* `'b: 'a`: generic lifetime `'b` must outlive lifetime `'a`.
* `T: ?Sized`: allow generic type parameter to be a dynamically-sized type. See [Unsized Types (`?Sized`)].
* `'a + trait`, `trait + trait`: compound type constraint. See [Traits (Multiple Trait Bounds)].
* `'b: 'a`: generic lifetime `'b` must outlive lifetime `'a`.
* `T: ?Sized`: allow generic type parameter to be a dynamically-sized type. See [Unsized Types (`?Sized`)].
* `'a + trait`, `trait + trait`: compound type constraint. See [Traits (Multiple Trait Bounds)].