42 lines
827 B
Rust
42 lines
827 B
Rust
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// check-pass
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// known-bug: #74629
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// Should fail. The `0` and `1` impls overlap, violating coherence. Eg, with
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// `T = Test, F = ()`, all bounds are true, making both impls applicable.
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// `Test: Fold<Nil>`, `Test: Fold<()>` are true because of `2`.
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// `Is<Test>: NotNil` is true because of `auto trait` and lack of negative impl.
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#![feature(negative_impls)]
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#![feature(auto_traits)]
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struct Nil;
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struct Cons<H>(H);
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struct Test;
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trait Fold<F> {}
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impl<T, F> Fold<F> for Cons<T> // 0
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where
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T: Fold<Nil>,
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{}
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impl<T, F> Fold<F> for Cons<T> // 1
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where
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T: Fold<F>,
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private::Is<T>: private::NotNil,
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{}
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impl<F> Fold<F> for Test {} // 2
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mod private {
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use crate::Nil;
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pub struct Is<T>(T);
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pub auto trait NotNil {}
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#[allow(suspicious_auto_trait_impls)]
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impl !NotNil for Is<Nil> {}
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}
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fn main() {}
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