[Bug c++/94454] ICE 'canonical types differ for identical types'

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94454

--- Comment #11 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Nathan Sidwell from comment #10)
> I cannot reproduce it,

it is frustratingly difficult to do so.

> but looking at the gist referenced in comment #1 I
> see that the complaint is about two instances of the same instantiation of
> struct std::integral_constant<bool, and_v<__is_constructible(Ts)...> >
> 
> One of which has __attribute__ ((__abi_tag__ ("cxx11"))) attached to it. 
> That seems to be the error -- how did that abi_tag get there? it's not on
> the original declaration. 
> 
> I can't see how those could have become attached. AFAICT we don't propagate
> attributes from the arguments of an instantiation, to the instantiation
> itself (and that wouldn't explain it here, as 'and_v' and __is_constructible
> are unattributed.

this does not seem to be reproducible, possibly a result of some other bug
that's since been fixed.

- I don't think it's the smoking gun (but could be that the relevant field
contains something random).