Box ItemKind to reduce the size of Item

This brings the size of `Item` from

```
[src/librustdoc/lib.rs:103] std::mem::size_of::<Item>() = 680
```

to

```
[src/librustdoc/lib.rs:103] std::mem::size_of::<Item>() = 280
```

src/librustdoc/clean/auto_trait.rs

@@ -123,7 +123,7 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
                     attrs: Default::default(),
                     visibility: Inherited,
                     def_id: self.cx.next_def_id(param_env_def_id.krate),
-                    kind: ImplItem(Impl {
+                    kind: box ImplItem(Impl {
                         unsafety: hir::Unsafety::Normal,
                         generics: new_generics,
                         provided_trait_methods: Default::default(),

src/librustdoc/clean/blanket_impl.rs

@@ -112,7 +112,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                     attrs: Default::default(),
                     visibility: Inherited,
                     def_id: self.cx.next_def_id(impl_def_id.krate),
-                    kind: ImplItem(Impl {
+                    kind: box ImplItem(Impl {
                         unsafety: hir::Unsafety::Normal,
                         generics: (
                             self.cx.tcx.generics_of(impl_def_id),

src/librustdoc/clean/inline.rs

@@ -482,7 +482,7 @@ fn build_module(cx: &DocContext<'_>, did: DefId, visited: &mut FxHashSet<DefId>)
                         source: clean::Span::dummy(),
                         def_id: DefId::local(CRATE_DEF_INDEX),
                         visibility: clean::Public,
-                        kind: clean::ImportItem(clean::Import::new_simple(
+                        kind: box clean::ImportItem(clean::Import::new_simple(
                             item.ident.name,
                             clean::ImportSource {
                                 path: clean::Path {

src/librustdoc/clean/mod.rs

@@ -2144,7 +2144,7 @@ fn clean_extern_crate(
         source: krate.span.clean(cx),
         def_id: crate_def_id,
         visibility: krate.vis.clean(cx),
-        kind: ExternCrateItem(name, orig_name),
+        kind: box ExternCrateItem(name, orig_name),
     }]
 }
 
@@ -2212,7 +2212,7 @@ impl Clean<Vec<Item>> for doctree::Import<'_> {
                         source: self.span.clean(cx),
                         def_id: cx.tcx.hir().local_def_id(self.id).to_def_id(),
                         visibility: self.vis.clean(cx),
-                        kind: ImportItem(Import::new_simple(
+                        kind: box ImportItem(Import::new_simple(
                             self.name,
                             resolve_use_source(cx, path),
                             false,
@@ -2230,7 +2230,7 @@ impl Clean<Vec<Item>> for doctree::Import<'_> {
             source: self.span.clean(cx),
             def_id: cx.tcx.hir().local_def_id(self.id).to_def_id(),
             visibility: self.vis.clean(cx),
-            kind: ImportItem(inner),
+            kind: box ImportItem(inner),
         }]
     }
 }

src/librustdoc/clean/types.rs

@@ -84,7 +84,7 @@ crate struct Item {
     crate name: Option<Symbol>,
     crate attrs: Attributes,
     crate visibility: Visibility,
-    crate kind: ItemKind,
+    crate kind: Box<ItemKind>,
     crate def_id: DefId,
 }
 
@@ -152,7 +152,7 @@ impl Item {
 
         Item {
             def_id,
-            kind,
+            kind: box kind,
             name,
             source: source.clean(cx),
             attrs: cx.tcx.get_attrs(def_id).clean(cx),
@@ -171,7 +171,7 @@ impl Item {
     }
 
     crate fn is_crate(&self) -> bool {
-        match self.kind {
+        match *self.kind {
             StrippedItem(box ModuleItem(Module { is_crate: true, .. }))
             | ModuleItem(Module { is_crate: true, .. }) => true,
             _ => false,
@@ -223,14 +223,14 @@ impl Item {
         self.type_() == ItemType::Keyword
     }
     crate fn is_stripped(&self) -> bool {
-        match self.kind {
+        match *self.kind {
             StrippedItem(..) => true,
             ImportItem(ref i) => !i.should_be_displayed,
             _ => false,
         }
     }
     crate fn has_stripped_fields(&self) -> Option<bool> {
-        match self.kind {
+        match *self.kind {
             StructItem(ref _struct) => Some(_struct.fields_stripped),
             UnionItem(ref union) => Some(union.fields_stripped),
             VariantItem(Variant { kind: VariantKind::Struct(ref vstruct) }) => {
@@ -281,7 +281,7 @@ impl Item {
     }
 
