First attempt at making Print Assumption compatible with opaque modules (fix #2168)

 We replace Global.lookup_constant by our own code that looks for a module
 and enters its implementation. This is still preliminary work, I would prefer
 to understand more completely the part about module substitutions when
 entering an applied functor. But this code already appears to work quite well.
 Anyway, since we only search for constants, we don't need to reconstitute a
 100% accurate environment, as long as the same objects are in it.

 Note:

  - Digging inside module structures is slower than just using
    Global.lookup_constant. Hence we try to avoid it as long as we could.
    Only in front of axioms (or in front of constant unknown to Global)
    do we check whether we have an inner-module implementation for this
    constant. There is some memoization of the search for internal
    structure_body out of a module_path.

  - In case of inner-module axioms, we might not be able to print
    its type, but only its long name.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@14600 85f007b7-540e-0410-9357-904b9bb8a0f7

3 files changed, 267 insertions, 1 deletions

diff --git a/library/assumptions.ml b/library/assumptions.ml
new file mode 100644
index 000000000..adc7f8edc
--- /dev/null
+++ b/library/assumptions.ml
@@ -0,0 +1,238 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2010     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+(* The following definitions are used by the function
+   [assumptions] which gives as an output the set of all
+   axioms and sections variables on which a given term depends
+   in a context (expectingly the Global context) *)
+
+(* Initial author: Arnaud Spiwack
+   Module-traversing code: Pierre Letouzey *)
+
+open Util
+open Names
+open Sign
+open Univ
+open Term
+open Declarations
+open Mod_subst
+
+let cst_ord k1 k2 = kn_ord (canonical_con k1) (canonical_con k2)
+
+type context_object =
+  | Variable of identifier (* A section variable or a Let definition *)
+  | Axiom of constant      (* An axiom or a constant. *)
+  | Opaque of constant     (* An opaque constant. *)
+
+(* Defines a set of [assumption] *)
+module OrderedContextObject =
+struct
+  type t = context_object
+  let compare x y =
+      match x , y with
+      | Variable i1 , Variable i2 -> id_ord i1 i2
+      | Axiom k1 , Axiom k2 -> cst_ord k1 k2
+      | Opaque k1 , Opaque k2 -> cst_ord k1 k2
+      | Variable _ , Axiom _ -> -1
+      | Axiom _ , Variable _ -> 1
+      | Opaque _ , _ -> -1
+      | _, Opaque _ -> 1
+end
+
+module ContextObjectSet = Set.Make (OrderedContextObject)
+module ContextObjectMap = Map.Make (OrderedContextObject)
+
+(** For a constant c in a module sealed by an interface (M:T and
+    not M<:T), [Global.lookup_constant] may return a [constant_body]
+    without body. We fix this by looking in the implementation
+    of the module *)
+
+let modcache = ref (MPmap.empty : structure_body MPmap.t)
+
+let rec lookup_module_in_impl mp =
+  try Global.lookup_module mp
+  with Not_found ->
+    (* The module we search might not be exported by its englobing module(s).
+       We access the upper layer, and then do a manual search *)
+    match mp with
+      | MPfile _ | MPbound _ ->
+	raise Not_found (* should have been found by [lookup_module] *)
+      | MPdot (mp',lab') ->
+	let fields = memoize_fields_of_mp mp' in
+	match List.assoc lab' fields with
+	  | SFBmodule mb -> mb
+	  | _ -> assert false (* same label for a non-module ?! *)
+
+and memoize_fields_of_mp mp =
+  try MPmap.find mp !modcache
+  with Not_found ->
+    let l = fields_of_mp mp in
+    modcache := MPmap.add mp l !modcache;
+    l
+
+and fields_of_mp mp =
+  let mb = lookup_module_in_impl mp in
