{motive : Mathlib.Linter.UnusedInstancesInType.InstanceOfConcern✝ → Sort u} →
  (t : Mathlib.Linter.UnusedInstancesInType.InstanceOfConcern✝¹) →
    ((fvarId : Lean.FVarId) → (idx : ℕ) → motive { fvarId := fvarId, idx := idx }) → motive t