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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 09:26:03 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 09:26:03 +0000 |
commit | 9918693037dce8aa4bb6f08741b6812923486c18 (patch) | |
tree | 21d2b40bec7e6a7ea664acee056eb3d08e15a1cf /tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.rs | |
parent | Releasing progress-linux version 1.75.0+dfsg1-5~progress7.99u1. (diff) | |
download | rustc-9918693037dce8aa4bb6f08741b6812923486c18.tar.xz rustc-9918693037dce8aa4bb6f08741b6812923486c18.zip |
Merging upstream version 1.76.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.rs')
-rw-r--r-- | tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.rs | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.rs b/tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.rs new file mode 100644 index 000000000..947b52da7 --- /dev/null +++ b/tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.rs @@ -0,0 +1,35 @@ +// compile-flags: -Znext-solver + +// Proving `W<?0>: Trait` instantiates `?0` with `(W<?1>, W<?2>)` and then +// proves `W<?1>: Trait` and `W<?2>: Trait`, resulting in a coinductive cycle. +// +// Proving coinductive cycles runs until we reach a fixpoint. However, after +// computing `try_evaluate_added_goals` in the second fixpoint iteration, the +// self type already has a depth equal to the number of steps. This results +// in enormous constraints, causing the canonicalizer to hang without ever +// reaching the recursion limit. We currently avoid that by erasing the constraints +// from overflow. +// +// This previously caused a hang in the trait solver, see +// https://github.com/rust-lang/trait-system-refactor-initiative/issues/13. + +#![feature(rustc_attrs)] + +#[rustc_coinductive] +trait Trait {} + +struct W<T>(T); + +impl<T, U> Trait for W<(W<T>, W<U>)> +where + W<T>: Trait, + W<U>: Trait, +{ +} + +fn impls<T: Trait>() {} + +fn main() { + impls::<W<_>>(); + //~^ ERROR overflow evaluating the requirement +} |