[libcxx-commits] [libcxx] [libc++] P2770R0: "Stashing stashing iterators for proper flattening" (PR #66033)

[Jakub Mazurkiewicz via libcxx-commits]

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@@ -209,21 +215,24 @@ namespace ranges {
 
     static constexpr bool __ref_is_glvalue = is_reference_v<range_reference_t<_Base>>;
 
+    static constexpr bool _OuterPresent = forward_range<_Base>;
+    using _OuterType                    = _If<_OuterPresent, _Outer, std::__empty>;
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JMazurkiewicz wrote:

`_Outer` is not really a cache (but `iterator_t<_Base>`), so I think that `std::__empty` is a better choice here. 

https://github.com/llvm/llvm-project/pull/66033