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Typechecking differs between one-line def of "return expr" vs. "r = expr; return r" #11985
Description
mypy 0.931
#!/usr/bin/env python3
from collections.abc import Iterable
from typing import Optional
import os
def min_direntry_good(
fs: 'Iterable[os.DirEntry[str]]'
) -> 'Optional[os.DirEntry[str]]':
r = min(fs, default=None, key=lambda x: x.stat().st_mtime)
return r
def min_direntry_bad(
fs: 'Iterable[os.DirEntry[str]]'
) -> 'Optional[os.DirEntry[str]]':
return min(fs, default=None, key=lambda x: x.stat().st_mtime)hober.py:16: error: Item "None" of "Optional[DirEntry[str]]" has no attribute "stat" Found 1 error in 1 file (checked 1 source file)
Activity
drvink commented on Mar 12, 2022
This is still broken in mypy 0.940:
JelleZijlstra commented on Mar 12, 2022
This is likely an issue with mypy's "type context", which infers different types based on the "expected" type. Here it obviously goes wrong, but chances are it's hard to fix it without breaking some other use case.
Extend special case for context-based typevar inference to typevar un…