Introduce common superclass to fix ClassElement.node (issue 23120)

pkg/analyzer/lib/src/generated/element.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.element;
 
 import 'dart:collection';
@@ skipping 207 matching lines @@
   List<InterfaceType> get mixins;
 
   /**
    * Return the resolved [ClassDeclaration] or [EnumDeclaration] node that
    * declares this [ClassElement].
    *
    * This method is expensive, because resolved AST might be evicted from cache,
    * so parsing and resolving will be performed.
    */
   @override
-  AstNode get node;
+  NamedCompilationUnitMember get node;
 
   /**
    * Return the superclass of this class, or `null` if the class represents the
    * class 'Object'. All other classes will have a non-`null` superclass. If the
    * superclass was not explicitly declared then the implicit superclass
    * 'Object' will be returned.
    *
    * <b>Note:</b> Because the element model represents the state of the code, it
    * is possible for it to be semantically invalid. In particular, it is not
    * safe to assume that the inheritance structure of a class does not contain a
@@ skipping 455 matching lines @@
 
   /**
    * Set whether an error has reported explaining why this class is an
    * invalid mixin application.
    */
   void set mixinErrorsReported(bool value) {
     setModifier(Modifier.MIXIN_ERRORS_REPORTED, value);
   }
 
   @override
-  AstNode get node {
+  NamedCompilationUnitMember get node {
     if (isEnum) {
       return getNodeMatching((node) => node is EnumDeclaration);
     } else {
       return getNodeMatching(
           (node) => node is ClassDeclaration || node is ClassTypeAlias);
     }
   }
 
   /**
    * Set whether this class is defined by a typedef construct.
@@ skipping 9541 matching lines @@
     // void <: void (by reflexivity)
     // bottom <: void (as bottom is a subtype of all types).
     // void <: dynamic (as dynamic is a supertype of all types)
     return identical(type, this) || type.isDynamic;
   }
 
   @override
   VoidTypeImpl substitute2(
       List<DartType> argumentTypes, List<DartType> parameterTypes) => this;
 }