[Bug c++/81239] std::__cxx11::string& visible in gcc warning output

[jg at jguk dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81239

--- Comment #2 from Jonny Grant <jg at jguk dot org> ---
Created attachment 44492
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44492&action=edit
Better test case