path: root/src/monomorphise_new.ml

open Parse_ast
open Ast
open Ast_util
open Type_check_new

let disable_const_propagation = ref false

(* TODO: some places will need Type_check_new.expand_synonyms *)

(* TODO: put this somewhere common *)

let id_to_string (Id_aux(id,l)) =
  match id with
    | Id(s) -> s
    | DeIid(s) -> s

(* TODO: check for temporary failwiths *)

let optmap v f =
  match v with
  | None -> None
  | Some v -> Some (f v)

module KSubst = Map.Make(Kid)
module ISubst = Map.Make(Id)
let ksubst_from_list = List.fold_left (fun s (v,i) -> KSubst.add v i s) KSubst.empty
let isubst_from_list = List.fold_left (fun s (v,i) -> ISubst.add v i s) ISubst.empty

let subst_src_typ substs t =
  let rec s_snexp (Nexp_aux (ne,l) as nexp) =
    let re ne = Nexp_aux (ne,l) in
    match ne with
    | Nexp_var (Kid_aux (_,l) as kid) ->
       (try KSubst.find kid substs
       with Not_found -> nexp)
    | Nexp_id _
    | Nexp_constant _ -> nexp
    | Nexp_times (n1,n2) -> re (Nexp_times (s_snexp n1, s_snexp n2))
    | Nexp_sum (n1,n2)   -> re (Nexp_sum   (s_snexp n1, s_snexp n2))
    | Nexp_minus (n1,n2) -> re (Nexp_minus (s_snexp n1, s_snexp n2))
    | Nexp_exp ne -> re (Nexp_exp (s_snexp ne))
    | Nexp_neg ne -> re (Nexp_neg (s_snexp ne))
  in
  let rec s_styp ((Typ_aux (t,l)) as ty) =
    let re t = Typ_aux (t,l) in
    match t with
    | Typ_wild
    | Typ_id _
    | Typ_var _
      -> ty
    | Typ_fn (t1,t2,e) -> re (Typ_fn (s_styp t1, s_styp t2,e))
    | Typ_tup ts -> re (Typ_tup (List.map s_styp ts))
    | Typ_app (id,tas) -> re (Typ_app (id,List.map s_starg tas))
  and s_starg (Typ_arg_aux (ta,l) as targ) =
    match ta with
    | Typ_arg_nexp ne -> Typ_arg_aux (Typ_arg_nexp (s_snexp ne),l)
    | Typ_arg_typ t -> Typ_arg_aux (Typ_arg_typ (s_styp t),l)
    | Typ_arg_order _
    | Typ_arg_effect _ -> targ
  in s_styp t




(* Based on current type checker's behaviour *)
let pat_id_is_variable env id =
  match Env.lookup_id id env with
  | Register _
  | Local _
    -> true
  | Enum _
  | Union _
    -> false
  | Unbound -> failwith "unbound var"

let rec is_value (E_aux (e,(l,annot))) =
  match e with
  | E_id id ->
     (match annot with
     | None -> false (* Be conservative if we have no info *)
     | Some (env,_,_) -> not (pat_id_is_variable env id))
  | E_lit _ -> true
  | E_tuple es -> List.for_all is_value es
(* TODO: more? *)
  | _ -> false

let is_pure (Effect_opt_aux (e,_)) =
  match e with
  | Effect_opt_pure -> true
  | Effect_opt_effect (Effect_aux (Effect_set [],_)) -> true
  | _ -> false

let rec list_extract f = function
  | [] -> None
  | h::t -> match f h with None -> list_extract f t | Some v -> Some v

let rec cross = function
  | [] -> failwith "cross"
  | [(x,l)] -> List.map (fun y -> [(x,y)]) l
  | (x,l)::t -> 
     let t' = cross t in
     List.concat (List.map (fun y -> List.map (fun l' -> (x,y)::l') t') l)

(* Given a type for a constructor, work out which refinements we ought to produce *)
(* TODO collision avoidance *)
let split_src_type i ty (TypQ_aux (q,ql)) =
  let rec size_nvars_nexp (Nexp_aux (ne,_)) =
    match ne with
    | Nexp_var v -> [v]
    | Nexp_id _
    | Nexp_constant _
      -> []
    | Nexp_times (n1,n2)
    | Nexp_sum (n1,n2)
    | Nexp_minus (n1,n2)
      -> size_nvars_nexp n1 @ size_nvars_nexp n2
    | Nexp_exp n
    | Nexp_neg n
      -> size_nvars_nexp n
  in
  let rec size_nvars_ty (Typ_aux (ty,l)) =
    match ty with
    | Typ_wild
    | Typ_id _
    | Typ_var _
      -> []
    | Typ_fn _ ->
       raise (Reporting_basic.err_general l ("Function type in constructor " ^ i))
    | Typ_tup ts -> List.concat (List.map size_nvars_ty ts)
    | Typ_app (Id_aux (Id "vector",_),
               [_;Typ_arg_aux (Typ_arg_nexp sz,_);
                _;Typ_arg_aux (Typ_arg_typ (Typ_aux (Typ_id (Id_aux (Id "bit",_)),_)),_)]) ->
       size_nvars_nexp sz
    | Typ_app (_, tas) ->
       []  (* We only support sizes for bitvectors mentioned explicitly, not any buried
              inside another type *)
  in
  let nvars = List.sort_uniq Kid.compare (size_nvars_ty ty) in
  match nvars with
  | [] -> None
  | sample::__ ->
     (* Only check for constraints if we found a size to constrain *)
     let qs =
       match q with
       | TypQ_no_forall -> 
          raise (Reporting_basic.err_general ql
                   ("No set constraint for variable " ^ string_of_kid sample ^ " in constructor " ^ i))
       | TypQ_tq qs -> qs
     in
     let find_set (Kid_aux (Var nvar,_) as kid) =
       match list_extract (function
       | QI_aux (QI_const (NC_aux (NC_nat_set_bounded (Kid_aux (Var nvar',_),vals),_)),_)
         -> if nvar = nvar' then Some vals else None
       | _ -> None) qs with
       | None ->
          raise (Reporting_basic.err_general ql
                   ("No set constraint for variable " ^ nvar ^ " in constructor " ^ i))
       | Some vals -> (kid,vals)
     in
     let nvar_sets = List.map find_set nvars in
     let total_variants = List.fold_left ( * ) 1 (List.map (fun (_,l) -> List.length l) nvar_sets) in
     let limit = 8 in
     let () = if total_variants > limit then
         raise (Reporting_basic.err_general ql
                  (string_of_int total_variants ^ "variants for constructor " ^ i ^
                     "bigger than limit " ^ string_of_int limit)) else ()
     in
     let variants = cross nvar_sets in
     let name l = String.concat "_" (i::(List.map (fun (v,i) -> string_of_kid v ^ string_of_int i) l)) in
     Some (List.map (fun l -> (l, name l)) variants)

