[Bug c++/77427] [6/7 Regression] ice when canonical types differ for identical types

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77427

--- Comment #8 from Tom de Vries <vries at gcc dot gnu.org> ---
Created attachment 39537
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39537&action=edit
tentative patch

currently doing bootstrap and reg-test