diff --git a/compiler/rustc_trait_selection/src/solve/assembly.rs b/compiler/rustc_trait_selection/src/solve/assembly.rs index 891ea0cdebe..76cde1a6692 100644 --- a/compiler/rustc_trait_selection/src/solve/assembly.rs +++ b/compiler/rustc_trait_selection/src/solve/assembly.rs @@ -224,7 +224,9 @@ pub(super) fn assemble_and_evaluate_candidates>( if goal.predicate.self_ty().is_ty_var() { return vec![Candidate { source: CandidateSource::BuiltinImpl, - result: self.make_canonical_response(Certainty::AMBIGUOUS).unwrap(), + result: self + .evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) + .unwrap(), }]; } @@ -261,8 +263,9 @@ fn assemble_candidates_after_normalizing_self_ty>( let &ty::Alias(ty::Projection, projection_ty) = goal.predicate.self_ty().kind() else { return }; - self.probe(|this| { - let normalized_ty = this.next_ty_infer(); + + self.probe(|ecx| { + let normalized_ty = ecx.next_ty_infer(); let normalizes_to_goal = goal.with( tcx, ty::Binder::dummy(ty::ProjectionPredicate { @@ -270,28 +273,16 @@ fn assemble_candidates_after_normalizing_self_ty>( term: normalized_ty.into(), }), ); - let normalization_certainty = match this.evaluate_goal(normalizes_to_goal) { - Ok((_, certainty)) => certainty, - Err(NoSolution) => return, - }; - let normalized_ty = this.resolve_vars_if_possible(normalized_ty); + ecx.add_goal(normalizes_to_goal); + if let Ok(_) = ecx.try_evaluate_added_goals() { + let normalized_ty = ecx.resolve_vars_if_possible(normalized_ty); - // 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 winnowing. - let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty)); - let normalized_candidates = this.assemble_and_evaluate_candidates(goal); - for mut normalized_candidate in normalized_candidates { - normalized_candidate.result = - normalized_candidate.result.unchecked_map(|mut response| { - // FIXME: This currently hides overflow in the normalization step of the self type - // which is probably wrong. Maybe `unify_and` should actually keep overflow as - // we treat it as non-fatal anyways. - response.certainty = response.certainty.unify_and(normalization_certainty); - response - }); - candidates.push(normalized_candidate); + // 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 winnowing. + let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty)); + candidates.extend(ecx.assemble_and_evaluate_candidates(goal)); } - }) + }); } fn assemble_impl_candidates>( @@ -516,7 +507,7 @@ pub(super) fn merge_candidates_and_discard_reservation_impls( } else { Certainty::AMBIGUOUS }; - return self.make_canonical_response(certainty); + return self.evaluate_added_goals_and_make_canonical_response(certainty); } } @@ -538,14 +529,16 @@ fn trait_candidate_should_be_dropped_in_favor_of( } } - fn discard_reservation_impl(&self, mut candidate: Candidate<'tcx>) -> Candidate<'tcx> { + fn discard_reservation_impl(&mut self, mut candidate: Candidate<'tcx>) -> Candidate<'tcx> { if let CandidateSource::Impl(def_id) = candidate.source { if let ty::ImplPolarity::Reservation = self.tcx().impl_polarity(def_id) { debug!("Selected reservation impl"); // We assemble all candidates inside of a probe so by // making a new canonical response here our result will // have no constraints. - candidate.result = self.make_canonical_response(Certainty::AMBIGUOUS).unwrap(); + candidate.result = self + .evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) + .unwrap(); } } diff --git a/compiler/rustc_trait_selection/src/solve/canonical/mod.rs b/compiler/rustc_trait_selection/src/solve/canonical/mod.rs index 8c3be8da16b..01a011a000e 100644 --- a/compiler/rustc_trait_selection/src/solve/canonical/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/canonical/mod.rs @@ -48,7 +48,20 @@ pub(super) fn canonicalize_goal( /// - `external_constraints`: additional constraints which aren't expressable /// using simple unification of inference variables. #[instrument(level = "debug", skip(self))] - pub(super) fn make_canonical_response(&self, certainty: Certainty) -> QueryResult<'tcx> { + pub(super) fn evaluate_added_goals_and_make_canonical_response( + &mut self, + certainty: Certainty, + ) -> QueryResult<'tcx> { + let goals_certainty = self.try_evaluate_added_goals()?; + let certainty = certainty.unify_and(goals_certainty); + + if let Certainty::Yes = certainty { + assert!( + self.nested_goals.is_empty(), + "Cannot be certain of query response if unevaluated goals exist" + ); + } + let external_constraints = self.compute_external_query_constraints()?; let response = Response { var_values: self.var_values, external_constraints, certainty }; @@ -209,7 +222,7 @@ fn unify_query_var_values( // FIXME: To deal with #105787 I also expect us to emit nested obligations here at // some point. We can figure out how to deal with this once we actually have // an ICE. - let nested_goals = self.eq(param_env, orig, response)?; + let nested_goals = self.eq_and_get_goals(param_env, orig, response)?; assert!(nested_goals.is_empty(), "{nested_goals:?