Crash upon unpacking undefined name during subclassing

Crash Report & To Reproduce

In the following, tuple[*TS] is a typo (it's supposed to be tuple[*Ts]. See mypy Playground:

class MyTuple[*Ts](tuple[*TS]):
    ...

The typo should report a name-defined error; currently, mypy crashes without reporting the error beforehand.

Traceback

Traceback (most recent call last):
  ...
  File "mypy/semanal_shared.py", line 306, in calculate_tuple_fallback
NotImplementedError

Your Environment

Yep, the old style version crashes with the same exception:

from typing import TypeVarTuple, Generic, Unpack

Ts = TypeVarTuple("Ts")

class MyTuple(tuple[Unpack[TS]], Generic[Unpack[Ts]]):
    ...

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