Box ItemKind::Impl

compiler/rustc_ast_lowering/src/item.rs

@@ -134,7 +134,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let old_len = self.in_scope_lifetimes.len();
 
         let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
-            hir::ItemKind::Impl { ref generics, .. }
+            hir::ItemKind::Impl(box hir::Impl { ref generics, .. })
             | hir::ItemKind::Trait(_, _, ref generics, ..) => &generics.params[..],
             _ => &[],
         };
@@ -431,7 +431,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 // to not cause an assertion failure inside the `lower_defaultness` function.
                 let has_val = true;
                 let (defaultness, defaultness_span) = self.lower_defaultness(defaultness, has_val);
-                hir::ItemKind::Impl {
+                hir::ItemKind::Impl(box hir::Impl {
                     unsafety: self.lower_unsafety(unsafety),
                     polarity,
                     defaultness,
@@ -441,7 +441,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     of_trait: trait_ref,
                     self_ty: lowered_ty,
                     items: new_impl_items,
-                }
+                })
             }
             ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
                 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());

compiler/rustc_ast_lowering/src/lib.rs

@@ -31,6 +31,8 @@
 //! in the HIR, especially for multiple identifiers.
 
 #![feature(array_value_iter)]
+#![feature(box_patterns)]
+#![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
 #![feature(or_patterns)]
 #![recursion_limit = "256"]

compiler/rustc_hir/src/hir.rs

@@ -2562,22 +2562,28 @@ pub enum ItemKind<'hir> {
     TraitAlias(Generics<'hir>, GenericBounds<'hir>),
 
     /// An implementation, e.g., `impl<A> Trait for Foo { .. }`.
-    Impl {
-        unsafety: Unsafety,
-        polarity: ImplPolarity,
-        defaultness: Defaultness,
-        // We do not put a `Span` in `Defaultness` because it breaks foreign crate metadata
-        // decoding as `Span`s cannot be decoded when a `Session` is not available.
-        defaultness_span: Option<Span>,
-        constness: Constness,
-        generics: Generics<'hir>,
-
-        /// The trait being implemented, if any.
-        of_trait: Option<TraitRef<'hir>>,
-
-        self_ty: &'hir Ty<'hir>,
-        items: &'hir [ImplItemRef<'hir>],
-    },
+    Impl(Box<Impl<'hir>>),
+}
+
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(ItemKind<'_>, 88);
+
+#[derive(Debug, HashStable_Generic)]
+pub struct Impl<'hir> {
+    pub unsafety: Unsafety,
+    pub polarity: ImplPolarity,
+    pub defaultness: Defaultness,
+    // We do not put a `Span` in `Defaultness` because it breaks foreign crate metadata
+    // 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>,
+
+    /// The trait being implemented, if any.
+    pub of_trait: Option<TraitRef<'hir>>,
+
+    pub self_ty: &'hir Ty<'hir>,
+    pub items: &'hir [ImplItemRef<'hir>],
 }
 
 impl ItemKind<'_> {
@@ -2590,7 +2596,7 @@ impl ItemKind<'_> {
             | ItemKind::Struct(_, ref generics)
             | ItemKind::Union(_, ref generics)
             | ItemKind::Trait(_, _, ref generics, _, _)
-            | ItemKind::Impl { ref generics, .. } => generics,
+            | ItemKind::Impl(box Impl { ref generics, .. }) => generics,
             _ => return None,
         })
     }

compiler/rustc_hir/src/intravisit.rs

@@ -611,7 +611,7 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) {
             // `visit_enum_def()` takes care of visiting the `Item`'s `HirId`.
             visitor.visit_enum_def(enum_definition, generics, item.hir_id, item.span)
         }
-        ItemKind::Impl {
+        ItemKind::Impl(box Impl {
             unsafety: _,
             defaultness: _,
             polarity: _,
@@ -621,7 +621,7 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) {
             ref of_trait,
             ref self_ty,
             items,
-        } => {
+        }) => {
             visitor.visit_id(item.hir_id);
             visitor.visit_generics(generics);
             walk_list!(visitor, visit_trait_ref, of_trait);

compiler/rustc_hir/src/lib.rs

@@ -3,6 +3,7 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
 
 #![feature(array_value_iter)]
+#![feature(box_patterns)]
 #![feature(crate_visibility_modifier)]
 #![feature(const_fn)] // For the unsizing cast on `&[]`
 #![feature(const_panic)]

compiler/rustc_hir_pretty/src/lib.rs

@@ -1,3 +1,4 @@
+#![feature(box_patterns)]
 #![feature(or_patterns)]
 #![recursion_limit = "256"]
 
@@ -684,7 +685,7 @@ impl<'a> State<'a> {
                 self.head(visibility_qualified(&item.vis, "union"));
                 self.print_struct(struct_def, generics, item.ident.name, item.span, true);
             }
-            hir::ItemKind::Impl {
+            hir::ItemKind::Impl(box hir::Impl {
                 unsafety,
                 polarity,
                 defaultness,
@@ -694,7 +695,7 @@ impl<'a> State<'a> {
                 ref of_trait,
                 ref self_ty,
                 items,
-            } => {
+            }) => {
                 self.head("");
                 self.print_visibility(&item.vis);
                 self.print_defaultness(defaultness);