(* TODO: maybe fold this into subst_src_typ? *)
let inst_src_type insts ty =
  let insts = List.map (fun (v,i) -> (v,Nexp_aux (Nexp_constant i,Generated Unknown))) insts in
  let subst = ksubst_from_list insts in
  subst_src_typ subst ty

let reduce_nexp subst ne =
  let rec eval (Nexp_aux (ne,_) as nexp) =
    match ne with
    | Nexp_constant i -> i
    | Nexp_sum (n1,n2) -> (eval n1) + (eval n2)
    | Nexp_minus (n1,n2) -> (eval n1) - (eval n2)
    | Nexp_times (n1,n2) -> (eval n1) * (eval n2)
    | Nexp_exp n -> 1 lsl (eval n)
    | Nexp_neg n -> - (eval n)
    | _ ->
       raise (Reporting_basic.err_general Unknown ("Couldn't turn nexp " ^
                                                      string_of_nexp nexp ^ " into concrete value"))
  in eval ne

(* Check to see if we need to monomorphise a use of a constructor.  Currently
   assumes that bitvector sizes are always given as a variable; don't yet handle
   more general cases (e.g., 8 * var) *)

(* TODO: use type checker's instantiation instead *)
let refine_constructor refinements i substs (E_aux (_,(l,_)) as arg) t =
  let rec derive_vars (Typ_aux (t,_)) (E_aux (e,(l,tannot))) =
    match t with
    | Typ_app (Id_aux (Id "vector",_), [_;Typ_arg_aux (Typ_arg_nexp (Nexp_aux (Nexp_var v,_)),_);_;Typ_arg_aux (Typ_arg_typ (Typ_aux (Typ_id (Id_aux (Id "bit",_)),_)),_)]) ->
       (match tannot with
       | Some (_,Typ_aux (Typ_app (Id_aux (Id "vector",_), [_;Typ_arg_aux (Typ_arg_nexp ne,_);_;Typ_arg_aux (Typ_arg_typ (Typ_aux (Typ_id (Id_aux (Id "bit",_)),_)),_)]),_),_) ->
          [(v,reduce_nexp substs ne)]
       | _ -> [])
    | Typ_wild
    | Typ_var _
    | Typ_id _
    | Typ_fn _
    | Typ_app _
      -> []
    | Typ_tup ts ->
       match e with
       | E_tuple es -> List.concat (List.map2 derive_vars ts es)
       | _ -> [] (* TODO? *)
  in
  try
    let irefinements = List.assoc i refinements in
    let vars = List.sort_uniq (fun x y -> Kid.compare (fst x) (fst y)) (derive_vars t arg) in
    try
      Some (List.assoc vars irefinements)
    with Not_found ->
      (Reporting_basic.print_err false true l "Monomorphisation"
         ("Failed to find a monomorphic constructor for " ^ i ^ " instance " ^
             match vars with [] -> "<empty>"
             | _ -> String.concat "," (List.map (fun (x,y) -> string_of_kid x ^ "=" ^ string_of_int y) vars)); None)
  with Not_found -> None


(* Substitute found nexps for variables in an expression, and rename constructors to reflect
   specialisation *)

