Like so? Code sample inpyright playground

This does seem to work withpyright,mypy seems to bug out on any new call withK≠str. Also:

_m0=Foo.new(bar=3)reveal_type(_m0)# "Foo[str, Unknown]"

Any idea why it fails to bindV=int (or possiblyV=Literal[3])?

Just to make sure that I get this right, when you say:

The types of class-scoped type variables are inferred from argument types only when you call*a constructor.* This doesn't work for other methods.

What exactly counts as*a constructor*? Only the standard constructormetaclass.__call__/__new__/__init__?

Well, actually, ... it does seem to produce the desired inference if we definenew inside a custom metaclass. 🤓 Code sample inpyright playground

I guess this makes sense insofar as that if we were to access, say, some generic class-attributes inside.new, it wouldn't be clear what their types are inside the constructor itself.

So if we want full type-checking for a custom constructor, one either should use a function defined outside the class, a@staticmethod or a custom metaclass (if we need access to certain class-variables at construction time).

Learned something new today, thanks as always for your insights.

Though I have to say, having to define metaclasses makes this whole thing quite un-ergonomic. In fact, there seems to be another type-checker divergence here:

Code sample inpyright playground,https://mypy-play.net/?mypy=latest&python=3.13&gist=d902e42012932c4a8892c75c46d170d4

fromtypingimportSelfclassVector[T]:@classmethoddeffrom_list(cls,x:list[T])->Self: ...# shows mypy: Vector[str], pyright: Vector[Unknown]reveal_type(Vector.from_list(["abc"]))

Would you considermypy's inference in the example above a bug then?