37 lines
654 B
Rust
37 lines
654 B
Rust
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// check-pass
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// compile-flags: -Ztrait-solver=next
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#![feature(rustc_attrs, marker_trait_attr)]
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#[rustc_coinductive]
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trait Trait {}
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impl<T, U> Trait for (T, U)
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where
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(U, T): Trait,
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(T, U): Inductive,
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(): ConstrainToU32<T>,
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{}
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trait ConstrainToU32<T> {}
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impl ConstrainToU32<u32> for () {}
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// We only prefer the candidate without an inductive cycle
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// once the inductive cycle has the same constraints as the
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// other goal.
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#[marker]
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trait Inductive {}
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impl<T, U> Inductive for (T, U)
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where
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(T, U): Trait,
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{}
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impl Inductive for (u32, u32) {}
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fn impls_trait<T, U>()
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where
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(T, U): Trait,
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{}
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fn main() {
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impls_trait::<_, _>();
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}
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