Box the biggest ast::ItemKind variants

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -527,12 +527,12 @@ impl<'a> TraitDef<'a> {
                     tokens: None,
                 },
                 attrs: Vec::new(),
-                kind: ast::AssocItemKind::TyAlias(
+                kind: ast::AssocItemKind::TyAlias(box ast::TyAliasKind(
                     ast::Defaultness::Final,
                     Generics::default(),
                     Vec::new(),
                     Some(type_def.to_ty(cx, self.span, type_ident, generics)),
-                ),
+                )),
                 tokens: None,
             })
         });
@@ -687,7 +687,7 @@ impl<'a> TraitDef<'a> {
             self.span,
             Ident::invalid(),
             a,
-            ast::ItemKind::Impl {
+            ast::ItemKind::Impl(box ast::ImplKind {
                 unsafety,
                 polarity: ast::ImplPolarity::Positive,
                 defaultness: ast::Defaultness::Final,
@@ -696,7 +696,7 @@ impl<'a> TraitDef<'a> {
                 of_trait: opt_trait_ref,
                 self_ty: self_type,
                 items: methods.into_iter().chain(associated_types).collect(),
-            },
+            }),
         )
     }
 
@@ -929,7 +929,7 @@ impl<'a> MethodDef<'a> {
                 tokens: None,
             },
             ident: method_ident,
-            kind: ast::AssocItemKind::Fn(def, sig, fn_generics, Some(body_block)),
+            kind: ast::AssocItemKind::Fn(box ast::FnKind(def, sig, fn_generics, Some(body_block))),
             tokens: None,
         })
     }

compiler/rustc_builtin_macros/src/deriving/mod.rs

@@ -2,7 +2,7 @@
 
 use rustc_ast as ast;
 use rustc_ast::ptr::P;
-use rustc_ast::{ItemKind, MetaItem};
+use rustc_ast::{ImplKind, ItemKind, MetaItem};
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, MultiItemModifier};
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::Span;
@@ -179,7 +179,7 @@ fn inject_impl_of_structural_trait(
         span,
         Ident::invalid(),
         attrs,
-        ItemKind::Impl {
+        ItemKind::Impl(box ImplKind {
             unsafety: ast::Unsafe::No,
             polarity: ast::ImplPolarity::Positive,
             defaultness: ast::Defaultness::Final,
@@ -188,7 +188,7 @@ fn inject_impl_of_structural_trait(
             of_trait: Some(trait_ref),
             self_ty: self_type,
             items: Vec::new(),
-        },
+        }),
     );
 
     push(Annotatable::Item(newitem));