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-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 // UNSUPPORTED: c++03, c++11, c++14, c++17
10 
11 // template<class I1, class I2, class Out,
12 //     class R = ranges::less, class P1 = identity, class P2 = identity>
13 //   concept mergeable = see below;                           // since C++20
14 
15 #include <iterator>
16 
17 #include <functional>
18 
19 #include "test_iterators.h"
20 #include "test_macros.h"
21 
22 using CompDefault = std::ranges::less;
23 using CompInt = bool(*)(int, int);
24 using ProjDefault = std::identity;
25 
26 using Input = cpp20_input_iterator<int*>;
27 static_assert( std::input_iterator<Input>);
28 using InputLong = cpp20_input_iterator<long*>;
29 static_assert( std::input_iterator<InputLong>);
30 
31 using Output = cpp17_output_iterator<int*>;
32 static_assert( std::weakly_incrementable<Output>);
33 
34 static_assert( std::indirectly_copyable<Input, Output>);
35 static_assert( std::indirectly_copyable<InputLong, Output>);
36 static_assert( std::indirect_strict_weak_order<CompDefault, Input, Input>);
37 static_assert( std::indirect_strict_weak_order<CompInt, Input, Input>);
38 static_assert( std::indirect_strict_weak_order<CompDefault, Input, InputLong>);
39 static_assert( std::indirect_strict_weak_order<CompInt, Input, InputLong>);
40 
41 // All requirements satisfied.
42 static_assert( std::mergeable<Input, Input, Output>);
43 static_assert( std::mergeable<Input, Input, Output, CompInt>);
44 static_assert( std::mergeable<Input, Input, Output, CompInt, ProjDefault>);
45 
46 // Non-default projections.
47 struct Foo {};
48 using ProjFooToInt = int(*)(Foo);
49 using ProjFooToLong = long(*)(Foo);
50 static_assert( std::indirect_strict_weak_order<CompDefault,
51     std::projected<Foo*, ProjFooToInt>, std::projected<Foo*, ProjFooToLong>>);
52 static_assert( std::mergeable<Foo*, Foo*, Foo*, CompDefault, ProjFooToInt, ProjFooToLong>);
53 static_assert( std::indirect_strict_weak_order<CompInt,
54     std::projected<Foo*, ProjFooToInt>, std::projected<Foo*, ProjFooToLong>>);
55 static_assert( std::mergeable<Foo*, Foo*, Foo*, CompInt, ProjFooToInt, ProjFooToLong>);
56 
57 // I1 or I2 is not an input iterator.
58 static_assert(!std::input_iterator<Output>);
59 static_assert(!std::mergeable<Output, Input, Output>);
60 static_assert(!std::mergeable<Input, Output, Output>);
61 
62 // O is not weakly incrementable.
63 struct NotWeaklyIncrementable {
64   int& operator*() const;
65 };
66 
67 static_assert(!std::weakly_incrementable<NotWeaklyIncrementable>);
68 static_assert( std::indirectly_copyable<Input, NotWeaklyIncrementable>);
69 static_assert( std::indirect_strict_weak_order<CompDefault, Input, Input>);
70 static_assert(!std::mergeable<Input, Input, NotWeaklyIncrementable>);
71 
72 // I1 or I2 is not indirectly copyable into O.
73 struct AssignableOnlyFromInt {
74   AssignableOnlyFromInt& operator=(int);
75   template <class T>
76   AssignableOnlyFromInt& operator=(T) = delete;
77 };
78 using OutputOnlyInt = cpp17_output_iterator<AssignableOnlyFromInt*>;
79 static_assert( std::weakly_incrementable<OutputOnlyInt>);
80 
81 static_assert( std::indirectly_copyable<Input, OutputOnlyInt>);
82 static_assert(!std::indirectly_copyable<InputLong, OutputOnlyInt>);
83 static_assert( std::indirect_strict_weak_order<CompDefault, Input, InputLong>);
84 static_assert( std::mergeable<Input, Input, OutputOnlyInt>);
85 static_assert(!std::mergeable<Input, InputLong, OutputOnlyInt>);
86 static_assert(!std::mergeable<InputLong, Input, OutputOnlyInt>);
87 
88 // No indirect strict weak order between I1 and I2 (bad comparison functor).
89 using GoodComp = bool(*)(int, int);
90 static_assert( std::indirect_strict_weak_order<GoodComp, Input, Input>);
91 static_assert( std::mergeable<Input, Input, Output, GoodComp>);
92 using BadComp = bool(*)(int*, int*);
93 static_assert(!std::indirect_strict_weak_order<BadComp, Input, Input>);
94 static_assert(!std::mergeable<Input, Input, Output, BadComp>);
95 
96 // No indirect strict weak order between I1 and I2 (bad projection).
97 using ToInt = int(*)(int);
98 using ToPtr = int*(*)(int);
99 static_assert( std::mergeable<Input, Input, Output, GoodComp, std::identity, std::identity>);
100 static_assert( std::mergeable<Input, Input, Output, GoodComp, ToInt, ToInt>);
101 static_assert(!std::mergeable<Input, Input, Output, GoodComp, ToPtr, ToInt>);
102 static_assert(!std::mergeable<Input, Input, Output, GoodComp, ToInt, ToPtr>);
103 static_assert(!std::mergeable<Input, Input, Output, bool(*)(int*, int), ToPtr, ToInt>);
104 static_assert(!std::mergeable<Input, Input, Output, bool(*)(int, int*), ToInt, ToPtr>);
105 
106 // A projection that only supports non-const references and has a non-const `operator()` still has to work.
107 struct ProjectionOnlyMutable {
108   int operator()(int&);
109   int operator()(int&&) const = delete;
110 };
111 static_assert( std::mergeable<Input, Input, Output, CompDefault, ProjectionOnlyMutable, ProjectionOnlyMutable>);
112 
113 // The output is weakly incrementable but not an output iterator.
114 struct WeaklyIncrementable {
115   using value_type = int;
116   using difference_type = int;
117 
118   int& operator*() const;
119   WeaklyIncrementable& operator++();
120   // `output_iterator` requires `i++` to return an iterator,
121   // while `weakly_incrementable` requires only that `i++` be well-formed.
122   void operator++(int);
123 };
124 static_assert( std::weakly_incrementable<WeaklyIncrementable>);
125 static_assert( std::indirectly_copyable<int*, WeaklyIncrementable>);
126 static_assert(!std::output_iterator<WeaklyIncrementable, int>);
127 static_assert( std::mergeable<Input, Input, WeaklyIncrementable>);
128