anchor.diff:    Catch(this.decl, this.body);
   
     accept(NodeVisitor visitor) => visitor.visitCatch(this);
  +  void visitChildren(NodeVisitor visitor) {
  +    decl.accept(visitor);
  +    body.accept(visitor);
  +  }
   }
   
   class With extends Statement {
  
positive.code:   Continue(this.id);
  
    accept(NodeVisitor visitor) => visitor.visitContinue(this);
  }
  
  class Break extends Statement {
  
negative.code:   Accsign(this.lhs, Expression val): super(val);
  
    accept(NodeVisitor visitor) => visitor.visitAccsign(this);
    void visitChildren(NodeVisitor visitor) {
      lhs.accept(visitor);
      val.accept(visitor);
    }
  }
  
  class AccsignOp extends Accsign {
  