∀ {w : ℕ} (ll lr : ℕ) (llhs : Std.Tactic.BVDecide.BVExpr ll) (lrhs : Std.Tactic.BVDecide.BVExpr lr) (lh : w = ll + lr)
  (rl rr : ℕ) (rlhs : Std.Tactic.BVDecide.BVExpr rl) (rrhs : Std.Tactic.BVDecide.BVExpr rr) (rh : w = rl + rr),
  ¬hash (llhs.append lrhs lh) ≠ hash (rlhs.append rrhs rh) →
    ∀ (h1 : ll = rl ∧ lr = rr) (x : Decidable (⋯ ▸ llhs = rlhs)),
      ¬⋯ ▸ lrhs = rrhs → ¬llhs.append lrhs lh = rlhs.append rrhs rh