Theorem: LRAT.DefaultFormula.confirmRupHint_preserves_invariant_helper
Proof state before:
case inr.inr.intro.intro.intro.intro.intro.intro.intro.intro
n : Nat
f : DefaultFormula n
f_assignments_size : f.assignments.size = n
acc : Array Assignment × List (Literal (PosFin n)) × Bool × Bool
hsize : acc.fst.size = n
l : Literal (PosFin n)
ih : f.derivedLits_invariant f_assignments_size acc.fst hsize acc.snd.fst
h : ¬hasAssignment l.snd acc.fst[l.fst.val]! = true
hsize'✝ : (acc.fst.modify l.fst.val (addAssignment l.snd)).size = n :=
  Eq.mpr (id (congrArg (fun _a => _a = n) Array.modify_preserves_size)) hsize
i : Fin n
i_in_bounds : ↑i < acc.fst.size
l_in_bounds : l.fst.val < acc.fst.size
j1 j2 : Fin acc.snd.fst.length
j1_eq_i : (acc.snd.fst.get j1).fst.val = ↑i
j2_eq_i : (acc.snd.fst.get j2).fst.val = ↑i
j1_eq_true : (acc.snd.fst.get j1).snd = true
j2_eq_false : (acc.snd.fst.get j2).snd = false
h1 : acc.fst[↑i] = both
h2 : f.assignments[↑i] = unassigned
h3 : ∀ (k : Fin acc.snd.fst.length), k ≠ j1 → k ≠ j2 → (acc.snd.fst.get k).fst.val ≠ ↑i
j1_succ_in_bounds : ↑j1 + 1 < (l :: acc.snd.fst).length
j2_succ_in_bounds : ↑j2 + 1 < (l :: acc.snd.fst).length
j1_succ : Fin (l :: acc.snd.fst).length := ⟨↑j1 + 1, j1_succ_in_bounds⟩
j2_succ : Fin (l :: acc.snd.fst).length := ⟨↑j2 + 1, j2_succ_in_bounds⟩
⊢ (acc.fst.modify l.fst.val (addAssignment l.snd))[↑i] = both ∧
    f.assignments[↑i] = unassigned ∧
      ∀ (k : Fin acc.snd.fst.length.succ), ¬k = j1_succ → ¬k = j2_succ → ¬((l :: acc.snd.fst).get k).fst.val = ↑i
Tactic:
have l_ne_i : l.1.1 ≠ i.1 := by
  intro l_eq_i
  simp only [hasAssignment, Bool.not_eq_true] at h
  split at h
  all_goals
    simp (config := {decide := true}) [getElem!, l_eq_i, i_in_bounds, h1] at h
Proof state after:
case inr.inr.intro.intro.intro.intro.intro.intro.intro.intro
n : Nat
f : DefaultFormula n
f_assignments_size : f.assignments.size = n
acc : Array Assignment × List (Literal (PosFin n)) × Bool × Bool
hsize : acc.fst.size = n
l : Literal (PosFin n)
ih : f.derivedLits_invariant f_assignments_size acc.fst hsize acc.snd.fst
h : ¬hasAssignment l.snd acc.fst[l.fst.val]! = true
hsize'✝ : (acc.fst.modify l.fst.val (addAssignment l.snd)).size = n :=
  Eq.mpr (id (congrArg (fun _a => _a = n) Array.modify_preserves_size)) hsize
i : Fin n
i_in_bounds : ↑i < acc.fst.size
l_in_bounds : l.fst.val < acc.fst.size
j1 j2 : Fin acc.snd.fst.length
j1_eq_i : (acc.snd.fst.get j1).fst.val = ↑i
j2_eq_i : (acc.snd.fst.get j2).fst.val = ↑i
j1_eq_true : (acc.snd.fst.get j1).snd = true
j2_eq_false : (acc.snd.fst.get j2).snd = false
h1 : acc.fst[↑i] = both
h2 : f.assignments[↑i] = unassigned
h3 : ∀ (k : Fin acc.snd.fst.length), k ≠ j1 → k ≠ j2 → (acc.snd.fst.get k).fst.val ≠ ↑i
j1_succ_in_bounds : ↑j1 + 1 < (l :: acc.snd.fst).length
j2_succ_in_bounds : ↑j2 + 1 < (l :: acc.snd.fst).length
j1_succ : Fin (l :: acc.snd.fst).length := ⟨↑j1 + 1, j1_succ_in_bounds⟩
j2_succ : Fin (l :: acc.snd.fst).length := ⟨↑j2 + 1, j2_succ_in_bounds⟩
l_ne_i : l.fst.val ≠ ↑i
⊢ (acc.fst.modify l.fst.val (addAssignment l.snd))[↑i] = both ∧
    f.assignments[↑i] = unassigned ∧
      ∀ (k : Fin acc.snd.fst.length.succ), ¬k = j1_succ → ¬k = j2_succ → ¬((l :: acc.snd.fst).get k).fst.val = ↑i