676 lines
26 KiB
Rust
676 lines
26 KiB
Rust
use crate::traits::{check_args_compatible, specialization_graph};
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use super::assembly::{self, structural_traits, Candidate};
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use super::EvalCtxt;
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use rustc_hir::def::DefKind;
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use rustc_hir::def_id::DefId;
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use rustc_hir::LangItem;
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use rustc_infer::traits::query::NoSolution;
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use rustc_infer::traits::specialization_graph::LeafDef;
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use rustc_infer::traits::Reveal;
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use rustc_middle::traits::solve::{
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CandidateSource, CanonicalResponse, Certainty, Goal, QueryResult,
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};
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use rustc_middle::traits::BuiltinImplSource;
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use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
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use rustc_middle::ty::ProjectionPredicate;
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use rustc_middle::ty::{self, Ty, TyCtxt};
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use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
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use rustc_span::{sym, ErrorGuaranteed, DUMMY_SP};
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mod inherent_projection;
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mod opaques;
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mod weak_types;
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impl<'tcx> EvalCtxt<'_, 'tcx> {
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#[instrument(level = "debug", skip(self), ret)]
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pub(super) fn compute_projection_goal(
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&mut self,
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goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
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) -> QueryResult<'tcx> {
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let def_id = goal.predicate.def_id();
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match self.tcx().def_kind(def_id) {
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DefKind::AssocTy | DefKind::AssocConst => {
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// To only compute normalization once for each projection we only
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// assemble normalization candidates if the expected term is an
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// unconstrained inference variable.
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//
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// Why: For better cache hits, since if we have an unconstrained RHS then
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// there are only as many cache keys as there are (canonicalized) alias
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// types in each normalizes-to goal. This also weakens inference in a
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// forwards-compatible way so we don't use the value of the RHS term to
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// affect candidate assembly for projections.
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//
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// E.g. for `<T as Trait>::Assoc == u32` we recursively compute the goal
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// `exists<U> <T as Trait>::Assoc == U` and then take the resulting type for
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// `U` and equate it with `u32`. This means that we don't need a separate
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// projection cache in the solver, since we're piggybacking off of regular
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// goal caching.
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if self.term_is_fully_unconstrained(goal) {
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match self.tcx().associated_item(def_id).container {
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ty::AssocItemContainer::TraitContainer => {
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let candidates = self.assemble_and_evaluate_candidates(goal);
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self.merge_candidates(candidates)
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}
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ty::AssocItemContainer::ImplContainer => {
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self.normalize_inherent_associated_type(goal)
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}
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}
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} else {
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self.set_normalizes_to_hack_goal(goal);
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self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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}
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}
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DefKind::AnonConst => self.normalize_anon_const(goal),
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DefKind::OpaqueTy => self.normalize_opaque_type(goal),
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DefKind::TyAlias => self.normalize_weak_type(goal),
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kind => bug!("unknown DefKind {} in projection goal: {goal:#?}", kind.descr(def_id)),
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}
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}
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#[instrument(level = "debug", skip(self), ret)]
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fn normalize_anon_const(
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&mut self,
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goal: Goal<'tcx, ty::ProjectionPredicate<'tcx>>,
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) -> QueryResult<'tcx> {
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if let Some(normalized_const) = self.try_const_eval_resolve(
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goal.param_env,
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ty::UnevaluatedConst::new(
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goal.predicate.projection_ty.def_id,
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goal.predicate.projection_ty.args,
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),
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self.tcx()
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.type_of(goal.predicate.projection_ty.def_id)
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.no_bound_vars()
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.expect("const ty should not rely on other generics"),
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) {
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self.eq(goal.param_env, normalized_const, goal.predicate.term.ct().unwrap())?;
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self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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} else {
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self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
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}
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}
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}
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impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
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fn self_ty(self) -> Ty<'tcx> {
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self.self_ty()
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}
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fn trait_ref(self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
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self.projection_ty.trait_ref(tcx)
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}
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fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
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self.with_self_ty(tcx, self_ty)
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}
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fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId {
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self.trait_def_id(tcx)
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}
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fn probe_and_match_goal_against_assumption(
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ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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assumption: ty::Clause<'tcx>,
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then: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> QueryResult<'tcx>,
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) -> QueryResult<'tcx> {
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if let Some(projection_pred) = assumption.as_projection_clause() {
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if projection_pred.projection_def_id() == goal.predicate.def_id() {
