Type narrowing broken with negative integer literals #10514
Description
Bug Report
Type narrowing seems to be broken for negative integer literals. Wild guess: This probably happens because they are not a single entity, but a unary minus applied to a positive integer. Funnily enough, the non-overlapping equality check seems to get this right.
To Reproduce
Consider the following code:
from typing import Literal, Union
Foo = Union[Literal[-1], Literal[42]]
def correct(f: Foo) -> None:
if f == 42:
reveal_type(f) # Revealed type is 'Literal[42]'
else:
reveal_type(f) # Revealed type is 'Literal[-1]'
def also_correct(f: Foo) -> None:
if f == -2:
reveal_type(f) # Non-overlapping equality check (left operand type: "Union[Literal[-1], Literal[42]]", right operand type: "Literal[-2]")
else:
reveal_type(f) # Revealed type is 'Union[Literal[-1], Literal[42]]'
def wrong(f: Foo) -> None:
if f == -1:
reveal_type(f) # Revealed type is '<nothing>'
else:
reveal_type(f) # Revealed type is 'Union[Literal[-1], Literal[42]]'Expected Behavior
The revealed types in wrong should be the same as in correct, only swapped.
Actual Behavior
Mypy is confused. 😉
Your Environment
- Mypy version used: 0.812
- Python version used: 3.8.10