Fix enum attributes are not members (#17207)

This adds on to the change in #17182
and fixes enum attributes being used as members.

Fixes: #16730

---------

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Ali Hamdan <ali.hamdan.dev@gmail.com>
Co-authored-by: hauntsaninja <hauntsaninja@gmail.com>

mypy/semanal.py

@@ -4311,6 +4311,13 @@ def analyze_name_lvalue(
                     lvalue,
                 )
 
+            if explicit_type and has_explicit_value:
+                self.fail("Enum members must be left unannotated", lvalue)
+                self.note(
+                    "See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members",
+                    lvalue,
+                )
+
         if (not existing or isinstance(existing.node, PlaceholderNode)) and not outer:
             # Define new variable.
             var = self.make_name_lvalue_var(

mypy/semanal_enum.py

@@ -143,6 +143,12 @@ def build_enum_call_typeinfo(
             var = Var(item)
             var.info = info
             var.is_property = True
+            # When an enum is created by its functional form `Enum(name, values)`
+            # - if it is a string it is first split by commas/whitespace
+            # - if it is an iterable of single items each item is assigned a value starting at `start`
+            # - if it is an iterable of (name, value) then the given values will be used
+            # either way, each item should be treated as if it has an explicit value.
+            var.has_explicit_value = True
             var._fullname = f"{info.fullname}.{item}"
             info.names[item] = SymbolTableNode(MDEF, var)
         return info

mypy/typeops.py

@@ -31,7 +31,6 @@
 )
 from mypy.state import state
 from mypy.types import (
-    ENUM_REMOVED_PROPS,
     AnyType,
     CallableType,
     ExtraAttrs,
@@ -958,27 +957,16 @@ class Status(Enum):
         items = [
             try_expanding_sum_type_to_union(item, target_fullname) for item in typ.relevant_items()
         ]
-        return make_simplified_union(items, contract_literals=False)
     elif isinstance(typ, Instance) and typ.type.fullname == target_fullname:
         if typ.type.is_enum:
-            new_items = []
-            for name, symbol in typ.type.names.items():
-                if not isinstance(symbol.node, Var):
-                    continue
-                # Skip these since Enum will remove it
-                if name in ENUM_REMOVED_PROPS:
-                    continue
-                # Skip private attributes
-                if name.startswith("__"):
-                    continue
-                new_items.append(LiteralType(name, typ))
-            return make_simplified_union(new_items, contract_literals=False)
+            items = [LiteralType(name, typ) for name in typ.get_enum_values()]
         elif typ.type.fullname == "builtins.bool":
-            return make_simplified_union(
-                [LiteralType(True, typ), LiteralType(False, typ)], contract_literals=False
-            )
+            items = [LiteralType(True, typ), LiteralType(False, typ)]
+    else:
+        return typ
 
-    return typ
+    # if the expanded union would be `Never` leave the type as is
+    return typ if not items else make_simplified_union(items, contract_literals=False)
 
 
 def try_contracting_literals_in_union(types: Sequence[Type]) -> list[ProperType]:

mypy/types.py

@@ -1566,7 +1566,14 @@ def is_singleton_type(self) -> bool:
     def get_enum_values(self) -> list[str]:
         """Return the list of values for an Enum."""
         return [
-            name for name, sym in self.type.names.items() if isinstance(sym.node, mypy.nodes.Var)
+            name
+            for name, sym in self.type.names.items()
+            if (
+                isinstance(sym.node, mypy.nodes.Var)
+                and name not in ENUM_REMOVED_PROPS
+                and not name.startswith("__")
+                and sym.node.has_explicit_value
+            )
         ]
 
 

mypyc/test-data/run-classes.test

@@ -270,8 +270,8 @@ from enum import Enum
 
 class TestEnum(Enum):
     _order_ = "a b"
-    a : int = 1
-    b : int = 2
+    a = 1
+    b = 2
 
     @classmethod
     def test(cls) -> int:

test-data/unit/check-enum.test

@@ -1764,7 +1764,8 @@ class B(A):
     x = 1  # E: Cannot override writable attribute "x" with a final one
 
 class A1(Enum):
-    x: int = 1
+    x: int = 1  # E: Enum members must be left unannotated \
+                # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members
 class B1(A1):  # E: Cannot extend enum with existing members: "A1"
     pass
 
@@ -1779,6 +1780,7 @@ class A3(Enum):
     x: Final[int]  # type: ignore
 class B3(A3):
     x = 1  # E: Cannot override final attribute "x" (previously declared in base class "A3")
+
 [builtins fixtures/bool.pyi]
 
