typer.ml 28.2 KB
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(* TODO:
   rewrite type-checking of operators to propagate constraint *)

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(* I. Transform the abstract syntax of types and patterns into
      the internal form *)
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open Location
open Ast
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open Ident
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module S = struct type t = string let compare = compare end
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module TypeEnv = Map.Make(S)
module Env = Map.Make(Ident.Id)
(*
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module StringSet = Set.Make(S)
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*)
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exception NonExhaustive of Types.descr
exception Constraint of Types.descr * Types.descr * string
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exception ShouldHave of Types.descr * string
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exception WrongLabel of Types.descr * label
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exception UnboundId of string
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let raise_loc loc exn = raise (Location (loc,exn))
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(* Internal representation as a graph (desugar recursive types and regexp),
   to compute freevars, etc... *)

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type ti = {
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  id : int; 
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  mutable seen : bool;
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  mutable loc' : loc;
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  mutable fv : fv option; 
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  mutable descr': descr;
  mutable type_node: Types.node option;
  mutable pat_node: Patterns.node option
} 
and descr =
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  | IAlias of string * ti
  | IType of Types.descr
  | IOr of ti * ti
  | IAnd of ti * ti
  | IDiff of ti * ti
  | ITimes of ti * ti
  | IXml of ti * ti
  | IArrow of ti * ti
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  | IOptional of ti
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  | IRecord of bool * ti label_map
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  | ICapture of id
  | IConstant of id * Types.const
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type glb = ti TypeEnv.t
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let mk' =
  let counter = ref 0 in
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  fun loc ->
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    incr counter;
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    let rec x = { 
      id = !counter; 
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      seen = false;
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      loc' = loc; 
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      fv = None; 
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      descr' = IAlias ("__dummy__", x);
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      type_node = None; 
      pat_node = None 
    } in
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    x

let cons loc d =
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  let x = mk' loc in
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  x.descr' <- d;
  x
    
(* Note:
   Compilation of Regexp is implemented as a ``rewriting'' of
   the parsed syntax, in order to be able to print its result
   (for debugging for instance)
   
   It would be possible (and a little more efficient) to produce
   directly ti nodes.
*)
    
module Regexp = struct
  let defs = ref []
  let name =
    let c = ref 0 in
    fun () ->
      incr c;
      "#" ^ (string_of_int !c)

  let rec seq_vars accu = function
    | Epsilon | Elem _ -> accu
    | Seq (r1,r2) | Alt (r1,r2) -> seq_vars (seq_vars accu r1) r2
    | Star r | WeakStar r -> seq_vars accu r
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    | SeqCapture (v,r) -> seq_vars (IdSet.add v accu) r
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  let uniq_id = let r = ref 0 in fun () -> incr r; !r

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  type flat =  
    | REpsilon 
    | RElem of int * Ast.ppat  (* the int arg is used
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					    to stop generic comparison *)
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    | RSeq of flat * flat
    | RAlt of flat * flat
    | RStar of flat
    | RWeakStar of flat
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  let re_loc = ref noloc

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  let rec propagate vars : regexp -> flat = function
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    | Epsilon -> REpsilon
    | Elem x -> let p = vars x in RElem (uniq_id (),p)
    | Seq (r1,r2) -> RSeq (propagate vars r1,propagate vars r2)
    | Alt (r1,r2) -> RAlt (propagate vars r1, propagate vars r2)
    | Star r -> RStar (propagate vars r)
    | WeakStar r -> RWeakStar (propagate vars r)
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    | SeqCapture (v,x) -> 
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	let v= mk !re_loc (Capture v) in
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	propagate (fun p -> mk !re_loc (And (vars p,v))) x
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  let dummy_pat = mk noloc (PatVar "DUMMY")
  let cup r1 r2 =
    if r1 == dummy_pat then r2 else
      if r2 == dummy_pat then r1 else
	mk !re_loc (Or (r1,r2))
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(*TODO: review this compilation schema to avoid explosion when
  coding (Optional x) by  (Or(Epsilon,x)); memoization ... *)

  module Memo = Map.Make(struct type t = flat list let compare = compare end)
  module Coind = Set.Make(struct type t = flat list let compare = compare end)
  let memo = ref Memo.empty

