Add generic alias test cases

[cdce8p]

Steps

• Add yourself to CONTRIBUTORS if you are a new contributor.
• Add a ChangeLog entry describing what your PR does.
• If it's a new feature or an important bug fix, add a What's New entry in doc/whatsnew/<current release.rst>.
• Write a good description on what the PR does.

Description

Add new test cases for generic_alias to make validating any updates a bit easier.
At the moment, some errors are still undetected that should be recognized.

Related
#4206
pylint-dev/astroid#921

Type of Changes

	Type
✓	🐛 Bug fix
✓	✨ New feature

[cdce8p]

These are the current non-detected errors, no false positives.

pytest tests/test_functional.py -k generic_alias

Python 3.8

test_functional[generic_alias_typing]
E       Expected in testdata:
E         66: unsubscriptable-object  # typing.ByteString[int]
E         67: unsubscriptable-object  # typing.Hashable[int]
E         68: unsubscriptable-object  # typing.Sized[int]
E        125: unsubscriptable-object  # var_bytestring2: typing.ByteString[int]
E        126: unsubscriptable-object  # var_hashable2: typing.Hashable[int]
E        127: unsubscriptable-object  # var_sized2: typing.Sized[int]

test_functional[generic_alias_postponed_evaluation_py37]
E       Expected in testdata:
E         67: unsubscriptable-object  # re.Pattern[str]
E         68: unsubscriptable-object  # re.Match[str]
E         85: abstract-method  # Derived -> Iterable
E         88: abstract-method  # Derived -> Collection
E        112: abstract-method  # Derived -> Sized, Iterable
E        114: abstract-method  # Derived -> Multiple

test_functional[generic_alias_collections_py37]
E       Expected in testdata:
E         62: unsubscriptable-object  # re.Pattern[str]
E         63: unsubscriptable-object  # re.Match[str]
E         80: abstract-method  # Derived -> Iterable
E         83: abstract-method  # Derived -> Collection
E        107: abstract-method  # Derived -> Sized, Iterable
E        109: abstract-method  # Derived -> Multiple
E        122: unsubscriptable-object  # var_pattern: re.Pattern[int]

Python 3.9

test_functional[generic_alias_typing]
E       Expected in testdata:
E         66: unsubscriptable-object  # typing.ByteString[int]
E         67: unsubscriptable-object  # typing.Hashable[int]
E         68: unsubscriptable-object  # typing.Sized[int]
E        125: unsubscriptable-object  # var_bytestring2: typing.ByteString[int]
E        126: unsubscriptable-object  # var_hashable2: typing.Hashable[int]
E        127: unsubscriptable-object  # var_sized2: typing.Sized[int]

test_functional[generic_alias_collections]
E       Expected in testdata:
E         77: abstract-method  # Derived -> Iterable
E         80: abstract-method  # Derived -> Collection
E        104: abstract-method  # Derived -> Sized, Iterable
E        106: abstract-method  # Derived -> Multiple

[Pierre-Sassoulas]

Very nice ! We clearly lacked tests for python 3.9.

[cdce8p]

It isn't as bad as it might seem! TBH it's a small miracle that there aren't more.

I frequently get confused what works in which version and in what setting (assignment, type annotation, with or without postponed evaluation). These tests should help with that and make it at least a bit easier. Always assuming that there isn't a bug in there as well 😅

This was one of the reasons I started working on the pylint support. If pylint is able to detect the errors, it should help a lot of devs who use typing, especially until 3.10 is the default.

[hippo91]

@cdce8p very nice job! It is a great help for setting up astroid's typing and collection brain!

[coveralls]

Coverage remained the same at 91.594% when pulling f7e6850 on cdce8p:generic-alias into 078ebea on PyCQA:master.

[cdce8p]

All tests pass, finally!
pytest -m acceptance -k "test_libmodule[typing.py]" works as well.

[Pierre-Sassoulas]

This is VERY satisfying. Wow 😄

[cdce8p]

🎉 🥳

[hippo91]

Very nice job @cdce8p ! Congrats!