diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_ast_lowering/messages.ftl | 3 | ||||
| -rw-r--r-- | compiler/rustc_ast_lowering/src/errors.rs | 7 | ||||
| -rw-r--r-- | compiler/rustc_ast_lowering/src/item.rs | 112 | ||||
| -rw-r--r-- | compiler/rustc_ast_lowering/src/lib.rs | 142 | ||||
| -rw-r--r-- | compiler/rustc_ast_passes/messages.ftl | 5 | ||||
| -rw-r--r-- | compiler/rustc_ast_passes/src/ast_validation.rs | 23 | ||||
| -rw-r--r-- | compiler/rustc_ast_passes/src/errors.rs | 16 | ||||
| -rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0203.md | 10 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/messages.ftl | 5 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/src/collect/predicates_of.rs | 16 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/src/errors.rs | 14 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs | 69 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs | 33 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs | 69 | ||||
| -rw-r--r-- | compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs | 62 |
15 files changed, 270 insertions, 316 deletions
diff --git a/compiler/rustc_ast_lowering/messages.ftl b/compiler/rustc_ast_lowering/messages.ftl index c6472fd45fa..370b15d2871 100644 --- a/compiler/rustc_ast_lowering/messages.ftl +++ b/compiler/rustc_ast_lowering/messages.ftl @@ -127,9 +127,6 @@ ast_lowering_misplaced_impl_trait = `impl Trait` is not allowed in {$position} .note = `impl Trait` is only allowed in arguments and return types of functions and methods -ast_lowering_misplaced_relax_trait_bound = - `?Trait` bounds are only permitted at the point where a type parameter is declared - ast_lowering_never_pattern_with_body = a never pattern is always unreachable .label = this will never be executed diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs index b444324ef91..83f3a976e83 100644 --- a/compiler/rustc_ast_lowering/src/errors.rs +++ b/compiler/rustc_ast_lowering/src/errors.rs @@ -325,13 +325,6 @@ pub(crate) struct MisplacedDoubleDot { } #[derive(Diagnostic)] -#[diag(ast_lowering_misplaced_relax_trait_bound)] -pub(crate) struct MisplacedRelaxTraitBound { - #[primary_span] - pub span: Span, -} - -#[derive(Diagnostic)] #[diag(ast_lowering_match_arm_with_no_body)] pub(crate) struct MatchArmWithNoBody { #[primary_span] diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs index abd70c7517c..ddf01b69e7f 100644 --- a/compiler/rustc_ast_lowering/src/item.rs +++ b/compiler/rustc_ast_lowering/src/item.rs @@ -16,14 +16,11 @@ use smallvec::{SmallVec, smallvec}; use thin_vec::ThinVec; use tracing::instrument; -use super::errors::{ - InvalidAbi, InvalidAbiSuggestion, MisplacedRelaxTraitBound, TupleStructWithDefault, - UnionWithDefault, -}; +use super::errors::{InvalidAbi, InvalidAbiSuggestion, TupleStructWithDefault, UnionWithDefault}; use super::stability::{enabled_names, gate_unstable_abi}; use super::{ AstOwner, FnDeclKind, ImplTraitContext, ImplTraitPosition, LoweringContext, ParamMode, - ResolverAstLoweringExt, + RelaxedBoundForbiddenReason, RelaxedBoundPolicy, ResolverAstLoweringExt, }; pub(super) struct ItemLowerer<'a, 'hir> { @@ -435,6 +432,7 @@ impl<'hir> LoweringContext<'_, 'hir> { |this| { let bounds = this.lower_param_bounds( bounds, + RelaxedBoundPolicy::Forbidden(RelaxedBoundForbiddenReason::SuperTrait), ImplTraitContext::Disallowed(ImplTraitPosition::Bound), ); let items = this.arena.alloc_from_iter( @@ -455,6 +453,7 @@ impl<'hir> LoweringContext<'_, 'hir> { |this| { this.lower_param_bounds( bounds, + RelaxedBoundPolicy::Allowed, ImplTraitContext::Disallowed(ImplTraitPosition::Bound), ) }, @@ -940,6 +939,7 @@ impl<'hir> LoweringContext<'_, 'hir> { hir::TraitItemKind::Type( this.lower_param_bounds( bounds, + RelaxedBoundPolicy::Allowed, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), ), ty, @@ -1677,61 +1677,6 @@ impl<'hir> LoweringContext<'_, 'hir> { assert!(self.impl_trait_defs.is_empty()); assert!(self.impl_trait_bounds.is_empty()); - // Error if `?Trait` bounds in where clauses don't refer directly to type parameters. - // Note: we used to clone these bounds directly onto the type parameter (and avoid lowering - // these into hir when we lower thee where clauses), but this makes it quite difficult to - // keep track of the Span info. Now, `<dyn HirTyLowerer>::add_implicit_sized_bound` - // checks both param bounds and where clauses for `?Sized`. - for pred in &generics.where_clause.predicates { - let WherePredicateKind::BoundPredicate(bound_pred) = &pred.kind else { - continue; - }; - let compute_is_param = || { - // Check if the where clause type is a plain type parameter. - match self - .resolver - .get_partial_res(bound_pred.bounded_ty.id) - .and_then(|r| r.full_res()) - { - Some(Res::Def(DefKind::TyParam, def_id)) - if bound_pred.bound_generic_params.is_empty() => - { - generics - .params - .iter() - .any(|p| def_id == self.local_def_id(p.id).to_def_id()) - } - // Either the `bounded_ty` is not a plain type parameter, or - // it's not found in the generic type parameters list. - _ => false, - } - }; - // We only need to compute this once per `WherePredicate`, but don't - // need to compute this at all unless there is a Maybe bound. - let mut is_param: Option<bool> = None; - for bound in &bound_pred.bounds { - if !matches!