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  let rec compile fin e seq : Ast.ppat = 
    if Coind.mem seq !e then dummy_pat
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    else (
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      e := Coind.add seq !e;
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      match seq with
	| [] ->
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	    fin
	| REpsilon :: rest -> 
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	    compile fin e rest
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	| RElem (_,p) :: rest -> 
	    mk !re_loc (Prod (p, guard_compile fin rest))
	| RSeq (r1,r2) :: rest -> 
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	    compile fin e (r1 :: r2 :: rest)
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	| RAlt (r1,r2) :: rest -> 
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	    cup (compile fin e (r1::rest)) (compile fin e (r2::rest))
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	| RStar r :: rest -> 
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	    cup (compile fin e (r::seq)) (compile fin e rest) 
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	| RWeakStar r :: rest -> 
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	    cup (compile fin e rest) (compile fin e (r::seq))
    )
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  and guard_compile fin seq =
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    try Memo.find seq !memo
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    with
	Not_found ->
          let n = name () in
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	  let v = mk !re_loc (PatVar n) in
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          memo := Memo.add seq v !memo;
	  let d = compile fin (ref Coind.empty) seq in
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	  assert (d != dummy_pat);
	  defs := (n,d) :: !defs;
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	  v

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(*
  type trans = [ `Alt of gnode * gnode | `Elem of Ast.ppat * gnode | `Final ]
  and gnode = 
      {
	mutable seen  : bool;
	mutable compile : bool;
	name  : string;
	mutable trans : trans;
      }

  let new_node() = { seen = false; compile = false; 
		     name = name(); trans = `Final }
  let to_compile = ref []

  let rec compile after = function
    | `Epsilon -> after
    | `Elem (_,p) -> 
	if not after.compile then (after.compile <- true; 
				   to_compile := after :: !to_compile);
	{ new_node () with trans = `Elem (p, after)  }
    | `Seq(r1,r2) -> compile (compile after r2) r1
    | `Alt(r1,r2) ->
	let r1 = compile after r1 and r2 = compile after r2 in
	{ new_node () with trans = `Alt (r1,r2) }
    | `Star r ->
	let n  = new_node() in
	n.trans <- `Alt (compile n r, after);
	n
    | `WeakStar r ->
	let n  = new_node() in
	n.trans <- `Alt (after, compile n r);
	n

  let seens = ref []	
  let rec collect_aux accu n =
    if n.seen then accu 
    else ( seens := n :: !seens;
	   match n.trans with
	     | `Alt (n1,n2) -> collect_aux (collect_aux accu n2) n1
	     | _ -> n :: accu
	 )

  let collect fin n =
    let l = collect_aux [] n in
    List.iter (fun n -> n.seen <- false) !seens;
    let l = List.map (fun n ->
			match n.trans with
			  | `Final -> fin
			  | `Elem (p,a) -> 
			      mk !re_loc (Prod(p, mk !re_loc (PatVar a.name)))
			  | _ -> assert false
		     ) l in
    match l with
      | h::t ->
	  List.fold_left (fun accu p -> mk !re_loc (Or (accu,p))) h t
      | _ -> assert false
*)    
	
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  let constant_nil t v = 
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    mk !re_loc 
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      (And (t, (mk !re_loc (Constant (v, Types.Atom Sequence.nil_atom)))))
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  let compile loc regexp queue : ppat =
    re_loc := loc;
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    let vars = seq_vars IdSet.empty regexp in
    let fin = IdSet.fold constant_nil queue vars in
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    let re = propagate (fun p -> p) regexp in
    let n = guard_compile fin [re] in
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    memo := Memo.empty; 
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    let d = !defs in
    defs := [];
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(*
    let after = new_node() in
    let n = collect queue (compile after re) in
    let d = List.map (fun n -> (n.name, collect queue n)) !to_compile in
    to_compile := [];
*)

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    mk !re_loc (Recurs (n,d))
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end

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let compile_regexp = Regexp.compile noloc
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let rec compile env { loc = loc; descr = d } : ti = 
  match (d : Ast.ppat') with
  | PatVar s -> 
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      (try TypeEnv.find s env
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       with Not_found -> 
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	 raise_loc_generic loc ("Undefined type variable " ^ s)
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      )
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  | Recurs (t, b) -> compile (compile_many env b) t
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  | Regexp (r,q) -> compile env (Regexp.compile loc r q)
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  | Internal t -> cons loc (IType t)
  | Or (t1,t2) -> cons loc (IOr (compile env t1, compile env t2))
  | And (t1,t2) -> cons loc (IAnd (compile env t1, compile env t2))
  | Diff (t1,t2) -> cons loc (IDiff (compile env t1, compile env t2))
  | Prod (t1,t2) -> cons loc (ITimes (compile env t1, compile env t2))
  | XmlT (t1,t2) -> cons loc (IXml (compile env t1, compile env t2))
  | Arrow (t1,t2) -> cons loc (IArrow (compile env t1, compile env t2))
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  | Optional t -> cons loc (IOptional (compile env t))
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  | Record (o,r) ->  cons loc (IRecord (o, LabelMap.map (compile env) r))
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  | Constant (x,v) -> cons loc (IConstant (x,v))
  | Capture x -> cons loc (ICapture x)
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and compile_many env b = 
  let b = List.map (fun (v,t) -> (v,t,mk' t.loc)) b in
  let env = 
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    List.fold_left (fun env (v,t,x) -> TypeEnv.add v x env) env b in
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  List.iter (fun (v,t,x) -> x.descr' <- IAlias (v, compile env t)) b;
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  env

