#[cfg(test)]

mod tests {

    #[test]

    fn test() {
        trait Get<'a> {
            type Output: Constraints;

            fn get(self) -> Self::Output;
        }

        trait Constraints {}

        impl<'b> Constraints for &'b mut usize {}

        impl<'a> Get<'a> for &'a mut usize {
            type Output = &'a mut usize;

            fn get(self) -> Self::Output {
                self
            }
        }
    }
}