( - *bound, - GenericBound::Trait(PolyTraitRef { - modifiers: TraitBoundModifiers { polarity: BoundPolarity::Maybe(_), .. }, - .. - }) - ) { - continue; - } - let is_param = *is_param.get_or_insert_with(compute_is_param); - if !is_param && !self.tcx.features().more_maybe_bounds() { - self.tcx - .sess - .create_feature_err( - MisplacedRelaxTraitBound { span: bound.span() }, - sym::more_maybe_bounds, - ) - .emit(); - } - } - } - let mut predicates: SmallVec<[hir::WherePredicate<'hir>; 4]> = SmallVec::new(); predicates.extend(generics.params.iter().filter_map(|param| { self.lower_generic_bound_predicate( @@ -1741,6 +1686,7 @@ impl<'hir> LoweringContext<'_, 'hir> { ¶m.bounds, param.colon_span, generics.span, + RelaxedBoundPolicy::Allowed, itctx, PredicateOrigin::GenericParam, ) @@ -1750,7 +1696,7 @@ impl<'hir> LoweringContext<'_, 'hir> { .where_clause .predicates .iter() - .map(|predicate| self.lower_where_predicate(predicate)), + .map(|predicate| self.lower_where_predicate(predicate, &generics.params)), ); let mut params: SmallVec<[hir::GenericParam<'hir>; 4]> = self @@ -1827,6 +1773,7 @@ impl<'hir> LoweringContext<'_, 'hir> { bounds: &[GenericBound], colon_span: Option<Span>, parent_span: Span, + rbp: RelaxedBoundPolicy<'_>, itctx: ImplTraitContext, origin: PredicateOrigin, ) -> Option<hir::WherePredicate<'hir>> { @@ -1835,7 +1782,7 @@ impl<'hir> LoweringContext<'_, 'hir> { return None; } - let bounds = self.lower_param_bounds(bounds, itctx); + let bounds = self.lower_param_bounds(bounds, rbp, itctx); let param_span = ident.span; @@ -1887,7 +1834,11 @@ impl<'hir> LoweringContext<'_, 'hir> { Some(hir::WherePredicate { hir_id, span, kind }) } - fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> { + fn lower_where_predicate( + &mut self, + pred: &WherePredicate, + params: &[ast::GenericParam], + ) -> hir::WherePredicate<'hir> { let hir_id = self.lower_node_id(pred.id); let span = self.lower_span(pred.span); self.lower_attrs(hir_id, &pred.attrs, span); @@ -1896,17 +1847,29 @@ impl<'hir> LoweringContext<'_, 'hir> { bound_generic_params, bounded_ty, bounds, - }) => hir::WherePredicateKind::BoundPredicate(hir::WhereBoundPredicate { - bound_generic_params: self - .lower_generic_params(bound_generic_params, hir::GenericParamSource::Binder), - bounded_ty: self - .lower_ty(bounded_ty, ImplTraitContext::Disallowed(ImplTraitPosition::Bound)), - bounds: self.lower_param_bounds( - bounds, - ImplTraitContext::Disallowed(ImplTraitPosition::Bound), - ), - origin: PredicateOrigin::WhereClause, - }), + }) => { + let rbp = if bound_generic_params.is_empty() { + RelaxedBoundPolicy::AllowedIfOnTyParam(bounded_ty.id, params) + } else { + RelaxedBoundPolicy::Forbidden(RelaxedBoundForbiddenReason::LateBoundVarsInScope) + }; + hir::WherePredicateKind::BoundPredicate(hir::WhereBoundPredicate { + bound_generic_params: self.lower_generic_params( + bound_generic_params, + hir::GenericParamSource::Binder, + ), + bounded_ty: self.lower_ty( + bounded_ty, + ImplTraitContext::Disallowed(ImplTraitPosition::Bound), + ), + bounds: self.lower_param_bounds( + bounds, + rbp, + ImplTraitContext::Disallowed(ImplTraitPosition::Bound), + ), + origin: PredicateOrigin::WhereClause, + }) + } WherePredicateKind::RegionPredicate(WhereRegionPredicate { lifetime, bounds }) => { hir::WherePredicateKind::RegionPredicate(hir::WhereRegionPredicate { lifetime: self.lower_lifetime( @@ -1916,6 +1879,7 @@ impl<'hir> LoweringContext<'_, 'hir> { ), bounds: self.lower_param_bounds( bounds, + RelaxedBoundPolicy::Allowed, ImplTraitContext::Disallowed(ImplTraitPosition::Bound), ), in_where_clause: true, diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs index 1c96a375035..533ee9bff54 100644 --- a/compiler/rustc_ast_lowering/src/lib.rs +++ b/compiler/rustc_ast_lowering/src/lib.rs @@ -53,8 +53,8 @@ use rustc_hir::def::{DefKind, LifetimeRes, Namespace, PartialRes, PerNS, Res}; use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId}; use rustc_hir::lints::DelayedLint; use rustc_hir::{ - self as hir, AngleBrackets, ConstArg, GenericArg, HirId, ItemLocalMap, LangItem, - LifetimeSource, LifetimeSyntax, ParamName, TraitCandidate, + self as hir, AngleBrackets, ConstArg, GenericArg, HirId, ItemLocalMap, LifetimeSource, + LifetimeSyntax, ParamName, TraitCandidate, }; use rustc_index::{Idx, IndexSlice, IndexVec}; use rustc_macros::extension; @@ -281,6 +281,24 @@ impl ResolverAstLowering { } } +/// How relaxed bounds `?Trait` should be treated. +/// +/// Relaxed bounds should only be allowed in places where we later +/// (namely during HIR ty lowering) perform *sized elaboration*. +#[derive(Clone, Copy, Debug)] +enum RelaxedBoundPolicy<'a> { + Allowed, + AllowedIfOnTyParam(NodeId, &'a [ast::GenericParam]), + Forbidden(RelaxedBoundForbiddenReason), +} + +#[derive(Clone, Copy, Debug)] +enum RelaxedBoundForbiddenReason { + TraitObjectTy, + SuperTrait, + LateBoundVarsInScope, +} + /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree, /// and if so, what meaning it