let nexp_subst_fns substs refinements =
(*
  let s_t t = typ_subst substs true t in
(*  let s_typschm (TypSchm_aux (TypSchm_ts (q,t),l)) = TypSchm_aux (TypSchm_ts (q,s_t t),l) in
   hopefully don't need this anyway *)
  let s_typschm tsh = tsh in
  let s_tannot = function
    | Base ((params,t),tag,ranges,effl,effc,bounds) ->
       (* TODO: do other fields need mapped? *)
       Base ((params,s_t t),tag,ranges,effl,effc,bounds)
    | tannot -> tannot
  in
  let rec s_pat (P_aux (p,(l,annot))) =
    let re p = P_aux (p,(l,s_tannot annot)) in
    match p with
    | P_lit _ | P_wild | P_id _ -> re p
    | P_as (p',id) -> re (P_as (s_pat p', id))
    | P_typ (ty,p') -> re (P_typ (ty,s_pat p'))
    | P_app (id,ps) -> re (P_app (id, List.map s_pat ps))
    | P_record (fps,flag) -> re (P_record (List.map s_fpat fps, flag))
    | P_vector ps -> re (P_vector (List.map s_pat ps))
    | P_vector_indexed ips -> re (P_vector_indexed (List.map (fun (i,p) -> (i,s_pat p)) ips))
    | P_vector_concat ps -> re (P_vector_concat (List.map s_pat ps))
    | P_tup ps -> re (P_tup (List.map s_pat ps))
    | P_list ps -> re (P_list (List.map s_pat ps))
  and s_fpat (FP_aux (FP_Fpat (id, p), (l,annot))) =
    FP_aux (FP_Fpat (id, s_pat p), (l,s_tannot annot))
  in*)
  let rec s_exp (E_aux (e,(l,annot))) =
    let re e = E_aux (e,(l,(*s_tannot*) annot)) in
      match e with
      | E_block es -> re (E_block (List.map s_exp es))
      | E_nondet es -> re (E_nondet (List.map s_exp es))
      | E_id _
      | E_lit _
      | E_comment _ -> re e
      | E_sizeof ne -> re (E_sizeof ne) (* TODO: do this need done?  does it appear in type checked code? *)
      | E_internal_exp (l,annot) -> re (E_internal_exp (l, (*s_tannot*) annot))
      | E_sizeof_internal (l,annot) -> re (E_sizeof_internal (l, (*s_tannot*) annot))
      | E_internal_exp_user ((l1,annot1),(l2,annot2)) ->
         re (E_internal_exp_user ((l1, (*s_tannot*) annot1),(l2, (*s_tannot*) annot2)))
      | E_cast (t,e') -> re (E_cast (t, s_exp e'))
      | E_app (id,es) ->
         let es' = List.map s_exp es in
         let arg =
           match es' with
           | [] -> E_aux (E_lit (L_aux (L_unit,Unknown)),(l,None))
           | [e] -> e
           | _ -> E_aux (E_tuple es',(l,None))
         in
         let i = id_to_string id in
         let id' = 
           let env = match annot with Some (e,_,_) -> e | None -> failwith "env" in
           match Env.lookup_id id env with
           | Union (qs,Typ_aux (Typ_fn(inty,outty,_),_)) ->
              (match refine_constructor refinements i substs arg inty with
              | None -> id
              | Some i -> Id_aux (Id i,Generated l))
           | _ -> id
         in re (E_app (id',es'))
      | E_app_infix (e1,id,e2) -> re (E_app_infix (s_exp e1,id,s_exp e2))
      | E_tuple es -> re (E_tuple (List.map s_exp es))
      | E_if (e1,e2,e3) -> re (E_if (s_exp e1, s_exp e2, s_exp e3))
      | E_for (id,e1,e2,e3,ord,e4) -> re (E_for (id,s_exp e1,s_exp e2,s_exp e3,ord,s_exp e4))
      | E_vector es -> re (E_vector (List.map s_exp es))
      | E_vector_indexed (ies,ed) -> re (E_vector_indexed (List.map (fun (i,e) -> (i,s_exp e)) ies,
                                                           s_opt_default ed))
      | E_vector_access (e1,e2) -> re (E_vector_access (s_exp e1,s_exp e2))
      | E_vector_subrange (e1,e2,e3) -> re (E_vector_subrange (s_exp e1,s_exp e2,s_exp e3))
      | E_vector_update (e1,e2,e3) -> re (E_vector_update (s_exp e1,s_exp e2,s_exp e3))
      | E_vector_update_subrange (e1,e2,e3,e4) -> re (E_vector_update_subrange (s_exp e1,s_exp e2,s_exp e3,s_exp e4))
      | E_vector_append (e1,e2) -> re (E_vector_append (s_exp e1,s_exp e2))
      | E_list es -> re (E_list (List.map s_exp es))
      | E_cons (e1,e2) -> re (E_cons (s_exp e1,s_exp e2))
      | E_record fes -> re (E_record (s_fexps fes))
      | E_record_update (e,fes) -> re (E_record_update (s_exp e, s_fexps fes))
      | E_field (e,id) -> re (E_field (s_exp e,id))
      | E_case (e,cases) -> re (E_case (s_exp e, List.map s_pexp cases))
      | E_let (lb,e) -> re (E_let (s_letbind lb, s_exp e))
      | E_assign (le,e) -> re (E_assign (s_lexp le, s_exp e))
      | E_exit e -> re (E_exit (s_exp e))
      | E_return e -> re (E_return (s_exp e))
      | E_assert (e1,e2) -> re (E_assert (s_exp e1,s_exp e2))
      | E_internal_cast ((l,ann),e) -> re (E_internal_cast ((l,(*s_tannot*) ann),s_exp e))
      | E_comment_struc e -> re (E_comment_struc e)
      | E_internal_let (le,e1,e2) -> re (E_internal_let (s_lexp le, s_exp e1, s_exp e2))
      | E_internal_plet (p,e1,e2) -> re (E_internal_plet ((*s_pat*) p, s_exp e1, s_exp e2))
      | E_internal_return e -> re (E_internal_return (s_exp e))
    and s_opt_default (Def_val_aux (ed,(l,annot))) =
      match ed with
      | Def_val_empty -> Def_val_aux (Def_val_empty,(l,(*s_tannot*) annot))
      | Def_val_dec e -> Def_val_aux (Def_val_dec (s_exp e),(l,(*s_tannot*) annot))
    and s_fexps (FES_aux (FES_Fexps (fes,flag), (l,annot))) =
      FES_aux (FES_Fexps (List.map s_fexp fes, flag), (l,(*s_tannot*) annot))
    and s_fexp (FE_aux (FE_Fexp (id,e), (l,annot))) =
      FE_aux (FE_Fexp (id,s_exp e),(l,(*s_tannot*) annot))
    and s_pexp (Pat_aux (Pat_exp (p,e),(l,annot))) =
      Pat_aux (Pat_exp ((*s_pat*) p, s_exp e),(l,(*s_tannot*) annot))
    and s_letbind (LB_aux (lb,(l,annot))) =
      match lb with
      | LB_val_explicit (tysch,p,e) ->
         LB_aux (LB_val_explicit ((*s_typschm*) tysch,(*s_pat*) p,s_exp e), (l,(*s_tannot*) annot))
      | LB_val_implicit (p,e) -> LB_aux (LB_val_implicit ((*s_pat*) p,s_exp e), (l,(*s_tannot*) annot))
    and s_lexp (LEXP_aux (e,(l,annot))) =
      let re e = LEXP_aux (e,(l,(*s_tannot*) annot)) in
      match e with
      | LEXP_id _
      | LEXP_cast _
        -> re e
      | LEXP_memory (id,es) -> re (LEXP_memory (id,List.map s_exp es))
      | LEXP_tup les -> re (LEXP_tup (List.map s_lexp les))
      | LEXP_vector (le,e) -> re (LEXP_vector (s_lexp le, s_exp e))
      | LEXP_vector_range (le,e1,e2) -> re (LEXP_vector_range (s_lexp le, s_exp e1, s_exp e2))
      | LEXP_field (le,id) -> re (LEXP_field (s_lexp le, id))
  in ((fun x -> x (*s_pat*)),s_exp)
let nexp_subst_pat substs refinements = fst (nexp_subst_fns substs refinements)
let nexp_subst_exp substs refinements = snd (nexp_subst_fns substs refinements)

let bindings_from_pat p =
  let rec aux_pat (P_aux (p,(l,annot))) =
    let env = match annot with Some (e,_,_) -> e | None -> failwith "env" in
    match p with
    | P_lit _
    | P_wild
      -> []
    | P_as (p,id) -> id::(aux_pat p)
    | P_typ (_,p) -> aux_pat p
    | P_id id ->
       if pat_id_is_variable env id then [id] else []
    | P_vector ps
    | P_vector_concat ps
    | P_app (_,ps)
    | P_tup ps
    | P_list ps
      -> List.concat (List.map aux_pat ps)
    | P_record (fps,_) -> List.concat (List.map aux_fpat fps)
    | P_vector_indexed ips -> List.concat (List.map (fun (_,p) -> aux_pat p) ips)
  and aux_fpat (FP_aux (FP_Fpat (_,p), _)) = aux_pat p
  in aux_pat p

let remove_bound env pat =
  let bound = bindings_from_pat pat in
  List.fold_left (fun sub v -> ISubst.remove v env) env bound