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let tcx = ecx.tcx();
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ecx.probe_misc_candidate("assumption").enter(|ecx| {
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let assumption_projection_pred =
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ecx.instantiate_binder_with_infer(projection_pred);
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ecx.eq(
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goal.param_env,
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goal.predicate.projection_ty,
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assumption_projection_pred.projection_ty,
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)?;
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ecx.eq(goal.param_env, goal.predicate.term, assumption_projection_pred.term)
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.expect("expected goal term to be fully unconstrained");
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// Add GAT where clauses from the trait's definition
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ecx.add_goals(
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tcx.predicates_of(goal.predicate.def_id())
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.instantiate_own(tcx, goal.predicate.projection_ty.args)
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.map(|(pred, _)| goal.with(tcx, pred)),
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);
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then(ecx)
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})
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} else {
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Err(NoSolution)
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}
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} else {
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Err(NoSolution)
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}
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}
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fn consider_impl_candidate(
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ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
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impl_def_id: DefId,
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) -> Result<Candidate<'tcx>, NoSolution> {
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let tcx = ecx.tcx();
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let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
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let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
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let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
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if !drcx.args_may_unify(goal_trait_ref.args, impl_trait_ref.skip_binder().args) {
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return Err(NoSolution);
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}
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ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
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let impl_args = ecx.fresh_args_for_item(impl_def_id);
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let impl_trait_ref = impl_trait_ref.instantiate(tcx, impl_args);
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ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;
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let where_clause_bounds = tcx
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.predicates_of(impl_def_id)
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.instantiate(tcx, impl_args)
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.predicates
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.into_iter()
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.map(|pred| goal.with(tcx, pred));
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ecx.add_goals(where_clause_bounds);
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// Add GAT where clauses from the trait's definition
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ecx.add_goals(
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tcx.predicates_of(goal.predicate.def_id())
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.instantiate_own(tcx, goal.predicate.projection_ty.args)
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.map(|(pred, _)| goal.with(tcx, pred)),
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);
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// In case the associated item is hidden due to specialization, we have to
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// return ambiguity this would otherwise be incomplete, resulting in
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// unsoundness during coherence (#105782).
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let Some(assoc_def) = fetch_eligible_assoc_item_def(
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ecx,
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goal.param_env,
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goal_trait_ref,
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goal.predicate.def_id(),
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impl_def_id,
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)?
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else {
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return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
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};
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let error_response = |ecx: &mut EvalCtxt<'_, 'tcx>, reason| {
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let guar = tcx.sess.delay_span_bug(tcx.def_span(assoc_def.item.def_id), reason);
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let error_term = match assoc_def.item.kind {
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ty::AssocKind::Const => ty::Const::new_error(
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tcx,
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guar,
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tcx.type_of(goal.predicate.def_id())
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.instantiate(tcx, goal.predicate.projection_ty.args),
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)
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.into(),
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ty::AssocKind::Type => Ty::new_error(tcx, guar).into(),
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ty::AssocKind::Fn => unreachable!(),
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};
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ecx.eq(goal.param_env, goal.predicate.term, error_term)
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.expect("expected goal term to be fully unconstrained");
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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};
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if !assoc_def.item.defaultness(tcx).has_value() {
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return error_response(ecx, "missing value for assoc item in impl");
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}
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// Getting the right args here is complex, e.g. given:
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// - a goal `<Vec<u32> as Trait<i32>>::Assoc<u64>`
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// - the applicable impl `impl<T> Trait<i32> for Vec<T>`
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// - and the impl which defines `Assoc` being `impl<T, U> Trait<U> for Vec<T>`
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//
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// We first rebase the goal args onto the impl, going from `[Vec<u32>, i32, u64]`
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// to `[u32, u64]`.
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//
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// And then map these args to the args of the defining impl of `Assoc`, going
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// from `[u32, u64]` to `[u32, i32, u64]`.
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let impl_args_with_gat = goal.predicate.projection_ty.args.rebase_onto(
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tcx,
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goal_trait_ref.def_id,
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impl_args,
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);
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let args = ecx.translate_args(
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goal.param_env,
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impl_def_id,
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impl_args_with_gat,
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assoc_def.defining_node,
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);
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if !check_args_compatible(tcx, assoc_def.item, args) {
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return error_response(
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ecx,
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"associated item has mismatched generic item arguments",
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);
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}
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// Finally we construct the actual value of the associated type.
