-(*CSC: Bug (or feature?). [with_what] is parsed in the context of the goal, *)
-(*CSC: while [what] can have a richer context (because of binders) *)
-(*CSC: So it is _NOT_ possible to use those binders in the [with_what] term. *)
-(*CSC: Is that evident? Is that right? Or should it be changed? *)
-let change_tac ~what ~with_what =
- let change_tac ~what ~with_what (proof, goal) =
- let curi,metasenv,pbo,pty = proof in
- let metano,context,ty = CicUtil.lookup_meta goal metasenv in
- (* are_convertible works only on well-typed terms *)
- let _,u =
- CicTypeChecker.type_of_aux' metasenv context with_what
- CicUniv.empty_ugraph
- in (* TASSI: FIXME *)
- let b,_ =
- CicReduction.are_convertible context what with_what u
+(* Note: this code is almost identical to ReductionTactics.reduction_tac and
+* it could be unified by making the change function a callback *)
+(* CSC: with_what is parsed in the context of the goal, but it should replace
+ something that lives in a completely different context. Thus we
+ perform a delift + lift phase to move it in the right context. However,
+ in this way the tactic is less powerful than expected: with_what cannot
+ reference variables that are local to the term that is going to be
+ replaced. To fix this we should parse with_what in the context of the
+ term(s) to be replaced. *)
+let change_tac ~pattern with_what =
+ let change_tac ~pattern ~with_what (proof, goal) =
+ let curi,metasenv,pbo,pty = proof in
+ let (metano,context,ty) as conjecture = CicUtil.lookup_meta goal metasenv in
+ let context_len = List.length context in
+ let change context'_len where terms =
+ if terms = [] then where
+ else
+ let terms, terms' =
+ List.split
+ (List.map
+ (fun (context_of_t, t) ->
+ let context_of_t_len = List.length context_of_t in
+ let with_what_in_context' =
+ if context_len > context'_len then
+ begin
+ let with_what,subst,metasenv' =
+ CicMetaSubst.delift_rels [] metasenv
+ (context_len - context'_len) with_what
+ in
+ assert (subst = []);
+ assert (metasenv = metasenv');
+ with_what
+ end
+ else
+ with_what in
+ let with_what_in_context_of_t =
+ if context_of_t_len > context'_len then
+ CicSubstitution.lift (context_of_t_len - context'_len)
+ with_what_in_context'
+ else
+ with_what in
+ let _,u =
+ CicTypeChecker.type_of_aux' metasenv context_of_t with_what
+ CicUniv.empty_ugraph in
+ let b,_ =
+ CicReduction.are_convertible ~metasenv context_of_t t with_what u in
+ if b then
+ t, with_what_in_context_of_t
+ else
+ raise NotConvertible) terms)