-val stop_all : unit -> unit
-(** Wait until all running jobs finish, and don't start any new ones.
- See [Jobs.stop_all]. *)
+val exists_runner : Deps.exists_runner
+(** Run the implicit existence tactic.
+
+ This is used when we find a tactic like *foo(...) but there
+ is no matching goal. We run (in this callback) the associated
+ tactic code. As long as it runs successfully, not returning 99 or
+ any error value, then we're OK - the tactic doesn't need rebuilding
+ so the dependency is satisfied. However if it returns 99 (needs
+ rebuild) or an error then we have to exit with an error. *)