Issue 3931. Visit children nodes safely.

compiler/java/com/google/dart/compiler/ast/DartClass.java

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file

[Brian Wilkerson, 2012/06/30 00:44:21]

nit: copyright year

 // 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.
 
 package com.google.dart.compiler.ast;
 
 import com.google.dart.compiler.resolver.ClassNodeElement;
 import com.google.dart.compiler.resolver.Element;
 
 import java.util.List;
 
@@ skipping 152 matching lines @@
   }
 
   public DartStringLiteral getNativeName() {
     return nativeName;
   }
 
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
     super.visitChildren(visitor);
     typeParameters.accept(visitor);
-    if (superclass != null) {
-      superclass.accept(visitor);
-    }
+    safelyVisitChild(superclass, visitor);
     interfaces.accept(visitor);
-    if (defaultClass != null) {
-      defaultClass.accept(visitor);
-    }
+    safelyVisitChild(defaultClass, visitor);
     members.accept(visitor);
   }
 
   @Override
   public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitClass(this);
   }
 }