Properly account for member and nonmember in TypeInfo.enum_members (#18559)

Closes #18557

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: sobolevn

mypy/nodes.py

@@ -3247,10 +3247,26 @@ def enum_members(self) -> list[str]:
             name
             for name, sym in self.names.items()
             if (
-                isinstance(sym.node, Var)
-                and name not in EXCLUDED_ENUM_ATTRIBUTES
-                and not name.startswith("__")
-                and sym.node.has_explicit_value
+                (
+                    isinstance(sym.node, Var)
+                    and name not in EXCLUDED_ENUM_ATTRIBUTES
+                    and not name.startswith("__")
+                    and sym.node.has_explicit_value
+                    and not (
+                        isinstance(
+                            typ := mypy.types.get_proper_type(sym.node.type), mypy.types.Instance
+                        )
+                        and typ.type.fullname == "enum.nonmember"
+                    )
+                )
+                or (
+                    isinstance(sym.node, Decorator)
+                    and any(
+                        dec.fullname == "enum.member"
+                        for dec in sym.node.decorators
+                        if isinstance(dec, RefExpr)
+                    )
+                )
             )
         ]
 

mypy/typeops.py

@@ -955,7 +955,7 @@ class Status(Enum):
             FAILURE = 2
             UNKNOWN = 3
 
-    ...and if we call `try_expanding_enum_to_union(Union[Color, Status], 'module.Color')`,
+    ...and if we call `try_expanding_sum_type_to_union(Union[Color, Status], 'module.Color')`,
     this function will return Literal[Color.RED, Color.BLUE, Color.YELLOW, Status].
     """
     typ = get_proper_type(typ)

test-data/unit/check-enum.test

@@ -1933,6 +1933,18 @@ class D(C):  # E: Cannot extend enum with existing members: "C" \
     x: int   # E: Cannot assign to final name "x"
 [builtins fixtures/bool.pyi]
 
+[case testEnumNotFinalWithMethodsAndUninitializedValuesStubMember]
+# flags: --python-version 3.11
+# This was added in 3.11
+import lib
+
+[file lib.pyi]
+from enum import Enum, member
+class A(Enum):
+    @member
+    def x(self) -> None: ...
+[builtins fixtures/bool.pyi]
+
 [case testEnumLiteralValues]
 from enum import Enum
 
@@ -2325,6 +2337,28 @@ def some_a(a: A):
 [builtins fixtures/dict.pyi]
 
 
+[case testEnumMemberAndNonMemberSupport]
+# flags: --python-version 3.11 --warn-unreachable
+# This was added in 3.11
+from enum import Enum, member, nonmember
+
+class A(Enum):
+    x = 1
+    y = member(2)
+    z = nonmember(3)
+
+def some_a(a: A):
+    if a is not A.x and a is not A.z:
+        reveal_type(a)  # N: Revealed type is "Literal[__main__.A.y]"
+    if a is not A.y and a is not A.z:
+        reveal_type(a)  # N: Revealed type is "Literal[__main__.A.x]"
+    if a is not A.x:
+        reveal_type(a)  # N: Revealed type is "Literal[__main__.A.y]"
+    if a is not A.y:
+        reveal_type(a)  # N: Revealed type is "Literal[__main__.A.x]"
+[builtins fixtures/dict.pyi]
+
+
 [case testErrorOnAnnotatedMember]
 from enum import Enum