Bug Report
some narrowing goes wrong and mypy ends up getting confused with a bunch of self-union types (A | A) and spurious errors
I'm not entirely sure the cause however
To Reproduce
from typing import NamedTuple
class AKey(NamedTuple):
k: str
class A(NamedTuple):
key: AKey
s: str
class BKey(NamedTuple):
k: str
class B(NamedTuple):
key: BKey
s: str
def f(x: A | B | str) -> A | B | str:
if isinstance(x, str):
return x
else:
return x._replace(s='wat')Expected Behavior
no errors from the given snippet
Actual Behavior
$ mypy t3.py
t3.py:24: error: Invalid self argument "A | A" to attribute function "_replace" with type "Callable[[_NT, DefaultNamedArg(AKey, 'key'), DefaultNamedArg(str, 's')], _NT]" [misc]
t3.py:24: error: Invalid self argument "B | B" to attribute function "_replace" with type "Callable[[_NT, DefaultNamedArg(BKey, 'key'), DefaultNamedArg(str, 's')], _NT]" [misc]
t3.py:24: error: Incompatible return value type (got "A | B | A | B", expected "A | B | str") [return-value]
Found 3 errors in 1 file (checked 1 source file)
Your Environment
- Mypy version used: 1.14.0
- Mypy command-line flags: n/a
- Mypy configuration options from
mypy.ini (and other config files): n/a
- Python version used: 3.13.1
Bug Report
some narrowing goes wrong and mypy ends up getting confused with a bunch of self-union types (
A | A) and spurious errorsI'm not entirely sure the cause however
To Reproduce
Expected Behavior
no errors from the given snippet
Actual Behavior
Your Environment
mypy.ini(and other config files): n/a