Repository navigation
isinstance(x, (T1, T2)) won't narrow the type of x when NamedTuple is involved. #1914
Description
Test case:
from typing import NamedTuple, Union
A = NamedTuple('A', [('y', int)])
B = NamedTuple('B', [('x', int)])
C = NamedTuple('C', [('x', int)])
def foo(a: Union[A, B, C]):
if isinstance(a, (B, C)):
a.x
b = a # type: Union[B, C]This fails with:
1.py: note: In function "foo":
1.py:9: error: Some element of union has no attribute "x"
1.py:10: error: Incompatible types in assignment (expression has type "Union[A, B, C]", variable has type "Union[B, C]")
The error happens only when NamedTuple is involved. Otherwise the type of a is correctly narrowed to Union[B, C] inside the branch.
cc #1328
$ mypy -V
mypy 0.4.3
$ python3 -V
Python 3.5.2
Activity
ddfisher commentedon Jul 21, 2016
This might be related to #1691.
Add test case
Add test case
Fixes to union simplification, isinstance and more (#3025)
Fixes to union simplification, isinstance and more (#3025)
Fixes to union simplification, isinstance and more (try 2) (#3086)