 [case testEnumNotFinalWithMethodsAndUninitializedValuesStub]
@@ -2185,3 +2187,67 @@ reveal_type(A.y.value)  # N: Revealed type is "Literal[2]?"
 def some_a(a: A):
     reveal_type(a.value)  # N: Revealed type is "Union[Literal[1]?, Literal[2]?]"
 [builtins fixtures/dict.pyi]
+
+
+[case testErrorOnAnnotatedMember]
+from enum import Enum
+
+class Medal(Enum):
+    gold: int = 1  # E: Enum members must be left unannotated \
+                   # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members
+    silver: str = 2  # E: Enum members must be left unannotated \
+                     # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members \
+                     # E: Incompatible types in assignment (expression has type "int", variable has type "str")
+    bronze = 3
+
+[case testEnumMemberWithPlaceholder]
+from enum import Enum
+
+class Pet(Enum):
+    CAT = ...
+    DOG: str = ...  # E: Enum members must be left unannotated \
+                    # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members \
+                    # E: Incompatible types in assignment (expression has type "ellipsis", variable has type "str")
+
+[case testEnumValueWithPlaceholderNodeType]
+# https://github.com/python/mypy/issues/11971
+from enum import Enum
+from typing import Any, Callable, Dict
+class Foo(Enum):
+    Bar: Foo = Callable[[str], None]  # E: Enum members must be left unannotated \
+                                      # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members \
+                                      # E: Incompatible types in assignment (expression has type "<typing special form>", variable has type "Foo")
+    Baz: Any = Callable[[Dict[str, "Missing"]], None]  # E: Enum members must be left unannotated \
+                                                       # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members \
+                                                       # E: Type application targets a non-generic function or class \
+                                                       # E: Name "Missing" is not defined
+
+reveal_type(Foo.Bar)  # N: Revealed type is "Literal[__main__.Foo.Bar]?"
+reveal_type(Foo.Bar.value)  # N: Revealed type is "__main__.Foo"
+reveal_type(Foo.Baz)  # N: Revealed type is "Literal[__main__.Foo.Baz]?"
+reveal_type(Foo.Baz.value)  # N: Revealed type is "Any"
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-full.pyi]
+
+
+[case testEnumWithOnlyImplicitMembersUsingAnnotationOnly]
+# flags: --warn-unreachable
+import enum
+
+
+class E(enum.IntEnum):
+    A: int
+    B: int
+
+
+def do_check(value: E) -> None:
+    reveal_type(value)  # N: Revealed type is "__main__.E"
+    # this is a nonmember check, not an emum member check, and it should not narrow the value
+    if value is E.A:
+        return
+
+    reveal_type(value)  # N: Revealed type is "__main__.E"
+    "should be reachable"
+
+[builtins fixtures/primitives.pyi]
+[typing fixtures/typing-full.pyi]

test-data/unit/check-python310.test

@@ -1525,6 +1525,60 @@ def g(m: Medal) -> int:
             reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.bronze]"
             return 2
 
+
+[case testMatchLiteralPatternEnumWithTypedAttribute]
+from enum import Enum
+from typing import NoReturn
+def assert_never(x: NoReturn) -> None: ...
+
+class int:
+    def __new__(cls, value: int): pass
+
+class Medal(int, Enum):
+    prize: str
+
+    def __new__(cls, value: int, prize: str) -> Medal:
+        enum = int.__new__(cls, value)
+        enum._value_ = value
+        enum.prize = prize
+        return enum
+
+    gold = (1, 'cash prize')
+    silver = (2, 'sponsorship')
+    bronze = (3, 'nothing')
+
+m: Medal
+
+match m:
+    case Medal.gold:
+        reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.gold]"
+    case Medal.silver:
+        reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.silver]"
+    case Medal.bronze:
+        reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.bronze]"
+    case _ as unreachable:
+        assert_never(unreachable)
+
+[builtins fixtures/tuple.pyi]
+
+[case testMatchLiteralPatternFunctionalEnum]
+from enum import Enum
+from typing import NoReturn
+def assert_never(x: NoReturn) -> None: ...
+
+Medal = Enum('Medal', 'gold silver bronze')
+m: Medal
+
+match m:
+    case Medal.gold:
+        reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.gold]"
+    case Medal.silver:
+        reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.silver]"
+    case Medal.bronze:
+        reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.bronze]"
+    case _ as unreachable:
+        assert_never(unreachable)
+
 [case testMatchLiteralPatternEnumCustomEquals-skip]
 from enum import Enum
 class Medal(Enum):

test-data/unit/pythoneval.test

@@ -1555,18 +1555,6 @@ if isinstance(obj, Awaitable):
 _testSpecialTypingProtocols.py:6: note: Revealed type is "Tuple[builtins.int]"
 _testSpecialTypingProtocols.py:8: error: Statement is unreachable
 
-[case testEnumValueWithPlaceholderNodeType]
-# https://github.com/python/mypy/issues/11971
-from enum import Enum
-from typing import Callable, Dict
-class Foo(Enum):
-    Bar: Foo = Callable[[str], None]
-    Baz: Foo = Callable[[Dict[str, "Missing"]], None]
-[out]
-_testEnumValueWithPlaceholderNodeType.py:5: error: Incompatible types in assignment (expression has type "<typing special form>", variable has type "Foo")
-_testEnumValueWithPlaceholderNodeType.py:6: error: Incompatible types in assignment (expression has type "<typing special form>", variable has type "Foo")
-_testEnumValueWithPlaceholderNodeType.py:6: error: Name "Missing" is not defined
-
 [case testTypeshedRecursiveTypesExample]
 from typing import List, Union