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use std::marker::PhantomData;
pub struct S;
pub struct K;
pub struct I;
pub struct S1<X>(pub PhantomData<X>);
pub struct S2<X, Y>(pub PhantomData<(X, Y)>);
pub struct K1<X>(pub PhantomData<X>);
pub trait A<In> {
type O;
}
impl<T> A<T> for S {
type O = S1<T>;
}
impl<X, T> A<T> for S1<X> {
type O = S2<X, T>;
}
impl<X, Y, T> A<T> for S2<X, Y>
where X: A<T>, Y: A<T>, <X as A<T>>::O: A<<Y as A<T>>::O>
{
type O = <<X as A<T>>::O as A<<Y as A<T>>::O>>::O;
}
impl<T> A<T> for K {
type O = K1<T>;
}
impl<X, T> A<T> for K1<X> {
type O = X;
}
impl<T> A<T> for I {
type O = T;
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn it_works() {
let _: <<<S as A<K>>::O as A<I>>::O as A<K>>::O;
assert!(false);
}
}