For std::span, these are free functions in namespace std and therefore
work for anything implicitly convertible to std::span,
incl. QSpan. But they're C++20, QSpan needs something for C++17
builds.
By adding them as hidden friends for QSpan, we allow unqualifid calls
to transparently resolve to the respective overload, ensuring
source-compatibility between std:: and QSpan, and, eventually, a
transition back to std::as_*_bytes.
I considered the alternative to add these functions in the q20
namespace, but q20::as_bytes() would have to take QSpan, and QSpan is
convertible from more types than std::span, so we wouldn't be able to
guarantee that std::as_bytes(t) works for all T t for which
q20::as_bytes(t) works, the fundamental guarantee for namespace qNN.
[ChangeLog][QtCore][QSpan] Added std::span-style as_bytes() and
as_writable_bytes() functions.
Fixes: QTBUG-125489
Change-Id: Ia9a7560c7843e182892608178433be7349c825ba
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
462c958a92