bjoernager/rust
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For a rigid projection, recursively look at the self type's item bounds

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This commit is contained in:
Michael Goulet 2024-02-01 23:48:04 +00:00
parent 98aa3624be
commit 22d582a38d
23 changed files with 273 additions and 431 deletions
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54
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
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@ -6,13 +6,16 @@
//!
//! [rustc dev guide]:https://rustc-dev-guide.rust-lang.org/traits/resolution.html#candidate-assembly
use std::ops::ControlFlow;
use hir::def_id::DefId;
use hir::LangItem;
use rustc_data_structures::fx::FxHashSet;
use rustc_hir as hir;
use rustc_infer::traits::ObligationCause;
use rustc_infer::traits::{Obligation, PolyTraitObligation, SelectionError};
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_middle::ty::{self, Ty, TypeVisitableExt};
use rustc_middle::ty::{self, ToPolyTraitRef, Ty, TypeVisitableExt};
use crate::traits;
use crate::traits::query::evaluate_obligation::InferCtxtExt;
@ -158,11 +161,52 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
_ => return,
}
let result = self
.infcx
.probe(|_| self.match_projection_obligation_against_definition_bounds(obligation));
self.infcx.probe(|_| {
let poly_trait_predicate = self.infcx.resolve_vars_if_possible(obligation.predicate);
let placeholder_trait_predicate =
self.infcx.enter_forall_and_leak_universe(poly_trait_predicate);
debug!(?placeholder_trait_predicate);
candidates.vec.extend(result.into_iter().map(|idx| ProjectionCandidate(idx)));
// The bounds returned by `item_bounds` may contain duplicates after
// normalization, so try to deduplicate when possible to avoid
// unnecessary ambiguity.
let mut distinct_normalized_bounds = FxHashSet::default();
self.for_each_item_bound::<!>(
placeholder_trait_predicate.self_ty(),
|selcx, bound, idx| {
let Some(bound) = bound.as_trait_clause() else {
return ControlFlow::Continue(());
};
if bound.polarity() != placeholder_trait_predicate.polarity {
return ControlFlow::Continue(());
}
selcx.infcx.probe(|_| {
match selcx.match_normalize_trait_ref(
obligation,
bound.to_poly_trait_ref(),
placeholder_trait_predicate.trait_ref,
) {
Ok(None) => {
candidates.vec.push(ProjectionCandidate(idx));
}
Ok(Some(normalized_trait))
if distinct_normalized_bounds.insert(normalized_trait) =>
{
candidates.vec.push(ProjectionCandidate(idx));
}
_ => {}
}
});
ControlFlow::Continue(())
},
|| {
// On ambiguity.
candidates.ambiguous = true;
},
);
});
}
/// Given an obligation like `<SomeTrait for T>`, searches the obligations that the caller