The QtDeclarative code causing QTBUG-131906 hits UB, because it tries to store -666 in an enum {A, B}, which has a valid range of [0,1], therefore its underlying_type is uint, yet, as per [conv.prom]/3¹, integer-promotes to _int_ instead, so in Qt 6.8 would cause the arg(int) overload to be called, outputting -666, while in Qt 6.9, it's treated (correctly) as an unsigned value, outputting -666's two's complement, a positive value. Add a version of the scenario that does not cause UB. ¹ Thanks to Ahmad Samir for digging up the pertinent legalese. Task-number: QTBUG-131906 Pick-to: 6.9 6.8 6.5 Change-Id: Iba1a04de523a0b4cd1c87deea40c643cf16df14f Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>