Implement the first part of N4258: 'Cleaning up noexcept in the Library'. This patch deals with swapping containers, and implements a more strict noexcept specification (a conforming extension) than the standard mandates.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@242056 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/containers/associative/set/set.special/swap_noexcept.pass.cpp

@@ -12,6 +12,10 @@
 // void swap(set& c)
 //     noexcept(!allocator_type::propagate_on_container_swap::value ||
 //              __is_nothrow_swappable<allocator_type>::value);
+//
+//  In C++17, the standard says that swap shall have:
+//     noexcept(allocator_traits<Allocator>::is_always_equal::value &&
+//              noexcept(swap(declval<Compare&>(), declval<Compare&>())));                 
 
 // This tests a conforming extension
 
@@ -33,6 +37,60 @@ struct some_comp
     typedef std::true_type propagate_on_container_swap;
 };
 
+template <class T>
+struct some_comp2
+{
+    typedef T value_type;
+    
+    some_comp2() {}
+    some_comp2(const some_comp2&) {}
+    void deallocate(void*, unsigned) {}
+    typedef std::true_type propagate_on_container_swap;
+};
+
+#if TEST_STD_VER >= 14
+template <typename T>
+void swap(some_comp2<T>&, some_comp2<T>&) noexcept {}
+#endif
+
+template <class T>
+struct some_alloc
+{
+    typedef T value_type;
+    
+    some_alloc() {}
+    some_alloc(const some_alloc&);
+    void deallocate(void*, unsigned) {}
+
+    typedef std::true_type propagate_on_container_swap;
+};
+
+template <class T>
+struct some_alloc2
+{
+    typedef T value_type;
+    
+    some_alloc2() {}
+    some_alloc2(const some_alloc2&);
+    void deallocate(void*, unsigned) {}
+
+    typedef std::false_type propagate_on_container_swap;
+    typedef std::true_type is_always_equal;
+};
+
+template <class T>
+struct some_alloc3
+{
+    typedef T value_type;
+    
+    some_alloc3() {}
+    some_alloc3(const some_alloc3&);
+    void deallocate(void*, unsigned) {}
+
+    typedef std::false_type propagate_on_container_swap;
+    typedef std::false_type is_always_equal;
+};
+
 int main()
 {
 #if __has_feature(cxx_noexcept)
@@ -56,5 +114,35 @@ int main()
         C c1, c2;
         static_assert(!noexcept(swap(c1, c2)), "");
     }
+
+#if TEST_STD_VER >= 14
+    { // POCS allocator, throwable swap for comp
+    typedef std::set<MoveOnly, some_comp <MoveOnly>, some_alloc <MoveOnly>> C;
+    C c1, c2;
+    static_assert(!noexcept(swap(c1, c2)), "");
+    }
+    { // always equal allocator, throwable swap for comp
+    typedef std::set<MoveOnly, some_comp <MoveOnly>, some_alloc2<MoveOnly>> C;
+    C c1, c2;
+    static_assert(!noexcept(swap(c1, c2)), "");
+    }
+    { // POCS allocator, nothrow swap for comp
+    typedef std::set<MoveOnly, some_comp2<MoveOnly>, some_alloc <MoveOnly>> C;
+    C c1, c2;
+    static_assert( noexcept(swap(c1, c2)), "");
+    }
+    { // always equal allocator, nothrow swap for comp
+    typedef std::set<MoveOnly, some_comp2<MoveOnly>, some_alloc2<MoveOnly>> C;
+    C c1, c2;
+    static_assert( noexcept(swap(c1, c2)), "");
+    }
+
+    { // NOT always equal allocator, nothrow swap for comp
+    typedef std::set<MoveOnly, some_comp2<MoveOnly>, some_alloc3<MoveOnly>> C;
+    C c1, c2;
+    static_assert( noexcept(swap(c1, c2)), "");
+    }
+#endif
+
 #endif
 }