diff options
5 files changed, 280 insertions, 298 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/alias_relate.rs b/compiler/rustc_trait_selection/src/solve/alias_relate.rs index ca7fcfd8ca1..422a6ee3442 100644 --- a/compiler/rustc_trait_selection/src/solve/alias_relate.rs +++ b/compiler/rustc_trait_selection/src/solve/alias_relate.rs @@ -1,6 +1,5 @@ use super::{EvalCtxt, SolverMode}; use rustc_infer::traits::query::NoSolution; -use rustc_middle::traits::solve::inspect::CandidateKind; use rustc_middle::traits::solve::{Certainty, Goal, QueryResult}; use rustc_middle::ty; @@ -110,12 +109,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { direction: ty::AliasRelationDirection, invert: Invert, ) -> QueryResult<'tcx> { - self.probe(|r| CandidateKind::Candidate { name: "normalizes-to".into(), result: *r }).enter( - |ecx| { - ecx.normalizes_to_inner(param_env, alias, other, direction, invert)?; - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - }, - ) + self.probe_candidate("normalizes-to").enter(|ecx| { + ecx.normalizes_to_inner(param_env, alias, other, direction, invert)?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + }) } fn normalizes_to_inner( @@ -156,20 +153,18 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { alias_rhs: ty::AliasTy<'tcx>, direction: ty::AliasRelationDirection, ) -> QueryResult<'tcx> { - self.probe(|r| CandidateKind::Candidate { name: "substs relate".into(), result: *r }).enter( - |ecx| { - match direction { - ty::AliasRelationDirection::Equate => { - ecx.eq(param_env, alias_lhs, alias_rhs)?; - } - ty::AliasRelationDirection::Subtype => { - ecx.sub(param_env, alias_lhs, alias_rhs)?; - } + self.probe_candidate("substs relate").enter(|ecx| { + match direction { + ty::AliasRelationDirection::Equate => { + ecx.eq(param_env, alias_lhs, alias_rhs)?; + } + ty::AliasRelationDirection::Subtype => { + ecx.sub(param_env, alias_lhs, alias_rhs)?; } + } - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - }, - ) + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + }) } fn assemble_bidirectional_normalizes_to_candidate( @@ -179,23 +174,22 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { rhs: ty::Term<'tcx>, direction: ty::AliasRelationDirection, ) -> QueryResult<'tcx> { - self.probe(|r| CandidateKind::Candidate { name: "bidir normalizes-to".into(), result: *r }) - .enter(|ecx| { - ecx.normalizes_to_inner( - param_env, - lhs.to_alias_ty(ecx.tcx()).unwrap(), - rhs, - direction, - Invert::No, - )?; - ecx.normalizes_to_inner( - param_env, - rhs.to_alias_ty(ecx.tcx()).unwrap(), - lhs, - direction, - Invert::Yes, - )?; - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - }) + self.probe_candidate("bidir normalizes-to").enter(|ecx| { + ecx.normalizes_to_inner( + param_env, + lhs.to_alias_ty(ecx.tcx()).unwrap(), + rhs, + direction, + Invert::No, + )?; + ecx.normalizes_to_inner( + param_env, + rhs.to_alias_ty(ecx.tcx()).unwrap(), + lhs, + direction, + Invert::Yes, + )?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + }) } } diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs index 6b7be73b631..f98997e115d 100644 --- a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs +++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs @@ -9,7 +9,7 @@ use rustc_infer::infer::{ use rustc_infer::traits::query::NoSolution; use rustc_infer::traits::ObligationCause; use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind}; -use rustc_middle::traits::solve::inspect::{self, CandidateKind}; +use rustc_middle::traits::solve::inspect; use rustc_middle::traits::solve::{ CanonicalInput, CanonicalResponse, Certainty, IsNormalizesToHack, MaybeCause, PredefinedOpaques, PredefinedOpaquesData, QueryResult, @@ -880,25 +880,19 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { if candidate_key.def_id != key.def_id { continue; } - values.extend( - self.probe(|r| CandidateKind::Candidate { - name: "opaque type storage".into(), - result: *r, - }) - .enter(|ecx| { - for (a, b) in