A well-known challenge in leveraging automatic theorem provers, such as satisfiability modulo theories (SMT) solvers, to discharge proof obligations from interactive theorem provers (ITPs) is determining which axioms to send to the solver together with the conjecture to be proven. Too many axioms may confuse or clog the solver, while too few may make a theorem unprovable. When a solver fails to prove a conjecture it is unclear to the user which case transpired. In this paper, we enhance SMTCoq — an integration between the Coq ITP and the cvc5 SMT solver — with a tactic called abduce aimed at mitigating the uncertainty above. When the solver fails to prove the goal, the user may invoke abduce which will use abductive reasoning to provide facts that will allow the solver to prove the goal, if any.

An Interactive SMT Tactic in Coq Using Abductive Reasoning