1610 lines
50 KiB
OCaml
1610 lines
50 KiB
OCaml
(***********************************************************************)
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(* *)
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(* Objective Caml *)
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(* *)
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(* Xavier Leroy and Jerome Vouillon, projet Cristal, INRIA Rocquencourt*)
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(* *)
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(* Copyright 1996 Institut National de Recherche en Informatique et *)
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(* Automatique. Distributed only by permission. *)
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(* *)
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(***********************************************************************)
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(* $Id$ *)
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(* Operations on core types *)
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open Misc
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open Asttypes
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open Types
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open Btype
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(*
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Type manipulation after type inference
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======================================
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If one wants to manipulate a type after type inference (for
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instance, during code generation or in the debugger), one must
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first make sure that the type levels are correct, using the
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function [correct_levels]. Then, this type can be correctely
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manipulated by [apply], [expand_abbrev] and [moregeneral].
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*)
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(*
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General notes
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=============
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- As much sharing as possible should be kept : it makes types
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smaller and better abbreviated.
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When necessary, some sharing can be lost. Types will still be
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printed correctly (+++ TO DO...), and abbreviations defined by a
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class do not depend on sharing thanks to constrained
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abbreviations. (Of course, even if some sharing is lost, typing
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will still be correct.)
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- All nodes of a type have a level : that way, one know whether a
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node need to be duplicated or not when instantiating a type.
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- Levels of a type are decreasing (generic level being considered
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as greatest).
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- The level of a type constructor is superior to the binding
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time of its path.
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- Recursive types without limitation should be handled (even if
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there is still an occur check). This avoid treating specially the
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case for objects, for instance. Furthermore, the occur check
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policy can then be easily changed.
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*)
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(*
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A faire
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=======
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- Revoir affichage des types.
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- Etendre la portee d'un alias [... as 'a] a tout le type englobant.
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- #-type implementes comme de vraies abreviations.
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- Niveaux plus fins pour les identificateurs :
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Champ [global] renomme en [level];
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Niveau -1 : global
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0 : module toplevel
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1 : module contenu dans module toplevel
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...
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En fait, incrementer le niveau a chaque fois que l'on rentre dans
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un module.
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3 4 6
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\ / /
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1 2 5
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\|/
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0
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[Subst] doit ecreter les niveaux (pour qu'un variable non
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generalisable dans un module de niveau 2 ne se retrouve pas
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generalisable lorsque l'on l'utilise au niveau 0).
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- Traitement de la trace de l'unification separe de la fonction
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[unify].
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*)
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(**** Errors ****)
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exception Unify of (type_expr * type_expr) list
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exception Subtype of
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(type_expr * type_expr) list * (type_expr * type_expr) list
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exception Cannot_expand
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exception Cannot_apply
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exception Recursive_abbrev
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(**** Type level management ****)
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let current_level = ref 0
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let global_level = ref 1
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let init_def level = current_level := level
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let begin_def () = incr current_level
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let end_def () = decr current_level
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let reset_global_level () =
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global_level := !current_level + 1
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(**** Some type creators ****)
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(* Re-export generic type creators *)
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let newty desc = { desc = desc; level = !current_level }
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let newgenty = newgenty
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let new_global_ty desc = { desc = desc; level = !global_level }
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let newvar () = { desc = Tvar; level = !current_level }
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let newmarkedvar () = { desc = Tvar; level = pivot_level - !current_level }
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let newgenvar = newgenvar
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let new_global_var () = new_global_ty Tvar
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let newmarkedgenvar = newmarkedgenvar
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let newobj fields = newty (Tobject (fields, ref None))
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let none = newty (Ttuple []) (* Clearly ill-formed type *)
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(**** Representative of a type ****)
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(* Re-export repr *)
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let repr = repr
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(**********************************************)
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(* Miscellaneous operations on object types *)
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(**********************************************)
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(**** Object field manipulation. ****)
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let flatten_fields ty =
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let rec flatten l ty =
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let ty = repr ty in
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match ty.desc with
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Tfield(s, kind, ty1, ty2) ->
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begin match field_kind_repr kind with
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Fabsent ->
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flatten l ty2
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| k ->
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flatten ((s, k, ty1)::l) ty2
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end
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| _ ->
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(l, ty)
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in
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let (l, r) = flatten [] ty in
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(List.rev l, r)
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let build_fields =
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List.fold_right (fun (s, k, ty1) ty2 -> newty (Tfield(s, k, ty1, ty2)))
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let associate_fields fields1 fields2 =
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let rec associate p s s' =
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function
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(l, []) ->
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(List.rev p, (List.rev s) @ l, List.rev s')
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| ([], l') ->
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(List.rev p, List.rev s, (List.rev s') @ l')
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| ((n, k, t)::r, (n', k', t')::r') when n = n' ->
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associate ((k, t, k', t')::p) s s' (r, r')
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| ((n, k, t)::r, ((n', k', t')::_ as l')) when n < n' ->
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associate p ((n, k, t)::s) s' (r, l')
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| (((n, k, t)::r as l), (n', k', t')::r') (* when n > n' *) ->
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associate p s ((n', k', t')::s') (l, r')
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in let sort = Sort.list (fun (n, _, _) (n', _, _) -> n < n') in
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associate [] [] [] (sort fields1, sort fields2)
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(**** Check whether an object is open ****)
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(* +++ Il faudra penser a eventuellement expanser l'abreviation *)
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let rec opened_object ty =
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match (repr ty).desc with
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Tobject (t, _) -> opened_object t
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| Tfield(_, _, _, t) -> opened_object t
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| Tvar -> true
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| _ -> false
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(**** Close an object ****)
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let close_object ty =
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let rec close ty =
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let ty = repr ty in
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match ty.desc with
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Tvar -> ty.desc <- Tlink {desc = Tnil; level = ty.level}
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| Tfield(_, k, _, ty') ->
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close ty';
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let k = field_kind_repr k in
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begin match k with
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Fvar r -> r := Some Fabsent
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| _ -> ()
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end
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| Tnil -> ()
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| _ -> fatal_error "Ctype.close_object (1)"
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in
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match (repr ty).desc with
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Tobject (ty, _) -> close ty
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| Tconstr (_, _, _) -> () (* Already closed *)
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| _ -> fatal_error "Ctype.close_object (2)"
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(**** Object name manipulation ****)
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(* +++ Bientot obsolete *)
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let rec row_variable ty =
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let ty = repr ty in
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match ty.desc with
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Tfield (_, _, _, ty) -> row_variable ty
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| Tvar -> ty
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| Tnil -> raise Not_found
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| _ -> fatal_error "Ctype.row_variable"
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let set_object_name ty params id =
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match (repr ty).desc with
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Tobject (fi, nm) ->
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begin try
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nm := Some (Path.Pident id, (row_variable fi)::params)
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with Not_found ->
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()
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end
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| Tconstr (_, _, _) ->
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()
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| _ ->
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fatal_error "Ctype.set_object_name"
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let remove_object_name ty =
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match (repr ty).desc with
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Tobject (_, nm) -> nm := None
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| Tconstr (_, _, _) -> ()
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| _ -> fatal_error "Ctype.remove_object_name"
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(**** Hiding of private methods ****)
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let hide_private_methods ty =
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let ty = repr ty in
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match ty.desc with
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Tobject (f, _) ->
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let (fl, _) = flatten_fields f in
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List.iter
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(function (_, k, _) ->
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let k = field_kind_repr k in
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match k with
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Fvar r -> r := Some Fabsent
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| _ -> ())
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fl
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| _ ->
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()
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(*****************************)
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(* Type level manipulation *)
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(*****************************)
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(*
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It would be a bit more efficient to remove abbreviation expansions
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rather than generalizing them: these expansions will usually not be
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used anymore. However, this is not possible in the general case, as
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[expand_abbrev] (via [subst]) requires these expansions to be
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preserved. Does it worth duplicating this code ?
