From db1cdd40f59dba43c3f742b1e65f693eda16fe28 Mon Sep 17 00:00:00 2001 From: lcnr Date: Tue, 22 Nov 2022 15:46:01 +0100 Subject: [PATCH 1/2] move 2 candidates into builtin candidate --- compiler/rustc_middle/src/traits/mod.rs | 23 -- compiler/rustc_middle/src/traits/select.rs | 6 - .../src/traits/structural_impls.rs | 12 - .../src/traits/project.rs | 333 +++++++++--------- .../src/traits/select/candidate_assembly.rs | 4 +- .../src/traits/select/confirmation.rs | 16 +- .../src/traits/select/mod.rs | 16 +- compiler/rustc_ty_utils/src/instance.rs | 2 - 8 files changed, 166 insertions(+), 246 deletions(-) diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs index 1890c0e24bb44..e436328709bb7 100644 --- a/compiler/rustc_middle/src/traits/mod.rs +++ b/compiler/rustc_middle/src/traits/mod.rs @@ -651,12 +651,6 @@ pub enum ImplSource<'tcx, N> { /// Same as above, but for a function pointer type with the given signature. FnPointer(ImplSourceFnPointerData<'tcx, N>), - /// ImplSource for a builtin `DeterminantKind` trait implementation. - DiscriminantKind(ImplSourceDiscriminantKindData), - - /// ImplSource for a builtin `Pointee` trait implementation. - Pointee(ImplSourcePointeeData), - /// ImplSource automatically generated for a generator. Generator(ImplSourceGeneratorData<'tcx, N>), @@ -678,8 +672,6 @@ impl<'tcx, N> ImplSource<'tcx, N> { ImplSource::Generator(c) => c.nested, ImplSource::Object(d) => d.nested, ImplSource::FnPointer(d) => d.nested, - ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) - | ImplSource::Pointee(ImplSourcePointeeData) => vec![], ImplSource::TraitAlias(d) => d.nested, ImplSource::TraitUpcasting(d) => d.nested, ImplSource::ConstDestruct(i) => i.nested, @@ -696,8 +688,6 @@ impl<'tcx, N> ImplSource<'tcx, N> { ImplSource::Generator(c) => &c.nested, ImplSource::Object(d) => &d.nested, ImplSource::FnPointer(d) => &d.nested, - ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) - | ImplSource::Pointee(ImplSourcePointeeData) => &[], ImplSource::TraitAlias(d) => &d.nested, ImplSource::TraitUpcasting(d) => &d.nested, ImplSource::ConstDestruct(i) => &i.nested, @@ -741,12 +731,6 @@ impl<'tcx, N> ImplSource<'tcx, N> { fn_ty: p.fn_ty, nested: p.nested.into_iter().map(f).collect(), }), - ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) => { - ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) - } - ImplSource::Pointee(ImplSourcePointeeData) => { - ImplSource::Pointee(ImplSourcePointeeData) - } ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData { alias_def_id: d.alias_def_id, substs: d.substs, @@ -856,13 +840,6 @@ pub struct ImplSourceFnPointerData<'tcx, N> { pub nested: Vec, } -// FIXME(@lcnr): This should be refactored and merged with other builtin vtables. -#[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)] -pub struct ImplSourceDiscriminantKindData; - -#[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)] -pub struct ImplSourcePointeeData; - #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)] #[derive(TypeFoldable, TypeVisitable)] pub struct ImplSourceConstDestructData { diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs index 85ead3171e785..d210d5c3dc4f0 100644 --- a/compiler/rustc_middle/src/traits/select.rs +++ b/compiler/rustc_middle/src/traits/select.rs @@ -137,12 +137,6 @@ pub enum SelectionCandidate<'tcx> { is_const: bool, }, - /// Builtin implementation of `DiscriminantKind`. - DiscriminantKindCandidate, - - /// Builtin implementation of `Pointee`. - PointeeCandidate, - TraitAliasCandidate, /// Matching `dyn Trait` with a supertrait of `Trait`. The index is the diff --git a/compiler/rustc_middle/src/traits/structural_impls.rs b/compiler/rustc_middle/src/traits/structural_impls.rs index 7fbd57ac7354a..4937c6b7dc514 100644 --- a/compiler/rustc_middle/src/traits/structural_impls.rs +++ b/compiler/rustc_middle/src/traits/structural_impls.rs @@ -17,10 +17,6 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSource<'tcx, N> { super::ImplSource::FnPointer(ref d) => write!