+  let fields,inner_mp,subs = fields_of_mb empty_subst mb [] in
+  let subs =
+    if inner_mp = mp then subs
+    else add_mp inner_mp mp mb.mod_delta subs
+  in
+  Modops.subst_signature subs fields
+
+and fields_of_mb subs mb args =
+  let seb = match mb.mod_expr with
+    | None -> mb.mod_type (* cf. Declare Module *)
+    | Some seb -> seb
+  in
+  fields_of_seb subs mb.mod_mp seb args
+
+(* TODO: using [empty_delta_resolver] below in [fields_of_seb]
+   is probably slightly incorrect. But:
+    a) I don't see currently what should be used instead
+    b) this shouldn't be critical for Print Assumption. At worse some
+       constants will have a canonical name which is non-canonical,
+       leading to failures in [Global.lookup_constant], but our own
+       [lookup_constant] should work.
+*)
+
+and fields_of_seb subs mp0 seb args = match seb with
+  | SEBstruct l ->
+    assert (args = []);
+    l, mp0, subs
+  | SEBident mp ->
+    let mb = lookup_module_in_impl (subst_mp subs mp) in
+    fields_of_mb subs mb args
+  | SEBapply (seb1,seb2,_) ->
+    (match seb2 with
+      | SEBident mp2 -> fields_of_seb subs mp0 seb1 (mp2::args)
+      | _ -> assert false) (* only legal application is to module names *)
+  | SEBfunctor (mbid,mtb,seb) ->
+    (match args with
+      | [] -> assert false (* we should only encounter applied functors *)
+      | mpa :: args ->
+	let subs = add_mbid mbid mpa empty_delta_resolver subs in
+	fields_of_seb subs mp0 seb args)
+  | SEBwith _ -> assert false (* should not appear in a mod_expr
+				   or mod_type field *)
+
+let lookup_constant_in_impl cst fallback =
+  try
+    let mp,dp,lab = repr_kn (canonical_con cst) in
+    let fields = memoize_fields_of_mp mp in
+    (* A module found this way is necessarily closed, in particular
+       our constant cannot be in an opened section : *)
+    match List.assoc lab fields with
+      | SFBconst cb -> cb
+      | _ -> assert false (* label not pointing to a constant ?! *)
+  with Not_found ->
+    (* Either:
+       - The module part of the constant isn't registered yet :
+         we're still in it, so the [constant_body] found earlier
+         (if any) was a true axiom.
+       - The label has not been found in the structure. This is an error *)
+    match fallback with
+      | Some cb -> cb
+      | None -> anomaly ("Print Assumption: unknown constant "^string_of_con cst)
+
+let lookup_constant cst =
+  try
+    let cb = Global.lookup_constant cst in
+    if constant_has_body cb then cb
+    else lookup_constant_in_impl cst (Some cb)
+  with Not_found -> lookup_constant_in_impl cst None
+
+let assumptions ?(add_opaque=false) st (* t *) =
+  modcache := MPmap.empty;
+  let (idts,knst) = st in
+  (* Infix definition for chaining function that accumulate
+     on a and a ContextObjectSet, ContextObjectMap.  *)
+  let ( ** ) f1 f2 s m = let (s',m') = f1 s m in f2 s' m' in
+  (* This function eases memoization, by checking if an object is already
+     stored before trying and applying a function.
+     If the object is there, the function is not fired (we are in a
+     particular case where memoized object don't need a treatment at all).
+     If the object isn't there, it is stored and the function is fired*)
+  let try_and_go o f s m =
+    if ContextObjectSet.mem o s then
+      (s,m)
+    else
+      f (ContextObjectSet.add o s) m
+  in
+  let identity2 s m = (s,m)
+  in
+  (* Goes recursively into the term to see if it depends on assumptions.
+    The 3 important cases are :
+     - Const _ where we need to first unfold the constant and return
+       the needed assumptions of its body in the environment,
+     - Rel _ which means the term is a variable which has been bound
+       earlier by a Lambda or a Prod (returns [] ),
