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dedup assembly

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This commit is contained in:
lcnr 2022-12-19 07:01:38 +00:00
parent a213bb36c9
commit 750bf36c33
4 changed files with 270 additions and 301 deletions
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150
compiler/rustc_trait_selection/src/solve/assembly.rs Normal file
View File

@ -0,0 +1,150 @@
//! 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),
);
}
}

1
compiler/rustc_trait_selection/src/solve/mod.rs
View File

@ -30,6 +30,7 @@ use rustc_span::DUMMY_SP;
use self::infcx_ext::InferCtxtExt;
mod assembly;
mod cache;
mod fulfill;
mod infcx_ext;

208
compiler/rustc_trait_selection/src/solve/project_goals.rs
View File

@ -1,64 +1,40 @@
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>>,
@ -112,83 +88,27 @@ impl<'tcx> EvalCtxt<'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 };
@ -198,11 +118,11 @@ impl<'tcx> AssemblyCtxt<'_, 'tcx> {
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)
@ -213,9 +133,10 @@ impl<'tcx> AssemblyCtxt<'_, 'tcx> {
};
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(),
@ -247,7 +168,7 @@ impl<'tcx> AssemblyCtxt<'_, 'tcx> {
impl_trait_ref.substs,
);
let substs = translate_substs(
self.infcx,
acx.infcx,
goal.param_env,
impl_def_id,
impl_substs_with_gat,
@ -267,7 +188,7 @@ impl<'tcx> AssemblyCtxt<'_, 'tcx> {
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)
@ -278,47 +199,46 @@ impl<'tcx> AssemblyCtxt<'_, 'tcx> {
};
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
} 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
}
};
if eligible { Some(node_item) } else { None }
}
}
/// 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 {
debug!(?node_item.item.def_id, "not eligible due to default");
false
}
};
if eligible { Some(node_item) } else { None }
}

212
compiler/rustc_trait_selection/src/solve/trait_goals.rs
View File

@ -2,35 +2,17 @@
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 {
@ -67,11 +49,56 @@ 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> {
@ -79,25 +106,10 @@ 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,
@ -166,117 +178,3 @@ impl<'tcx> EvalCtxt<'tcx> {
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);
})
}
}