753 lines
30 KiB
Rust
753 lines
30 KiB
Rust
//! Dealing with trait goals, i.e. `T: Trait<'a, U>`.
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use super::assembly::{self, structural_traits};
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use super::{EvalCtxt, SolverMode};
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use rustc_hir::def_id::DefId;
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use rustc_hir::{LangItem, Movability};
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use rustc_infer::traits::query::NoSolution;
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use rustc_infer::traits::util::supertraits;
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use rustc_middle::traits::solve::inspect::CandidateKind;
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use rustc_middle::traits::solve::{CanonicalResponse, Certainty, Goal, QueryResult};
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use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, TreatProjections};
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use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
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use rustc_middle::ty::{TraitPredicate, TypeVisitableExt};
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use rustc_span::DUMMY_SP;
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impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'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, _: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
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self.trait_ref
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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, _: TyCtxt<'tcx>) -> DefId {
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self.def_id()
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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, TraitPredicate<'tcx>>,
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impl_def_id: DefId,
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) -> QueryResult<'tcx> {
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let tcx = ecx.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.substs_refs_may_unify(
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goal.predicate.trait_ref.substs,
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impl_trait_ref.skip_binder().substs,
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) {
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return Err(NoSolution);
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}
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let impl_polarity = tcx.impl_polarity(impl_def_id);
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// An upper bound of the certainty of this goal, used to lower the certainty
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// of reservation impl to ambiguous during coherence.
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let maximal_certainty = match impl_polarity {
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ty::ImplPolarity::Positive | ty::ImplPolarity::Negative => {
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match impl_polarity == goal.predicate.polarity {
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true => Certainty::Yes,
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false => return Err(NoSolution),
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}
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}
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ty::ImplPolarity::Reservation => match ecx.solver_mode() {
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SolverMode::Normal => return Err(NoSolution),
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SolverMode::Coherence => Certainty::AMBIGUOUS,
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},
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};
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ecx.probe(
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|ecx| {
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let impl_substs = ecx.fresh_substs_for_item(impl_def_id);
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let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
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ecx.eq(goal.param_env, goal.predicate.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_substs)
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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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ecx.evaluate_added_goals_and_make_canonical_response(maximal_certainty)
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},
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|r| CandidateKind::Candidate { name: "impl".into(), result: *r },
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)
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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::Binder<'tcx, ty::ClauseKind<'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(trait_clause) = assumption.as_trait_clause() {
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if trait_clause.def_id() == goal.predicate.def_id()
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&& trait_clause.polarity() == goal.predicate.polarity
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{
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// FIXME: Constness
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ecx.probe(
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|ecx| {
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let assumption_trait_pred = ecx.instantiate_binder_with_infer(trait_clause);
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ecx.eq(
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goal.param_env,
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goal.predicate.trait_ref,
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assumption_trait_pred.trait_ref,
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)?;
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then(ecx)
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},
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|r| CandidateKind::Candidate { name: "assumption".into(), result: *r },
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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_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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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if let Some(result) = ecx.disqualify_auto_trait_candidate_due_to_possible_impl(goal) {
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return result;
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}
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ecx.probe_and_evaluate_goal_for_constituent_tys(
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goal,
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structural_traits::instantiate_constituent_tys_for_auto_trait,
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)
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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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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let tcx = ecx.tcx();
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ecx.probe(
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|ecx| {
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let nested_obligations = tcx
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.predicates_of(goal.predicate.def_id())
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.instantiate(tcx, goal.predicate.trait_ref.substs);
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ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p)));
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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},
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|r| CandidateKind::Candidate { name: "trait alias".into(), result: *r },
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)
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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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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ecx.probe_and_evaluate_goal_for_constituent_tys(
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goal,
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structural_traits::instantiate_constituent_tys_for_sized_trait,
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)
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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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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ecx.probe_and_evaluate_goal_for_constituent_tys(
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goal,
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structural_traits::instantiate_constituent_tys_for_copy_clone_trait,
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)
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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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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// The regions of a type don't affect the size of the type
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let tcx = ecx.tcx();
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// We should erase regions from both the param-env and type, since both
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// may have infer regions. Specifically, after canonicalizing and instantiating,
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// early bound regions turn into region vars in both the new and old solver.
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let key = tcx.erase_regions(goal.param_env.and(goal.predicate.self_ty()));
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// But if there are inference variables, we have to wait until it's resolved.
