--- /dev/null
+//! Code shared by trait and projection goals for candidate assembly.
+
+use super::infcx_ext::InferCtxtExt;
+use super::{
+ fixme_instantiate_canonical_query_response, CanonicalGoal, CanonicalResponse, Certainty,
+ EvalCtxt, Goal,
+};
+use rustc_hir::def_id::DefId;
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::infer::{
+ canonical::{CanonicalVarValues, OriginalQueryValues},
+ InferCtxt,
+};
+use rustc_infer::traits::query::NoSolution;
+use rustc_middle::ty::TypeFoldable;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::DUMMY_SP;
+use std::fmt::Debug;
+
+/// A candidate is a possible way to prove a goal.
+///
+/// It consists of both the `source`, which describes how that goal would be proven,
+/// and the `result` when using the given `source`.
+///
+/// For the list of possible candidates, please look at the documentation of
+/// [super::trait_goals::CandidateSource] and [super::project_goals::CandidateSource].
+#[derive(Debug, Clone)]
+pub(super) struct Candidate<'tcx, G: GoalKind<'tcx>> {
+ pub(super) source: G::CandidateSource,
+ pub(super) result: CanonicalResponse<'tcx>,
+}
+
+pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy {
+ type CandidateSource: Debug + Copy;
+
+ fn self_ty(self) -> Ty<'tcx>;
+
+ fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self;
+
+ fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId;
+
+ fn consider_impl_candidate(
+ acx: &mut AssemblyCtxt<'_, 'tcx, Self>,
+ goal: Goal<'tcx, Self>,
+ impl_def_id: DefId,
+ );
+}
+
+/// An abstraction which correctly deals with the canonical results for candidates.
+///
+/// It also deduplicates the behavior between trait and projection predicates.
+pub(super) struct AssemblyCtxt<'a, 'tcx, G: GoalKind<'tcx>> {
+ pub(super) cx: &'a mut EvalCtxt<'tcx>,
+ pub(super) infcx: &'a InferCtxt<'tcx>,
+ var_values: CanonicalVarValues<'tcx>,
+ candidates: Vec<Candidate<'tcx, G>>,
+}
+
+impl<'a, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'tcx, G> {
+ pub(super) fn assemble_and_evaluate_candidates(
+ cx: &'a mut EvalCtxt<'tcx>,
+ goal: CanonicalGoal<'tcx, G>,
+ ) -> Vec<Candidate<'tcx, G>> {
+ let (ref infcx, goal, var_values) =
+ cx.tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &goal);
+ let mut acx = AssemblyCtxt { cx, infcx, var_values, candidates: Vec::new() };
+
+ acx.assemble_candidates_after_normalizing_self_ty(goal);
+
+ acx.assemble_impl_candidates(goal);
+
+ acx.candidates
+ }
+
+ pub(super) fn try_insert_candidate(
+ &mut self,
+ source: G::CandidateSource,
+ certainty: Certainty,
+ ) {
+ match self.infcx.make_canonical_response(self.var_values.clone(), certainty) {
+ Ok(result) => self.candidates.push(Candidate { source, result }),
+ Err(NoSolution) => debug!(?source, ?certainty, "failed leakcheck"),
+ }
+ }
+
+ /// If the self type of a goal is a projection, computing the relevant candidates is difficult.
+ ///
+ /// To deal with this, we first try to normalize the self type and add the candidates for the normalized
+ /// self type to the list of candidates in case that succeeds. Note that we can't just eagerly return in
+ /// this case as projections as self types add `
+ fn assemble_candidates_after_normalizing_self_ty(&mut self, goal: Goal<'tcx, G>) {
+ let tcx = self.cx.tcx;
+ // FIXME: We also have to normalize opaque types, not sure where to best fit that in.
+ let &ty::Alias(ty::Projection, projection_ty) = goal.predicate.self_ty().kind() else {
+ return
+ };
+ self.infcx.probe(|_| {
+ let normalized_ty = self.infcx.next_ty_infer();
+ let normalizes_to_goal = goal.with(
+ tcx,
+ ty::Binder::dummy(ty::ProjectionPredicate {
+ projection_ty,
+ term: normalized_ty.into(),
+ }),
+ );
+ let normalization_certainty =
+ match self.cx.evaluate_goal(&self.infcx, normalizes_to_goal) {
+ Ok((_, certainty)) => certainty,
+ Err(NoSolution) => return,
+ };
+
+ // NOTE: Alternatively we could call `evaluate_goal` here and only have a `Normalized` candidate.
