+val rewritingstep :
+ dbd:HSql.dbd -> universe:Universe.universe ->
+ (string option * Cic.term) option -> Cic.term ->
+ [ `Term of Cic.term | `Auto of Auto.auto_params
+ | `Proof | `SolveWith of Cic.term] ->
+ bool (* last step *) -> ProofEngineTypes.tactic