∀ {α : Sort u_1} (ctx : Lean.Grind.AC.Context α) {inst₁ : Std.Associative ctx.op} {inst₂ : Std.IdempotentOp ctx.op}
  (x : Lean.Grind.AC.Var) (lhs₁ rhs₁ rhs : Lean.Grind.AC.Seq),
  Lean.Grind.AC.superpose_tail_idempotent_cert x lhs₁ rhs₁ rhs = true →
    Lean.Grind.AC.Seq.denote ctx lhs₁ = Lean.Grind.AC.Seq.denote ctx rhs₁ →
      Lean.Grind.AC.Seq.denote ctx lhs₁ = Lean.Grind.AC.Seq.denote ctx rhs