+ // This doesn't work as long as we use `CandidateSource` in both winnowing and to resolve associated items.
+ let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty));
+ let mut orig_values = OriginalQueryValues::default();
+ let goal = self.infcx.canonicalize_query(goal, &mut orig_values);
+ let normalized_candidates =
+ AssemblyCtxt::assemble_and_evaluate_candidates(self.cx, goal);
+
+ // Map each candidate from being canonical wrt the current inference context to being
+ // canonical wrt the caller.
+ for Candidate { source, result } in normalized_candidates {
+ self.infcx.probe(|_| {
+ let candidate_certainty = fixme_instantiate_canonical_query_response(
+ &self.infcx,
+ &orig_values,
+ result,
+ );
+
+ // FIXME: This is a bit scary if the `normalizes_to_goal` overflows.
+ //
+ // If we have an ambiguous candidate it hides that normalization
+ // caused an overflow which may cause issues.
+ self.try_insert_candidate(
+ source,
+ normalization_certainty.unify_and(candidate_certainty),
+ )
+ })
+ }
+ })
+ }
+
+ fn assemble_impl_candidates(&mut self, goal: Goal<'tcx, G>) {
+ self.cx.tcx.for_each_relevant_impl(
+ goal.predicate.trait_def_id(self.cx.tcx),
+ goal.predicate.self_ty(),
+ |impl_def_id| G::consider_impl_candidate(self, goal, impl_def_id),
+ );
+ }
+}
use self::infcx_ext::InferCtxtExt;
+mod assembly;
mod cache;
mod fulfill;
mod infcx_ext;
use crate::traits::{specialization_graph, translate_substs};
-use super::infcx_ext::InferCtxtExt;
-use super::{
- fixme_instantiate_canonical_query_response, CanonicalGoal, CanonicalResponse, Certainty,
- EvalCtxt, Goal, QueryResult,
-};
+use super::assembly::{self, AssemblyCtxt};
+use super::{CanonicalGoal, EvalCtxt, Goal, QueryResult};
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
-use rustc_infer::infer::canonical::{CanonicalVarValues, OriginalQueryValues};
-use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
+use rustc_infer::infer::{InferCtxt, InferOk};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::specialization_graph::LeafDef;
use rustc_infer::traits::{ObligationCause, Reveal};
-use rustc_middle::ty;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_middle::ty::ProjectionPredicate;
use rustc_middle::ty::TypeVisitable;
+use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP;
use std::iter;
-// FIXME: Deduplicate the candidate code between projection and trait goal.
-
-/// Similar to [super::trait_goals::Candidate] but for `Projection` goals.
-#[derive(Debug, Clone)]
-struct Candidate<'tcx> {
- source: CandidateSource,
- result: CanonicalResponse<'tcx>,
-}
-
#[allow(dead_code)] // FIXME: implement and use all variants.
#[derive(Debug, Clone, Copy)]
-enum CandidateSource {
+pub(super) enum CandidateSource {
Impl(DefId),
ParamEnv(usize),
Builtin,
}
+type Candidate<'tcx> = assembly::Candidate<'tcx, ProjectionPredicate<'tcx>>;
+
impl<'tcx> EvalCtxt<'tcx> {
pub(super) fn compute_projection_goal(
&mut self,
goal: CanonicalGoal<'tcx, ProjectionPredicate<'tcx>>,
) -> QueryResult<'tcx> {
- let candidates = self.assemble_and_evaluate_project_candidates(goal);
+ let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
self.merge_project_candidates(candidates)
}
- fn assemble_and_evaluate_project_candidates(
- &mut self,
- goal: CanonicalGoal<'tcx, ProjectionPredicate<'tcx>>,
- ) -> Vec<Candidate<'tcx>> {
- let (ref infcx, goal, var_values) =
- self.tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &goal);
- let mut acx = AssemblyCtxt { cx: self, infcx, var_values, candidates: Vec::new() };
-
- acx.assemble_candidates_after_normalizing_self_ty(goal);
- acx.assemble_impl_candidates(goal);
- acx.candidates
- }
-
fn merge_project_candidates(
&mut self,
mut candidates: Vec<Candidate<'tcx>>,
}
}
-/// Similar to [super::trait_goals::AssemblyCtxt] but for `Projection` goals.
