void testRuntimeSpan(Span sp) { _LIBCPP_ASSERT(sp.back(), ""); assert(std::addressof(sp.back()) == sp.data() + sp.size() - 1); }
constexpr bool testConstexprSpan(Span sp) { _LIBCPP_ASSERT(sp.back(), ""); return std::addressof(sp.back()) == sp.data() + sp.size() - 1; }