Don't use an allocation for ItemId in StmtKind

src/librustc/hir/intravisit.rs

@@ -951,7 +951,7 @@ pub fn walk_stmt<'v, V: Visitor<'v>>(visitor: &mut V, statement: &'v Stmt) {
     visitor.visit_id(statement.id);
     match statement.node {
         StmtKind::Local(ref local) => visitor.visit_local(local),
-        StmtKind::Item(ref item) => visitor.visit_nested_item(**item),
+        StmtKind::Item(item) => visitor.visit_nested_item(item),
         StmtKind::Expr(ref expression) |
         StmtKind::Semi(ref expression) => {
             visitor.visit_expr(expression)

src/librustc/hir/lowering.rs

@@ -4663,7 +4663,7 @@ fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
                         hir::Stmt {
                             id: node_id,
                             hir_id,
-                            node: hir::StmtKind::Item(P(item_id)),
+                            node: hir::StmtKind::Item(item_id),
                             span: s.span,
                         }
                     })
@@ -4693,7 +4693,7 @@ fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
                         hir::Stmt {
                             id: node_id,
                             hir_id,
-                            node: hir::StmtKind::Item(P(item_id)),
+                            node: hir::StmtKind::Item(item_id),
                             span: s.span,
                         }
                     })

src/librustc/hir/mod.rs

@@ -1159,8 +1159,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 pub enum StmtKind {
     /// A local (`let`) binding.
     Local(P<Local>),
+
     /// An item binding.
-    Item(P<ItemId>),
+    Item(ItemId),
 
     /// An expression without a trailing semi-colon (must have unit type).
     Expr(P<Expr>),

src/librustc/hir/print.rs

@@ -1007,8 +1007,8 @@ pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
                 }
                 self.end()?
             }
-            hir::StmtKind::Item(ref item) => {
-                self.ann.nested(self, Nested::Item(**item))?
+            hir::StmtKind::Item(item) => {
+                self.ann.nested(self, Nested::Item(item))?
             }
             hir::StmtKind::Expr(ref expr) => {
                 self.space_if_not_bol()?;