next ib_eq_c =>
simp only [toList, Array.toList_eq, Array.push_data, List.append_assoc, List.mem_append, List.mem_filterMap,
  List.mem_singleton, id_eq, exists_eq_right, Option.some.injEq, List.mem_map, Prod.exists, Bool.exists_bool]
apply Or.inl ∘ Or.inr
rw [isUnit_iff, DefaultClause.toList, ← ib_eq_c] at hc
apply DefaultClause.ext
simp only [unit, hc]
case pos
n : Nat
f : DefaultFormula n
c : DefaultClause n
f_readyForRupAdd : f.readyForRupAdd
x✝ : Option (Literal (PosFin n))
l : PosFin n
hc : c.isUnit = some (l, true)
hsize : (f.assignments.modify l.val addPosAssignment).size = n
i : PosFin n
b : Bool
hb : hasAssignment b (f.assignments.modify l.val addPosAssignment)[i.val] = true
hf : hasAssignment b f.assignments[i.val] = true → unit (i, b) ∈ f.toList
i_in_bounds : i.val < f.assignments.size
l_in_bounds : l.val < f.assignments.size
h✝ : (i, b) = (l, true)
⊢ unit (i, b) ∈
    { clauses := f.clauses.push (some c), rupUnits := f.rupUnits, ratUnits := f.ratUnits,
        assignments := f.assignments.modify l.val addPosAssignment }.toList
no goals