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Better error message if Generic.__init_subclass__ is not called #139905
Description
Bug report
Bug description:
This code (from https://discuss.python.org/t/type-object-cls-has-no-attribute-parameters/104276/4 ):
class Base:
def __init_subclass__(cls) -> None:
pass
class Sub[T](Base): pass
class SubSub(Sub[object]): passFails with an inscrutable error about cls.__parameters__ not existing, because super().__init_subclass__() was not called.
Let's produce a clearer error message in this case so it's easier to debug for the next person.
CPython versions tested on:
CPython main branch
Operating systems tested on:
No response
Linked PRs
- gh-139905: Provide suggestion in error message if
Generic.__init_subclass__was not called #139943 - gh-139905: better error msg when subclassing
GenericAliaswithout calling__init_subclass__#139949 - [3.14] gh-139905: Provide suggestion in error message if
Generic.__init_subclass__was not called (GH-139943) #139955 - [3.13] gh-139905: Provide suggestion in error message if
Generic.__init_subclass__was not called (GH-139943) #139956
Reacted by Alex Waygood and BrenBarn
Activity
gh-139905: Provide suggestion in error message if `Generic.__init_sub…
pythongh-139905: Provide suggestion in error message if `Generic.__in…
pythongh-139905: Provide suggestion in error message if `Generic.__in…
[3.13] gh-139905: Provide suggestion in error message if `Generic.__i…
[3.14] gh-139905: Provide suggestion in error message if `Generic.__i…