}"); } diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs index 856f1eec443..1e481f165be 100644 --- a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs +++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs @@ -13,8 +13,7 @@ use rustc_span::DUMMY_SP; use std::ops::ControlFlow; -use super::search_graph::SearchGraph; -use super::Goal; +use super::{search_graph::SearchGraph, Goal}; pub struct EvalCtxt<'a, 'tcx> { // FIXME: should be private. @@ -33,14 +32,35 @@ pub struct EvalCtxt<'a, 'tcx> { pub(super) search_graph: &'a mut SearchGraph<'tcx>, - /// This field is used by a debug assertion in [`EvalCtxt::evaluate_goal`], - /// see the comment in that method for more details. - pub in_projection_eq_hack: bool, + pub(super) nested_goals: NestedGoals<'tcx>, +} + +#[derive(Debug, Clone)] +pub(super) struct NestedGoals<'tcx> { + pub(super) projection_eq_hack_goal: Option>>, + pub(super) goals: Vec>>, +} + +impl NestedGoals<'_> { + pub(super) fn new() -> Self { + Self { projection_eq_hack_goal: None, goals: Vec::new() } + } + + pub(super) fn is_empty(&self) -> bool { + self.projection_eq_hack_goal.is_none() && self.goals.is_empty() + } } impl<'tcx> EvalCtxt<'_, 'tcx> { pub(super) fn probe(&mut self, f: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> T) -> T { - self.infcx.probe(|_| f(self)) + let mut ecx = EvalCtxt { + infcx: self.infcx, + var_values: self.var_values, + max_input_universe: self.max_input_universe, + search_graph: self.search_graph, + nested_goals: self.nested_goals.clone(), + }; + self.infcx.probe(|_| f(&mut ecx)) } pub(super) fn tcx(&self) -> TyCtxt<'tcx> { @@ -61,6 +81,15 @@ pub(super) fn next_const_infer(&self, ty: Ty<'tcx>) -> ty::Const<'tcx> { ) } + /// Returns a ty infer or a const infer depending on whether `kind` is a `Ty` or `Const`. + /// If `kind` is an integer inference variable this will still return a ty infer var. + pub(super) fn next_term_infer_of_kind(&self, kind: ty::Term<'tcx>) -> ty::Term<'tcx> { + match kind.unpack() { + ty::TermKind::Ty(_) => self.next_ty_infer().into(), + ty::TermKind::Const(ct) => self.next_const_infer(ct.ty()).into(), + } + } + /// Is the projection predicate is of the form `exists ::Assoc = T`. /// /// This is the case if the `term` is an inference variable in the innermost universe @@ -137,6 +166,25 @@ fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow { #[instrument(level = "debug", skip(self, param_env), ret)] pub(super) fn eq>( + &mut self, + param_env: ty::ParamEnv<'tcx>, + lhs: T, + rhs: T, + ) -> Result<(), NoSolution> { + self.infcx + .at(&ObligationCause::dummy(), param_env) + .eq(DefineOpaqueTypes::No, lhs, rhs) + .map(|InferOk { value: (), obligations }| { + self.add_goals(obligations.into_iter().map(|o| o.into())); + }) + .map_err(|e| { + debug!(?e, "failed to equate"); + NoSolution + }) + } + + #[instrument(level = "debug", skip(self, param_env), ret)] + pub(super) fn eq_and_get_goals>( &self, param_env: ty::ParamEnv<'tcx>, lhs: T, diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs index a873060687d..79e295f6b53 100644 --- a/compiler/rustc_trait_selection/src/solve/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/mod.rs @@ -45,6 +45,8 @@ pub use eval_ctxt::EvalCtxt; pub use fulfill::FulfillmentCtxt; +use self::eval_ctxt::NestedGoals; + trait CanonicalResponseExt { fn has_no_inference_or_external_constraints(&self) -> bool; } @@ -69,6 +71,7 @@ fn evaluate_root_goal( } impl<'tcx> InferCtxtEvalExt<'tcx> for InferCtxt<'tcx> { + #[instrument(level = "debug", skip(self))] fn evaluate_root_goal( &self, goal: Goal<'tcx, ty::Predicate<'tcx>>, @@ -81,9 +84,9 @@ fn evaluate_root_goal( // Only relevant when canonicalizing the response. max_input_universe: ty::UniverseIndex::ROOT, var_values: CanonicalVarValues::dummy(), - in_projection_eq_hack: false, + nested_goals: NestedGoals::new(), } - .evaluate_goal(goal); + .evaluate_goal(false, goal); assert!(search_graph.is_empty()); result @@ -117,7 +120,7 @@ fn evaluate_canonical_goal( var_values, max_input_universe: canonical_goal.max_universe, search_graph, - in_projection_eq_hack: false, + nested_goals: NestedGoals::new(), }; ecx.compute_goal(goal) }) @@ -127,6 +130,7 @@ fn evaluate_canonical_goal( /// been constrained and the certainty of the result. fn evaluate_goal( &mut self, + is_projection_eq_hack_goal: bool, goal: Goal<'tcx, ty::Predicate<'tcx>>, ) -> Result<(bool, Certainty), NoSolution> { let (orig_values, canonical_goal) = self.canonicalize_goal(goal); @@ -149,10 +153,10 @@ fn evaluate_goal( // solver cycle. if cfg!(debug_assertions) && has_changed - && !self.in_projection_eq_hack + && !is_projection_eq_hack_goal && !self.search_graph.in_cycle() - && false { + debug!("rerunning goal to check result is stable"); let (_orig_values, canonical_goal) = self.canonicalize_goal(goal); let canonical_response = EvalCtxt::evaluate_canonical_goal(self.tcx(), self.search_graph, canonical_goal)?; @@ -202,10 +206,12 @@ fn compute_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> QueryResult ty::PredicateKind::WellFormed(arg) => { self.compute_well_formed_goal(Goal { param_env, predicate: arg }) } - ty::PredicateKind::Ambiguous => self.make_canonical_response(Certainty::AMBIGUOUS), + ty::PredicateKind::Ambiguous => { + self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) + } // FIXME: implement these predicates :) ty::PredicateKind::ConstEvaluatable(_) | ty::PredicateKind::ConstEquate(_, _) => { - self.make_canonical_response(Certainty::Yes) + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } ty::PredicateKind::TypeWellFormedFromEnv(..) => { bug!