(f, "({:?})", d), - super::ImplSource::DiscriminantKind(ref d) => write!(f, "{:?}", d), - - super::ImplSource::Pointee(ref d) => write!(f, "{:?}", d), - super::ImplSource::Object(ref d) => write!(f, "{:?}", d), super::ImplSource::Param(ref n, ct) => { @@ -125,11 +121,3 @@ impl fmt::Debug for traits::ImplSourceConstDestructData { write!(f, "ImplSourceConstDestructData(nested={:?})", self.nested) } } - -/////////////////////////////////////////////////////////////////////////// -// Lift implementations - -TrivialTypeTraversalAndLiftImpls! { - super::ImplSourceDiscriminantKindData, - super::ImplSourcePointeeData, -} diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs index 9f19b0092c00f..9aab28f494476 100644 --- a/compiler/rustc_trait_selection/src/traits/project.rs +++ b/compiler/rustc_trait_selection/src/traits/project.rs @@ -11,8 +11,8 @@ use super::Selection; use super::SelectionContext; use super::SelectionError; use super::{ - ImplSourceClosureData, ImplSourceDiscriminantKindData, ImplSourceFnPointerData, - ImplSourceGeneratorData, ImplSourcePointeeData, ImplSourceUserDefinedData, + ImplSourceClosureData, ImplSourceFnPointerData, ImplSourceGeneratorData, + ImplSourceUserDefinedData, }; use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey}; @@ -28,6 +28,7 @@ use rustc_hir::def::DefKind; use rustc_hir::def_id::DefId; use rustc_hir::lang_items::LangItem; use rustc_infer::infer::resolve::OpportunisticRegionResolver; +use rustc_infer::traits::ImplSourceBuiltinData; use rustc_middle::traits::select::OverflowError; use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable}; use rustc_middle::ty::visit::{MaxUniverse, TypeVisitable}; @@ -1612,128 +1613,126 @@ fn assemble_candidates_from_impls<'cx, 'tcx>( } } } - super::ImplSource::DiscriminantKind(..) => { - // While `DiscriminantKind` is automatically implemented for every type, - // the concrete discriminant may not be known yet. - // - // Any type with multiple potential discriminant types is therefore not eligible. + super::ImplSource::Builtin(..) => { + // While a builtin impl may be known to exist, the associated type may not yet + // be known. Any type with multiple potential associated types is therefore + // not eligible. let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); - match self_ty.kind() { - ty::Bool - | ty::Char - | ty::Int(_) - | ty::Uint(_) - | ty::Float(_) - | ty::Adt(..) - | ty::Foreign(_) - | ty::Str - | ty::Array(..) - | ty::Slice(_) - | ty::RawPtr(..) - | ty::Ref(..) - | ty::FnDef(..) - | ty::FnPtr(..) - | ty::Dynamic(..) - | ty::Closure(..) - | ty::Generator(..) - | ty::GeneratorWitness(..) - | ty::Never - | ty::Tuple(..) - // Integers and floats always have `u8` as their discriminant. - | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true, - - ty::Projection(..) - | ty::Opaque(..) - | ty::Param(..) - | ty::Bound(..) - | ty::Placeholder(..) - | ty::Infer(..) - | ty::Error(_) => false, - } - } - super::ImplSource::Pointee(..) => { - // While `Pointee` is automatically implemented for every type, - // the concrete metadata type may not be known yet. - // - // Any type with multiple potential metadata types is therefore not eligible. - let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); - - let tail = selcx.tcx().struct_tail_with_normalize( - self_ty, - |ty| { - // We