Overloads for argument with default value doesn't recognize signature when argument is omitted

[Xoriun]

In the following code, there is a bool argument with default value False and overloads to specify the return type depending on this argument.

from typing import Literal, overload

@overload
def func(a: Literal[True]) -> int: ...
@overload
def func(a: Literal[False]) -> str: ...

def func(a: bool = False) -> int | str:
    return 1 if a else 'ssdf'

This works as expected as long as this optional argument is used when calling the function, but gives an reportCallIssue when not using it:

a: int = func(True)  # fine
b: str = func(False) # fine
c: str = func()      # error

Of course, adding the overload

@overload
def func() -> str: ...

solves the issue.

Now, is this third overload something that pyright could/should imply by the provided default argument or does leaving it out violate some official rule for type checkers?

[Daraan]

Hi, you need to add the default value to the overloaded signature as well. Otherwise there is no option for zero arguments:

from typing import Literal, overload

@overload
def func(a: Literal[True]) -> int: ...

# Default case:
@overload
def func(a: Literal[False] = False) -> str: ...

def func(a: bool = False) -> int | str:
    return 1 if a else 'ssdf'

a: int = func(True)  # fine
b: str = func(False) # fine
c: str = func()      # fine

[Xoriun]

Thank you, I just didn't think to provide the default value in the overload...