[Bug c++/120287] [12/13/14/15/16 Regression] internal compiler error: tree check: expected class 'type', have 'exceptional' (error_mark) in is_std_substitution, at cp/mangle.cc:507

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120287

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Should this be two separate bugs? There might be one that's been there since
gcc-5 but there's still a newer one that's is a gcc-15 regression.

It's only ice-on-invalid-code though, so I guess it's not too important.