[libcxx-commits] [libcxx] [libc++] implement std::flat_set (PR #125241)

[Louis Dionne via libcxx-commits]

================
@@ -0,0 +1,158 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_set>
+
+// explicit flat_set(container_type key_cont, const key_compare& comp = key_compare());
+// template<class Allocator>
+//   flat_set(const container_type& key_cont, const Allocator& a);
+// template<class Alloc>
+//   flat_set(const container_type& key_cont, const key_compare& comp, const Alloc& a);
+
+#include <algorithm>
+#include <deque>
+#include <flat_set>
+#include <functional>
+#include <type_traits>
+#include <vector>
+
+#include "min_allocator.h"
+#include "MoveOnly.h"
+#include "test_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+
+template <class T>
+void conversion_test(T);
+
+template <class T, class... Args>
+concept ImplicitlyConstructible = requires(Args&&... args) { conversion_test<T>({std::forward<Args>(args)...}); };
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_set<int, C, V1>;
+    using M2 = std::flat_set<int, C, V2>;
+    static_assert(std::is_constructible_v<M1, const V1&, const A1&>);
+    static_assert(std::is_constructible_v<M2, const V2&, const A2&>);
+    static_assert(!std::is_constructible_v<M1, const V1&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, const V2&, const A1&>);
+
+    static_assert(std::is_constructible_v<M1, const V1&, const C&, const A1&>);
+    static_assert(std::is_constructible_v<M2, const V2&, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M1, const V1&, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, const V2&, const C&, const A1&>);
+  }
+  {
+    // flat_set(container_type)
+    using M             = std::flat_set<int>;
+    std::vector<int> ks = {1, 1, 1, 2, 2, 3, 2, 3, 3};
+    auto m              = M(ks);
+    assert(std::ranges::equal(m, std::vector<int>{1, 2, 3}));
+
+    // explicit
+    static_assert(std::is_constructible_v<M, const std::vector<int>&>);
+    static_assert(!ImplicitlyConstructible<M, const std::vector<int>&>);
+  }
+  {
+    // flat_set(container_type)
+    // move-only
+    MoveOnly expected[] = {3, 2, 1};
+    using Ks            = std::deque<MoveOnly, min_allocator<MoveOnly>>;
+    using M             = std::flat_set<MoveOnly, std::greater<MoveOnly>, Ks>;
+    Ks ks;
+    ks.push_back(1);
+    ks.push_back(3);
+    ks.push_back(2);
+    auto m = M(std::move(ks));
+    assert(ks.empty()); // it was moved-from
+    assert(std::ranges::equal(m, expected));
+  }
+  {
+    // flat_set(container_type)
+    // container's allocator is used
+    using A = test_allocator<int>;
+    using M = std::flat_set<int, std::less<int>, std::deque<int, A>>;
+    auto ks = std::deque<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(5));
+    auto m  = M(std::move(ks));
+    assert(ks.empty()); // it was moved-from
+    assert((m == M{1, 2, 3}));
+    auto keys = std::move(m).extract();
+    assert(keys.get_allocator() == A(5));
+  }
+  {
+    // flat_set(container_type , key_compare)
+    using C             = test_less<int>;
+    using M             = std::flat_set<int, C>;
+    std::vector<int> ks = {1, 1, 1, 2, 2, 3, 2, 3, 3};
+    auto m              = M(ks, C(4));
+    assert(std::ranges::equal(m, std::vector<int>{1, 2, 3}));
+    assert(m.key_comp() == C(4));
+
+    // explicit
+    static_assert(std::is_constructible_v<M, const std::vector<int>&, const C&>);
+    static_assert(!ImplicitlyConstructible<M, const std::vector<int>&, const C&>);
+  }
+  {
+    // flat_set(container_type , const Allocator&)
+    using A = test_allocator<int>;
+    using M = std::flat_set<int, std::less<int>, std::deque<int, A>>;
+    auto ks = std::deque<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(5));
+    auto m  = M(ks, A(4)); // replaces the allocators
+    assert(!ks.empty());   // it was an lvalue above
+    assert((m == M{1, 2, 3}));
+    auto keys = std::move(m).extract();
+    assert(keys.get_allocator() == A(4));
+  }
+  {
+    // flat_set(container_type , const Allocator&)
+    // explicit(false)
+    using A = test_allocator<int>;
+    using M = std::flat_set<int, std::less<int>, std::deque<int, A>>;
+    static_assert(ImplicitlyConstructible<M, const std::deque<int, A>&, const A&>);
+    auto ks = std::deque<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(5));
+    M m     = {ks, A(4)}; // implicit ctor
+    assert(!ks.empty());  // it was an lvalue above
+    assert((m == M{1, 2, 3}));
+    auto keys = std::move(m).extract();
+    assert(keys.get_allocator() == A(4));
+  }
----------------
ldionne wrote:

I would suggest testing this constructor the same way you tested the other ones in this file, i.e.

```
{
    // flat_set(container_type , const Allocator&)
    using A = test_allocator<int>;
    using M = std::flat_set<int, std::less<int>, std::deque<int, A>>;
    auto ks = std::deque<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(5));
    auto m  = M(ks, A(4)); // replaces the allocators
    assert(!ks.empty());   // it was an lvalue above
    assert((m == M{1, 2, 3}));
    auto keys = std::move(m).extract();
    assert(keys.get_allocator() == A(4));

    // explicit(false)
    static_assert(ImplicitlyConstructible<...>);
    // etc...
}
```

https://github.com/llvm/llvm-project/pull/125241