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if key.has_non_region_infer() {
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return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
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}
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if let Ok(layout) = tcx.layout_of(key)
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&& layout.layout.is_pointer_like(&tcx.data_layout)
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{
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// FIXME: We could make this faster by making a no-constraints response
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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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_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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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if let ty::FnPtr(..) = goal.predicate.self_ty().kind() {
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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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_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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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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(a) => a,
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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, _)| {
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ty::TraitRef::new(tcx, goal.predicate.def_id(), [goal.predicate.self_ty(), inputs])
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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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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if let ty::Tuple(..) = goal.predicate.self_ty().kind() {
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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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_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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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}
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fn consider_builtin_future_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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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let ty::Generator(def_id, _, _) = *goal.predicate.self_ty().kind() else {
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return Err(NoSolution);
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};
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// Generators are not futures unless they come from `async` desugaring
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let tcx = ecx.tcx();
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if !tcx.generator_is_async(def_id) {
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return Err(NoSolution);
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}
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// Async generator unconditionally implement `Future`
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// Technically, we need to check that the future output type is Sized,
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// but that's already proven by the generator being WF.
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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}
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fn consider_builtin_generator_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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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let self_ty = goal.predicate.self_ty();
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let ty::Generator(def_id, substs, _) = *self_ty.kind() else {
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return Err(NoSolution);
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};
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// `async`-desugared generators do not implement the generator trait
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let tcx = ecx.tcx();
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if tcx.generator_is_async(def_id) {
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return Err(NoSolution);
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}
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let generator = substs.as_generator();
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Self::consider_implied_clause(
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ecx,
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goal,
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ty::TraitRef::new(tcx, goal.predicate.def_id(), [self_ty, generator.resume_ty()])
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.to_predicate(tcx),
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// Technically, we need to check that the generator types are Sized,
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// but that's already proven by the generator being WF.
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[],
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)
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}
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fn consider_builtin_unsize_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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if goal.predicate.polarity != ty::ImplPolarity::Positive {
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return Err(NoSolution);
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}
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let tcx = ecx.tcx();
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let a_ty = goal.predicate.self_ty();
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let b_ty = goal.predicate.trait_ref.substs.type_at(1);
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if b_ty.is_ty_var() {
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return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
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}
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ecx.probe(
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|ecx| {
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match (a_ty.kind(), b_ty.kind()) {
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// Trait upcasting, or `dyn Trait + Auto + 'a` -> `dyn Trait + 'b`
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(&ty::Dynamic(_, _, ty::Dyn), &ty::Dynamic(_, _, ty::Dyn)) => {
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// Dyn upcasting is handled separately, since due to upcasting,
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// when there are two supertraits that differ by substs, we
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// may return more than one query response.
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Err(NoSolution)
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}
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// `T` -> `dyn Trait` unsizing
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(_, &ty::Dynamic(data, region, ty::Dyn)) => {
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// Can only unsize to an object-safe type
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if data
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.principal_def_id()
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.is_some_and(|def_id| !tcx.check_is_object_safe(def_id))
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{
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return Err(NoSolution);
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}
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let Some(sized_def_id) = tcx.lang_items().sized_trait() else {
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return Err(NoSolution);
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};
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// Check that the type implements all of the predicates of the def-id.
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// (i.e. the principal, all of the associated types match, and any auto traits)
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ecx.add_goals(
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data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))),
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);
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// The type must be Sized to be unsized.
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ecx.add_goal(goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty])));
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// The type must outlive the lifetime of the `dyn` we're unsizing into.
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ecx.add_goal(
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goal.with(tcx, ty::Binder::dummy(ty::OutlivesPredicate(a_ty, region))),
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);
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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}
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// `[T; n]` -> `[T]` unsizing
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(&ty::Array(a_elem_ty, ..), &ty::Slice(b_elem_ty)) => {
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// We just require that the element type stays the same
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ecx.eq(goal.param_env, a_elem_ty, b_elem_ty)?;
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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}
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// Struct unsizing `Struct<T>` -> `Struct<U>` where `T: Unsize<U>`
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(&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
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if a_def.is_struct() && a_def.did() == b_def.did() =>
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{
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let unsizing_params = tcx.unsizing_params_for_adt(a_def.did());
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// We must be unsizing some type parameters. This also implies
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// that the struct has a tail field.
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if unsizing_params.is_empty() {
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return Err(NoSolution);
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}
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let tail_field = a_def
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.non_enum_variant()
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.fields
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.raw
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.last()
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.expect("expected unsized ADT to have a tail field");
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let tail_field_ty = tcx.type_of(tail_field.did);
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let a_tail_ty = tail_field_ty.subst(tcx, a_substs);
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let b_tail_ty = tail_field_ty.subst(tcx, b_substs);
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// Substitute just the unsizing params from B into A. The type after
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// this substitution must be equal to B. This is so we don't unsize
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// unrelated type parameters.
