. split at rupAddSuccess
  . simp only [Prod.mk.injEq, and_false] at rupAddSuccess
  . next performRupCheck_success =>
    rw [Bool.not_eq_false] at performRupCheck_success
    have f_limplies_fc := performRupCheck_of_insertRup_entails_safe_insert f f_readyForRupAdd c rupHints performRupCheck_success
    rw [liff_iff_limplies_and_limplies f f', f'_def]
    constructor
    . exact f_limplies_fc
    . exact limplies_of_insert f c
case isFalse.isFalse
n : Nat
f : DefaultFormula n
c : DefaultClause n
rupHints : Array Nat
f' : DefaultFormula n
f_readyForRupAdd : f.readyForRupAdd
f'_def : f' = f.insert c
h✝¹ : ¬(f.insertRupUnits c.negate).snd = true
h✝ : ¬((f.insertRupUnits c.negate).fst.performRupCheck rupHints).2.2.snd = true
rupAddSuccess :
  (if ((f.insertRupUnits c.negate).fst.performRupCheck rupHints).2.2.fst = false then
      (((f.insertRupUnits c.negate).fst.performRupCheck rupHints).fst, false)
    else
      ({ clauses := ((f.insertRupUnits c.negate).fst.performRupCheck rupHints).1.clauses,
                rupUnits := ((f.insertRupUnits c.negate).fst.performRupCheck rupHints).1.rupUnits,
                ratUnits := ((f.insertRupUnits c.negate).fst.performRupCheck rupHints).1.ratUnits,
                assignments :=
                  restoreAssignments ((f.insertRupUnits c.negate).fst.performRupCheck rupHints).1.assignments
                    ((f.insertRupUnits c.negate).fst.performRupCheck rupHints).2.fst }.clearRupUnits.insert
          c,
        true)) =
    (f', true)
⊢ liff (PosFin n) f f'
no goals