Box HIR Generics and Impl.

16 files changed, 61 insertions, 56 deletions

diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 8ae07982f6f..7fc53d264a6 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -410,7 +410,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     ImplPolarity::Positive => ImplPolarity::Positive,
                     ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(s)),
                 };
-                hir::ItemKind::Impl(hir::Impl {
+                hir::ItemKind::Impl(self.arena.alloc(hir::Impl {
                     unsafety: self.lower_unsafety(unsafety),
                     polarity,
                     defaultness,
@@ -420,7 +420,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     of_trait: trait_ref,
                     self_ty: lowered_ty,
                     items: new_impl_items,
-                })
+                }))
             }
             ItemKind::Trait(box Trait {
                 is_auto,
@@ -1226,7 +1226,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         id: NodeId,
         kind: FnDeclKind,
         is_async: Option<NodeId>,
-    ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
+    ) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) {
         let header = self.lower_fn_header(sig.header);
         let (generics, decl) = self.add_implicit_generics(generics, id, |this, idty| {
             this.lower_fn_decl(&sig.decl, Some((id, idty)), kind, is_async)
@@ -1349,7 +1349,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         generics: &Generics,
         itctx: ImplTraitContext<'_, 'hir>,
-    ) -> hir::Generics<'hir> {
+    ) -> &'hir hir::Generics<'hir> {
         let generics_ctor = self.lower_generics_mut(generics, itctx);
         generics_ctor.into_generics(self.arena)
     }
@@ -1419,11 +1419,11 @@ pub(super) struct GenericsCtor<'hir> {
 }
 
 impl<'hir> GenericsCtor<'hir> {
-    pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> hir::Generics<'hir> {
-        hir::Generics {
+    pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> &'hir hir::Generics<'hir> {
+        arena.alloc(hir::Generics {
             params: arena.alloc_from_iter(self.params),
             where_clause: self.where_clause,
             span: self.span,
-        }
+        })
     }
 }
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index de4f8e04b16..a5e12408087 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -719,7 +719,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         generics: &Generics,
         parent_node_id: NodeId,
         f: impl FnOnce(&mut Self, &mut Vec<hir::GenericParam<'hir>>) -> T,
-    ) -> (hir::Generics<'hir>, T) {
+    ) -> (&'hir hir::Generics<'hir>, T) {
         let mut impl_trait_defs = Vec::new();
         let mut lowered_generics = self.lower_generics_mut(
             generics,
@@ -1383,11 +1383,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             debug!("lower_opaque_impl_trait: lifetime_defs={:#?}", lifetime_defs);
 
             let opaque_ty_item = hir::OpaqueTy {
-                generics: hir::Generics {
+                generics: self.arena.alloc(hir::Generics {
                     params: lifetime_defs,
                     where_clause: hir::WhereClause { predicates: &[], span: lctx.lower_span(span) },
                     span: lctx.lower_span(span),
-                },
+                }),
                 bounds: hir_bounds,
                 origin,
             };
@@ -1715,11 +1715,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             debug!("lower_async_fn_ret_ty: generic_params={:#?}", generic_params);
 
             let opaque_ty_item = hir::OpaqueTy {
-                generics: hir::Generics {
+                generics: this.arena.alloc(hir::Generics {
                     params: generic_params,
                     where_clause: hir::WhereClause { predicates: &[], span: this.lower_span(span) },
                     span: this.lower_span(span),
-                },
+                }),
                 bounds: arena_vec![this; future_bound],
                 origin: hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
             };
diff --git a/compiler/rustc_hir/src/arena.rs b/compiler/rustc_hir/src/arena.rs
index 27ec4619064..5d1314ebb48 100644
--- a/compiler/rustc_hir/src/arena.rs
+++ b/compiler/rustc_hir/src/arena.rs
@@ -15,11 +15,13 @@ macro_rules! arena_types {
             [] block: rustc_hir::Block<'tcx>,
             [] bare_fn_ty: rustc_hir::BareFnTy<'tcx>,
             [] body: rustc_hir::Body<'tcx>,
+            [] generics: rustc_hir::Generics<'tcx>,
             [] generic_arg: rustc_hir::GenericArg<'tcx>,
             [] generic_args: rustc_hir::GenericArgs<'tcx>,
             [] generic_bound: rustc_hir::GenericBound<'tcx>,
             [] generic_param: rustc_hir::GenericParam<'tcx>,
             [] expr: rustc_hir::Expr<'tcx>,
+            [] impl_: rustc_hir::Impl<'tcx>,
             [] let_expr: rustc_hir::Let<'tcx>,
             [] expr_field: rustc_hir::ExprField<'tcx>,
             [] pat_field: rustc_hir::PatField<'tcx>,
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 7d9203b70ab..b723312f094 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -572,12 +572,13 @@ pub struct Generics<'hir> {
 }
 
