Ocaml interpreter

AST
type expr =
| EInt of int
| EBool of bool
| Var of string
| Let of string * expr * expr | Prim of string * expr * expr | If of expr * expr * expr
| Fun of string * expr
| Call of expr * expr
| GetInput of expr

type value =
| Int of int
| Bool of bool
| Closure of string * expr * value env

Environment:

(* environment )
type 'v env = (string * 'v * bool) list
(
binding )
let rec lookup env x =
match env with
| [] → failwith (x ^ “not found”)
| (y, v, _) :: r → if x = y then v else lookup r x
(
taintness of a variable *) let rec t_lookup env x =
match env with
| → failwith (x ^ “not found”)
| (y, _, t) :: r → if x = y then t else t_lookup r x

Interpreter
let rec eval (e : expr) (env:value env) (t : bool) : value * bool = match e with
| EInt n → (Int n, t)
| EBool b → (Bool b, t)
| Var x → (lookup env x, t_lookup env x) | Prim (op, e1, e2) →
begin
let v1, t1 = eval e1 env t in let v2, t2 = eval e2 env t in
match (op, v1, v2) with
(* taintness of binary ops is given by the OR of the taintness of the args ) | "", Int i1, Int i2 → (Int (i1 * i2), t1 || t2)
| “+”, Int i1, Int i2 → (Int (i1 + i2), t1 || t2)
| “-”, Int i1, Int i2 → (Int (i1 - i2), t1 || t2)
| “=”, Int i1, Int i2 → (Bool (if i1 = i2 then true else false), t1 || t2)
| “<”, Int i1, Int i2 → (Bool (if i1 < i2 then true else false), t1 || t2)
| “>”, Int i1, Int i2 → (Bool (if i1 > i2 then true else false), t1 || t2)
| _, _, _ → failwith “Unexpected primitive.”
end

| If (e1, e2, e3) → begin
let v1, t1 = eval e1 env t in match v1 with
| Bool true → let v2, t2 = eval e2 env t in (v2, t1 || t2) | Bool false → let v3, t3 = eval e3 env t in (v3, t1 || t3) | _ → failwith “Unexpected condition.”
end

| Fun (f_param, f_body) → (Closure (f_param, f_body, env), t) | Call (f, param) →
let f_closure, f_t = eval f env t in begin
match f_closure with
| Closure (f_param, f_body, f_dec_env) →
let f_param_val, f_param_t = eval param env t in
let env’ = (f_param, f_param_val, f_param_t)::f_dec_env in
let f_res, t_res = eval f_body env’ t in (f_res, f_t || f_param_t || t_res)
| _ → failwith “Function expected error” end
| GetInput(e) → eval e env true

In the eval of the Call in the Interpreter there is a error, what is? Can you fix it?