(* We may need to split up a pattern match if (1) we've been told to case split
   on a variable by the user, or (2) we monomorphised a constructor that's used
   in the pattern. *)
type split =
  | NoSplit
  | VarSplit of (tannot pat * (id * tannot Ast.exp)) list
  | ConstrSplit of (tannot pat * nexp KSubst.t) list

let split_defs splits (Type_check.Env (d_env,t_env,b_env,tp_env)) defs =
  let split_constructors (Defs defs) =
    let sc_type_union q (Tu_aux (tu,l) as tua) =
      match tu with
      | Tu_id id -> [],[tua]
      | Tu_ty_id (ty,id) ->
         let i = id_to_string id in
         (match split_src_type i ty q with
         | None -> ([],[Tu_aux (Tu_ty_id (ty,id),l)])
         | Some variants ->
            ([(i,variants)],
             List.map (fun (insts, i') -> Tu_aux (Tu_ty_id (inst_src_type insts ty,Id_aux (Id i',Generated l)),Generated l)) variants))
    in
    let sc_type_def ((TD_aux (tda,annot)) as td) =
      match tda with
      | TD_variant (id,nscm,quant,tus,flag) ->
         let (refinements, tus') = List.split (List.map (sc_type_union quant) tus) in
         (List.concat refinements, TD_aux (TD_variant (id,nscm,quant,List.concat tus',flag),annot))
      | _ -> ([],td)
    in
    let sc_def d =
      match d with
    | DEF_type td -> let (refinements,td') = sc_type_def td in (refinements, DEF_type td')
    | _ -> ([], d)
    in
    let (refinements, defs') = List.split (List.map sc_def defs)
    in (List.concat refinements, Defs defs')
  in

  let (refinements, defs') = split_constructors defs in

  (* Attempt simple pattern matches *)
  let can_match (E_aux (e,(l,annot)) as exp0) cases =
    let (env,ty) = match annot with Some (env,ty,_) -> env,ty | None -> failwith "env" in
    match e with
    | E_id id ->
       let i = id_to_string id in
       (match Env.lookup_id id env with
       | Enum _ ->
          let rec findpat cases =
            match cases with
            | [] -> (Reporting_basic.print_err false true l "Monomorphisation"
                       ("Failed to find a case for " ^ i); None)
            | [Pat_aux (Pat_exp (P_aux (P_wild,_),exp),_)] -> Some (exp,[])
            | (Pat_aux (Pat_exp (P_aux (P_typ (_,p),_),exp),ann))::tl ->
               findpat ((Pat_aux (Pat_exp (p,exp),ann))::tl)
            | (Pat_aux (Pat_exp (P_aux (P_id id',_),exp),_))::tl
                when pat_id_is_variable env id' ->
               Some (exp, [(id', exp0)])
            | (Pat_aux (Pat_exp (P_aux (P_id id',_),exp),_))::tl
            | (Pat_aux (Pat_exp (P_aux (P_app (id',[]),_),exp),_))::tl ->
               if i = id_to_string id' then Some (exp,[]) else findpat tl
            | (Pat_aux (Pat_exp (P_aux (_,(l',_)),_),_))::_ ->
               (Reporting_basic.print_err false true l' "Monomorphisation"
                  "Unexpected kind of pattern for enumeration"; None)
          in findpat cases
       | _ -> None)
    (* TODO: could generalise Lit matching *)
    | E_lit (L_aux ((L_zero | L_one | L_true | L_false) as bit, _)) ->
       let rec findpat cases =
         match cases with
         | [] -> (Reporting_basic.print_err false true l "Monomorphisation"
                    ("Failed to find a case for bit"); None)
         | [Pat_aux (Pat_exp (P_aux (P_wild,_),exp),_)] -> Some (exp,[])
         | (Pat_aux (Pat_exp (P_aux (P_typ (_,p),_),exp),ann))::tl ->
            findpat ((Pat_aux (Pat_exp (p,exp),ann))::tl)
         | (Pat_aux (Pat_exp (P_aux (P_id id',_),exp),_))::tl
             when pat_id_is_variable env id' ->
            Some (exp, [(id', exp0)])
         | (Pat_aux (Pat_exp (P_aux (P_lit (L_aux (lit, _)),_),exp),_))::tl ->
            (match bit,lit with
            | (L_zero | L_false), (L_zero | L_false) -> Some (exp,[])
            | (L_one  | L_true ), (L_one  | L_true ) -> Some (exp,[])
            | _ -> findpat tl)
         | (Pat_aux (Pat_exp (P_aux (_,(l',_)),_),_))::_ ->
            (Reporting_basic.print_err false true l' "Monomorphisation"
               "Unexpected kind of pattern for bit"; None)
       in findpat cases
    | _ -> None
  in

  (* Similarly, simple conditionals *)
  (* TODO: doublecheck *)
  let lit_eq (L_aux (l1,_)) (L_aux (l2,_)) =
    match l1,l2 with
    | (L_zero|L_false), (L_zero|L_false)
    | (L_one |L_true ), (L_one |L_true)
      -> Some true
    | L_undef, _ | _, L_undef -> None
    | _ -> Some (l1 = l2)
  in

  (* TODO: any useful type information revealed? (probably not) *)
  let try_app_infix (l,ann) (E_aux (e1,ann1)) id (E_aux (e2,ann2)) =
    let new_l = Generated l in
    match e1, id, e2 with
    | E_lit l1, ("=="|"!="), E_lit l2 ->
       let lit b = if b then L_true else L_false in
       let lit b = lit (if id = "==" then b else not b) in
       (match lit_eq l1 l2 with
       | Some b -> Some (E_aux (E_lit (L_aux (lit b,new_l)), (l,ann)))
       | None -> None)
    | _ -> None
  in