("TypeWellFormedFromEnv is only used for Chalk") @@ -217,20 +223,25 @@ fn compute_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> QueryResult } else { let kind = self.infcx.instantiate_binder_with_placeholders(kind); let goal = goal.with(self.tcx(), ty::Binder::dummy(kind)); - let (_, certainty) = self.evaluate_goal(goal)?; - self.make_canonical_response(certainty) + // `false` is fine to use as if this were a projection goal from the hack there would not be + // a binder as the real projection goal that is the parent of the hack goal would have already + // had its binder replaced with placeholders. + let (_, certainty) = self.evaluate_goal(false, goal)?; + self.evaluate_added_goals_and_make_canonical_response(certainty) } } + #[instrument(level = "debug", skip(self))] fn compute_type_outlives_goal( &mut self, goal: Goal<'tcx, TypeOutlivesPredicate<'tcx>>, ) -> QueryResult<'tcx> { let ty::OutlivesPredicate(ty, lt) = goal.predicate; self.infcx.register_region_obligation_with_cause(ty, lt, &ObligationCause::dummy()); - self.make_canonical_response(Certainty::Yes) + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } + #[instrument(level = "debug", skip(self))] fn compute_region_outlives_goal( &mut self, goal: Goal<'tcx, RegionOutlivesPredicate<'tcx>>, @@ -239,9 +250,10 @@ fn compute_region_outlives_goal( &ObligationCause::dummy(), ty::Binder::dummy(goal.predicate), ); - self.make_canonical_response(Certainty::Yes) + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } + #[instrument(level = "debug", skip(self))] fn compute_coerce_goal( &mut self, goal: Goal<'tcx, CoercePredicate<'tcx>>, @@ -256,6 +268,7 @@ fn compute_coerce_goal( }) } + #[instrument(level = "debug", skip(self))] fn compute_subtype_goal( &mut self, goal: Goal<'tcx, SubtypePredicate<'tcx>>, @@ -263,18 +276,18 @@ fn compute_subtype_goal( if goal.predicate.a.is_ty_var() && goal.predicate.b.is_ty_var() { // FIXME: Do we want to register a subtype relation between these vars? // That won't actually reflect in the query response, so it seems moot. - self.make_canonical_response(Certainty::AMBIGUOUS) + self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) } else { let InferOk { value: (), obligations } = self .infcx .at(&ObligationCause::dummy(), goal.param_env) .sub(DefineOpaqueTypes::No, goal.predicate.a, goal.predicate.b)?; - self.evaluate_all_and_make_canonical_response( - obligations.into_iter().map(|pred| pred.into()).collect(), - ) + self.add_goals(obligations.into_iter().map(|pred| pred.into())); + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } } + #[instrument(level = "debug", skip(self))] fn compute_closure_kind_goal( &mut self, goal: Goal<'tcx, (DefId, ty::SubstsRef<'tcx>, ty::ClosureKind)>, @@ -283,23 +296,25 @@ fn compute_closure_kind_goal( let found_kind = substs.as_closure().kind_ty().to_opt_closure_kind(); let Some(found_kind) = found_kind else { - return self.make_canonical_response(Certainty::AMBIGUOUS); + return self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS); }; if found_kind.extends(expected_kind) { - self.make_canonical_response(Certainty::Yes) + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } else { Err(NoSolution) } } + #[instrument(level = "debug", skip(self))] fn compute_object_safe_goal(&mut self, trait_def_id: DefId) -> QueryResult<'tcx> { if self.tcx().check_is_object_safe(trait_def_id) { - self.make_canonical_response(Certainty::Yes) + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } else { Err(NoSolution) } } + #[instrument(level = "debug", skip(self))] fn compute_well_formed_goal( &mut self, goal: Goal<'tcx, ty::GenericArg<'tcx>>, @@ -309,10 +324,11 @@ fn compute_well_formed_goal( goal.param_env, goal.predicate, ) { - Some(obligations) => self.evaluate_all_and_make_canonical_response( - obligations.into_iter().map(|o| o.into()).collect(), - ), - None => self.make_canonical_response(Certainty::AMBIGUOUS), + Some(obligations) => { + self.add_goals(obligations.into_iter().map(|o| o.into())); + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + } + None => self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS), } } @@ -326,14 +342,14 @@ fn compute_alias_eq_goal( let evaluate_normalizes_to = |ecx: &mut EvalCtxt<'_, 'tcx>, alias, other| { debug!("evaluate_normalizes_to(alias={:?}, other={:?})", alias, other); let r = ecx.probe(|ecx| { - let (_, certainty) = ecx.evaluate_goal(goal.with( + ecx.add_goal(goal.with( tcx, ty::Binder::dummy(ty::ProjectionPredicate { projection_ty: alias, term: other, }), - ))?; - ecx.make_canonical_response(certainty) + )); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }); debug!("evaluate_normalizes_to(..) -> {:?