38 lines
1.2 KiB
Rust
38 lines
1.2 KiB
Rust
//@ check-pass
|
|
// Related to Bevy regression #115559, found in
|
|
// a crater run on #118553.
|
|
|
|
pub trait QueryBase {
|
|
type Db;
|
|
}
|
|
|
|
pub trait AsyncQueryFunction<'f>: // 'f is important
|
|
QueryBase<Db = <Self as AsyncQueryFunction<'f>>::SendDb> // bound is important
|
|
{
|
|
type SendDb;
|
|
}
|
|
|
|
pub struct QueryTable<'me, Q, DB> {
|
|
_q: Option<Q>,
|
|
_db: Option<DB>,
|
|
_marker: Option<&'me ()>,
|
|
}
|
|
|
|
impl<'me, Q> QueryTable<'me, Q, <Q as QueryBase>::Db>
|
|
where
|
|
Q: for<'f> AsyncQueryFunction<'f>,
|
|
{
|
|
// When borrowchechking this function we normalize `<Q as QueryBase>::Db` in the
|
|
// function signature to `<Self as QueryFunction<'?x>>::SendDb`, where `'?x` is an
|
|
// unconstrained region variable. We then addd `<Self as QueryFunction<'?x>>::SendDb: 'a`
|
|
// as an implied bound. We currently a structural equality to decide whether this bound
|
|
// should be used to prove the bound `<Self as QueryFunction<'?x>>::SendDb: 'a`. For this
|
|
// to work we may have to structurally resolve regions as the actually used vars may
|
|
// otherwise be semantically equal but structurally different.
|
|
pub fn get_async<'a>(&'a mut self) {
|
|
panic!();
|
|
}
|
|
}
|
|
|
|
fn main() {}
|