fix printing of 1-tuples

src/mlw/rust_printer.ml

@@ -772,6 +772,9 @@ module Print = struct
     | Eassign (rho, rs, pv) ->
         fprintf fmt "%a.%a = %a" (print_lident info) (pv_name rho)
         (print_lident info) rs.rs_name (print_lident info) (pv_name pv)
+    | Etup [e] ->
+        (* 1-tuples don't exist in whyml, so this is not strictly needed *)
+        fprintf fmt "(%a,)" (print_expr info) e
     | Etup el -> fprintf fmt "(%a)" (print_list comma (print_expr info)) el
     | Eenum (rs, []) -> print_uident info fmt rs.rs_name
     | Eenum (rs, el) ->