Code shared from the Rust Playground

playground.rs

use std::io::Write;

struct Foo<W: Write> {
    out: W,
}

impl<W: Write> Foo<W> {
    fn exchange_out<W2: Write>(self, new: W2) -> (Foo<W2>, W) {
        let Foo { out } = self;
        (Foo { out: new }, out )
    }
}

fn main() {}