HIR analysis: Remove unnecessary abstraction over list of clauses

compiler/rustc_hir_analysis/src/collect/item_bounds.rs

@@ -13,7 +13,6 @@ use tracing::{debug, instrument};
 
 use super::ItemCtxt;
 use super::predicates_of::assert_only_contains_predicates_from;
-use crate::bounds::Bounds;
 use crate::hir_ty_lowering::{HirTyLowerer, PredicateFilter};
 
 /// For associated types we include both bounds written on the type
@@ -38,7 +37,7 @@ fn associated_type_bounds<'tcx>(
         );
 
         let icx = ItemCtxt::new(tcx, assoc_item_def_id);
-        let mut bounds = Bounds::default();
+        let mut bounds = Vec::new();
         icx.lowerer().lower_bounds(item_ty, hir_bounds, &mut bounds, ty::List::empty(), filter);
         // Associated types are implicitly sized unless a `?Sized` bound is found
         match filter {
@@ -68,7 +67,7 @@ fn associated_type_bounds<'tcx>(
                 )
             });
 
-        let all_bounds = tcx.arena.alloc_from_iter(bounds.clauses().chain(bounds_from_parent));
+        let all_bounds = tcx.arena.alloc_from_iter(bounds.into_iter().chain(bounds_from_parent));
         debug!(
             "associated_type_bounds({}) = {:?}",
             tcx.def_path_str(assoc_item_def_id.to_def_id()),
@@ -327,7 +326,7 @@ fn opaque_type_bounds<'tcx>(
 ) -> &'tcx [(ty::Clause<'tcx>, Span)] {
     ty::print::with_reduced_queries!({
         let icx = ItemCtxt::new(tcx, opaque_def_id);
-        let mut bounds = Bounds::default();
+        let mut bounds = Vec::new();
         icx.lowerer().lower_bounds(item_ty, hir_bounds, &mut bounds, ty::List::empty(), filter);
         // Opaque types are implicitly sized unless a `?Sized` bound is found
         match filter {
@@ -343,7 +342,7 @@ fn opaque_type_bounds<'tcx>(
         }
         debug!(?bounds);
 
-        tcx.arena.alloc_from_iter(bounds.clauses())
+        tcx.arena.alloc_slice(&bounds)
     })
 }
 

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -13,7 +13,6 @@ use rustc_span::{DUMMY_SP, Ident, Span};
 use tracing::{debug, instrument, trace};
 
 use super::item_bounds::explicit_item_bounds_with_filter;
-use crate::bounds::Bounds;
 use crate::collect::ItemCtxt;
 use crate::constrained_generic_params as cgp;
 use crate::delegation::inherit_predicates_for_delegation_item;
@@ -178,15 +177,15 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
     // on a trait we must also consider the bounds that follow the trait's name,
     // like `trait Foo: A + B + C`.
     if let Some(self_bounds) = is_trait {
-        let mut bounds = Bounds::default();
+        let mut bounds = Vec::new();
         icx.lowerer().lower_bounds(
             tcx.types.self_param,
             self_bounds,
             &mut bounds,
             ty::List::empty(),
             PredicateFilter::All,
         );
-        predicates.extend(bounds.clauses());
+        predicates.extend(bounds);
     }
 
     // In default impls, we can assume that the self type implements
@@ -209,7 +208,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
             GenericParamKind::Lifetime { .. } => (),
             GenericParamKind::Type { .. } => {
                 let param_ty = icx.lowerer().lower_ty_param(param.hir_id);
-                let mut bounds = Bounds::default();
+                let mut bounds = Vec::new();
                 // Params are implicitly sized unless a `?Sized` bound is found
                 icx.lowerer().add_sized_bound(
                     &mut bounds,
@@ -219,7 +218,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     param.span,
                 );
                 trace!(?bounds);
-                predicates.extend(bounds.clauses());
+                predicates.extend(bounds);
                 trace!(?predicates);
             }
             hir::GenericParamKind::Const { .. } => {
@@ -264,15 +263,15 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     }
                 }
 
