4 files changed, 46 insertions, 16 deletions
diff --git a/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp b/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp
index f1be49c1d4..b7e56c5ec3 100644
--- a/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp
+++ b/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp
@@ -297,11 +297,11 @@ inline size_t qHash(const std::unordered_set<int> &key, size_t seed = 0)
 //! [31]
 
 //! [32]
-size_t qHash(K key);
-size_t qHash(const K &key);
-
 size_t qHash(K key, size_t seed);
 size_t qHash(const K &key, size_t seed);
+
+size_t qHash(K key);        // deprecated, do not use
+size_t qHash(const K &key); // deprecated, do not use
 //! [32]
 
 //! [33]
diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp
index 2d2061c707..7ff53fe67e 100644
--- a/src/corelib/tools/qhash.cpp
+++ b/src/corelib/tools/qhash.cpp
@@ -1683,10 +1683,15 @@ size_t qHash(long double key, size_t seed) noexcept
 
     The two-arguments overloads take an unsigned integer that should be used to
     seed the calculation of the hash function. This seed is provided by QHash
-    in order to prevent a family of \l{algorithmic complexity attacks}. If both
-    a one-argument and a two-arguments overload are defined for a key type,
-    the latter is used by QHash (note that you can simply define a
-    two-arguments version, and use a default value for the seed parameter).
+    in order to prevent a family of \l{algorithmic complexity attacks}.
+
+    \note In Qt 6 it is possible to define a \c{qHash()} overload
+    taking only one argument; support for this is deprecated. Starting
+    with Qt 7, it will be mandatory to use a two-arguments overload. If
+    both a one-argument and a two-arguments overload are defined for a
+    key type, the latter is used by QHash (note that you can simply
+    define a two-arguments version, and use a default value for the
+    seed parameter).
 
     The second way to provide a hashing function is by specializing
     the \c{std::hash} class for the key type \c{K}, and providing a
diff --git a/src/corelib/tools/qhashfunctions.h b/src/corelib/tools/qhashfunctions.h
index 029d98674c..bcb8caf1f7 100644
--- a/src/corelib/tools/qhashfunctions.h
+++ b/src/corelib/tools/qhashfunctions.h
@@ -68,14 +68,6 @@ Q_DECL_CONST_FUNCTION constexpr size_t hash(size_t key, size_t seed) noexcept
     }
 }
 
-template <typename T, typename = void>
-constexpr inline bool HasQHashSingleArgOverload = false;
-
-template <typename T>
-constexpr inline bool HasQHashSingleArgOverload<T, std::enable_if_t<
-    std::is_convertible_v<decltype(qHash(std::declval<const T &>())), size_t>
->> = true;
-
 template <typename T1, typename T2> static constexpr bool noexceptPairHash();
 }
 
@@ -141,6 +133,9 @@ Q_DECL_CONST_FUNCTION constexpr inline size_t qHash(std::nullptr_t, size_t seed
 {
     return seed;
 }
+template <class Enum, std::enable_if_t<std::is_enum_v<Enum>, bool> = true>
+Q_DECL_CONST_FUNCTION constexpr inline size_t qHash(Enum e, size_t seed = 0) noexcept
+{ return QHashPrivate::hash(qToUnderlying(e), seed); }
 
 // (some) Qt types
 Q_DECL_CONST_FUNCTION constexpr inline size_t qHash(const QChar key, size_t seed = 0) noexcept { return qHash(key.unicode(), seed); }
@@ -168,9 +163,26 @@ template <typename Enum>
 Q_DECL_CONST_FUNCTION constexpr inline size_t qHash(QFlags<Enum> flags, size_t seed = 0) noexcept
 { return qHash(flags.toInt(), seed); }
 
-template <typename T, std::enable_if_t<QHashPrivate::HasQHashSingleArgOverload<T>, bool> = true>
+// ### Qt 7: remove this "catch-all" overload logic, and require users
+// to provide the two-argument version of qHash.
+#if (QT_VERSION < QT_VERSION_CHECK(7, 0, 0))
+// Beware of moving this code from here. It needs to see all the
+// declarations of qHash overloads for C++ fundamental types *before*
+// its own declaration.
+namespace QHashPrivate {
+template <typename T, typename = void>
+constexpr inline bool HasQHashSingleArgOverload = false;
+
+template <typename T>
+constexpr inline bool HasQHashSingleArgOverload<T, std::enable_if_t<
+    std::is_convertible_v<decltype(qHash(std::declval<const T &>())), size_t>
+>> = true;
+}
+
+template <typename T, std::enable_if_t<QHashPrivate::HasQHashSingleArgOverload<T> && !std::is_enum_v<T>, bool> = true>
 size_t qHash(const T &t, size_t seed) noexcept(noexcept(qHash(t)))
 { return qHash(t) ^ seed; }
+#endif // < Qt 7
 
 template<typename T>
 bool qHashEquals(const T &a, const T &b)
diff --git a/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp b/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp
index 2d04579253..6daf418e7b 100644
--- a/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp
+++ b/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp
@@ -53,6 +53,8 @@ private Q_SLOTS:
     void stdPair_string_pairIntInt()    { stdPair_template(QString("Hello"), std::make_pair(42, -47)); } // QTBUG-92910
     void stdPair_int_pairIntPairIntInt() { stdPair_template(1, std::make_pair(2, std::make_pair(3, 4))); }
 
+    void enum_int_consistent_hash_qtbug108032();
+
 #if QT_DEPRECATED_SINCE(6, 6)
     void setGlobalQHashSeed();
 #endif
@@ -372,6 +374,17 @@ void tst_QHashFunctions::stdPair_template(const T1 &t1, const T2 &t2)
     QCOMPARE(qHash(vpair, seed), qHash(vpair, seed));
 }
 
+void tst_QHashFunctions::enum_int_consistent_hash_qtbug108032()
+{
+    enum E { E1, E2, E3 };
+
+    static_assert(QHashPrivate::HasQHashSingleArgOverload<E>);
+
+    QCOMPARE(qHash(E1, seed), qHash(int(E1), seed));
+    QCOMPARE(qHash(E2, seed), qHash(int(E2), seed));
+    QCOMPARE(qHash(E3, seed), qHash(int(E3), seed));
+}
+
 #if QT_DEPRECATED_SINCE(6, 6)
 void tst_QHashFunctions::setGlobalQHashSeed()
 {