has. #[derive(Debug, Copy, Clone, PartialEq, Eq)] @@ -1084,10 +1102,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { &*self.arena.alloc(self.ty(constraint.span, hir::TyKind::Err(guar))); hir::AssocItemConstraintKind::Equality { term: err_ty.into() } } else { - // Desugar `AssocTy: Bounds` into an assoc type binding where the - // later desugars into a trait predicate. - let bounds = self.lower_param_bounds(bounds, itctx); - + // FIXME(#135229): These should be forbidden! + let bounds = + self.lower_param_bounds(bounds, RelaxedBoundPolicy::Allowed, itctx); hir::AssocItemConstraintKind::Bound { bounds } } } @@ -1216,6 +1233,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { span: t.span, parens: ast::Parens::No, }, + RelaxedBoundPolicy::Forbidden(RelaxedBoundForbiddenReason::TraitObjectTy), itctx, ); let bounds = this.arena.alloc_from_iter([bound]); @@ -1271,7 +1289,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { parenthesized: hir::GenericArgsParentheses::No, span_ext: span, }); - let path = self.make_lang_item_qpath(LangItem::Pin, span, Some(args)); + let path = self.make_lang_item_qpath(hir::LangItem::Pin, span, Some(args)); hir::TyKind::Path(path) } TyKind::FnPtr(f) => { @@ -1332,7 +1350,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { // takes care of rejecting invalid modifier combinations and // const trait bounds in trait object types. GenericBound::Trait(ty) => { - let trait_ref = this.lower_poly_trait_ref(ty, itctx); + let trait_ref = this.lower_poly_trait_ref( + ty, + RelaxedBoundPolicy::Forbidden( + RelaxedBoundForbiddenReason::TraitObjectTy, + ), + itctx, + ); Some(trait_ref) } GenericBound::Outlives(lifetime) => { @@ -1387,9 +1411,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { } path } - ImplTraitContext::InBinding => { - hir::TyKind::TraitAscription(self.lower_param_bounds(bounds, itctx)) - } + ImplTraitContext::InBinding => hir::TyKind::TraitAscription( + self.lower_param_bounds(bounds, RelaxedBoundPolicy::Allowed, itctx), + ), ImplTraitContext::FeatureGated(position, feature) => { let guar = self .tcx @@ -1505,7 +1529,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None); self.lower_opaque_inner(opaque_ty_node_id, origin, opaque_ty_span, |this| { - this.lower_param_bounds(bounds, itctx) + this.lower_param_bounds(bounds, RelaxedBoundPolicy::Allowed, itctx) }) } @@ -1799,10 +1823,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { fn lower_param_bound( &mut self, tpb: &GenericBound, + rbp: RelaxedBoundPolicy<'_>, itctx: ImplTraitContext, ) -> hir::GenericBound<'hir> { match tpb { - GenericBound::Trait(p) => hir::GenericBound::Trait(self.lower_poly_trait_ref(p, itctx)), + GenericBound::Trait(p) => { + hir::GenericBound::Trait(self.lower_poly_trait_ref(p, rbp, itctx)) + } GenericBound::Outlives(lifetime) => hir::GenericBound::Outlives(self.lower_lifetime( lifetime, LifetimeSource::OutlivesBound, @@ -2017,19 +2044,91 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { #[instrument(level = "debug", skip(self))] fn lower_poly_trait_ref( &mut self, - p: &PolyTraitRef, + PolyTraitRef { bound_generic_params, modifiers, trait_ref, span, parens: _ }: &PolyTraitRef, + rbp: RelaxedBoundPolicy<'_>, itctx: ImplTraitContext, ) -> hir::PolyTraitRef<'hir> { let bound_generic_params = - self.lower_lifetime_binder(p.trait_ref.ref_id, &p.bound_generic_params); - let trait_ref = self.lower_trait_ref(p.modifiers, &p.trait_ref, itctx); - let modifiers = self.lower_trait_bound_modifiers(p.modifiers); + self.lower_lifetime_binder(trait_ref.ref_id, bound_generic_params); + let trait_ref = self.lower_trait_ref(*modifiers, trait_ref, itctx); + let modifiers = self.lower_trait_bound_modifiers(*modifiers); + + if let ast::BoundPolarity::Maybe(_) = modifiers.polarity { + self.validate_relaxed_bound(trait_ref, *span, rbp); + } + hir::PolyTraitRef { bound_generic_params, modifiers, trait_ref, - span: self.lower_span(p.span), + span: self.lower_span(*span), + } + } + + fn validate_relaxed_bound( + &self, + trait_ref: hir::TraitRef<'_>, + span: Span, + rbp: RelaxedBoundPolicy<'_>, + ) { + // Even though feature `more_maybe_bounds` bypasses the given policy and (currently) enables + // relaxed bounds in every conceivable position[^1], we don't want to advertise it to the user + // (via a feature gate) since it's super internal. Besides this, it'd be quite distracting. + // + // [^1]: Strictly speaking, this is incorrect (at the very least for `Sized`) because it's + // no longer fully consistent with default trait elaboration in HIR ty lowering. + + match rbp { + RelaxedBoundPolicy::Allowed => return, + RelaxedBoundPolicy::AllowedIfOnTyParam(id, params) => { + if let Some(res) = self.resolver.get_partial_res(id).and_then(|r| r.full_res()) + && let Res::Def(DefKind::TyParam, def_id) = res + && params.iter().any(|p| def_id == self.local_def_id(p.id).to_def_id()) + { + return; + } + if self.tcx.features().more_maybe_bounds() { + return; + } + } + RelaxedBoundPolicy::Forbidden(reason) => { + if self.tcx.features().more_maybe_bounds() { + return; + } + + match reason { + RelaxedBoundForbiddenReason::TraitObjectTy => { + self.dcx().span_err( + span, + "relaxed bounds are