On Thu, 17 Jun 2021, 16:50 Patrick Palka via Libstdc++, < libstd...@gcc.gnu.org> wrote:
> This implements the wording changes of P2325R3 "Views should not be > required to be default constructible". Changes are relatively > straightforward, besides perhaps those to __box (which now stands > for copyable-box instead of semiregular-box) and __non_propagating_cache. > > For __box, this patch implements the recommended practice to also avoid > std::optional when the boxed type is nothrow_move/copy_constructible. > > For __non_propagating_cache, now that it's used by split_view::_M_current, > we need to add assignment from a value of the underlying type to the > subset of the std::optional API implemented for the cache (needed by > split_view::begin()). Hence the new __non_propagating_cache::operator= > overload. > > While we're changing __box, this fixes the undesirable list-init in > the constuctors of the partial specialization as reported in PR100475 > comment #7. As I said on IRC, I'm not sure why the defaulted default constructors need to be constrained (rather than just letting them get deleted) but the patch is OK.