throw away any obligations we get from this, since we normalize - // and confirm these obligations once again during confirmation - normalize_with_depth( - selcx, - obligation.param_env, - obligation.cause.clone(), - obligation.recursion_depth + 1, - ty, - ) - .value - }, - || {}, - ); - - match tail.kind() { - 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::Dynamic(..) - | ty::Closure(..) - | ty::Generator(..) - | ty::GeneratorWitness(..) - | ty::Never - // Extern types have unit metadata, according to RFC 2850 - | ty::Foreign(_) - // If returned by `struct_tail_without_normalization` this is a unit struct - // without any fields, or not a struct, and therefore is Sized. - | ty::Adt(..) - // If returned by `struct_tail_without_normalization` this is the empty tuple. - | ty::Tuple(..) - // Integers and floats are always Sized, and so have unit type metadata. - | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true, - - // type parameters, opaques, and unnormalized projections have pointer - // metadata if they're known (e.g. by the param_env) to be sized - ty::Param(_) | ty::Projection(..) | ty::Opaque(..) - if selcx.infcx().predicate_must_hold_modulo_regions( - &obligation.with( - selcx.tcx(), - ty::Binder::dummy(selcx.tcx().at(obligation.cause.span).mk_trait_ref( - LangItem::Sized, - [self_ty], - )) - .without_const(), - ), - ) => - { - true + let lang_items = selcx.tcx().lang_items(); + if lang_items.discriminant_kind_trait() == Some(poly_trait_ref.def_id()) { + match self_ty.kind() { + ty::Bool + | ty::Char + | ty::Int(_) + | ty::Uint(_) + | ty::Float(_) + | ty::Adt(..) + | ty::Foreign(_) + | ty::Str + | ty::Array(..) + | ty::Slice(_) + | ty::RawPtr(..) + | ty::Ref(..) + | ty::FnDef(..) + | ty::FnPtr(..) + | ty::Dynamic(..) + | ty::Closure(..) + | ty::Generator(..) + | ty::GeneratorWitness(..) + | ty::Never + | ty::Tuple(..) + // Integers and floats always have `u8` as their discriminant. + | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true, + + // type parameters, opaques, and unnormalized projections have pointer + // metadata if they're known (e.g. by the param_env) to be sized + ty::Param(_) + | ty::Projection(..) + | ty::Opaque(..) + | ty::Bound(..) + | ty::Placeholder(..) + | ty::Infer(..) + | ty::Error(_) => false, } + } else if lang_items.pointee_trait() == Some(poly_trait_ref.def_id()) { + let tail = selcx.tcx().struct_tail_with_normalize( + self_ty, + |ty| { + // We throw away any obligations we get from this, since we normalize + // and confirm these obligations once again during confirmation + normalize_with_depth( + selcx, + obligation.param_env, + obligation.cause.clone(), + obligation.recursion_depth + 1, + ty, + ) + .value + }, + || {}, + ); - // FIXME(compiler-errors): are Bound and Placeholder types ever known sized? - ty::Param(_) - | ty::Projection(..) - | ty::Opaque(..) - | ty::Bound(..) - | ty::Placeholder(..) - | ty::Infer(..) - | ty::Error(_) => { - if tail.has_infer_types() { - candidate_set.mark_ambiguous(); + match tail.kind() { + 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::Dynamic(..) + | ty::Closure(..) + | ty::Generator(..) + | ty::GeneratorWitness(..) + | ty::Never + // Extern types have unit metadata, according to RFC 2850 + | ty::Foreign(_) + // If returned by `struct_tail_without_normalization` this is a unit struct + // without any fields, or not a struct, and therefore is Sized. + | ty::Adt(..) + // If returned by `struct_tail_without_normalization` this is the empty tuple. + | ty::Tuple(..) + // Integers and floats are always Sized, and so have unit type metadata. + | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true, + + // type