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| author | Yurii Karabas <1998uriyyo@gmail.com> | 2021-08-18 19:08:32 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2021-08-18 19:08:32 (GMT) |
| commit | a3a4d20d6798aa2975428d51f3a4f890248810cb (patch) | |
| tree | 96f00098fbd62759b13d7997efd315047da3ca18 /Lib/typing.py | |
| parent | 6fb62b42f4db56ed5efe0ca4c1059049276c1083 (diff) | |
| download | cpython-a3a4d20d6798aa2975428d51f3a4f890248810cb.zip cpython-a3a4d20d6798aa2975428d51f3a4f890248810cb.tar.gz cpython-a3a4d20d6798aa2975428d51f3a4f890248810cb.tar.bz2 | |
bpo-44524: Fix cryptic TypeError message when trying to subclass special forms in `typing` (GH-27710)
This was a Python 3.9 regression.
Diffstat (limited to 'Lib/typing.py')
| -rw-r--r-- | Lib/typing.py | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/Lib/typing.py b/Lib/typing.py index 51468ae..eeeb295 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -1086,6 +1086,9 @@ class _GenericAlias(_BaseGenericAlias, _root=True): return operator.getitem, (origin, args) def __mro_entries__(self, bases): + if isinstance(self.__origin__, _SpecialForm): + raise TypeError(f"Cannot subclass {self!r}") + if self._name: # generic version of an ABC or built-in class return super().__mro_entries__(bases) if self.__origin__ is Generic: |