Makes classes compatible with mypy 1.2

[thepabloaguilar]

Makes classes compatible with mypy 1.2

Checklist

• I have double checked that there are no unrelated changes in this pull request (old patches, accidental config files, etc)
• I have created at least one test case for the changes I have made
• I have updated the documentation for the changes I have made
• I have added my changes to the CHANGELOG.md

[thepabloaguilar]

@sobolevn just need a little of your help here with the errors!

[sobolevn]

tests/test_typeclass/test_typed_dict.py:25: error: Invalid metaclass "_Meta" [misc]

This test needs some love.
https://github.com/dry-python/classes/blob/master/tests/test_typeclass/test_typed_dict.py#L9

Right now it is in a semi-broken state.

tests/test_typeclass/test_call.py:17: error: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases [misc]

Can be just ignored.
This is probably a mypy bug.
You can also report this to mypy.

tests/test_associated_type/test_variadic_generic.py:34: error: Function "Type[Example[Any]]" could always be true in boolean context [truthy-function]

Can be just ignored.

[codecov-commenter]

Codecov Report

Merging #487 (13d3f44) into master (4b0e9e5) will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@## master #487 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 2 3 +1 Lines 103 106 +3 Branches 18 17 -1 ========================================= + Hits 103 106 +3 

Impacted Files	Coverage Δ
classes/_typeclass.py	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[thepabloaguilar]

I need to dig more deep to see why this expected error is not being raised anymore:

main:29: error: Instance "TypedDict('main.Other',{'name': builtins.str, 'registered': builtins.bool})" does not match inferred type "main.UserDict" 

[zhukovgreen]

Updated #483 to have also mypy^1.2.0. Can you guys either cherry-pick it here or review after this one is merged

[sobolevn]

Sure!

[sobolevn]

You can do the same for returns

[zhukovgreen]

Added dry-python/returns#1605

[guitvcer]

I need to dig more deep to see why this expected error is not being raised anymore:

main:29: error: Instance "TypedDict('main.Other',{'name': builtins.str, 'registered': builtins.bool})" does not match inferred type "main.UserDict" 

Hello. How are things going? If you wish, I can try to fix it.

[sobolevn]

@guitvcer you are very welcome to create a PR with new mypy version :)
It is rather hard to do, but I can help!