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -345,9 +345,10 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         match tcx.hir().get_if_local(def_id) {
             Some(Node::ImplItem(ImplItem { ident, hir_id, .. })) => {
                 match tcx.hir().find(tcx.hir().get_parent_item(*hir_id)) {
-                    Some(Node::Item(Item { kind: ItemKind::Impl { self_ty, .. }, .. })) => {
-                        Some((*ident, self_ty))
-                    }
+                    Some(Node::Item(Item {
+                        kind: ItemKind::Impl(box hir::Impl { self_ty, .. }),
+                        ..
+                    })) => Some((*ident, self_ty)),
                     _ => None,
                 }
             }
@@ -367,7 +368,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                                 let impl_did = tcx.hir().local_def_id(*impl_node);
                                 match tcx.hir().get_if_local(impl_did.to_def_id()) {
                                     Some(Node::Item(Item {
-                                        kind: ItemKind::Impl { self_ty, .. },
+                                        kind: ItemKind::Impl(box hir::Impl { self_ty, .. }),
                                         ..
                                     })) if trait_objects.iter().all(|did| {
                                         // FIXME: we should check `self_ty` against the receiver

compiler/rustc_lint/src/builtin.rs

@@ -542,7 +542,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
                     return;
                 }
             }
-            hir::ItemKind::Impl { of_trait: Some(ref trait_ref), items, .. } => {
+            hir::ItemKind::Impl(box hir::Impl { of_trait: Some(ref trait_ref), items, .. }) => {
                 // If the trait is private, add the impl items to `private_traits` so they don't get
                 // reported for missing docs.
                 let real_trait = trait_ref.path.res.def_id();

compiler/rustc_lint/src/lib.rs

@@ -29,6 +29,7 @@
 #![cfg_attr(test, feature(test))]
 #![feature(array_windows)]
 #![feature(bool_to_option)]
+#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
 #![feature(iter_order_by)]

compiler/rustc_metadata/src/lib.rs

@@ -1,4 +1,5 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
+#![feature(box_patterns)]
 #![feature(core_intrinsics)]
 #![feature(crate_visibility_modifier)]
 #![feature(drain_filter)]

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1283,7 +1283,7 @@ impl EncodeContext<'a, 'tcx> {
                     is_non_exhaustive: variant.is_field_list_non_exhaustive(),
                 }), adt_def.repr)
             }
-            hir::ItemKind::Impl { defaultness, .. } => {
+            hir::ItemKind::Impl(box hir::Impl { defaultness, .. }) => {
                 let trait_ref = self.tcx.impl_trait_ref(def_id);
                 let polarity = self.tcx.impl_polarity(def_id);
                 let parent = if let Some(trait_ref) = trait_ref {

compiler/rustc_middle/src/hir/map/mod.rs

@@ -505,7 +505,7 @@ impl<'hir> Map<'hir> {
                     | ItemKind::Union(_, generics)
                     | ItemKind::Trait(_, _, generics, ..)
                     | ItemKind::TraitAlias(generics, _)
-                    | ItemKind::Impl { generics, .. },
+                    | ItemKind::Impl(box Impl { generics, .. }),
                 ..
             }) => Some(generics),
             _ => None,

compiler/rustc_middle/src/ty/error.rs

@@ -829,7 +829,8 @@ fn foo(&self) -> Self::T { String::new() }
                 }
             }
             Some(hir::Node::Item(hir::Item {
-                kind: hir::ItemKind::Impl { items, .. }, ..
+                kind: hir::ItemKind::Impl(box hir::Impl { items, .. }),
+                ..
             })) => {
                 for item in &items[..] {
                     if let hir::AssocItemKind::Type = item.kind {

compiler/rustc_mir/src/const_eval/fn_queries.rs

@@ -126,7 +126,7 @@ fn is_const_impl_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
     matches!(
         node,
         hir::Node::Item(hir::Item {
-            kind: hir::ItemKind::Impl { constness: hir::Constness::Const, .. },
+            kind: hir::ItemKind::Impl(box hir::Impl { constness: hir::Constness::Const, .. }),
             ..
         })
     )

compiler/rustc_mir/src/monomorphize/collector.rs

@@ -1146,8 +1146,8 @@ fn create_mono_items_for_default_impls<'tcx>(
     output: &mut Vec<Spanned<MonoItem<'tcx>>>,
 ) {
     match item.kind {
-        hir::ItemKind::Impl { ref generics, ref items, .. } => {
-            for param in generics.params {
+        hir::ItemKind::Impl(ref impl_) => {
+            for param in impl_.generics.params {
                 match param.kind {
                     hir::GenericParamKind::Lifetime { .. } => {}
                     hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => {
@@ -1167,7 +1167,7 @@ fn create_mono_items_for_default_impls<'tcx>(
                 let param_env = ty::ParamEnv::reveal_all();
                 let trait_ref = tcx.normalize_erasing_regions(param_env, trait_ref);
                 let overridden_methods: FxHashSet<_> =
-                    items.iter().map(|iiref| iiref.ident.normalize_to_macros_2_0()).collect();
+                    impl_.items.iter().map(|iiref| iiref.ident.normalize_to_macros_2_0()).collect();
                 for method in tcx.provided_trait_methods(trait_ref.def_id) {
                     if overridden_methods.contains(&method.ident.normalize_to_macros_2_0()) {
                         continue;