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module IntSet = 
  Set.Make(struct type t = int let compare (x:int) y = compare x y end)

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let comp_fv_seen = ref []
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let comp_fv_res = ref IdSet.empty
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let rec comp_fv s =
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  match s.fv with
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    | Some fv -> comp_fv_res := IdSet.cup fv !comp_fv_res
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    | None ->
	(match s.descr' with
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	   | IAlias (_,x) -> 
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	       if x.seen then ()
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	       else ( 
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		 x.seen <- true;
		 comp_fv_seen := x :: !comp_fv_seen; 
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		 comp_fv x
	       ) 
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	   | IOr (s1,s2) 
	   | IAnd (s1,s2)
	   | IDiff (s1,s2)
	   | ITimes (s1,s2) | IXml (s1,s2)
	   | IArrow (s1,s2) -> comp_fv s1; comp_fv s2
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	   | IOptional r -> comp_fv r
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	   | IRecord (_,r) -> LabelMap.iter comp_fv r
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	   | IType _ -> ()
	   | ICapture x
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	   | IConstant (x,_) -> comp_fv_res := IdSet.add x !comp_fv_res
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	)
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let fv s =   
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  match s.fv with
    | Some l -> l
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    | None -> 
	comp_fv s;
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	let l = !comp_fv_res in
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	comp_fv_res := IdSet.empty;
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	List.iter (fun n -> n.seen <- false) !comp_fv_seen;
	comp_fv_seen := [];
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	s.fv <- Some l; 
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	l

let rec typ seen s : Types.descr =
  match s.descr' with
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    | IAlias (v,x) ->
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	if IntSet.mem s.id seen then 
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	  raise_loc_generic s.loc' 
	    ("Unguarded recursion on variable " ^ v ^ " in this type")
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	else typ (IntSet.add s.id seen) x
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    | IType t -> t
    | IOr (s1,s2) -> Types.cup (typ seen s1) (typ seen s2)
    | IAnd (s1,s2) ->  Types.cap (typ seen s1) (typ seen s2)
    | IDiff (s1,s2) -> Types.diff (typ seen s1) (typ seen s2)
    | ITimes (s1,s2) ->	Types.times (typ_node s1) (typ_node s2)
    | IXml (s1,s2) ->	Types.xml (typ_node s1) (typ_node s2)
    | IArrow (s1,s2) ->	Types.arrow (typ_node s1) (typ_node s2)
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    | IOptional s -> Types.Record.or_absent (typ seen s)
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    | IRecord (o,r) -> 
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	Types.record' 
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	  (o, LabelMap.map typ_node r)
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    | ICapture x | IConstant (x,_) -> assert false
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and typ_node s : Types.node =
  match s.type_node with
    | Some x -> x
    | None ->
	let x = Types.make () in
	s.type_node <- Some x;
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	let t = typ IntSet.empty s in
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	Types.define x t;
	x

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let type_node s = 
  let s = typ_node s in
  let s = Types.internalize s in
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(*  Types.define s (Types.normalize (Types.descr s)); *)
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  s
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let rec pat seen s : Patterns.descr =
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  if IdSet.is_empty (fv s) 
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  then Patterns.constr (Types.descr (type_node s)) 
  else
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    try pat_aux seen s
    with Patterns.Error e -> raise_loc_generic s.loc' e
      | Location (loc,exn) when loc = noloc -> raise (Location (s.loc', exn))


