[red-knot] Panics on (some) starred expressions in annotations

[sharkdp]

Red knot currently panics on some instances of starred expressions (at the outermost layer) of type annotations. An actual example where something like this would occur is in variadic generics (the *Ts):

Ts = TypeVarTuple("Ts")

def append_int(*args: *Ts) -> tuple[*Ts, int]: …

In this particular case, we currently do not panic since we never run deferred inference on that parameter type. But we would panic if we were to implement function parameter inference.

A case which does lead to a panic is the following (invalid syntax) example:

def f() -> *int: ...
f()

(it's important that this occurs as a return type and that the function is actually called; it doesn't work otherwise)

A fix for this is already ready at #14106