// { dg-do run { target c++17 xfail *-*-* } }
// { dg-require-debug-mode "" }

#include <unordered_set>
#include <algorithm>
#include <testsuite_hooks.h>

using test_type = std::unordered_set<int>;

void
test01()
{
  test_type c0{ 1, 2, 3, 5, 6, 7 };
  std::unordered_multiset<int> c1{ 1, 1, 2, 2, 3, 3, 4, 4, 5 };

  auto it1 = c1.find(1);
  auto it41 = c1.find(4);
  auto it42 = it41;
  ++it42;
  VERIFY( *it42 == 4 );

  c0.merge(std::move(c1));

  VERIFY( *it1 == 1 );
  VERIFY( c1.count(4) == 1 );
  VERIFY( it41 != it42 ); // Invalid iterator.
}

int
main()
{
  test01();
}