+     - Var _ which means that the term refers to a section variable or
+       a "Let" definition, in the former it is an assumption of [t],
+       in the latter is must be unfolded like a Const.
+    The other cases are straightforward recursion.
+    Calls to the environment are memoized, thus avoiding to explore
+    the DAG of the environment as if it was a tree (can cause
+    exponential behavior and prevent the algorithm from terminating
+    in reasonable time). [s] is a set of [context_object], representing
+    the object already visited.*)
+  let rec do_constr t s acc =
+    let rec iter t =
+      match kind_of_term t with
+	| Var id -> do_memoize_id id
+	| Meta _ | Evar _ -> assert false
+	| Cast (e1,_,e2) | Prod (_,e1,e2) | Lambda (_,e1,e2) ->
+	  (iter e1)**(iter e2)
+	| LetIn (_,e1,e2,e3) -> (iter e1)**(iter e2)**(iter e3)
+	| App (e1, e_array) -> (iter e1)**(iter_array e_array)
+	| Case (_,e1,e2,e_array) -> (iter e1)**(iter e2)**(iter_array e_array)
+	| Fix (_,(_, e1_array, e2_array)) | CoFix (_,(_,e1_array, e2_array)) ->
+          (iter_array e1_array) ** (iter_array e2_array)
+	| Const kn -> do_memoize_kn kn
+	| _ -> identity2 (* closed atomic types + rel *)
+    and iter_array a = Array.fold_right (fun e f -> (iter e)**f) a identity2
+    in iter t s acc
+
+  and add_id id s acc =
+    (* a Var can be either a variable, or a "Let" definition.*)
+    match Global.lookup_named id with
+    | (_,None,t) ->
+        (s,ContextObjectMap.add (Variable id) t acc)
+    | (_,Some bdy,_) -> do_constr bdy s acc
+
+  and do_memoize_id id =
+    try_and_go (Variable id) (add_id id)
+
+  and add_kn kn s acc =
+    let cb = lookup_constant kn in
+    let do_type cst =
+      let ctype =
+	match cb.Declarations.const_type with
+	| PolymorphicArity (ctx,a) -> mkArity (ctx, Type a.poly_level)
+	| NonPolymorphicType t -> t
+      in
+	(s,ContextObjectMap.add cst ctype acc)
+    in
+    let (s,acc) =
+      if add_opaque && Declarations.constant_has_body cb
+	&& (Declarations.is_opaque cb || not (Cpred.mem kn knst))
+      then
+	do_type (Opaque kn)
+      else (s,acc)
+    in
+      match Declarations.body_of_constant cb with
+      | None -> do_type (Axiom kn)
+      | Some body -> do_constr (Declarations.force body) s acc
+
+  and do_memoize_kn kn =
+    try_and_go (Axiom kn) (add_kn kn)
+
+ in
+ fun t ->
+   snd (do_constr t
+	  (ContextObjectSet.empty)
+	  (ContextObjectMap.empty))
diff --git a/library/assumptions.mli b/library/assumptions.mli
new file mode 100644
index 000000000..1e3e9ef86
--- /dev/null
+++ b/library/assumptions.mli
@@ -0,0 +1,28 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2010     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+open Names
+open Term
+open Environ
+
+(** A few declarations for the "Print Assumption" command
+    @author spiwack *)
+type context_object =
+  | Variable of identifier (** A section variable or a Let definition *)
+  | Axiom of constant      (** An axiom or a constant. *)
+  | Opaque of constant     (** An opaque constant. *)
+
+(** AssumptionSet.t is a set of [assumption] *)
+module OrderedContextObject :  Set.OrderedType with type t = context_object
+module ContextObjectMap : Map.S with type key = context_object
+
+(** collects all the assumptions (optionally including opaque definitions)
+   on which a term relies (together with their type) *)
+val assumptions :
+  ?add_opaque:bool -> transparent_state -> constr ->
+    Term.types ContextObjectMap.t
diff --git a/library/library.mllib b/library/library.mllib
index 4efb69a21..e8b5a7a4c 100644
--- a/library/library.mllib
+++ b/library/library.mllib
@@ -13,4 +13,4 @@ Dischargedhypsmap
 Goptions
 Decls
 Heads
-
+Assumptions
\ No newline at end of file