     crate fn is_default(&self) -> bool {
-        match self.kind {
+        match *self.kind {
             ItemKind::MethodItem(_, Some(defaultness)) => {
                 defaultness.has_value() && !defaultness.is_final()
             }

src/librustdoc/clean/utils.rs

@@ -43,7 +43,7 @@ crate fn krate(mut cx: &mut DocContext<'_>) -> Crate {
     let mut module = module.clean(cx);
     let mut masked_crates = FxHashSet::default();
 
-    match module.kind {
+    match *module.kind {
         ItemKind::ModuleItem(ref module) => {
             for it in &module.items {
                 // `compiler_builtins` should be masked too, but we can't apply
@@ -61,7 +61,7 @@ crate fn krate(mut cx: &mut DocContext<'_>) -> Crate {
 
     let ExternalCrate { name, src, primitives, keywords, .. } = LOCAL_CRATE.clean(cx);
     {
-        let m = match module.kind {
+        let m = match *module.kind {
             ItemKind::ModuleItem(ref mut m) => m,
             _ => unreachable!(),
         };
@@ -338,7 +338,7 @@ crate fn build_deref_target_impls(cx: &DocContext<'_>, items: &[Item], ret: &mut
     let tcx = cx.tcx;
 
     for item in items {
-        let target = match item.kind {
+        let target = match *item.kind {
             ItemKind::TypedefItem(ref t, true) => &t.type_,
             _ => continue,
         };

src/librustdoc/fold.rs

@@ -5,9 +5,9 @@ crate struct StripItem(pub Item);
 impl StripItem {
     crate fn strip(self) -> Option<Item> {
         match self.0 {
-            Item { kind: StrippedItem(..), .. } => Some(self.0),
+            Item { kind: box StrippedItem(..), .. } => Some(self.0),
             mut i => {
-                i.kind = StrippedItem(box i.kind);
+                i.kind = box StrippedItem(i.kind);
                 Some(i)
             }
         }
@@ -72,9 +72,9 @@ crate trait DocFolder: Sized {
 
     /// don't override!
     fn fold_item_recur(&mut self, mut item: Item) -> Item {
-        item.kind = match item.kind {
+        item.kind = box match *item.kind {
             StrippedItem(box i) => StrippedItem(box self.fold_inner_recur(i)),
-            _ => self.fold_inner_recur(item.kind),
+            _ => self.fold_inner_recur(*item.kind),
         };
         item
     }

src/librustdoc/formats/cache.rs

@@ -219,7 +219,7 @@ impl DocFolder for Cache {
 
         // If this is a stripped module,
         // we don't want it or its children in the search index.
-        let orig_stripped_mod = match item.kind {
+        let orig_stripped_mod = match *item.kind {
             clean::StrippedItem(box clean::ModuleItem(..)) => {
                 mem::replace(&mut self.stripped_mod, true)
             }
@@ -228,7 +228,7 @@ impl DocFolder for Cache {
 
         // If the impl is from a masked crate or references something from a
         // masked crate then remove it completely.
-        if let clean::ImplItem(ref i) = item.kind {
+        if let clean::ImplItem(ref i) = *item.kind {
             if self.masked_crates.contains(&item.def_id.krate)
                 || i.trait_.def_id().map_or(false, |d| self.masked_crates.contains(&d.krate))
                 || i.for_.def_id().map_or(false, |d| self.masked_crates.contains(&d.krate))
@@ -239,12 +239,12 @@ impl DocFolder for Cache {
 
         // Propagate a trait method's documentation to all implementors of the
         // trait.
-        if let clean::TraitItem(ref t) = item.kind {
+        if let clean::TraitItem(ref t) = *item.kind {
             self.traits.entry(item.def_id).or_insert_with(|| t.clone());
         }
 
