[libcxx-commits] [libcxx] [libc++] Add [[nodiscard]] to std::prev and std::next (PR #109550)

[Louis Dionne via libcxx-commits]

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@@ -43,25 +43,26 @@ next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n =
 namespace ranges {
 struct __next {
   template <input_or_output_iterator _Ip>
-  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
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ldionne wrote:

We also want to add this to `std::next` above. But since that code must work before C++17, you can use `[[__nodiscard__]]` instead above, which is accepted as an extension before C++17.

The same comment applies to `std::prev`.

https://github.com/llvm/llvm-project/pull/109550