Your link appears not to work (for me) — can you cite what you believe I have incorrect?
This section seems to agree with me, where it explains why normal classes can’t be subclassed to protocols:
> Now, C is a subtype of Proto, and Proto is a subtype of Base. But C cannot be a subtype of Base (since the latter is not a protocol). This situation would be really weird. In addition, there is an ambiguity about whether attributes of Base should become protocol members of Proto.
I’m not sure why you think it’s “obvious” that you can use a third party library to solve the problem — or why that addresses my complaint that the built-in type system doesn’t work for that.
If anything, the existence of a third party library hints the standard library doesn’t cover the use case.
https://peps.python.org/pep-0544/#:~:text=Structural%20subty....
> substituted-for class to be defined as a protocol.
... which is false
> Similarly, the heading on the dictionary says “for a fixed set of keys” — but what if I want a dynamic heterodox dict? Eg, unpacking JSON.
You can quite obviously decode to recursive types (e.g. using pydantic), not sure what the problem is.