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*)
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let rec generalize ty =
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let ty = repr ty in
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if (ty.level > !current_level) && (ty.level <> generic_level) then begin
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ty.level <- generic_level;
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begin match ty.desc with
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Tconstr (_, _, abbrev) ->
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generalize_expans !abbrev
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| _ -> ()
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end;
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iter_type_expr generalize ty
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end
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and generalize_expans =
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function
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Mnil -> ()
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| Mcons(_, ty, rem) -> generalize ty; generalize_expans rem
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| Mlink rem -> generalize_expans !rem
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let expand_abbrev' = (* Forward declaration *)
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ref (fun env path args abbrev level -> raise Cannot_expand)
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(*
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Lower the levels of a type (assume [level] is not
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[generic_level]).
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*)
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(*
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The level of a type constructor must be greater than its binding
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time. That way, a type constructor cannot escape the scope of its
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definition, as would be the case in
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let x = ref []
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module M = struct type t let _ = (x : t list ref) end
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(without this constraint, the type system would actually be unsound.)
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*)
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let rec update_level env level ty =
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let ty = repr ty in
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if ty.level > level then begin
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let old_level = ty.level in
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ty.level <- level;
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begin match ty.desc with
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Tconstr(p, tl, abbrev) when level < Path.binding_time p ->
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(* Try first to replace an abbreviation by its expansion. *)
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begin try
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ty.desc <- Tlink (!expand_abbrev' env p tl abbrev old_level);
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update_level env level ty
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with Cannot_expand ->
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(* +++ Levels should be restored... *)
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raise (Unify [])
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end
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| _ ->
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iter_type_expr (update_level env level) ty
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end
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end
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(*
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Function [update_level] will never try to expand an abbreviation in
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this case ([current_level] is greater than the binding time of any
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type constructor path). So, it can be called with the empty
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environnement.
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*)
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let make_nongen ty = update_level Env.empty !current_level ty
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(* Correct the levels of type [ty]. *)
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let correct_levels ty =
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Subst.type_expr Subst.identity ty
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(*******************)
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(* Instantiation *)
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(*******************)
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(*
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Generic nodes are duplicated, while non-generic nodes are left
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as-is.
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During instantiation, the description of a generic node is first
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replaced by a link to a stub ([Tlink (newmarkedvar ())]). Once the
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copy is made, it replaces the stub.
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After instantiation, the description of generic node, which was
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stored by [save_desc], must be put back, using [cleanup_types].
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Marked on the copy are removed by [unmark].
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*)
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let abbreviations = ref (ref Mnil)
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(* Abbreviation memorized. *)
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let rec copy ty =
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let ty = repr ty in
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if ty.level <> generic_level then
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ty
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else begin
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let desc = ty.desc in
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save_desc ty desc;
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let t = newmarkedvar () in (* Stub *)
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ty.desc <- Tlink t;
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t.desc <-
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begin match desc with
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Tvar ->
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Tvar
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| Tarrow (t1, t2) ->
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Tarrow (copy t1, copy t2)
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| Ttuple tl ->
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Ttuple (List.map copy tl)
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| Tconstr (p, tl, _) ->
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(*
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One must allocate a new reference, so that abbrevia-
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tions belonging to different branches of a type are
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independent.
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Moreover, a reference containing a [Mcons] must be
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shared, so that the memorized expansion of an abbrevi-
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ation can be released by changing the content of just
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one reference.
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*)
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Tconstr (p, List.map copy tl,
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ref (match ! !abbreviations with
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Mcons _ -> Mlink !abbreviations
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| abbrev -> abbrev))
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| Tobject (t1, {contents = name}) ->
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let name' =
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match name with
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None ->
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None
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| Some (p, tl) ->
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Some (p, List.map copy tl)
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in
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Tobject (copy t1, ref name')
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| Tfield (label, kind, t1, t2) ->
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begin match field_kind_repr kind with
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Fpresent ->
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Tfield (label, Fpresent, copy t1, copy t2)
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| _ ->
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Tlink (copy t2)
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end
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| Tnil ->
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Tnil
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| Tlink t -> (* Actually unused *)
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Tlink (copy t)
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end;
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t
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end
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(**** Variants of instantiations ****)
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let instance sch =
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let ty = copy sch in
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cleanup_types ();
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unmark_type ty;
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ty
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let instance_list schl =
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let tyl = List.map copy schl in
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cleanup_types ();
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List.iter unmark_type tyl;
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tyl
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let instance_constructor cstr =
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let ty_res = copy cstr.cstr_res in
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let ty_args = List.map copy cstr.cstr_args in
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cleanup_types ();
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List.iter unmark_type ty_args; unmark_type ty_res;
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(ty_args, ty_res)
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let instance_label lbl =
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let ty_res = copy lbl.lbl_res in
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let ty_arg = copy lbl.lbl_arg in
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cleanup_types ();
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unmark_type ty_arg; unmark_type ty_res;
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(ty_arg, ty_res)
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let instance_parameterized_type sch_args sch =
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let ty_args = List.map copy sch_args in
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let ty = copy sch in
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cleanup_types ();
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List.iter unmark_type ty_args; unmark_type ty;
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(ty_args, ty)
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let instance_parameterized_type_2 sch_args sch_lst sch =
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let ty_args = List.map copy sch_args in
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let ty_lst = List.map copy sch_lst in
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let ty = copy sch in
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cleanup_types ();
|
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List.iter unmark_type ty_args; List.iter unmark_type ty_lst;
|
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unmark_type ty;
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(ty_args, ty_lst, ty)
|
||
|
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let instance_class cl =
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let params = List.map copy cl.cty_params in
|
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let args = List.map copy cl.cty_args in
|
||
let vars = Vars.map (function (mut, ty) -> (mut, copy ty)) cl.cty_vars in
|
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let mets = Meths.map copy cl.cty_meths in
|
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let self = copy cl.cty_self in
|
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cleanup_types ();
|
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List.iter unmark_type params; List.iter unmark_type args;
|
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Vars.iter (fun l (m, t) -> unmark_type t) vars;
|
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Meths.iter (fun l t -> unmark_type t) mets;
|
||
unmark_type self;
|
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(params, args, vars, mets, self)
|
||
|
||
(**** Instantiation with parameter substitution ****)
|
||
|
||
let unify' = (* Forward declaration *)
|
||
ref (fun env ty1 ty2 -> raise (Unify []))
|
||
|
||
let rec subst env level abbrev path params args body =
|
||
let old_level = !current_level in
|
||
current_level := level;
|
||
try
|
||
let body0 = newvar () in (* Stub *)
|
||
begin match path with
|
||
None -> ()
|
||
| Some path -> memorize_abbrev abbrev path body0
|
||
end;
|
||
abbreviations := abbrev;
|
||
let (params', body') = instance_parameterized_type params body in
|
||
abbreviations := ref Mnil;
|
||
!unify' env body0 body';
|
||
List.iter2 (!unify' env) params' args;
|
||
current_level := old_level;
|
||
body'
|
||
with Unify _ as exn ->
|
||
current_level := old_level;
|
||
raise exn
|
||
|
||
(*
|
||
Only the shape of the type matters, not whether is is generic or
|
||
not. [generic_level] might be somewhat slower, but it ensures
|
||
invariants on types are enforced (decreasing levels.), and we don't
|
||
care about efficiency here.
