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Strange case with deepcopy() and Literal[True] #12001
Description
The following code:
from copy import deepcopy
from typing import Literal, Union
def f(a: str, b: bool) -> Union[Literal[True], str]:
return b or deepcopy(a)
print(f("abc", False))
print(f("abc", True))produces the following output:
$ python3 test.py
abc
True
$ mypy test.py
test.py: note: In function "f":
test.py:5:12: error: Incompatible return value type (got "bool", expected "Union[Literal[True], str]") [return-value]
return b or deepcopy(a)
^
test.py:5:26: error: Argument 1 to "deepcopy" has incompatible type "str"; expected "bool" [arg-type]
return b or deepcopy(a)
^
Found 2 errors in 1 file (checked 1 source file)
$ python3 --version
Python 3.8.10
$ mypy --version
mypy 0.931
$ cat /etc/issue
Ubuntu 20.04.3 LTS \n \l
$ uname -a
Linux ubuntu 5.4.0-94-generic #106-Ubuntu SMP Thu Jan 6 23:58:14 UTC 2022 x86_64 x86_64 x86_64 GNU/LinuxIf deepcopy() call is removed, warnings go away.
In some similar cases only the second warning appears, which looks even weirder.
Activity
[-]Strange case with deepcopy()[/-][+]Strange case with deepcopy() and Literal[True][/+]brianschubert commentedon Dec 8, 2024
Related / duplicate of #10696, just using
orinstead ofand. Both issues have to do with bidirectional inference going awry when analyzing the right operand using the type of the left operand as the type context.Merge branch 'master' into bugfix/pythongh-12001-binary-op-inference-…
Merge branch 'master' into bugfix/pythongh-12001-binary-op-inference-…
Use union of current context and left side for right side narrowing o…