[Bug c++/126280] [13/14/15/16/17 Regression] "used but never defined" SFINAE warning for function template in specific circumstances with fold expression

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126280

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 65058
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65058&action=edit
Reduced testcase without the fold expression