. split at rupAddSuccess
  . simp only [Prod.mk.injEq, and_false] at rupAddSuccess
  . let fc := (insertRupUnits f (negate c)).1
    have fc_assignments_size : (insertRupUnits f (negate c)).1.assignments.size = n := by
      rw [insertRupUnits_preserves_assignments_size f (negate c)]
      exact f_readyForRupAdd.2.1
    simp only [performRupCheck_preserves_clauses, performRupCheck_preserves_rupUnits, performRupCheck_preserves_ratUnits,
      restoreAssignments_performRupCheck fc fc_assignments_size, Prod.mk.injEq, and_true] at rupAddSuccess
    have rupAddSuccess : DefaultFormula.insert (clearRupUnits (insertRupUnits f (negate c)).fst) c = f' := by
      rw [rupAddSuccess]
    rw [clear_insertRup f f_readyForRupAdd (negate c)] at rupAddSuccess
    exact rupAddSuccess.symm
case isFalse.isFalse
n : Nat
f : DefaultFormula n
c : DefaultClause n
rupHints : Array Nat
f' : DefaultFormula n
f_readyForRupAdd : f.readyForRupAdd
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)
⊢ f' = f.insert c
no goals