{α : Type u} →
  [inst : BEq α] →
    {motive : LawfulBEq α → Sort u_1} →
      (t : LawfulBEq α) →
        ([toReflBEq : ReflBEq α] → (eq_of_beq : ∀ {a b : α}, (a == b) = true → a = b) → motive ⋯) → motive t