-struct AssemblyCtxt<'a, 'tcx> {
- cx: &'a mut EvalCtxt<'tcx>,
- infcx: &'a InferCtxt<'tcx>,
- var_values: CanonicalVarValues<'tcx>,
- candidates: Vec<Candidate<'tcx>>,
-}
+impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
+ type CandidateSource = CandidateSource;
-impl<'tcx> AssemblyCtxt<'_, 'tcx> {
- fn try_insert_candidate(&mut self, source: CandidateSource, certainty: Certainty) {
- match self.infcx.make_canonical_response(self.var_values.clone(), certainty) {
- Ok(result) => self.candidates.push(Candidate { source, result }),
- Err(NoSolution) => debug!(?source, ?certainty, "failed leakcheck"),
- }
+ fn self_ty(self) -> Ty<'tcx> {
+ self.self_ty()
}
- fn assemble_candidates_after_normalizing_self_ty(
- &mut self,
- goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
- ) {
- let tcx = self.cx.tcx;
- let &ty::Alias(ty::Projection, projection_ty) = goal.predicate.projection_ty.self_ty().kind() else {
- return
- };
- self.infcx.probe(|_| {
- let normalized_ty = self.infcx.next_ty_infer();
- let normalizes_to_goal = goal.with(
- tcx,
- ty::Binder::dummy(ty::ProjectionPredicate {
- projection_ty,
- term: normalized_ty.into(),
- }),
- );
- let normalization_certainty =
- match self.cx.evaluate_goal(&self.infcx, normalizes_to_goal) {
- Ok((_, certainty)) => certainty,
- Err(NoSolution) => return,
- };
-
- // NOTE: Alternatively we could call `evaluate_goal` here and only have a `Normalized` candidate.
- // This doesn't work as long as we use `CandidateSource` in both winnowing and to resolve associated items.
- let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty));
- let mut orig_values = OriginalQueryValues::default();
- let goal = self.infcx.canonicalize_query(goal, &mut orig_values);
- let normalized_candidates = self.cx.assemble_and_evaluate_project_candidates(goal);
- // Map each candidate from being canonical wrt the current inference context to being
- // canonical wrt the caller.
- for Candidate { source, result } in normalized_candidates {
- self.infcx.probe(|_| {
- let candidate_certainty = fixme_instantiate_canonical_query_response(
- self.infcx,
- &orig_values,
- result,
- );
- self.try_insert_candidate(
- source,
- normalization_certainty.unify_and(candidate_certainty),
- )
- })
- }
- })
+ fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
+ self.with_self_ty(tcx, self_ty)
}
- fn assemble_impl_candidates(&mut self, goal: Goal<'tcx, ProjectionPredicate<'tcx>>) {
- self.cx.tcx.for_each_relevant_impl(
- goal.predicate.trait_def_id(self.cx.tcx),
- goal.predicate.self_ty(),
- |impl_def_id| self.consider_impl_candidate(goal, impl_def_id),
- );
+ fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId {
+ self.trait_def_id(tcx)
}
fn consider_impl_candidate(
- &mut self,
+ acx: &mut AssemblyCtxt<'_, 'tcx, ProjectionPredicate<'tcx>>,
goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
impl_def_id: DefId,
) {
- let tcx = self.cx.tcx;
+ let tcx = acx.cx.tcx;
let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
let impl_trait_ref = tcx.bound_impl_trait_ref(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
return;
}
- self.infcx.probe(|_| {
- let impl_substs = self.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
+ acx.infcx.probe(|_| {
+ let impl_substs = acx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
- let Ok(InferOk { obligations, .. }) = self
+ let Ok(InferOk { obligations, .. }) = acx
.infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
};
let nested_goals = obligations.into_iter().map(|o| o.into()).collect();
- let Ok(trait_ref_certainty) = self.cx.evaluate_all(self.infcx, nested_goals) else { return };
+ let Ok(trait_ref_certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
- let Some(assoc_def) = self.fetch_eligible_assoc_item_def(
+ let Some(assoc_def) = fetch_eligible_assoc_item_def(
+ acx.infcx,
goal.param_env,
goal_trait_ref,
goal.predicate.def_id(),
impl_trait_ref.substs,
);
let substs = translate_substs(
- self.infcx,
+ acx.infcx,
goal.param_env,
impl_def_id,
impl_substs_with_gat,
ty.map_bound(|ty| ty.into())
};
- let Ok(InferOk { obligations, .. }) = self
+ let Ok(InferOk { obligations, .. }) = acx
.infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
};
let nested_goals = obligations.into_iter().map(|o| o.into()).collect();
- let Ok(rhs_certainty) = self.cx.evaluate_all(self.infcx, nested_goals) else { return };
+ let Ok(rhs_certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
let certainty = trait_ref_certainty.unify_and(rhs_certainty);
- self.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
+ acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
})
}
+}
- /// This behavior is also implemented in `rustc_ty_utils` and in the old `project` code.
