Theorem: LRAT.DefaultFormula.clear_insert_inductive_case
Proof state before:
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
j1 : Fin units.size
j1_ge_idx : ↑j1 ≥ ↑idx
j2 : Fin units.size
j2_ge_idx : ↑j2 ≥ ↑idx
i_gt_zero : ↑i > 0
ih1 : units[↑j1] = (⟨↑i, ⋯⟩, true)
ih2 : units[↑j2] = (⟨↑i, ⋯⟩, false)
ih3 : assignments[↑i] = both
ih4 : f.assignments[↑i] = unassigned
ih5 : ∀ (k : Fin units.size), ↑k ≥ ↑idx → ¬k = j1 → ¬k = j2 → ¬units[↑k].fst.val = ↑i
h✝ : idx = j1
⊢ 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

case neg
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
j1 : Fin units.size
j1_ge_idx : ↑j1 ≥ ↑idx
j2 : Fin units.size
j2_ge_idx : ↑j2 ≥ ↑idx
i_gt_zero : ↑i > 0
ih1 : units[↑j1] = (⟨↑i, ⋯⟩, true)
ih2 : units[↑j2] = (⟨↑i, ⋯⟩, false)
ih3 : assignments[↑i] = both
ih4 : f.assignments[↑i] = unassigned
ih5 : ∀ (k : Fin units.size), ↑k ≥ ↑idx → ¬k = j1 → ¬k = j2 → ¬units[↑k].fst.val = ↑i
h✝ : ¬idx = j1
⊢ 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
Tactic:
. next idx_eq_j1 =>
  have idx_ne_j2 : idx ≠ j2 := by
    rw [idx_eq_j1]
    intro j1_eq_j2
    simp only [j1_eq_j2, ih2, Prod.mk.injEq, and_false] at ih1
  refine Or.inr <| Or.inl <| ⟨j2, false, i_gt_zero, ?_⟩
  constructor
  . apply Nat.le_of_lt_succ
    rw [← Nat.succ_eq_add_one]
    apply Nat.succ_lt_succ ∘ Nat.lt_of_le_of_ne j2_ge_idx
    intro idx_eq_j2
    exact idx_ne_j2 (Fin.eq_of_val_eq idx_eq_j2)
  . constructor
    . simp only [Fin.getElem_fin]
      exact ih2
    . constructor
      . simp only [clearUnit, idx_eq_j1, Array.get_eq_getElem, ih1]
        have i_in_bounds : i.1 < assignments.size := hsize ▸ i.2
        rw [Array.get_modify_at_idx i_in_bounds, ih3, ih4]
        decide
      . constructor
        . simp only [hasAssignment, hasNegAssignment, ih4, ite_false, not_false_eq_true]
        . intro k k_ge_idx_add_one k_ne_j2
          intro h1
          by_cases units[k.1].2
          . next h2 =>
            have k_ne_j1 : k ≠ j1 := by
              rw [← idx_eq_j1]
              intro k_eq_idx
              rw [k_eq_idx] at k_ge_idx_add_one
              exact Nat.lt_irrefl idx.1 $ Nat.lt_of_succ_le k_ge_idx_add_one
            have h3 := units_nodup k j1 k_ne_j1
            simp only [Fin.getElem_fin, ih1, ← h1, ← h2, ne_eq] at h3
            exact h3 rfl
          . next h2 =>
            have h3 := units_nodup k j2 k_ne_j2
            simp only [Bool.not_eq_true] at h2
            simp only [Fin.getElem_fin, ih2, ← h1, ← h2, ne_eq] at h3
            exact h3 rfl
Proof state after:
case neg
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
j1 : Fin units.size
j1_ge_idx : ↑j1 ≥ ↑idx
j2 : Fin units.size
j2_ge_idx : ↑j2 ≥ ↑idx
i_gt_zero : ↑i > 0
ih1 : units[↑j1] = (⟨↑i, ⋯⟩, true)
ih2 : units[↑j2] = (⟨↑i, ⋯⟩, false)
ih3 : assignments[↑i] = both
ih4 : f.assignments[↑i] = unassigned
ih5 : ∀ (k : Fin units.size), ↑k ≥ ↑idx → ¬k = j1 → ¬k = j2 → ¬units[↑k].fst.val = ↑i
h✝ : ¬idx = j1
⊢ 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