Added diagnostic check for an enum member with a type annotation. The typing spec says that this should be considered a typing error. This addresses #8060. (#8069)

Author: erictraut

packages/pyright-internal/src/analyzer/checker.ts

@@ -4971,12 +4971,17 @@ export class Checker extends ParseTreeWalker {
         }
 
         ClassType.getSymbolTable(classType).forEach((symbol, name) => {
-            // Enum members don't have type annotations.
-            if (symbol.getTypedDeclarations().length > 0) {
-                return;
-            }
-
-            const symbolType = transformTypeForEnumMember(this._evaluator, classType, name);
+            // Determine whether this is an enum member. We ignore the presence
+            // of an annotation in this case because the runtime does. From a
+            // type checking perspective, if the runtime treats the assignment
+            // as an enum member but there is a type annotation present, it is
+            // considered a type checking error.
+            const symbolType = transformTypeForEnumMember(
+                this._evaluator,
+                classType,
+                name,
+                /* ignoreAnnotation */ true
+            );
 
             // Is this symbol a literal instance of the enum class?
             if (
@@ -4988,6 +4993,19 @@ export class Checker extends ParseTreeWalker {
                 return;
             }
 
+            // Enum members should not have type annotations.
+            const typedDecls = symbol.getTypedDeclarations();
+            if (typedDecls.length > 0) {
+                if (typedDecls[0].type === DeclarationType.Variable && typedDecls[0].inferredTypeSource) {
+                    this._evaluator.addDiagnostic(
+                        DiagnosticRule.reportGeneralTypeIssues,
+                        LocMessage.enumMemberTypeAnnotation(),
+                        typedDecls[0].node
+                    );
+                }
+                return;
+            }
+
             // Look for a duplicate assignment.
             const decls = symbol.getDeclarations();
             if (decls.length >= 2 && decls[0].type === DeclarationType.Variable) {

packages/pyright-internal/src/analyzer/enums.ts

@@ -283,10 +283,19 @@ export function createEnumType(
     return classType;
 }
 
+// Performs the "magic" that the Enum metaclass does at runtime when it
+// transforms a value into an enum instance. If the specified name isn't
+// an enum member, this function returns undefined indicating that the
+// Enum metaclass does not transform the value.
+// By default, if a type annotation is present, the member is not treated
+// as a member of the enumeration, but the Enum metaclass ignores such
+// annotations. The typing spec indicates that the use of an annotation is
+// illegal, so we need to detect this case and report an error.
 export function transformTypeForEnumMember(
     evaluator: TypeEvaluator,
     classType: ClassType,
     memberName: string,
+    ignoreAnnotation = false,
     recursionCount = 0
 ): Type | undefined {
     if (recursionCount > maxTypeRecursionCount) {
@@ -335,16 +344,24 @@ export function transformTypeForEnumMember(
         isMemberOfEnumeration = true;
         isUnpackedTuple = true;
         valueTypeExprNode = nameNode.parent.parent.rightExpression;
+    } else if (
+        nameNode.parent?.nodeType === ParseNodeType.TypeAnnotation &&
+        nameNode.parent.valueExpression === nameNode
+    ) {
+        if (ignoreAnnotation) {
+            isMemberOfEnumeration = true;
+        }
+        declaredTypeNode = nameNode.parent.typeAnnotation;
     }
 
     // The spec specifically excludes names that start and end with a single underscore.
     // This also includes dunder names.
-    if (isSingleDunderName(nameNode.value)) {
+    if (isSingleDunderName(memberName)) {
         return undefined;
     }
 
     // Specifically exclude "value" and "name". These are reserved by the enum metaclass.
-    if (nameNode.value === 'name' || nameNode.value === 'value') {
+    if (memberName === 'name' || memberName === 'value') {
         return undefined;
     }
 
@@ -362,6 +379,7 @@ export function transformTypeForEnumMember(
             evaluator,
             classType,
             valueTypeExprNode.value,
+            /* ignoreAnnotation */ false,
             recursionCount
         );
 
@@ -402,7 +420,7 @@ export function transformTypeForEnumMember(
     }
 
     // The spec excludes private (mangled) names.
-    if (isPrivateName(nameNode.value)) {
+    if (isPrivateName(memberName)) {
         return undefined;
     }
 
@@ -457,7 +475,7 @@ export function transformTypeForEnumMember(
     const enumLiteral = new EnumLiteral(
         memberInfo.classType.details.fullName,
         memberInfo.classType.details.name,
-        nameNode.value,
+        memberName,
         valueType
     );
 

packages/pyright-internal/src/localization/localize.ts

@@ -436,6 +436,7 @@ export namespace Localizer {
             new ParameterizedString<{ name: string }>(getRawString('Diagnostic.enumMemberDelete'));
         export const enumMemberSet = () =>
             new ParameterizedString<{ name: string }>(getRawString('Diagnostic.enumMemberSet'));
+        export const enumMemberTypeAnnotation = () => getRawString('Diagnostic.enumMemberTypeAnnotation');
         export const exceptionGroupIncompatible = () => getRawString('Diagnostic.exceptionGroupIncompatible');
         export const exceptionTypeIncorrect = () =>
             new ParameterizedString<{ type: string }>(getRawString('Diagnostic.exceptionTypeIncorrect'));

packages/pyright-internal/src/localization/package.nls.en-us.json

@@ -142,6 +142,7 @@
         "enumClassOverride": "Enum class \"{name}\" is final and cannot be subclassed",
         "enumMemberDelete": "Enum member \"{name}\" cannot be deleted",
         "enumMemberSet": "Enum member \"{name}\" cannot be assigned",
+        "enumMemberTypeAnnotation": "Type annotations are not allowed for enum members",
         "exceptionGroupIncompatible": "Exception group syntax (\"except*\") requires Python 3.11 or newer",
         "exceptionTypeIncorrect": "\"{type}\" does not derive from BaseException",
         "exceptionTypeNotClass": "\"{type}\" is not a valid exception class",

packages/pyright-internal/src/tests/samples/enum12.py

@@ -0,0 +1,15 @@
+# This sample tests that any attribute that is treated as a member at
+# runtime does not have a type annotation. The typing spec indicates that
+# type checkers should flag such conditions as errors.
+
+from enum import Enum
+from typing import Callable
+
+
+class Enum1(Enum):
+    # This should generate an error.
+    MEMBER: int = 1
+
+    _NON_MEMBER_: int = 3
+
+    NON_MEMBER_CALLABLE: Callable[[], int] = lambda: 1

packages/pyright-internal/src/tests/typeEvaluator3.test.ts

@@ -998,6 +998,12 @@ test('Enum11', () => {
     TestUtils.validateResults(analysisResults, 8);
 });
 
+test('Enum12', () => {
+    const analysisResults = TestUtils.typeAnalyzeSampleFiles(['enum12.py']);
+
+    TestUtils.validateResults(analysisResults, 1);
+});
+
 test('EnumAuto1', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['enumAuto1.py']);