not permitted in trait object types", + ); + return; + } + RelaxedBoundForbiddenReason::SuperTrait => { + let mut diag = self.dcx().struct_span_err( + span, + "relaxed bounds are not permitted in supertrait bounds", + ); + if let Some(def_id) = trait_ref.trait_def_id() + && self.tcx.is_lang_item(def_id, hir::LangItem::Sized) + { + diag.note("traits are `?Sized` by default"); + } + diag.emit(); + return; + } + RelaxedBoundForbiddenReason::LateBoundVarsInScope => {} + }; + } } + + self.dcx() + .struct_span_err(span, "this relaxed bound is not permitted here") + .with_note( + "in this context, relaxed bounds are only allowed on \ + type parameters defined by the closest item", + ) + .emit(); } fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext) -> hir::MutTy<'hir> { @@ -2040,17 +2139,19 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { fn lower_param_bounds( &mut self, bounds: &[GenericBound], + rbp: RelaxedBoundPolicy<'_>, itctx: ImplTraitContext, ) -> hir::GenericBounds<'hir> { - self.arena.alloc_from_iter(self.lower_param_bounds_mut(bounds, itctx)) + self.arena.alloc_from_iter(self.lower_param_bounds_mut(bounds, rbp, itctx)) } fn lower_param_bounds_mut( &mut self, bounds: &[GenericBound], + rbp: RelaxedBoundPolicy<'_>, itctx: ImplTraitContext, ) -> impl Iterator<Item = hir::GenericBound<'hir>> { - bounds.iter().map(move |bound| self.lower_param_bound(bound, itctx)) + bounds.iter().map(move |bound| self.lower_param_bound(bound, rbp, itctx)) } #[instrument(level = "debug", skip(self), ret)] @@ -2084,6 +2185,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { bounds, /* colon_span */ None, span, + RelaxedBoundPolicy::Allowed, ImplTraitContext::Universal, hir::PredicateOrigin::ImplTrait, ); diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl index e419154d65d..af93d55c898 100644 --- a/compiler/rustc_ast_passes/messages.ftl +++ b/compiler/rustc_ast_passes/messages.ftl @@ -212,11 +212,6 @@ ast_passes_nomangle_ascii = `#[no_mangle]` requires ASCII identifier ast_passes_obsolete_auto = `impl Trait for .. {"{}"}` is an obsolete syntax .help = use `auto trait Trait {"{}"}` instead -ast_passes_optional_trait_object = `?Trait` is not permitted in trait object types - -ast_passes_optional_trait_supertrait = `?Trait` is not permitted in supertraits - .note = traits are `?{$path_str}` by default - ast_passes_out_of_order_params = {$param_ord} parameters must be declared prior to {$max_param} parameters .suggestion = reorder the parameters: lifetimes, then consts and types diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs index c69250c0305..a08dae11153 100644 --- a/compiler/rustc_ast_passes/src/ast_validation.rs +++ b/compiler/rustc_ast_passes/src/ast_validation.rs @@ -1381,29 +1381,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> { match bound { GenericBound::Trait(trait_ref) => { match (ctxt, trait_ref.modifiers.constness, trait_ref.modifiers.polarity) { - (BoundKind::SuperTraits, BoundConstness::Never, BoundPolarity::Maybe(_)) - if !self.features.more_maybe_bounds() => - { - self.sess - .create_feature_err( - errors::OptionalTraitSupertrait { - span: trait_ref.span, - path_str: pprust::path_to_string(&trait_ref.trait_ref.path), - }, - sym::more_maybe_bounds, - ) - .emit(); - } - (BoundKind::TraitObject, BoundConstness::Never, BoundPolarity::Maybe(_)) - if !self.features.more_maybe_bounds() => - { - self.sess - .create_feature_err( - errors::OptionalTraitObject { span: trait_ref.span }, - sym::more_maybe_bounds, - ) - .emit(); - } ( BoundKind::TraitObject, BoundConstness::Always(_), diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs index c1ebd025c7a..fd4b2528541 100644 --- a/compiler/rustc_ast_passes/src/errors.rs +++ b/compiler/rustc_ast_passes/src/errors.rs @@ -567,22 +567,6 @@ pub(crate) struct NestedLifetimes { } #[derive(Diagnostic)] -#[diag(ast_passes_optional_trait_supertrait)] -#[note] -pub(crate) struct OptionalTraitSupertrait { - #[primary_span] - pub span: Span, - pub path_str: String, -} - -#[derive(Diagnostic)] -#[diag(ast_passes_optional_trait_object)] -pub(crate) struct OptionalTraitObject { - #[primary_span] - pub span: Span, -} - -#[derive(Diagnostic)] #[diag(ast_passes_const_bound_trait_object)] pub(crate) struct ConstBoundTraitObject { #[primary_span] diff --git a/compiler/rustc_error_codes/src/error_codes/E0203.md b/compiler/rustc_error_codes/src/error_codes/E0203.md index 1edb519275f..a4dceedbf1f 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0203.md +++ b/compiler/rustc_error_codes/src/error_codes/E0203.md @@ -1,15 +1,15 @@ -Having multiple relaxed default bounds is unsupported. +Having duplicate relaxed default bounds is unsupported. Erroneous code example: ```compile_fail,E0203 -struct Bad<T: ?Sized + ?Send>{ - inner: T +struct Bad<T: ?Sized + ?Sized>{ + inner: T, } ``` -Here the type `T` cannot have a relaxed bound for multiple default traits -(`Sized` and `Send`). This can be fixed by only using one relaxed bound. +Here the type parameter `T` cannot have duplicate relaxed bounds for default +trait `Sized`. This can be fixed by only using one relaxed bound: ``` struct Good<T: ?Sized>{ diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl index e38ca9e80ce..2428c1aa29f 100644 --- a/compiler/rustc_hir_analysis/messages.ftl +++ b/compiler/rustc_hir_analysis/messages.ftl @@ -371,9 +371,6 @@ hir_analysis_missing_type_params = *[other] parameters } must be specified on the object type -hir_analysis_multiple_relaxed_default_bounds = - type parameter has more than one relaxed default bound, only one is supported - hir_analysis_must_be_name_of_associated_function = must be a name of an associated function hir_analysis_must_implement_not_function = not a function @@ -448,8 +445,6 @@ hir_analysis_parenthesized_fn_trait_expansion = hir_analysis_placeholder_not_allowed_item_signatures = the placeholder `_` is not allowed within types on item signatures for {$kind} .label = not allowed in type signatures -hir_analysis_pointee_sized_trait_object = `PointeeSized` cannot be used with trait objects - hir_analysis_precise_capture_self_alias = `Self` can't be captured in `use<...>` precise captures list, since it is an alias .label = `Self` is not a generic argument, but an alias to the type of the {$what} diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs index f2f1560d8b2..cc53919626e 100644 --- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs +++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs @@ -267,20 +267,16 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen match predicate.kind { hir::WherePredicateKind::BoundPredicate(bound_pred) => { let ty = icx.lowerer().lower_ty_maybe_return_type_notation(bound_pred.bounded_ty); - let bound_vars = tcx.late_bound_vars(predicate.hir_id); - // Keep the type around in a dummy predicate, in case of no bounds. - // That way, `where Ty:` is not a complete noop (see #53696) and `Ty` - // is still checked for WF. + + // This is a `where Ty:` (sic!). if bound_pred.bounds.is_empty() { if let ty::Param(_) = ty.kind() { - // This is a `where T:`, which can be in the HIR from the - // transformation that moves `?Sized` to `T`'s declaration. - // We can skip the predicate because type parameters are - // trivially WF, but also we *should*, to avoid exposing - // users who never wrote `where Type:,` themselves, to - // compiler/tooling bugs from not handling WF predicates. + // We can skip the predicate because type parameters are trivially WF. } else { + // Keep the type around in a dummy predicate. That way, it's not a complete + // noop (see #53696) and `Ty` is still checked for WF. + let span = bound_pred.bounded_ty.span; let predicate = ty::Binder::bind_with_vars( ty::ClauseKind::WellFormed(ty.into()), diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs index fbd21f8b100..26a98722b34 100644 --- a/compiler/rustc_hir_analysis/src/errors.rs +++ b/compiler/rustc_hir_analysis/src/errors.rs @@ -280,13 +280,6 @@ pub(crate) struct CopyImplOnTypeWithDtor { } #[derive(Diagnostic)] -#[diag(hir_analysis_multiple_relaxed_default_bounds, code = E0203)] -pub(crate) struct MultipleRelaxedDefaultBounds { - #[primary_span] - pub spans: Vec<Span>, -} - -#[derive(Diagnostic)] #[diag(hir_analysis_copy_impl_on_non_adt, code = E0206)] pub(crate) struct CopyImplOnNonAdt { #[primary_span] @@ -320,13 +313,6 @@ pub(crate) struct TraitObjectDeclaredWithNoTraits { } #[derive(Diagnostic)] -#[diag(hir_analysis_pointee_sized_trait_object)] -pub(crate) struct PointeeSizedTraitObject { - #[primary_span] - pub span: Span, -} - -#[derive(Diagnostic)] #[diag(hir_analysis_ambiguous_lifetime_bound, code = E0227)] pub(crate) struct AmbiguousLifetimeBound { #[primary_span] diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs index 9a752aeccdd..d7a827c649d 100644 --- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs +++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs @@ -6,7 +6,7 @@ use rustc_errors::struct_span_code_err; use rustc_hir as hir; use rustc_hir::def::{DefKind, Res}; use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId}; -use rustc_hir::{AmbigArg, LangItem, PolyTraitRef}; +use rustc_hir::{AmbigArg, PolyTraitRef}; use rustc_middle::bug; use rustc_middle::ty::{ self as ty, IsSuggestable, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, @@ -85,17 +85,17 @@ fn search_bounds_for<'tcx>( } } -fn collect_unbounds<'tcx>( +fn collect_relaxed_bounds<'tcx>( hir_bounds: &'tcx [hir::GenericBound<'tcx>], self_ty_where_predicates: Option<(LocalDefId, &'tcx [hir::WherePredicate<'tcx>])>, ) -> SmallVec<[&'tcx PolyTraitRef<'tcx>; 1]> { - let mut unbounds: SmallVec<[_; 1]> = SmallVec::new(); + let mut relaxed_bounds: SmallVec<[_; 1]> = SmallVec::new(); search_bounds_for(hir_bounds, self_ty_where_predicates, |ptr| { if matches!