// Note: optional trailing text is often a comment, e.g. '// namespace xyz'.
  Renderer &BlockClose(const string &text = "");
  template <typename... Args>
  Renderer BlockClose(absl::string_view text, const Args &...args) {
    return BlockClose(absl::Substitute(text, args...));
  }

 protected:
  RendererContext context_;
};

}  // namespace cpp
}  // namespace generator

        BlockOpen("while (i == 1)");
        {
          CommentLine("Do nothing, really....");
          CodeLine("#if 0");
          Statement("call()");
          CodeLine("#endif");
          BlockClose();
        }
        BlockClose("  // comment ending TestFunction");
      }
    }
  };

  SourceCode code;
  TestRenderer(code).Render();

  string expected = R"(// File level comment.
#include "header.h"

  return *this;
}

Renderer& Renderer::BlockOpen(const string& text) {
  context_.code.AddLineWithIndent(absl::StrCat(text, " {"));
  context_.code.IncreaseIndent();
  return *this;
}

Renderer& Renderer::BlockClose(const string& text) {
  context_.code.DecreaseIndent();
  context_.code.AddLineWithIndent(absl::StrCat("}", text));
  return *this;
}

}  // namespace cpp
}  // namespace generator

  comment_.Render();
  if (context_.mode == RendererContext::kHeader) {
    Statement(Signature());
  } else {
    BlockOpen(Signature());
    OpImplementationRenderer(context_, op_).Render();
    BlockClose();
  }
  BlankLine();
}

}  // namespace cpp
}  // namespace generator