There is a qmlsc warning produced when trying to make an arg call on qStr.
This will result in the following warning
Warning: main.qml:7:29: Property "arg" not found on type "void"
title: qsTr("Hello %1").arg("World")
It is suspected that type info for qsTr does not say it returns a string, as someone should be able to call arg() on it. It should be noted that this appears to only occur on linux, could not re-produce this warning on windows.