[Bug c++/89766] [8 Regression] ICE: canonical types differ for identical types, -std=c++17

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89766

--- Comment #5 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Rimvydas (RJ) from comment #4)
> @Martin: Yes, ICE happens for valid code too only if -fchecking=1. Reduced
> cases are invalid and rejected by 9.0.1 20190319 and 8.2.1 20181127.
> However 8.3.1 20190319 accepts them even for -fchecking=0.

Please attach the valid code snippet.