QVariant: fix comparison of enums to numerics

qIsNumericType does not return true for enum types, which meant we never
called numericCompare() or numericEquals() when one of the types was an
enum.

Task-number: QTBUG-108188
Change-Id: I3d74c753055744deb8acfffd172449c68af19367
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

2 files changed, 197 insertions, 28 deletions

diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index 91a17335fd..9fb30c6f28 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -2158,15 +2158,49 @@ static bool qIsFloatingPoint(uint tp)
     return tp == QMetaType::Double || tp == QMetaType::Float;
 }
 
+static bool canBeNumericallyCompared(const QtPrivate::QMetaTypeInterface *iface1,
+                                     const QtPrivate::QMetaTypeInterface *iface2)
+{
+    if (!iface1 || !iface2)
+        return false;
+
+    // We don't need QMetaType::id() here because the type Id is always stored
+    // directly for all built-in types.
+    bool isNumeric1 = qIsNumericType(iface1->typeId);
+    bool isNumeric2 = qIsNumericType(iface2->typeId);
+
+    // if they're both numeric (or QString), then they can be compared
+    if (isNumeric1 && isNumeric2)
+        return true;
+
+    bool isEnum1 = iface1->flags & QMetaType::IsEnumeration;
+    bool isEnum2 = iface2->flags & QMetaType::IsEnumeration;
+
+    // if both are enums, we can only compare if they are the same enum
+    // (the language does allow comparing two different enum types, but that's
+    // usually considered poor coding and produces a warning)
+    if (isEnum1 && isEnum2)
+        return QMetaType(iface1) == QMetaType(iface2);
+
+    // if one is an enum and the other is a numeric, we can compare too
+    if (isEnum1 && isNumeric2)
+        return true;
+    if (isNumeric1 && isEnum2)
+        return true;
+
+    // we need at least one enum and one numeric...
+    return false;
+}
+
 static int numericTypePromotion(const QtPrivate::QMetaTypeInterface *iface1,
                                 const QtPrivate::QMetaTypeInterface *iface2)
 {
+    Q_ASSERT(canBeNumericallyCompared(iface1, iface2));
+
     // We don't need QMetaType::id() here because the type Id is always stored
     // directly for the types we're comparing against below.
     uint t1 = iface1->typeId;
     uint t2 = iface2->typeId;
-    Q_ASSERT(qIsNumericType(t1));
-    Q_ASSERT(qIsNumericType(t2));
 
     if ((t1 == QMetaType::Bool && t2 == QMetaType::QString) ||
         (t2 == QMetaType::Bool && t1 == QMetaType::QString))
@@ -2295,7 +2329,7 @@ bool QVariant::equals(const QVariant &v) const
 
     if (metatype != v.metaType()) {
         // try numeric comparisons, with C++ type promotion rules (no conversion)
-        if (qIsNumericType(metatype.id()) && qIsNumericType(v.d.type().id()))
+        if (canBeNumericallyCompared(metatype.iface(), v.d.type().iface()))
             return numericCompare(&d, &v.d) == QPartialOrdering::Equivalent;
 #ifndef QT_BOOTSTRAPPED
         // if both types are related pointers to QObjects, check if they point to the same object
@@ -2339,7 +2373,7 @@ QPartialOrdering QVariant::compare(const QVariant &lhs, const QVariant &rhs)
     QMetaType t = lhs.d.type();
     if (t != rhs.d.type()) {
         // try numeric comparisons, with C++ type promotion rules (no conversion)
-        if (qIsNumericType(lhs.d.type().id()) && qIsNumericType(rhs.d.type().id()))
+        if (canBeNumericallyCompared(lhs.d.type().iface(), rhs.d.type().iface()))
             return numericCompare(&lhs.d, &rhs.d);
 #ifndef QT_BOOTSTRAPPED
         if (canConvertMetaObject(lhs.metaType(), rhs.metaType()))
diff --git a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
index e7579a7927..ccb7952407 100644
--- a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
+++ b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
@@ -59,6 +59,29 @@ struct QVariantFromValueCompiles<T, std::void_t<decltype (QVariant::fromValue(st
 static_assert(QVariantFromValueCompiles<int>::value);
 static_assert(!QVariantFromValueCompiles<QObject>::value);
 
