incompatible type "Callable[[], str]"; expected "Callable[[], <nothing>]"

Bug Report

I'm a bit unsure about whether this is supposed to work or not. The example seems to type check in VSCode, indicating that pyright can infer and match the type properly.

To Reproduce

from typing import Union, Callable, TypeVar

T = TypeVar("T")

def my_func(maybe_lazy: Union[Callable[[], T], T]) -> T:
    ...

a: str = my_func("foo")
b: str = my_func(lambda: "foo")

Expected Behavior

Type checks without error.

Actual Behavior

mypy complains with the following in the last line:

main.py:9: error: Argument 1 to "my_func" has incompatible type "Callable[[], str]"; expected "Callable[[], <nothing>]"
main.py:9: error: Return statement in function which does not return

Note that there is spurious "return statement in function which does not return" hinting to a similarity with https://github.com/python/mypy/issues/13014 and https://github.com/python/mypy/issues/10520 but I think this is a coincidence of using a lambda. Modifying the example to

from typing import Union, Callable, TypeVar

T = TypeVar("T")

def my_func(maybe_lazy: Union[Callable[[], T], T]) -> T:
    ...

def produce_a_string() -> str:
    return "foo"

a: str = my_func("foo")
b: str = my_func(produce_a_string)

gets rid of the "return statement in function which does not return" but still errors with "incompatible type".

Your Environment

Reproduction example on mypy playground

• Mypy version used: 0.981
• Mypy command-line flags: None (playground default)
• Mypy configuration options from mypy.ini (and other config files): None (playground default)
• Python version used: 3.10

Start with the linked mypy playground reproduction using the reported Python 3.10 and mypy 0.981 settings. Compare inference for the string argument, lambda, and named function, then verify that both calls type check without the reported Callable or spurious return errors.