std::iter::zip(candidate_key.substs, key.substs) { - ecx.eq(param_env, a, b)?; - } - ecx.eq(param_env, candidate_ty, ty)?; - ecx.add_item_bounds_for_hidden_type( - candidate_key.def_id.to_def_id(), - candidate_key.substs, - param_env, - candidate_ty, - ); - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - }), - ); + values.extend(self.probe_candidate("opaque type storage").enter(|ecx| { + for (a, b) in std::iter::zip(candidate_key.substs, key.substs) { + ecx.eq(param_env, a, b)?; + } + ecx.eq(param_env, candidate_ty, ty)?; + ecx.add_item_bounds_for_hidden_type( + candidate_key.def_id.to_def_id(), + candidate_key.substs, + param_env, + candidate_ty, + ); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + })); } values } diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/probe.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/probe.rs index 5d912fc039d..4477ea7d501 100644 --- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/probe.rs +++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/probe.rs @@ -1,5 +1,5 @@ use super::EvalCtxt; -use rustc_middle::traits::solve::inspect; +use rustc_middle::traits::solve::{inspect, QueryResult}; use std::marker::PhantomData; pub(in crate::solve) struct ProbeCtxt<'me, 'a, 'tcx, F, T> { @@ -44,4 +44,24 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> { { ProbeCtxt { ecx: self, probe_kind, _result: PhantomData } } + + pub(in crate::solve) fn probe_candidate( + &mut self, + name: &'static str, + ) -> ProbeCtxt< + '_, + 'a, + 'tcx, + impl FnOnce(&QueryResult<'tcx>) -> inspect::CandidateKind<'tcx>, + QueryResult<'tcx>, + > { + ProbeCtxt { + ecx: self, + probe_kind: move |result: &QueryResult<'tcx>| inspect::CandidateKind::Candidate { + name: name.to_string(), + result: *result, + }, + _result: PhantomData, + } + } } diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs index cbea8009f02..14fff4ab661 100644 --- a/compiler/rustc_trait_selection/src/solve/project_goals.rs +++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs @@ -112,23 +112,18 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { ) -> QueryResult<'tcx> { if let Some(projection_pred) = assumption.as_projection_clause() { if projection_pred.projection_def_id() == goal.predicate.def_id() { - ecx.probe(|r| CandidateKind::Candidate { name: "assumption".into(), result: *r }) - .enter(|ecx| { - let assumption_projection_pred = - ecx.instantiate_binder_with_infer(projection_pred); - ecx.eq( - goal.param_env, - goal.predicate.projection_ty, - assumption_projection_pred.projection_ty, - )?; - ecx.eq( - goal.param_env, - goal.predicate.term, - assumption_projection_pred.term, - ) + ecx.probe_candidate("assumption").enter(|ecx| { + let assumption_projection_pred = + ecx.instantiate_binder_with_infer(projection_pred); + ecx.eq( + goal.param_env, + goal.predicate.projection_ty, + assumption_projection_pred.projection_ty, + )?; + ecx.eq(goal.param_env, goal.predicate.term, assumption_projection_pred.term) .expect("expected goal term to be fully unconstrained"); - then(ecx) - }) + then(ecx) + }) } else { Err(NoSolution) } @@ -329,69 +324,53 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { goal: Goal<'tcx, Self>, ) -> QueryResult<'tcx> { let tcx = ecx.tcx(); - ecx.probe(|r| CandidateKind::Candidate { name: "builtin pointee".into(), result: *r }) - .enter(|ecx| { - let metadata_ty = match goal.predicate.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::Generator(..) - | ty::GeneratorWitness(..) - | ty::GeneratorWitnessMIR(..) - | ty::Never - | ty::Foreign(..) => tcx.types.unit, - - ty::Error(e) => tcx.ty_error(*e), - - ty::Str | ty::Slice(_) => tcx.types.usize, - - ty::Dynamic(_, _, _) => { - let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None); - tcx.type_of(dyn_metadata) - .subst(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())]) - } - - ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => { - // FIXME(ptr_metadata): It would also be possible to return a `Ok(Ambig)` with no constraints. - let sized_predicate = ty::TraitRef::from_lang_item( - tcx, - LangItem::Sized, - DUMMY_SP, - [ty::GenericArg::from(goal.predicate.self_ty())], - ); - ecx.add_goal(goal.with(tcx, sized_predicate)); - tcx.types.unit - } + ecx.probe_candidate("builtin pointee").enter(|ecx| { + let metadata_ty = match goal.predicate.