Rollup merge of rust-lang#137100 - fmease:hirtylow-rm-clauses-wrapper, r=compiler-errors

HIR analysis: Remove unnecessary abstraction over list of clauses

`rustc_hir_analysis::bounds::Bounds` with its methods is nowadays a paper-thin wrapper around `Vec<(Clause, Span)>`s and `Vec::push` essentially.

Its existence slightly annoyed me (and I keep opening its corresp. file instead of the identically named `bounds.rs` in `hir_ty_lowering/` that I actually want most of the time :P).

Opening to check if you agree with inlining it.
r? compiler-errors or reassign

Author: matthiaskrgr

compiler/rustc_hir_analysis/src/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/item_bounds.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/collect/predicates_of.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(_) => {}