 impl<'hir> Generics<'hir> {
-    pub const fn empty() -> Generics<'hir> {
-        Generics {
+    pub const fn empty() -> &'hir Generics<'hir> {
+        const NOPE: Generics<'_> = Generics {
             params: &[],
             where_clause: WhereClause { predicates: &[], span: DUMMY_SP },
             span: DUMMY_SP,
-        }
+        };
+        &NOPE
     }
 
     pub fn get_named(&self, name: Symbol) -> Option<&GenericParam<'_>> {
@@ -2075,7 +2076,7 @@ impl TraitItemId {
 pub struct TraitItem<'hir> {
     pub ident: Ident,
     pub def_id: LocalDefId,
-    pub generics: Generics<'hir>,
+    pub generics: &'hir Generics<'hir>,
     pub kind: TraitItemKind<'hir>,
     pub span: Span,
 }
@@ -2135,7 +2136,7 @@ impl ImplItemId {
 pub struct ImplItem<'hir> {
     pub ident: Ident,
     pub def_id: LocalDefId,
-    pub generics: Generics<'hir>,
+    pub generics: &'hir Generics<'hir>,
     pub kind: ImplItemKind<'hir>,
     pub span: Span,
     pub vis_span: Span,
@@ -2340,7 +2341,7 @@ pub struct BareFnTy<'hir> {
 
 #[derive(Debug, HashStable_Generic)]
 pub struct OpaqueTy<'hir> {
-    pub generics: Generics<'hir>,
+    pub generics: &'hir Generics<'hir>,
     pub bounds: GenericBounds<'hir>,
     pub origin: OpaqueTyOrigin,
 }
@@ -2814,7 +2815,7 @@ pub enum ItemKind<'hir> {
     /// A `const` item.
     Const(&'hir Ty<'hir>, BodyId),
     /// A function declaration.
-    Fn(FnSig<'hir>, Generics<'hir>, BodyId),
+    Fn(FnSig<'hir>, &'hir Generics<'hir>, BodyId),
     /// A MBE macro definition (`macro_rules!` or `macro`).
     Macro(ast::MacroDef, MacroKind),
     /// A module.
@@ -2824,22 +2825,22 @@ pub enum ItemKind<'hir> {
     /// Module-level inline assembly (from `global_asm!`).
     GlobalAsm(&'hir InlineAsm<'hir>),
     /// A type alias, e.g., `type Foo = Bar<u8>`.
-    TyAlias(&'hir Ty<'hir>, Generics<'hir>),
+    TyAlias(&'hir Ty<'hir>, &'hir Generics<'hir>),
     /// An opaque `impl Trait` type alias, e.g., `type Foo = impl Bar;`.
     OpaqueTy(OpaqueTy<'hir>),
     /// An enum definition, e.g., `enum Foo<A, B> {C<A>, D<B>}`.
-    Enum(EnumDef<'hir>, Generics<'hir>),
+    Enum(EnumDef<'hir>, &'hir Generics<'hir>),
     /// A struct definition, e.g., `struct Foo<A> {x: A}`.
-    Struct(VariantData<'hir>, Generics<'hir>),
+    Struct(VariantData<'hir>, &'hir Generics<'hir>),
     /// A union definition, e.g., `union Foo<A, B> {x: A, y: B}`.
-    Union(VariantData<'hir>, Generics<'hir>),
+    Union(VariantData<'hir>, &'hir Generics<'hir>),
     /// A trait definition.
-    Trait(IsAuto, Unsafety, Generics<'hir>, GenericBounds<'hir>, &'hir [TraitItemRef]),
+    Trait(IsAuto, Unsafety, &'hir Generics<'hir>, GenericBounds<'hir>, &'hir [TraitItemRef]),
     /// A trait alias.
-    TraitAlias(Generics<'hir>, GenericBounds<'hir>),
+    TraitAlias(&'hir Generics<'hir>, GenericBounds<'hir>),
 