-                let mut bounds = Bounds::default();
+                let mut bounds = Vec::new();
                 icx.lowerer().lower_bounds(
                     ty,
                     bound_pred.bounds,
                     &mut bounds,
                     bound_vars,
                     PredicateFilter::All,
                 );
-                predicates.extend(bounds.clauses());
+                predicates.extend(bounds);
             }
 
             hir::WherePredicateKind::RegionPredicate(region_pred) => {
@@ -627,15 +626,15 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
     let icx = ItemCtxt::new(tcx, trait_def_id);
 
     let self_param_ty = tcx.types.self_param;
-    let mut bounds = Bounds::default();
+    let mut bounds = Vec::new();
     icx.lowerer().lower_bounds(self_param_ty, superbounds, &mut bounds, ty::List::empty(), filter);
 
     let where_bounds_that_match =
         icx.probe_ty_param_bounds_in_generics(generics, item.owner_id.def_id, filter);
 
     // Combine the two lists to form the complete set of superbounds:
     let implied_bounds =
-        &*tcx.arena.alloc_from_iter(bounds.clauses().chain(where_bounds_that_match));
+        &*tcx.arena.alloc_from_iter(bounds.into_iter().chain(where_bounds_that_match));
     debug!(?implied_bounds);
 
     // Now require that immediate supertraits are lowered, which will, in
@@ -904,7 +903,7 @@ impl<'tcx> ItemCtxt<'tcx> {
         param_def_id: LocalDefId,
         filter: PredicateFilter,
     ) -> Vec<(ty::Clause<'tcx>, Span)> {
-        let mut bounds = Bounds::default();
+        let mut bounds = Vec::new();
 
         for predicate in hir_generics.predicates {
             let hir_id = predicate.hir_id;
@@ -938,7 +937,7 @@ impl<'tcx> ItemCtxt<'tcx> {
             );
         }
 
-        bounds.clauses().collect()
+        bounds
     }
 }
 
@@ -1007,7 +1006,7 @@ pub(super) fn const_conditions<'tcx>(
     };
 
     let icx = ItemCtxt::new(tcx, def_id);
-    let mut bounds = Bounds::default();
+    let mut bounds = Vec::new();
 
     for pred in generics.predicates {
         match pred.kind {
@@ -1027,12 +1026,12 @@ pub(super) fn const_conditions<'tcx>(
     }
 
     if let Some((def_id, supertraits)) = trait_def_id_and_supertraits {
-        bounds.push_const_bound(
-            tcx,
-            ty::Binder::dummy(ty::TraitRef::identity(tcx, def_id.to_def_id())),
-            ty::BoundConstness::Maybe,
+        // We've checked above that the trait is conditionally const.
+        bounds.push((
+            ty::Binder::dummy(ty::TraitRef::identity(tcx, def_id.to_def_id()))
+                .to_host_effect_clause(tcx, ty::BoundConstness::Maybe),
             DUMMY_SP,
-        );
+        ));
 
         icx.lowerer().lower_bounds(
             tcx.types.self_param,
@@ -1045,7 +1044,7 @@ pub(super) fn const_conditions<'tcx>(
 
     ty::ConstConditions {
         parent: has_parent.then(|| tcx.local_parent(def_id).to_def_id()),
-        predicates: tcx.arena.alloc_from_iter(bounds.clauses().map(|(clause, span)| {
+        predicates: tcx.arena.alloc_from_iter(bounds.into_iter().map(|(clause, span)| {
             (
                 clause.kind().map_bound(|clause| match clause {
                     ty::ClauseKind::HostEffect(ty::HostEffectPredicate {

compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs

@@ -8,15 +8,14 @@ use rustc_hir::HirId;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::bug;
-use rustc_middle::ty::{self as ty, IsSuggestable, Ty, TyCtxt};
+use rustc_middle::ty::{self as ty, IsSuggestable, Ty, TyCtxt, Upcast};
 use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::traits;
 use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
 use smallvec::SmallVec;
 use tracing::{debug, instrument};
 
