Revert "Small improvement to layout inference for mutually recursive type decl parameters (#1766)"

This reverts commit be17ee2.

Author: goldfirere

ocaml/typing/typedecl.ml

@@ -1548,8 +1548,6 @@ let transl_type_decl env rec_flag sdecl_list =
         raise (Error (loc, Type_clash (new_env, err))))
       checks)
     delayed_jkind_checks;
-  (* Check that constraints are enforced *)
-  List.iter2 (check_constraints new_env) sdecl_list decls;
   (* Check that all type variables are closed; this also defaults any remaining
      sort variables. Defaulting must happen before update_decls_jkind,
      Typedecl_seperability.update_decls, and add_types_to_env, all of which need
@@ -1563,6 +1561,8 @@ let transl_type_decl env rec_flag sdecl_list =
          Some ty -> raise(Error(sdecl.ptype_loc, Unbound_type_var(ty,decl)))
        | None   -> ())
     sdecl_list tdecls;
+  (* Check that constraints are enforced *)
+  List.iter2 (check_constraints new_env) sdecl_list decls;
   (* Add type properties to declarations *)
   let decls =
     try