∀ {α : Type u} {β : α → Type v} {x : BEq α} {x_1 : Hashable α} [inst : EquivBEq α] [inst_1 : LawfulHashable α]
  (m m_1 : Std.ExtDHashMap α β), m = m_1 → ∀ (a : α) (b b_1 : β a), b = b_1 → m.insertIfNew a b = m_1.insertIfNew a b_1