 use super::errors::GenericsArgsErrExtend;
-use crate::bounds::Bounds;
 use crate::errors;
 use crate::hir_ty_lowering::{
     AssocItemQSelf, FeedConstTy, HirTyLowerer, PredicateFilter, RegionInferReason,
@@ -28,7 +27,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// Doesn't add the bound if the HIR bounds contain any of `Sized`, `?Sized` or `!Sized`.
     pub(crate) fn add_sized_bound(
         &self,
-        bounds: &mut Bounds<'tcx>,
+        bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         self_ty: Ty<'tcx>,
         hir_bounds: &'tcx [hir::GenericBound<'tcx>],
         self_ty_where_predicates: Option<(LocalDefId, &'tcx [hir::WherePredicate<'tcx>])>,
@@ -113,10 +112,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         if seen_sized_unbound || seen_negative_sized_bound || seen_positive_sized_bound {
             // There was in fact a `?Sized`, `!Sized` or explicit `Sized` bound;
             // we don't need to do anything.
-        } else if sized_def_id.is_some() {
+        } else if let Some(sized_def_id) = sized_def_id {
             // There was no `?Sized`, `!Sized` or explicit `Sized` bound;
             // add `Sized` if it's available.
-            bounds.push_sized(tcx, self_ty, span);
+            let trait_ref = ty::TraitRef::new(tcx, sized_def_id, [self_ty]);
+            // Preferable to put this obligation first, since we report better errors for sized ambiguity.
+            bounds.insert(0, (trait_ref.upcast(tcx), span));
         }
     }
 
@@ -146,7 +147,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         param_ty: Ty<'tcx>,
         hir_bounds: I,
-        bounds: &mut Bounds<'tcx>,
+        bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
         predicate_filter: PredicateFilter,
     ) where
@@ -189,14 +190,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     }
 
                     let region = self.lower_lifetime(lifetime, RegionInferReason::OutlivesBound);
-                    bounds.push_region_bound(
-                        self.tcx(),
-                        ty::Binder::bind_with_vars(
-                            ty::OutlivesPredicate(param_ty, region),
-                            bound_vars,
-                        ),
-                        lifetime.ident.span,
+                    let bound = ty::Binder::bind_with_vars(
+                        ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(param_ty, region)),
+                        bound_vars,
                     );
+                    bounds.push((bound.upcast(self.tcx()), lifetime.ident.span));
                 }
                 hir::GenericBound::Use(..) => {
                     // We don't actually lower `use` into the type layer.
@@ -219,7 +217,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         hir_ref_id: hir::HirId,
         trait_ref: ty::PolyTraitRef<'tcx>,
         constraint: &hir::AssocItemConstraint<'tcx>,
-        bounds: &mut Bounds<'tcx>,
+        bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         duplicates: &mut FxIndexMap<DefId, Span>,
         path_span: Span,
         predicate_filter: PredicateFilter,
@@ -389,14 +387,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     PredicateFilter::All
                     | PredicateFilter::SelfOnly
                     | PredicateFilter::SelfAndAssociatedTypeBounds => {
-                        bounds.push_projection_bound(
-                            tcx,
-                            projection_term.map_bound(|projection_term| ty::ProjectionPredicate {
+                        let bound = projection_term.map_bound(|projection_term| {
+                            ty::ClauseKind::Projection(ty::ProjectionPredicate {
                                 projection_term,
                                 term,
-                            }),
-                            constraint.span,
-                        );
+                            })
+                        });
+                        bounds.push((bound.upcast(tcx), constraint.span));
                     }
                     // SelfTraitThatDefines is only interested in trait predicates.
                     PredicateFilter::SelfTraitThatDefines(_) => {}

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs

@@ -17,7 +17,6 @@ use smallvec::{SmallVec, smallvec};
 use tracing::{debug, instrument};
 
 use super::HirTyLowerer;
-use crate::bounds::Bounds;
 use crate::hir_ty_lowering::{
     GenericArgCountMismatch, GenericArgCountResult, PredicateFilter, RegionInferReason,
 };
@@ -36,7 +35,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let tcx = self.tcx();
         let dummy_self = tcx.types.trait_object_dummy_self;
 
-        let mut user_written_bounds = Bounds::default();
+        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 {
@@ -60,15 +59,17 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
 
         let (trait_bounds, mut projection_bounds) =
-            traits::expand_trait_aliases(tcx, user_written_bounds.clauses());
+            traits::expand_trait_aliases(tcx, user_written_bounds.iter().copied());
         let (regular_traits, mut auto_traits): (Vec<_>, Vec<_>) = trait_bounds
             .into_iter()
             .partition(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()));
 
