typing an init parameter causes wrong argument calculation

[mckaysalisbury]

I've got a class which has a method that creates instances of the class.

class Bar:
    @classmethod
    def create(cls, foo: int):
        return cls(foo)

    def __init__(self, foo: int) -> None:
        pass

When I run mypy against it, it says mypytest.py:4: error: Too many arguments for "Bar"

It seems like a bug to me, because this works fine

class Bar:
    @classmethod
    def create(cls, foo):
        return cls(foo)

    def __init__(self, foo: int) -> None:
        pass

I don't understand why a class method which defines the type of a parameter should break the creation of an instance.

(see https://stackoverflow.com/q/47493293/8384 )

[gvanrossum]

This is because mypy processes definitions in order, and when it comes across create() in the first version it hasn't seen the __init__() signature yet. IIRC there's another issue open for this.

[JelleZijlstra]

Yes, this is #1727.

[mvoitko]

The same problem remains with SQLAlchemy models.