|
||
*)
|
||
let apply env params body args =
|
||
try
|
||
subst env generic_level (ref Mnil) None params args body
|
||
with
|
||
Unify _ -> raise Cannot_apply
|
||
|
||
|
||
(****************************)
|
||
(* Abbreviation expansion *)
|
||
(****************************)
|
||
|
||
|
||
(* Search whether the expansion has been memorized. *)
|
||
let rec find_expans p1 =
|
||
function
|
||
Mnil ->
|
||
None
|
||
| Mcons (p2, ty, _) when Path.same p1 p2 ->
|
||
Some ty
|
||
| Mcons (_, _, rem) ->
|
||
find_expans p1 rem
|
||
| Mlink {contents = rem} ->
|
||
find_expans p1 rem
|
||
|
||
let previous_env = ref Env.empty
|
||
|
||
(* Expand an abbreviation. The expansion is memorized. *)
|
||
(*
|
||
Assume the level is greater than the path binding time of the
|
||
expanded abbreviation.
|
||
*)
|
||
(*
|
||
An abbreviation expansion will fail in either of these cases:
|
||
1. The type constructor does not correspond to a manifest type.
|
||
2. The type constructor is defined in an external file, and this
|
||
file is not in the path (missing -I options).
|
||
3. The type constructor is not in the "local" environment. This can
|
||
happens when a non-generic type variable has been instantiated
|
||
afterwards to the not yet defined type constructor. (Actually,
|
||
this cannot happen at the moment due to the strong constraints
|
||
between type levels and constructor binding time.)
|
||
4. The expansion requires the expansion of another abbreviation,
|
||
and this other expansion fails.
|
||
*)
|
||
let expand_abbrev env path args abbrev level =
|
||
(*
|
||
If the environnement has changed, memorized expansions might not
|
||
be correct anymore, and so we flush the cache. This is safe but
|
||
quite pessimistic: it would be enough to flush the cache at the
|
||
ends of structures and signatures.
|
||
+++ Do it !
|
||
*)
|
||
if env != !previous_env then begin
|
||
cleanup_abbrev ();
|
||
previous_env := env
|
||
end;
|
||
match find_expans path !abbrev with
|
||
Some ty ->
|
||
if level <> generic_level then
|
||
update_level env level ty;
|
||
ty
|
||
| None ->
|
||
let (params, body) =
|
||
try Env.find_type_expansion path env with Not_found ->
|
||
raise Cannot_expand
|
||
in
|
||
try
|
||
subst env level abbrev (Some path) params args body
|
||
with Unify _ -> raise Cannot_expand
|
||
|
||
let _ = expand_abbrev' := expand_abbrev
|
||
|
||
(* Fully expand the head of a type. *)
|
||
let rec expand_head env ty =
|
||
let ty = repr ty in
|
||
match ty.desc with
|
||
Tconstr(p, tl, abbrev) ->
|
||
begin try
|
||
expand_head env (expand_abbrev env p tl abbrev ty.level)
|
||
with Cannot_expand ->
|
||
ty
|
||
end
|
||
| _ ->
|
||
ty
|
||
|
||
(* Recursively expand the head of a type.
|
||
Also expand #-types. *)
|
||
let rec full_expand env ty =
|
||
let ty = repr (expand_head env ty) in
|
||
match ty.desc with
|
||
Tobject (fi, {contents = Some (_, v::_)}) when (repr v).desc = Tvar ->
|
||
{ desc = Tobject (fi, ref None); level = ty.level }
|
||
| _ ->
|
||
ty
|
||
|
||
(*
|
||
Check whether the abbreviation expands to a well-defined type.
|
||
During the typing of a class, abbreviations for correspondings
|
||
types expand to non-generic types.
|
||
*)
|
||
let generic_abbrev env path =
|
||
try
|
||
let (_, body) = Env.find_type_expansion path env in
|
||
(repr body).level = generic_level
|
||
with
|
||
Not_found ->
|
||
false
|
||
|
||
|
||
(*****************)
|
||
(* Occur check *)
|
||
(*****************)
|
||
|
||
|
||
exception Occur
|
||
|
||
(* The marks are already used by [expand_abbrev]... *)
|
||
let visited = ref []
|
||
|
||
let rec non_recursive_abbrev env ty =
|
||
let ty = repr ty in
|
||
if ty == none then raise Recursive_abbrev;
|
||
if not (List.memq ty !visited) then begin
|
||
let level = ty.level in
|
||
visited := ty :: !visited;
|
||
match ty.desc with
|
||
Tconstr(p, args, abbrev) ->
|
||
begin try
|
||
non_recursive_abbrev env (expand_abbrev env p args abbrev level)
|
||
with Cannot_expand ->
|
||
iter_type_expr (non_recursive_abbrev env) ty
|
||
end
|
||
| Tobject (_, _) ->
|
||
()
|
||
| _ ->
|
||
iter_type_expr (non_recursive_abbrev env) ty
|
||
end
|
||
|
||
let correct_abbrev env ident params ty =
|
||
visited := [];
|
||
non_recursive_abbrev env
|
||
(subst env generic_level (ref (Mcons (Path.Pident ident, none, Mnil))) None
|
||
[] [] ty);
|
||
visited := []
|
||
|
||
let occur env ty0 ty =
|
||
let rec occur_rec ty =
|
||
if ty == ty0 then raise Occur;
|
||
if ty.level >= lowest_level then
|
||
match ty.desc with
|
||
Tlink ty' ->
|
||
occur_rec ty'
|
||
| Tconstr(p, tl, abbrev) ->
|
||
ty.level <- pivot_level - ty.level;
|
||
begin try
|
||
iter_type_expr occur_rec ty
|
||
with Occur -> try
|
||
occur_rec (expand_abbrev env p tl abbrev ty.level)
|
||
with Cannot_expand ->
|
||
raise Occur
|
||
end
|
||
| Tobject (_, _) ->
|
||
()
|
||
| _ ->
|
||
ty.level <- pivot_level - ty.level;
|
||
iter_type_expr occur_rec ty
|
||
in
|
||
try
|
||
occur_rec ty; unmark_type ty
|
||
with Occur ->
|
||
unmark_type ty; raise Occur
|
||
|
||
|
||
(*****************)
|
||
(* Unification *)
|
||
(*****************)
|
||
|
||
|
||
|
||
(**** Transform error trace ****)
|
||
(* +++ Move it to some other place ? *)
|
||
|
||
let expand_trace env trace =
|
||
List.fold_right
|
||
(fun (t1, t2) rem ->
|
||
(repr t1, full_expand env t1)::(repr t2, full_expand env t2)::rem)
|
||
trace []
|
||
|
||
let rec filter_trace =
|
||
function
|
||
(t1, t1')::(t2, t2')::rem ->
|
||
let rem' = filter_trace rem in
|
||
if (t1 == t1') & (t2 == t2')
|
||
then rem'
|
||
else (t1, t1')::(t2, t2')::rem'
|
||
| _ ->
|
||
[]
|
||
|
||
(**** Unification ****)
|
||
|
||
(* Return whether [t0] occurs in [ty]. Objects are also traversed. *)
|
||
let deep_occur t0 ty =
|
||
let rec occur_rec ty =
|
||
let ty = repr ty in
|
||
if ty.level >= lowest_level then begin
|
||
if ty == t0 then raise Occur;
|
||
ty.level <- pivot_level - ty.level;
|
||
iter_type_expr occur_rec ty
|
||
end
|
||
in
|
||
try
|
||
occur_rec ty; unmark_type ty; false
|
||
with Occur ->
|
||
unmark_type ty; true
|
||
|
||
(*
|
||
1. When unifying two non-abbreviated types, one type is made a link
|
||
to the other. When unifying an abbreviated type with a
|
||
non-abbreviated type, the non-abbreviated type is made a link to
|
||
the other one. When unifying to abbreviated types, these two
|
||
types are kept distincts, but they are made to (temporally)
|
||
expand to the same type.
