如何在具有生命周期的结构上实现标记特征？

Question

Given a struct that has a lifetime, how can I provide a marker-trait for it.

struct UserProvidedID<'a> { field: &'a str, }
impl warp::reject::Reject for UserProvidedID<'_> {}

Note this trait otherwise does what I want, I just want to "mark" it. I don't want to change the lifetime semantics.

Answer 1

The definition of Reject is the following:

pub trait Reject: Debug + Sized + Send + Sync + 'static { }

Notice the 'static , which means any type you want to implement Reject for needs to accept the 'static lifetime. Therefore, the only possibility is to use the static lifetime in your struct too :

struct UserProvidedID<'a> { field: &'a str, }
impl Reject for UserProvidedID<'static> {}

This might not be what you want, but given the definition of Reject , in a crate I assume is not yours, this is your only option.