and pat_aux seen s = match s.descr' with
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  | IAlias (v,x) ->
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      if IntSet.mem s.id seen 
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      then raise 
	(Patterns.Error
	   ("Unguarded recursion on variable " ^ v ^ " in this pattern"));
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      pat (IntSet.add s.id seen) x
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  | IOr (s1,s2) -> Patterns.cup (pat seen s1) (pat seen s2)
  | IAnd (s1,s2) -> Patterns.cap (pat seen s1) (pat seen s2)
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  | IDiff (s1,s2) when IdSet.is_empty (fv s2) ->
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      let s2 = Types.neg (Types.descr (type_node s2)) in
      Patterns.cap (pat seen s1) (Patterns.constr s2)
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  | IDiff _ ->
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      raise (Patterns.Error "Difference not allowed in patterns")
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  | ITimes (s1,s2) -> Patterns.times (pat_node s1) (pat_node s2)
  | IXml (s1,s2) -> Patterns.xml (pat_node s1) (pat_node s2)
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  | IOptional _ -> 
      raise 
      (Patterns.Error 
	 "Optional field not allowed in record patterns")
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  | IRecord (o,r) ->
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      let pats = ref [] in
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      let aux l s = 
	if IdSet.is_empty (fv s) then type_node s
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	else
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	  ( pats := Patterns.record l (pat_node s) :: !pats;
	    Types.any_node )
      in
      let constr = Types.record' (o,LabelMap.mapi aux r) in
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      List.fold_left Patterns.cap (Patterns.constr constr) !pats
(* TODO: can avoid constr when o=true, and all fields have fv *)
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  | ICapture x ->  Patterns.capture x
  | IConstant (x,c) -> Patterns.constant x c
  | IArrow _ ->
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      raise (Patterns.Error "Arrow not allowed in patterns")
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  | IType _ -> assert false
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and pat_node s : Patterns.node =
  match s.pat_node with
    | Some x -> x
    | None ->
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	let x = Patterns.make (fv s) in
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	s.pat_node <- Some x;
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	let t = pat IntSet.empty s in
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	Patterns.define x t;
	x

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let mk_typ e =
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  if IdSet.is_empty (fv e) then type_node e
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  else raise_loc_generic e.loc' "Capture variables are not allowed in types"
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let typ glb e =
  mk_typ (compile glb e)

let pat glb e =
  pat_node (compile glb e)
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let register_global_types glb b =
  let env' = compile_many glb b in
  List.fold_left 
    (fun glb (v,{ loc = loc }) -> 
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       let t = TypeEnv.find v env' in
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       let d = Types.descr (mk_typ t) in
       (*	       let d = Types.normalize d in*)
       Types.Print.register_global v d;
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       if TypeEnv.mem v glb
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       then raise_loc_generic loc ("Multiple definition for type " ^ v);
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       TypeEnv.add v t glb
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    ) glb b
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(* II. Build skeleton *)

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module Fv = IdSet
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(* IDEA: introduce a node Loc in the AST to override nolocs
   in sub-expressions *)
   
let rec expr loc' glb { loc = loc; descr = d } = 
  let loc =  if loc = noloc then loc' else loc in
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  let (fv,td) = 
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    match d with
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      | Forget (e,t) ->
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	  let (fv,e) = expr loc glb e and t = typ glb t in
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	  (fv, Typed.Forget (e,t))
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      | Var s -> (Fv.singleton s, Typed.Var s)
      | Apply (e1,e2) -> 
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	  let (fv1,e1) = expr loc glb e1 and (fv2,e2) = expr loc glb e2 in
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	  (Fv.cup fv1 fv2, Typed.Apply (e1,e2))
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      | Abstraction a ->
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	  let iface = List.map (fun (t1,t2) -> (typ glb t1, typ glb t2)) 
			a.fun_iface in
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	  let t = List.fold_left 
		    (fun accu (t1,t2) -> Types.cap accu (Types.arrow t1 t2)) 
		    Types.any iface in
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	  let iface = List.map 
			(fun (t1,t2) -> (Types.descr t1, Types.descr t2)) 
			iface in
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	  let (fv0,body) = branches loc glb a.fun_body in
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	  let fv = match a.fun_name with
	    | None -> fv0
	    | Some f -> Fv.remove f fv0 in
	  (fv,
	   Typed.Abstraction 
	     { Typed.fun_name = a.fun_name;
	       Typed.fun_iface = iface;
	       Typed.fun_body = body;
	       Typed.fun_typ = t;
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	       Typed.fun_fv = fv
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	     }
	  )
      | Cst c -> (Fv.empty, Typed.Cst c)
      | Pair (e1,e2) ->
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	  let (fv1,e1) = expr loc glb e1 and (fv2,e2) = expr loc glb e2 in
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	  (Fv.cup fv1 fv2, Typed.Pair (e1,e2))
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      | Xml (e1,e2) ->
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	  let (fv1,e1) = expr loc glb e1 and (fv2,e2) = expr loc glb e2 in
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	  (Fv.cup fv1 fv2, Typed.Xml (e1,e2))
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      | Dot (e,l) ->
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	  let (fv,e) = expr loc glb e in
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	  (fv,  Typed.Dot (e,l))
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      | RemoveField (e,l) ->
	  let (fv,e) = expr loc glb e in
	  (fv,  Typed.RemoveField (e,l))
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      | RecordLitt r -> 
	  let fv = ref Fv.empty in
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	  let r = LabelMap.map 
		    (fun e -> 
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		       let (fv2,e) = expr loc glb e 
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		       in fv := Fv.cup !fv fv2; e)
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		    r in
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	  (!fv, Typed.RecordLitt r)
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      | Op (op,le) ->
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	  let (fvs,ltes) = List.split (List.map (expr loc glb) le) in
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	  let fv = List.fold_left Fv.cup Fv.empty fvs in
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	  (fv, Typed.Op (op,ltes))
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      | Match (e,b) -> 
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	  let (fv1,e) = expr loc glb e
	  and (fv2,b) = branches loc glb b in
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	  (Fv.cup fv1 fv2, Typed.Match (e, b))
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      | Map (e,b) ->
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	  let (fv1,e) = expr loc glb e
	  and (fv2,b) = branches loc glb b in
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	  (Fv.cup fv1 fv2, Typed.Map (e, b))
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      | Try (e,b) ->
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	  let (fv1,e) = expr loc glb e
	  and (fv2,b) = branches loc glb b in
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	  (Fv.cup fv1 fv2, Typed.Try (e, b))
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  in
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  fv,
  { Typed.exp_loc = loc;
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    Typed.exp_typ = Types.empty;
    Typed.exp_descr = td;
  }
	      
