Function maybe_drop_guard 

fn maybe_drop_guard<'tcx>(
    tcx: TyCtxt<'tcx>,
    typing_env: TypingEnv<'tcx>,
    index: PlaceIndex,
    ever_dropped: &DenseBitSet<PlaceIndex>,
    checked_places: &PlaceSet<'tcx>,
    body: &Body<'tcx>,
) -> bool

Return whether we should consider the current place as a drop guard and skip reporting.