anchor.diff:        result.add(".");
       }
       result.add(procedure.name.name);
  -    return result;
  -  }
  -
  -  List<Object> visitPartialInstantiationConstant(
  -      PartialInstantiationConstant node) {
  -    List<Object> result = node.tearOffConstant.accept(this);
  +  }
  +
  +  void visitPartialInstantiationConstant(PartialInstantiationConstant node) {
  +    node.tearOffConstant.accept(this);
       if (node.types.isNotEmpty) {
         result.add("<");
         bool first = true;
         for (DartType typeArg in node.types) {
           if (!first) result.add(", ");
  -        result.addAll(typeArg.accept(this));
  +        typeArg.accept(this);
           first = false;
         }
         result.add(">");
       }
  -    return result;
  -  }
  -
  -  List<Object> visitTypeLiteralConstant(TypeLiteralConstant node) {
  -    return node.type.accept(this);
  +  }
  +
  +  void visitTypeLiteralConstant(TypeLiteralConstant node) {
  +    node.type.accept(this);
     }
   }
   
  
positive.code:   List<Object> labelType(DartType type) {
      // TODO(askesc): Remove null check when we are completely null clean here.
      if (type == null) return ["null-type"];
      return type.accept(this);
    }
  
    /// Pretty-print a constant.
  
negative.code:     bool first = true;
      for (int i = 0; i < node.requiredParameterCount; i++) {
        if (!first) result.add(", ");
        node.positionalParameters[i].accept(this);
        first = false;
      }
      if (node.positionalParameters.length > node.requiredParameterCount) {
  