|
||
2. Abbreviations with at least one parameter are systematically
|
||
expanded. The overhead does not seem to high, and that way
|
||
abbreviations where some parameters does not appear in the
|
||
expansion, such as ['a t = int], are correctly handled. In
|
||
particular, for this example, unifying ['a t] with ['b t] keeps
|
||
['a] and ['b] distincts. (Is it really important ?)
|
||
3. Unifying an abbreviation ['a t = 'a] with ['a] should not yield
|
||
['a t as 'a]. Indeed, the type variable would otherwise be lost.
|
||
This problem occurs for abbreviations expanding to a type
|
||
variable, but also to many other constrained abbreviations (for
|
||
instance, [(< x : 'a > -> unit) t = <x : 'a>]). The solution is
|
||
that, if an abbreviation is unified with some subpart of its
|
||
parameters, then the parameter actually does not get
|
||
abbreviated. It would be possible to check whether some
|
||
information is indeed lost, but it probably does not worth it.
|
||
*)
|
||
let rec unify env t1 t2 =
|
||
(* First step: special cases (optimizations) *)
|
||
if t1 == t2 then () else
|
||
let t1 = repr t1 in
|
||
let t2 = repr t2 in
|
||
if t1 == t2 then () else
|
||
|
||
try
|
||
match (t1.desc, t2.desc) with
|
||
(Tvar, Tconstr _) when deep_occur t1 t2 ->
|
||
unify2 env t1 t2
|
||
| (Tconstr _, Tvar) when deep_occur t2 t1 ->
|
||
unify2 env t1 t2
|
||
| (Tvar, _) ->
|
||
begin try occur env t1 t2 with Occur ->
|
||
raise (Unify [])
|
||
end;
|
||
update_level env t1.level t2;
|
||
t1.desc <- Tlink t2
|
||
| (_, Tvar) ->
|
||
begin try occur env t2 t1 with Occur ->
|
||
raise (Unify [])
|
||
end;
|
||
update_level env t2.level t1;
|
||
t2.desc <- Tlink t1
|
||
| (Tconstr (p1, [], _), Tconstr (p2, [], _)) when Path.same p1 p2 ->
|
||
update_level env t1.level t2;
|
||
t1.desc <- Tlink t2
|
||
| _ ->
|
||
unify2 env t1 t2
|
||
with Unify trace ->
|
||
raise (Unify ((t1, t2)::trace))
|
||
|
||
and unify2 env t1 t2 =
|
||
(* Second step: expansion of abbreviations *)
|
||
let t1' = expand_head env t1 in
|
||
let t2' = expand_head env t2 in
|
||
(* Expansion may have changed the representative of the types... *)
|
||
let t1' = repr t1' and t2' = repr t2' in
|
||
if t1' == t2' then () else
|
||
|
||
let t1 = repr t1 and t2 = repr t2 in
|
||
if (t1 == t1') || (t2 != t2') then
|
||
unify3 env t1 t1' t2 t2'
|
||
else
|
||
try unify3 env t2 t2' t1 t1' with Unify trace ->
|
||
raise (Unify (List.map (fun (x, y) -> (y, x)) trace))
|
||
|
||
and unify3 env t1 t1' t2 t2' =
|
||
(* Third step: truly unification *)
|
||
(* Assumes either [t1 == t1'] or [t2 != t2'] *)
|
||
let d1 = t1'.desc and d2 = t2'.desc in
|
||
|
||
if (t2 != t2') && (deep_occur t1' t2) then begin
|
||
(* See point 3. *)
|
||
update_level env t1'.level t2';
|
||
t1'.desc <- Tlink t2'
|
||
end else begin
|
||
update_level env t1'.level t2;
|
||
t1'.desc <- Tlink t2
|
||
end;
|
||
|
||
try
|
||
begin match (d1, d2) with
|
||
(Tvar, _) ->
|
||
begin try occur env t1' t2 with Occur ->
|
||
raise (Unify [])
|
||
end
|
||
| (_, Tvar) ->
|
||
begin try occur env t2' (newty d1) with Occur ->
|
||
raise (Unify [])
|
||
end;
|
||
if t1 == t1' then begin
|
||
(* The variable must be instantiated... *)
|
||
let ty = {desc = d1; level = t1'.level} in
|
||
update_level env t2'.level ty;
|
||
t2'.desc <- Tlink ty
|
||
end else begin
|
||
t1'.desc <- d1;
|
||
update_level env t2'.level t1;
|
||
t2'.desc <- Tlink t1
|
||
end
|
||
| (Tarrow (t1, u1), Tarrow (t2, u2)) ->
|
||
unify env t1 t2; unify env u1 u2
|
||
| (Ttuple tl1, Ttuple tl2) ->
|
||
unify_list env tl1 tl2
|
||
| (Tconstr (p1, tl1, _), Tconstr (p2, tl2, _)) when Path.same p1 p2 ->
|
||
unify_list env tl1 tl2
|
||
| (Tobject (fi1, nm1), Tobject (fi2, _)) ->
|
||
unify_fields env fi1 fi2;
|
||
(* Type [t2'] may have been instantiated by [unify_fields] *)
|
||
(* XXX One should do some kind of unification... *)
|
||
begin match (repr t2').desc with
|
||
Tobject (_, {contents = Some (_, va::_)})
|
||
when (repr va).desc = Tvar ->
|
||
()
|
||
| Tobject (_, nm2) ->
|
||
nm2 := !nm1
|
||
| _ ->
|
||
()
|
||
end
|
||
| (Tfield _, Tfield _) -> (* Actually unused *)
|
||
unify_fields env t1' t2'
|
||
| (Tfield (_, kind, _, t1''), _) ->
|
||
unify_kind kind Fabsent;
|
||
unify env t1'' t2'
|
||
| (_, Tfield (_, kind, _, t2'')) ->
|
||
unify_kind kind Fabsent;
|
||
unify env t1' t2''
|
||
| (Tnil, Tnil) ->
|
||
()
|
||
| (_, _) ->
|
||
raise (Unify [])
|
||
end
|
||
(*
|
||
(*
|
||
Can only be done afterwards, once the row variable has
|
||
(possibly) been instantiated.