}", r); r @@ -360,10 +376,10 @@ fn compute_alias_eq_goal( // Evaluate all 3 potential candidates for the alias' being equal candidates.push(evaluate_normalizes_to(self, alias_lhs, goal.predicate.1)); candidates.push(evaluate_normalizes_to(self, alias_rhs, goal.predicate.0)); - candidates.push(self.probe(|this| { + candidates.push(self.probe(|ecx| { debug!("compute_alias_eq_goal: alias defids are equal, equating substs"); - let nested_goals = this.eq(goal.param_env, alias_lhs, alias_rhs)?; - this.evaluate_all_and_make_canonical_response(nested_goals) + ecx.eq(goal.param_env, alias_lhs, alias_rhs)?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) })); debug!(?candidates); @@ -379,25 +395,92 @@ fn compute_const_arg_has_type_goal( goal: Goal<'tcx, (ty::Const<'tcx>, Ty<'tcx>)>, ) -> QueryResult<'tcx> { let (ct, ty) = goal.predicate; - let nested_goals = self.eq(goal.param_env, ct.ty(), ty)?; - self.evaluate_all_and_make_canonical_response(nested_goals) + self.eq(goal.param_env, ct.ty(), ty)?; + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } } impl<'tcx> EvalCtxt<'_, 'tcx> { - // Recursively evaluates a list of goals to completion, returning the certainty - // of all of the goals. - fn evaluate_all( - &mut self, - mut goals: Vec>>, - ) -> Result { - let mut new_goals = Vec::new(); - self.repeat_while_none( + #[instrument(level = "debug", skip(self))] + fn set_projection_eq_hack_goal(&mut self, goal: Goal<'tcx, ty::ProjectionPredicate<'tcx>>) { + assert!( + self.nested_goals.projection_eq_hack_goal.is_none(), + "attempted to set the projection eq hack goal when one already exists" + ); + self.nested_goals.projection_eq_hack_goal = Some(goal); + } + + #[instrument(level = "debug", skip(self))] + fn add_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) { + self.nested_goals.goals.push(goal); + } + + #[instrument(level = "debug", skip(self, goals))] + fn add_goals(&mut self, goals: impl IntoIterator>>) { + let current_len = self.nested_goals.goals.len(); + self.nested_goals.goals.extend(goals); + debug!("added_goals={:?}", &self.nested_goals.goals[current_len..]); + } + + // Recursively evaluates all the goals added to this `EvalCtxt` to completion, returning + // the certainty of all the goals. + #[instrument(level = "debug", skip(self))] + fn try_evaluate_added_goals(&mut self) -> Result { + let mut goals = core::mem::replace(&mut self.nested_goals, NestedGoals::new()); + let mut new_goals = NestedGoals::new(); + + let response = self.repeat_while_none( |_| Ok(Certainty::Maybe(MaybeCause::Overflow)), |this| { let mut has_changed = Err(Certainty::Yes); - for goal in goals.drain(..) { - let (changed, certainty) = match this.evaluate_goal(goal) { + + if let Some(goal) = goals.projection_eq_hack_goal.take() { + let (_, certainty) = match this.evaluate_goal( + true, + goal.with(this.tcx(), ty::Binder::dummy(goal.predicate)), + ) { + Ok(r) => r, + Err(NoSolution) => return Some(Err(NoSolution)), + }; + + if goal.predicate.projection_ty + != this.resolve_vars_if_possible(goal.predicate.projection_ty) + { + has_changed = Ok(()) + } + + match certainty { + Certainty::Yes => {} + Certainty::Maybe(_) => { + let goal = this.resolve_vars_if_possible(goal); + + // The rhs of this `normalizes-to` must always be an unconstrained infer var as it is + // the hack used by `normalizes-to` to ensure that every `normalizes-to` behaves the same + // regardless of the rhs. + // + // However it is important not to unconditionally replace the rhs with a new infer var + // as otherwise we may replace the original unconstrained infer var with a new infer var + // and never propagate any constraints on the new var back to the original var. + let term = this + .term_is_fully_unconstrained(goal) + .then_some(goal.predicate.term) + .unwrap_or_else(|| { + this.next_term_infer_of_kind(goal.predicate.term) + }); + let projection_pred = ty::ProjectionPredicate { + term, + projection_ty: goal.predicate.projection_ty, + }; + new_goals.projection_eq_hack_goal = + Some(goal.with(this.tcx(), projection_pred)); + + has_changed = has_changed.map_err(|c| c.unify_and(certainty)); + } + } + } + + for nested_goal in goals.goals.drain(..) { + let (changed, certainty) = match this.evaluate_goal(false, nested_goal) { Ok(result) => result, Err(NoSolution) => return Some(Err(NoSolution)), }; @@ -409,32 +492,22 @@ fn evaluate_all( match certainty { Certainty::Yes => {} Certainty::Maybe(_) => { - new_goals.push(goal); + new_goals.goals.push(nested_goal); has_changed = has_changed.map_err(|c| c.unify_and(certainty)); } } } + mem::swap(&mut new_goals, &mut goals); match has_changed { - Ok(()) => { - mem::swap(&mut new_goals, &mut goals); - None - } + Ok(()) => None, Err(certainty) => Some(Ok(certainty)), } }, - ) - } + ); - // Recursively evaluates a list of goals to completion, making a query response. - // - // This is just a convenient way of calling [`EvalCtxt::evaluate_all`], - // then [`EvalCtxt::make_canonical_response`]. - fn evaluate_all_and_make_canonical_response( - &mut self, - goals: Vec>>, - ) -> QueryResult<'tcx> { - self.evaluate_all(goals).and_then(|certainty| self.make_canonical_response(certainty)) + self.nested_goals = goals; + response } fn try_merge_responses( @@ -466,7 +539,7 @@ fn try_merge_responses( }); // FIXME(-Ztrait-solver=next): We should take the intersection of the constraints on all the // responses and use that for the constraints of this ambiguous response. - let response = self.make_canonical_response(certainty); + let response = self.evaluate_added_goals_and_make_canonical_response(certainty); if let Ok(response) = &response { assert!