  (* Extract nvar substitution by comparing two types *)
  let build_nexp_subst l t1 t2 = [] (*
    let rec from_types t1 t2 =
      let t1 = match t1.t with Tabbrev(_,t) -> t | _ -> t1 in
      let t2 = match t2.t with Tabbrev(_,t) -> t | _ -> t2 in
      if t1 = t2 then [] else
        match t1.t,t2.t with
        | Tapp (s1,args1), Tapp (s2,args2) ->
           if s1 = s2 then
             List.concat (List.map2 from_args args1 args2)
           else (Reporting_basic.print_err false true l "Monomorphisation"
                   "Unexpected type mismatch"; [])
        | Ttup ts1, Ttup ts2 ->
           if List.length ts1 = List.length ts2 then
             List.concat (List.map2 from_types ts1 ts2)
           else (Reporting_basic.print_err false true l "Monomorphisation"
                   "Unexpected type mismatch"; [])
        | _ -> []
    and from_args arg1 arg2 =
    match arg1,arg2 with
    | TA_typ t1, TA_typ t2 -> from_types t1 t2
    | TA_nexp n1, TA_nexp n2 -> from_nexps n1 n2
    | _ -> []
    and from_nexps n1 n2 =
      match n1.nexp, n2.nexp with
      | Nvar s, Nvar s' when s = s' -> []
      | Nvar s, _ -> [(s,n2)]
      | Nadd (n3,n4), Nadd (n5,n6)
      | Nsub (n3,n4), Nsub (n5,n6)
      | Nmult (n3,n4), Nmult (n5,n6)
        -> from_nexps n3 n5 @ from_nexps n4 n6
      | N2n (n3,p1), N2n (n4,p2) when p1 = p2 -> from_nexps n3 n4
      | Npow (n3,p1), Npow (n4,p2) when p1 = p2 -> from_nexps n3 n4
      | Nneg n3, Nneg n4 -> from_nexps n3 n4
      | _ -> []
    in match t1,t2 with
    | Base ((_,t1),_,_,_,_,_),Base ((_,t2),_,_,_,_,_) -> from_types t1 t2
    | _ -> []*)
  in

  let nexp_substs = ref [] in

  (* Constant propogation *)
  let rec const_prop_exp substs ((E_aux (e,(l,annot))) as exp) =
    let re e = E_aux (e,(l,annot)) in
    match e with
      (* TODO: are there more circumstances in which we should get rid of these? *)
    | E_block [e] -> const_prop_exp substs e
    | E_block es -> re (E_block (List.map (const_prop_exp substs) es))
    | E_nondet es -> re (E_nondet (List.map (const_prop_exp substs) es))
       