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  and branches loc glb b = 
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    let fv = ref Fv.empty in
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    let accept = ref Types.empty in
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    let b = List.map 
	      (fun (p,e) ->
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		 let (fv2,e) = expr loc glb e in
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		 let p = pat glb p in
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		 let fv2 = Fv.diff fv2 (Patterns.fv p) in
		 fv := Fv.cup !fv fv2;
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		 accept := Types.cup !accept (Types.descr (Patterns.accept p));
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		 { Typed.br_used = false;
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		   Typed.br_pat = p;
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		   Typed.br_body = e }
	      ) b in
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    (!fv, 
     { 
       Typed.br_typ = Types.empty; 
       Typed.br_branches = b; 
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       Typed.br_accept = !accept;
       Typed.br_compiled = None;
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     } 
    )
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let expr = expr noloc

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let let_decl glb p e =
  let (_,e) = expr glb e in
  { Typed.let_pat = pat glb p;
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    Typed.let_body = e;
    Typed.let_compiled = None }

(* III. Type-checks *)

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let int_cup_record = Types.cup Types.Int.any Types.Record.any


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type env = Types.descr Env.t
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open Typed

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let warning loc msg =
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  Format.fprintf !Location.warning_ppf "Warning %a:@\n%a%s@\n" 
    Location.print_loc loc
    Location.html_hilight loc
    msg
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let check loc t s msg =
  if not (Types.subtype t s) then raise_loc loc (Constraint (t, s, msg))

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let rec type_check env e constr precise = 
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(*  Format.fprintf Format.std_formatter "constr=%a precise=%b@\n"
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    Types.Print.print_descr constr precise; 
*)
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  let d = type_check' e.exp_loc env e.exp_descr constr precise in
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  e.exp_typ <- Types.cup e.exp_typ d;
  d