+enum EnumTest_Enum0 { EnumTest_Enum0_value = 42, EnumTest_Enum0_negValue = -8 };
+Q_DECLARE_METATYPE(EnumTest_Enum0)
+enum EnumTest_Enum1 : qint64 { EnumTest_Enum1_value = 42, EnumTest_Enum1_bigValue = (Q_INT64_C(1) << 33) + 50 };
+Q_DECLARE_METATYPE(EnumTest_Enum1)
+
+enum EnumTest_Enum3 : qint64 { EnumTest_Enum3_value = -47, EnumTest_Enum3_bigValue = (Q_INT64_C(1) << 56) + 5  };
+Q_DECLARE_METATYPE(EnumTest_Enum3)
+enum EnumTest_Enum4 : quint64 { EnumTest_Enum4_value = 47, EnumTest_Enum4_bigValue = (Q_INT64_C(1) << 52) + 45 };
+Q_DECLARE_METATYPE(EnumTest_Enum4)
+enum EnumTest_Enum5 : uint { EnumTest_Enum5_value = 47 };
+Q_DECLARE_METATYPE(EnumTest_Enum5)
+enum EnumTest_Enum6 : uchar { EnumTest_Enum6_value = 47 };
+Q_DECLARE_METATYPE(EnumTest_Enum6)
+enum class EnumTest_Enum7 { EnumTest_Enum7_value = 47, ensureSignedEnum7 = -1 };
+Q_DECLARE_METATYPE(EnumTest_Enum7)
+enum EnumTest_Enum8 : short { EnumTest_Enum8_value = 47 };
+Q_DECLARE_METATYPE(EnumTest_Enum8)
+
+template <typename T> int qToUnderlying(QFlags<T> f)
+{
+    return f.toInt();
+}
+
 class tst_QVariant : public QObject
 {
     Q_OBJECT
@@ -2728,6 +2751,10 @@ void tst_QVariant::compareNumerics_data() const
     static const auto asString = [](const QVariant &v) {
         if (v.isNull())
             return QStringLiteral("null");
+        if (v.metaType().flags() & QMetaType::IsEnumeration)
+            return v.metaType().flags() & QMetaType::IsUnsignedEnumeration ?
+                        QString::number(v.toULongLong()) :
+                        QString::number(v.toLongLong());
         switch (v.typeId()) {
         case QMetaType::Char:
         case QMetaType::Char16:
@@ -2768,9 +2795,15 @@ QT_WARNING_PUSH
 QT_WARNING_DISABLE_CLANG("-Wsign-compare")
 QT_WARNING_DISABLE_GCC("-Wsign-compare")
 QT_WARNING_DISABLE_MSVC(4018)   // '<': signed/unsigned mismatch
-    static const auto addComparePair = [](auto value1, auto value2) {
+    static const auto addComparePairWithResult = [](auto value1, auto value2, QPartialOrdering order) {
         QVariant v1 = QVariant::fromValue(value1);
         QVariant v2 = QVariant::fromValue(value2);
+        QTest::addRow("%s(%s)-%s(%s)", v1.typeName(), qPrintable(asString(v1)),
+                      v2.typeName(), qPrintable(asString(v2)))
+                << v1 << v2 << order;
+    };
+
+    static const auto addComparePair = [](auto value1, auto value2) {
         QPartialOrdering order = QPartialOrdering::Unordered;
         if (value1 == value2)
             order = QPartialOrdering::Equivalent;
@@ -2778,9 +2811,7 @@ QT_WARNING_DISABLE_MSVC(4018)   // '<': signed/unsigned mismatch
             order = QPartialOrdering::Less;
         else if (value1 > value2)
             order = QPartialOrdering::Greater;
-        QTest::addRow("%s(%s)-%s(%s)", v1.typeName(), qPrintable(asString(v1)),
-                      v2.typeName(), qPrintable(asString(v2)))
-                << v1 << v2 << order;
+        addComparePairWithResult(value1, value2, order);
     };
 QT_WARNING_POP
 