(ptr.modifiers.polarity, hir::BoundPolarity::Maybe(_)) { - unbounds.push(ptr); + relaxed_bounds.push(ptr); } }); - unbounds + relaxed_bounds } fn collect_bounds<'a, 'tcx>( @@ -124,13 +124,13 @@ fn collect_sizedness_bounds<'tcx>( self_ty_where_predicates: Option<(LocalDefId, &'tcx [hir::WherePredicate<'tcx>])>, span: Span, ) -> CollectedSizednessBounds { - let sized_did = tcx.require_lang_item(LangItem::Sized, span); + let sized_did = tcx.require_lang_item(hir::LangItem::Sized, span); let sized = collect_bounds(hir_bounds, self_ty_where_predicates, sized_did); - let meta_sized_did = tcx.require_lang_item(LangItem::MetaSized, span); + let meta_sized_did = tcx.require_lang_item(hir::LangItem::MetaSized, span); let meta_sized = collect_bounds(hir_bounds, self_ty_where_predicates, meta_sized_did); - let pointee_sized_did = tcx.require_lang_item(LangItem::PointeeSized, span); + let pointee_sized_did = tcx.require_lang_item(hir::LangItem::PointeeSized, span); let pointee_sized = collect_bounds(hir_bounds, self_ty_where_predicates, pointee_sized_did); CollectedSizednessBounds { sized, meta_sized, pointee_sized } @@ -151,24 +151,6 @@ fn add_trait_bound<'tcx>( } impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { - /// Skip `PointeeSized` bounds. - /// - /// `PointeeSized` is a "fake bound" insofar as anywhere a `PointeeSized` bound exists, there - /// is actually the absence of any bounds. This avoids limitations around non-global where - /// clauses being preferred over item bounds (where `PointeeSized` bounds would be - /// proven) - which can result in errors when a `PointeeSized` supertrait/bound/predicate is - /// added to some items. - pub(crate) fn should_skip_sizedness_bound<'hir>( - &self, - bound: &'hir hir::GenericBound<'tcx>, - ) -> bool { - bound - .trait_ref() - .and_then(|tr| tr.trait_def_id()) - .map(|did| self.tcx().is_lang_item(did, LangItem::PointeeSized)) - .unwrap_or(false) - } - /// Adds sizedness bounds to a trait, trait alias, parameter, opaque type or associated type. /// /// - On parameters, opaque type and associated types, add default `Sized` bound if no explicit @@ -193,8 +175,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { return; } - let meta_sized_did = tcx.require_lang_item(LangItem::MetaSized, span); - let pointee_sized_did = tcx.require_lang_item(LangItem::PointeeSized, span); + let meta_sized_did = tcx.require_lang_item(hir::LangItem::MetaSized, span); + let pointee_sized_did = tcx.require_lang_item(hir::LangItem::PointeeSized, span); // If adding sizedness bounds to a trait, then there are some relevant early exits if let Some(trait_did) = trait_did { @@ -209,9 +191,22 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { return; } } else { - // Report invalid unbounds on sizedness-bounded generic parameters. - let unbounds = collect_unbounds(hir_bounds, self_ty_where_predicates); - self.check_and_report_invalid_unbounds_on_param(unbounds); + // Report invalid relaxed bounds. + // FIXME: Since we only call this validation function here in this function, we only + // fully validate relaxed bounds in contexts where we perform + // "sized elaboration". In most cases that doesn't matter because we *usually* + // reject such relaxed bounds outright during AST lowering. + // However, this can easily get out of sync! Ideally, we would perform this step + // where we are guaranteed to catch *all* bounds like in + // `Self::lower_poly_trait_ref`. List of concrete issues: + // FIXME(more_maybe_bounds): We don't call this for e.g., trait object tys or + // supertrait bounds! + // FIXME(trait_alias, #143122): We don't call it for the RHS. Arguably however, + // AST lowering should reject them outright. + // FIXME(associated_type_bounds): We don't call this for them. However, AST + // lowering should reject them outright (#135229). + let bounds = collect_relaxed_bounds(hir_bounds, self_ty_where_predicates); + self.check_and_report_invalid_relaxed_bounds(bounds); } let collected = collect_sizedness_bounds(tcx, hir_bounds, self_ty_where_predicates, span); @@ -231,7 +226,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { } else { // If there are no explicit sizedness bounds on a parameter then add a default // `Sized` bound. - let sized_did = tcx.require_lang_item(LangItem::Sized, span); + let sized_did = tcx.require_lang_item(hir::LangItem::Sized, span); add_trait_bound(tcx, bounds, self_ty, sized_did, span); } } @@ -463,10 +458,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { 'tcx: 'hir, { for hir_bound in hir_bounds { - if self.should_skip_sizedness_bound(hir_bound) { - continue; - } - // In order to avoid cycles, when we're lowering `SelfTraitThatDefines`, // we skip over any traits that don't define the given associated type. if let PredicateFilter::SelfTraitThatDefines(assoc_ident) = predicate_filter { @@ -482,12 +473,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { match hir_bound { hir::GenericBound::Trait(poly_trait_ref) => { - let hir::TraitBoundModifiers { constness, polarity } = poly_trait_ref.modifiers; let _ = self.lower_poly_trait_ref( - &poly_trait_ref.trait_ref, - poly_trait_ref.span, - constness, - polarity, + poly_trait_ref, param_ty, bounds, predicate_filter, diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs index 364ad38556b..76bb59e3f09 100644 --- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs +++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs @@ -2,7 +2,6 @@ use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet}; use rustc_errors::codes::*; use rustc_errors::struct_span_code_err; use rustc_hir as hir; -use rustc_hir::LangItem; use rustc_hir::def::{DefKind, Res}; use