QHash/QMap: don't return const from value(), key()

... it breaks move semantics.

We can change these, since they're templates and a short survey shows
that no-one in Qt was crazy enough to inherit an exported class from
QHash or QMap.

Otherwise this would be BiC on MSVC, which encodes the return type.

There's also no safety benefit here, as none of the overloads returns
by reference, so users cannot expect map.value(key).mutate() to have
an effect on the element in the container.

In this, key() and value() differ from op[], which also returns const,
but whose overload returns a reference. op[] is therefore not proposed
here.

[ChangeLog][QtCore][QHash/QMultiHash/QMap/QMultiMap] The value() and
key() member functions now return T (was: const T), enabling move
semantics on their return values.

Change-Id: I0e5f53f9834caad458e3bde27f1daacbb4bac71b
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp
index 7ebc374d9f..1e5af7e0ce 100644
--- a/src/corelib/tools/qhash.cpp
+++ b/src/corelib/tools/qhash.cpp
@@ -1449,7 +1449,7 @@ uint qHash(long double key, uint seed) noexcept
     \sa count(), QMultiHash::contains()
 */
 
-/*! \fn template <class Key, class T> const T QHash<Key, T>::value(const Key &key) const
+/*! \fn template <class Key, class T> T QHash<Key, T>::value(const Key &key) const
 
     Returns the value associated with the \a key.
 
@@ -1461,7 +1461,7 @@ uint qHash(long double key, uint seed) noexcept
     \sa key(), values(), contains(), operator[]()
 */
 
-/*! \fn template <class Key, class T> const T QHash<Key, T>::value(const Key &key, const T &defaultValue) const
+/*! \fn template <class Key, class T> T QHash<Key, T>::value(const Key &key, const T &defaultValue) const
     \overload
 
     If the hash contains no item with the given \a key, the function returns