rust/compiler/rustc_trait_selection
Matthias Krüger d55e2e4333
Rollup merge of #137314 - lcnr:cycles-with-unknown-kind, r=compiler-errors
change definitely unproductive cycles to error

builds on top of #136824 by adding a third variant to `PathKind` for paths which may change to be coinductive in the future but must not be so right now. Most notably, impl where-clauses of not yet coinductive traits.

With this, we can change cycles which are definitely unproductive to a proper error. This fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/114. This does not affect stable as we keep these cycles as ambiguous during coherence.

r? ````````@compiler-errors```````` ````````@nikomatsakis````````
2025-03-12 17:59:06 +01:00
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