Trying to define a generic using the backporked paramspec in python 3.

from typing import Generic
from typing_extensions import ParamSpec

p = ParamSpec("p")
class X(Generic[p]):
    pass

You'll run into an exception thrown by this snippet in the Generic class

            if not all(isinstance(p, TypeVar) for p in params):
                raise TypeError(
                    f"Parameters to {cls.__name__}[...] must all be type variables"
                )

In 3.10 this has been changed to allow it as defined by PEP 612

https://github.com/python/cpython/blob/3.10/Lib/typing.py#L1260

From the limitations note in the readme I would expect it to work for static typing checking but fail silently at runtime, instead I get an exception that interrupts program flow.