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let new_a_substs =
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tcx.mk_substs_from_iter(a_substs.iter().enumerate().map(|(i, a)| {
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if unsizing_params.contains(i as u32) { b_substs[i] } else { a }
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}));
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let unsized_a_ty = tcx.mk_adt(a_def, new_a_substs);
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// Finally, we require that `TailA: Unsize<TailB>` for the tail field
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// types.
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ecx.eq(goal.param_env, unsized_a_ty, b_ty)?;
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ecx.add_goal(goal.with(
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tcx,
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ty::TraitRef::new(tcx, goal.predicate.def_id(), [a_tail_ty, b_tail_ty]),
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));
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ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
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}
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// Tuple unsizing `(.., T)` -> `(.., U)` where `T: Unsize<U>`
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(&ty::Tuple(a_tys), &ty::Tuple(b_tys))
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if a_tys.len() == b_tys.len() && !a_tys.is_empty() =>
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{
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let (a_last_ty, a_rest_tys) = a_tys.split_last().unwrap();
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|
let b_last_ty = b_tys.last().unwrap();
|
|
|
|
// Substitute just the tail field of B., and require that they're equal.
|
|
let unsized_a_ty =
|
|
tcx.mk_tup_from_iter(a_rest_tys.iter().chain([b_last_ty]).copied());
|
|
ecx.eq(goal.param_env, unsized_a_ty, b_ty)?;
|
|
|
|
// Similar to ADTs, require that the rest of the fields are equal.
|
|
ecx.add_goal(goal.with(
|
|
tcx,
|
|
ty::TraitRef::new(
|
|
tcx,
|
|
goal.predicate.def_id(),
|
|
[*a_last_ty, *b_last_ty],
|
|
),
|
|
));
|
|
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
|
|
}
|
|
_ => Err(NoSolution),
|
|
}
|
|
},
|
|
|r| CandidateKind::Candidate { name: "builtin unsize".into(), result: *r },
|
|
)
|
|
}
|
|
|
|
fn consider_builtin_dyn_upcast_candidates(
|
|
ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> Vec<CanonicalResponse<'tcx>> {
|
|
if goal.predicate.polarity != ty::ImplPolarity::Positive {
|
|
return vec![];
|
|
}
|
|
|
|
let tcx = ecx.tcx();
|
|
|
|
let a_ty = goal.predicate.self_ty();
|
|
let b_ty = goal.predicate.trait_ref.substs.type_at(1);
|
|
let ty::Dynamic(a_data, a_region, ty::Dyn) = *a_ty.kind() else {
|
|
return vec![];
|
|
};
|
|
let ty::Dynamic(b_data, b_region, ty::Dyn) = *b_ty.kind() else {
|
|
return vec![];
|
|
};
|
|
|
|
// All of a's auto traits need to be in b's auto traits.
|
|
let auto_traits_compatible =
|
|
b_data.auto_traits().all(|b| a_data.auto_traits().any(|a| a == b));
|
|
if !auto_traits_compatible {
|
|
return vec![];
|
|
}
|
|
|
|
let mut unsize_dyn_to_principal = |principal: Option<ty::PolyExistentialTraitRef<'tcx>>| {
|
|
ecx.probe(
|
|
|ecx| -> Result<_, NoSolution> {
|
|
// Require that all of the trait predicates from A match B, except for
|
|
// the auto traits. We do this by constructing a new A type with B's
|
|
// auto traits, and equating these types.
|
|
let new_a_data = principal
|
|
.into_iter()
|
|
.map(|trait_ref| trait_ref.map_bound(ty::ExistentialPredicate::Trait))
|
|
.chain(a_data.iter().filter(|a| {
|
|
matches!(a.skip_binder(), ty::ExistentialPredicate::Projection(_))
|
|
}))
|
|
.chain(
|
|
b_data
|
|
.auto_traits()
|
|
.map(ty::ExistentialPredicate::AutoTrait)
|
|
.map(ty::Binder::dummy),
|
|
);
|
|
let new_a_data = tcx.mk_poly_existential_predicates_from_iter(new_a_data);
|
|
let new_a_ty = tcx.mk_dynamic(new_a_data, b_region, ty::Dyn);
|
|
|
|
// We also require that A's lifetime outlives B's lifetime.