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and type_check' loc env e constr precise = match e with
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  | Forget (e,t) ->
      let t = Types.descr t in
      ignore (type_check env e t false);
      t
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  | Abstraction a ->
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      let t =
	try Types.Arrow.check_strenghten a.fun_typ constr 
	with Not_found -> 
	  raise_loc loc 
	  (ShouldHave
	     (constr, "but the interface of the abstraction is not compatible"))
      in
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      let env = match a.fun_name with
	| None -> env
	| Some f -> Env.add f a.fun_typ env in
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      List.iter 
	(fun (t1,t2) ->
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	   ignore (type_check_branches loc env t1 a.fun_body t2 false)
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	) a.fun_iface;
      t
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  | Match (e,b) ->
      let t = type_check env e b.br_accept true in
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      type_check_branches loc env t b constr precise
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  | Try (e,b) ->
      let te = type_check env e constr precise in
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      let tb = type_check_branches loc env Types.any b constr precise in
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      Types.cup te tb
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  | Pair (e1,e2) ->
      type_check_pair loc env e1 e2 constr precise
  | Xml (e1,e2) ->
      type_check_pair ~kind:`XML loc env e1 e2 constr precise
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  | RecordLitt r ->
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      if not (Types.Record.has_record constr) then
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	raise_loc loc (ShouldHave (constr,"but it is a record."));
      let (rconstr,res) = 
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	List.fold_left
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	  (fun (rconstr,res) (l,e) ->
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	     (* could compute (split l e) once... *)
	     let pi = Types.Record.project_opt rconstr l in
	     if Types.is_empty pi then 
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	       raise_loc loc 
		 (ShouldHave (constr,(Printf.sprintf 
					"Field %s is not allowed here."
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					(LabelPool.value l)
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				     )
			     ));
	     let t = type_check env e pi true in
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	     let rconstr = Types.Record.condition rconstr l t in
	     let res = if precise then (l,Types.cons t) :: res else res in
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	     (rconstr,res)
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	  ) (constr, []) (LabelMap.get r)
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      in
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      if not (Types.Record.has_empty_record rconstr) then
	raise_loc loc 
	  (ShouldHave (constr,"More field should be present"));
      if precise then
	Types.record' (false, LabelMap.from_list (fun _ _ -> assert false) res)
      else constr
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  | Map (e,b) ->
      let t = type_check env e (Sequence.star b.br_accept) true in

      let constr' = Sequence.approx (Types.cap Sequence.any constr) in
      let exact = Types.subtype (Sequence.star constr') constr in
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      (* Note: 
	 - could be more precise by integrating the decomposition
	 of constr inside Sequence.map.
      *)
      let res = 
	Sequence.map 
	  (fun t -> 
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	     type_check_branches loc env t b constr' (precise || (not exact)))
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	  t in
      if not exact then check loc res constr "";
      if precise then res else constr
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  | Op ("@", [e1;e2]) ->
      let constr' = Sequence.star 
		      (Sequence.approx (Types.cap Sequence.any constr)) in
      let exact = Types.subtype constr' constr in
      if exact then
	let t1 = type_check env e1 constr' precise
	and t2 = type_check env e2 constr' precise in
	if precise then Sequence.concat t1 t2 else constr
      else
	(* Note:
	   the knownledge of t1 may makes it useless to
	   check t2 with 'precise' ... *)
	let t1 = type_check env e1 constr' true
	and t2 = type_check env e2 constr' true in
	let res = Sequence.concat t1 t2 in
	check loc res constr "";
	if precise then res else constr
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  | Apply (e1,e2) ->
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(*
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      let constr' = Sequence.star 
		      (Sequence.approx (Types.cap Sequence.any constr)) in
      let t1 = type_check env e1 (Types.cup Types.Arrow.any constr') true in
      let t1_fun = Types.Arrow.get t1 in

      let has_fun = not (Types.Arrow.is_empty t1_fun)
      and has_seq = not (Types.subtype t1 Types.Arrow.any) in

      let constr' =
	Types.cap 
	  (if has_fun then Types.Arrow.domain t1_fun else Types.any)
	  (if has_seq then constr' else Types.any)
      in
      let need_arg = has_fun && Types.Arrow.need_arg t1_fun in
      let precise  = need_arg || has_seq in
      let t2 = type_check env e2 constr' precise in
      let res = Types.cup 
		  (if has_fun then 
		     if need_arg then Types.Arrow.apply t1_fun t2
		     else Types.Arrow.apply_noarg t1_fun
		   else Types.empty)
		  (if has_seq then Sequence.concat t1 t2
		   else Types.empty)
      in
      check loc res constr "";
      res
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*)
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      let t1 = type_check env e1 Types.Arrow.any true in
      let t1 = Types.Arrow.get t1 in
      let dom = Types.Arrow.domain t1 in
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      let res =
	if Types.Arrow.need_arg t1 then
	  let t2 = type_check env e2 dom true in
	  Types.Arrow.apply t1 t2
	else
	  (ignore (type_check env e2 dom false); Types.Arrow.apply_noarg t1)
      in
      check loc res constr "";
      res
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  | Op ("flatten", [e]) ->
      let constr' = Sequence.star 
		      (Sequence.approx (Types.cap Sequence.any constr)) in
      let sconstr' = Sequence.star constr' in
      let exact = Types.subtype constr' constr in
      if exact then
	let t = type_check env e sconstr' precise in
	if precise then Sequence.flatten t else constr
      else
	let t = type_check env e sconstr' true in
	let res = Sequence.flatten t in
	check loc res constr "";
	if precise then res else constr
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  | _ -> 
      let t : Types.descr = compute_type' loc env e in
      check loc t constr "";
      t

