-Wdeprecated-literal-operator from clang++-20 for 'operator"" _c' (i.e. with space)

[MichaelChirico]

yap/include/boost/yap/algorithm_fwd.hpp

Line 180 in 7f99028

constexpr auto operator"" _p()

yap/include/boost/yap/user_macros.hpp

Line 819 in 7f99028

constexpr auto operator"" _p() \

The fix can be trivial, but I think there's some back-compatibility considerations I lack the context to adjudicate, see sister issues e.g.

boostorg/hana#521

[tzlaine]

Man, that is a crazy-ass issue. I'm not complaining at you, mind you. I'm complaining at EWG/the committee. I'll try to work this in during this release cycle. Thanks for reporting it, here and on Boost.Parser!