- ///
- /// FIXME: We should merge these 3 implementations as it's likely that they otherwise
- /// diverge.
- #[instrument(level = "debug", skip(self, param_env), ret)]
- fn fetch_eligible_assoc_item_def(
- &self,
- param_env: ty::ParamEnv<'tcx>,
- goal_trait_ref: ty::TraitRef<'tcx>,
- trait_assoc_def_id: DefId,
- impl_def_id: DefId,
- ) -> Option<LeafDef> {
- let node_item =
- specialization_graph::assoc_def(self.cx.tcx, impl_def_id, trait_assoc_def_id)
- .map_err(|ErrorGuaranteed { .. }| ())
- .ok()?;
-
- let eligible = if node_item.is_final() {
- // Non-specializable items are always projectable.
- true
+/// This behavior is also implemented in `rustc_ty_utils` and in the old `project` code.
+///
+/// FIXME: We should merge these 3 implementations as it's likely that they otherwise
+/// diverge.
+#[instrument(level = "debug", skip(infcx, param_env), ret)]
+fn fetch_eligible_assoc_item_def<'tcx>(
+ infcx: &InferCtxt<'tcx>,
+ param_env: ty::ParamEnv<'tcx>,
+ goal_trait_ref: ty::TraitRef<'tcx>,
+ trait_assoc_def_id: DefId,
+ impl_def_id: DefId,
+) -> Option<LeafDef> {
+ let node_item = specialization_graph::assoc_def(infcx.tcx, impl_def_id, trait_assoc_def_id)
+ .map_err(|ErrorGuaranteed { .. }| ())
+ .ok()?;
+
+ let eligible = if node_item.is_final() {
+ // Non-specializable items are always projectable.
+ true
+ } else {
+ // Only reveal a specializable default if we're past type-checking
+ // and the obligation is monomorphic, otherwise passes such as
+ // transmute checking and polymorphic MIR optimizations could
+ // get a result which isn't correct for all monomorphizations.
+ if param_env.reveal() == Reveal::All {
+ let poly_trait_ref = infcx.resolve_vars_if_possible(goal_trait_ref);
+ !poly_trait_ref.still_further_specializable()
} else {
- // Only reveal a specializable default if we're past type-checking
- // and the obligation is monomorphic, otherwise passes such as
- // transmute checking and polymorphic MIR optimizations could
- // get a result which isn't correct for all monomorphizations.
- if param_env.reveal() == Reveal::All {
- let poly_trait_ref = self.infcx.resolve_vars_if_possible(goal_trait_ref);
- !poly_trait_ref.still_further_specializable()
- } else {
- debug!(?node_item.item.def_id, "not eligible due to default");
- false
- }
- };
+ debug!(?node_item.item.def_id, "not eligible due to default");
+ false
+ }
+ };
- if eligible { Some(node_item) } else { None }
- }
+ if eligible { Some(node_item) } else { None }
}
use std::iter;
-use super::infcx_ext::InferCtxtExt;
-use super::{
- fixme_instantiate_canonical_query_response, CanonicalGoal, CanonicalResponse, Certainty,
- EvalCtxt, Goal, QueryResult,
-};
+use super::assembly::{self, AssemblyCtxt};
+use super::{CanonicalGoal, EvalCtxt, Goal, QueryResult};
use rustc_hir::def_id::DefId;
-use rustc_infer::infer::canonical::{CanonicalVarValues, OriginalQueryValues};
-use rustc_infer::infer::TyCtxtInferExt;
-use rustc_infer::infer::{InferCtxt, InferOk};
+use rustc_infer::infer::InferOk;
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::ObligationCause;
-use rustc_middle::ty;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_middle::ty::TraitPredicate;
+use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP;
-/// A candidate is a possible way to prove a goal.
