[qmltc] Compilation errors when building a QML component with aliased attached property

import QtQuick
import QtQuick.Templates as T

T.Popup {
    T.Overlay.modal: Rectangle {
        color: 'grey'
    }
}

...
    QQuickOverlayAttached * m_T.Overlay = nullptr;
...

.qmltc\test\mypopup.h(123): error C3551: if a trailing return type is used then the leading return type shall be the single type-specifier 'auto' (not 'overloaded function type')
.qmltc\test\mypopup.h(123): error C3484: syntax error: expected '->' before the return type
.qmltc\test\mypopup.h(123): error C3613: missing return type after '->' ('int' assumed)
.qmltc\test\mypopup.h(123): error C3646: 'Overlay': unknown override specifier