Function collect_local_origins 

pub fn collect_local_origins<'tcx>(
    tcx: TyCtxt<'tcx>,
    def_id: DefId,
) -> LocalOriginMap

Build a lightweight intra-procedural origin map by scanning MIR assignments. For each local = rvalue, records the source place if the rvalue is a simple copy / move / cast / ref / raw-ptr / copy-for-deref.