-///
-/// It consists of both the `source`, which describes how that goal
-/// would be proven, and the `result` when using the given `source`.
-///
-/// For the list of possible candidates, please look at the documentation
-/// of [CandidateSource].
-#[derive(Debug, Clone)]
-pub(super) struct Candidate<'tcx> {
- source: CandidateSource,
- result: CanonicalResponse<'tcx>,
-}
-
#[allow(dead_code)] // FIXME: implement and use all variants.
#[derive(Debug, Clone, Copy)]
pub(super) enum CandidateSource {
AutoImpl,
}
-struct AssemblyCtxt<'a, 'tcx> {
- cx: &'a mut EvalCtxt<'tcx>,
- infcx: &'a InferCtxt<'tcx>,
- var_values: CanonicalVarValues<'tcx>,
- candidates: Vec<Candidate<'tcx>>,
+type Candidate<'tcx> = assembly::Candidate<'tcx, TraitPredicate<'tcx>>;
+
+impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
+ type CandidateSource = CandidateSource;
+
+ fn self_ty(self) -> Ty<'tcx> {
+ self.self_ty()
+ }
+
+ fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
+ self.with_self_ty(tcx, self_ty)
+ }
+
+ fn trait_def_id(self, _: TyCtxt<'tcx>) -> DefId {
+ self.def_id()
+ }
+
+ fn consider_impl_candidate(
+ acx: &mut AssemblyCtxt<'_, 'tcx, Self>,
+ goal: Goal<'tcx, TraitPredicate<'tcx>>,
+ impl_def_id: DefId,
+ ) {
+ let impl_trait_ref = acx.cx.tcx.bound_impl_trait_ref(impl_def_id).unwrap();
+ let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
+ if iter::zip(goal.predicate.trait_ref.substs, impl_trait_ref.skip_binder().substs)
+ .any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
+ {
+ return;
+ }
+
+ acx.infcx.probe(|_| {
+ let impl_substs = acx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
+ let impl_trait_ref = impl_trait_ref.subst(acx.cx.tcx, impl_substs);
+
+ let Ok(InferOk { obligations, .. }) = acx
+ .infcx
+ .at(&ObligationCause::dummy(), goal.param_env)
+ .define_opaque_types(false)
+ .eq(goal.predicate.trait_ref, impl_trait_ref)
+ .map_err(|e| debug!("failed to equate trait refs: {e:?}"))
+ else {
+ return
+ };
+
+ let nested_goals = obligations.into_iter().map(|o| o.into()).collect();
+
+ let Ok(certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
+ acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
+ })
+ }
}
impl<'tcx> EvalCtxt<'tcx> {
&mut self,
goal: CanonicalGoal<'tcx, TraitPredicate<'tcx>>,
) -> QueryResult<'tcx> {
- let candidates = self.assemble_and_evaluate_trait_candidates(goal);
+ let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
self.merge_trait_candidates_discard_reservation_impls(candidates)
}
- pub(super) fn assemble_and_evaluate_trait_candidates(
- &mut self,
- goal: CanonicalGoal<'tcx, TraitPredicate<'tcx>>,
- ) -> Vec<Candidate<'tcx>> {
- let (ref infcx, goal, var_values) =
- self.tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &goal);
- let mut acx = AssemblyCtxt { cx: self, infcx, var_values, candidates: Vec::new() };
-
- acx.assemble_candidates_after_normalizing_self_ty(goal);
- acx.assemble_impl_candidates(goal);
-
- // FIXME: Remaining candidates
- acx.candidates
- }
-
#[instrument(level = "debug", skip(self), ret)]
pub(super) fn merge_trait_candidates_discard_reservation_impls(
&mut self,
candidate
}
}
-
-impl<'tcx> AssemblyCtxt<'_, 'tcx> {
- /// Adds a new candidate using the current state of the inference context.
- ///
- /// This does require each assembly method to correctly use `probe` to not taint
- /// the results of other candidates.
