Function rustc_mir_transform::separate_const_switch::find_determining_place

fn find_determining_place<'tcx>(
    switch_place: Place<'tcx>,
    block: &BasicBlockData<'tcx>
) -> Option<Place<'tcx>>

Finds a unique place that entirely determines the value of switch_place, if it exists. This is only a heuristic. Ideally we would like to track multiple determining places for some edge cases, but one is enough for a lot of situations.