[libcxx-commits] [libcxx] [libc++] Implement a type-safe iterator for optional (PR #154239)

[William Tran-Viet via libcxx-commits]

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@@ -688,52 +688,53 @@ private:
   using __pointer _LIBCPP_NODEBUG       = add_pointer_t<remove_reference_t<_Tp>>;
   using __const_pointer _LIBCPP_NODEBUG = add_pointer_t<const remove_reference_t<_Tp>>;
 
-public:
 #    if _LIBCPP_STD_VER >= 26
+  template <typename _Underlying>
+  using __iter _LIBCPP_NODEBUG = __capacity_aware_iterator<_Underlying, optional<_Tp>, 1>;
+
+public:
 #      ifdef _LIBCPP_ABI_BOUNDED_ITERATORS_IN_OPTIONAL
   using iterator       = __bounded_iter<__wrap_iter<__pointer>>;
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smallp-o-p wrote:

I'm not sure whether it's worth it to wrap `__bounded_iter`, other than for type safety in the ABI break mode. The check provided by `__capacity_aware_iterator` would become useless overhead, although may just get optimized out? Not sure.  

https://github.com/llvm/llvm-project/pull/154239