- fn try_insert_candidate(&mut self, source: CandidateSource, certainty: Certainty) {
- match self.infcx.make_canonical_response(self.var_values.clone(), certainty) {
- Ok(result) => self.candidates.push(Candidate { source, result }),
- Err(NoSolution) => debug!(?source, ?certainty, "failed leakcheck"),
- }
- }
-
- /// If the self type of a trait goal is a projection, computing the relevant candidates is difficult.
- ///
- /// To deal with this, we first try to normalize the self type and add the candidates for the normalized
- /// self type to the list of candidates in case that succeeds. Note that we can't just eagerly return in
- /// this case as projections as self types add `
- fn assemble_candidates_after_normalizing_self_ty(
- &mut self,
- goal: Goal<'tcx, TraitPredicate<'tcx>>,
- ) {
- let tcx = self.cx.tcx;
- // FIXME: We also have to normalize opaque types, not sure where to best fit that in.
- let &ty::Alias(ty::Projection, projection_ty) = goal.predicate.self_ty().kind() else {
- return
- };
- self.infcx.probe(|_| {
- let normalized_ty = self.infcx.next_ty_infer();
- let normalizes_to_goal = goal.with(
- tcx,
- ty::Binder::dummy(ty::ProjectionPredicate {
- projection_ty,
- term: normalized_ty.into(),
- }),
- );
- let normalization_certainty =
- match self.cx.evaluate_goal(&self.infcx, normalizes_to_goal) {
- Ok((_, certainty)) => certainty,
- Err(NoSolution) => return,
- };
-
- // NOTE: Alternatively we could call `evaluate_goal` here and only have a `Normalized` candidate.
- // This doesn't work as long as we use `CandidateSource` in both winnowing and to resolve associated items.
- let goal = goal.with(tcx, goal.predicate.with_self_type(tcx, normalized_ty));
- let mut orig_values = OriginalQueryValues::default();
- let goal = self.infcx.canonicalize_query(goal, &mut orig_values);
- let normalized_candidates = self.cx.assemble_and_evaluate_trait_candidates(goal);
-
- // Map each candidate from being canonical wrt the current inference context to being
- // canonical wrt the caller.
- for Candidate { source, result } in normalized_candidates {
- self.infcx.probe(|_| {
- let candidate_certainty = fixme_instantiate_canonical_query_response(
- self.infcx,
- &orig_values,
- result,
- );
-
- // FIXME: This is a bit scary if the `normalizes_to_goal` overflows.
- //
- // If we have an ambiguous candidate it hides that normalization
- // caused an overflow which may cause issues.
- self.try_insert_candidate(
- source,
- normalization_certainty.unify_and(candidate_certainty),
- )
- })
- }
- })
- }
-
- fn assemble_impl_candidates(&mut self, goal: Goal<'tcx, TraitPredicate<'tcx>>) {
- self.cx.tcx.for_each_relevant_impl(
- goal.predicate.def_id(),
- goal.predicate.self_ty(),
- |impl_def_id| self.consider_impl_candidate(goal, impl_def_id),
- );
- }
-
- fn consider_impl_candidate(
- &mut self,
- goal: Goal<'tcx, TraitPredicate<'tcx>>,
- impl_def_id: DefId,
- ) {
- let impl_trait_ref = self.cx.tcx.bound_impl_trait_ref(impl_def_id).unwrap();
- let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
- if iter::zip(goal.predicate.trait_ref.substs, impl_trait_ref.skip_binder().substs)
- .any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
- {
- return;
- }
-
- self.infcx.probe(|_| {
- let impl_substs = self.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
- let impl_trait_ref = impl_trait_ref.subst(self.cx.tcx, impl_substs);
-
- let Ok(InferOk { obligations, .. }) = self
- .infcx
- .at(&ObligationCause::dummy(), goal.param_env)
- .define_opaque_types(false)
- .eq(goal.predicate.trait_ref, impl_trait_ref)
- .map_err(|e| debug!("failed to equate trait refs: {e:?}"))
- else {
- return
- };
-
- let nested_goals = obligations.into_iter().map(|o| o.into()).collect();
-
- let Ok(certainty) = self.cx.evaluate_all(self.infcx, nested_goals) else { return };
- self.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
- })
- }
-}
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