|
||
*)
|
||
if t1 != t1' (* && t2 != t2' *) then begin
|
||
match (t1.desc, t2.desc) with
|
||
(Tconstr (p, ty::_, _), _)
|
||
when ((repr ty).desc <> Tvar)
|
||
&& weak_abbrev p
|
||
&& not (deep_occur t1 t2) ->
|
||
update_level env t1.level t2;
|
||
t1.desc <- Tlink t2
|
||
| (_, Tconstr (p, ty::_, _))
|
||
when ((repr ty).desc <> Tvar)
|
||
&& weak_abbrev p
|
||
&& not (deep_occur t2 t1) ->
|
||
update_level env t2.level t1;
|
||
t2.desc <- Tlink t1;
|
||
t1'.desc <- Tlink t2'
|
||
| _ ->
|
||
()
|
||
end
|
||
*)
|
||
with Unify trace ->
|
||
t1'.desc <- d1;
|
||
raise (Unify trace)
|
||
|
||
and unify_list env tl1 tl2 =
|
||
if List.length tl1 <> List.length tl2 then
|
||
raise (Unify []);
|
||
List.iter2 (unify env) tl1 tl2
|
||
|
||
and unify_fields env ty1 ty2 = (* Optimization *)
|
||
let (fields1, rest1) = flatten_fields ty1
|
||
and (fields2, rest2) = flatten_fields ty2 in
|
||
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
|
||
let va = newvar () in
|
||
unify env rest1 (build_fields miss2 va);
|
||
unify env (build_fields miss1 va) rest2;
|
||
List.iter (fun (k1, t1, k2, t2) -> unify_kind k1 k2; unify env t1 t2) pairs
|
||
|
||
and unify_kind k1 k2 =
|
||
let k1 = field_kind_repr k1 in
|
||
let k2 = field_kind_repr k2 in
|
||
match k1, k2 with
|
||
(Fvar r, _) -> r := Some k2
|
||
| (_, Fvar r) -> r := Some k1
|
||
| (Fabsent, Fabsent) | (Fpresent, Fpresent) -> ()
|
||
| _ -> raise (Unify [])
|
||
|
||
let unify env ty1 ty2 =
|
||
try
|
||
unify env ty1 ty2
|
||
with Unify trace ->
|
||
let trace = expand_trace env trace in
|
||
match trace with
|
||
t1::t2::rem ->
|
||
raise (Unify (t1::t2::filter_trace rem))
|
||
| _ ->
|
||
fatal_error "Ctype.unify"
|
||
|
||
let _ = unify' := unify
|
||
|
||
(**** Special cases of unification ****)
|
||
|
||
(* Unify [t] and ['a -> 'b]. Return ['a] and ['b]. *)
|
||
let rec filter_arrow env t =
|
||
let t = repr t in
|
||
match t.desc with
|
||
Tvar ->
|
||
let t1 = newvar () and t2 = newvar () in
|
||
let t' = newty (Tarrow (t1, t2)) in
|
||
update_level env t.level t';
|
||
t.desc <- Tlink t';
|
||
(t1, t2)
|
||
| Tarrow(t1, t2) ->
|
||
(t1, t2)
|
||
| Tconstr(p, tl, abbrev) ->
|
||
begin try
|
||
filter_arrow env (expand_abbrev env p tl abbrev t.level)
|
||
with Cannot_expand ->
|
||
raise (Unify [])
|
||
end
|
||
| _ ->
|
||
raise (Unify [])
|
||
|
||
(* Used by [filter_method]. *)
|
||
let rec filter_method_field env name priv ty =
|
||
let ty = repr ty in
|
||
match ty.desc with
|
||
Tvar ->
|
||
let ty1 = newvar () and ty2 = newvar () in
|
||
let ty' = newty (Tfield (name,
|
||
begin match priv with
|
||
Private -> Fvar (ref None)
|
||
| Public -> Fpresent
|
||
end,
|
||
ty1, ty2))
|
||
in
|
||
update_level env ty.level ty';
|
||
ty.desc <- Tlink ty';
|
||
ty1
|
||
| Tfield(n, kind, ty1, ty2) ->
|
||
let kind = field_kind_repr kind in
|
||
if (n = name) && (kind <> Fabsent) then begin
|
||
if priv = Public then
|
||
unify_kind kind Fpresent;
|
||
ty1
|
||
end else
|
||
filter_method_field env name priv ty2
|
||
| _ when priv = Private ->
|
||
newvar ()
|
||
| _ ->
|
||
raise (Unify [])
|
||
|
||
(* Unify [ty] and [< name : 'a; .. >]. Return ['a]. *)
|
||
let rec filter_method env name priv ty =
|
||
let ty = repr ty in
|
||
match ty.desc with
|
||
Tvar ->
|
||
let ty1 = newvar () in
|
||
let ty' = newobj ty1 in
|
||
update_level env ty.level ty';
|
||
ty.desc <- Tlink ty';
|
||
filter_method_field env name priv ty1
|
||
| Tobject(f, _) ->
|
||
filter_method_field env name priv f
|
||
| Tconstr(p, tl, abbrev) ->
|
||
begin try
|
||
filter_method env name priv (expand_abbrev env p tl abbrev ty.level)
|
||
with Cannot_expand ->
|
||
raise (Unify [])
|
||
end
|
||
| _ ->
|
||
raise (Unify [])
|
||
|
||
|
||
(***********************************)
|
||
(* Matching between type schemes *)
|
||
(***********************************)
|
||
|
||
(*
|
||
Update the level of [ty]. First check that the levels of variables
|
||
from the subject are not lowered.
|
||
*)
|
||
let moregen_occur env level ty =
|
||
let rec occur ty =
|
||
let ty = repr ty in
|
||
if ty.level > level then begin
|
||
if ty.desc = Tvar then raise Occur;
|
||
ty.level <- pivot_level - ty.level;
|
||
iter_type_expr occur ty
|
||
end
|
||
in
|
||
begin try
|
||
occur ty; unmark_type ty
|
||
with Occur ->
|
||
unmark_type ty; raise (Unify [])
|
||
end;
|
||
update_level env level ty
|
||
|
||
(*
|
||
Non-generic variable can be instanciated only if [inst_nongen] is
|
||
true. So, [inst_nongen] should be set to false if the subject might
|
||
contain non-generic variables.
|
||
Usually, the subject is given by the user, and the pattern
|
||
is unimportant. So, no need to propagate abbreviations.
|
||
*)
|
||
let moregeneral env inst_nongen pat_sch subj_sch =
|
||
let type_pairs = ref [] in
|
||
|
||
let rec moregen env t1 t2 =
|
||
if t1 == t2 then () else
|
||
let t1 = repr t1 in
|
||
let t2 = repr t2 in
|
||
if t1 == t2 then () else
|
||
|
||
match (t1.desc, t2.desc) with
|
||
(Tvar, _) when if inst_nongen then t1.level <> generic_level - 1
|
||
else t1.level = generic_level ->
|
||
moregen_occur env t1.level t2;
|
||
t1.desc <- Tlink t2
|
||
| (Tconstr (p1, [], _), Tconstr (p2, [], _)) when Path.same p1 p2 ->
|
||
()
|
||
| _ ->
|
||
let t1' = expand_head env t1 in
|
||
let t2' = expand_head env t2 in
|
||
(* Expansion may have changed the representative of the types... *)
|
||
let t1' = repr t1' and t2' = repr t2' in
|
||
if t1' == t2' then () else
|
||
if
|
||
List.exists (function (t1, t2) -> t1 == t1' && t2 == t2') !type_pairs
|
||
then
|
||
()
|
||
else begin
|
||
type_pairs := (t1', t2') :: !type_pairs;
|
||
|
||
match (t1'.desc, t2'.desc) with
|
||
(Tvar, _) when if inst_nongen then t1'.level <> generic_level - 1
|
||
else t1'.level = generic_level ->
|
||
moregen_occur env t1'.level t2;
|
||
t1'.desc <- Tlink t2
|
||
| (Tarrow (t1, u1), Tarrow (t2, u2)) ->
|
||
moregen env t1 t2; moregen env u1 u2
|
||
| (Ttuple tl1, Ttuple tl2) ->
|
||
moregen_list env tl1 tl2
|
||
| (Tconstr (p1, tl1, _), Tconstr (p2, tl2, _))
|
||
when Path.same p1 p2 ->
|
||
moregen_list env tl1 tl2
|
||
| (Tobject (fi1, nm1), Tobject (fi2, nm2)) ->
|
||
moregen_fields env fi1 fi2
|
||
| (Tfield _, Tfield _) -> (* Actually unused *)
|
||
moregen_fields env t1' t2'
|
||
| (Tfield (_, kind, _, t1''), _) ->
|
||
moregen_kind kind Fabsent;
|
||
moregen env t1'' t2'
|
||
| (_, Tfield (_, kind, _, t2'')) ->
|
||
moregen_kind Fabsent kind;
|
||
moregen env t1' t2''
|
||
| (Tnil, Tnil) ->
|
||
()
|
||
| (_, _) ->
|
||
raise (Unify [])
|
||
end
|
||
|
||
and moregen_list env tl1 tl2 =
|
||
if List.length tl1 <> List.length tl2 then
|
||
raise (Unify []);
|
||
List.iter2 (moregen env) tl1 tl2
|
||
|
||
and moregen_fields env ty1 ty2 =
|
||
let (fields1, rest1) = flatten_fields ty1
|
||
and (fields2, rest2) = flatten_fields ty2 in
|
||
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
|
||
if miss1 <> [] then raise (Unify []);
|
||
moregen env rest1 (build_fields miss2 rest2);
|
||
List.iter
|
||
(fun (k1, t1, k2, t2) -> moregen_kind k1 k2; moregen env t1 t2)
|
||
pairs
|
||
|
||
and moregen_kind level k1 k2 =
|
||
let k1 = field_kind_repr k1 in
|
||
let k2 = field_kind_repr k2 in
|
||
match k1, k2 with
|
||
(Fvar r, _) -> r := Some k2
|
||
| (Fabsent, Fabsent) | (Fpresent, Fpresent) -> ()
|
||
| _ -> raise (Unify [])
|
||
|
||
in
|
||
let old_level = !current_level in
|
||
current_level := generic_level - 1;
|
||
(*
|
||
Generic variables are first duplicated with [instance]. So,
|
||
their levels are lowered to [generic_level - 1]. The subject is
|
||
then copied with [correct_levels]. That way, its levels won't be
|
||
changed.
