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));

compiler/rustc_builtin_macros/src/global_allocator.rs

@@ -5,7 +5,7 @@ use rustc_ast::expand::allocator::{
 };
 use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, Attribute, Expr, FnHeader, FnSig, Generics, Param, StmtKind};
-use rustc_ast::{ItemKind, Mutability, Stmt, Ty, TyKind, Unsafe};
+use rustc_ast::{FnKind, ItemKind, Mutability, Stmt, Ty, TyKind, Unsafe};
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
@@ -85,7 +85,8 @@ impl AllocFnFactory<'_, '_> {
         let header = FnHeader { unsafety: Unsafe::Yes(self.span), ..FnHeader::default() };
         let sig = FnSig { decl, header, span: self.span };
         let block = Some(self.cx.block_expr(output_expr));
-        let kind = ItemKind::Fn(ast::Defaultness::Final, sig, Generics::default(), block);
+        let kind =
+            ItemKind::Fn(box FnKind(ast::Defaultness::Final, sig, Generics::default(), block));
         let item = self.cx.item(
             self.span,
             Ident::from_str_and_span(&self.kind.fn_name(method.name), self.span),

compiler/rustc_builtin_macros/src/lib.rs

@@ -2,6 +2,8 @@
 //! injecting code into the crate before it is lowered to HIR.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
+#![feature(box_patterns)]
+#![feature(box_syntax)]
 #![feature(bool_to_option)]
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]

compiler/rustc_builtin_macros/src/test.rs

@@ -425,7 +425,7 @@ fn test_type(cx: &ExtCtxt<'_>) -> TestType {
 fn has_test_signature(cx: &ExtCtxt<'_>, i: &ast::Item) -> bool {
     let has_should_panic_attr = cx.sess.contains_name(&i.attrs, sym::should_panic);
     let sd = &cx.sess.parse_sess.span_diagnostic;
-    if let ast::ItemKind::Fn(_, ref sig, ref generics, _) = i.kind {
+    if let ast::ItemKind::Fn(box ast::FnKind(_, ref sig, ref generics, _)) = i.kind {
         if let ast::Unsafe::Yes(span) = sig.header.unsafety {
             sd.struct_span_err(i.span, "unsafe functions cannot be used for tests")
                 .span_label(span, "`unsafe` because of this")
@@ -474,7 +474,7 @@ fn has_test_signature(cx: &ExtCtxt<'_>, i: &ast::Item) -> bool {
 }
 
 fn has_bench_signature(cx: &ExtCtxt<'_>, i: &ast::Item) -> bool {
-    let has_sig = if let ast::ItemKind::Fn(_, ref sig, _, _) = i.kind {
+    let has_sig = if let ast::ItemKind::Fn(box ast::FnKind(_, ref sig, _, _)) = i.kind {
         // N.B., inadequate check, but we're running
         // well before resolve, can't get too deep.
         sig.decl.inputs.len() == 1

compiler/rustc_builtin_macros/src/test_harness.rs

@@ -311,7 +311,8 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
     let decl = ecx.fn_decl(vec![], ast::FnRetTy::Ty(main_ret_ty));
     let sig = ast::FnSig { decl, header: ast::FnHeader::default(), span: sp };
     let def = ast::Defaultness::Final;
-    let main = ast::ItemKind::Fn(def, sig, ast::Generics::default(), Some(main_body));
+    let main =
+        ast::ItemKind::Fn(box ast::FnKind(def, sig, ast::Generics::default(), Some(main_body)));
 
     // Honor the reexport_test_harness_main attribute
     let main_id = match cx.reexport_test_harness_main {