rust/tests/ui/impl-trait/wf-eval-order.rs

40 lines
738 B
Rust

// Check that we handle evaluating `wf` predicates correctly.
//@ check-pass
struct X<T: B>(T)
where
T::V: Clone;
fn hide<T>(t: T) -> impl Sized {
t
}
trait A {
type U;
}
impl<T> A for T {
type U = T;
}
trait B {
type V;
}
impl<S: A<U = T>, T> B for S {
type V = T;
}
fn main() {
// Evaluating `typeof(x): Sized` requires
//
// - `wf(typeof(x))` because we use a projection candidate.
// - `<i32 as B>::V: Clone` because that's a bound on the trait.
// - `<i32 as B>::V` normalizes to `?1t` where `<i32 as A>::U == ?1t`
//
// This all works if we evaluate `<i32 as A>::U == ?1t` before
// `<i32 as B>::V`, but we previously had the opposite order.
let x = hide(X(0));
}