any], /, **kwargs: Any) -> Never: ...

class Shape(Protocol):

mypy-play

# mypy: disable-error-code=empty-body

from typing import Protocol, Any
from typing_extensions import Never
from collections.abc import Callable

class Factory(Protocol):
    def __call__(self, cls: type[Any], /, **kwargs: Any) -> Never: ...

class Shape(Protocol):

mypy-play

from typing import Callable, Generic, Literal, Protocol, Type, overload
from typing_extensions import ParamSpec

P = ParamSpec('P')

class Shape[**P](Protocol):
    def __init__(self, *args: P.args, **kwargs: P.kwargs) -> None: ...
    def area(self) -> float: ...
    def perimeter(self) -> float: ...