#![feature(marker_trait_attr)]

#[marker]
trait A {}

trait B {}

impl<T: A> B for T {}
impl<T: B> A for T {}
impl A for &str {}
impl<T: A + B> A for (T,) {}
// insert another line break around here and it stops compiling on nightly-2021-04-25
trait TraitWithAssoc {
    type Assoc;
}

impl<T: A> TraitWithAssoc for T {
    type Assoc = T;
}
// ^^^ vvv  these two impls should be overlapping
impl TraitWithAssoc for ((&str,),) {
    type Assoc = ((&'static str,),);
}

fn g<T: TraitWithAssoc<Assoc = ((&'static str,),)>>(x: T::Assoc) -> ((&'static str,),) {
    x
}

fn j<T: A + B>(
    x: (T,),
    f: fn(<(T,) as TraitWithAssoc>::Assoc) -> ((&'static str,),),
) -> ((&'static str,),) {
    f(x)
}

fn main() {
    let y;
    {
        let hello = "Hello World!".to_owned();
        y = j::<(&str,)>(((&hello,),), g::<((&str,),)>).0 .0;
    }
    println!("{}", y);
}