pivot_at reverses order of the traversed list. This can cause issues when reconstructing the match so we undo.

Author: Cameron-Low

src/ecMatching.ml

@@ -230,6 +230,7 @@ module Zipper = struct
             with Not_found -> raise InvalidCPos
           in
           let prebr, (locals, body), postbr = List.pivot_at ix bs in
+          let prebr = List.rev prebr in
           let env = EcEnv.Var.bind_locals locals env in
           (ZMatch (e, ((s1, s2), zpr), { locals; prebr; postbr; }), body), env