anchor.diff:    bool get isConst => varDecl.isConst;
     bool get isFinal => varDecl.isFinal;
     
  +  dynamic accept(ElementVisitor visitor) => visitor.visitFieldElement(this);
  +
     FieldElement(FieldDeclaration this.ast,VariableDeclaration this.varDecl, ClassElement classDecl): super(classDecl); 
   }
   
  
positive.code:   bool get isStatic => ast.isStatic;
    bool get isSynthetic => ast.isSynthetic;
      
    MethodElement(MethodDeclaration this.ast, ClassElement classDecl): super(classDecl);
  }
  
  
negative.code: class SourceElement extends Block {
    Source source;
    CompilationUnit ast;
    LibraryIdentifier library = null;
    List<Source> partOf = <Source>[];
    List<Source> imports = <Source>[];
    List<Source> parts = <Source>[];
    List<Source> exports = <Source>[];
  