Keyed unification option, compiling the whole standard library

(but deactivated still).

Set Keyed Unification to activate the option, which changes
subterm selection to _always_ use full conversion _after_ finding a
subterm whose head/key matches the key of the term we're looking for.
This applies to rewrite and higher-order unification in
apply/elim/destruct.

Most proof scripts already abide by these semantics. For those that
don't, it's usually only a matter of using:

Declare Equivalent Keys f g.

This make keyed unification consider f and g to match as keys.
This takes care of most cases of abbreviations: typically Def foo :=
bar and rewriting with a bar-headed lhs in a goal mentioning foo works
once they're set equivalent.
For canonical structures, these hints should be automatically declared.

For non-global-reference headed terms, the key is the constructor name
(Sort, Prod...). Evars and metas are no keys.

INCOMPATIBILITIES:
In FMapFullAVL, a Function definition doesn't go through with keyed
unification on.

1 files changed, 11 insertions, 5 deletions

diff --git a/pretyping/unification.ml b/pretyping/unification.ml
index efa64ca1ea..735d4b68ab 100644
--- a/pretyping/unification.ml
+++ b/pretyping/unification.ml
@@ -1457,11 +1457,17 @@ let make_abstraction env evd ccl abs =
       make_abstraction_core name
         (make_eq_test env evd c) (evd,c) ty occs check_occs env ccl
 
-let keyed_unify env evd kop cl = 
-  if not !keyed_unification then true
-  else
-    let k2 = Keys.constr_key cl in
-      Keys.equiv_keys kop k2
+let keyed_unify env evd kop = 
+  if not !keyed_unification then fun cl -> true
+  else 
+    match kop with 
+    | None -> fun _ -> true
+    | Some kop ->
+      fun cl ->
+	let kc = Keys.constr_key cl in
+	  match kc with
+	  | None -> false
+	  | Some kc -> Keys.equiv_keys kop kc
 
 (* Tries to find an instance of term [cl] in term [op].
    Unifies [cl] to every subterm of [op] until it finds a match.