rustc_lint_defs::builtin::UNUSED_ASSOCIATED_TYPE_BOUNDS; use rustc_middle::ty::elaborate::ClauseWithSupertraitSpan; @@ -18,9 +17,7 @@ use tracing::{debug, instrument}; use super::HirTyLowerer; use crate::errors::SelfInTypeAlias; -use crate::hir_ty_lowering::{ - GenericArgCountMismatch, GenericArgCountResult, PredicateFilter, RegionInferReason, -}; +use crate::hir_ty_lowering::{GenericArgCountMismatch, PredicateFilter, RegionInferReason}; impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { /// Lower a trait object type from the HIR to our internal notion of a type. @@ -38,24 +35,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { let mut user_written_bounds = Vec::new(); let mut potential_assoc_types = Vec::new(); - for trait_bound in hir_bounds.iter() { - if let hir::BoundPolarity::Maybe(_) = trait_bound.modifiers.polarity { - continue; - } - if let GenericArgCountResult { - correct: - Err(GenericArgCountMismatch { invalid_args: cur_potential_assoc_types, .. }), - .. - } = self.lower_poly_trait_ref( - &trait_bound.trait_ref, - trait_bound.span, - trait_bound.modifiers.constness, - hir::BoundPolarity::Positive, + for poly_trait_ref in hir_bounds.iter() { + let result = self.lower_poly_trait_ref( + poly_trait_ref, dummy_self, &mut user_written_bounds, PredicateFilter::SelfOnly, - ) { - potential_assoc_types.extend(cur_potential_assoc_types); + ); + if let Err(GenericArgCountMismatch { invalid_args, .. }) = result.correct { + potential_assoc_types.extend(invalid_args); } } @@ -81,13 +69,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { let guar = self.report_trait_object_addition_traits(®ular_traits); return Ty::new_error(tcx, guar); } - // We don't support `PointeeSized` principals - let pointee_sized_did = tcx.require_lang_item(LangItem::PointeeSized, span); - if regular_traits.iter().any(|(pred, _)| pred.def_id() == pointee_sized_did) { - let guar = self.report_pointee_sized_trait_object(span); - return Ty::new_error(tcx, guar); - } - // Don't create a dyn trait if we have errors in the principal. if let Err(guar) = regular_traits.error_reported() { return Ty::new_error(tcx, guar); diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs index 5d85a3f8455..287a5532f01 100644 --- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs +++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs @@ -8,7 +8,7 @@ use rustc_errors::{ }; use rustc_hir::def::{CtorOf, DefKind, Res}; use rustc_hir::def_id::DefId; -use rustc_hir::{self as hir, HirId, LangItem, PolyTraitRef}; +use rustc_hir::{self as hir, HirId, PolyTraitRef}; use rustc_middle::bug; use rustc_middle::ty::fast_reject::{TreatParams, simplify_type}; use rustc_middle::ty::print::{PrintPolyTraitRefExt as _, PrintTraitRefExt as _}; @@ -29,59 +29,54 @@ use tracing::debug; use super::InherentAssocCandidate; use crate::errors::{ self, AssocItemConstraintsNotAllowedHere, ManualImplementation, MissingTypeParams, - ParenthesizedFnTraitExpansion, PointeeSizedTraitObject, TraitObjectDeclaredWithNoTraits, + ParenthesizedFnTraitExpansion, TraitObjectDeclaredWithNoTraits, }; use crate::fluent_generated as fluent; use crate::hir_ty_lowering::{AssocItemQSelf, HirTyLowerer}; impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { - /// Check for multiple relaxed default bounds and relaxed bounds of non-sizedness traits. - pub(crate) fn check_and_report_invalid_unbounds_on_param( + /// Check for duplicate relaxed bounds and relaxed bounds of non-default traits. + pub(crate) fn check_and_report_invalid_relaxed_bounds( &self, - unbounds: SmallVec<[&PolyTraitRef<'_>; 1]>, + relaxed_bounds: SmallVec<[&PolyTraitRef<'_>; 1]>, ) { let tcx = self.tcx(); - let sized_did = tcx.require_lang_item(LangItem::Sized, DUMMY_SP); + let mut grouped_bounds = FxIndexMap::<_, Vec<_>>::default(); - let mut unique_bounds = FxIndexSet::default(); - let mut seen_repeat = false; - for unbound in &unbounds { - if let Res::Def(DefKind::Trait, unbound_def_id) = unbound.trait_ref.path.res { - seen_repeat |= !unique_bounds.insert(unbound_def_id); + for bound in &relaxed_bounds { + if let Res::Def(DefKind::Trait, trait_def_id) = bound.trait_ref.path.res { + grouped_bounds.entry(trait_def_id).or_default().push(bound.span); } } - if unbounds.len() > 1 { - let err = errors::MultipleRelaxedDefaultBounds { - spans: unbounds.iter().map(|ptr| ptr.span).collect(), - }; - - if seen_repeat { - tcx.dcx().emit_err(err); - } else if !tcx.features().more_maybe_bounds() { - tcx.sess.create_feature_err(err, sym::more_maybe_bounds).emit(); - }; + for (trait_def_id, spans) in grouped_bounds { + if spans.len() > 1 { + let name = tcx.item_name(trait_def_id); + self.dcx() + .struct_span_err(spans, format!("duplicate relaxed `{name}` bounds")) + .with_code(E0203) + .emit(); + } } - for unbound in unbounds { - if let Res::Def(DefKind::Trait, did) = unbound.trait_ref.path.res - && ((did == sized_did) || tcx.is_default_trait(did)) + let sized_def_id = tcx.require_lang_item(hir::LangItem::Sized, DUMMY_SP); + + for bound in relaxed_bounds { + if let Res::Def(DefKind::Trait, def_id) = bound.trait_ref.path.res + && (def_id == sized_def_id || tcx.is_default_trait(def_id)) { continue; } - - let unbound_traits = match tcx.sess.opts.unstable_opts.experimental_default_bounds { - true => "`?Sized` and `experimental_default_bounds`", - false => "`?Sized`", - }; self.dcx().span_err( - unbound.span, - format!