         // Collect all the implementors of traits.
-        if let clean::ImplItem(ref i) = item.kind {
+        if let clean::ImplItem(ref i) = *item.kind {
             if let Some(did) = i.trait_.def_id() {
                 if i.blanket_impl.is_none() {
                     self.implementors
@@ -257,7 +257,7 @@ impl DocFolder for Cache {
 
         // Index this method for searching later on.
         if let Some(ref s) = item.name {
-            let (parent, is_inherent_impl_item) = match item.kind {
+            let (parent, is_inherent_impl_item) = match *item.kind {
                 clean::StrippedItem(..) => ((None, None), false),
                 clean::AssocConstItem(..) | clean::TypedefItem(_, true)
                     if self.parent_is_trait_impl =>
@@ -348,7 +348,7 @@ impl DocFolder for Cache {
             _ => false,
         };
 
-        match item.kind {
+        match *item.kind {
             clean::StructItem(..)
             | clean::EnumItem(..)
             | clean::TypedefItem(..)
@@ -387,7 +387,7 @@ impl DocFolder for Cache {
 
         // Maintain the parent stack
         let orig_parent_is_trait_impl = self.parent_is_trait_impl;
-        let parent_pushed = match item.kind {
+        let parent_pushed = match *item.kind {
             clean::TraitItem(..)
             | clean::EnumItem(..)
             | clean::ForeignTypeItem
@@ -425,21 +425,19 @@ impl DocFolder for Cache {
         // Once we've recursively found all the generics, hoard off all the
         // implementations elsewhere.
         let item = self.fold_item_recur(item);
-        let ret = if let clean::Item { kind: clean::ImplItem(_), .. } = item {
+        let ret = if let clean::Item { kind: box clean::ImplItem(ref i), .. } = item {
             // Figure out the id of this impl. This may map to a
             // primitive rather than always to a struct/enum.
             // Note: matching twice to restrict the lifetime of the `i` borrow.
             let mut dids = FxHashSet::default();
-            if let clean::Item { kind: clean::ImplItem(ref i), .. } = item {
             match i.for_ {
                 clean::ResolvedPath { did, .. }
                 | clean::BorrowedRef { type_: box clean::ResolvedPath { did, .. }, .. } => {
                     dids.insert(did);
                 }
                 ref t => {
-                        let did = t
+                    let did =
-                            .primitive_type()
+                        t.primitive_type().and_then(|t| self.primitive_locations.get(&t).cloned());
-                            .and_then(|t| self.primitive_locations.get(&t).cloned());
 
                     if let Some(did) = did {
                         dids.insert(did);
@@ -454,9 +452,6 @@ impl DocFolder for Cache {
                     }
                 }
             }
-            } else {
-                unreachable!()
-            };
             let impl_item = Impl { impl_item: item };
             if impl_item.trait_did().map_or(true, |d| self.traits.contains_key(&d)) {
                 for did in dids {

src/librustdoc/formats/item_type.rs

@@ -60,7 +60,7 @@ impl Serialize for ItemType {
 
 impl<'a> From<&'a clean::Item> for ItemType {
     fn from(item: &'a clean::Item) -> ItemType {
-        let kind = match item.kind {
+        let kind = match *item.kind {
             clean::StrippedItem(box ref item) => item,
             ref kind => kind,
         };

src/librustdoc/formats/mod.rs

@@ -32,7 +32,7 @@ crate struct Impl {
 
 impl Impl {
     crate fn inner_impl(&self) -> &clean::Impl {
-        match self.impl_item.kind {
+        match *self.impl_item.kind {
             clean::ImplItem(ref impl_) => impl_,
             _ => panic!("non-impl item found in impl"),
         }

src/librustdoc/formats/renderer.rs

@@ -89,7 +89,7 @@ crate fn run_format<'tcx, T: FormatRenderer<'tcx>>(
             }
 
             cx.mod_item_in(&item, &name, &cache)?;
-            let module = match item.kind {
+            let module = match *item.kind {
                 clean::StrippedItem(box clean::ModuleItem(m)) | clean::ModuleItem(m) => m,
                 _ => unreachable!(),
             };

src/librustdoc/html/render/cache.rs

@@ -165,7 +165,7 @@ crate fn build_index(krate: &clean::Crate, cache: &mut Cache) -> String {
 }
 