|
||
*)
|
||
let subj = correct_levels (instance subj_sch) in
|
||
current_level := generic_level;
|
||
(* Duplicate generic variables *)
|
||
let patt = instance pat_sch in
|
||
let res = try moregen env patt subj; true with Unify _ -> false in
|
||
current_level := old_level;
|
||
res
|
||
|
||
|
||
(*********************************************)
|
||
(* Equivalence between parameterized types *)
|
||
(*********************************************)
|
||
|
||
|
||
(* Two modes: with or without renaming of variables *)
|
||
|
||
let equal env rename tyl1 tyl2 =
|
||
let subst = ref [] in
|
||
let type_pairs = ref [] in
|
||
|
||
let rec eqtype t1 t2 =
|
||
if t1 == t2 then true else
|
||
let t1 = repr t1 in
|
||
let t2 = repr t2 in
|
||
if t1 == t2 then true else
|
||
match (t1.desc, t2.desc) with
|
||
| (Tvar, Tvar) when rename ->
|
||
begin try
|
||
List.assq t1 !subst == t2
|
||
with Not_found ->
|
||
subst := (t1, t2) :: !subst;
|
||
true
|
||
end
|
||
| (Tconstr (p1, [], _), Tconstr (p2, [], _)) when Path.same p1 p2 ->
|
||
true
|
||
| _ ->
|
||
let t1 = expand_head env t1 in
|
||
let t2 = expand_head env t2 in
|
||
(* Expansion may have changed the representative of the types... *)
|
||
let t1 = repr t1 and t2 = repr t2 in
|
||
if t1 == t2 then true else
|
||
List.exists (function (t1', t2') -> t1 == t1' & t2 == t2') !type_pairs
|
||
(* XXX Possibly slow... *)
|
||
||
|
||
begin
|
||
type_pairs := (t1, t2) :: !type_pairs;
|
||
match (t1.desc, t2.desc) with
|
||
(Tvar, Tvar) when rename ->
|
||
begin try
|
||
List.assq t1 !subst == t2
|
||
with Not_found ->
|
||
subst := (t1, t2) :: !subst;
|
||
true
|
||
end
|
||
| (Tarrow (t1, u1), Tarrow (t2, u2)) ->
|
||
eqtype t1 t2 && eqtype u1 u2
|
||
| (Ttuple tl1, Ttuple tl2) ->
|
||
eqtype_list tl1 tl2
|
||
| (Tconstr (p1, tl1, _), Tconstr (p2, tl2, _))
|
||
when Path.same p1 p2 ->
|
||
eqtype_list tl1 tl2
|
||
| (Tobject (fi1, nm1), Tobject (fi2, nm2)) ->
|
||
eqtype_fields fi1 fi2
|
||
| (Tfield _, Tfield _) -> (* Actually unused *)
|
||
eqtype_fields t1 t2
|
||
| (Tfield (_, kind, _, t1'), _)
|
||
when field_kind_repr kind = Fabsent ->
|
||
eqtype t1' t2
|
||
| (_, Tfield (_, kind, _, t2'))
|
||
when field_kind_repr kind = Fabsent ->
|
||
eqtype t1 t2'
|
||
| (Tnil, Tnil) ->
|
||
true
|
||
| (_, _) ->
|
||
false
|
||
end
|
||
|
||
and eqtype_list tl1 tl2 =
|
||
List.length tl1 = List.length tl2
|
||
&&
|
||
List.for_all2 eqtype tl1 tl2
|
||
|
||
and eqtype_fields ty1 ty2 = (* Optimization *)
|
||
let (fields1, rest1) = flatten_fields ty1
|
||
and (fields2, rest2) = flatten_fields ty2 in
|
||
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
|
||
eqtype rest1 rest2
|
||
&&
|
||
(miss1 = []) && (miss2 = [])
|
||
&&
|
||
List.for_all (function (k1, t1, k2, t2) -> eqtype t1 t2) pairs
|
||
|
||
in
|
||
eqtype_list tyl1 tyl2
|
||
|
||
|
||
(***************)
|
||
(* Subtyping *)
|
||
(***************)
|
||
|
||
|
||
(**** Build a subtype of a given type. ****)
|
||
|
||
let subtypes = ref []
|
||
|
||
(* XXX Types r<>cursifs ? *)
|
||
let rec build_subtype env t =
|
||
let t = repr t in
|
||
match t.desc with
|
||
Tlink t' -> (* Redundant ! *)
|
||
build_subtype env t'
|
||
| Tvar ->
|
||
(t, false)
|
||
| Tarrow(t1, t2) ->
|
||
let (t1', c1) = (t1, false) in
|
||
let (t2', c2) = build_subtype env t2 in
|
||
if c1 or c2 then (new_global_ty (Tarrow(t1', t2')), true)
|
||
else (t, false)
|
||
| Ttuple tlist ->
|
||
let (tlist', clist) =
|
||
List.split (List.map (build_subtype env) tlist)
|
||
in
|
||
if List.exists (function c -> c) clist then
|
||
(new_global_ty (Ttuple tlist'), true)
|
||
else (t, false)
|
||
| Tconstr(p, tl, abbrev) when generic_abbrev env p ->
|
||
let t' = expand_abbrev env p tl abbrev t.level in
|
||
let (t'', c) = build_subtype env t' in
|
||
if c then (t'', true)
|
||
else (t, false)
|
||
| Tconstr(p, tl, abbrev) ->
|
||
(t, false)
|
||
| Tobject (t1, _) when opened_object t1 ->
|
||
(t, false)
|
||
| Tobject (t1, _) ->
|
||
(begin try
|
||
List.assq t !subtypes
|
||
with Not_found ->
|
||
let t' = new_global_var () in
|
||
subtypes := (t, t')::!subtypes;
|
||
let (t1', _) = build_subtype env t1 in
|
||
t'.desc <- Tobject (t1', ref None);
|
||
t'
|
||
end,
|
||
true)
|
||
| Tfield(s, _, t1, t2) (* Always present *) ->
|
||
let (t1', _) = build_subtype env t1 in
|
||
let (t2', _) = build_subtype env t2 in
|
||
(new_global_ty (Tfield(s, Fpresent, t1', t2')), true)
|
||
| Tnil ->
|
||
let v = new_global_var () in
|
||
(v, true)
|
||
|
||
let enlarge_type env ty =
|
||
subtypes := [];
|
||
let (ty', _) = build_subtype env ty in
|
||
subtypes := [];
|
||
ty'
|
||
|
||
(**** Check whether a type is a subtype of another type. ****)
|
||
|
||
(*
|
||
During the traversal, a trace of visited types is maintained. It
|
||
is printed in case of error.
