using @declared_attr does not recognize method as a classmethod unless one writes @classmethod explicitly (hence the workaround)

Describe the bug

Further typing refinement is required for sqlalchemy.orm.has_inherited_table as PyCharm currently complains when it’s used both directly inside the DeclarativeBase class and in Mixin classes (as the 2.0 docs suggest).

To Reproduce

from typing import Optional
from sqlalchemy.orm import DeclarativeBase, declared_attr, has_inherited_table

# Scenario 1: Directly within a DeclarativeBase class
class Base(DeclarativeBase):
    @declared_attr.directive
    def __tablename__(cls) -> Optional[str]:
        if has_inherited_table(cls):  # <- PyCharm Warning: Expected type 'Type[_O]', got 'Base' instead
            return None
        return cls.__name__.lower()

# Scenario 2: Within a Mixin class (directly from the 2.0 docs)
class Tablename:
    @declared_attr.directive
    def __tablename__(cls):
        if has_inherited_table(cls):  # <- PyCharm Warning: Expected type 'Type[_O]', got 'Tablename' instead
            return None
        return cls.__name__.lower()

Error

N/A - Non-runtime issue

Versions

• OS: Microsoft Windows [Version 10.0.19043.2130]
• Python: 3.7.8 (tags/v3.7.8:4b47a5b6ba, Jun 28 2020, 08:53:46) [MSC v.1916 64 bit (AMD64)] on win32
• SQLAlchemy: 2.0.0b3
• Database: N/A, but PostgreSQL 14
• DBAPI (eg: psycopg, cx_oracle, mysqlclient): psycopg

Additional context

I prefer to have the logic inside the Base(DeclarativeBase) class, so the logic is applied conditionally to all mapped tables without needing a Mixin for this specific functionality.

[zzzeek]

sure but that’s not correct. there’s any number of functions one could invoke that accept a class as its argument which would all have this problem.

[caffeinatedMike]

True, I see what you mean. I know it’s not a concrete solution, but in the case of has_inherited_table it seems to be resolved by updating the the signature to def has_inherited_table(cls: Type[Union[_O, _OO]]) -> bool:.