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let term = match assoc_def.item.kind {
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ty::AssocKind::Type => tcx.type_of(assoc_def.item.def_id).map_bound(|ty| ty.into()),
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ty::AssocKind::Const => {
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if tcx.features().associated_const_equality {
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bug!("associated const projection is not supported yet")
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} else {
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ty::EarlyBinder::bind(
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ty::Const::new_error_with_message(
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tcx,
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tcx.type_of(assoc_def.item.def_id).instantiate_identity(),
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DUMMY_SP,
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"associated const projection is not supported yet",
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)
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.into(),
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)
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}
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}
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ty::AssocKind::Fn => unreachable!("we should never project to a fn"),
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};
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ecx.eq(goal.param_env, goal.predicate.term, term.instantiate(tcx, args))
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.expect("expected goal term to be fully unconstrained");
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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})
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}
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/// Fail to normalize if the predicate contains an error, alternatively, we could normalize to `ty::Error`
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/// and succeed. Can experiment with this to figure out what results in better error messages.
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fn consider_error_guaranteed_candidate(
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_ecx: &mut EvalCtxt<'_, 'tcx>,
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_guar: ErrorGuaranteed,
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) -> QueryResult<'tcx> {
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Err(NoSolution)
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}
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fn consider_auto_trait_candidate(
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ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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ecx.tcx().sess.delay_span_bug(
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ecx.tcx().def_span(goal.predicate.def_id()),
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"associated types not allowed on auto traits",
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);
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Err(NoSolution)
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}
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fn consider_trait_alias_candidate(
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_ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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bug!("trait aliases do not have associated types: {:?}", goal);
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}
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fn consider_builtin_sized_candidate(
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_ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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bug!("`Sized` does not have an associated type: {:?}", goal);
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}
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fn consider_builtin_copy_clone_candidate(
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_ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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bug!("`Copy`/`Clone` does not have an associated type: {:?}", goal);
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}
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fn consider_builtin_pointer_like_candidate(
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_ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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bug!("`PointerLike` does not have an associated type: {:?}", goal);
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}
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fn consider_builtin_fn_ptr_trait_candidate(
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_ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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bug!("`FnPtr` does not have an associated type: {:?}", goal);
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}
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fn consider_builtin_fn_trait_candidates(
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ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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goal_kind: ty::ClosureKind,
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) -> QueryResult<'tcx> {
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let tcx = ecx.tcx();
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let tupled_inputs_and_output =
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match structural_traits::extract_tupled_inputs_and_output_from_callable(
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tcx,
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goal.predicate.self_ty(),
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goal_kind,
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)? {
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Some(tupled_inputs_and_output) => tupled_inputs_and_output,
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None => {
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return ecx
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.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
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}
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};
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let output_is_sized_pred = tupled_inputs_and_output.map_bound(|(_, output)| {
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ty::TraitRef::from_lang_item(tcx, LangItem::Sized, DUMMY_SP, [output])
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});
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let pred = tupled_inputs_and_output
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.map_bound(|(inputs, output)| ty::ProjectionPredicate {
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projection_ty: ty::AliasTy::new(
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tcx,
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goal.predicate.def_id(),
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[goal.predicate.self_ty(), inputs],
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),
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term: output.into(),
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})
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.to_predicate(tcx);
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// A built-in `Fn` impl only holds if the output is sized.
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// (FIXME: technically we only need to check this if the type is a fn ptr...)
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Self::consider_implied_clause(ecx, goal, pred, [goal.with(tcx, output_is_sized_pred)])
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}
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fn consider_builtin_tuple_candidate(
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_ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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bug!("`Tuple` does not have an associated type: {:?}", goal);
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}
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fn consider_builtin_pointee_candidate(
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ecx: &mut EvalCtxt<'_, 'tcx>,
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goal: Goal<'tcx, Self>,
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) -> QueryResult<'tcx> {
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let tcx = ecx.tcx();
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ecx.probe_misc_candidate("builtin pointee").enter(|ecx| {
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let metadata_ty = match goal.predicate.self_ty().kind() {
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ty::Bool
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| ty::Char
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| ty::Int(..)
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| ty::Uint(..)
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| ty::Float(..)
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| ty::Array(..)
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| ty::RawPtr(..)
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| ty::Ref(..)
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| ty::FnDef(..)
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| ty::FnPtr(..)
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| ty::Closure(..)
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| ty::Infer(ty::IntVar(..) | ty::FloatVar(..))
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| ty::Coroutine(..)
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| ty::CoroutineWitness(..)
