[Bug c++/123738] [16 Regression] "is not a constant expression" in code using a string literal operator template

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123738

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 63437
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=63437&action=edit
Slightly reduced testcase