Improve error message when setting to a property with unknown type

At the moment we were being told that the types were incompatible but
the truth was we were comparing to nullptr.
This patch makes it apparent that the assigning broke because the type
comparison never happened.

Change-Id: I29728eedeee13c3bc9389213735df142f56e9c34
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 11 insertions, 7 deletions

diff --git a/src/qml/qml/qqmlpropertyvalidator.cpp b/src/qml/qml/qqmlpropertyvalidator.cpp
index 71964aca64..7dbcbe986b 100644
--- a/src/qml/qml/qqmlpropertyvalidator.cpp
+++ b/src/qml/qml/qqmlpropertyvalidator.cpp
@@ -711,21 +711,25 @@ QQmlJS::DiagnosticMessage QQmlPropertyValidator::validateObjectBinding(QQmlPrope
         // Using -1 for the minor version ensures that we get the raw metaObject.
         QQmlPropertyCache *propertyMetaObject = enginePrivate->rawPropertyCacheForType(property->propType(), -1);
 
-        // Will be true if the assigned type inherits propertyMetaObject
-        bool isAssignable = false;
-        // Determine isAssignable value
         if (propertyMetaObject) {
+            // Will be true if the assigned type inherits propertyMetaObject
+            // Determine isAssignable value
+            bool isAssignable = false;
             QQmlPropertyCache *c = propertyCaches.at(binding->value.objectIndex);
             while (c && !isAssignable) {
                 isAssignable |= c == propertyMetaObject;
                 c = c->parent();
             }
-        }
 
-        if (!isAssignable) {
-            return qQmlCompileError(binding->valueLocation, tr("Cannot assign object of type \"%1\" to property of type \"%2\" as the former is neither the same as the latter nor a sub-class of it.")
-                    .arg(stringAt(compilationUnit->objectAt(binding->value.objectIndex)->inheritedTypeNameIndex)).arg(QLatin1String(QMetaType::typeName(property->propType()))));
+            if (!isAssignable) {
+                return qQmlCompileError(binding->valueLocation, tr("Cannot assign object of type \"%1\" to property of type \"%2\" as the former is neither the same as the latter nor a sub-class of it.")
+                        .arg(stringAt(compilationUnit->objectAt(binding->value.objectIndex)->inheritedTypeNameIndex)).arg(QLatin1String(QMetaType::typeName(property->propType()))));
+            }
+        } else {
+            return qQmlCompileError(binding->valueLocation, tr("Cannot assign to property of unknown type \"%1\".")
+                        .arg(QLatin1String(QMetaType::typeName(property->propType()))));
         }
+
     }
     return noError;
 }