Using ellipsis in a TypeVarTuple

[MilanStaffehl]

I want to have an alias for tuple, but I wish to keep it general purpose, so I am parametrizing it with a TypeVarTuple:

from typing import TypeVarTuple

_ShapeTypeVar = TypeVarTuple('_ShapeTypeVar')
Shape = tuple[*_ShapeTypeVar]

x: Shape[int, ...]

This works fine for all types (i.e. I can use this type like Shape[int, str, float]), but does not work for ellipses. If I use my alias with an ellipsis, all type checkers give me an error, stating that this is not supported behavior:

C:\Desktop> mypy tmp.py
tmp.py:6: error: Unexpected "..."  [misc]

C:\Desktop> pyright tmp.py
C:\Desktop\tmp.py:6:15 - error: "..." is not allowed in this context

So, either I am not understanding the typing system correctly, or there is something not quite right. I want to make sure I am not doing it completely wrong, so any guidance would be appreciated.

Some things I have tried:

• Using typing.Tuple yields the same result.
• Using class Shape[tuple[*_ShapeTypeVar]] yields the same result.
• Using Shape[*Tuple[int, ..]] or Shape[*tuple[int, ...]] works, but is somewhat unsatisfying and unintuitive.

Is this a valid way to create an alias for tuple or am I doing it wrong? Are ellipses just not valid in a TypeVarTuple? If so, what is the correct way to get a parametrized alias of tuple that supports ellipses?

[erictraut]

The ... token isn't allowed in the specialization of a class parameterized by a TypeVarTuple. It's allowed only for the tuple class as discussed here in the typing spec.

You can use an unpacked tuple to specialize a class parameterized with a TypeVarTuple, like this:

x: Shape[*tuple[int, ...]]

For more information, refer to the TypeVarTuple section of the typing spec.

[MilanStaffehl]

Thanks, the second link clears up a lot of confusion for me!