Add operator-> to the key-value iterator for QHash and QMap

This patch adds the arrow operator to the stl-like key-value
iterator (QKeyValueIterator) for QMap and QHash.

This allows using normal member access syntax it->first and it->second
instead of having to use (*it).first and (*it).second.

[ChangeLog][QtCore][Containers] Added operator-> to the key-value
iterator for QHash/QMap.

Change-Id: I9cfa6480784ebce147fcfbf37fec5ad0080e2899
Reviewed-by: Vitaly Fanaskov <vitaly.fanaskov@qt.io>

src/corelib/tools/qiterator.h

@@ -195,7 +195,6 @@ public:
     typedef typename Iterator::iterator_category iterator_category;
     typedef typename Iterator::difference_type difference_type;
     typedef std::pair<Key, T> value_type;
-    typedef const value_type *pointer;
     typedef const value_type &reference;
 
     QKeyValueIterator() = default;
@@ -206,6 +205,31 @@ public:
         return std::pair<Key, T>(i.key(), i.value());
     }
 
+    struct pointer {
+        pointer(value_type&& r_)
+            : r(std::move(r_))
+        {}
+
+        pointer() = default;
+        pointer(const pointer &other) = default;
+        pointer(pointer &&other) = default;
+        pointer& operator=(const pointer &other) = default;
+        pointer& operator=(pointer &&other) = default;
+
+        value_type& operator*() const {
+            return r;
+        }
+
+        value_type r;
+        const value_type *operator->() const {
+            return &r;
+        }
+    };
+
+    pointer operator->() const {
+        return pointer(std::pair<Key, T>(i.key(), i.value()));
+    }
+
     friend bool operator==(QKeyValueIterator lhs, QKeyValueIterator rhs) noexcept { return lhs.i == rhs.i; }
     friend bool operator!=(QKeyValueIterator lhs, QKeyValueIterator rhs) noexcept { return lhs.i != rhs.i; }
 

src/corelib/tools/qiterator.qdoc

@@ -57,7 +57,7 @@
     \internal
 */
 
-/*! \typedef QKeyValueIterator::pointer
+/*! \struct QKeyValueIterator::pointer
     \internal
 */
 
@@ -75,11 +75,20 @@
     Constructs a QKeyValueIterator on top of \a o.
 */
 
-/*! \fn template<typename Key, typename T, class Iterator> const T &QKeyValueIterator<Key, T, Iterator>::operator*() const
+/*! \fn template<typename Key, typename T, class Iterator> std::pair<Key, T> QKeyValueIterator<Key, T, Iterator>::operator*() const
 
     Returns the current entry as a pair.
 */
 
+/*! \fn template<typename Key, typename T, class Iterator> pointer QKeyValueIterator<Key, T, Iterator>::operator->() const
+
+    Returns the current entry as a pointer-like object to the pair.
+
+    \since 5.15
+
+    \sa operator*()
+*/
+
 /*! \fn template<typename Key, typename T, class Iterator> bool operator==(QKeyValueIterator<Key, T, Iterator> lhs, QKeyValueIterator<Key, T, Iterator> rhs)
     \relates QKeyValueIterator
 

tests/auto/corelib/tools/qhash/tst_qhash.cpp

@@ -1144,6 +1144,12 @@ void tst_QHash::keyValueIterator()
 
         entry_type pair(it.key(), it.value());
         QCOMPARE(*key_value_it, pair);
+        QCOMPARE(key_value_it->first, pair.first);
+        QCOMPARE(key_value_it->second, pair.second);
+        QCOMPARE(&(*key_value_it).first, &it.key());
+        QCOMPARE(&key_value_it->first,   &it.key());
+        QCOMPARE(&(*key_value_it).second, &it.value());
+        QCOMPARE(&key_value_it->second,   &it.value());
         ++key_value_it;
         ++it;
     }

tests/auto/corelib/tools/qmap/tst_qmap.cpp

@@ -882,6 +882,12 @@ void tst_QMap::keyValueIterator()
 
         entry_type pair(it.key(), it.value());
         QCOMPARE(*key_value_it, pair);
+        QCOMPARE(key_value_it->first, pair.first);
+        QCOMPARE(key_value_it->second, pair.second);
+        QCOMPARE(&(*key_value_it).first, &it.key());
+        QCOMPARE(&key_value_it->first,   &it.key());
+        QCOMPARE(&(*key_value_it).second, &it.value());
+        QCOMPARE(&key_value_it->second,   &it.value());
         ++key_value_it;
         ++it;
     }