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Rollup merge of #139791 - lcnr:ignore-global-where-bounds, r=compiler-errors

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drop global where-bounds before merging candidates

fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/172

r? ```@compiler-errors```
This commit is contained in:
Stuart Cook 2025-04-15 15:47:30 +10:00 • committed by GitHub
commit e8c9dcc79e
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5 changed files with 93 additions and 6 deletions
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8
compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
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@ -1256,10 +1256,11 @@ where
D: SolverDelegate<Interner = I>,
I: Interner,
{
#[instrument(level = "debug", skip(self, goal), ret)]
pub(super) fn merge_trait_candidates(
&mut self,
goal: Goal<I, TraitPredicate<I>>,
candidates: Vec<Candidate<I>>,
mut candidates: Vec<Candidate<I>>,
) -> Result<(CanonicalResponse<I>, Option<TraitGoalProvenVia>), NoSolution> {
if let TypingMode::Coherence = self.typing_mode() {
let all_candidates: Vec<_> = candidates.into_iter().map(|c| c.result).collect();
@ -1341,13 +1342,16 @@ where
// If there are *only* global where bounds, then make sure to return that this
// is still reported as being proven-via the param-env so that rigid projections
// operate correctly.
// operate correctly. Otherwise, drop all global where-bounds before merging the
// remaining candidates.
let proven_via =
if candidates.iter().all(|c| matches!(c.source, CandidateSource::ParamEnv(_))) {
TraitGoalProvenVia::ParamEnv
} else {
candidates.retain(|c| !matches!(c.source, CandidateSource::ParamEnv(_)));
TraitGoalProvenVia::Misc
};
let all_candidates: Vec<_> = candidates.into_iter().map(|c| c.result).collect();
if let Some(response) = self.try_merge_responses(&all_candidates) {
Ok((response, Some(proven_via)))