Code shared from the Rust Playground

playground.rs

trait Def<T> {
    fn def(&self, foo: T) -> bool;
}

impl<T, Func> Def<T> for Func
  where Func: Fn(T) -> bool
{
    fn def(&self, foo: T) -> bool {
        (self)(foo)
    }
}

fn doo(d: i32) -> bool {
    d > 0
}

fn main() {
    println!("{}", doo.def(5));
}