91b9ffeab0
In `report_fullfillment_errors` push back `T: Sized`, `T: WellFormed` and coercion errors to the end of the list. The pre-existing deduplication logic eliminates redundant errors better that way, keeping the resulting output with fewer errors than before, while also having more detail.
32 lines
764 B
Rust
32 lines
764 B
Rust
// compile-flags: -Ztrait-solver=next
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// Proving `W<?0>: Trait` instantiates `?0` with `(W<?1>, W<?2>)` and then
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// proves `W<?1>: Trait` and `W<?2>: Trait`, resulting in a coinductive cycle.
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//
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// Proving coinductive cycles runs until we reach a fixpoint. This fixpoint is
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// never reached here and each step doubles the amount of nested obligations.
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//
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// This previously caused a hang in the trait solver, see
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// https://github.com/rust-lang/trait-system-refactor-initiative/issues/13.
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#![feature(rustc_attrs)]
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#[rustc_coinductive]
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trait Trait {}
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struct W<T>(T);
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impl<T, U> Trait for W<(W<T>, W<U>)>
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where
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W<T>: Trait,
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W<U>: Trait,
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{
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}
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fn impls<T: Trait>() {}
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fn main() {
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impls::<W<_>>();
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//~^ ERROR overflow evaluating the requirement
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}
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