@@ -2815,6 +2846,10 @@ QT_WARNING_POP
     addSingleType(quint64(0));
     addSingleType(0.f);
     addSingleType(0.0);
+    addList(std::array{ EnumTest_Enum0{}, EnumTest_Enum0_value, EnumTest_Enum0_negValue });
+    addList(std::array{ EnumTest_Enum1{}, EnumTest_Enum1_value, EnumTest_Enum1_bigValue });
+    addList(std::array{ EnumTest_Enum7{}, EnumTest_Enum7::EnumTest_Enum7_value, EnumTest_Enum7::ensureSignedEnum7 });
+    addList(std::array{ Qt::AlignRight|Qt::AlignHCenter, Qt::AlignCenter|Qt::AlignVCenter });
 
     // heterogeneous
     addComparePair(char(0), qint8(-127));
@@ -2888,6 +2923,52 @@ QT_WARNING_POP
         addComparePair(-double(Q_INT64_C(1) << 53), Q_INT64_C(1) << 53);
         addComparePair(-double(Q_INT64_C(1) << 53) + 1, (Q_INT64_C(1) << 53) + 1);
     }
+
+    // enums vs integers
+    addComparePair(EnumTest_Enum0_value, 0);
+    addComparePair(EnumTest_Enum0_value, 0U);
+    addComparePair(EnumTest_Enum0_value, 0LL);
+    addComparePair(EnumTest_Enum0_value, 0ULL);
+    addComparePair(EnumTest_Enum0_value, int(EnumTest_Enum0_value));
+    addComparePair(EnumTest_Enum0_value, qint64(EnumTest_Enum0_value));
+    addComparePair(EnumTest_Enum0_value, quint64(EnumTest_Enum0_value));
+    addComparePair(EnumTest_Enum0_negValue, int(EnumTest_Enum0_value));
+    addComparePair(EnumTest_Enum0_negValue, qint64(EnumTest_Enum0_value));
+    addComparePair(EnumTest_Enum0_negValue, quint64(EnumTest_Enum0_value));
+    addComparePair(EnumTest_Enum0_negValue, int(EnumTest_Enum0_negValue));
+    addComparePair(EnumTest_Enum0_negValue, qint64(EnumTest_Enum0_negValue));
+    addComparePair(EnumTest_Enum0_negValue, quint64(EnumTest_Enum0_negValue));
+
+    addComparePair(EnumTest_Enum1_value, 0);
+    addComparePair(EnumTest_Enum1_value, 0U);
+    addComparePair(EnumTest_Enum1_value, 0LL);
+    addComparePair(EnumTest_Enum1_value, 0ULL);
+    addComparePair(EnumTest_Enum1_value, int(EnumTest_Enum1_value));
+    addComparePair(EnumTest_Enum1_value, qint64(EnumTest_Enum1_value));
+    addComparePair(EnumTest_Enum1_value, quint64(EnumTest_Enum1_value));
+    addComparePair(EnumTest_Enum1_bigValue, int(EnumTest_Enum1_value));
+    addComparePair(EnumTest_Enum1_bigValue, qint64(EnumTest_Enum1_value));
+    addComparePair(EnumTest_Enum1_bigValue, quint64(EnumTest_Enum1_value));
+    addComparePair(EnumTest_Enum1_bigValue, int(EnumTest_Enum1_bigValue));
+    addComparePair(EnumTest_Enum1_bigValue, qint64(EnumTest_Enum1_bigValue));
+    addComparePair(EnumTest_Enum1_bigValue, quint64(EnumTest_Enum1_bigValue));
+
+    addComparePair(EnumTest_Enum3_value, 0);
+    addComparePair(EnumTest_Enum3_value, 0U);
+    addComparePair(EnumTest_Enum3_value, 0LL);
+    addComparePair(EnumTest_Enum3_value, 0ULL);
+    addComparePair(EnumTest_Enum3_value, int(EnumTest_Enum3_value));
+    addComparePair(EnumTest_Enum3_value, qint64(EnumTest_Enum3_value));
+    addComparePair(EnumTest_Enum3_value, quint64(EnumTest_Enum3_value));
+    addComparePair(EnumTest_Enum3_bigValue, int(EnumTest_Enum3_value));
+    addComparePair(EnumTest_Enum3_bigValue, qint64(EnumTest_Enum3_value));
+    addComparePair(EnumTest_Enum3_bigValue, quint64(EnumTest_Enum3_value));
+    addComparePair(EnumTest_Enum3_bigValue, int(EnumTest_Enum3_bigValue));
+    addComparePair(EnumTest_Enum3_bigValue, qint64(EnumTest_Enum3_bigValue));
+    addComparePair(EnumTest_Enum3_bigValue, quint64(EnumTest_Enum3_bigValue));
+
+    // enums of different types always compare as unordered
+    addComparePairWithResult(EnumTest_Enum0_value, EnumTest_Enum1_value, QPartialOrdering::Unordered);
 }
 
