{motive : Lean.EnvExtension.AsyncMode → Sort u} →
  (t : Lean.EnvExtension.AsyncMode) →
    motive Lean.EnvExtension.AsyncMode.sync →
      ((branch : Lean.AsyncBranch) → motive (Lean.EnvExtension.AsyncMode.async branch)) →
        (Nat.hasNotBit 9 t.ctorIdx → motive t) → motive t