This commit introduces changes in induction and destruct.

The main change is that selection of subterm is made similar whether
the given term is fully applied or not.
- The selection of subterm now works as follows depending on whether
  the "at" is given, of whether the subterm is fully applied or not,
  and whether there are incompatible subterms matching the pattern. In
  particular, we have:
  "at" given
  | subterm fully applied
  | | incompatible subterms
  | | |
  Y Y - it works like in 8.4
  Y N - this was broken in 8.4 ("at" was ineffective and it was finding
        all subterms syntactically equal to the first one which matches)
  N Y Y it now finds all subterms like the first one which matches
        while in 8.4 it used to fail (I hope it is not a too risky in-draft
        for a semantics we would regret...) (e.g. "destruct (S _)" on
        goal "S x = S y + S x" now selects the two occurrences of "S x"
        while it was failing before)
  N Y N it works like in 8.4
  N N - it works like in 8.4, selecting all subterms like the
        first one which matches
- Note that the "historical" semantics, when looking for a subterm, to
  select all subterms that syntactically match the first subterm to
  match the pattern (looking from left to right) is now internally called
  "like first".
- Selection of subterms can now find the type by pattern-matching (useful e.g.
  for "induction (nat_rect _ _ _ _)")
- A version of Unification.w_unify w/o any conversion is used for
  finding the subterm: it could be easily replaced by an other
  matching algorithm.

In particular, "destruct H" now works on a goal such as "H:True -> x<=y |- P y".

Secondary change is in the interpretation of terms with existential
variables:
- When several arguments are given, interpretation is delayed at the
  time of execution
- Because we aim at eventually accepting "edestruct c" with unresolved
  holes in c, we need the sigma obtained from c to be an extension of
  the sigma of the tactics, while before, we just type-checked c
  independently of the sigma of the tactic
- Finishing the resolution of evars (using type classes, candidates,
  pending conversion problems) is made slightly cleaner: it now takes
  three states: a term is evaluated in state sigma, leading to state
  sigma' >= sigma, with evars finally solved in state sigma'' >=
  sigma'; we solve evars in the diff of sigma' and sigma and report
  the solution in sigma''
- We however renounce to give now a success semantics to "edestruct c"
  when "c" has unresolved holes, waiting instead for a decision on
  what to do in the case of a similar eapply (see mail to coqdev).

An auxiliary change is that an "in" clause can be attached to each component
of a "destruct t, u, v", etc.

Incidentally, make_abstraction does not do evar resolution itself any longer.

2 files changed, 9 insertions, 2 deletions

diff --git a/proofs/clenv.ml b/proofs/clenv.ml
index d852a02785..fb5a76bd30 100644
--- a/proofs/clenv.ml
+++ b/proofs/clenv.ml
@@ -118,13 +118,13 @@ let clenv_environments evd bound t =
   in
   clrec (evd,[]) bound t
 
-let mk_clenv_from_env environ sigma n (c,cty) =
+let mk_clenv_from_env env sigma n (c,cty) =
   let evd = create_goal_evar_defs sigma in
   let (evd,args,concl) = clenv_environments evd n cty in
   { templval = mk_freelisted (applist (c,args));
     templtyp = mk_freelisted concl;
     evd = evd;
-    env = environ }
+    env = env }
 
 let mk_clenv_from_n gls n (c,cty) =
   mk_clenv_from_env (pf_env gls) gls.sigma n (c, cty)
@@ -532,6 +532,9 @@ let make_clenv_binding_gen hyps_only n env sigma (c,t) = function
 
 let make_clenv_binding_env_apply env sigma n =
   make_clenv_binding_gen true n env sigma
+
+let make_clenv_binding_env env sigma =
+  make_clenv_binding_gen false None env sigma
 	
 let make_clenv_binding_apply env sigma n = make_clenv_binding_gen true n env sigma
 let make_clenv_binding env sigma = make_clenv_binding_gen false None env sigma
diff --git a/proofs/clenv.mli b/proofs/clenv.mli
index d7bdaf2f5c..5868f1e9bf 100644
--- a/proofs/clenv.mli
+++ b/proofs/clenv.mli
@@ -96,6 +96,10 @@ val make_clenv_binding_env_apply :
 val make_clenv_binding_apply :
   env -> evar_map -> int option -> constr * constr -> constr bindings ->
    clausenv
+
+val make_clenv_binding_env :
+  env -> evar_map -> constr * constr -> constr bindings -> clausenv
+
 val make_clenv_binding :
   env -> evar_map -> constr * constr -> constr bindings -> clausenv