( - "relaxing a default bound only does something for {}; all other traits are \ - not bound by default", - unbound_traits - ), + bound.span, + if tcx.sess.opts.unstable_opts.experimental_default_bounds + || tcx.features().more_maybe_bounds() + { + "bound modifier `?` can only be applied to default traits like `Sized`" + } else { + "bound modifier `?` can only be applied to `Sized`" + }, ); } } @@ -1410,10 +1405,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { self.dcx().emit_err(TraitObjectDeclaredWithNoTraits { span, trait_alias_span }) } - - pub(super) fn report_pointee_sized_trait_object(&self, span: Span) -> ErrorGuaranteed { - self.dcx().emit_err(PointeeSizedTraitObject { span }) - } } /// Emit an error for the given associated item constraint. diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs index a5bd7c1a34a..78794cd8eb6 100644 --- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs +++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs @@ -747,18 +747,46 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { /// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>` /// where `'a` is a bound region at depth 0. Similarly, the `trait_ref` would be `Bar<'a>`. /// The lowered poly-trait-ref will track this binder explicitly, however. - #[instrument(level = "debug", skip(self, span, constness, bounds))] + #[instrument(level = "debug", skip(self, bounds))] pub(crate) fn lower_poly_trait_ref( &self, - trait_ref: &hir::TraitRef<'tcx>, - span: Span, - constness: hir::BoundConstness, - polarity: hir::BoundPolarity, + poly_trait_ref: &hir::PolyTraitRef<'tcx>, self_ty: Ty<'tcx>, bounds: &mut Vec<(ty::Clause<'tcx>, Span)>, predicate_filter: PredicateFilter, ) -> GenericArgCountResult { + let tcx = self.tcx(); + + // We use the *resolved* bound vars later instead of the HIR ones since the former + // also include the bound vars of the overarching predicate if applicable. + let hir::PolyTraitRef { bound_generic_params: _, modifiers, ref trait_ref, span } = + *poly_trait_ref; + let hir::TraitBoundModifiers { constness, polarity } = modifiers; + let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise()); + + // Relaxed bounds `?Trait` and `PointeeSized` bounds aren't represented in the `middle::ty` IR + // as they denote the *absence* of a default bound. However, we can't bail out early here since + // we still need to perform several validation steps (see below). Instead, simply "pour" all + // resulting bounds "down the drain", i.e., into a new `Vec` that just gets dropped at the end. + let (polarity, bounds) = match polarity { + rustc_ast::BoundPolarity::Positive + if tcx.is_lang_item(trait_def_id, hir::LangItem::PointeeSized) => + { + // To elaborate on the comment directly above, regarding `PointeeSized` specifically, + // we don't "reify" such bounds to avoid trait system limitations -- namely, + // non-global where-clauses being preferred over item bounds (where `PointeeSized` + // bounds would be proven) -- which can result in errors when a `PointeeSized` + // supertrait / bound / predicate is added to some items. + (ty::PredicatePolarity::Positive, &mut Vec::new()) + } + rustc_ast::BoundPolarity::Positive => (ty::PredicatePolarity::Positive, bounds), + rustc_ast::BoundPolarity::Negative(_) => (ty::PredicatePolarity::Negative, bounds), + rustc_ast::BoundPolarity::Maybe(_) => { + (ty::PredicatePolarity::Positive, &mut Vec::new()) + } + }; + let trait_segment = trait_ref.path.segments.last().unwrap(); let _ = self.prohibit_generic_args( @@ -775,7 +803,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { Some(self_ty), ); - let tcx = self.tcx(); let bound_vars = tcx.late_bound_vars(trait_ref.hir_ref_id); debug!(?bound_vars); @@ -786,27 +813,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { debug!(?poly_trait_ref); - let polarity = match polarity { - rustc_ast::BoundPolarity::Positive => ty::PredicatePolarity::Positive, - rustc_ast::BoundPolarity::Negative(_) => ty::PredicatePolarity::Negative, - rustc_ast::BoundPolarity::Maybe(_) => { - // Validate associated type at least. We may want to reject these - // outright in the future... - for constraint in trait_segment.args().constraints { - let _ = self.lower_assoc_item_constraint( - trait_ref.hir_ref_id, - poly_trait_ref, - constraint, - &mut Default::default(), - &mut Default::default(), - constraint.span, - predicate_filter, - ); - } - return arg_count; - } - }; - // We deal with const conditions later. match predicate_filter { PredicateFilter::All @@ -909,7 +915,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ { // Don't register any associated item constraints for negative bounds, // since we should have emitted an error for them earlier, and they // would not be well-formed! - if polarity != ty::PredicatePolarity::Positive { + if polarity == ty::PredicatePolarity::Negative { self.dcx().span_delayed_bug( constraint.span, "negative trait bounds should not have assoc item constraints", |