     /// An implementation, e.g., `impl<A> Trait for Foo { .. }`.
-    Impl(Impl<'hir>),
+    Impl(&'hir Impl<'hir>),
 }
 
 #[derive(Debug, HashStable_Generic)]
@@ -2851,7 +2852,7 @@ pub struct Impl<'hir> {
     // decoding as `Span`s cannot be decoded when a `Session` is not available.
     pub defaultness_span: Option<Span>,
     pub constness: Constness,
-    pub generics: Generics<'hir>,
+    pub generics: &'hir Generics<'hir>,
 
     /// The trait being implemented, if any.
     pub of_trait: Option<TraitRef<'hir>>,
@@ -2993,7 +2994,7 @@ impl ForeignItem<'_> {
 #[derive(Debug, HashStable_Generic)]
 pub enum ForeignItemKind<'hir> {
     /// A foreign function.
-    Fn(&'hir FnDecl<'hir>, &'hir [Ident], Generics<'hir>),
+    Fn(&'hir FnDecl<'hir>, &'hir [Ident], &'hir Generics<'hir>),
     /// A foreign static item (`static ext: u8`).
     Static(&'hir Ty<'hir>, Mutability),
     /// A foreign type.
@@ -3326,9 +3327,11 @@ mod size_asserts {
     rustc_data_structures::static_assert_size!(super::QPath<'static>, 24);
     rustc_data_structures::static_assert_size!(super::Ty<'static>, 72);
     rustc_data_structures::static_assert_size!(super::GenericBound<'_>, 48);
+    rustc_data_structures::static_assert_size!(super::Generics<'static>, 48);
+    rustc_data_structures::static_assert_size!(super::Impl<'static>, 80);
 
-    rustc_data_structures::static_assert_size!(super::Item<'static>, 160);
-    rustc_data_structures::static_assert_size!(super::TraitItem<'static>, 128);
-    rustc_data_structures::static_assert_size!(super::ImplItem<'static>, 120);
-    rustc_data_structures::static_assert_size!(super::ForeignItem<'static>, 112);
+    rustc_data_structures::static_assert_size!(super::Item<'static>, 80);
+    rustc_data_structures::static_assert_size!(super::TraitItem<'static>, 88);
+    rustc_data_structures::static_assert_size!(super::ImplItem<'static>, 80);
+    rustc_data_structures::static_assert_size!(super::ForeignItem<'static>, 72);
 }
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index 59bd46ae353..002fa607416 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -619,7 +619,7 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) {
             visitor.visit_generics(generics);
             walk_list!(visitor, visit_trait_ref, of_trait);
             visitor.visit_ty(self_ty);
-            walk_list!(visitor, visit_impl_item_ref, items);
+            walk_list!(visitor, visit_impl_item_ref, *items);
         }
         ItemKind::Struct(ref struct_definition, ref generics)
         | ItemKind::Union(ref struct_definition, ref generics) => {
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index 87ff9457783..3978579c60b 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -626,8 +626,8 @@ impl<'a> State<'a> {
                 items,
             }) => {
                 self.head("");
-                self.print_defaultness(defaultness);
-                self.print_unsafety(unsafety);
+                self.print_defaultness(*defaultness);
+                self.print_unsafety(*unsafety);
                 self.word_nbsp("impl");
 
                 if !generics.params.is_empty() {
@@ -635,7 +635,7 @@ impl<'a> State<'a> {
                     self.space();
                 }
 