|
||
Constraints (pairs of types that must be equals) are accumulated
|
||
rather than being enforced straight. Indeed, the result would
|
||
otherwise depend on the order in which these constraints are
|
||
enforced.
|
||
A function enforcing these constraints is returned. That way, type
|
||
variables can be bound to their actual values before this function
|
||
is called (see Typecore).
|
||
Only well-defined abbreviations are expanded (hence the tests
|
||
[generic_abbrev ...]).
|
||
*)
|
||
|
||
let subtypes = ref [];;
|
||
|
||
let subtype_error env trace =
|
||
raise (Subtype (expand_trace env (List.rev trace), []))
|
||
|
||
let rec subtype_rec env trace t1 t2 =
|
||
let t1 = repr t1 in
|
||
let t2 = repr t2 in
|
||
if t1 == t2 then [] else
|
||
if List.exists (fun (t1', t2') -> t1 == t1' & t2 == t2') !subtypes then
|
||
(* +++ Possibly slow *)
|
||
[]
|
||
else begin
|
||
subtypes := (t1, t2) :: !subtypes;
|
||
match (t1.desc, t2.desc) with
|
||
(Tvar, _) | (_, Tvar) ->
|
||
[(trace, t1, t2)]
|
||
| (Tarrow(t1, u1), Tarrow(t2, u2)) ->
|
||
(subtype_rec env ((t2, t1)::trace) t2 t1) @
|
||
(subtype_rec env ((u1, u2)::trace) u1 u2)
|
||
| (Ttuple tl1, Ttuple tl2) ->
|
||
subtype_list env trace tl1 tl2
|
||
| (Tconstr(p1, tl1, abbrev1), Tconstr _) when generic_abbrev env p1 ->
|
||
subtype_rec env trace (expand_abbrev env p1 tl1 abbrev1 t1.level) t2
|
||
| (Tconstr _, Tconstr(p2, tl2, abbrev2)) when generic_abbrev env p2 ->
|
||
subtype_rec env trace t1 (expand_abbrev env p2 tl2 abbrev2 t2.level)
|
||
| (Tconstr _, Tconstr _) ->
|
||
[(trace, t1, t2)]
|
||
| (Tconstr(p1, tl1, abbrev1), _) when generic_abbrev env p1 ->
|
||
subtype_rec env trace (expand_abbrev env p1 tl1 abbrev1 t1.level) t2
|
||
| (_, Tconstr (p2, tl2, abbrev2)) when generic_abbrev env p2 ->
|
||
subtype_rec env trace t1 (expand_abbrev env p2 tl2 abbrev2 t2.level)
|
||
| (Tobject (f1, _), Tobject (f2, _))
|
||
when opened_object f1 & opened_object f2 ->
|
||
(* Same row variable implies same object. *)
|
||
[(trace, t1, t2)]
|
||
| (Tobject (f1, _), Tobject (f2, _)) ->
|
||
subtype_fields env trace f1 f2
|
||
| (_, _) ->
|
||
subtype_error env trace
|
||
end
|
||
|
||
and subtype_list env trace tl1 tl2 =
|
||
if List.length tl1 <> List.length tl2 then
|
||
subtype_error env trace;
|
||
List.fold_left2
|
||
(fun cstrs t1 t2 -> cstrs @ (subtype_rec env ((t1, t2)::trace) t1 t2))
|
||
[] tl1 tl2
|
||
|
||
and subtype_fields env trace ty1 ty2 =
|
||
let (fields1, rest1) = flatten_fields ty1 in
|
||
let (fields2, rest2) = flatten_fields ty2 in
|
||
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
|
||
[(trace, rest1, build_fields miss2 (newvar ()))]
|
||
@
|
||
begin match rest2.desc with
|
||
Tnil -> []
|
||
| _ -> [(trace, build_fields miss1 rest1, rest2)]
|
||
end
|
||
@
|
||
(List.fold_left
|
||
(fun cstrs (k1, t1, k2, t2) ->
|
||
(* Theses fields are always present *)
|
||
cstrs @ (subtype_rec env ((t1, t2)::trace) t1 t2))
|
||
[] pairs)
|
||
|
||
let subtype env ty1 ty2 =
|
||
subtypes := [];
|
||
(* Build constraint set. *)
|
||
let cstrs = subtype_rec env [(ty1, ty2)] ty1 ty2 in
|
||
(* Enforce constraints. *)
|
||
function () ->
|
||
List.iter
|
||
(function (trace0, t1, t2) ->
|
||
try unify env t1 t2 with Unify trace ->
|
||
raise (Subtype (expand_trace env (List.rev trace0),
|
||
List.tl (List.tl trace))))
|
||
cstrs;
|
||
subtypes := []
|
||
|
||
|
||
(*******************)
|
||
(* Miscellaneous *)
|
||
(*******************)
|
||
|
||
|
||
let unalias ty =
|
||
let ty = repr ty in
|
||
match ty.desc with
|
||
Tvar ->
|
||
ty
|
||
| _ ->
|
||
{desc = ty.desc; level = ty.level}
|
||
|
||
let unroll_abbrev id tl ty =
|
||
let ty = repr ty in
|
||
match ty.desc with
|
||
Tvar ->
|
||
ty
|
||
| _ ->
|
||
let ty' = {desc = ty.desc; level = ty.level} in
|
||
ty.desc <- Tlink {desc = Tconstr (Path.Pident id, tl, ref Mnil);
|
||
level = ty.level};
|
||
ty'
|
||
|
||
(* Return the arity (as for curried functions) of the given type. *)
|
||
let rec arity ty =
|
||
match (repr ty).desc with
|
||
Tarrow(t1, t2) -> 1 + arity t2
|
||
| _ -> 0
|
||
|
||
|
||
(*************************)
|
||
(* Remove dependencies *)
|
||
(*************************)
|
||
|
||
|
||
(*
|
||
Variables are left unchanged. Other type nodes are duplicated, with
|
||
levels set to generic level.
|
||
During copying, the description of a (non-variable) node is first
|
||
replaced by a link to a marked stub ([Tlink (newmarkedgenvar ())]).
|
||
The mark allows to differentiate the original type from the copy.
|
||
Once the copy is made, it replaces the stub.
|
||
After copying, the description of node, which was stored by
|
||
[save_desc], must be put back, using [cleanup_types], and the
|
||
marks on the copy must be removed.
