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diff --git a/src/Reflection/RewriterInterp.v b/src/Reflection/RewriterInterp.v
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+Require Import Crypto.Reflection.Syntax.
+Require Import Crypto.Reflection.Rewriter.
+Require Import Crypto.Util.Tactics.RewriteHyp.
+
+Section language.
+  Context {base_type_code : Type}
+          {interp_base_type : base_type_code -> Type}
+          {op : flat_type base_type_code -> flat_type base_type_code -> Type}
+          {interp_op : forall src dst, op src dst -> interp_flat_type interp_base_type src -> interp_flat_type interp_base_type dst}.
+
+  Local Notation flat_type := (flat_type base_type_code).
+  Local Notation type := (type base_type_code).
+  Local Notation interp_type := (interp_type interp_base_type).
+  Local Notation interp_flat_type := (interp_flat_type interp_base_type).
+  Local Notation exprf := (@exprf base_type_code op interp_base_type).
+  Local Notation expr := (@expr base_type_code op interp_base_type).
+  Local Notation Expr := (@Expr base_type_code op).
+
+  Section specialized.
+    Context {rewrite_op_expr : forall src dst (opc : op src dst), exprf src -> exprf dst}
+            (Hrewrite : forall src dst opc args,
+                interpf interp_op (rewrite_op_expr src dst opc args)
+                = interp_op _ _ opc (interpf interp_op args)).
+
+    Lemma interpf_rewrite_opf {t} (e : exprf t)
+      : interpf interp_op (rewrite_opf rewrite_op_expr e) = interpf interp_op e.
+    Proof.
+      induction e; simpl; unfold LetIn.Let_In; rewrite_hyp ?*; reflexivity.
+    Qed.
+
+    Lemma interp_rewrite_op {t} (e : expr t)
+      : forall x, interp interp_op (rewrite_op rewrite_op_expr e) x = interp interp_op e x.
+    Proof.
+      destruct e; intro x; apply interpf_rewrite_opf.
+    Qed.
+  End specialized.
+
+  Lemma InterpRewriteOp
+        {rewrite_op_expr}
+        (Hrewrite : forall src dst opc args,
+            interpf interp_op (rewrite_op_expr interp_base_type src dst opc args)
+            = interp_op _ _ opc (interpf interp_op args))
+        {t} (e : Expr t)
+    : forall x, Interp interp_op (RewriteOp rewrite_op_expr e) x = Interp interp_op e x.
+  Proof.
+    apply interp_rewrite_op; assumption.
+  Qed.
+End language.