Rewriter.Rule
type 'a t
val identity : 'a Flambda2_types.Rewriter.Rule.t
val rewrite : 'a Flambda2_types.Rewriter.Pattern.t -> Flambda2_types.Rewriter.Var.t Flambda2_types.Rewriter.expr -> 'a Flambda2_types.Rewriter.Rule.t