[Bug c++/65072] Segfault when parsing dectlype in trailing return type

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65072

--- Comment #9 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Likely started with r151360 -- which doesn't reveal much, this rev was a part
of LTO merge, dealing with gimplification of types and symbols.