109 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// UNSUPPORTED: c++03, c++11, c++14, c++1710 11// constexpr auto begin() requires (!simple-view<V>)12// { return ranges::begin(base_); }13//14// constexpr auto begin() const15// requires range<const V> &&16// indirect_unary_predicate<const Pred, iterator_t<const V>>17// { return ranges::begin(base_); }18 19#include <cassert>20#include <ranges>21#include <type_traits>22#include <utility>23 24#include "types.h"25 26// Test Constraints27template <class T>28concept HasConstBegin = requires(const T& ct) { ct.begin(); };29 30template <class T>31concept HasBegin = requires(T& t) { t.begin(); };32 33template <class T>34concept HasConstAndNonConstBegin =35 HasConstBegin<T> &&36 requires(T& t, const T& ct) { requires !std::same_as<decltype(t.begin()), decltype(ct.begin())>; };37 38template <class T>39concept HasOnlyNonConstBegin = HasBegin<T> && !HasConstBegin<T>;40 41template <class T>42concept HasOnlyConstBegin = HasConstBegin<T> && !HasConstAndNonConstBegin<T>;43 44struct Pred {45 constexpr bool operator()(int i) const { return i > 5; }46};47 48static_assert(HasOnlyConstBegin<std::ranges::take_while_view<SimpleView, Pred>>);49 50static_assert(HasOnlyNonConstBegin<std::ranges::take_while_view<ConstNotRange, Pred>>);51 52static_assert(HasConstAndNonConstBegin<std::ranges::take_while_view<NonSimple, Pred>>);53 54struct NotPredForConst {55 constexpr bool operator()(int& i) const { return i > 5; }56};57static_assert(HasOnlyNonConstBegin<std::ranges::take_while_view<NonSimple, NotPredForConst>>);58 59constexpr bool test() {60 // simple-view61 {62 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};63 SimpleView v{buffer};64 std::ranges::take_while_view twv(v, Pred{});65 std::same_as<int*> decltype(auto) it1 = twv.begin();66 assert(it1 == buffer);67 std::same_as<int*> decltype(auto) it2 = std::as_const(twv).begin();68 assert(it2 == buffer);69 }70 71 // const not range72 {73 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};74 ConstNotRange v{buffer};75 std::ranges::take_while_view twv(v, Pred{});76 std::same_as<int*> decltype(auto) it1 = twv.begin();77 assert(it1 == buffer);78 }79 80 // NonSimple81 {82 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};83 NonSimple v{buffer};84 std::ranges::take_while_view twv(v, Pred{});85 std::same_as<int*> decltype(auto) it1 = twv.begin();86 assert(it1 == buffer);87 std::same_as<const int*> decltype(auto) it2 = std::as_const(twv).begin();88 assert(it2 == buffer);89 }90 91 // NotPredForConst92 // LWG 3450: The const overloads of `take_while_view::begin/end` are underconstrained93 {94 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};95 NonSimple v{buffer};96 std::ranges::take_while_view twv(v, NotPredForConst{});97 std::same_as<int*> decltype(auto) it1 = twv.begin();98 assert(it1 == buffer);99 }100 101 return true;102}103 104int main(int, char**) {105 test();106 static_assert(test());107 return 0;108}109