 crate fn get_index_search_type(item: &clean::Item) -> Option<IndexItemFunctionType> {
-    let (all_types, ret_types) = match item.kind {
+    let (all_types, ret_types) = match *item.kind {
         clean::FunctionItem(ref f) => (&f.all_types, &f.ret_types),
         clean::MethodItem(ref m, _) => (&m.all_types, &m.ret_types),
         clean::TyMethodItem(ref m) => (&m.all_types, &m.ret_types),

src/librustdoc/html/render/mod.rs

@@ -633,7 +633,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
 
         // Render sidebar-items.js used throughout this module.
         if !self.render_redirect_pages {
-            let module = match item.kind {
+            let module = match *item.kind {
                 clean::StrippedItem(box clean::ModuleItem(ref m)) | clean::ModuleItem(ref m) => m,
                 _ => unreachable!(),
             };
@@ -1739,7 +1739,7 @@ fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut Buffer, cache: &Ca
 
     write!(buf, "</span>"); // out-of-band
     write!(buf, "<span class=\"in-band\">");
-    let name = match item.kind {
+    let name = match *item.kind {
         clean::ModuleItem(ref m) => {
             if m.is_crate {
                 "Crate "
@@ -1788,7 +1788,7 @@ fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut Buffer, cache: &Ca
 
     write!(buf, "</span></h1>"); // in-band
 
-    match item.kind {
+    match *item.kind {
         clean::ModuleItem(ref m) => item_module(buf, cx, item, &m.items),
         clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) => {
             item_function(buf, cx, item, f)
@@ -2149,7 +2149,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
             );
         }
 
-        match myitem.kind {
+        match *myitem.kind {
             clean::ExternCrateItem(ref name, ref src) => {
                 use crate::html::format::anchor;
 
@@ -2185,7 +2185,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
                     continue;
                 }
 
-                let unsafety_flag = match myitem.kind {
+                let unsafety_flag = match *myitem.kind {
                     clean::FunctionItem(ref func) | clean::ForeignFunctionItem(ref func)
                         if func.header.unsafety == hir::Unsafety::Unsafe =>
                     {
@@ -2624,7 +2624,7 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
             }
             for (pos, m) in provided.iter().enumerate() {
                 render_assoc_item(w, m, AssocItemLink::Anchor(None), ItemType::Trait, cx);
-                match m.kind {
+                match *m.kind {
                     clean::MethodItem(ref inner, _)
                         if !inner.generics.where_predicates.is_empty() =>
                     {
@@ -3051,7 +3051,7 @@ fn render_assoc_item(
             where_clause = WhereClause { gens: g, indent, end_newline }
         )
     }
-    match item.kind {
+    match *item.kind {
         clean::StrippedItem(..) => {}
         clean::TyMethodItem(ref m) => {
             method(w, item, m.header, &m.generics, &m.decl, link, parent, cx)
@@ -3098,7 +3098,7 @@ fn item_struct(
     let mut fields = s
         .fields
         .iter()
-        .filter_map(|f| match f.kind {
+        .filter_map(|f| match *f.kind {
             clean::StructFieldItem(ref ty) => Some((f, ty)),
             _ => None,
         })
@@ -3148,7 +3148,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
     let mut fields = s
         .fields
         .iter()
-        .filter_map(|f| match f.kind {
+        .filter_map(|f| match *f.kind {
             clean::StructFieldItem(ref ty) => Some((f, ty)),
             _ => None,
         })
@@ -3201,7 +3201,7 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
             for v in &e.variants {
                 write!(w, "    ");
                 let name = v.name.as_ref().unwrap();
-                match v.kind {
+                match *v.kind {
                     clean::VariantItem(ref var) => match var.kind {
                         clean::VariantKind::CLike => write!(w, "{}", name),
                         clean::VariantKind::Tuple(ref tys) => {
@@ -3251,7 +3251,7 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
                 id = id,
                 name = variant.name.as_ref().unwrap()
             );
-            if let clean::VariantItem(ref var) = variant.kind {
+            if let clean::VariantItem(ref var) = *variant.kind {
                 if let clean::VariantKind::Tuple(ref tys) = var.kind {
                     write!(w, "(");
                     for (i, ty) in tys.iter().enumerate() {
@@ -3268,7 +3268,8 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
             document_non_exhaustive(w, variant);
 
