next idx_eq_j =>
apply Or.inl
constructor
. simp only [clearUnit, idx_eq_j, Array.get_eq_getElem, ih1]
  have i_in_bounds : i.1 < assignments.size := by rw [hsize]; exact i.2
  rw [Array.get_modify_at_idx i_in_bounds, ih2, remove_add_cancel]
  exact ih3
. intro k k_ge_idx_add_one
  have k_ge_idx : k.val ≥ idx.val := Nat.le_of_succ_le k_ge_idx_add_one
  have k_ne_j : k ≠ j := by
    intro k_eq_j
    rw [k_eq_j, idx_eq_j] at k_ge_idx_add_one
    exact Nat.not_succ_le_self j.val k_ge_idx_add_one
  exact ih4 k k_ge_idx k_ne_j
case pos
n : Nat
f : DefaultFormula n
f_assignments_size : f.assignments.size = n
units : Array (Literal (PosFin n))
units_nodup : ∀ (i j : Fin units.size), i ≠ j → units[i] ≠ units[j]
idx : Fin units.size
assignments : Array Assignment
hsize : assignments.size = n
hsize' : (clearUnit assignments units[idx]).size = n
i : Fin n
j : Fin units.size
j_ge_idx : ↑j ≥ ↑idx
b : Bool
i_gt_zero : ↑i > 0
ih1 : units[↑j] = (⟨↑i, ⋯⟩, b)
ih2 : assignments[↑i] = addAssignment b f.assignments[↑i]
ih3 : ¬hasAssignment b f.assignments[↑i] = true
ih4 : ∀ (k : Fin units.size), ↑k ≥ ↑idx → ¬k = j → ¬units[↑k].fst.val = ↑i
h✝ : idx = j
⊢ let_fun i_lt_assignments_size := ⋯;
  let_fun i_lt_f_assignments_size := ⋯;
  let assignments_i := (clearUnit assignments units[idx])[↑i];
  let fassignments_i := f.assignments[↑i];
  (assignments_i = fassignments_i ∧ ∀ (j : Fin units.size), ↑j ≥ ↑idx + 1 → units[j].fst.val ≠ ↑i) ∨
    (∃ j b i_gt_zero,
        ↑j ≥ ↑idx + 1 ∧
          units[j] = (⟨↑i, ⋯⟩, b) ∧
            assignments_i = addAssignment b fassignments_i ∧
              ¬hasAssignment b fassignments_i = true ∧
                ∀ (k : Fin units.size), ↑k ≥ ↑idx + 1 → k ≠ j → units[k].fst.val ≠ ↑i) ∨
      ∃ j1 j2 i_gt_zero,
        ↑j1 ≥ ↑idx + 1 ∧
          ↑j2 ≥ ↑idx + 1 ∧
            units[j1] = (⟨↑i, ⋯⟩, true) ∧
              units[j2] = (⟨↑i, ⋯⟩, false) ∧
                assignments_i = both ∧
                  fassignments_i = unassigned ∧
                    ∀ (k : Fin units.size), ↑k ≥ ↑idx + 1 → k ≠ j1 → k ≠ j2 → units[k].fst.val ≠ ↑i
no goals