Implement DEP 34 (less restricted mixins) in analysis engine.

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 engine.resolver.error_verifier;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/src/generated/static_type_analyzer.dart';
@@ skipping 237 matching lines @@
   HashSet<String> _namesForReferenceToDeclaredVariableInInitializer =
       new HashSet<String>();
 
   /**
    * A list of types used by the [CompileTimeErrorCode.EXTENDS_DISALLOWED_CLASS]
    * and [CompileTimeErrorCode.IMPLEMENTS_DISALLOWED_CLASS] error codes.
    */
   List<InterfaceType> _DISALLOWED_TYPES_TO_EXTEND_OR_IMPLEMENT;
 
   /**
+   * If `true`, mixins are allowed to inherit from types other than Object, and
+   * are allowed to reference `super`.
+   */
+  final bool enableSuperMixins;
+
+  /**
    * Initialize a newly created error verifier.
    */
   ErrorVerifier(this._errorReporter, this._currentLibrary, this._typeProvider,
-      this._inheritanceManager) {
+      this._inheritanceManager, this.enableSuperMixins) {
     this._isInSystemLibrary = _currentLibrary.source.isInSystemLibrary;
     this._hasExtUri = _currentLibrary.hasExtUri;
     _isEnclosingConstructorConst = false;
     _isInCatchClause = false;
     _isInStaticVariableDeclaration = false;
     _isInInstanceVariableDeclaration = false;
     _isInInstanceVariableInitializer = false;
     _isInConstructorInitializer = false;
     _isInStaticMethod = false;
     _boolType = _typeProvider.boolType;
@@ skipping 1372 matching lines @@
         problemReported = true;
       } else {
         ClassElement mixinElement = (mixinType as InterfaceType).element;
         if (_checkForExtendsOrImplementsDeferredClass(
             mixinName, CompileTimeErrorCode.MIXIN_DEFERRED_CLASS)) {
           problemReported = true;
         }
         if (_checkForMixinDeclaresConstructor(mixinName, mixinElement)) {
           problemReported = true;
         }
-        if (_checkForMixinInheritsNotFromObject(mixinName, mixinElement)) {
+        if (!enableSuperMixins &&
+            _checkForMixinInheritsNotFromObject(mixinName, mixinElement)) {
           problemReported = true;
         }
         if (_checkForMixinReferencesSuper(mixinName, mixinElement)) {
           problemReported = true;
         }
       }
     }
     return problemReported;
   }
 
@@ skipping 2537 matching lines @@
 
   /**
    * Verify that the given mixin does not reference 'super'. The [mixinName] is
    * the node to report problem on. The [mixinElement] is the mixing to
    * evaluate.
    *
    * See [CompileTimeErrorCode.MIXIN_REFERENCES_SUPER].
    */
   bool _checkForMixinReferencesSuper(
       TypeName mixinName, ClassElement mixinElement) {
-    if (mixinElement.hasReferenceToSuper) {
+    if (!enableSuperMixins && mixinElement.hasReferenceToSuper) {
       _errorReporter.reportErrorForNode(
           CompileTimeErrorCode.MIXIN_REFERENCES_SUPER, mixinName,
           [mixinElement.name]);
     }
     return false;
   }
 
   /**
    * Verify that the given [constructor] has at most one 'super' initializer.
    *
@@ skipping 1762 matching lines @@
     toCheck.add(type.element);
     // type arguments
     if (type is InterfaceType) {
       InterfaceType interfaceType = type;
       for (DartType typeArgument in interfaceType.typeArguments) {
         _addTypeToCheck(typeArgument);
       }
     }
   }
 }