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//@ check-pass
#![feature(associated_type_defaults)]
// Having a cycle in assoc. type defaults is okay, as long as there's no impl
// that retains it.
trait Tr {
type A = Self::B;
type B = Self::A;
fn f();
}
// An impl has to break the cycle to be accepted.
impl Tr for u8 {
type A = u8;
fn f() {
// Check that the type propagates as expected (seen from inside the impl)
let _: Self::A = 0u8;
let _: Self::B = 0u8;
}
}
impl Tr for String {
type B = ();
fn f() {
// Check that the type propagates as expected (seen from inside the impl)
let _: Self::A = ();
let _: Self::B = ();
}
}
impl Tr for () {
type A = Vec<()>;
type B = u8;
fn f() {
// Check that the type propagates as expected (seen from inside the impl)
let _: Self::A = Vec::<()>::new();
let _: Self::B = 0u8;
}
}
fn main() {
// Check that both impls now have the right types (seen from outside the impls)
let _: <u8 as Tr>::A = 0u8;
let _: <u8 as Tr>::B = 0u8;
let _: <String as Tr>::A = ();
let _: <String as Tr>::B = ();
let _: <() as Tr>::A = Vec::<()>::new();
let _: <() as Tr>::B = 0u8;
}
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