(response.has_no_inference_or_external_constraints()); } diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs index dbb8e722c8f..b054a2bda1f 100644 --- a/compiler/rustc_trait_selection/src/solve/project_goals.rs +++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs @@ -20,6 +20,7 @@ use std::iter; impl<'tcx> EvalCtxt<'_, 'tcx> { + #[instrument(level = "debug", skip(self), ret)] pub(super) fn compute_projection_goal( &mut self, goal: Goal<'tcx, ProjectionPredicate<'tcx>>, @@ -36,54 +37,18 @@ pub(super) fn compute_projection_goal( self.merge_candidates_and_discard_reservation_impls(candidates) } else { let predicate = goal.predicate; - let unconstrained_rhs = match predicate.term.unpack() { - ty::TermKind::Ty(_) => self.next_ty_infer().into(), - ty::TermKind::Const(ct) => self.next_const_infer(ct.ty()).into(), - }; - let unconstrained_predicate = ty::Clause::Projection(ProjectionPredicate { + let unconstrained_rhs = self.next_term_infer_of_kind(predicate.term); + let unconstrained_predicate = ProjectionPredicate { projection_ty: goal.predicate.projection_ty, term: unconstrained_rhs, - }); - let (_has_changed, normalize_certainty) = self.in_projection_eq_hack(|this| { - this.evaluate_goal(goal.with(this.tcx(), unconstrained_predicate)) - })?; + }; - let nested_eq_goals = self.eq(goal.param_env, unconstrained_rhs, predicate.term)?; - let eval_certainty = self.evaluate_all(nested_eq_goals)?; - self.make_canonical_response(normalize_certainty.unify_and(eval_certainty)) + self.set_projection_eq_hack_goal(goal.with(self.tcx(), unconstrained_predicate)); + self.try_evaluate_added_goals()?; + self.eq(goal.param_env, unconstrained_rhs, predicate.term)?; + self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } } - - /// This sets a flag used by a debug assert in [`EvalCtxt::evaluate_goal`], - /// see the comment in that method for more details. - fn in_projection_eq_hack(&mut self, f: impl FnOnce(&mut Self) -> T) -> T { - self.in_projection_eq_hack = true; - let result = f(self); - self.in_projection_eq_hack = false; - result - } - - /// After normalizing the projection to `normalized_alias` with the given - /// `normalization_certainty`, constrain the inference variable `term` to it - /// and return a query response. - fn eq_term_and_make_canonical_response( - &mut self, - goal: Goal<'tcx, ProjectionPredicate<'tcx>>, - normalization_certainty: Certainty, - normalized_alias: impl Into>, - ) -> QueryResult<'tcx> { - // The term of our goal should be fully unconstrained, so this should never fail. - // - // It can however be ambiguous when the `normalized_alias` contains a projection. - let nested_goals = self - .eq(goal.param_env, goal.predicate.term, normalized_alias.into()) - .expect("failed to unify with unconstrained term"); - - let unify_certainty = - self.evaluate_all(nested_goals).expect("failed to unify with unconstrained term"); - - self.make_canonical_response(normalization_certainty.unify_and(unify_certainty)) - } } impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { @@ -111,19 +76,14 @@ fn consider_implied_clause( ecx.probe(|ecx| { let assumption_projection_pred = ecx.instantiate_binder_with_infer(poly_projection_pred); - let mut nested_goals = ecx.eq( + ecx.eq( goal.param_env, goal.predicate.projection_ty, assumption_projection_pred.projection_ty, )?; - nested_goals.extend(requirements); - let subst_certainty = ecx.evaluate_all(nested_goals)?; - - ecx.eq_term_and_make_canonical_response( - goal, - subst_certainty, - assumption_projection_pred.term, - ) + ecx.eq(goal.param_env, goal.predicate.term, assumption_projection_pred.term)?; + ecx.add_goals(requirements); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } else { Err(NoSolution) @@ -139,21 +99,22 @@ fn consider_object_bound_candidate( && poly_projection_pred.projection_def_id() == goal.predicate.def_id() { ecx.probe(|ecx| { + let tcx = ecx.tcx(); + let assumption_projection_pred = ecx.instantiate_binder_with_infer(poly_projection_pred); - let mut nested_goals = ecx.eq( + ecx.eq( goal.param_env, goal.predicate.projection_ty, assumption_projection_pred.projection_ty, )?; - let tcx = ecx.tcx(); let ty::Dynamic(bounds, _, _) = *goal.predicate.self_ty().kind() else { bug!("expected object type in `consider_object_bound_candidate`"); }; - nested_goals.extend( + ecx.add_goals( structural_traits::predicates_for_object_candidate( - ecx, + &ecx, goal.param_env, goal.predicate.projection_ty.trait_ref(tcx), bounds, @@ -161,14 +122,8 @@ fn consider_object_bound_candidate( .into_iter() .map(|pred| goal.with(tcx, pred)), ); - - let subst_certainty = ecx.evaluate_all(nested_goals)?; - - ecx.eq_term_and_make_canonical_response( - goal, - subst_certainty, - assumption_projection_pred.term, - ) + ecx.eq(goal.param_env, goal.predicate.term, assumption_projection_pred.term)?