parameters, opaques, and unnormalized projections have pointer + // metadata if they're known (e.g. by the param_env) to be sized + ty::Param(_) | ty::Projection(..) | ty::Opaque(..) + if selcx.infcx().predicate_must_hold_modulo_regions( + &obligation.with( + selcx.tcx(), + ty::Binder::dummy( + selcx.tcx().at(obligation.cause.span()).mk_trait_ref(LangItem::Sized, [self_ty]), + ) + .without_const(), + ), + ) => + { + true + } + + // FIXME(compiler-errors): are Bound and Placeholder types ever known sized? + ty::Param(_) + | ty::Projection(..) + | ty::Opaque(..) + | ty::Bound(..) + | ty::Placeholder(..) + | ty::Infer(..) + | ty::Error(_) => { + if tail.has_infer_types() { + candidate_set.mark_ambiguous(); + } + false } - false } + } else { + bug!("unexpected builtin trait with associated type: {poly_trait_ref:?}") } } super::ImplSource::Param(..) => { @@ -1771,7 +1770,6 @@ fn assemble_candidates_from_impls<'cx, 'tcx>( false } super::ImplSource::AutoImpl(..) - | super::ImplSource::Builtin(..) | super::ImplSource::TraitUpcasting(_) | super::ImplSource::ConstDestruct(_) => { // These traits have no associated types. @@ -1850,14 +1848,10 @@ fn confirm_select_candidate<'cx, 'tcx>( super::ImplSource::Generator(data) => confirm_generator_candidate(selcx, obligation, data), super::ImplSource::Closure(data) => confirm_closure_candidate(selcx, obligation, data), super::ImplSource::FnPointer(data) => confirm_fn_pointer_candidate(selcx, obligation, data), - super::ImplSource::DiscriminantKind(data) => { - confirm_discriminant_kind_candidate(selcx, obligation, data) - } - super::ImplSource::Pointee(data) => confirm_pointee_candidate(selcx, obligation, data), + super::ImplSource::Builtin(data) => confirm_builtin_candidate(selcx, obligation, data), super::ImplSource::Object(_) | super::ImplSource::AutoImpl(..) | super::ImplSource::Param(..) - | super::ImplSource::Builtin(..) | super::ImplSource::TraitUpcasting(_) | super::ImplSource::TraitAlias(..) | super::ImplSource::ConstDestruct(_) => { @@ -1921,68 +1915,55 @@ fn confirm_generator_candidate<'cx, 'tcx>( .with_addl_obligations(obligations) } -fn confirm_discriminant_kind_candidate<'cx, 'tcx>( +fn confirm_builtin_candidate<'cx, 'tcx>( selcx: &mut SelectionContext<'cx, 'tcx>, obligation: &ProjectionTyObligation<'tcx>, - _: ImplSourceDiscriminantKindData, + data: ImplSourceBuiltinData>, ) -> Progress<'tcx> { let tcx = selcx.tcx(); - - let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); - // We get here from `poly_project_and_unify_type` which replaces bound vars - // with placeholders - debug_assert!(!self_ty.has_escaping_bound_vars()); + let self_ty = obligation.predicate.self_ty(); let substs = tcx.mk_substs([self_ty.into()].iter()); - - let discriminant_def_id = tcx.require_lang_item(LangItem::Discriminant, None); - - let predicate = ty::ProjectionPredicate { - projection_ty: ty::ProjectionTy { substs, item_def_id: discriminant_def_id }, - term: self_ty.discriminant_ty(tcx).into(), + let lang_items = tcx.lang_items(); + let item_def_id = obligation.predicate.item_def_id; + let trait_def_id = tcx.trait_of_item(item_def_id).unwrap(); + let (term, obligations) = if lang_items.discriminant_kind_trait() == Some(trait_def_id) { + let discriminant_def_id = tcx.require_lang_item(LangItem::Discriminant, None); + assert_eq!(discriminant_def_id, item_def_id); + + (self_ty.discriminant_ty(tcx).into(), Vec::new()) + } else if lang_items.pointee_trait() == Some(trait_def_id) { + let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, None); + assert_eq!