Dedicated error code for explicit any (#18398)

Author: hauntsaninja

docs/source/error_code_list.rst

@@ -1241,6 +1241,22 @@ Consider this example:
 `PEP 705 <https://peps.python.org/pep-0705>`_ specifies
 how ``ReadOnly`` special form works for ``TypedDict`` objects.
 
+.. _code-narrowed-type-not-subtype:
+
+Check that ``TypeIs`` narrows types [narrowed-type-not-subtype]
+---------------------------------------------------------------
+
+:pep:`742` requires that when ``TypeIs`` is used, the narrowed
+type must be a subtype of the original type::
+
+    from typing_extensions import TypeIs
+
+    def f(x: int) -> TypeIs[str]:  # Error, str is not a subtype of int
+        ...
+
+    def g(x: object) -> TypeIs[str]:  # OK
+        ...
+
 .. _code-misc:
 
 Miscellaneous checks [misc]

docs/source/error_code_list2.rst

@@ -594,18 +594,19 @@ Correct usage:
 When this code is enabled, using ``reveal_locals`` is always an error,
 because there's no way one can import it.
 
-.. _code-narrowed-type-not-subtype:
 
-Check that ``TypeIs`` narrows types [narrowed-type-not-subtype]
----------------------------------------------------------------
+.. _code-explicit-any:
 
-:pep:`742` requires that when ``TypeIs`` is used, the narrowed
-type must be a subtype of the original type::
+Check that explicit Any type annotations are not allowed [explicit-any]
+-----------------------------------------------------------------------
 
-    from typing_extensions import TypeIs
+If you use :option:`--disallow-any-explicit <mypy --disallow-any-explicit>`, mypy generates an error
+if you use an explicit ``Any`` type annotation.
 
-    def f(x: int) -> TypeIs[str]:  # Error, str is not a subtype of int
-        ...
+Example:
 
-    def g(x: object) -> TypeIs[str]:  # OK
-        ...
+.. code-block:: python
+
+    # mypy: disallow-any-explicit
+    from typing import Any
+    x: Any = 1  # Error: Explicit "Any" type annotation  [explicit-any]

mypy/errorcodes.py

@@ -304,6 +304,10 @@ def __hash__(self) -> int:
     "General",
 )
 
+EXPLICIT_ANY: Final = ErrorCode(
+    "explicit-any", "Warn about explicit Any type annotations", "General"
+)
+
 DEPRECATED: Final = ErrorCode(
     "deprecated",
     "Warn when importing or using deprecated (overloaded) functions, methods or classes",

mypy/messages.py

@@ -1821,7 +1821,7 @@ def need_annotation_for_var(
         )
 
     def explicit_any(self, ctx: Context) -> None:
-        self.fail('Explicit "Any" is not allowed', ctx)
+        self.fail('Explicit "Any" is not allowed', ctx, code=codes.EXPLICIT_ANY)
 
     def unsupported_target_for_star_typeddict(self, typ: Type, ctx: Context) -> None:
         self.fail(

test-data/unit/check-flags.test

@@ -1829,120 +1829,120 @@ x: A  # E:4: Missing type parameters for generic type "A"
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitDefSignature]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 
 from typing import Any, List
 
-def f(x: Any) -> None:  # E: Explicit "Any" is not allowed
+def f(x: Any) -> None:  # E: Explicit "Any" is not allowed  [explicit-any]
     pass
 
-def g() -> Any:  # E: Explicit "Any" is not allowed
+def g() -> Any:  # E: Explicit "Any" is not allowed  [explicit-any]
     pass
 
-def h() -> List[Any]:  # E: Explicit "Any" is not allowed
+def h() -> List[Any]:  # E: Explicit "Any" is not allowed  [explicit-any]
     pass
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitVarDeclaration]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any
-v: Any = ''  # E: Explicit "Any" is not allowed
-w = ''  # type: Any  # E: Explicit "Any" is not allowed
+v: Any = ''  # E: Explicit "Any" is not allowed  [explicit-any]
+w = ''  # type: Any  # E: Explicit "Any" is not allowed  [explicit-any]
 class X:
-    y = ''  # type: Any  # E: Explicit "Any" is not allowed
+    y = ''  # type: Any  # E: Explicit "Any" is not allowed  [explicit-any]
 
 [case testDisallowAnyExplicitGenericVarDeclaration]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, List
-v: List[Any] = []  # E: Explicit "Any" is not allowed
+v: List[Any] = []  # E: Explicit "Any" is not allowed  [explicit-any]
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitInheritance]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, List
 
-class C(Any):  # E: Explicit "Any" is not allowed
+class C(Any):  # E: Explicit "Any" is not allowed  [explicit-any]
     pass
 
