anchor.diff:    Primitive get input => inputRef.definition;
   
     Yield(Primitive input, this.hasStar)
  -    : this.inputRef = new Reference<Primitive>(input);
  +      : this.inputRef = new Reference<Primitive>(input);
   
     @override
     accept(Visitor visitor) {
  
positive.code:   Primitive get value => valueRef.definition;
  
    ReifyRuntimeType(Primitive value, this.sourceInformation)
      : this.valueRef = new Reference<Primitive>(value);
  
    @override
    accept(Visitor visitor) => visitor.visitReifyRuntimeType(this);
  
negative.code:   /// same node.
    String debugString([Map annotations]) {
      return new SExpressionStringifier()
          .withAnnotations(annotations)
          .visit(this);
    }
  
    /// Prints the result of [debugString].
  