This was recently approved for C++26, but there's no harm in
implementing it unconditionally for C++20 and C++23. As it says in the
paper, it doesn't change the meaning of any valid code. It only enables
things that were previously ill-formed for questionable reasons.
libstdc++-v3/ChangeLog:
* include/bits/iterator_concepts.h (projected): Replace class
template with alias template denoting an ADL-proofed helper.
(incremental_traits<projected<Iter, Proj>>): Remove.
* testsuite/24_iterators/indirect_callable/projected-adl.cc:
New test.
(cherry picked from commit 6eafdfc73c21d7a5e59e18c9dee275af5bf6d979)
Jonathan Wakely
d96e4962f5