Version 0.780 does not recognize python internal types as `typing.Type` anymore

[na-kialo]

Since upgrading from version 0.770 to 0.780 we saw issues, where types used during runtime were recognized as object and not as typing.Type anymore.

• Are you reporting a bug, or opening a feature request?
  Bug

• Please insert below the code you are checking with mypy

# test.py
from typing import Type, Union

def method(type: Type) -> None:
    pass

method(int)
method(Union[int, str])

• What is the actual behavior/output?

> mypy test.py # mypy==0.780
test.py:8: error: Argument 1 to "method" has incompatible type "object"; expected "Type[Any]"
Found 1 error in 1 file (checked 1 source file)

• What is the behavior/output you expect?

> mypy test.py # mypy==0.770
Success: no issues found in 1 source file

• What are the versions of mypy and Python you are using?
  Do you see the same issue after installing mypy from Git master?
  • Python version 3.8.2
  • failing mypy versions: 0.780 + latest master
  • passing mypy version: 0.770

[ilevkivskyi]

This is intended, at runtime Union[int, str] is not a subclass of type (on most newer version of Python anymore).

[aachurin]

But the documentation says the following:

The only legal parameters for Type are classes, Any, type variables, and unions of any of these types. For example:

def new_non_team_user(user_class: Type[Union[BaseUser, ProUser]]): ...

Type[Any] is equivalent to Type which in turn is equivalent to type, which is the root of Python’s metaclass hierarchy.

[hmvp]

The same happens with Optional[str] etc.. If Type is not the correct type to use, what should be used instead? How should I annotate mapping in this example?:

mapping: Dict[str, ?] = {
    "foo": str,
    "bar": Optional[str],
    "baz": SomeClass,

[JukkaL]

@hmvp You need to use object or Any.

[hmvp]

@JukkaL That's not really satisfying isn't it? I would like to use something that expresses that the values in the mapping are type-like, not instances. Using Any or object is basically saying "I don't care about the type". I want mypy to warn that any of the following entries are not allowed:

mapping: Dict[str, ?] = {
    "foo": "some string",
    "baz": SomeClass(),
}