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Overloads in super-class for sub-class specific return types #11759
Description
Bug Report
It is probably not good coding style to implement sub-class specific behavior in a super-class, but it would be great to still be able to write type annotations for it.
The sub-class specific overloads in the example below make mypy and pyright correctly infer the return type. Unfortunately, mypy throws an error for the two sub-class specific overloads. Are these false-positives?
To Reproduce
from __future__ import annotations
from typing import overload
class Base:
@overload
def any(self: A) -> bool: # mypy: The erased type of self "test.A" is not a supertype of its class "test.Base"
...
@overload
def any(self: B) -> str: # mypy: The erased type of self "test.B" is not a supertype of its class "test.Base"
...
@overload
def any(self) -> bool | str:
...
def any(self) -> bool | str:
# implementation that handles sub-classes differently
...
class A(Base):
...
class B(Base):
...
# mypy&pyright: bool | str
reveal_type(Base().any())
# mypy&pyright: bool
reveal_type(A().any())
# mypy&pyright: str
reveal_type(B().any())Expected Behavior
No erased type errors?
Actual Behavior
See inline comments.
Your Environment
- Mypy version used: 0.910
- Mypy command-line flags: -
- Mypy configuration options from
mypy.ini(and other config files): - - Python version used: 3.9.6
- Operating system and version: 3.10.0-693.5.2.el7.x86_64
Activity
AlexWaygood commentedon Mar 31, 2022
Is this feature really necessary? You can achieve the same thing just by doing this:
Mypy has no complaints, and it's even more concise.
twoertwein commentedon Mar 31, 2022
Thank you @AlexWaygood, I like it!