#![feature(associated_type_defaults)]

struct S<T = u8>(T);
trait Tr<T = u8> {
    type A = ();
}

impl Tr<Self> for S {} // OK
impl<T: Tr<Self>> Tr<T> for S {} // OK
impl Tr for S where Self: Copy {} // OK
impl Tr for S where S<Self>: Copy {} // OK
impl Tr for S where Self::A: Copy {} // OK

impl Tr for Self {} //~ ERROR cycle detected
impl Tr for S<Self> {} //~ ERROR cycle detected
impl Self {} //~ ERROR cycle detected
impl S<Self> {} //~ ERROR cycle detected
impl Tr<Self::A> for S {} //~ ERROR cycle detected

fn main() {}