|
|
ecx.eq(goal.param_env, new_a_ty, b_ty)?;
|
|
ecx.add_goal(
|
|
goal.with(
|
|
tcx,
|
|
ty::Binder::dummy(ty::OutlivesPredicate(a_region, b_region)),
|
|
),
|
|
);
|
|
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
|
|
},
|
|
|r| CandidateKind::Candidate { name: "upcast dyn to principle".into(), result: *r },
|
|
)
|
|
};
|
|
|
|
let mut responses = vec![];
|
|
// If the principal def ids match (or are both none), then we're not doing
|
|
// trait upcasting. We're just removing auto traits (or shortening the lifetime).
|
|
if a_data.principal_def_id() == b_data.principal_def_id() {
|
|
if let Ok(response) = unsize_dyn_to_principal(a_data.principal()) {
|
|
responses.push(response);
|
|
}
|
|
} else if let Some(a_principal) = a_data.principal()
|
|
&& let Some(b_principal) = b_data.principal()
|
|
{
|
|
for super_trait_ref in supertraits(tcx, a_principal.with_self_ty(tcx, a_ty)) {
|
|
if super_trait_ref.def_id() != b_principal.def_id() {
|
|
continue;
|
|
}
|
|
let erased_trait_ref = super_trait_ref
|
|
.map_bound(|trait_ref| ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref));
|
|
if let Ok(response) = unsize_dyn_to_principal(Some(erased_trait_ref)) {
|
|
responses.push(response);
|
|
}
|
|
}
|
|
}
|
|
|
|
responses
|
|
}
|
|
|
|
fn consider_builtin_discriminant_kind_candidate(
|
|
ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
if goal.predicate.polarity != ty::ImplPolarity::Positive {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
// `DiscriminantKind` is automatically implemented for every type.
|
|
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> {
|
|
if goal.predicate.polarity != ty::ImplPolarity::Positive {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
if !goal.param_env.is_const() {
|
|
// `Destruct` is automatically implemented for every type in
|
|
// non-const environments.
|
|
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
|
|
} else {
|
|
// FIXME(-Ztrait-solver=next): Implement this when we get const working in the new solver
|
|
Err(NoSolution)
|
|
}
|
|
}
|
|
|
|
fn consider_builtin_transmute_candidate(
|
|
ecx: &mut EvalCtxt<'_, 'tcx>,
|
|
goal: Goal<'tcx, Self>,
|
|
) -> QueryResult<'tcx> {
|
|
if goal.predicate.polarity != ty::ImplPolarity::Positive {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
// `rustc_transmute` does not have support for type or const params
|
|
if goal.has_non_region_placeholders() {
|
|
return Err(NoSolution);
|
|
}
|
|
|
|
// Erase regions because we compute layouts in `rustc_transmute`,
|
|
// which will ICE for region vars.
|
|
let substs = ecx.tcx().erase_regions(goal.predicate.trait_ref.substs);
|
|
|
|
let Some(assume) = rustc_transmute::Assume::from_const(
|
|
ecx.tcx(),
|
|
goal.param_env,
|
|
substs.const_at(3),
|
|
) else {
|
|
return Err(NoSolution);
|
|
};
|
|
|
|
let certainty = ecx.is_transmutable(
|
|
rustc_transmute::Types { dst: substs.type_at(0), src: substs.type_at(1) },
|
|
substs.type_at(2),
|
|
assume,
|
|
)?;
|
|
ecx.evaluate_added_goals_and_make_canonical_response(certainty)
|
|
}
|
|
}
|
|
|
|
impl<'tcx> EvalCtxt<'_, 'tcx> {
|
|
// Return `Some` if there is an impl (built-in or user provided) that may
|
|
// hold for the self type of the goal, which for coherence and soundness
|
|
// purposes must disqualify the built-in auto impl assembled by considering
|
|
// the type's constituent types.
|
|
fn disqualify_auto_trait_candidate_due_to_possible_impl(
|
|
&mut self,
|
|
goal: Goal<'tcx, TraitPredicate<'tcx>>,
|
|
) -> Option<QueryResult<'tcx>> {
|
|
let self_ty = goal.predicate.self_ty();
|
|
match *self_ty.kind() {
|
|
// Stall int and float vars until they are resolved to a concrete
|
|
// numerical type. That's because the check for impls below treats
|
|
// int vars as matching any impl. Even if we filtered such impls,
|
|
// we probably don't want to treat an `impl !AutoTrait for i32` as
|
|
// disqualifying the built-in auto impl for `i64: AutoTrait` either.
|
|
ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => {
|
|
Some(self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS))
|
|
}
|
|
|
|
// These types cannot be structurally decomposed into constituent
|
|
// types, and therefore have no built-in auto impl.
|
|
ty::Dynamic(..)
|
|
| ty::Param(..)
|
|
| ty::Foreign(..)