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::Generator(..) + | ty::GeneratorWitness(..) + | ty::GeneratorWitnessMIR(..) + | ty::Never + | ty::Foreign(..) => tcx.types.unit, + + ty::Error(e) => tcx.ty_error(*e), + + ty::Str | ty::Slice(_) => tcx.types.usize, + + ty::Dynamic(_, _, _) => { + let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None); + tcx.type_of(dyn_metadata) + .subst(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())]) + } - ty::Adt(def, substs) if def.is_struct() => { - match def.non_enum_variant().fields.raw.last() { - None => tcx.types.unit, - Some(field_def) => { - let self_ty = field_def.ty(tcx, substs); - ecx.add_goal(goal.with( - tcx, - ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)), - )); - return ecx.evaluate_added_goals_and_make_canonical_response( - Certainty::Yes, - ); - } - } - } - ty::Adt(_, _) => tcx.types.unit, + ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => { + // FIXME(ptr_metadata): It would also be possible to return a `Ok(Ambig)` with no constraints. + let sized_predicate = ty::TraitRef::from_lang_item( + tcx, + LangItem::Sized, + DUMMY_SP, + [ty::GenericArg::from(goal.predicate.self_ty())], + ); + ecx.add_goal(goal.with(tcx, sized_predicate)); + tcx.types.unit + } - ty::Tuple(elements) => match elements.last() { + ty::Adt(def, substs) if def.is_struct() => { + match def.non_enum_variant().fields.raw.last() { None => tcx.types.unit, - Some(&self_ty) => { + Some(field_def) => { + let self_ty = field_def.ty(tcx, substs); ecx.add_goal(goal.with( tcx, ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)), @@ -399,21 +378,35 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { return ecx .evaluate_added_goals_and_make_canonical_response(Certainty::Yes); } - }, - - ty::Infer( - ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_), - ) - | ty::Bound(..) => bug!( - "unexpected self ty `{:?}` when normalizing `<T as Pointee>::Metadata`", - goal.predicate.self_ty() - ), - }; + } + } + ty::Adt(_, _) => tcx.types.unit, - 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) - }) + ty::Tuple(elements) => match elements.last() { + None => tcx.types.unit, + Some(&self_ty) => { + ecx.add_goal(goal.with( + tcx, + ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)), + )); + return ecx + .evaluate_added_goals_and_make_canonical_response(Certainty::Yes); + } + }, + + ty::Infer( + 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( @@ -548,11 +541,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { ), }; - ecx.probe(|r| CandidateKind::Candidate { - name: "builtin discriminant kind".into(), - result: *r, - }) - .enter(|ecx| { + ecx.probe_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) diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs index 18fec6d9c89..a2eb223bc26 100644 --- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs +++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs @@ -6,7 +6,6 @@ use rustc_hir::def_id::DefId; use rustc_hir::{LangItem, Movability}; use rustc_infer::traits::query::NoSolution; use rustc_infer::traits::util::supertraits; -use rustc_middle::traits::solve::inspect::CandidateKind; use rustc_middle::traits::solve::{CanonicalResponse, Certainty, Goal, QueryResult}; use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, TreatProjections}; use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt}; @@ -62,7 +61,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { }, }; - ecx.probe(|r| CandidateKind::Candidate { name: "impl".into(), result: *r }).enter(|ecx| { + ecx.probe_candidate("impl").enter(|ecx| { let impl_substs = ecx.fresh_substs_for_item(impl_def_id); let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs); @@ -90,16 +89,15 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { && trait_clause.polarity() == goal.predicate.polarity { // FIXME: Constness - ecx.probe(|r| CandidateKind::Candidate { name: "assumption".into(), result: *r }) - .enter(|ecx| { - let assumption_trait_pred = ecx.instantiate_binder_with_infer(trait_clause); - ecx.eq( - goal.param_env, - goal.predicate.trait_ref, - assumption_trait_pred.trait_ref, - )?; - then(ecx) - }) + ecx.probe_candidate("assumption").enter(|ecx| { + let assumption_trait_pred = ecx.instantiate_binder_with_infer(trait_clause); + ecx.eq( + goal.param_env, + goal.predicate.trait_ref, + assumption_trait_pred.trait_ref, + )?; + then(ecx) + }) } else { Err(NoSolution) } @@ -136,15 +134,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { let tcx = ecx.tcx(); - ecx.probe(|r| CandidateKind::Candidate { name: "trait alias".into(), result: *r }).enter( - |ecx| { - let nested_obligations = tcx - .predicates_of(goal.predicate.def_id()) - .instantiate(tcx, goal.predicate.trait_ref.substs); - ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p))); - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - }, - ) + ecx.probe_candidate("trait alias").enter(|ecx| { + let nested_obligations = tcx + .predicates_of(goal.predicate.def_id()) + .instantiate(tcx, goal.predicate.trait_ref.substs); + ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p))); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + }) } fn consider_builtin_sized_candidate( @@ -350,115 +346,109 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { if b_ty.is_ty_var() { return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS); } - ecx.probe(|r| CandidateKind::Candidate { name: "builtin unsize".into(), result: *r }).enter( - |ecx| { - match (a_ty.kind(), b_ty.kind()) { - // Trait upcasting, or `dyn Trait + Auto + 'a` -> `dyn Trait + 'b` - (&ty::Dynamic(_, _, ty::Dyn), &ty::Dynamic(_, _, ty::Dyn)) => { - // 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. - Err(NoSolution) + ecx.probe_candidate("builtin unsize").enter(|ecx| { + match (a_ty.kind(), b_ty.kind()) { + // Trait upcasting, or `dyn Trait + Auto + 'a` -> `dyn Trait + 'b` + (&ty::Dynamic(_, _, ty::Dyn), &ty::Dynamic(_, _, ty::Dyn)) => { + // 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. + Err(NoSolution) + } + // `T` -> `dyn Trait` unsizing + (_, &ty::Dynamic(data, region, ty::Dyn)) => { + // Can only unsize to an object-safe type + if data + .principal_def_id() + .is_some_and(|def_id| !tcx.check_is_object_safe(def_id)) + { + return Err(NoSolution); } - // `T` -> `dyn Trait` unsizing - (_, &ty::Dynamic(data, region, ty::Dyn)) => { - // Can only unsize to an object-safe type - if data - .principal_def_id() - .is_some_and(|def_id| !tcx.check_is_object_safe(def_id)) - { - return Err(NoSolution); - } - - let Some(sized_def_id) = tcx.lang_items().sized_trait() else { + + let Some(sized_def_id) = tcx.lang_items().sized_trait() else { return Err(NoSolution); }; - // 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) - ecx.add_goals( - data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))), - ); - // The type must be Sized to be unsized. - ecx.add_goal(goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty]))); - // The type must outlive the lifetime of the `dyn` we're unsizing into. - ecx.add_goal( - 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 - ecx.eq(goal.param_env, a_elem_ty, b_elem_ty)?; - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - } - // Struct unsizing `Struct<T>` -> `Struct<U>` where `T: Unsize<U>` - (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs)) - if a_def.is_struct() && a_def.did() == b_def.did() => - { - let unsizing_params = tcx.unsizing_params_for_adt(a_def.did()); - // We must be unsizing some type parameters. This also implies - // that the struct has a tail field. - if unsizing_params.is_empty() { - return Err(NoSolution); - } - - let tail_field = a_def - .non_enum_variant() - .fields - .raw - .last() - .expect("expected unsized ADT to have a tail field"); - let tail_field_ty = tcx.type_of(tail_field.did); - - let a_tail_ty = tail_field_ty.subst(tcx, a_substs); - let b_tail_ty = tail_field_ty.subst(tcx, b_substs); - - // Substitute just the unsizing params from B into A. The type after - // this substitution must be equal to B. This is so we don't unsize - // unrelated