             use crate::clean::{Variant, VariantKind};
-            if let clean::VariantItem(Variant { kind: VariantKind::Struct(ref s) }) = variant.kind {
+            if let clean::VariantItem(Variant { kind: VariantKind::Struct(ref s) }) = *variant.kind
+            {
                 let variant_id = cx.derive_id(format!(
                     "{}.{}.fields",
                     ItemType::Variant,
@@ -3282,7 +3283,7 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
                 );
                 for field in &s.fields {
                     use crate::clean::StructFieldItem;
-                    if let StructFieldItem(ref ty) = field.kind {
+                    if let StructFieldItem(ref ty) = *field.kind {
                         let id = cx.derive_id(format!(
                             "variant.{}.field.{}",
                             variant.name.as_ref().unwrap(),
@@ -3379,7 +3380,7 @@ fn render_struct(
             let mut has_visible_fields = false;
             write!(w, " {{");
             for field in fields {
-                if let clean::StructFieldItem(ref ty) = field.kind {
+                if let clean::StructFieldItem(ref ty) = *field.kind {
                     write!(
                         w,
                         "\n{}    {}{}: {},",
@@ -3410,7 +3411,7 @@ fn render_struct(
                 if i > 0 {
                     write!(w, ", ");
                 }
-                match field.kind {
+                match *field.kind {
                     clean::StrippedItem(box clean::StructFieldItem(..)) => write!(w, "_"),
                     clean::StructFieldItem(ref ty) => {
                         write!(w, "{}{}", field.visibility.print_with_space(cx.tcx()), ty.print())
@@ -3457,7 +3458,7 @@ fn render_union(
 
     write!(w, " {{\n{}", tab);
     for field in fields {
-        if let clean::StructFieldItem(ref ty) = field.kind {
+        if let clean::StructFieldItem(ref ty) = *field.kind {
             write!(
                 w,
                 "    {}{}: {},\n{}",
@@ -3619,7 +3620,7 @@ fn render_deref_methods(
         .inner_impl()
         .items
         .iter()
-        .find_map(|item| match item.kind {
+        .find_map(|item| match *item.kind {
             clean::TypedefItem(ref t, true) => Some(match *t {
                 clean::Typedef { item_type: Some(ref type_), .. } => (type_, &t.type_),
                 _ => (&t.type_, &t.type_),
@@ -3641,7 +3642,7 @@ fn render_deref_methods(
 }
 
 fn should_render_item(item: &clean::Item, deref_mut_: bool) -> bool {
-    let self_type_opt = match item.kind {
+    let self_type_opt = match *item.kind {
         clean::MethodItem(ref method, _) => method.decl.self_type(),
         clean::TyMethodItem(ref method) => method.decl.self_type(),
         _ => None,
@@ -3692,7 +3693,7 @@ fn spotlight_decl(decl: &clean::FnDecl) -> String {
                     ));
                     let t_did = impl_.trait_.def_id().unwrap();
                     for it in &impl_.items {
-                        if let clean::TypedefItem(ref tydef, _) = it.kind {
+                        if let clean::TypedefItem(ref tydef, _) = *it.kind {
                             out.push_str("<span class=\"where fmt-newline\">    ");
                             assoc_type(
                                 &mut out,
@@ -3764,7 +3765,7 @@ fn render_impl(
             fmt_impl_for_trait_page(&i.inner_impl(), w, use_absolute);
             if show_def_docs {
                 for it in &i.inner_impl().items {
-                    if let clean::TypedefItem(ref tydef, _) = it.kind {
+                    if let clean::TypedefItem(ref tydef, _) = *it.kind {
                         write!(w, "<span class=\"where fmt-newline\">  ");
                         assoc_type(w, it, &[], Some(&tydef.type_), AssocItemLink::Anchor(None), "");
                         write!(w, ";</span>");
@@ -3846,7 +3847,7 @@ fn render_impl(
             } else {
                 (true, " hidden")
             };
-        match item.kind {
+        match *item.kind {
             clean::MethodItem(..) | clean::TyMethodItem(_) => {
                 // Only render when the method is not static or we allow static methods
                 if render_method_item {
@@ -4123,7 +4124,7 @@ fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Buffer, cache:
         write!(
             buffer,
             "<p class=\"location\">{}{}</p>",
-            match it.kind {
+            match *it.kind {
                 clean::StructItem(..) => "Struct ",
                 clean::TraitItem(..) => "Trait ",
                 clean::PrimitiveItem(..) => "Primitive Type ",
@@ -4163,7 +4164,7 @@ fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Buffer, cache:
             it.name.as_ref().expect("crates always have a name")
         );
     }
-    match it.kind {
+    match *it.kind {
         clean::StructItem(ref s) => sidebar_struct(buffer, it, s),
         clean::TraitItem(ref t) => sidebar_trait(buffer, it, t),
         clean::PrimitiveItem(_) => sidebar_primitive(buffer, it),
@@ -4303,7 +4304,7 @@ fn sidebar_assoc_items(it: &clean::Item) -> String {
                 .find(|i| i.inner_impl().trait_.def_id() == c.deref_trait_did)
             {
                 if let Some((target, real_target)) =
-                    impl_.inner_impl().items.iter().find_map(|item| match item.kind {
+                    impl_.inner_impl().items.iter().find_map(|item| match *item.kind {
                         clean::TypedefItem(ref t, true) => Some(match *t {
                             clean::Typedef { item_type: Some(ref type_), .. } => (type_, &t.type_),
                             _ => (&t.type_, &t.type_),
@@ -4442,7 +4443,7 @@ fn get_id_for_impl_on_foreign_type(for_: &clean::Type, trait_: &clean::Type) ->
 }
 
