[Bug c++/87464] Gcc reports hard error instead of SFINAE out the related method

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87464

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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           Keywords|                            |diagnostic

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Adding diagnostic keyword, since the issue is simply that when showing the
reason for substitution failure we show an error not a note.