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and type_check_pair ?(kind=`Normal) loc env e1 e2 constr precise =
  let rects = Types.Product.get ~kind constr in
  if Types.Product.is_empty rects then 
    (match kind with
      | `Normal -> raise_loc loc (ShouldHave (constr,"but it is a pair."))
      | `XML -> raise_loc loc (ShouldHave (constr,"but it is an XML element.")));
  let pi1 = Types.Product.pi1 rects in
  
  let t1 = type_check env e1 (Types.Product.pi1 rects) 
	     (precise || (Types.Product.need_second rects))in
  let rects = Types.Product.restrict_1 rects t1 in
  let t2 = type_check env e2 (Types.Product.pi2 rects) precise in
  if precise then 
    match kind with
      | `Normal -> Types.times (Types.cons t1) (Types.cons t2)
      | `XML -> Types.xml (Types.cons t1) (Types.cons t2)
  else
    constr


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and compute_type env e =
  type_check env e Types.any true

and compute_type' loc env = function
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  | Var s -> 
      (try Env.find s env 
764
       with Not_found -> raise_loc loc (UnboundId (Id.value s))
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      )
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  | Cst c -> Types.constant c
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  | Dot (e,l) ->
      let t = type_check env e Types.Record.any true in
         (try (Types.Record.project t l) 
          with Not_found -> raise_loc loc (WrongLabel(t,l)))
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  | RemoveField (e,l) ->
      let t = type_check env e Types.Record.any true in
      Types.Record.remove_field t l
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  | Op (op, el) ->
      let args = List.map (fun e -> (e.exp_loc, compute_type env e)) el in
      type_op loc op args
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  | Map (e,b) ->
      let t = compute_type env e in
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      Sequence.map (fun t -> type_check_branches loc env t b Types.any true) t
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(* We keep these cases here to allow comparison and benchmarking ...
   Just comment the corresponding cases in type_check' to
   activate these ones.
*)
  | Pair (e1,e2) -> 
      let t1 = compute_type env e1 
      and t2 = compute_type env e2 in
      Types.times (Types.cons t1) (Types.cons t2)
  | RecordLitt r ->
790
      let r = LabelMap.map (fun e -> Types.cons (compute_type env e)) r in
791
      Types.record' (false,r)
792
  | _ -> assert false
793

794
and type_check_branches loc env targ brs constr precise =
795
  if Types.is_empty targ then Types.empty 
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  else (
    brs.br_typ <- Types.cup brs.br_typ targ;
798
    branches_aux loc env targ 
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      (if precise then Types.empty else constr) 
      constr precise brs.br_branches
801
  )
802
    
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804
and branches_aux loc env targ tres constr precise = function
  | [] -> raise_loc loc (NonExhaustive targ)
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810
  | b :: rem ->
      let p = b.br_pat in
      let acc = Types.descr (Patterns.accept p) in

      let targ' = Types.cap targ acc in
      if Types.is_empty targ' 
811
      then branches_aux loc env targ tres constr precise rem
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      else 
	( b.br_used <- true;
	  let res = Patterns.filter targ' p in
	  let env' = List.fold_left 
		       (fun env (x,t) -> Env.add x (Types.descr t) env) 
		       env res in
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819
	  let t = type_check env' b.br_body constr precise in
	  let tres = if precise then Types.cup t tres else tres in
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821
	  let targ'' = Types.diff targ acc in
	  if (Types.non_empty targ'') then 
822
	    branches_aux loc env targ'' tres constr precise rem 
823
824
	  else
	    tres
825
	)
826

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and type_let_decl env l =
  let acc = Types.descr (Patterns.accept l.let_pat) in
  let t = type_check env l.let_body acc true in
  let res = Patterns.filter t l.let_pat in
  List.map (fun (x,t) -> (x, Types.descr t)) res

and type_rec_funs env l =
  let types = 
    List.fold_left
      (fun accu -> function  {let_body={exp_descr=Abstraction a}} as l ->
	 let t = a.fun_typ in
	 let acc = Types.descr (Patterns.accept l.let_pat) in
	 if not (Types.subtype t acc) then
	   raise_loc l.let_body.exp_loc (NonExhaustive (Types.diff t acc));
	 let res = Patterns.filter t l.let_pat in
	 List.fold_left (fun accu (x,t) -> (x, Types.descr t)::accu) accu res
	 | _ -> assert false) [] l
  in
  let env' = List.fold_left (fun env (x,t) -> Env.add x t env) env types in
  List.iter 
    (function  { let_body = { exp_descr = Abstraction a } } as l ->
       ignore (type_check env' l.let_body Types.any false)
       | _ -> assert false) l;
  types