-                if constness == hir::Constness::Const {
+                if *constness == hir::Constness::Const {
                     self.word_nbsp("const");
                 }
 
@@ -655,7 +655,7 @@ impl<'a> State<'a> {
                 self.space();
                 self.bopen();
                 self.print_inner_attributes(attrs);
-                for impl_item in items {
+                for impl_item in *items {
                     self.ann.nested(self, Nested::ImplItem(impl_item.id));
                 }
                 self.bclose(item.span);
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 68658e2616e..e097ab9d7fd 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1199,8 +1199,8 @@ impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
                     });
                 }
             }
-            hir::ItemKind::Impl(hir::Impl { ref generics, items, .. }) => {
-                for it in items {
+            hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
+                for it in *items {
                     if let hir::AssocItemKind::Fn { .. } = it.kind {
                         if let Some(no_mangle_attr) = cx
                             .sess()
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index ed49eebd16d..b46ea955a3a 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1462,8 +1462,8 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 }))
             }
             hir::ItemKind::Impl(hir::Impl { defaultness, constness, .. }) => {
-                self.tables.impl_defaultness.set(def_id.index, defaultness);
-                self.tables.impl_constness.set(def_id.index, constness);
+                self.tables.impl_defaultness.set(def_id.index, *defaultness);
+                self.tables.impl_constness.set(def_id.index, *constness);
 
                 let trait_ref = self.tcx.impl_trait_ref(def_id);
                 if let Some(trait_ref) = trait_ref {
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index b661f6f9d72..3cd18390285 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -512,7 +512,7 @@ impl<'v, 'tcx> ItemLikeVisitor<'v> for LifeSeeder<'tcx> {
                 if of_trait.is_some() {
                     self.worklist.push(item.def_id);
                 }
-                for impl_item_ref in items {
+                for impl_item_ref in *items {
                     let impl_item = self.tcx.hir().impl_item(impl_item_ref.id);
                     if of_trait.is_some()
                         || has_allow_dead_code_or_lang_attr(self.tcx, impl_item.hir_id())
diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index 35a858cb86c..10dc587be6e 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -737,7 +737,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                     }
                 }
 
-                for impl_item_ref in items {
+                for impl_item_ref in *items {
                     let impl_item = self.tcx.associated_item(impl_item_ref.id.def_id);
 
                     if let Some(def_id) = impl_item.trait_item_def_id {
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 894ff0f17f8..a5243bf8ac3 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -86,7 +86,7 @@ impl ForLifetimeSpanType {
     }
 }
 
-impl<'tcx> Into<MissingLifetimeSpot<'tcx>> for &'tcx hir::Generics<'tcx> {
+impl<'tcx> Into<MissingLifetimeSpot<'tcx>> for &&'tcx hir::Generics<'tcx> {
     fn into(self) -> MissingLifetimeSpot<'tcx> {
         MissingLifetimeSpot::Generics(self)
     }
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index 0ccc2b6b182..e36eebcf931 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -2200,16 +2200,16 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
 
     let icx = ItemCtxt::new(tcx, def_id);
 
-    const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
+    const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty();
 
     // We use an `IndexSet` to preserves order of insertion.
     // Preserving the order of insertion is important here so as not to break UI tests.
     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
 
     let ast_generics = match node {
-        Node::TraitItem(item) => &item.generics,
+        Node::TraitItem(item) => item.generics,
 
-        Node::ImplItem(item) => &item.generics,
+        Node::ImplItem(item) => item.generics,
 
         Node::Item(item) => {
             match item.kind {
@@ -2223,15 +2223,15 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
                 | ItemKind::TyAlias(_, ref generics)
                 | ItemKind::Enum(_, ref generics)
                 | ItemKind::Struct(_, ref generics)
-                | ItemKind::Union(_, ref generics) => generics,
+                | ItemKind::Union(_, ref generics) => *generics,
 
