Improved Overload Resolution

[3ok]

Hi 👋

I have been using Pylance as my language server for Python development, and I have noticed an issue with overload resolution. Specifically, when I define multiple overloads for a function, Pylance does not always suggest the correct overload based on the arguments provided.

For example, consider the following code:

from typing import Any, Literal, overload, Union

@overload
def foo(name: Literal["bunny"], *, color: str, **kwargs: Any) -> str: ...

@overload
def foo(name: Literal["human"], *, age: int, **kwargs: Any) -> int: ...

@overload
def foo(name: str, **kwargs: Any) -> None: ...

def foo(name: str, **kwargs: Any) -> Union[None, str, int]:
    if (
        name == "bunny" and
        "color" in kwargs and
        isinstance(kwargs["color"], str)
    ):
        return kwargs["color"]
    elif (
        name == "human" and
        "age" in kwargs and
        isinstance(kwargs["age"], int)
    ):
        return kwargs["age"]
    else:
        return None

When I start typing a call to the foo function with the argument "human", and VSCode/Pylance suggests overloads, it always shows the first overload (the "bunny" 🐰 one) , even though it is not the most relevant one in this case.

I would have expected that either the second or third overload would be shown instead of the first one that is no longer relevant. Automatically going to 2 / 3 or 3 / 3 (or removing the first overload from being shown, i.e. have something like n / 2) would be more user-friendly IMO, especially in cases where there is a lot of overloads.

Thanks!

[erictraut]

This is related to this work item. We've implemented the necessary support in the type evaluator to determine which overloads are applicable for a call expression. The hover text (tooltip) now applies this filtering, but the signature help (the functionality you're referring to above) has not yet been updated to apply this filtering.

[3ok]

Great to hear that this is being worked on, and I appreciate the update on the current status of the feature. I look forward to seeing the signature help functionality updated to apply the filtering as well. Thank you for the response! 🙂

(I guess we can close this discussion post?)