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| ty::Never
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| ty::Foreign(..) => tcx.types.unit,
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ty::Error(e) => Ty::new_error(tcx, *e),
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ty::Str | ty::Slice(_) => tcx.types.usize,
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ty::Dynamic(_, _, _) => {
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let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
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tcx.type_of(dyn_metadata)
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.instantiate(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())])
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}
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ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
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// FIXME(ptr_metadata): It would also be possible to return a `Ok(Ambig)` with no constraints.
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let sized_predicate = ty::TraitRef::from_lang_item(
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tcx,
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LangItem::Sized,
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DUMMY_SP,
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[ty::GenericArg::from(goal.predicate.self_ty())],
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);
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ecx.add_goal(goal.with(tcx, sized_predicate));
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tcx.types.unit
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}
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ty::Adt(def, args) if def.is_struct() => match def.non_enum_variant().tail_opt() {
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None => tcx.types.unit,
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Some(field_def) => {
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let self_ty = field_def.ty(tcx, args);
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ecx.add_goal(goal.with(tcx, goal.predicate.with_self_ty(tcx, self_ty)));
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return ecx
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.evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
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}
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},
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ty::Adt(_, _) => tcx.types.unit,
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ty::Tuple(elements) => match elements.last() {
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None => tcx.types.unit,
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Some(&self_ty) => {
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ecx.add_goal(goal.with(tcx, goal.predicate.with_self_ty(tcx, self_ty)));
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return ecx
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.evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
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}
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},
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ty::Infer(
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|
ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_),
|
|
)
|
|
| ty::Bound(..) => bug!(
|
|
"unexpected self ty `{:?}` when normalizing `<T as Pointee>::Metadata`",
|
|
goal.predicate.self_ty()
|
|
),
|
|
};
|
|
|
|
ecx.eq(goal.param_env, goal.predicate.term, metadata_ty.into())
|
|
.expect("expected goal term to be fully unconstrained");
|
|
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
|
|
})
|
|
}
|
|
|
|
fn consider_builtin_future_candidate(
|
|
ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
let self_ty = goal.predicate.self_ty();
|
|
let ty::Coroutine(def_id, args, _) = *self_ty.kind() else {
|
|
return Err(NoSolution);
|
|
};
|
|
|
|
// Coroutines are not futures unless they come from `async` desugaring
|
|
let tcx = ecx.tcx();
|
|
if !tcx.coroutine_is_async(def_id) {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
let term = args.as_coroutine().return_ty().into();
|
|
|
|
Self::consider_implied_clause(
|
|
ecx,
|
|
goal,
|
|
ty::ProjectionPredicate {
|
|
projection_ty: ty::AliasTy::new(ecx.tcx(), goal.predicate.def_id(), [self_ty]),
|
|
term,
|
|
}
|
|
.to_predicate(tcx),
|
|
// Technically, we need to check that the future type is Sized,
|
|
// but that's already proven by the coroutine being WF.
|
|
[],
|
|
)
|
|
}
|
|
|
|
fn consider_builtin_iterator_candidate(
|
|
ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
let self_ty = goal.predicate.self_ty();
|
|
let ty::Coroutine(def_id, args, _) = *self_ty.kind() else {
|
|
return Err(NoSolution);
|
|
};
|
|
|
|
// Coroutines are not Iterators unless they come from `gen` desugaring
|
|
let tcx = ecx.tcx();
|
|
if !tcx.coroutine_is_gen(def_id) {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
let term = args.as_coroutine().yield_ty().into();
|
|
|
|
Self::consider_implied_clause(
|
|
ecx,
|
|
goal,
|
|
ty::ProjectionPredicate {
|
|
projection_ty: ty::AliasTy::new(ecx.tcx(), goal.predicate.def_id(), [self_ty]),
|
|
term,
|
|
}
|
|
.to_predicate(tcx),
|
|
// Technically, we need to check that the iterator type is Sized,
|
|
// but that's already proven by the generator being WF.