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } else { Err(NoSolution) @@ -195,16 +150,15 @@ fn consider_impl_candidate( let impl_substs = ecx.fresh_substs_for_item(impl_def_id); let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs); - let mut nested_goals = ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?; + ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?; + let where_clause_bounds = tcx .predicates_of(impl_def_id) .instantiate(tcx, impl_substs) .predicates .into_iter() .map(|pred| goal.with(tcx, pred)); - - nested_goals.extend(where_clause_bounds); - let match_impl_certainty = ecx.evaluate_all(nested_goals)?; + ecx.add_goals(where_clause_bounds); // In case the associated item is hidden due to specialization, we have to // return ambiguity this would otherwise be incomplete, resulting in @@ -216,7 +170,7 @@ fn consider_impl_candidate( goal.predicate.def_id(), impl_def_id )? else { - return ecx.make_canonical_response(match_impl_certainty.unify_and(Certainty::AMBIGUOUS)); + return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes); }; if !assoc_def.item.defaultness(tcx).has_value() { @@ -263,7 +217,8 @@ fn consider_impl_candidate( ty.map_bound(|ty| ty.into()) }; - ecx.eq_term_and_make_canonical_response(goal, match_impl_certainty, term.subst(tcx, substs)) + ecx.eq(goal.param_env, goal.predicate.term, term.subst(tcx, substs))?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } @@ -308,14 +263,18 @@ fn consider_builtin_fn_trait_candidates( goal_kind: ty::ClosureKind, ) -> QueryResult<'tcx> { let tcx = ecx.tcx(); - let Some(tupled_inputs_and_output) = - structural_traits::extract_tupled_inputs_and_output_from_callable( - tcx, - goal.predicate.self_ty(), - goal_kind, - )? else { - return ecx.make_canonical_response(Certainty::AMBIGUOUS); - }; + let tupled_inputs_and_output = + match structural_traits::extract_tupled_inputs_and_output_from_callable( + tcx, + goal.predicate.self_ty(), + goal_kind, + )? { + Some(tupled_inputs_and_output) => tupled_inputs_and_output, + None => { + return ecx + .evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS); + } + }; let output_is_sized_pred = tupled_inputs_and_output .map_bound(|(_, output)| tcx.at(DUMMY_SP).mk_trait_ref(LangItem::Sized, [output])); @@ -380,13 +339,9 @@ fn consider_builtin_pointee_candidate( [ty::GenericArg::from(goal.predicate.self_ty())], )); - let (_, is_sized_certainty) = - ecx.evaluate_goal(goal.with(tcx, sized_predicate))?; - return ecx.eq_term_and_make_canonical_response( - goal, - is_sized_certainty, - tcx.types.unit, - ); + ecx.add_goal(goal.with(tcx, sized_predicate)); + ecx.eq(goal.param_env, goal.predicate.term, tcx.types.unit.into())?; + return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes); } ty::Adt(def, substs) if def.is_struct() => { @@ -394,12 +349,12 @@ fn consider_builtin_pointee_candidate( None => tcx.types.unit, Some(field_def) => { let self_ty = field_def.ty(tcx, substs); - let new_goal = goal.with( + ecx.add_goal(goal.with( tcx, ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)), - ); - let (_, certainty) = ecx.evaluate_goal(new_goal)?; - return ecx.make_canonical_response(certainty); + )); + return ecx + .evaluate_added_goals_and_make_canonical_response(Certainty::Yes); } } } @@ -408,12 +363,12 @@ fn consider_builtin_pointee_candidate( ty::Tuple(elements) => match elements.last() { None => tcx.types.unit, Some(&self_ty) => { - let new_goal = goal.with( + ecx.add_goal(goal.with( tcx, ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)), - ); - let (_, certainty) = ecx.evaluate_goal(new_goal)?; - return ecx.make_canonical_response(certainty); + )); + return ecx + .evaluate_added_goals_and_make_canonical_response(Certainty::Yes); } }, @@ -426,7 +381,8 @@ fn consider_builtin_pointee_candidate( ), }; - ecx.eq_term_and_make_canonical_response(goal, Certainty::Yes, metadata_ty) + ecx.eq(goal.param_env, goal.predicate.term, metadata_ty.into())?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } @@ -522,7 +478,10 @@ fn consider_builtin_discriminant_kind_candidate( goal: Goal<'tcx, Self>, ) -> QueryResult<'tcx> { let discriminant = goal.predicate.self_ty().discriminant_ty(ecx.tcx()); - ecx.probe(|ecx| ecx.eq_term_and_make_canonical_response(goal, Certainty::Yes, discriminant)) + ecx.probe(|ecx| { + ecx.eq(goal.param_env, goal.predicate.term, discriminant.into())?