Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with
or
.
Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

72 lines (64 sloc) 3.692 kB
(*
Copyright © 2011 MLstate
This file is part of OPA.
OPA is free software: you can redistribute it and/or modify it under the
terms of the GNU Affero General Public License, version 3, as published by
the Free Software Foundation.
OPA is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for
more details.
You should have received a copy of the GNU Affero General Public License
along with OPA. If not, see <http://www.gnu.org/licenses/>.
*)
(*
@author François Pessaux
*)
type expansions_memory
val empty_memory : expansions_memory
val incrementally_expand_abbrev:
W_TypingEnv.t -> expansions_memory -> W_Algebra.simple_type ->
expansions_memory
(* ************************************************************************** *)
(** {b Descr}: Fully expand a named type untils either it is no more a named
type or it can't be expanded anymore. In other words, follow the sequence
of type abbreviations.
If this function is called on something else than a named type, it simply
returns the type itself.
Note that during expansion, the original type is modified in place, setting
is field [W_Algebra.nst_unwinded] to [Some ...] (and in depth) each time
an abbrev is expanded.
The expansion is just "deep in surface": we follow the cascading
abbreviations but do not expand abbreviations present in the structure of
the type (anyway, since we stop when we get something else than a named
type, this remark may seem obvious, but that's better to say this clearly).
This function is currently used to report errors in order to find fields
suggestions in case of error on a dot-expression. It allows to find a
record type hidden under a type abbreviation, hence seing the structure of
this type, it is possible to see its available fields. Not expanding the
abbreviations would leave the named type as it is, hence not showing
fields, hence not allowing to give close available fields as a hint.
{b Visibility}: Exported outside this module. *)
(* ************************************************************************** *)
val fully_expand_abbrev:
W_TypingEnv.t -> expansions_memory -> W_Algebra.simple_type ->
W_Algebra.simple_type
(* ************************************************************************** *)
(* {b Descr}: Performs a deep occur check, checking if the type variable passed
as argument ([ty_var]) is in fact the same type than the other one ([ty])
passed as argument by following type aliases.
This is very important to prevent unification to create cyclic types in case
of unifying types like ['a] and ['a t] in case where [t] is defined as
[type 'a t = 'a u = 'a v = ... 'a].
In effect, if we don't be careful, seing ['a] and ['a t] unification would
simply establish a link from ['a] to ['a t] hence creating a cycle. This
would result into an exportation error, although in fact, ['a] and ['a t]
are exactly the same type.
This function doesn't modify the structure of type. It unwinds [ty] without
modifying its structure and in particular, without setting the field
[W_Algebra.nst_unwinded] of types.
{b Visibility}: Exported outside this module. *)
(* ************************************************************************** *)
val deep_exact_occur_expand_abbrev:
W_TypingEnv.t -> expansions_memory -> ty_var: W_Algebra.simple_type ->
in_ty: W_Algebra.simple_type -> bool
Jump to Line
Something went wrong with that request. Please try again.