lifetime-fight-001

ltf.rs

//=========== attempt 1 =============
trait Handler<'a> {
    fn handle(self, String) -> &'a str;
}

#[derive(Debug)]
struct TestHandle {
    uri: String,
}

impl<'a> Handler<'a> for TestHandle {
    fn handle(self, s: String) -> &'a str {
        format!("via {}", s)
    }
}
struct A<S>
    where S: Handler
{
    name: String,
    handler: Box<S>,
}

//error[E0106]: missing lifetime specifier
//  --> src/main.rs:18:14
//   |
//18 |     where S: Handler
//   |              ^^^^^^^ expected lifetime parameter
//
//error: aborting due to previous error

//===== attempt 2 =============

struct A<S>
    where S: Handler<'a>
{
    name: String,
    handler: Box<S>,
}

//Error:
//error[E0261]: use of undeclared lifetime name `'a`
//  --> src/main.rs:18:22
//   |
//18 |     where S: Handler<'a>
//   |                      ^^ undeclared lifetime

error: aborting due to previous error


// attempt 3 ===============
struct A<'a, S>
    where S: Handler<'a>
{
    name: String,
    handler: Box<S>,
}

//error[E0392]: parameter `'a` is never used
//  --> src/main.rs:17:10
//   |
//17 | struct A<'a, S>
//   |          ^^ unused type parameter
//   |
//   = help: consider removing `'a` or using a marker such as `std::marker::PhantomData`