|
|
[],
|
|
)
|
|
}
|
|
|
|
fn consider_builtin_coroutine_candidate(
|
|
ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
let self_ty = goal.predicate.self_ty();
|
|
let ty::Coroutine(def_id, args, _) = *self_ty.kind() else {
|
|
return Err(NoSolution);
|
|
};
|
|
|
|
// `async`-desugared coroutines do not implement the coroutine trait
|
|
let tcx = ecx.tcx();
|
|
if !tcx.is_general_coroutine(def_id) {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
let coroutine = args.as_coroutine();
|
|
|
|
let name = tcx.associated_item(goal.predicate.def_id()).name;
|
|
let term = if name == sym::Return {
|
|
coroutine.return_ty().into()
|
|
} else if name == sym::Yield {
|
|
coroutine.yield_ty().into()
|
|
} else {
|
|
bug!("unexpected associated item `<{self_ty} as Coroutine>::{name}`")
|
|
};
|
|
|
|
Self::consider_implied_clause(
|
|
ecx,
|
|
goal,
|
|
ty::ProjectionPredicate {
|
|
projection_ty: ty::AliasTy::new(
|
|
ecx.tcx(),
|
|
goal.predicate.def_id(),
|
|
[self_ty, coroutine.resume_ty()],
|
|
),
|
|
term,
|
|
}
|
|
.to_predicate(tcx),
|
|
// Technically, we need to check that the coroutine type is Sized,
|
|
// but that's already proven by the coroutine being WF.
|
|
[],
|
|
)
|
|
}
|
|
|
|
fn consider_unsize_to_dyn_candidate(
|
|
_ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
bug!("`Unsize` does not have an associated type: {:?}", goal)
|
|
}
|
|
|
|
fn consider_structural_builtin_unsize_candidates(
|
|
_ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> Vec<(CanonicalResponse<'tcx>, BuiltinImplSource)> {
|
|
bug!("`Unsize` does not have an associated type: {:?}", goal);
|
|
}
|
|
|
|
fn consider_builtin_discriminant_kind_candidate(
|
|
ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
let self_ty = goal.predicate.self_ty();
|
|
let discriminant_ty = match *self_ty.kind() {
|
|
ty::Bool
|
|
| ty::Char
|
|
| ty::Int(..)
|
|
| ty::Uint(..)
|
|
| ty::Float(..)
|
|
| ty::Array(..)
|
|
| ty::RawPtr(..)
|
|
| ty::Ref(..)
|
|
| ty::FnDef(..)
|
|
| ty::FnPtr(..)
|
|
| ty::Closure(..)
|
|
| ty::Infer(ty::IntVar(..) | ty::FloatVar(..))
|
|
| ty::Coroutine(..)
|
|
| ty::CoroutineWitness(..)
|
|
| ty::Never
|
|
| ty::Foreign(..)
|
|
| ty::Adt(_, _)
|
|
| ty::Str
|
|
| ty::Slice(_)
|
|
| ty::Dynamic(_, _, _)
|
|
| ty::Tuple(_)
|
|
| ty::Error(_) => self_ty.discriminant_ty(ecx.tcx()),
|
|
|
|
// We do not call `Ty::discriminant_ty` on alias, param, or placeholder
|
|
// types, which return `<self_ty as DiscriminantKind>::Discriminant`
|
|
// (or ICE in the case of placeholders). Projecting a type to itself
|
|
// is never really productive.
|
|
ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
|
|
| ty::Bound(..) => bug!(
|
|
"unexpected self ty `{:?}` when normalizing `<T as DiscriminantKind>::Discriminant`",
|
|
goal.predicate.self_ty()
|
|
),
|
|
};
|
|
|
|
ecx.probe_misc_candidate("builtin discriminant kind").enter(|ecx| {
|
|
ecx.eq(goal.param_env, goal.predicate.term, discriminant_ty.into())
|
|
.expect("expected goal term to be fully unconstrained");
|
|
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
|
|
})
|
|
}
|
|
|
|
fn consider_builtin_destruct_candidate(
|
|
_ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
bug!("`Destruct` does not have an associated type: {:?}", goal);
|
|
}
|
|
|
|
fn consider_builtin_transmute_candidate(
|
|
_ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
bug!("`BikeshedIntrinsicFrom` does not have an associated type: {:?}", goal)
|
|
}
|
|
}
|
|
|
|
/// 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(ecx, param_env), ret)]
|
|
fn fetch_eligible_assoc_item_def<'tcx>(
|
|
ecx: &EvalCtxt<'_, 'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
goal_trait_ref: ty::TraitRef<'tcx>,
|
|
trait_assoc_def_id: DefId,
|
|
impl_def_id: DefId,
|
|
) -> Result<Option<LeafDef>, NoSolution> {
|
|
let node_item = specialization_graph::assoc_def(ecx.tcx(), impl_def_id, trait_assoc_def_id)
|
|
.map_err(|ErrorGuaranteed { .. }| NoSolution)?;
|
|
|
|
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 = ecx.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 { Ok(Some(node_item)) } else { Ok(None) }
|
|
}
|