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