Your code doesn't type check because you haven't specialized the generic Class in the last line of your code sample. In all previous cases, you've correctly supplied a specialization for the TypeVarTuple.

You can fix this by changing the last line to:

Class[()]().foo(x_no_args)

Ah, thanks didn't know that!

Now for a slight variation. Ideally I'd like to supply a default empty tuple and use the generic class without explicit specialization. This seems to work when an object is instantiated and has its type inferred but not for type annotated variables: mypy playground. The intended use case is for annotated class variables that are instantiated in a metaclass.
This appears to work as expected in pyright

Here's the error I got:

error: Invalid self argument "Class[*tuple[*tuple[()], ...]]" to attribute function "foo" with type "Callable[[Class[*Ts], Callable[[VarArg(*Ts)], None]], None]"  [misc]

This sounds like it could be related to #19110, and maybe also #19105 🤔

I made a fork and added a test case to investigate it but realized it seems to be working as expected on the latest mypy (1.16 vs 1.15 at time of issue report)

Thanks!
closing issue