QmlCompiler: Don't try to get attached objects for non-QObject*

We might end up in this situation if we don't know enough about the
base of the attached lookup. This would generate invalid C++ code.

Pick-to: 6.2 6.3
Change-Id: I210077388d0d1d0d4e9454bd3ba3792af9b42049
Reviewed-by: Maximilian Goldstein <max.goldstein@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 11 insertions, 4 deletions

diff --git a/src/qmlcompiler/qqmljscodegenerator.cpp b/src/qmlcompiler/qqmljscodegenerator.cpp
index a3cd7cdd91..30d6bc42fb 100644
--- a/src/qmlcompiler/qqmljscodegenerator.cpp
+++ b/src/qmlcompiler/qqmljscodegenerator.cpp
@@ -971,7 +971,18 @@ void QQmlJSCodeGenerator::generate_GetLookup(int index)
     const QString namespaceString = m_state.accumulatorIn.isImportNamespace()
             ? QString::number(m_state.accumulatorIn.importNamespace())
             : u"QQmlPrivate::AOTCompiledContext::InvalidStringId"_qs;
+    const auto storedType = m_state.accumulatorIn.storedType();
+    const bool isReferenceType
+            = (storedType->accessSemantics() == QQmlJSScope::AccessSemantics::Reference);
     if (m_state.accumulatorOut.variant() == QQmlJSRegisterContent::ObjectAttached) {
+        if (!isReferenceType) {
+            // This can happen on incomplete type information. We contextually know that the
+            // type must be a QObject, but we cannot construct the inheritance chain. Then we
+            // store it in a generic type. Technically we could even convert it to QObject*, but
+            // that would be expensive.
+            reject(u"attached object for non-QObject type"_qs);
+        }
+
         const QString lookup = u"aotContext->loadAttachedLookup("_qs + indexString
                 + u", "_qs + use(m_state.accumulatorVariableIn)
                 + u", &"_qs + m_state.accumulatorVariableOut + u')';
@@ -991,10 +1002,6 @@ void QQmlJSCodeGenerator::generate_GetLookup(int index)
 
     Q_ASSERT(m_state.accumulatorOut.isProperty());
 
-    const auto storedType = m_state.accumulatorIn.storedType();
-    const bool isReferenceType
-            = (storedType->accessSemantics() == QQmlJSScope::AccessSemantics::Reference);
-
     const QQmlJSScope::ConstPtr out = m_state.accumulatorOut.storedType();
     if (isReferenceType) {
         m_body += u"{\n"_qs;