#![feature(generic_associated_types)]

pub struct Structure<F> {
    f: F,
}

pub trait Trait {
    type Gat<'a>;
}

impl<F> Trait for Structure<F>
where
    for<'a> F: FnOnce(Self::Gat<'a>),
{
    type Gat<'a> = String;
}