message: Add missing const
diff: @@ -164,7 +164,7 @@ struct Type {
  enum_def(_ed),
  fixed_length(_fixed_length) {}
  - bool operator==(const Type &o) {
  + bool operator==(const Type &o) const {
  return base_type == o.base_type && element == o.element &&
  struct_def == o.struct_def && enum_def == o.enum_def;
  }
  