--python-version 3.9 should warn about generic usages #10971

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1. rr-

   added

   feature

   on Aug 11, 2021
2. rr- commented on Aug 11, 2021

   

   rr-

   on Aug 11, 2021

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   Here's an initial patch that adds such warnings and breaks half of the Python ecosystem

   diff --git a/mypy/checker.py b/mypy/checker.py
   index ba020f5d9..37063f9e2 100644
   --- a/mypy/checker.py
   +++ b/mypy/checker.py
   @@ -1958,6 +1958,52 @@ class TypeChecker(NodeVisitor[None], CheckerPluginInterface):
        def visit_import_from(self, node: ImportFrom) -> None:
            self.check_import(node)
    
   +        if (self.options.python_version[0] > 3 or self.options.python_version[0] == 3 and self.options.python_version[1] >= 9) and node.id == 'typing':
   +            deprecated_imports = {
   +                'Tuple': 'builtins.tuple',
   +                'Callable': 'collections.abc.Callable',
   +                'Type': 'builtins.type',
   +                'Dict': 'builtins.dict',
   +                'List': 'builtins.list',
   +                'Set': 'builtins.set',
   +                'FrozenSet': 'builtins.frozenset',
   +                'DefaultDict': 'collections.defaultdict',
   +                'OrderedDict': 'collections.OrderedDict',
   +                'ChainMap': 'collections.ChainMap',
   +                'Counter': 'collections.Counter',
   +                'Deque': 'collections.Deque',
   +                'Pattern': 're.Pattern',
   +                'Match': 're.Match',
   +                'AbstractSet': 'collections.abc.Set',
   +                'ByteString': 'collections.abc.ByteString',
   +                'Collection': 'collections.abc.Collection',
   +                'Container': 'collections.abc.Container',
   +                'ItemsView': 'collections.abc.ItemsView',
   +                'KeysView': 'collections.abc.KeysView',
   +                'Mapping': 'collections.abc.Mapping',
   +                'MappingView': 'collections.abc.MappingView',
   +                'MutableMapping': 'collections.abc.MutableMapping',
   +                'MutableSequence': 'collections.abc.MutableSequence',
   +                'MutableSet': 'collections.abc.MutableSet',
   +                'Sequence': 'collections.abc.Sequence',
   +                'ValuesView': 'collections.abc.ValuesView',
   +                'Iterable': 'collections.abc.Iterable',
   +                'Iterator': 'collections.abc.Iterator',
   +                'Generator': 'collections.abc.Generator',
   +                'Reversible': 'collections.abc.Reversible',
   +                'Coroutine': 'collections.abc.Coroutine',
   +                'AsyncGenerator': 'collections.abc.AsyncGenerator',
   +                'AsyncIterable': 'collections.abc.AsyncIterable',
   +                'AsyncIterator': 'collections.abc.AsyncIterator',
   +                'Awaitable': 'collections.abc.Awaitable',
   +                'ContextManager': 'collections.abc.AbstractContextManager',
   +                'AsyncContextManager': 'collections.abc.AbstractAsyncContextManager',
   +            }
   +            imported_names = [name[0] for name in node.names]
   +            for source, target in deprecated_imports.items():
   +                if source in imported_names:
   +                    self.fail(message_registry.TYPE_DEPRECATED_IN_FAVOR_OF_PY39.format(node.id + "." + source, target), node)
   +
        def visit_import_all(self, node: ImportAll) -> None:
            self.check_import(node)
    
   diff --git a/mypy/message_registry.py b/mypy/message_registry.py
   index 48b53336f..648e5a16e 100644
   --- a/mypy/message_registry.py
   +++ b/mypy/message_registry.py
   @@ -73,6 +73,7 @@ RETURN_TYPE_CANNOT_BE_CONTRAVARIANT: Final = (
    FUNCTION_PARAMETER_CANNOT_BE_COVARIANT: Final = (
        "Cannot use a covariant type variable as a parameter"
    )
   +TYPE_DEPRECATED_IN_FAVOR_OF_PY39: Final = "Type {} deprecated in favor of {} since Python 3.9"
    INCOMPATIBLE_IMPORT_OF: Final = "Incompatible import of"
    FUNCTION_TYPE_EXPECTED: Final = "Function is missing a type annotation"
    ONLY_CLASS_APPLICATION: Final = "Type application is only supported for generic classes"
   diff --git a/mypyc/test-data/run-imports.test b/mypyc/test-data/run-imports.test
   index 0957d1b2b..bf848d3e9 100644
   --- a/mypyc/test-data/run-imports.test
   +++ b/mypyc/test-data/run-imports.test
   @@ -192,3 +192,9 @@ a.x = 10
    x = 20
    [file driver.py]
    import native
   +
   +[case testPy39TypingImportDeprecationWarnings]
   +# flags: --python-version 3.9
   +from typing import Iterable
   +[out]
   +testPy39TypingImportDeprecationWarnings.py:1: note: Type typing.Iterable deprecated in favor of collections.abc.Iterable since Python 3.9
3. rr-

   added a commit that references this issue on Aug 14, 2021

   use collections.abc over typing

   ...

   b9c07d4
4. Avasam commented on May 18, 2026

   

   Avasam

   on May 18, 2026

   Last edited by Avasam

   SponsorContributor

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   FYI mypy 2.0 has dropped support for Python 3.9, so this shouldn't need 3.9-specific special casing:

   • Drop support for --python-version 3.9 #21243
   • https://mypy-lang.blogspot.com/2026/05/mypy-20-relased.html#:~:text=Drop%20Support%20for%20Targeting%20Python%203.9
5. JelleZijlstra commented on May 18, 2026

   

   JelleZijlstra

   on May 18, 2026

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   This is also relevant to newer versions, right?

   Though in practice, linters (e.g. Ruff, pyupgrade) warn about this instead, so there isn't a strong need for mypy to do it too.
6. Avasam commented on May 18, 2026

   

   Avasam

   on May 18, 2026

   Last edited by Avasam

   SponsorContributor

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   For class and function symbols typeshed can add deprecated decorators (even if not decorated as such at runtime) added in Python 3.13 (but backportable for static typing)
   and mypy has https://mypy.readthedocs.io/en/stable/error_code_list2.html#check-that-imported-or-used-feature-is-deprecated-deprecated

   So yeah, I don't think there's any special casing needed from mypy anymore.
7. JelleZijlstra commented on May 18, 2026

   

   JelleZijlstra

   on May 18, 2026

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   We can't add deprecated decorators for things like typing.List in typeshed though.

   👍React with 👍1Reacted by Avasam