35 lines
900 B
Rust
35 lines
900 B
Rust
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// Checking the `Send` bound in `main` requires:
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//
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// checking <C<'static> as Y>::P: Send
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// which normalizes to Box<X<C<'?1>>>: Send
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// which needs X<C<'?1>>: Send
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// which needs <C<'?1> as Y>::P: Send
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//
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// At this point we used to normalize the predicate to `Box<X<C<'?2>>>: Send`
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// and continue in a loop where we created new region variables to the
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// recursion limit. To avoid this we now "canonicalize" region variables to
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// lowest unified region vid. This means we instead have to prove
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// `Box<X<C<'?1>>>: Send`, which we can because auto traits are coinductive.
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// check-pass
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// Avoid a really long error message if this regresses.
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#![recursion_limit="20"]
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trait Y {
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type P;
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}
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impl<'a> Y for C<'a> {
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type P = Box<X<C<'a>>>;
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}
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struct C<'a>(&'a ());
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struct X<T: Y>(T::P);
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fn is_send<S: Send>() {}
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fn main() {
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is_send::<X<C<'static>>>();
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}
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