trait Tr {
    fn trim_indent(&self) -> &Self;
}

impl Tr for str {
    fn trim_indent(&self) -> &Self {
        &self[..1] // some transformation here
    }
}

trait Tr1 {
    fn trim_indent(self) -> Self;
}

impl<'a> Tr1 for &'a str {
    fn trim_indent(self) -> Self {
        &self[..1] // some transformation here
    }
}


fn main() {
    let _: Box<Tr> = unimplemented!();
    let _: Box<Tr1> = unimplemented!();
    let func = <str as Tr>::trim_indent;
    let func = <&str as Tr1>::trim_indent;
}