QMetaProperty: limit QMetaEnum resolution to enums known to QMetaType

Since we don't know ahead of time if a property's type is an enum
or a flag we have to resolve it at runtime.

In a QMetaProperty-heavy application this overhead can be quite dramatic
given that we mark anything that is not a built-in as a potential
flag/enum.

However, QMetaType already knows if it's an enum, so we can use that to
return early if it's not known to the meta-type system.
To add to this - Q_PROPERTY requires that a type is fully defined, so
there are no issues with forward declarations for the enums.

Change-Id: Ifecc7f1e6cdef416e3ce72ee705eb26e682071cc
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/corelib/kernel/qmetaobject.cpp b/src/corelib/kernel/qmetaobject.cpp
index 148983f126..05662b385a 100644
--- a/src/corelib/kernel/qmetaobject.cpp
+++ b/src/corelib/kernel/qmetaobject.cpp
@@ -3656,8 +3656,8 @@ QMetaProperty::QMetaProperty(const QMetaObject *mobj, int index)
       data(getMetaPropertyData(mobj, index))
 {
     Q_ASSERT(index >= 0 && index < priv(mobj->d.data)->propertyCount);
-
-    if (!(data.flags() & EnumOrFlag))
+    // The code below here just resolves menum if the property is an enum type:
+    if (!(data.flags() & EnumOrFlag) || !metaType().flags().testFlag(QMetaType::IsEnumeration))
         return;
     QByteArrayView enum_name = typeNameFromTypeInfo(mobj, data.type());
     menum = mobj->enumerator(QMetaObjectPrivate::indexOfEnumerator(mobj, enum_name));