type parameters. - let new_a_substs = - tcx.mk_substs_from_iter(a_substs.iter().enumerate().map(|(i, a)| { - if unsizing_params.contains(i as u32) { b_substs[i] } else { a } - })); - let unsized_a_ty = tcx.mk_adt(a_def, new_a_substs); - - // Finally, we require that `TailA: Unsize<TailB>` for the tail field - // types. - ecx.eq(goal.param_env, unsized_a_ty, b_ty)?; - ecx.add_goal(goal.with( - tcx, - ty::TraitRef::new(tcx, goal.predicate.def_id(), [a_tail_ty, b_tail_ty]), - )); - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - } - // Tuple unsizing `(.., T)` -> `(.., U)` where `T: Unsize<U>` - (&ty::Tuple(a_tys), &ty::Tuple(b_tys)) - if a_tys.len() == b_tys.len() && !a_tys.is_empty() => - { - let (a_last_ty, a_rest_tys) = a_tys.split_last().unwrap(); - 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) + // 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) + ecx.add_goals( + data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))), + ); + // The type must be Sized to be unsized. + ecx.add_goal(goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty]))); + // The type must outlive the lifetime of the `dyn` we're unsizing into. + ecx.add_goal( + 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 + ecx.eq(goal.param_env, a_elem_ty, b_elem_ty)?; + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + } + // Struct unsizing `Struct<T>` -> `Struct<U>` where `T: Unsize<U>` + (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs)) + if a_def.is_struct() && a_def.did() == b_def.did() => + { + let unsizing_params = tcx.unsizing_params_for_adt(a_def.did()); + // We must be unsizing some type parameters. This also implies + // that the struct has a tail field. + if unsizing_params.is_empty() { + return Err(NoSolution); } - _ => Err(NoSolution), + + let tail_field = a_def + .non_enum_variant() + .fields + .raw + .last() + .expect("expected unsized ADT to have a tail field"); + let tail_field_ty = tcx.type_of(tail_field.did); + + let a_tail_ty = tail_field_ty.subst(tcx, a_substs); + let b_tail_ty = tail_field_ty.subst(tcx, b_substs); + + // Substitute just the unsizing params from B into A. The type after + // this substitution must be equal to B. This is so we don't unsize + // unrelated type parameters. + let new_a_substs = + tcx.mk_substs_from_iter(a_substs.iter().enumerate().map(|(i, a)| { + if unsizing_params.contains(i as u32) { b_substs[i] } else { a } + })); + let unsized_a_ty = tcx.mk_adt(a_def, new_a_substs); + + // Finally, we require that `TailA: Unsize<TailB>` for the tail field + // types. + ecx.eq(goal.param_env, unsized_a_ty, b_ty)?; + ecx.add_goal(goal.with( + tcx, + ty::TraitRef::new(tcx, goal.predicate.def_id(), [a_tail_ty, b_tail_ty]), + )); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) } - }, - ) + // Tuple unsizing `(.., T)` -> `(.., U)` where `T: Unsize<U>` + (&ty::Tuple(a_tys), &ty::Tuple(b_tys)) + if a_tys.len() == b_tys.len() && !a_tys.is_empty() => + { + let (a_last_ty, a_rest_tys) = a_tys.split_last().unwrap(); + 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), + } + }) } fn consider_builtin_dyn_upcast_candidates( @@ -488,11 +478,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { } let mut unsize_dyn_to_principal = |principal: Option<ty::PolyExistentialTraitRef<'tcx>>| { - ecx.probe(|r| CandidateKind::Candidate { - name: "upcast dyn to principle".into(), - result: *r, - }) - .enter(|ecx| -> Result<_, NoSolution> { + ecx.probe_candidate("upcast dyn to principle").enter(|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. @@ -714,21 +700,20 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { goal: Goal<'tcx, TraitPredicate<'tcx>>, constituent_tys: impl Fn(&EvalCtxt<'_, 'tcx>, Ty<'tcx>) -> Result<Vec<Ty<'tcx>>, NoSolution>, ) -> QueryResult<'tcx> { - self.probe(|r| CandidateKind::Candidate { name: "constituent tys".into(), result: *r }) - .enter(|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) - }) + self.probe_candidate("constituent tys").enter(|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) + }) } #[instrument(level = "debug", skip(self))] |