    | E_id id ->
       (try ISubst.find id substs
        with Not_found -> exp)
    | E_lit _
    | E_sizeof _
    | E_internal_exp _
    | E_sizeof_internal _
    | E_internal_exp_user _
    | E_comment _
      -> exp
    | E_cast (t,e') -> re (E_cast (t, const_prop_exp substs e'))
    | E_app (id,es) ->
       let es' = List.map (const_prop_exp substs) es in
       (match const_prop_try_fn (id,es') with
       | None -> re (E_app (id,es'))
       | Some r -> r)
    | E_app_infix (e1,id,e2) ->
       let e1',e2' = const_prop_exp substs e1,const_prop_exp substs e2 in
       (match try_app_infix (l,annot) e1' (id_to_string id) e2' with
       | Some exp -> exp
       | None -> re (E_app_infix (e1',id,e2')))
    | E_tuple es -> re (E_tuple (List.map (const_prop_exp substs) es))
    | E_if (e1,e2,e3) ->
       let e1' = const_prop_exp substs e1 in
       let e2',e3' = const_prop_exp substs e2, const_prop_exp substs e3 in
       (match e1' with
       | E_aux (E_lit (L_aux ((L_true|L_false) as lit ,_)),_) ->
          let e' = match lit with L_true -> e2' | _ -> e3' in
          (match e' with E_aux (_,(_,annot')) ->
            nexp_substs := build_nexp_subst l annot annot' @ !nexp_substs;
            e')
       | _ -> re (E_if (e1',e2',e3')))
    | E_for (id,e1,e2,e3,ord,e4) -> re (E_for (id,const_prop_exp substs e1,const_prop_exp substs e2,const_prop_exp substs e3,ord,const_prop_exp (ISubst.remove id substs) e4))
    | E_vector es -> re (E_vector (List.map (const_prop_exp substs) es))
    | E_vector_indexed (ies,ed) -> re (E_vector_indexed (List.map (fun (i,e) -> (i,const_prop_exp substs e)) ies,
                                                         const_prop_opt_default substs ed))
    | E_vector_access (e1,e2) -> re (E_vector_access (const_prop_exp substs e1,const_prop_exp substs e2))
    | E_vector_subrange (e1,e2,e3) -> re (E_vector_subrange (const_prop_exp substs e1,const_prop_exp substs e2,const_prop_exp substs e3))
    | E_vector_update (e1,e2,e3) -> re (E_vector_update (const_prop_exp substs e1,const_prop_exp substs e2,const_prop_exp substs e3))
    | E_vector_update_subrange (e1,e2,e3,e4) -> re (E_vector_update_subrange (const_prop_exp substs e1,const_prop_exp substs e2,const_prop_exp substs e3,const_prop_exp substs e4))
    | E_vector_append (e1,e2) -> re (E_vector_append (const_prop_exp substs e1,const_prop_exp substs e2))
    | E_list es -> re (E_list (List.map (const_prop_exp substs) es))
    | E_cons (e1,e2) -> re (E_cons (const_prop_exp substs e1,const_prop_exp substs e2))
    | E_record fes -> re (E_record (const_prop_fexps substs fes))
    | E_record_update (e,fes) -> re (E_record_update (const_prop_exp substs e, const_prop_fexps substs fes))
    | E_field (e,id) -> re (E_field (const_prop_exp substs e,id))
    | E_case (e,cases) ->
       let e' = const_prop_exp substs e in
       (match can_match e' cases with
       | None -> re (E_case (e', List.map (const_prop_pexp substs) cases))
       | Some (E_aux (_,(_,annot')) as exp,newbindings) ->
          let newbindings_env = isubst_from_list newbindings in
          let substs' = ISubst.union (fun _ _ s -> Some s) substs newbindings_env in
          nexp_substs := build_nexp_subst l annot annot' @ !nexp_substs;
          const_prop_exp substs' exp)
    | E_let (lb,e) ->
       let (lb',substs') = const_prop_letbind substs lb in
       re (E_let (lb', const_prop_exp substs' e))
    | E_assign (le,e) -> re (E_assign (const_prop_lexp substs le, const_prop_exp substs e))
    | E_exit e -> re (E_exit (const_prop_exp substs e))
    | E_return e -> re (E_return (const_prop_exp substs e))
    | E_assert (e1,e2) -> re (E_assert (const_prop_exp substs e1,const_prop_exp substs e2))
    | E_internal_cast (ann,e) -> re (E_internal_cast (ann,const_prop_exp substs e))
    | E_comment_struc e -> re (E_comment_struc e)
    | E_internal_let _
    | E_internal_plet _
    | E_internal_return _
      -> raise (Reporting_basic.err_unreachable l
                  "Unexpected internal expression encountered in monomorphisation")
    and const_prop_opt_default substs ((Def_val_aux (ed,annot)) as eda) =
    match ed with
    | Def_val_empty -> eda
    | Def_val_dec e -> Def_val_aux (Def_val_dec (const_prop_exp substs e),annot)
  and const_prop_fexps substs (FES_aux (FES_Fexps (fes,flag), annot)) =
    FES_aux (FES_Fexps (List.map (const_prop_fexp substs) fes, flag), annot)
  and const_prop_fexp substs (FE_aux (FE_Fexp (id,e), annot)) =
    FE_aux (FE_Fexp (id,const_prop_exp substs e),annot)
  and const_prop_pexp substs (Pat_aux (Pat_exp (p,e),l)) =
    Pat_aux (Pat_exp (p,const_prop_exp (remove_bound substs p) e),l)
  and const_prop_letbind substs (LB_aux (lb,annot)) =
    match lb with
    | LB_val_explicit (tysch,p,e) ->
       (LB_aux (LB_val_explicit (tysch,p,const_prop_exp substs e), annot),
        remove_bound substs p)
    | LB_val_implicit (p,e) ->
       (LB_aux (LB_val_implicit (p,const_prop_exp substs e), annot),
        remove_bound substs p)
  and const_prop_lexp substs ((LEXP_aux (e,annot)) as le) =
    let re e = LEXP_aux (e,annot) in
    match e with
    | LEXP_id _ (* shouldn't end up substituting here *)
    | LEXP_cast _
      -> le
    | LEXP_memory (id,es) -> re (LEXP_memory (id,List.map (const_prop_exp substs) es)) (* or here *)
    | LEXP_tup les -> re (LEXP_tup (List.map (const_prop_lexp substs) les))
    | LEXP_vector (le,e) -> re (LEXP_vector (const_prop_lexp substs le, const_prop_exp substs e))
    | LEXP_vector_range (le,e1,e2) -> re (LEXP_vector_range (const_prop_lexp substs le, const_prop_exp substs e1, const_prop_exp substs e2))
    | LEXP_field (le,id) -> re (LEXP_field (const_prop_lexp substs le, id))
  (* Reduce a function when
     1. all arguments are values,
     2. the function is pure,
     3. the result is a value
     (and 4. the function is not scattered, but that's not terribly important)
     to try and keep execution time and the results managable.
  *)
  and const_prop_try_fn (id,args) =
    if not (List.for_all is_value args) then
      None
    else
      let i = id_to_string id in
      let Defs ds = defs in
      match list_extract (function
      | (DEF_fundef (FD_aux (FD_function (_,_,eff,((FCL_aux (FCL_Funcl (id',_,_),_))::_ as fcls)),_)))
        -> if i = id_to_string id' then Some (eff,fcls) else None
      | _ -> None) ds with
      | None -> None
      | Some (eff,_) when not (is_pure eff) -> None
      | Some (_,fcls) ->
         let arg = match args with
           | [] -> E_aux (E_lit (L_aux (L_unit,Unknown)),(Unknown,None))
           | [e] -> e
           | _ -> E_aux (E_tuple args,(Unknown,None)) in
         let cases = List.map (function
           | FCL_aux (FCL_Funcl (_,pat,exp), ann) -> Pat_aux (Pat_exp (pat,exp),ann))
           fcls in
         match can_match arg cases with
         | Some (exp,bindings) ->
            let substs = isubst_from_list bindings in
            let result = const_prop_exp substs exp in
            if is_value result then Some result else None
         | None -> None
  in

  let subst_exp subst exp =
    if !disable_const_propagation then
    (* TODO: This just sticks a let in - we really need propogation *)
      let (subi,(E_aux (_,subannot) as sube)) = subst in
      let E_aux (e,(l,annot)) = exp in
      let lg = Generated l in
      let id = match subi with Id_aux (i,l) -> Id_aux (i,lg) in
      let p = P_aux (P_id id, subannot) in
      E_aux (E_let (LB_aux (LB_val_implicit (p,sube),(lg,annot)), exp),(lg,annot))
    else 
      let substs = isubst_from_list [subst] in
      let () = nexp_substs := [] in
      let exp' = const_prop_exp substs exp in
      (* Substitute what we've learned about nvars into the term *)
      let nsubsts = isubst_from_list !nexp_substs in
      let () = nexp_substs := [] in
      nexp_subst_exp nsubsts refinements exp'
  in
    
let env_some_enum_lookup _ _ = None in
  (* Split a variable pattern into every possible value *)

  let split var env (Typ_aux (ty,l) as typ) =
    let new_l = Generated l in
    let new_id i = Id_aux (Id i, new_l) in
    let v = string_of_id var in
    let cannot () =
      raise (Reporting_basic.err_general l
               ("Cannot split type " ^ string_of_typ typ ^ " for variable " ^ v))
    in
    match ty with
    | Typ_id id ->
       (match env_some_enum_lookup id env with
          (* enumerations *)
       | Some ns -> List.map (fun n -> (P_aux (P_id (new_id n),(l,None)),
                                        (var,E_aux (E_id (new_id n),(new_l,None))))) ns
       | None ->
          if id_to_string id = "bit" then
            List.map (fun b ->
              P_aux (P_lit (L_aux (b,new_l)),(l,None)),
              (var,E_aux (E_lit (L_aux (b,new_l)),(new_l, None))))
              [L_zero; L_one]
          else cannot ())
       (*|  vectors TODO *)
       (*|  numbers TODO *)
    | _ -> cannot ()
  in
  
