message: Uniquify {func,type}.derived
diff: @@ -2264,9 +2264,13 @@ optional<std::vector<std::unique_ptr<IndexFile>>> ParseWithTu(
  for (std::unique_ptr<IndexFile>& entry : result) {
  entry->import_file = file;
  entry->args = args;
  - for (IndexFunc& func : entry->funcs)
  + for (IndexFunc& func : entry->funcs) {
  + // e.g. declaration + out-of-line definition
  + Uniquify(func.derived);
  Uniquify(func.uses);
  + }
  for (IndexType& type : entry->types) {
  + Uniquify(type.derived);
  Uniquify(type.uses);
  // e.g. declaration + out-of-line definition
  Uniquify(type.def.funcs);
  