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nested isinstances lose type information #10146
Description
Bug Report
To Reproduce
x = object()
if isinstance(x, (int, str)):
reveal_type(x) # Union[int, str]
if isinstance(x, int):
pass
reveal_type(x) # objectExpected Behavior
both types revealed as Union[int, str]
Actual Behavior
object from second type
Your Environment
- Mypy version used: latest master (0.820+dev.72ac2cee910ca61bfdf449217328b6d10b45d378)
- Mypy command-line flags: none
- Mypy configuration options from
mypy.ini(and other config files): none - Python version used: 3.7.3
- Operating system and version: debian 10 based linux distro
Activity
JukkaL commentedon Mar 5, 2021
It looks like we should perhaps maintain a stack of narrowed down types (though I might be wrong).
erictraut commentedon Aug 12, 2023
This is another example of join vs union. It should probably be tagged as such.