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|
Require Import Ltac2.Ltac2 Ltac2.Notations.
Ltac2 Type exn ::= [ Nope ].
Ltac2 check_id id id' := match Ident.equal id id' with
| true => ()
| false => Control.throw Nope
end.
Goal True -> False.
Proof.
Fail
let b := { contents := true } in
let f c :=
match b.(contents) with
| true => Message.print (Message.of_constr c); b.(contents) := false; fail
| false => ()
end
in
(** This fails because the matching is not allowed to backtrack once
it commits to a branch*)
lazy_match! '(nat -> bool) with context [?a] => f a end.
lazy_match! Control.goal () with ?a -> ?b => Message.print (Message.of_constr b) end.
(** This one works by taking the second match context, i.e. ?a := nat *)
let b := { contents := true } in
let f c :=
match b.(contents) with
| true => b.(contents) := false; fail
| false => Message.print (Message.of_constr c)
end
in
match! '(nat -> bool) with context [?a] => f a end.
Abort.
Goal forall (i j : unit) (x y : nat) (b : bool), True.
Proof.
Fail match! goal with
| [ h : ?t, h' : ?t |- _ ] => ()
end.
intros i j x y b.
match! goal with
| [ h : ?t, h' : ?t |- _ ] =>
check_id h @x;
check_id h' @y
end.
match! reverse goal with
| [ h : ?t, h' : ?t |- _ ] =>
check_id h @j;
check_id h' @i
end.
Abort.
|
