remove option from Econst string option

There is no case that leads to None

src/mlw/rust_printer.ml

@@ -43,7 +43,7 @@ module Rust = struct
   type fn = rsymbol * var list * ty * expr * Stv.t * Slt.t
 
   and expr =
-    | Econst of string option * BigInt.t
+    | Econst of string * BigInt.t
     | Evar of ident
     | Efield of expr * ident
     | Eassign of pvsymbol * rsymbol * expr
@@ -322,8 +322,7 @@ module Translate = struct
           | I { ity_node = Ityapp ({its_ts = ts},_,_) } -> ts.ts_name
           | _ -> assert false in
         (match query_syntax info.literal id with
-          | Some s -> Rust.Econst (Some s, n)
-          (* TODO there can never be an Econst (None, ..), the option is not needed *)
+          | Some s -> Rust.Econst (s, n)
           | None -> raise (MissingSyntaxLiteral id.id_string))
           (* there is no default, driver must make a decision about how to represent
           literals *)
@@ -949,10 +948,7 @@ module Print = struct
 
   let rec print_expr info fmt (e:expr) =
     match e with
-    | Econst (s_opt, n) ->
-        (match s_opt with
-        | Some s -> syntax_arguments s print_constant fmt [n]
-        | None -> raise (TODO "const no syntax"))
+    | Econst (s, n) -> syntax_arguments s print_constant fmt [n]
     | Evar id -> print_lident info fmt id
     | Efield (e, id) ->
         fprintf fmt "%a.%a" (print_expr info) e (print_lident info) id