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Regression: types.NotImplementedType considered @type_check_only #14965
Description
#14717 marked _NotImplementedType as @type_check_only, this causes typing errors when types.NotImplementedType is used in runtime context Code sample in pyright playground
from types import NotImplementedType
assert isinstance(NotImplemented, NotImplementedType)
# "_NotImplementedType" is marked as @type_check_only and can be used only in type annotations (reportGeneralTypeIssues)(this checked fine with pyright 1.1.405 which uses older stub version)
Activity
srittau commentedon Nov 2, 2025
It probably makes sense to move
_NotImplementedTypetotypes, renaming it, and removing the@type_check_onlymarker. I'm not sure why it is inbuiltins.pyiin the first place, possibly for historic reasons.