| //@ revisions: current next |
| //@ ignore-compare-mode-next-solver (explicit revisions) |
| //@[next] compile-flags: -Znext-solver |
| //@ check-pass |
| |
| // This caused a regression in a crater run in #132325. |
| // |
| // The underlying issue is a really subtle implementation detail. |
| // |
| // When building the `param_env` for `Trait` we start out with its |
| // explicit predicates `Self: Trait` and `Self: for<'a> Super<'a, { 1 + 1 }>`. |
| // |
| // When normalizing the environment we also elaborate. This implicitly |
| // deduplicates its returned predicates. We currently first eagerly |
| // normalize constants in the unnormalized param env to avoid issues |
| // caused by our lack of deferred alias equality. |
| // |
| // So we actually elaborate `Self: Trait` and `Self: for<'a> Super<'a, 2>`, |
| // resulting in a third `Self: for<'a> Super<'a, { 1 + 1 }>` predicate which |
| // then gets normalized to `Self: for<'a> Super<'a, 2>` at which point we |
| // do not deduplicate however. By failing to handle equal where-bounds in |
| // candidate selection, this caused ambiguity when checking that `Trait` is |
| // well-formed. |
| trait Super<'a, const N: usize> {} |
| trait Trait: for<'a> Super<'a, { 1 + 1 }> {} |
| fn main() {} |
