Unprotected use of std::default_initializable in char8_view

[anarthal]

In file: ./boost/parser/detail/text/transcode_view.hpp:331:46

Build can be found here (edited link): https://drone.cpp.al/boostorg/mysql/545/12/3

Compiler details:

• toolset=clang-11
• cxxstd=20
• variant=debug
• warnings=extra
• OS: Ubuntu 22.04

[tzlaine]

How the hell did I miss exactly one of three default ctors?! The other two are qritten correctly. Anyway, this is now fixed on a branch.