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sys.platform != "foo" defeats platform-specific path #18873
Description
import sys
def foo() -> None:
if sys.platform != "darwin":
print("not darwin")
return
print("darwin")$ mypy --platform linux plat.py
plat.py: note: In function "foo":
plat.py:9:5: error: Statement is unreachable [unreachable]
print("darwin")
^~~~~~~~~~~~~~~
Found 1 error in 1 file (checked 1 source file)mypy claims to understand sys.platform checks, yet is defeated by !=.
I would expect mypy not to warn about unreachable code here:
- I am not assigning sys.platform to an intermediate
- I am checking against a literal value (which in the documentation mypy also claims to understand).
Activity
brianschubert commented on Apr 2, 2025
Thanks for the report. Platform checks currently only apply within the if/elif/else statement. If you use an explicit else branch, this will work as expected:
Closing as duplicate of #10773