                 ItemKind::Trait(_, _, ref generics, ..) => {
                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
-                    generics
+                    *generics
                 }
                 ItemKind::TraitAlias(ref generics, _) => {
                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
-                    generics
+                    *generics
                 }
                 ItemKind::OpaqueTy(OpaqueTy {
                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
@@ -2268,7 +2268,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
 
         Node::ForeignItem(item) => match item.kind {
             ForeignItemKind::Static(..) => NO_GENERICS,
-            ForeignItemKind::Fn(_, _, ref generics) => generics,
+            ForeignItemKind::Fn(_, _, ref generics) => *generics,
             ForeignItemKind::Type => NO_GENERICS,
         },
 
diff --git a/compiler/rustc_typeck/src/collect/type_of.rs b/compiler/rustc_typeck/src/collect/type_of.rs
index fa06ec09fce..495b8d3b4ee 100644
--- a/compiler/rustc_typeck/src/collect/type_of.rs
+++ b/compiler/rustc_typeck/src/collect/type_of.rs
@@ -337,8 +337,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
                         icx.to_ty(ty)
                     }
                 }
-                ItemKind::TyAlias(self_ty, _)
-                | ItemKind::Impl(hir::Impl { self_ty, .. }) => icx.to_ty(self_ty),
+                ItemKind::TyAlias(self_ty, _) => icx.to_ty(self_ty),
+                ItemKind::Impl(hir::Impl { self_ty, .. }) => icx.to_ty(*self_ty),
                 ItemKind::Fn(..) => {
                     let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
                     tcx.mk_fn_def(def_id.to_def_id(), substs)
diff --git a/src/tools/clippy/clippy_lints/src/new_without_default.rs b/src/tools/clippy/clippy_lints/src/new_without_default.rs
index 9419056be14..96c00c205ff 100644
--- a/src/tools/clippy/clippy_lints/src/new_without_default.rs
+++ b/src/tools/clippy/clippy_lints/src/new_without_default.rs
@@ -68,7 +68,7 @@ impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
             ..
         }) = item.kind
         {
-            for assoc_item in items {
+            for assoc_item in *items {
                 if assoc_item.kind == (hir::AssocItemKind::Fn { has_self: false }) {
                     let impl_item = cx.tcx.hir().impl_item(assoc_item.id);
                     if in_external_macro(cx.sess(), impl_item.span) {
diff --git a/src/tools/clippy/clippy_lints/src/partialeq_ne_impl.rs b/src/tools/clippy/clippy_lints/src/partialeq_ne_impl.rs
index e827cdaae87..1469cb434c0 100644
--- a/src/tools/clippy/clippy_lints/src/partialeq_ne_impl.rs
+++ b/src/tools/clippy/clippy_lints/src/partialeq_ne_impl.rs
@@ -42,7 +42,7 @@ impl<'tcx> LateLintPass<'tcx> for PartialEqNeImpl {
             if let Some(eq_trait) = cx.tcx.lang_items().eq_trait();
             if trait_ref.path.res.def_id() == eq_trait;
             then {
-                for impl_item in impl_items {
+                for impl_item in *impl_items {
                     if impl_item.ident.name == sym::ne {
                         span_lint_hir(
                             cx,
diff --git a/src/tools/clippy/clippy_lints/src/serde_api.rs b/src/tools/clippy/clippy_lints/src/serde_api.rs
index 398e2c200de..fc1c2af9257 100644
--- a/src/tools/clippy/clippy_lints/src/serde_api.rs
+++ b/src/tools/clippy/clippy_lints/src/serde_api.rs
@@ -36,7 +36,7 @@ impl<'tcx> LateLintPass<'tcx> for SerdeApi {
                 if did == visit_did {
                     let mut seen_str = None;
                     let mut seen_string = None;
-                    for item in items {
+                    for item in *items {
                         match item.ident.as_str() {
                             "visit_str" => seen_str = Some(item.span),
                             "visit_string" => seen_string = Some(item.span),