Second half of C++17's splicing maps and sets

This commit adds a merge member function to all the map and set containers,
which splices nodes from the source container. This completes support for
P0083r3.

Differential revision: https://reviews.llvm.org/D48896

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@345744 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/containers/associative/map/map.modifiers/merge.pass.cpp

@@ -0,0 +1,149 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <map>
+
+// class map
+
+// template <class C2>
+//   void merge(map<key_type, value_type, C2, allocator_type>& source);
+// template <class C2>
+//   void merge(map<key_type, value_type, C2, allocator_type>&& source);
+// template <class C2>
+//   void merge(multimap<key_type, value_type, C2, allocator_type>& source);
+// template <class C2>
+//   void merge(multimap<key_type, value_type, C2, allocator_type>&& source);
+
+#include <map>
+#include "test_macros.h"
+#include "Counter.h"
+
+template <class Map>
+bool map_equal(const Map& map, Map other)
+{
+    return map == other;
+}
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+struct throw_comparator
+{
+    bool& should_throw_;
+
+    throw_comparator(bool& should_throw) : should_throw_(should_throw) {}
+
+    template <class T>
+    bool operator()(const T& lhs, const T& rhs) const
+    {
+        if (should_throw_)
+            throw 0;
+        return lhs < rhs;
+    }
+};
+#endif
+
+int main()
+{
+    {
+        std::map<int, int> src{{1, 0}, {3, 0}, {5, 0}};
+        std::map<int, int> dst{{2, 0}, {4, 0}, {5, 0}};
+        dst.merge(src);
+        assert(map_equal(src, {{5,0}}));
+        assert(map_equal(dst, {{1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}}));
+    }
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    {
+        bool do_throw = false;
+        typedef std::map<Counter<int>, int, throw_comparator> map_type;
+        map_type src({{1, 0}, {3, 0}, {5, 0}}, throw_comparator(do_throw));
+        map_type dst({{2, 0}, {4, 0}, {5, 0}}, throw_comparator(do_throw));
+
+        assert(Counter_base::gConstructed == 6);
+
+        do_throw = true;
+        try
+        {
+            dst.merge(src);
+        }
+        catch (int)
+        {
+            do_throw = false;
+        }
+        assert(!do_throw);
+        assert(map_equal(src, map_type({{1, 0}, {3, 0}, {5, 0}}, throw_comparator(do_throw))));
+        assert(map_equal(dst, map_type({{2, 0}, {4, 0}, {5, 0}}, throw_comparator(do_throw))));
+    }
+#endif
+    assert(Counter_base::gConstructed == 0);
+    struct comparator
+    {
+        comparator() = default;
+
+        bool operator()(const Counter<int>& lhs, const Counter<int>& rhs) const
+        {
+            return lhs < rhs;
+        }
+    };
+    {
+        typedef std::map<Counter<int>, int, std::less<Counter<int>>> first_map_type;
+        typedef std::map<Counter<int>, int, comparator> second_map_type;
+        typedef std::multimap<Counter<int>, int, comparator> third_map_type;
+
+        {
+            first_map_type first{{1, 0}, {2, 0}, {3, 0}};
+            second_map_type second{{2, 0}, {3, 0}, {4, 0}};
+            third_map_type third{{1, 0}, {3, 0}};
+
+            assert(Counter_base::gConstructed == 8);
+
+            first.merge(second);
+            first.merge(third);
+
+            assert(map_equal(first, {{1, 0}, {2, 0}, {3, 0}, {4, 0}}));
+            assert(map_equal(second, {{2, 0}, {3, 0}}));
+            assert(map_equal(third, {{1, 0}, {3, 0}}));
+
+            assert(Counter_base::gConstructed == 8);
+        }
+        assert(Counter_base::gConstructed == 0);
+        {
+            first_map_type first{{1, 0}, {2, 0}, {3, 0}};
+            second_map_type second{{2, 0}, {3, 0}, {4, 0}};
+            third_map_type third{{1, 0}, {3, 0}};
+
+            assert(Counter_base::gConstructed == 8);
+
+            first.merge(std::move(second));
+            first.merge(std::move(third));
+
+            assert(map_equal(first, {{1, 0}, {2, 0}, {3, 0}, {4, 0}}));
+            assert(map_equal(second, {{2, 0}, {3, 0}}));
+            assert(map_equal(third, {{1, 0}, {3, 0}}));
+
+            assert(Counter_base::gConstructed == 8);
+        }
+        assert(Counter_base::gConstructed == 0);
+    }
+    assert(Counter_base::gConstructed == 0);
+    {
+        std::map<int, int> first;
+        {
+            std::map<int, int> second;
+            first.merge(second);
+            first.merge(std::move(second));
+        }
+        {
+            std::multimap<int, int> second;
+            first.merge(second);
+            first.merge(std::move(second));
+        }
+    }
+}