Test failures with Python 3.9

[kulikjak]

With current astroid (version 2.4.2) we are experiencing 4 test failures when running with Python 3.9.0. Sadly, I don't see into astroid, hence I couldn't find the root cause, but I am ready to help with debugging.

________________________ TypingBrain.test_namedtuple_few_args ________________________

self = <tests.unittest_brain.TypingBrain testMethod=test_namedtuple_few_args>

    def test_namedtuple_few_args(self):
        result = builder.extract_node(
            """
        from typing import NamedTuple
        NamedTuple("A")
        """
        )
        inferred = next(result.infer())
>       self.assertIsInstance(inferred, astroid.Instance)
E       AssertionError: Uninferable is not an instance of <class 'astroid.bases.Instance'>

tests/unittest_brain.py:1021: AssertionError
_______________________ TypingBrain.test_namedtuple_few_fields _______________________

self = <tests.unittest_brain.TypingBrain testMethod=test_namedtuple_few_fields>

    def test_namedtuple_few_fields(self):
        result = builder.extract_node(
            """
        from typing import NamedTuple
        NamedTuple("A", [("a",), ("b", str), ("c", bytes)])
        """
        )
        inferred = next(result.infer())
>       self.assertIsInstance(inferred, astroid.Instance)
E       AssertionError: Uninferable is not an instance of <class 'astroid.bases.Instance'>

tests/unittest_brain.py:1032: AssertionError
__________________ TypingBrain.test_namedtuple_inference_nonliteral __________________

self = <tests.unittest_brain.TypingBrain testMethod=test_namedtuple_inference_nonliteral>

    def test_namedtuple_inference_nonliteral(self):
        # Note: NamedTuples in mypy only work with literals.
        klass = builder.extract_node(
            """
        from typing import NamedTuple
    
        name = "X"
        fields = [("a", int), ("b", str), ("c", bytes)]
        NamedTuple(name, fields)
        """
        )
        inferred = next(klass.infer())
>       self.assertIsInstance(inferred, astroid.Instance)
E       AssertionError: Uninferable is not an instance of <class 'astroid.bases.Instance'>

tests/unittest_brain.py:988: AssertionError
________________ test_dataclasses_subscript_inference_recursion_error ________________

    @pytest.mark.skipif(sys.version_info < (3, 8), reason="Needs dataclasses available")
    def test_dataclasses_subscript_inference_recursion_error():
        code = """
        from dataclasses import dataclass, replace
    
        @dataclass
        class ProxyConfig:
            auth: str = "/auth"
    
    
        a = ProxyConfig("")
        test_dict = {"proxy" : {"auth" : "", "bla" : "f"}}
    
        foo = test_dict['proxy']
        replace(a, **test_dict['proxy']) # This fails
        """
        node = extract_node(code)
        # Reproduces only with safe_infer()
>       assert helpers.safe_infer(node) is None
E       assert Uninferable is None
E        +  where Uninferable = <function safe_infer at 0x7fca603b4040>(<Call l.13 at 0x7fca4e6fc1f0>)
E        +    where <function safe_infer at 0x7fca603b4040> = helpers.safe_infer

tests/unittest_inference.py:5691: AssertionError
====== 4 failed, 908 passed, 6 skipped, 14 xfailed, 1 xpassed in 35.69 seconds =======

[hippo91]

@kulikjak thanks for your report. Currently we do not support python 3.9 yet. But we should work on it ASAP.

[kulikjak]

With patches from recently merged #858 and #829, the test suite for Python 3.9 is green again. Thanks!