https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86195
--- Comment #2 from Paolo Monteverde <paolo.monteverde at gmail dot com> --- (In reply to Jonathan Wakely from comment #1) > This started to fail on trunk with r251438 > > It seems to have been fixed on the gcc-8-branch though. 8.1.1 is not a > release, we need to know exactly which version you're using (as requested by > https://gcc.gnu.org/bugs/ when submitting a new bug report). I spotted the original error on g++ (GCC) 8.1.1 20180531 running on Arch Linux. The simplified example above is failing on https://wandbox.org/permlink/VMBVdHgzkcH2xLlb. The only needed option is -std=c++14 or above.