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + }) } } diff --git a/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs index f1b840aac55..83d77a69c00 100644 --- a/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs @@ -39,9 +39,7 @@ pub(super) fn new(tcx: TyCtxt<'tcx>) -> SearchGraph<'tcx> { } pub(super) fn is_empty(&self) -> bool { - self.stack.is_empty() - && self.provisional_cache.is_empty() - && !self.overflow_data.did_overflow() + self.stack.is_empty() && self.provisional_cache.is_empty() } /// Whether we're currently in a cycle. This should only be used diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs index 7878539817c..108e1d0b13f 100644 --- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs +++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs @@ -47,16 +47,15 @@ fn consider_impl_candidate( let impl_substs = ecx.fresh_substs_for_item(impl_def_id); let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs); - let mut nested_goals = - ecx.eq(goal.param_env, goal.predicate.trait_ref, impl_trait_ref)?; + ecx.eq(goal.param_env, goal.predicate.trait_ref, impl_trait_ref)?; let where_clause_bounds = tcx .predicates_of(impl_def_id) .instantiate(tcx, impl_substs) .predicates .into_iter() .map(|pred| goal.with(tcx, pred)); - nested_goals.extend(where_clause_bounds); - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.add_goals(where_clause_bounds); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } @@ -73,13 +72,13 @@ fn consider_implied_clause( ecx.probe(|ecx| { let assumption_trait_pred = ecx.instantiate_binder_with_infer(poly_trait_pred); - let mut nested_goals = ecx.eq( + ecx.eq( goal.param_env, goal.predicate.trait_ref, assumption_trait_pred.trait_ref, )?; - nested_goals.extend(requirements); - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.add_goals(requirements); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } else { Err(NoSolution) @@ -98,7 +97,7 @@ fn consider_object_bound_candidate( ecx.probe(|ecx| { let assumption_trait_pred = ecx.instantiate_binder_with_infer(poly_trait_pred); - let mut nested_goals = ecx.eq( + ecx.eq( goal.param_env, goal.predicate.trait_ref, assumption_trait_pred.trait_ref, @@ -108,9 +107,9 @@ fn consider_object_bound_candidate( let ty::Dynamic(bounds, _, _) = *goal.predicate.self_ty().kind() else { bug!("expected object type in `consider_object_bound_candidate`"); }; - nested_goals.extend( + ecx.add_goals( structural_traits::predicates_for_object_candidate( - ecx, + &ecx, goal.param_env, goal.predicate.trait_ref, bounds, @@ -118,8 +117,7 @@ fn consider_object_bound_candidate( .into_iter() .map(|pred| goal.with(tcx, pred)), ); - - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } else { Err(NoSolution) @@ -166,9 +164,8 @@ fn consider_trait_alias_candidate( let nested_obligations = tcx .predicates_of(goal.predicate.def_id()) .instantiate(tcx, goal.predicate.trait_ref.substs); - ecx.evaluate_all_and_make_canonical_response( - nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p)).collect(), - ) + ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p))); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } @@ -197,7 +194,7 @@ fn consider_builtin_pointer_like_candidate( goal: Goal<'tcx, Self>, ) -> QueryResult<'tcx> { if goal.predicate.self_ty().has_non_region_infer() { - return ecx.make_canonical_response(Certainty::AMBIGUOUS); + return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS); } let tcx = ecx.tcx(); @@ -209,7 +206,7 @@ fn consider_builtin_pointer_like_candidate( && layout.layout.align().abi == usize_layout.align().abi { // FIXME: We could make this faster by making a no-constraints response - ecx.make_canonical_response(Certainty::Yes) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } else { Err(NoSolution) } @@ -227,7 +224,7 @@ fn consider_builtin_fn_trait_candidates( goal.predicate.self_ty(), goal_kind, )? else { - return ecx.make_canonical_response(Certainty::AMBIGUOUS); + return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS); }; let output_is_sized_pred = tupled_inputs_and_output .map_bound(|(_, output)| tcx.at(DUMMY_SP).mk_trait_ref(LangItem::Sized, [output])); @@ -247,7 +244,7 @@ fn consider_builtin_tuple_candidate( goal: Goal<'tcx, Self>, ) -> QueryResult<'tcx> { if let ty::Tuple(..) = goal.predicate.self_ty().kind() { - ecx.make_canonical_response(Certainty::Yes) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } else { Err(NoSolution) } @@ -257,7 +254,7 @@ fn consider_builtin_pointee_candidate( ecx: &mut EvalCtxt<'_, 'tcx>, _goal: Goal<'tcx, Self>, ) -> QueryResult<'tcx> { - ecx.make_canonical_response(Certainty::Yes) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } fn consider_builtin_future_candidate( @@ -277,7 +274,7 @@ fn consider_builtin_future_candidate( // Async generator unconditionally implement `Future` // Technically, we need to check that the future output type is Sized, // but that's already proven by the generator being WF. - ecx.make_canonical_response(Certainty::Yes) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } fn consider_builtin_generator_candidate( @@ -317,7 +314,7 @@ fn consider_builtin_unsize_candidate( let a_ty = goal.predicate.self_ty(); let b_ty = goal.predicate.trait_ref.substs.type_at(1); if b_ty.is_ty_var() { - return ecx.make_canonical_response(Certainty::AMBIGUOUS); + return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS); } ecx.probe(|ecx| { match (a_ty.kind(), b_ty.kind()) { @@ -326,7 +323,7 @@ fn consider_builtin_unsize_candidate( // Dyn upcasting is handled separately, since due to upcasting, // when there are two supertraits that differ by substs, we // may return more than one query response. - return Err(NoSolution); + Err(NoSolution) } // `T` -> `dyn Trait` unsizing (_, &ty::Dynamic(data, region, ty::Dyn)) => { @@ -341,29 +338,31 @@ fn consider_builtin_unsize_candidate( let Some(sized_def_id) = tcx.lang_items().sized_trait() else { return Err(NoSolution); }; - let nested_goals: Vec<_> = data - .iter() - // Check that the type implements all of the predicates of the def-id. - // (i.e. the principal, all of the associated types match, and any auto traits) - .map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))) - .chain([ - // The type must be Sized to be unsized. - goal.with( - tcx, - ty::Binder::dummy(tcx.mk_trait_ref(sized_def_id, [a_ty])), - ), - // The type must outlive the lifetime of the `dyn` we're unsizing into. - goal.with(tcx, ty::Binder::dummy(ty::OutlivesPredicate(a_ty, region))), - ]) - .collect(); - - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.add_goals( + data.iter() + // Check that the type implements all of the predicates of the def-id. + // (i.e. the principal, all of the associated types match, and any auto traits) + .map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))) + .chain([ + // The type must be Sized to be unsized. + goal.with( + tcx, + ty::Binder::dummy(tcx.mk_trait_ref(sized_def_id, [a_ty])), + ), + // The type must outlive the lifetime of the `dyn` we're unsizing into. + goal.with( + tcx, + ty::Binder::dummy(ty::OutlivesPredicate(a_ty, region)), + ), + ]), + ); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } // `[T; n]` -> `[T]` unsizing (&ty::Array(a_elem_ty, ..), &ty::Slice(b_elem_ty)) => { // We just require that the element type stays the same - let nested_goals = ecx.eq(goal.param_env, a_elem_ty, b_elem_ty)?; - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.eq(goal.param_env, a_elem_ty, b_elem_ty)?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } // Struct unsizing `Struct` -> `Struct` where `T: Unsize` (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs)) @@ -397,15 +396,14 @@ fn consider_builtin_unsize_candidate( // Finally, we require that `TailA: Unsize` for the tail field // types. - let mut nested_goals = ecx.eq(goal.param_env, unsized_a_ty, b_ty)?; - nested_goals.push(goal.with( + ecx.eq(goal.param_env, unsized_a_ty, b_ty)?; + ecx.add_goal(goal.with( tcx, ty::Binder::dummy( tcx.mk_trait_ref(goal.predicate.def_id(), [a_tail_ty, b_tail_ty]), ), )); - - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } // Tuple unsizing `(.., T)` -> `(.., U)` where `T: Unsize` (&ty::Tuple(a_tys), &ty::Tuple(b_tys)) @@ -417,17 +415,16 @@ fn consider_builtin_unsize_candidate( // 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()); - let mut nested_goals = ecx.eq(goal.param_env, unsized_a_ty, b_ty)?; + ecx.eq(goal.param_env, unsized_a_ty, b_ty)?; // Similar to ADTs, require that the rest of the fields are equal. - nested_goals.push(goal.with( + ecx.add_goal(goal.with( tcx, ty::Binder::dummy( tcx.mk_trait_ref(goal.predicate.def_id(), [*a_last_ty, *b_last_ty]), ), )); - - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } _ => Err(NoSolution), } @@ -477,12 +474,11 @@ fn consider_builtin_dyn_upcast_candidates( 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. - let mut nested_obligations = ecx.eq(goal.param_env, new_a_ty, b_ty)?; - nested_obligations.push( + 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_all_and_make_canonical_response(nested_obligations) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) }; @@ -516,7 +512,7 @@ fn consider_builtin_discriminant_kind_candidate( _goal: Goal<'tcx, Self>, ) -> QueryResult<'tcx> { // `DiscriminantKind` is automatically implemented for every type. - ecx.make_canonical_response(Certainty::Yes) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } } @@ -530,21 +526,23 @@ fn probe_and_evaluate_goal_for_constituent_tys( goal: Goal<'tcx, TraitPredicate<'tcx>>, constituent_tys: impl Fn(&EvalCtxt<'_, 'tcx>, Ty<'tcx>) -> Result>, NoSolution>, ) -> QueryResult<'tcx> { - self.probe(|this| { - this.evaluate_all_and_make_canonical_response( - constituent_tys(this, goal.predicate.self_ty())? + self.probe(|ecx| { + ecx.add_goals( + constituent_tys(ecx, goal.predicate.self_ty())? .into_iter() .map(|ty| { goal.with( - this.tcx(), - ty::Binder::dummy(goal.predicate.with_self_ty(this.tcx(), ty)), + ecx.tcx(), + ty::Binder::dummy(goal.predicate.with_self_ty(ecx.tcx(), ty)), ) }) - .collect(), - ) + .collect::>(), + ); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }) } + #[instrument(level = "debug", skip(self))] pub(super) fn compute_trait_goal( &mut self, goal: Goal<'tcx, TraitPredicate<'tcx>>, diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs b/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs index d7d93377cf1..871e7c2cc5a 100644 --- a/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs +++ b/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs @@ -333,7 +333,7 @@ fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { // FIXME: Technically this folder could be fallible? let nested = self .ecx - .eq(self.param_env, alias_ty, proj.projection_ty) + .eq_and_get_goals(self.param_env, alias_ty, proj.projection_ty) .expect("expected to be able to unify goal projection with dyn's projection"); // FIXME: Technically we could register these too.. assert!(nested.is_empty(), "did not expect unification to have any nested goals");