Trait Object Lifetime

• If a trait object contain references, the lifetimes need to be expressed as part of it. e.g Trait + 'a
• Compiler infers lifetime most of the time based on defaults

trait Foo { }

// these are the same because Box<T> has no lifetime bound on T
type T1 = Box<dyn Foo>;
type T2 = Box<dyn Foo + 'static>';

more details here