Augment. Report INVALID_OVERRIDE using merged interfaces.

Change-Id: Id515aaf813b60ccbfc3d5fece1b728f1e909a261
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/373762
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/lib/src/error/inheritance_override.dart

@@ -196,10 +196,13 @@ class _ClassVerifier {
       return true;
     }
 
-    var classElement = this.classElement;
-    if (classElement is! EnumElement &&
-        classElement is ClassElement &&
-        !classElement.isAbstract &&
+    var fragment = classElement;
+    var augmented = fragment.augmented;
+    var declaration = augmented.declaration;
+
+    if (declaration is! EnumElement &&
+        declaration is ClassElement &&
+        !declaration.isAbstract &&
         implementsDartCoreEnum) {
       reporter.atToken(
         classNameToken,
@@ -208,23 +211,23 @@ class _ClassVerifier {
       return true;
     }
 
-    if (_checkForRecursiveInterfaceInheritance(classElement)) {
+    if (_checkForRecursiveInterfaceInheritance(declaration)) {
       return true;
     }
 
     // Compute the interface of the class.
-    var interface = inheritance.getInterface(classElement);
+    var interface = inheritance.getInterface(declaration);
 
     // Report conflicts between direct superinterfaces of the class.
     for (var conflict in interface.conflicts) {
       _reportInconsistentInheritance(classNameToken, conflict);
     }
 
-    if (classElement.supertype != null) {
-      directSuperInterfaces.add(classElement.supertype!);
+    if (declaration.supertype != null) {
+      directSuperInterfaces.add(declaration.supertype!);
     }
-    if (classElement is MixinElement) {
-      directSuperInterfaces.addAll(classElement.superclassConstraints);
+    if (augmented is AugmentedMixinElement) {
+      directSuperInterfaces.addAll(augmented.superclassConstraints);
     }
 
     // Each mixin in `class C extends S with M0, M1, M2 {}` is equivalent to:
@@ -235,14 +238,14 @@ class _ClassVerifier {
     // So, we need to check members of each mixin against superinterfaces
     // of `S`, and superinterfaces of all previous mixins.
     var mixinNodes = withClause?.mixinTypes;
-    var mixinTypes = classElement.mixins;
+    var mixinTypes = declaration.mixins;
     for (var i = 0; i < mixinTypes.length; i++) {
       var mixinType = mixinTypes[i];
       _checkDeclaredMembers(mixinNodes![i], mixinType, mixinIndex: i);
       directSuperInterfaces.add(mixinType);
     }
 
-    directSuperInterfaces.addAll(classElement.interfaces);
+    directSuperInterfaces.addAll(augmented.interfaces);
 
     // Check the members of the class itself, against all the previously
     // collected superinterfaces of the supertype, mixins, and interfaces.
@@ -253,7 +256,7 @@ class _ClassVerifier {
           var fieldElement = field.declaredElement as FieldElement;
           _checkDeclaredMember(field.name, libraryUri, fieldElement.getter);
           _checkDeclaredMember(field.name, libraryUri, fieldElement.setter);
-          if (!member.isStatic && classElement is! EnumElement) {
+          if (!member.isStatic && declaration is! EnumElement) {
             _checkIllegalEnumValuesDeclaration(field.name);
           }
           if (!member.isStatic) {
@@ -271,7 +274,7 @@ class _ClassVerifier {
         if (!(member.isStatic || member.isAbstract || member.isSetter)) {
           _checkIllegalConcreteEnumMemberDeclaration(member.name);
         }
-        if (!member.isStatic && classElement is! EnumElement) {
+        if (!member.isStatic && declaration is! EnumElement) {
           _checkIllegalEnumValuesDeclaration(member.name);
         }
       }
@@ -283,10 +286,10 @@ class _ClassVerifier {
     GetterSetterTypesVerifier(
       typeSystem: typeSystem,
       errorReporter: reporter,
-    ).checkInterface(classElement, interface);
+    ).checkInterface(declaration, interface);
 
-    if (classElement is ClassElement && !classElement.isAbstract ||
-        classElement is EnumElement) {
+    if (declaration is ClassElement && !declaration.isAbstract ||
+        declaration is EnumElement) {
       List<ExecutableElement>? inheritedAbstract;
 
       for (var name in interface.map.keys) {
@@ -302,11 +305,11 @@ class _ClassVerifier {
           if (_reportConcreteClassWithAbstractMember(name.name)) {
             continue;
           }
-          if (_isNotImplementedInConcreteSuperClass(classElement, name)) {
+          if (_isNotImplementedInConcreteSuperClass(declaration, name)) {
             continue;
           }
           // We already reported ILLEGAL_ENUM_VALUES_INHERITANCE.
-          if (classElement is EnumElement &&
+          if (declaration is EnumElement &&
               const {'values', 'values='}.contains(name.name)) {
             continue;
           }

pkg/analyzer/test/src/diagnostics/invalid_override_test.dart

@@ -602,6 +602,23 @@ class B implements A {
     ]);
   }
 
+  test_method_returnType_interface_fromAugmentation() async {
+    await assertErrorsInCode('''
+class A {
+  int foo() => 0;
+}
+
+class B {
+  String foo() => '';
+}
+
+augment class B implements A {}
+''', [
+      error(CompileTimeErrorCode.INVALID_OVERRIDE, 50, 3,
+          contextMessages: [message(testFile, 16, 3)]),
+    ]);
+  }
+
   test_method_returnType_interface_grandparent() async {
     await assertErrorsInCode('''
 abstract class A {
@@ -646,6 +663,23 @@ class B extends A {
     ]);
   }
 
+  test_method_returnType_superclass_fromAugmentation() async {
+    await assertErrorsInCode('''
+class A {
+  int foo() => 0;
+}
+
+class B {
+  String foo() => '';
+}
+
+augment class B extends A {}
+''', [
+      error(CompileTimeErrorCode.INVALID_OVERRIDE, 50, 3,
+          contextMessages: [message(testFile, 16, 3)]),
+    ]);
+  }
+
   test_method_returnType_superclass_grandparent() async {
     await assertErrorsInCode('''
 class A {
@@ -694,7 +728,7 @@ class B extends A {
     ]);
   }
 
-  test_mixin_field_type() async {
+  test_mixin_field_type_on() async {
     await assertErrorsInCode(r'''
 class A {
   String foo = '';
@@ -711,7 +745,7 @@ mixin M on A {
     ]);
   }
 
-  test_mixin_getter_type() async {
+  test_mixin_getter_type_on() async {
     await assertErrorsInCode(r'''
 class A {
   String get foo => '';
@@ -726,7 +760,7 @@ mixin M on A {
     ]);
   }
 
-  test_mixin_method_returnType() async {
+  test_mixin_method_returnType_on() async {
     await assertErrorsInCode(r'''
 class A {
   String foo() => '';
@@ -741,7 +775,24 @@ mixin M on A {
     ]);
   }
 
-  test_mixin_setter_type() async {
+  test_mixin_method_returnType_on_fromAugmentation() async {
+    await assertErrorsInCode(r'''
+class A {
+  int foo() => 0;
+}
+
+mixin M {
+  String foo() => '';
+}
+
+augment mixin M on A {}
+''', [
+      error(CompileTimeErrorCode.INVALID_OVERRIDE, 50, 3,
+          contextMessages: [message(testFile, 16, 3)]),
+    ]);
+  }
+
+  test_mixin_setter_type_on() async {
     await assertErrorsInCode(r'''
 class A {
   set foo(String _) {}