[libcxx-commits] [libcxx] [libc++][ranges] Applied [[nodiscard]] to `lazy_split` (PR #208036)

[Lucas Mellone via libcxx-commits]

https://github.com/lknknm created https://github.com/llvm/llvm-project/pull/208036

[[nodiscard]] should be applied to functions where discarding the return value is most likely a correctness issue.

- https://libcxx.llvm.org/CodingGuidelines.html
- https://wg21.link/range.lazy.split

Towards https://github.com/llvm/llvm-project/issues/172124

>From 1a1da3d615018ef52c9eefcbb376679f5cdd7505 Mon Sep 17 00:00:00 2001
From: Lucas Mellone <github.snugness349 at passinbox.com>
Date: Tue, 7 Jul 2026 18:00:56 +0200
Subject: [PATCH] initial: nodiscard implementation to lazy_split_view.h

---
 libcxx/include/__ranges/lazy_split_view.h | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/libcxx/include/__ranges/lazy_split_view.h b/libcxx/include/__ranges/lazy_split_view.h
index 938dca24cc4fc..01d398a0ac6d8 100644
--- a/libcxx/include/__ranges/lazy_split_view.h
+++ b/libcxx/include/__ranges/lazy_split_view.h
@@ -95,14 +95,14 @@ class lazy_split_view : public view_interface<lazy_split_view<_View, _Pattern>>
   _LIBCPP_HIDE_FROM_ABI constexpr explicit lazy_split_view(_Range&& __r, range_value_t<_Range> __e)
       : __base_(views::all(std::forward<_Range>(__r))), __pattern_(views::single(std::move(__e))) {}
 
-  _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
     requires copy_constructible<_View>
   {
     return __base_;
   }
-  _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
     if constexpr (forward_range<_View>) {
       return __outer_iterator < __simple_view<_View> && __simple_view < _Pattern >> {*this, ranges::begin(__base_)};
     } else {
@@ -111,19 +111,19 @@ class lazy_split_view : public view_interface<lazy_split_view<_View, _Pattern>>
     }
   }
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
     requires forward_range<_View> && forward_range<const _View>
   {
     return __outer_iterator<true>{*this, ranges::begin(__base_)};
   }
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto end()
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto end()
     requires forward_range<_View> && common_range<_View>
   {
     return __outer_iterator < __simple_view<_View> && __simple_view < _Pattern >> {*this, ranges::end(__base_)};
   }
 
-  _LIBCPP_HIDE_FROM_ABI constexpr auto end() const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto end() const {
     if constexpr (forward_range<_View> && forward_range<const _View> && common_range<const _View>) {
       return __outer_iterator<true>{*this, ranges::end(__base_)};
     } else {
@@ -206,7 +206,7 @@ class lazy_split_view : public view_interface<lazy_split_view<_View, _Pattern>>
       requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
         : __parent_(__i.__parent_), __current_(std::move(__i.__current_)) {}
 
-    _LIBCPP_HIDE_FROM_ABI constexpr value_type operator*() const { return value_type{*this}; }
+    [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr value_type operator*() const { return value_type{*this}; }
 
     _LIBCPP_HIDE_FROM_ABI constexpr __outer_iterator& operator++() {
       const auto __end = ranges::end(__parent_->__base_);
@@ -342,14 +342,14 @@ class lazy_split_view : public view_interface<lazy_split_view<_View, _Pattern>>
 
     _LIBCPP_HIDE_FROM_ABI constexpr explicit __inner_iterator(__outer_iterator<_Const> __i) : __i_(std::move(__i)) {}
 
-    _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __i_.__current(); }
-    _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() &&
+    [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __i_.__current(); }
+    [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() &&
       requires forward_range<_View>
     {
       return std::move(__i_.__current());
     }
 
-    _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const { return *__i_.__current(); }
+    [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const { return *__i_.__current(); }
 
     _LIBCPP_HIDE_FROM_ABI constexpr __inner_iterator& operator++() {
       __incremented_ = true;
@@ -385,7 +385,7 @@ class lazy_split_view : public view_interface<lazy_split_view<_View, _Pattern>>
       return __x.__is_done();
     }
 
-    _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto)
+    [[nodiscard]] _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto)
     iter_move(const __inner_iterator& __i) noexcept(noexcept(ranges::iter_move(__i.__outer_current()))) {
       return ranges::iter_move(__i.__outer_current());
     }