I've never seen this typing syntax. What is it?

[qexat]

I was coding some random stuff when I discovered a typing syntax I've never seen before:

I suppose it is related to TypeVar since the parameter is one until I do some if isinstance() checks then it falls back to this object*, but what does the star suffix mean?

[erictraut]

See this documentation for details. It effectively means that the type is an intersection between a concrete type and a type variable. In other words, it's an object but it's also a T (or whatever TypeVar it corresponds to).

[echoix]

For future reference, I think that the section referred to is now in this document https://github.com/microsoft/pyright/blob/8f35aa06437f517a03fc68a4ae086ede4e1b6f83/docs/type-concepts-advanced.md#conditional-types-and-type-variables (permalink)