https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116399
--- Comment #10 from 康桓瑋 <hewillk at gmail dot com> --- (In reply to Jonathan Wakely from comment #9) > Currently aliases_view is allowed to be a common range, but not required to > be. > > If we specify that its sentinel type is std::default_sentinel, that would > require it to be a non-common range. Why would we want that? > > If an implementation decides to use a different design for the aliases_view > which is more efficient with a common range, your suggestion would forbid > them from using that. > > So I don't think we should require that. Whether libstdc++ should make that > change is a different matter. > > I guess we could also defined the sentinel as an enum type, which might be a > little less expensive than a new class type. Or just use default_sentinel_t. But we should at least make it clear in the standard whether aliases_view is common range is *unspecified*, right? Currently, the return type of begin()/end() is *implementation defined*, which seems confusing because the two types appear to be the same as we indicated for iterators in the [container], and containers are always common ranges.
