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[libc++][ranges] Applied [[nodiscard]] to common_view #173176

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[libc++][ranges] Applied [[nodiscard]] to common_view #173176

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14 changes: 7 additions & 7 deletions libcxx/include/__ranges/common_view.h
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Original file line number Diff line number Diff line change
Expand Up @@ -56,16 +56,16 @@ class common_view : public view_interface<common_view<_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 (random_access_range<_View> && sized_range<_View>)
return ranges::begin(__base_);
else
return common_iterator<iterator_t<_View>, sentinel_t<_View>>(ranges::begin(__base_));
}

_LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
requires range<const _View>
{
if constexpr (random_access_range<const _View> && sized_range<const _View>)
Expand All @@ -74,14 +74,14 @@ class common_view : public view_interface<common_view<_View>> {
return common_iterator<iterator_t<const _View>, sentinel_t<const _View>>(ranges::begin(__base_));
}

_LIBCPP_HIDE_FROM_ABI constexpr auto end() {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto end() {
if constexpr (random_access_range<_View> && sized_range<_View>)
return ranges::begin(__base_) + ranges::size(__base_);
else
return common_iterator<iterator_t<_View>, sentinel_t<_View>>(ranges::end(__base_));
}

_LIBCPP_HIDE_FROM_ABI constexpr auto end() const
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
requires range<const _View>
{
if constexpr (random_access_range<const _View> && sized_range<const _View>)
Expand All @@ -90,13 +90,13 @@ class common_view : public view_interface<common_view<_View>> {
return common_iterator<iterator_t<const _View>, sentinel_t<const _View>>(ranges::end(__base_));
}

_LIBCPP_HIDE_FROM_ABI constexpr auto size()
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto size()
requires sized_range<_View>
{
return ranges::size(__base_);
}

_LIBCPP_HIDE_FROM_ABI constexpr auto size() const
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
requires sized_range<const _View>
{
return ranges::size(__base_);
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61 changes: 61 additions & 0 deletions libcxx/test/libcxx/ranges/range.adaptors/range.common.view/nodiscard.verify.cpp
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Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// REQUIRES: std-at-least-c++20

// Check that functions are marked [[nodiscard]]

#include <ranges>
#include <utility>

struct NonCommonView : std::ranges::view_base {
int* begin() const;
const int* end() const;

int* base();

int* begin();
const int* end();

constexpr std::size_t size() const { return 0; };
};
static_assert(!std::ranges::common_range<NonCommonView>);

void test() {
NonCommonView range;

auto v = std::views::common(range);

// [range.common.view]

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
std::move(v).base();

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
v.begin();
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
std::as_const(v).begin();

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
v.end();
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
std::as_const(v).end();

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
v.size();
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
std::as_const(v).size();

// [range.common.overview]

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
std::views::common(v);

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
std::views::common(range);
}
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