from typing import NoReturn, Any

# Assumption1: NoReturn denotes that the function in question will not pass 
# control back to the calling function, making all code called below it 
# unreachable

# Assumption2: NoReturn denotes that the function in question may or may not
# pass control back to the calling function, but more importantly it does not 
# explicitly return anything and does not contain the return keyword or contains
# the return keyword by itself.


# Functions 1-6 pass mypy checks, comment out functions 7-8 to validate

def function1() -> NoReturn:
    """Exact behavior of scenario in official docs"""
    raise RuntimeError('no way')


def function2() -> NoReturn:
    """This function should be functionally identical to function7() in that it
    implicitly returns None but does not contain the return keyword. This 
    matches the 
    [mypy test implementation](https://github.com/ilevkivskyi/mypy/blob/5af9597a0a8e6b16075637145f15178130a659a1/test-data/unit/check-flags.test#L154)
    and does not generate the error 
    `error: Implicit return in function which does not return` in mypy that 
    function7 does, though it is functionally identical (as far as type goes).
    """
    pass


def function3() -> None:
    """This function implicitly returns None, but the return keyword is used. 
    If NoReturn is used here, the error 
    `error: Return statement in function which does not return` is generated
    in mypy."""
    return


def function4() -> None:
    """This function explicitly returns None"""
    return None


def function5() -> NoReturn:
    """Arbitrary function created to identify if mypy had special treatment of 
    functions with just `pass` in them"""
    pass


def function6() -> NoReturn:
    """This function should be functionally identical to function7() in that it
    implicitly returns None but does not contain the return keyword. This 
    matches the 
    [mypy test implementation](https://github.com/ilevkivskyi/mypy/blob/5af9597a0a8e6b16075637145f15178130a659a1/test-data/unit/check-flags.test#L154)
    and does not generate the error 
    `error: Implicit return in function which does not return` in mypy that 
    function7 does, though it is functionally identical (as far as type goes).
    """
    function5()
    function5()
    function5()


# Function7 does not pass mypy checks and function8 calls function7, comment out to validate

def function7() -> NoReturn:
    """This function performs actions, but does not explicitly return and does 
    not contain the return keyword. This generates the error 
    `error: Implicit return in function which does not return` in mypy. 
    Implicitly, the returned value is None"""
    1+1


def function8() -> NoReturn:
    """This function should be functionally identical to function7() in that it
    implicitly returns None but does not contain the return keyword. This 
    matches the 
    [mypy test implementation](https://github.com/ilevkivskyi/mypy/blob/5af9597a0a8e6b16075637145f15178130a659a1/test-data/unit/check-flags.test#L154)
    and does not generate the error 
    `error: Implicit return in function which does not return` in mypy that 
    function2 does, though it is functionally identical (as far as type goes).
    """
    function7()


def testing() -> None:  # This should be None if assumption1 is correct, NoReturn if assumption2 is correct
    a: None = function1()  # This should cause an error in all cases
    b: None = function2()  # This code is unreachable if assumption1 is correct. If assumption2 is correct it will cause an error like `assigning result of a function call, where the function has no return`
    c: None = function3()  # This code is unreachable if assumption1 is correct, and not necessarily cause an error if assumption2 is correct

    x = function2    # Valid use-case assigning a function to a variable
    y = function2()  # Valid use-case of when the intent might have been to assign a function to a variable, but instead the value of that function was assigned