(motive : List Lean.Meta.RefinedDiscrTree.Key → Sort u_1) →
  (rest : List Lean.Meta.RefinedDiscrTree.Key) →
    ((key : Lean.Meta.RefinedDiscrTree.Key) → (rest : List Lean.Meta.RefinedDiscrTree.Key) → motive (key :: rest)) →
      ((x : List Lean.Meta.RefinedDiscrTree.Key) → motive x) → motive rest