(metadata_def_id, item_def_id); + + let mut obligations = Vec::new(); + let (metadata_ty, check_is_sized) = self_ty.ptr_metadata_ty(tcx, |ty| { + normalize_with_depth_to( + selcx, + obligation.param_env, + obligation.cause.clone(), + obligation.recursion_depth + 1, + ty, + &mut obligations, + ) + }); + if check_is_sized { + let sized_predicate = ty::Binder::dummy( + tcx.at(obligation.cause.span()).mk_trait_ref(LangItem::Sized, [self_ty]), + ) + .without_const(); + obligations.push(obligation.with(tcx, sized_predicate)); + } + (metadata_ty.into(), obligations) + } else { + bug!("unexpected builtin trait with associated type: {:?}", obligation.predicate); }; - // We get here from `poly_project_and_unify_type` which replaces bound vars - // with placeholders, so dummy is okay here. - confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false) -} - -fn confirm_pointee_candidate<'cx, 'tcx>( - selcx: &mut SelectionContext<'cx, 'tcx>, - obligation: &ProjectionTyObligation<'tcx>, - _: ImplSourcePointeeData, -) -> Progress<'tcx> { - let tcx = selcx.tcx(); - let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); - - let mut obligations = vec![]; - let (metadata_ty, check_is_sized) = self_ty.ptr_metadata_ty(tcx, |ty| { - normalize_with_depth_to( - selcx, - obligation.param_env, - obligation.cause.clone(), - obligation.recursion_depth + 1, - ty, - &mut obligations, - ) - }); - if check_is_sized { - let sized_predicate = ty::Binder::dummy( - tcx.at(obligation.cause.span).mk_trait_ref(LangItem::Sized, [self_ty]), - ) - .without_const(); - obligations.push(obligation.with(tcx, sized_predicate)); - } - - let substs = tcx.mk_substs([self_ty.into()].iter()); - let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, Some(obligation.cause.span)); - - let predicate = ty::ProjectionPredicate { - projection_ty: ty::ProjectionTy { substs, item_def_id: metadata_def_id }, - term: metadata_ty.into(), - }; + let predicate = + ty::ProjectionPredicate { projection_ty: ty::ProjectionTy { substs, item_def_id }, term }; confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false) .with_addl_obligations(obligations) + .with_addl_obligations(data.nested) } fn confirm_fn_pointer_candidate<'cx, 'tcx>( diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs index 3b107d9570f14..5bc402dcaa41f 100644 --- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs +++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs @@ -284,10 +284,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { self.assemble_builtin_bound_candidates(copy_conditions, &mut candidates); } else if lang_items.discriminant_kind_trait() == Some(def_id) { // `DiscriminantKind` is automatically implemented for every type. - candidates.vec.push(DiscriminantKindCandidate); + candidates.vec.push(BuiltinCandidate { has_nested: false }); } else if lang_items.pointee_trait() == Some(def_id) { // `Pointee` is automatically implemented for every type. - candidates.vec.push(PointeeCandidate); + candidates.vec.push(BuiltinCandidate { has_nested: false }); } else if lang_items.sized_trait() == Some(def_id) { // Sized is never implementable by end-users, it is // always automatically computed. diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs index 2ec5d925b6900..5edff1463f4f9 100644 --- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs +++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs @@ -22,11 +22,11 @@ use crate::traits::util::{self, closure_trait_ref_and_return_type, predicate_for use crate::traits::{ BuiltinDerivedObligation, ImplDerivedObligation, ImplDerivedObligationCause, ImplSource, ImplSourceAutoImplData, ImplSourceBuiltinData, ImplSourceClosureData, - ImplSourceConstDestructData, ImplSourceDiscriminantKindData, ImplSourceFnPointerData, - ImplSourceGeneratorData, ImplSourceObjectData, ImplSourcePointeeData, ImplSourceTraitAliasData, - ImplSourceTraitUpcastingData, ImplSourceUserDefinedData, Normalized, ObjectCastObligation, - Obligation, ObligationCause, OutputTypeParameterMismatch, PredicateObligation, Selection, - SelectionError, TraitNotObjectSafe, TraitObligation, Unimplemented, VtblSegment, + ImplSourceConstDestructData, ImplSourceFnPointerData, ImplSourceGeneratorData, + ImplSourceObjectData, ImplSourceTraitAliasData, ImplSourceTraitUpcastingData, + ImplSourceUserDefinedData, Normalized, ObjectCastObligation, Obligation, ObligationCause, + OutputTypeParameterMismatch, PredicateObligation, Selection, SelectionError, + TraitNotObjectSafe, TraitObligation, Unimplemented, VtblSegment, }; use super::BuiltinImplConditions; @@ -94,12 +94,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { ImplSource::FnPointer(data) } - DiscriminantKindCandidate => { - ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) - } - - PointeeCandidate => ImplSource::Pointee(ImplSourcePointeeData), - TraitAliasCandidate => { let data = self.confirm_trait_alias_candidate(obligation); ImplSource::TraitAlias(data) diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs index e54e290fb4b11..df25beffd79dd 100644 --- a/compiler/rustc_trait_selection/src/traits/select/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs @@ -1591,20 +1591,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { (TransmutabilityCandidate, _) | (_, TransmutabilityCandidate) => false, // (*) - ( - BuiltinCandidate { has_nested: false } - | DiscriminantKindCandidate - | PointeeCandidate - | ConstDestructCandidate(_), - _, - ) => true, - ( - _, - BuiltinCandidate { has_nested: false } - | DiscriminantKindCandidate - | PointeeCandidate - | ConstDestructCandidate(_), - ) => false, + (BuiltinCandidate { has_nested: false } | ConstDestructCandidate(_), _) => true, + (_, BuiltinCandidate { has_nested: false } | ConstDestructCandidate(_)) => false, (ParamCandidate(other), ParamCandidate(victim)) => { let same_except_bound_vars = other.skip_binder().trait_ref diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs index 6436713b38811..469108345b1d8 100644 --- a/compiler/rustc_ty_utils/src/instance.rs +++ b/compiler/rustc_ty_utils/src/instance.rs @@ -264,8 +264,6 @@ fn resolve_associated_item<'tcx>( traits::ImplSource::AutoImpl(..) | traits::ImplSource::Param(..) | traits::ImplSource::TraitAlias(..) - | traits::ImplSource::DiscriminantKind(..) - | traits::ImplSource::Pointee(..) | traits::ImplSource::TraitUpcasting(_) | traits::ImplSource::ConstDestruct(_) => None, }) From f995583aa5f2f2d5891068aa9374c455a1f730e2 Mon Sep 17 00:00:00 2001 From: lcnr Date: Wed, 23 Nov 2022 17:39:51 +0100 Subject: [PATCH 2/2] add comment --- compiler/rustc_middle/src/traits/select.rs | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs index d210d5c3dc4f0..51ae245900822 100644 --- a/compiler/rustc_middle/src/traits/select.rs +++ b/compiler/rustc_middle/src/traits/select.rs @@ -105,6 +105,12 @@ pub type EvaluationCache<'tcx> = Cache< /// parameter environment. #[derive(PartialEq, Eq, Debug, Clone, TypeFoldable, TypeVisitable)] pub enum SelectionCandidate<'tcx> { + /// A builtin implementation for some specific traits, used in cases + /// where we cannot rely an ordinary library implementations. + /// + /// The most notable examples are `sized`, `Copy` and `Clone`. This is also + /// used for the `DiscriminantKind` and `Pointee` trait, both of which have + /// an associated type. BuiltinCandidate { /// `false` if there are no *further* obligations. has_nested: bool,