compiler/rustc_passes/src/check_attr.rs

@@ -32,7 +32,7 @@ pub(crate) fn target_from_impl_item<'tcx>(
             let parent_hir_id = tcx.hir().get_parent_item(impl_item.hir_id);
             let containing_item = tcx.hir().expect_item(parent_hir_id);
             let containing_impl_is_for_trait = match &containing_item.kind {
-                hir::ItemKind::Impl { ref of_trait, .. } => of_trait.is_some(),
+                hir::ItemKind::Impl(impl_) => impl_.of_trait.is_some(),
                 _ => bug!("parent of an ImplItem must be an Impl"),
             };
             if containing_impl_is_for_trait {
@@ -343,7 +343,7 @@ impl CheckAttrVisitor<'tcx> {
                 // We can't link to trait impl's consts.
                 let err = "associated constant in trait implementation block";
                 match containing_item.kind {
-                    ItemKind::Impl { of_trait: Some(_), .. } => Some(err),
+                    ItemKind::Impl(box hir::Impl { of_trait: Some(_), .. }) => Some(err),
                     _ => None,
                 }
             }

compiler/rustc_passes/src/dead.rs

@@ -396,7 +396,7 @@ impl<'v, 'k, 'tcx> ItemLikeVisitor<'v> for LifeSeeder<'k, 'tcx> {
                     }
                 }
             }
-            hir::ItemKind::Impl { ref of_trait, items, .. } => {
+            hir::ItemKind::Impl(box hir::Impl { ref of_trait, items, .. }) => {
                 if of_trait.is_some() {
                     self.worklist.push(item.hir_id);
                 }

compiler/rustc_passes/src/lib.rs

@@ -5,6 +5,7 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
+#![feature(box_patterns)]
 #![feature(const_fn)]
 #![feature(const_panic)]
 #![feature(crate_visibility_modifier)]

compiler/rustc_passes/src/reachable.rs

@@ -349,7 +349,10 @@ impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a, 'tcx
         }
 
         // We need only trait impls here, not inherent impls, and only non-exported ones
-        if let hir::ItemKind::Impl { of_trait: Some(ref trait_ref), ref items, .. } = item.kind {
+        if let hir::ItemKind::Impl(box hir::Impl {
+            of_trait: Some(ref trait_ref), ref items, ..
+        }) = item.kind
+        {
             if !self.access_levels.is_reachable(item.hir_id) {
                 // FIXME(#53488) remove `let`
                 let tcx = self.tcx;

compiler/rustc_passes/src/stability.rs

@@ -330,11 +330,12 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             // they don't have their own stability. They still can be annotated as unstable
             // and propagate this unstability to children, but this annotation is completely
             // optional. They inherit stability from their parents when unannotated.
-            hir::ItemKind::Impl { of_trait: None, .. } | hir::ItemKind::ForeignMod { .. } => {
+            hir::ItemKind::Impl(box hir::Impl { of_trait: None, .. })
+            | hir::ItemKind::ForeignMod { .. } => {
                 self.in_trait_impl = false;
                 kind = AnnotationKind::Container;
             }
-            hir::ItemKind::Impl { of_trait: Some(_), .. } => {
+            hir::ItemKind::Impl(box hir::Impl { of_trait: Some(_), .. }) => {
                 self.in_trait_impl = true;
                 kind = AnnotationKind::DeprecationProhibited;
             }
@@ -503,7 +504,7 @@ impl<'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'tcx> {
         // optional. They inherit stability from their parents when unannotated.
         if !matches!(
             i.kind,
-            hir::ItemKind::Impl { of_trait: None, .. } | hir::ItemKind::ForeignMod { .. }
+            hir::ItemKind::Impl(box hir::Impl { of_trait: None, .. }) | hir::ItemKind::ForeignMod { .. }
         ) {
             self.check_missing_stability(i.hir_id, i.span);
         }
@@ -672,7 +673,9 @@ impl Visitor<'tcx> for Checker<'tcx> {
             // For implementations of traits, check the stability of each item
             // individually as it's possible to have a stable trait with unstable
             // items.
-            hir::ItemKind::Impl { of_trait: Some(ref t), self_ty, items, .. } => {
+            hir::ItemKind::Impl(box hir::Impl {
+                of_trait: Some(ref t), self_ty, items, ..
+            }) => {
                 if self.tcx.features().staged_api {
                     // If this impl block has an #[unstable] attribute, give an
                     // error if all involved types and traits are stable, because