New GitHub issue #96385 from sobolevn:<br>
<hr>
<pre>
Right now there's an uncovered branch in `TypeVarTuple.__typing_prepare_subst__`:
<img width="775" alt="Снимок экрана 2022-08-29 в 15 16 14" src="https://user-images.githubusercontent.com/4660275/187199050-d95b0e39-d260-4fcd-aef6-ebd376019648.png">
And it looks like there's a bug in it, these two lines:
```python
for param in enumerate(params[typevartuple_index + 1:]):
if isinstance(param, TypeVarTuple):
```
This `if` will never be executed, because `enumerate` always returns `tuple[int, T]`, it is never `TypeVarTuple`.
So, I think that we need to remove `enumerate()` call here and add a test like:
```python
>>> from typing import Generic, TypeVarTuple
>>> V = TypeVarTuple('V')
>>> T = TypeVarTuple('T')
>>> class My(Generic[*T]): pass
...
>>> My[*T, *V][*V]
TypeError: More than one TypeVarTuple parameter in __main__.My[*T, *V]
```
I will send a PR 😉
</pre>
<hr>
<a href="https://github.com/python/cpython/issues/96385">View on GitHub</a>
<p>Labels: type-bug</p>
<p>Assignee: sobolevn</p>