 void tst_QVariant::compareNumerics() const
@@ -4818,27 +4899,16 @@ void tst_QVariant::pairElements()
     TEST_PAIR_ELEMENT_ACCESS(std::pair, int, QVariant, 44, 15)
 }
 
-enum EnumTest_Enum0 { EnumTest_Enum0_value = 42, EnumTest_Enum0_negValue = -8 };
-Q_DECLARE_METATYPE(EnumTest_Enum0)
-enum EnumTest_Enum1 : qint64 { EnumTest_Enum1_value = 42, EnumTest_Enum1_bigValue = (Q_INT64_C(1) << 33) + 50 };
-Q_DECLARE_METATYPE(EnumTest_Enum1)
-
-enum EnumTest_Enum3 : qint64 { EnumTest_Enum3_value = -47, EnumTest_Enum3_bigValue = (Q_INT64_C(1) << 56) + 5  };
-Q_DECLARE_METATYPE(EnumTest_Enum3)
-enum EnumTest_Enum4 : quint64 { EnumTest_Enum4_value = 47, EnumTest_Enum4_bigValue = (Q_INT64_C(1) << 52) + 45 };
-Q_DECLARE_METATYPE(EnumTest_Enum4)
-enum EnumTest_Enum5 : uint { EnumTest_Enum5_value = 47 };
-Q_DECLARE_METATYPE(EnumTest_Enum5)
-enum EnumTest_Enum6 : uchar { EnumTest_Enum6_value = 47 };
-Q_DECLARE_METATYPE(EnumTest_Enum6)
-enum class EnumTest_Enum7 { EnumTest_Enum7_value = 47, ensureSignedEnum7 = -1 };
-Q_DECLARE_METATYPE(EnumTest_Enum7)
-enum EnumTest_Enum8 : short { EnumTest_Enum8_value = 47 };
-Q_DECLARE_METATYPE(EnumTest_Enum8)
-
 template<typename Enum> void testVariant(Enum value, bool *ok)
 {
     *ok = false;
+
+    auto canLosslesslyConvert = [=](auto zero) {
+        return sizeof(value) <= sizeof(zero) ||
+                value == Enum(decltype(zero)(qToUnderlying(value)));
+    };
+    bool losslessConvertToInt = canLosslesslyConvert(int{});
+
     QVariant var = QVariant::fromValue(value);
 
     QCOMPARE(var.userType(), qMetaTypeId<Enum>());
@@ -4851,7 +4921,6 @@ template<typename Enum> void testVariant(Enum value, bool *ok)
     QVERIFY(var.canConvert<qint64>());
     QVERIFY(var.canConvert<quint64>());
 
-
     QCOMPARE(var.value<Enum>(), value);
     QCOMPARE(var.value<int>(), static_cast<int>(value));
     QCOMPARE(var.value<uint>(), static_cast<uint>(value));
@@ -4865,7 +4934,7 @@ template<typename Enum> void testVariant(Enum value, bool *ok)
     QCOMPARE(var2.value<int>(), static_cast<int>(value));
 