 fn extract_for_impl_name(item: &clean::Item) -> Option<(String, String)> {
-    match item.kind {
+    match *item.kind {
         clean::ItemKind::ImplItem(ref i) => {
             if let Some(ref trait_) = i.trait_ {
                 Some((
@@ -4593,7 +4594,7 @@ fn sidebar_typedef(buf: &mut Buffer, it: &clean::Item) {
 fn get_struct_fields_name(fields: &[clean::Item]) -> String {
     let mut fields = fields
         .iter()
-        .filter(|f| if let clean::StructFieldItem(..) = f.kind { true } else { false })
+        .filter(|f| matches!(*f.kind, clean::StructFieldItem(..)))
         .filter_map(|f| match f.name {
             Some(ref name) => {
                 Some(format!("<a href=\"#structfield.{name}\">{name}</a>", name = name))

src/librustdoc/json/conversions.rs

@@ -19,9 +19,9 @@ impl JsonRenderer<'_> {
         let item_type = ItemType::from(&item);
         let deprecation = item.deprecation(self.tcx);
         let clean::Item { source, name, attrs, kind, visibility, def_id } = item;
-        match kind {
+        match *kind {
             clean::StrippedItem(_) => None,
-            _ => Some(Item {
+            kind => Some(Item {
                 id: def_id.into(),
                 crate_id: def_id.krate.as_u32(),
                 name: name.map(|sym| sym.to_string()),

src/librustdoc/json/mod.rs

@@ -178,9 +178,9 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
         cache: &Cache,
     ) -> Result<(), Error> {
         use clean::types::ItemKind::*;
-        if let ModuleItem(m) = &item.kind {
+        if let ModuleItem(m) = &*item.kind {
             for item in &m.items {
-                match &item.kind {
+                match &*item.kind {
                     // These don't have names so they don't get added to the output by default
                     ImportItem(_) => self.item(item.clone(), cache).unwrap(),
                     ExternCrateItem(_, _) => self.item(item.clone(), cache).unwrap(),

src/librustdoc/passes/calculate_doc_coverage.rs

@@ -187,7 +187,7 @@ impl<'a, 'b> CoverageCalculator<'a, 'b> {
 
 impl<'a, 'b> fold::DocFolder for CoverageCalculator<'a, 'b> {
     fn fold_item(&mut self, i: clean::Item) -> Option<clean::Item> {
-        match i.kind {
+        match *i.kind {
             _ if !i.def_id.is_local() => {
                 // non-local items are skipped because they can be out of the users control,
                 // especially in the case of trait impls, which rustdoc eagerly inlines

src/librustdoc/passes/collect_trait_impls.rs

@@ -58,11 +58,11 @@ crate fn collect_trait_impls(krate: Crate, cx: &DocContext<'_>) -> Crate {
 
