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Report higher-ranked trait error when higher-ranked projection goal fails in new solver

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This commit is contained in:
Michael Goulet 2025-04-08 05:18:17 +00:00
parent f06e5c1e35
commit f6faaee372
7 changed files with 122 additions and 38 deletions
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36
compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs
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@ -291,6 +291,34 @@ impl<'tcx> BestObligation<'tcx> {
}
}
/// When a higher-ranked projection goal fails, check that the corresponding
/// higher-ranked trait goal holds or not. This is because the process of
/// instantiating and then re-canonicalizing the binder of the projection goal
/// forces us to be unable to see that the leak check failed in the nested
/// `NormalizesTo` goal, so we don't fall back to the rigid projection check
/// that should catch when a projection goal fails due to an unsatisfied trait
/// goal.
fn detect_error_in_higher_ranked_projection(
&mut self,
goal: &inspect::InspectGoal<'_, 'tcx>,
) -> ControlFlow<PredicateObligation<'tcx>> {
let tcx = goal.infcx().tcx;
if let Some(projection_clause) = goal.goal().predicate.as_projection_clause()
&& !projection_clause.bound_vars().is_empty()
{
let pred = projection_clause.map_bound(|proj| proj.projection_term.trait_ref(tcx));
self.with_derived_obligation(self.obligation.with(tcx, pred), |this| {
goal.infcx().visit_proof_tree_at_depth(
goal.goal().with(tcx, pred),
goal.depth() + 1,
this,
)
})
} else {
ControlFlow::Continue(())
}
}
/// It is likely that `NormalizesTo` failed without any applicable candidates
/// because the alias is not well-formed.
///
@ -374,7 +402,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
source: CandidateSource::Impl(impl_def_id),
result: _,
} = candidate.kind()
&& goal.infcx().tcx.do_not_recommend_impl(impl_def_id)
&& tcx.do_not_recommend_impl(impl_def_id)
{
trace!("#[do_not_recommend] -> exit");
return ControlFlow::Break(self.obligation.clone());
@ -486,7 +514,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
if let Some(obligation) = goal
.infcx()
.visit_proof_tree_at_depth(
goal.goal().with(goal.infcx().tcx, ty::ClauseKind::WellFormed(lhs.into())),
goal.goal().with(tcx, ty::ClauseKind::WellFormed(lhs.into())),
goal.depth() + 1,
self,
)
@ -496,7 +524,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
} else if let Some(obligation) = goal
.infcx()
.visit_proof_tree_at_depth(
goal.goal().with(goal.infcx().tcx, ty::ClauseKind::WellFormed(rhs.into())),
goal.goal().with(tcx, ty::ClauseKind::WellFormed(rhs.into())),
goal.depth() + 1,
self,
)
@ -506,6 +534,8 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
}
}
self.detect_error_in_higher_ranked_projection(goal)?;
ControlFlow::Break(self.obligation.clone())
}
}