{motive : Lean.Expr → Sort u} →
  (t : Lean.Expr) →
    ((declName : Lean.Name) → (us : List Lean.Level) → motive (Lean.Expr.const declName us)) →
      ((fn arg : Lean.Expr) → motive (fn.app arg)) → (Nat.hasNotBit 48 t.ctorIdx → motive t) → motive t