First error: you create a Rustmark
object with the field parser
of type DefaultParser
and the field renderer
of type HTMLRenderer
, but the function is expected to return Rustmark <P, R>
. In general P is not of type DefaultParser
and R is not of type HTMLRenderer
, so it will never compile. A good solution if you want have default values of the right type is to bound P
and R
to implement the Default
trait
, this way:
use std::default:Default;
impl <P: MarkParser + Default, R: MarkRenderer + Default> Rustmark <P, R> {
fn new() -> Rustmark <P, R> {
Rustmark {
parser: P::default(),
renderer: R:default(),
}
}
}
Second error: that main problem is that you return a reference of something that probably will die inside the render
method (the String
you allocate in the inner render
method probably). The compiler is telling you that it doesn’t know the lifetime of the object that is pointed by that reference, so it cannot guarantee that the reference is valid. You can specify a lifetime parameter but in your case probably the best solution is to return the String
object itself, not a reference.