     // scan through included items ahead of time to splice in Deref targets to the "valid" sets
     for it in &new_items {
-        if let ImplItem(Impl { ref for_, ref trait_, ref items, .. }) = it.kind {
+        if let ImplItem(Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
             if cleaner.keep_item(for_) && trait_.def_id() == cx.tcx.lang_items().deref_trait() {
                 let target = items
                     .iter()
-                    .find_map(|item| match item.kind {
+                    .find_map(|item| match *item.kind {
                         TypedefItem(ref t, true) => Some(&t.type_),
                         _ => None,
                     })
@@ -78,7 +78,7 @@ crate fn collect_trait_impls(krate: Crate, cx: &DocContext<'_>) -> Crate {
     }
 
     new_items.retain(|it| {
-        if let ImplItem(Impl { ref for_, ref trait_, ref blanket_impl, .. }) = it.kind {
+        if let ImplItem(Impl { ref for_, ref trait_, ref blanket_impl, .. }) = *it.kind {
             cleaner.keep_item(for_)
                 || trait_.as_ref().map_or(false, |t| cleaner.keep_item(t))
                 || blanket_impl.is_some()
@@ -124,7 +124,7 @@ crate fn collect_trait_impls(krate: Crate, cx: &DocContext<'_>) -> Crate {
     }
 
     if let Some(ref mut it) = krate.module {
-        if let ModuleItem(Module { ref mut items, .. }) = it.kind {
+        if let ModuleItem(Module { ref mut items, .. }) = *it.kind {
             items.extend(synth.impls);
             items.extend(new_items);
         } else {

src/librustdoc/passes/doc_test_lints.rs

@@ -59,7 +59,7 @@ impl crate::doctest::Tester for Tests {
 
 crate fn should_have_doc_example(cx: &DocContext<'_>, item: &clean::Item) -> bool {
     if matches!(
-        item.kind,
+        *item.kind,
         clean::StructFieldItem(_)
             | clean::VariantItem(_)
             | clean::AssocConstItem(_, _)

src/librustdoc/passes/strip_hidden.rs

@@ -41,7 +41,7 @@ impl<'a> DocFolder for Stripper<'a> {
         if i.attrs.lists(sym::doc).has_word(sym::hidden) {
             debug!("strip_hidden: stripping {:?} {:?}", i.type_(), i.name);
             // use a dedicated hidden item for given item type if any
-            match i.kind {
+            match *i.kind {
                 clean::StructFieldItem(..) | clean::ModuleItem(..) => {
                     // We need to recurse into stripped modules to
                     // strip things like impl methods but when doing so

src/librustdoc/passes/stripper.rs

@@ -13,7 +13,7 @@ crate struct Stripper<'a> {
 
 impl<'a> DocFolder for Stripper<'a> {
     fn fold_item(&mut self, i: Item) -> Option<Item> {
-        match i.kind {
+        match *i.kind {
             clean::StrippedItem(..) => {
                 // We need to recurse into stripped modules to strip things
                 // like impl methods but when doing so we must not add any
@@ -86,7 +86,7 @@ impl<'a> DocFolder for Stripper<'a> {
             clean::KeywordItem(..) => {}
         }
 
-        let fastreturn = match i.kind {
+        let fastreturn = match *i.kind {
             // nothing left to do for traits (don't want to filter their
             // methods out, visibility controlled by the trait)
             clean::TraitItem(..) => true,
@@ -121,7 +121,7 @@ crate struct ImplStripper<'a> {
 
 impl<'a> DocFolder for ImplStripper<'a> {
     fn fold_item(&mut self, i: Item) -> Option<Item> {
-        if let clean::ImplItem(ref imp) = i.kind {
+        if let clean::ImplItem(ref imp) = *i.kind {
             // emptied none trait impls can be stripped
             if imp.trait_.is_none() && imp.items.is_empty() {
                 return None;
@@ -160,7 +160,7 @@ crate struct ImportStripper;
 
 impl DocFolder for ImportStripper {
     fn fold_item(&mut self, i: Item) -> Option<Item> {
-        match i.kind {
+        match *i.kind {
             clean::ExternCrateItem(..) | clean::ImportItem(..) if !i.visibility.is_public() => None,
             _ => Some(self.fold_item_recur(i)),
         }