         // We  don't support empty trait objects.
         if regular_traits.is_empty() && auto_traits.is_empty() {
-            let guar =
-                self.report_trait_object_with_no_traits_error(span, user_written_bounds.clauses());
+            let guar = self.report_trait_object_with_no_traits_error(
+                span,
+                user_written_bounds.iter().copied(),
+            );
             return Ty::new_error(tcx, guar);
         }
         // We don't support >1 principal
@@ -84,7 +85,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // Check that there are no gross dyn-compatibility violations;
         // most importantly, that the supertraits don't contain `Self`,
         // to avoid ICEs.
-        for (clause, span) in user_written_bounds.clauses() {
+        for (clause, span) in user_written_bounds {
             if let Some(trait_pred) = clause.as_trait_clause() {
                 let violations =
                     hir_ty_lowering_dyn_compatibility_violations(tcx, trait_pred.def_id());

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -49,9 +49,9 @@ use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::wf::object_region_bounds;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
+use rustc_type_ir::Upcast;
 use tracing::{debug, instrument};
 
-use crate::bounds::Bounds;
 use crate::check::check_abi_fn_ptr;
 use crate::errors::{AmbiguousLifetimeBound, BadReturnTypeNotation, InvalidBaseType};
 use crate::hir_ty_lowering::errors::{GenericsArgsErrExtend, prohibit_assoc_item_constraint};
@@ -691,7 +691,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         constness: hir::BoundConstness,
         polarity: hir::BoundPolarity,
         self_ty: Ty<'tcx>,
-        bounds: &mut Bounds<'tcx>,
+        bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         predicate_filter: PredicateFilter,
     ) -> GenericArgCountResult {
         let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise());
@@ -720,6 +720,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             bound_vars,
         );
 
+        debug!(?poly_trait_ref);
+
         let polarity = match polarity {
             rustc_ast::BoundPolarity::Positive => ty::PredicatePolarity::Positive,
             rustc_ast::BoundPolarity::Negative(_) => ty::PredicatePolarity::Negative,
@@ -741,6 +743,26 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
         };
 
