[Bug c++/85864] [8/9 Regression] template argument string literal operator with default argument doesnt work in templates

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85864

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
                 CC|                            |jason at gcc dot gnu.org
      Known to work|                            |7.3.0
            Summary|template argument string    |[8/9 Regression] template
                   |literal operator with       |argument string literal
                   |default argument doesnt     |operator with default
                   |work in templates           |argument doesnt work in
                   |                            |templates
      Known to fail|                            |8.1.0, 9.0

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm not sure if this is valid, but it started to be rejected with with r258039

            PR c++/84489 - dependent default template argument

            * pt.c (type_unification_real): Handle early substitution failure.