Add strong mode error for mixins defining conflicting private names (issue 28809)

pkg/analyzer/lib/src/generated/error_verifier.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.generated.error_verifier;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 468 matching lines @@
           _checkForExtendsDeferredClass(extendsClause);
           _checkForImplementsDeferredClass(implementsClause);
           _checkForNonAbstractClassInheritsAbstractMember(node.name);
           _checkForInconsistentMethodInheritance();
           _checkForRecursiveInterfaceInheritance(_enclosingClass);
           _checkForConflictingGetterAndMethod();
           _checkForConflictingInstanceGetterAndSuperclassMember();
           _checkImplementsSuperClass(node);
           _checkImplementsFunctionWithoutCall(node);
           _checkForMixinHasNoConstructors(node);
+          if (_options.strongMode) {
+            _checkForMixinWithConflictingPrivateMember(node);
+          }
         }
       }
       visitClassDeclarationIncrementally(node);
       _checkForFinalNotInitializedInClass(node);
       _checkForDuplicateDefinitionInheritance();
       _checkForConflictingInstanceMethodSetter(node);
       _checkForBadFunctionUse(node);
       return super.visitClassDeclaration(node);
     } finally {
       _isInNativeClass = false;
@@ skipping 4393 matching lines @@
     if (!enableSuperMixins && mixinElement.hasReferenceToSuper) {
       _errorReporter.reportErrorForNode(
           CompileTimeErrorCode.MIXIN_REFERENCES_SUPER,
           mixinName,
           [mixinElement.name]);
     }
     return false;
   }
 
   /**
+   * Check for the declaration of a mixin from a library other than the current
+   * library that defines a private member that conflicts with a private name
+   * from the same library but from a superclass or a different mixin.
+   */
+  void _checkForMixinWithConflictingPrivateMember(ClassDeclaration node) {
+    WithClause withClause = node.withClause;
+    if (withClause == null) {
+      return;
+    }
+    DartType declaredSupertype = node.extendsClause?.superclass?.type;
+    if (declaredSupertype is! InterfaceType) {
+      return;
+    }
+    InterfaceType superclass = declaredSupertype;
+    Map<LibraryElement, Map<String, String>> mixedInNames =
+        <LibraryElement, Map<String, String>>{};
+
+    /**
+     * Report an error and return `true` if the given [name] is a private name
+     * (which is defined in the given [library]) and it conflicts with another
+     * definition of that name inherited from the superclass.
+     */
+    bool isConflictingName(
+        String name, LibraryElement library, TypeName typeName) {
+      if (Identifier.isPrivateName(name)) {
+        Map<String, String> names =
+            mixedInNames.putIfAbsent(library, () => <String, String>{});
+        if (names.containsKey(name)) {
+          _errorReporter.reportErrorForNode(
+              CompileTimeErrorCode.PRIVATE_COLLISION_IN_MIXIN_APPLICATION,
+              typeName,
+              [name, typeName.name.name, names[name]]);
+          return true;
+        }
+        names[name] = typeName.name.name;
+        ExecutableElement inheritedMember =
+            superclass.lookUpMethod(name, library) ??
+                superclass.lookUpGetter(name, library) ??
+                superclass.lookUpSetter(name, library);
+        if (inheritedMember != null) {
+          _errorReporter.reportErrorForNode(
+              CompileTimeErrorCode.PRIVATE_COLLISION_IN_MIXIN_APPLICATION,
+              typeName, [
+            name,
+            typeName.name.name,
+            inheritedMember.enclosingElement.name
+          ]);
+          return true;
+        }
+      }
+      return false;
+    }
+
+    for (TypeName mixinType in withClause.mixinTypes) {
+      DartType type = mixinType.type;
+      if (type is InterfaceType) {
+        LibraryElement library = type.element.library;
+        if (library != _currentLibrary) {
+          for (PropertyAccessorElement accessor in type.accessors) {
+            if (isConflictingName(accessor.name, library, mixinType)) {
+              return;
+            }
+          }
+          for (MethodElement method in type.methods) {
+            if (isConflictingName(method.name, library, mixinType)) {
+              return;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  /**
    * Verify that the given [constructor] has at most one 'super' initializer.
    *
    * See [CompileTimeErrorCode.MULTIPLE_SUPER_INITIALIZERS].
    */
   void _checkForMultipleSuperInitializers(ConstructorDeclaration constructor) {
     bool hasSuperInitializer = false;
     for (ConstructorInitializer initializer in constructor.initializers) {
       if (initializer is SuperConstructorInvocation) {
         if (hasSuperInitializer) {
           _errorReporter.reportErrorForNode(
@@ skipping 2178 matching lines @@
 class _InvocationCollector extends RecursiveAstVisitor {
   final List<String> superCalls = <String>[];
 
   @override
   visitMethodInvocation(MethodInvocation node) {
     if (node.target is SuperExpression) {
       superCalls.add(node.methodName.name);
     }
   }
 }