|
|
| ty::Alias(ty::Projection | ty::Weak | ty::Inherent, ..)
|
|
| ty::Placeholder(..) => Some(Err(NoSolution)),
|
|
|
|
ty::Infer(_) | ty::Bound(_, _) => bug!("unexpected type `{self_ty}`"),
|
|
|
|
// Generators have one special built-in candidate, `Unpin`, which
|
|
// takes precedence over the structural auto trait candidate being
|
|
// assembled.
|
|
ty::Generator(_, _, movability)
|
|
if Some(goal.predicate.def_id()) == self.tcx().lang_items().unpin_trait() =>
|
|
{
|
|
match movability {
|
|
Movability::Static => Some(Err(NoSolution)),
|
|
Movability::Movable => {
|
|
Some(self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes))
|
|
}
|
|
}
|
|
}
|
|
|
|
// For rigid types, any possible implementation that could apply to
|
|
// the type (even if after unification and processing nested goals
|
|
// it does not hold) will disqualify the built-in auto impl.
|
|
//
|
|
// This differs from the current stable behavior and fixes #84857.
|
|
// Due to breakage found via crater, we currently instead lint
|
|
// patterns which can be used to exploit this unsoundness on stable,
|
|
// see #93367 for more details.
|
|
ty::Bool
|
|
| ty::Char
|
|
| ty::Int(_)
|
|
| ty::Uint(_)
|
|
| ty::Float(_)
|
|
| ty::Str
|
|
| ty::Array(_, _)
|
|
| ty::Slice(_)
|
|
| ty::RawPtr(_)
|
|
| ty::Ref(_, _, _)
|
|
| ty::FnDef(_, _)
|
|
| ty::FnPtr(_)
|
|
| ty::Closure(_, _)
|
|
| ty::Generator(_, _, _)
|
|
| ty::GeneratorWitness(_)
|
|
| ty::GeneratorWitnessMIR(_, _)
|
|
| ty::Never
|
|
| ty::Tuple(_)
|
|
| ty::Adt(_, _)
|
|
// FIXME: Handling opaques here is kinda sus. Especially because we
|
|
// simplify them to PlaceholderSimplifiedType.
|
|
| ty::Alias(ty::Opaque, _) => {
|
|
let mut disqualifying_impl = None;
|
|
self.tcx().for_each_relevant_impl_treating_projections(
|
|
goal.predicate.def_id(),
|
|
goal.predicate.self_ty(),
|
|
TreatProjections::NextSolverLookup,
|
|
|impl_def_id| {
|
|
disqualifying_impl = Some(impl_def_id);
|
|
},
|
|
);
|
|
if let Some(def_id) = disqualifying_impl {
|
|
debug!(?def_id, ?goal, "disqualified auto-trait implementation");
|
|
// No need to actually consider the candidate here,
|
|
// since we do that in `consider_impl_candidate`.
|
|
return Some(Err(NoSolution));
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
ty::Error(_) => None,
|
|
}
|
|
}
|
|
|
|
/// Convenience function for traits that are structural, i.e. that only
|
|
/// have nested subgoals that only change the self type. Unlike other
|
|
/// evaluate-like helpers, this does a probe, so it doesn't need to be
|
|
/// wrapped in one.
|
|
fn probe_and_evaluate_goal_for_constituent_tys(
|
|
&mut self,
|
|
goal: Goal<'tcx, TraitPredicate<'tcx>>,
|
|
constituent_tys: impl Fn(&EvalCtxt<'_, 'tcx>, Ty<'tcx>) -> Result<Vec<Ty<'tcx>>, NoSolution>,
|
|
) -> QueryResult<'tcx> {
|
|
self.probe(
|
|
|ecx| {
|
|
ecx.add_goals(
|
|
constituent_tys(ecx, goal.predicate.self_ty())?
|
|
.into_iter()
|
|
.map(|ty| {
|
|
goal.with(
|
|
ecx.tcx(),
|
|
ty::Binder::dummy(goal.predicate.with_self_ty(ecx.tcx(), ty)),
|
|
)
|
|
})
|
|
.collect::<Vec<_>>(),
|
|
);
|
|
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
|
|
},
|
|
|r| CandidateKind::Candidate { name: "constituent tys".into(), result: *r },
|
|
)
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
pub(super) fn compute_trait_goal(
|
|
&mut self,
|
|
goal: Goal<'tcx, TraitPredicate<'tcx>>,
|
|
) -> QueryResult<'tcx> {
|
|
let candidates = self.assemble_and_evaluate_candidates(goal);
|
|
self.merge_candidates(candidates)
|
|
}
|
|
}
|