QML: Add a pragma for value type behavior

Unfortunately value types behave differently when compiled to C++.
Document the difference and introduce a pragma to make them behave one
way or the other.

Pick-to: 6.5
Fixes: QTBUG-109221
Change-Id: Ib2685153c0b4ae209bafbea7a01229377fdb47dd
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlirloader.cpp b/src/qml/qml/qqmlirloader.cpp
index c80f9b4bd1..5137c4c1ab 100644
--- a/src/qml/qml/qqmlirloader.cpp
+++ b/src/qml/qml/qqmlirloader.cpp
@@ -55,6 +55,12 @@ void QQmlIRLoader::load()
         createPragma(type)->nativeMethodBehavior = value;
     };
 
+    const auto createValueTypePragma = [&](
+            Pragma::PragmaType type,
+            Pragma::ValueTypeBehaviorValue value) {
+        createPragma(type)->valueTypeBehavior = value;
+    };
+
     if (unit->flags & QV4::CompiledData::Unit::IsSingleton)
         createPragma(Pragma::Singleton);
     if (unit->flags & QV4::CompiledData::Unit::IsStrict)
@@ -74,6 +80,9 @@ void QQmlIRLoader::load()
     if (unit->flags & QV4::CompiledData::Unit::NativeMethodsAcceptThisObject)
         createNativeMethodPragma(Pragma::NativeMethodBehavior, Pragma::AcceptThisObject);
 
+    if (unit->flags & QV4::CompiledData::Unit::ValueTypesCopied)
+        createValueTypePragma(Pragma::ValueTypeBehavior, Pragma::Copy);
+
     for (uint i = 0; i < qmlUnit->nObjects; ++i) {
         const QV4::CompiledData::Object *serializedObject = qmlUnit->objectAt(i);
         QmlIR::Object *object = loadObject(serializedObject);