// this used to cause stack overflows trait Hrtb<'a> { type Assoc; } impl<'a> Hrtb<'a> for () { type Assoc = (); } impl<'a> Hrtb<'a> for &'a () { type Assoc = (); } fn make_impl() -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {} fn make_weird_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> { &() //~^ ERROR implementation of `Hrtb` is not general enough } fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> { x //~^ ERROR implementation of `Hrtb` is not general enough } fn main() {}