|
||
*)
|
||
|
||
let rec nondep_type_rec env id ty =
|
||
let ty = repr ty in
|
||
if (ty.desc = Tvar) || (ty.level < lowest_level) then
|
||
ty
|
||
else begin
|
||
let desc = ty.desc in
|
||
save_desc ty desc;
|
||
let ty' = newmarkedgenvar () in (* Stub *)
|
||
ty.desc <- Tlink ty';
|
||
ty'.desc <-
|
||
begin match desc with
|
||
Tvar ->
|
||
fatal_error "Ctype.nondep_type_rec"
|
||
| Tarrow(t1, t2) ->
|
||
Tarrow(nondep_type_rec env id t1, nondep_type_rec env id t2)
|
||
| Ttuple tl ->
|
||
Ttuple(List.map (nondep_type_rec env id) tl)
|
||
| Tconstr(p, tl, abbrev) ->
|
||
if Path.isfree id p then
|
||
begin try
|
||
Tlink (nondep_type_rec env id
|
||
(expand_abbrev env p tl abbrev ty.level))
|
||
(*
|
||
The [Tlink] is important. The expanded type may be a
|
||
variable, or may not be completely copied yet
|
||
(recursive type), so one cannot just take its
|
||
description.
|
||
*)
|
||
with Cannot_expand ->
|
||
raise Not_found
|
||
end
|
||
else
|
||
Tconstr(p, List.map (nondep_type_rec env id) tl, ref Mnil)
|
||
| Tobject (t1, name) ->
|
||
Tobject (nondep_type_rec env id t1,
|
||
ref (match !name with
|
||
None -> None
|
||
| Some (p, tl) ->
|
||
if Path.isfree id p then None
|
||
else Some (p, List.map (nondep_type_rec env id) tl)))
|
||
| Tfield(label, kind, t1, t2) ->
|
||
begin match field_kind_repr kind with
|
||
Fpresent ->
|
||
Tfield(label, Fpresent, nondep_type_rec env id t1,
|
||
nondep_type_rec env id t2)
|
||
| _ ->
|
||
Tlink (nondep_type_rec env id t2)
|
||
end
|
||
| Tnil ->
|
||
Tnil
|
||
| Tlink ty -> (* Actually unused *)
|
||
Tlink(nondep_type_rec env id ty)
|
||
end;
|
||
ty'
|
||
end
|
||
|
||
let nondep_type env id ty =
|
||
try
|
||
let ty' = nondep_type_rec env id ty in
|
||
cleanup_types ();
|
||
unmark_type ty';
|
||
ty'
|
||
with Not_found ->
|
||
cleanup_types ();
|
||
raise Not_found
|
||
|
||
(* Preserve sharing inside type declarations. *)
|
||
let nondep_type_decl env mid id is_covariant decl =
|
||
try
|
||
let params = List.map (nondep_type_rec env mid) decl.type_params in
|
||
let decl =
|
||
{ type_params = params;
|
||
type_arity = decl.type_arity;
|
||
type_kind =
|
||
begin try
|
||
match decl.type_kind with
|
||
Type_abstract ->
|
||
Type_abstract
|
||
| Type_variant cstrs ->
|
||
Type_variant(List.map
|
||
(fun (c, tl) -> (c, List.map (nondep_type_rec env mid) tl))
|
||
cstrs)
|
||
| Type_record lbls ->
|
||
Type_record(List.map
|
||
(fun (c, mut, t) -> (c, mut, nondep_type_rec env mid t))
|
||
lbls)
|
||
with Not_found when is_covariant ->
|
||
Type_abstract
|
||
end;
|
||
type_manifest =
|
||
begin try
|
||
match decl.type_manifest with
|
||
None -> None
|
||
| Some ty ->
|
||
Some (unroll_abbrev id params (nondep_type_rec env mid ty))
|
||
with Not_found when is_covariant ->
|
||
None
|
||
end }
|
||
in
|
||
cleanup_types ();
|
||
List.iter unmark_type decl.type_params;
|
||
begin match decl.type_kind with
|
||
Type_abstract -> ()
|
||
| Type_variant cstrs ->
|
||
List.iter (fun (c, tl) -> List.iter unmark_type tl) cstrs
|
||
| Type_record lbls ->
|
||
List.iter (fun (c, mut, t) -> unmark_type t) lbls
|
||
end;
|
||
begin match decl.type_manifest with
|
||
None -> ()
|
||
| Some ty -> unmark_type ty
|
||
end;
|
||
decl
|
||
with Not_found ->
|
||
cleanup_types ();
|
||
raise Not_found
|
||
|
||
(* Preserve sharing inside class types. *)
|
||
let nondep_class_type env id decl =
|
||
try
|
||
let decl =
|
||
{ cty_params = List.map (nondep_type_rec env id) decl.cty_params;
|
||
cty_args = List.map (nondep_type_rec env id) decl.cty_args;
|
||
cty_vars =
|
||
Vars.map (function (m, t) -> (m, nondep_type_rec env id t))
|
||
decl.cty_vars;
|
||
cty_meths = Meths.map (nondep_type_rec env id) decl.cty_meths;
|
||
cty_self = nondep_type_rec env id decl.cty_self;
|
||
cty_concr = decl.cty_concr;
|
||
cty_new =
|
||
begin match decl.cty_new with
|
||
None -> None
|
||
| Some ty -> Some (nondep_type_rec env id ty)
|
||
end }
|
||
in
|
||
cleanup_types ();
|
||
List.iter unmark_type decl.cty_params;
|
||
List.iter unmark_type decl.cty_args;
|
||
Vars.iter (fun l (m, t) -> unmark_type t) decl.cty_vars;
|
||
Meths.iter (fun l t -> unmark_type t) decl.cty_meths;
|
||
unmark_type decl.cty_self;
|
||
begin match decl.cty_new with
|
||
None -> ()
|
||
| Some ty -> unmark_type ty
|
||
end;
|
||
decl
|
||
with Not_found ->
|
||
cleanup_types ();
|
||
raise Not_found
|
||
|
||
|
||
(**************************************)
|
||
(* Check genericity of type schemes *)
|
||
(**************************************)
|
||
|
||
|
||
type closed_schema_result = Var of type_expr | Row_var of type_expr
|
||
exception Failed of closed_schema_result
|
||
|
||
let rec closed_schema_rec row ty =
|
||
let ty = repr ty in
|
||
if ty.level >= lowest_level then begin
|
||
let level = ty.level in
|
||
ty.level <- pivot_level - level;
|
||
match ty.desc with
|
||
Tvar when level <> generic_level ->
|
||
raise (Failed (if row then Row_var ty else Var ty))
|
||
| Tobject(f, {contents = Some (_, p)}) ->
|
||
closed_schema_rec true f;
|
||
List.iter (closed_schema_rec false) p
|
||
| Tobject(f, _) ->
|
||
closed_schema_rec true f
|
||
| Tfield(_, kind, t1, t2) ->
|
||
if field_kind_repr kind = Fpresent then
|
||
closed_schema_rec false t1;
|
||
closed_schema_rec true t2
|
||
| _ ->
|
||
iter_type_expr (closed_schema_rec false) ty
|
||
end
|
||
|
||
(* Return whether all variables of type [ty] are generic. *)
|
||
let closed_schema ty =
|
||
try
|
||
closed_schema_rec false ty;
|
||
unmark_type ty;
|
||
true
|
||
with Failed _ ->
|
||
unmark_type ty;
|
||
false
|
||
|
||
(*
|
||
Check that all variables of type [ty] are generic. If this is not
|
||
the case, the non-generic variable is returned. The type is never
|
||
generalized.
|
||
*)
|
||
let closed_schema_verbose ty =
|
||
try
|
||
closed_schema_rec false ty;
|
||
unmark_type ty;
|
||
None
|
||
with Failed status ->
|
||
unmark_type ty;
|
||
Some status
|