+        // We deal with const conditions later.
+        match predicate_filter {
+            PredicateFilter::All
+            | PredicateFilter::SelfOnly
+            | PredicateFilter::SelfTraitThatDefines(..)
+            | PredicateFilter::SelfAndAssociatedTypeBounds => {
+                let bound = poly_trait_ref.map_bound(|trait_ref| {
+                    ty::ClauseKind::Trait(ty::TraitPredicate { trait_ref, polarity })
+                });
+                let bound = (bound.upcast(tcx), span);
+                // FIXME(-Znext-solver): We can likely remove this hack once the new trait solver lands.
+                if tcx.is_lang_item(trait_def_id, rustc_hir::LangItem::Sized) {
+                    bounds.insert(0, bound);
+                } else {
+                    bounds.push(bound);
+                }
+            }
+            PredicateFilter::ConstIfConst | PredicateFilter::SelfConstIfConst => {}
+        }
+
         if let hir::BoundConstness::Always(span) | hir::BoundConstness::Maybe(span) = constness
             && !self.tcx().is_const_trait(trait_def_id)
         {
@@ -765,58 +787,53 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 suggestion_pre,
                 suggestion,
             });
-        }
-
-        match predicate_filter {
-            // This is only concerned with trait predicates.
-            PredicateFilter::SelfTraitThatDefines(..) => {
-                bounds.push_trait_bound(tcx, poly_trait_ref, span, polarity);
-            }
-            PredicateFilter::All
-            | PredicateFilter::SelfOnly
-            | PredicateFilter::SelfAndAssociatedTypeBounds => {
-                debug!(?poly_trait_ref);
-                bounds.push_trait_bound(tcx, poly_trait_ref, span, polarity);
-
-                match constness {
-                    hir::BoundConstness::Always(span) => {
-                        if polarity == ty::PredicatePolarity::Positive {
-                            bounds.push_const_bound(
-                                tcx,
-                                poly_trait_ref,
-                                ty::BoundConstness::Const,
-                                span,
-                            );
+        } else {
+            match predicate_filter {
+                // This is only concerned with trait predicates.
+                PredicateFilter::SelfTraitThatDefines(..) => {}
+                PredicateFilter::All
+                | PredicateFilter::SelfOnly
+                | PredicateFilter::SelfAndAssociatedTypeBounds => {
+                    match constness {
+                        hir::BoundConstness::Always(span) => {
+                            if polarity == ty::PredicatePolarity::Positive {
+                                bounds.push((
+                                    poly_trait_ref
+                                        .to_host_effect_clause(tcx, ty::BoundConstness::Const),
+                                    span,
+                                ));
+                            }
                         }
+                        hir::BoundConstness::Maybe(_) => {
+                            // We don't emit a const bound here, since that would mean that we
+                            // unconditionally need to prove a `HostEffect` predicate, even when
+                            // the predicates are being instantiated in a non-const context. This
+                            // is instead handled in the `const_conditions` query.
+                        }
+                        hir::BoundConstness::Never => {}
                     }
-                    hir::BoundConstness::Maybe(_) => {
-                        // We don't emit a const bound here, since that would mean that we
-                        // unconditionally need to prove a `HostEffect` predicate, even when
-                        // the predicates are being instantiated in a non-const context. This
-                        // is instead handled in the `const_conditions` query.
-                    }
-                    hir::BoundConstness::Never => {}
                 }
-            }
-            // On the flip side, when filtering `ConstIfConst` bounds, we only need to convert
-            // `~const` bounds. All other predicates are handled in their respective queries.
-            //
-            // Note that like `PredicateFilter::SelfOnly`, we don't need to do any filtering
-            // here because we only call this on self bounds, and deal with the recursive case
-            // in `lower_assoc_item_constraint`.
-            PredicateFilter::ConstIfConst | PredicateFilter::SelfConstIfConst => match constness {
-                hir::BoundConstness::Maybe(span) => {
-                    if polarity == ty::PredicatePolarity::Positive {
-                        bounds.push_const_bound(
-                            tcx,
-                            poly_trait_ref,
-                            ty::BoundConstness::Maybe,
-                            span,
-                        );
+                // On the flip side, when filtering `ConstIfConst` bounds, we only need to convert
+                // `~const` bounds. All other predicates are handled in their respective queries.
+                //
+                // Note that like `PredicateFilter::SelfOnly`, we don't need to do any filtering
+                // here because we only call this on self bounds, and deal with the recursive case
+                // in `lower_assoc_item_constraint`.
+                PredicateFilter::ConstIfConst | PredicateFilter::SelfConstIfConst => {
+                    match constness {
+                        hir::BoundConstness::Maybe(span) => {
+                            if polarity == ty::PredicatePolarity::Positive {
+                                bounds.push((
+                                    poly_trait_ref
+                                        .to_host_effect_clause(tcx, ty::BoundConstness::Maybe),
+                                    span,
+                                ));
+                            }
+                        }
+                        hir::BoundConstness::Always(_) | hir::BoundConstness::Never => {}
                     }
                 }
-                hir::BoundConstness::Always(_) | hir::BoundConstness::Never => {}
-            },
+            }
         }
 
         let mut dup_constraints = FxIndexMap::default();
@@ -2382,19 +2399,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 // Impl trait in bindings lower as an infer var with additional
                 // set of type bounds.
                 let self_ty = self.ty_infer(None, hir_ty.span);
-                let mut bounds = Bounds::default();
+                let mut bounds = Vec::new();
                 self.lower_bounds(
                     self_ty,
                     hir_bounds.iter(),
                     &mut bounds,
                     ty::List::empty(),
                     PredicateFilter::All,
                 );
-                self.register_trait_ascription_bounds(
-                    bounds.clauses().collect(),
-                    hir_ty.hir_id,
-                    hir_ty.span,
-                );
+                self.register_trait_ascription_bounds(bounds, hir_ty.hir_id, hir_ty.span);
                 self_ty
             }
             // If we encounter a type relative path with RTN generics, then it must have

compiler/rustc_hir_analysis/src/lib.rs

@@ -80,7 +80,6 @@ This API is completely unstable and subject to change.
 pub mod check;
 
 pub mod autoderef;
-mod bounds;
 mod check_unused;
 mod coherence;
 mod collect;

compiler/rustc_middle/src/ty/generic_args.rs

@@ -495,7 +495,7 @@ impl<'tcx> GenericArgs<'tcx> {
         self.iter().filter_map(|k| k.as_const())
     }
 
-    /// Returns generic arguments that are not lifetimes or host effect params.
+    /// Returns generic arguments that are not lifetimes.
     #[inline]
     pub fn non_erasable_generics(
         &'tcx self,