     // unary + to silence gcc warning
-    if ((+static_cast<qint64>(value) <= INT_MAX) && (+static_cast<qint64>(value) >= INT_MIN)) {
+    if (losslessConvertToInt) {
         int intValue = static_cast<int>(value);
         QVariant intVar = intValue;
         QVERIFY(intVar.canConvert<Enum>());
@@ -4875,6 +4944,72 @@ template<typename Enum> void testVariant(Enum value, bool *ok)
     QVERIFY(QVariant(longValue).canConvert<Enum>());
     QCOMPARE(QVariant(longValue).value<Enum>(), value);
 
+    auto value2 = Enum(qToUnderlying(value) + 1);
+    var2 = QVariant::fromValue(value2);
+    QCOMPARE_EQ(var, var);
+    QCOMPARE_NE(var, var2);
+    QCOMPARE(QVariant::compare(var, var), QPartialOrdering::Equivalent);
+    QCOMPARE(QVariant::compare(var, var2), QPartialOrdering::Less);
+    QCOMPARE(QVariant::compare(var2, var), QPartialOrdering::Greater);
+
+    QCOMPARE_EQ(var, static_cast<qint64>(value));
+    QCOMPARE_EQ(var, static_cast<quint64>(value));
+    QCOMPARE_EQ(static_cast<qint64>(value), var);
+    QCOMPARE_EQ(static_cast<quint64>(value), var);
+    QCOMPARE_NE(var2, static_cast<qint64>(value));
+    QCOMPARE_NE(var2, static_cast<quint64>(value));
+    QCOMPARE_NE(static_cast<qint64>(value), var2);
+    QCOMPARE_NE(static_cast<quint64>(value), var2);
+
+    if (losslessConvertToInt) {
+        QCOMPARE_EQ(var, int(value));
+        QCOMPARE_EQ(int(value), var);
+        QCOMPARE_NE(var2, int(value));
+        QCOMPARE_NE(int(value), var2);
+    }
+    if (canLosslesslyConvert(uint{})) {
+        QCOMPARE_EQ(var, uint(value));
+        QCOMPARE_EQ(uint(value), var);
+        QCOMPARE_NE(var2, uint(value));
+        QCOMPARE_NE(uint(value), var2);
+    }
+    if (canLosslesslyConvert(short{})) {
+        QCOMPARE_EQ(var, short(value));
+        QCOMPARE_EQ(short(value), var);
+        QCOMPARE_NE(var2, short(value));
+        QCOMPARE_NE(short(value), var2);
+    }
+    if (canLosslesslyConvert(ushort{})) {
+        QCOMPARE_EQ(var, ushort(value));
+        QCOMPARE_EQ(ushort(value), var);
+        QCOMPARE_NE(var2, ushort(value));
+        QCOMPARE_NE(ushort(value), var2);
+    }
+    if (canLosslesslyConvert(char{})) {
+        QCOMPARE_EQ(var, char(value));
+        QCOMPARE_EQ(char(value), var);
+        QCOMPARE_NE(var2, char(value));
+        QCOMPARE_NE(char(value), var2);
+    }
+    if (canLosslesslyConvert(uchar{})) {
+        QCOMPARE_EQ(var, uchar(value));
+        QCOMPARE_EQ(uchar(value), var);
+        QCOMPARE_NE(var2, uchar(value));
+        QCOMPARE_NE(uchar(value), var2);
+    }
+    if (canLosslesslyConvert(qint8{})) {
+        QCOMPARE_EQ(var, qint8(value));
+        QCOMPARE_EQ(qint8(value), var);
+        QCOMPARE_NE(var2, qint8(value));
+        QCOMPARE_NE(qint8(value), var2);
+    }
+
+    // string compares too (of the values in decimal)
+    QCOMPARE_EQ(var, QString::number(qToUnderlying(value)));
+    QCOMPARE_EQ(QString::number(qToUnderlying(value)), var);
+    QCOMPARE_NE(var, QString::number(qToUnderlying(value2)));
+    QCOMPARE_NE(QString::number(qToUnderlying(value2)), var);
+
     *ok = true;
 }