-class D(List[Any]):  # E: Explicit "Any" is not allowed
+class D(List[Any]):  # E: Explicit "Any" is not allowed  [explicit-any]
     pass
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitAlias]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, List
 
-X = Any  # E: Explicit "Any" is not allowed
-Y = List[Any]  # E: Explicit "Any" is not allowed
+X = Any  # E: Explicit "Any" is not allowed  [explicit-any]
+Y = List[Any]  # E: Explicit "Any" is not allowed  [explicit-any]
 
 def foo(x: X) -> Y:  # no error
     x.nonexistent()  # no error
     return x
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitGenericAlias]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, TypeVar, Tuple
 
 T = TypeVar('T')
 
-TupleAny = Tuple[Any, T]  # E: Explicit "Any" is not allowed
+TupleAny = Tuple[Any, T]  # E: Explicit "Any" is not allowed  [explicit-any]
 
 def foo(x: TupleAny[str]) -> None:  # no error
     pass
 
-def goo(x: TupleAny[Any]) -> None:  # E: Explicit "Any" is not allowed
+def goo(x: TupleAny[Any]) -> None:  # E: Explicit "Any" is not allowed  [explicit-any]
     pass
 [builtins fixtures/tuple.pyi]
 
 [case testDisallowAnyExplicitCast]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, List, cast
 
 x = 1
-y = cast(Any, x)  # E: Explicit "Any" is not allowed
-z = cast(List[Any], x)  # E: Explicit "Any" is not allowed
+y = cast(Any, x)  # E: Explicit "Any" is not allowed  [explicit-any]
+z = cast(List[Any], x)  # E: Explicit "Any" is not allowed  [explicit-any]
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitNamedTuple]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, List, NamedTuple
 
-Point = NamedTuple('Point', [('x', List[Any]), ('y', Any)])  # E: Explicit "Any" is not allowed
+Point = NamedTuple('Point', [('x', List[Any]), ('y', Any)])  # E: Explicit "Any" is not allowed  [explicit-any]
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitTypeVarConstraint]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, List, TypeVar
 
-T = TypeVar('T', Any, List[Any])  # E: Explicit "Any" is not allowed
+T = TypeVar('T', Any, List[Any])  # E: Explicit "Any" is not allowed  [explicit-any]
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitNewType]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from typing import Any, List, NewType
 
 # this error does not come from `--disallow-any-explicit` flag
-Baz = NewType('Baz', Any)  # E: Argument 2 to NewType(...) must be subclassable (got "Any")
-Bar = NewType('Bar', List[Any])  # E: Explicit "Any" is not allowed
+Baz = NewType('Baz', Any)  # E: Argument 2 to NewType(...) must be subclassable (got "Any")  [valid-newtype]
+Bar = NewType('Bar', List[Any])  # E: Explicit "Any" is not allowed  [explicit-any]
 [builtins fixtures/list.pyi]
 
 [case testDisallowAnyExplicitTypedDictSimple]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from mypy_extensions import TypedDict
 from typing import Any
 
-M = TypedDict('M', {'x': str, 'y': Any})  # E: Explicit "Any" is not allowed
+M = TypedDict('M', {'x': str, 'y': Any})  # E: Explicit "Any" is not allowed  [explicit-any]
 M(x='x', y=2)  # no error
 def f(m: M) -> None: pass  # no error
 [builtins fixtures/dict.pyi]
 
 [case testDisallowAnyExplicitTypedDictGeneric]
-# flags: --disallow-any-explicit
+# flags: --disallow-any-explicit --show-error-codes
 from mypy_extensions import TypedDict
 from typing import Any, List
 
-M = TypedDict('M', {'x': str, 'y': List[Any]})  # E: Explicit "Any" is not allowed
+M = TypedDict('M', {'x': str, 'y': List[Any]})  # E: Explicit "Any" is not allowed  [explicit-any]
 N = TypedDict('N', {'x': str, 'y': List})  # no error
 [builtins fixtures/dict.pyi]
 

test-data/unit/fixtures/typing-typeddict.pyi

@@ -47,8 +47,7 @@ class Iterator(Iterable[T_co], Protocol):
     def __next__(self) -> T_co: pass
 
 class Sequence(Iterable[T_co]):
-    # misc is for explicit Any.
-    def __getitem__(self, n: Any) -> T_co: pass # type: ignore[misc]
+    def __getitem__(self, n: Any) -> T_co: pass # type: ignore[explicit-any]
 
 class Mapping(Iterable[T], Generic[T, T_co], metaclass=ABCMeta):
     def keys(self) -> Iterable[T]: pass  # Approximate return type