From python/typeshed#14558: Some classes (like re.Pattern) are not instantiable at runtime:

>>> import re
>>> re.Pattern()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot create 're.Pattern' instances

Currently, there is no working way to mark classes as such. Ideas to mark classes:

• Annotate the return type of __new__ as NoReturn/Never.
• Set __new__ to None (similar to how __hash__ works).
• A new decorator.