  (* Split variable patterns at the given locations *)

  let map_locs ls (Defs defs) =
    let rec match_l = function
      | Unknown
      | Int _ -> []
      | Generated l -> [] (* Could do match_l l, but only want to split user-written patterns *)
      | Range (p,q) ->
         List.filter (fun ((filename,line),_) ->
           Filename.basename p.Lexing.pos_fname = filename &&
             p.Lexing.pos_lnum <= line && line <= q.Lexing.pos_lnum) ls
    in 

    let split_pat var p =
      let rec list f = function
        | [] -> None
        | h::t ->
           match f h with
           | None -> (match list f t with None -> None | Some (l,ps,r) -> Some (h::l,ps,r))
           | Some ps -> Some ([],ps,t)
      in
      let rec spl (P_aux (p,(l,annot))) =
        let relist f ctx ps =
          optmap (list f ps) 
            (fun (left,ps,right) ->
              List.map (fun (p,sub) -> P_aux (ctx (left@p::right),(l,annot)),sub) ps)
        in
        let re f p =
          optmap (spl p)
            (fun ps -> List.map (fun (p,sub) -> (P_aux (f p,(l,annot)), sub)) ps)
        in
        let fpat (FP_aux ((FP_Fpat (id,p),annot))) =
          optmap (spl p)
            (fun ps -> List.map (fun (p,sub) -> FP_aux (FP_Fpat (id,p), annot), sub) ps)
        in
        let ipat (i,p) = optmap (spl p) (List.map (fun (p,sub) -> (i,p),sub))
        in
        match p with
        | P_lit _
        | P_wild
          -> None
        | P_as (p',id) ->
           let i = id_to_string id in
           if i = var
           then raise (Reporting_basic.err_general l
                         ("Cannot split " ^ var ^ " on 'as' pattern"))
           else re (fun p -> P_as (p,id)) p'
        | P_typ (t,p') -> re (fun p -> P_typ (t,p)) p'
        | P_id id ->
           let i = id_to_string id in
           if i = var
           then
             match annot with
             | Some (env,ty,_) -> Some (split id env ty)
             | None -> raise (Reporting_basic.err_general l
                                ("Missing type environment when splitting " ^ var))
           else None
        | P_app (id,ps) ->
           relist spl (fun ps -> P_app (id,ps)) ps
        | P_record (fps,flag) ->
           relist fpat (fun fps -> P_record (fps,flag)) fps
        | P_vector ps ->
           relist spl (fun ps -> P_vector ps) ps
        | P_vector_indexed ips ->
           relist ipat (fun ips -> P_vector_indexed ips) ips
        | P_vector_concat ps ->
           relist spl (fun ps -> P_vector_concat ps) ps
        | P_tup ps ->
           relist spl (fun ps -> P_tup ps) ps
        | P_list ps ->
           relist spl (fun ps -> P_list ps) ps
      in spl p
    in

    let map_pat_by_loc (P_aux (p,(l,_)) as pat) =
      match match_l l with
      | [] -> None
      | [(_,var)] -> split_pat var pat
      | lvs -> raise (Reporting_basic.err_general l
                        ("Multiple variables to split on: " ^ String.concat ", " (List.map snd lvs)))
    in
    let map_pat (P_aux (p,(l,tannot)) as pat) =
      match map_pat_by_loc pat with
      | Some l -> VarSplit l
      | None ->
         match p with
         | P_app (id,args) ->
            (try
              let i = id_to_string id in
              let variants = List.assoc i refinements in
              let env = match tannot with Some (env,_,_) -> env | None -> failwith "env" in
              let constr_out_typ =
                match Env.lookup_id id env with
                | Union (qs,Typ_aux (Typ_fn(_,outt,_),_)) -> outt
                | _ -> raise (Reporting_basic.err_general l
                                ("Constructor " ^ i ^ " is not a construtor!"))
              in
              let varmap = build_nexp_subst l constr_out_typ tannot in
              let map_inst (insts,i') =
                let insts = List.map (fun (v,i) ->
                  ((match List.assoc (string_of_kid v) varmap with
                  | Nexp_aux (Nexp_var s, _) -> s
                  | _ -> raise (Reporting_basic.err_general l
                                  ("Constructor parameter not a variable: " ^ string_of_kid v))),
                   Nexp_aux (Nexp_constant i,Generated l)))
                  insts in
                P_aux (P_app (Id_aux (Id i',Generated l),args),(Generated l,tannot)),
                ksubst_from_list insts
              in
              ConstrSplit (List.map map_inst variants)
            with Not_found -> NoSplit)
         | _ -> NoSplit
    in

    let check_single_pat (P_aux (_,(l,annot)) as p) =
      match match_l l with
      | [] -> p
      | lvs ->
         let pvs = bindings_from_pat p in
         let pvs = List.map string_of_id pvs in
         let overlap = List.exists (fun (_,v) -> List.mem v pvs) lvs in
         let () =
           if overlap then
             Reporting_basic.print_err false true l "Monomorphisation"
               "Splitting a singleton pattern is not possible"
         in p
    in