853
854
and type_op loc op args =
  match (op,args) with
855
    | "+", [loc1,t1; loc2,t2] ->
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	check loc1 t1 int_cup_record
	"The first argument of + must be an integer or a record";
	let int = Types.Int.get t1 in
	let int = if Intervals.is_empty int then None else Some int in
	let r = if Types.Record.has_record t1 then Some t1 else None in
	(match (int,r) with
	   | Some t1, None ->
	       if not (Types.Int.is_int t2) then
		 raise_loc loc2
		   (Constraint 
		      (t2,Types.Int.any,
		       "The second argument of + must be an integer"));
	       Types.Int.put
		 (Intervals.add t1 (Types.Int.get t2));
	   | None, Some r1 ->
	       check loc2 t2 Types.Record.any 
	       "The second argument of + must be a record";
	       Types.Record.merge r1 t2
	   | None, None ->
	       Types.empty
	   | Some t1, Some r1 ->
	       check loc2 t2 int_cup_record
	       "The second argument of + must be an integer or a record";
	       Types.cup 
		 (Types.Int.put (Intervals.add t1 (Types.Int.get t2)))
		 (Types.Record.merge r1 t2)
	)
883
884
    | "-", [loc1,t1; loc2,t2] ->
	type_int_binop Intervals.sub loc1 t1 loc2 t2
885
    | ("*" | "/" | "mod"), [loc1,t1; loc2,t2] ->
886
	type_int_binop (fun i1 i2 -> Intervals.any) loc1 t1 loc2 t2
887
    | "@", [loc1,t1; loc2,t2] ->
888
889
890
	check loc1 t1 Sequence.any
	  "The first argument of @ must be a sequence";
	Sequence.concat t1 t2
891
    | "flatten", [loc1,t1] ->
892
893
894
	check loc1 t1 Sequence.seqseq 
	  "The argument of flatten must be a sequence of sequences";
	Sequence.flatten t1
895
896
897
898
    | "load_xml", [loc1,t1] ->
	check loc1 t1 Sequence.string
	  "The argument of load_xml must be a string (filename)";
	Types.any
899
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901
902
    | "load_html", [loc1,t1] ->
	check loc1 t1 Sequence.string
	  "The argument of load_html must be a string (filename)";
	Types.any
903
904
    | "raise", [loc1,t1] ->
	Types.empty
905
906
    | "print_xml", [loc1,t1] ->
	Sequence.string
907
908
    | "print", [loc1,t1] ->
	check loc1 t1 Sequence.string
909
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912
913
914
915
916
	  "The argument of print must be a string";
	Sequence.nil_type
    | "dump_to_file", [loc1,t1; loc2,t2] ->
	check loc1 t1 Sequence.string
	  "The argument of dump_to_file must be a string (filename)";
	check loc2 t2 Sequence.string
	  "The argument of dump_to_file must be a string (value to dump)";
	Sequence.nil_type
917
918
    | "int_of", [loc1,t1] ->
	check loc1 t1 Sequence.string
919
	  "The argument of int_of must be a string";
920
921
922
	if not (Types.subtype t1 Builtin.intstr) then
	  warning loc "This application of int_of may fail";
	Types.interval Intervals.any
923
924
    | "string_of", [loc1,t1] ->
	Sequence.string
925
    | "=", [loc1,t1; loc2,t2] ->
926
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932
	(* could prevent comparision of functional value here... *)
	(* could also handle the case when t1 and t2 are the same 
	   singleton type *)
	if Types.is_empty (Types.cap t1 t2) then
	  Builtin.false_type
	else 
	  Builtin.bool
933
934
935
    | ("<=" | "<" | ">" | ">=" ), [loc1,t1; loc2,t2] ->
	(* could prevent comparision of functional value here... *)
	Builtin.bool
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946
    | _ -> assert false

and type_int_binop f loc1 t1 loc2 t2 =
  if not (Types.Int.is_int t1) then
    raise_loc loc1 
      (Constraint 
	 (t1,Types.Int.any,
	  "The first argument must be an integer"));
  if not (Types.Int.is_int t2) then
    raise_loc loc2
      (Constraint 
947
	       (t2,Types.Int.any,
948
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952
		"The second argument must be an integer"));
  Types.Int.put
    (f (Types.Int.get t1) (Types.Int.get t2));