https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100983
--- Comment #6 from Artur Bać <gcc at ebasoft dot com.pl> --- The typename was from my real code by mistake where value_type s template param. But in real code withing template I have to use typename and it doesn't work with trunk too. https://godbolt.org/z/E6Pavhfza