    let rec map_exp ((E_aux (e,annot)) as ea) =
      let re e = E_aux (e,annot) in
      match e with
      | E_block es -> re (E_block (List.map map_exp es))
      | E_nondet es -> re (E_nondet (List.map map_exp es))
      | E_id _
      | E_lit _
      | E_sizeof _
      | E_internal_exp _
      | E_sizeof_internal _
      | E_internal_exp_user _
      | E_comment _
        -> ea
      | E_cast (t,e') -> re (E_cast (t, map_exp e'))
      | E_app (id,es) -> re (E_app (id,List.map map_exp es))
      | E_app_infix (e1,id,e2) -> re (E_app_infix (map_exp e1,id,map_exp e2))
      | E_tuple es -> re (E_tuple (List.map map_exp es))
      | E_if (e1,e2,e3) -> re (E_if (map_exp e1, map_exp e2, map_exp e3))
      | E_for (id,e1,e2,e3,ord,e4) -> re (E_for (id,map_exp e1,map_exp e2,map_exp e3,ord,map_exp e4))
      | E_vector es -> re (E_vector (List.map map_exp es))
      | E_vector_indexed (ies,ed) -> re (E_vector_indexed (List.map (fun (i,e) -> (i,map_exp e)) ies,
                                                           map_opt_default ed))
      | E_vector_access (e1,e2) -> re (E_vector_access (map_exp e1,map_exp e2))
      | E_vector_subrange (e1,e2,e3) -> re (E_vector_subrange (map_exp e1,map_exp e2,map_exp e3))
      | E_vector_update (e1,e2,e3) -> re (E_vector_update (map_exp e1,map_exp e2,map_exp e3))
      | E_vector_update_subrange (e1,e2,e3,e4) -> re (E_vector_update_subrange (map_exp e1,map_exp e2,map_exp e3,map_exp e4))
      | E_vector_append (e1,e2) -> re (E_vector_append (map_exp e1,map_exp e2))
      | E_list es -> re (E_list (List.map map_exp es))
      | E_cons (e1,e2) -> re (E_cons (map_exp e1,map_exp e2))
      | E_record fes -> re (E_record (map_fexps fes))
      | E_record_update (e,fes) -> re (E_record_update (map_exp e, map_fexps fes))
      | E_field (e,id) -> re (E_field (map_exp e,id))
      | E_case (e,cases) -> re (E_case (map_exp e, List.concat (List.map map_pexp cases)))
      | E_let (lb,e) -> re (E_let (map_letbind lb, map_exp e))
      | E_assign (le,e) -> re (E_assign (map_lexp le, map_exp e))
      | E_exit e -> re (E_exit (map_exp e))
      | E_return e -> re (E_return (map_exp e))
      | E_assert (e1,e2) -> re (E_assert (map_exp e1,map_exp e2))
      | E_internal_cast (ann,e) -> re (E_internal_cast (ann,map_exp e))
      | E_comment_struc e -> re (E_comment_struc e)
      | E_internal_let (le,e1,e2) -> re (E_internal_let (map_lexp le, map_exp e1, map_exp e2))
      | E_internal_plet (p,e1,e2) -> re (E_internal_plet (check_single_pat p, map_exp e1, map_exp e2))
      | E_internal_return e -> re (E_internal_return (map_exp e))
    and map_opt_default ((Def_val_aux (ed,annot)) as eda) =
      match ed with
      | Def_val_empty -> eda
      | Def_val_dec e -> Def_val_aux (Def_val_dec (map_exp e),annot)
    and map_fexps (FES_aux (FES_Fexps (fes,flag), annot)) =
      FES_aux (FES_Fexps (List.map map_fexp fes, flag), annot)
    and map_fexp (FE_aux (FE_Fexp (id,e), annot)) =
      FE_aux (FE_Fexp (id,map_exp e),annot)
    and map_pexp (Pat_aux (Pat_exp (p,e),l)) =
      match map_pat p with
      | NoSplit -> [Pat_aux (Pat_exp (p,map_exp e),l)]
      | VarSplit patsubsts ->
         List.map (fun (pat',subst) ->
           let exp' = subst_exp subst e in
           Pat_aux (Pat_exp (pat', map_exp exp'),l))
           patsubsts
      | ConstrSplit patnsubsts ->
         List.map (fun (pat',nsubst) ->
           (* Leave refinements to later *)
           let pat' = nexp_subst_pat nsubst [] pat' in
           let exp' = nexp_subst_exp nsubst [] e in
           Pat_aux (Pat_exp (pat', map_exp exp'),l)
         ) patnsubsts
    and map_letbind (LB_aux (lb,annot)) =
      match lb with
      | LB_val_explicit (tysch,p,e) -> LB_aux (LB_val_explicit (tysch,check_single_pat p,map_exp e), annot)
      | LB_val_implicit (p,e) -> LB_aux (LB_val_implicit (check_single_pat p,map_exp e), annot)
    and map_lexp ((LEXP_aux (e,annot)) as le) =
      let re e = LEXP_aux (e,annot) in
      match e with
      | LEXP_id _
      | LEXP_cast _
        -> le
      | LEXP_memory (id,es) -> re (LEXP_memory (id,List.map map_exp es))
      | LEXP_tup les -> re (LEXP_tup (List.map map_lexp les))
      | LEXP_vector (le,e) -> re (LEXP_vector (map_lexp le, map_exp e))
      | LEXP_vector_range (le,e1,e2) -> re (LEXP_vector_range (map_lexp le, map_exp e1, map_exp e2))
      | LEXP_field (le,id) -> re (LEXP_field (map_lexp le, id))
    in

    let map_funcl (FCL_aux (FCL_Funcl (id,pat,exp),annot)) =
      match map_pat pat with
      | NoSplit -> [FCL_aux (FCL_Funcl (id, pat, map_exp exp), annot)]
      | VarSplit patsubsts ->
         List.map (fun (pat',subst) ->
           let exp' = subst_exp subst exp in
           FCL_aux (FCL_Funcl (id, pat', map_exp exp'), annot))
           patsubsts
      | ConstrSplit patnsubsts ->
         List.map (fun (pat',nsubst) ->
           (* Leave refinements to later *)
           let pat' = nexp_subst_pat nsubst [] pat' in
           let exp' = nexp_subst_exp nsubst [] exp in
           FCL_aux (FCL_Funcl (id, pat', map_exp exp'), annot)
         ) patnsubsts
    in

    let map_fundef (FD_aux (FD_function (r,t,e,fcls),annot)) =
      FD_aux (FD_function (r,t,e,List.concat (List.map map_funcl fcls)),annot)
    in
    let map_scattered_def sd =
      match sd with
      | SD_aux (SD_scattered_funcl fcl, annot) ->
         List.map (fun fcl' -> SD_aux (SD_scattered_funcl fcl', annot)) (map_funcl fcl)
      | _ -> [sd]
    in
    let map_def d =
      match d with
      | DEF_kind _
      | DEF_type _
      | DEF_spec _
      | DEF_default _
      | DEF_reg_dec _
      | DEF_comm _
      | DEF_overload _
        -> [d]
      | DEF_fundef fd -> [DEF_fundef (map_fundef fd)]
      | DEF_val lb -> [DEF_val (map_letbind lb)]
      | DEF_scattered sd -> List.map (fun x -> DEF_scattered x) (map_scattered_def sd)

    in
    Defs (List.concat (List.map map_def defs))
  in
  map_locs splits defs'