rustc_back: fix fallout of merging ast::ViewItem into ast::Item.

Author: eddyb

src/librustc_back/svh.rs

@@ -188,7 +188,6 @@ mod svh_visitor {
         SawLifetimeDef(token::InternedString),
 
         SawMod,
-        SawViewItem,
         SawForeignItem,
         SawItem,
         SawDecl,
@@ -434,19 +433,6 @@ mod svh_visitor {
             SawStmt(saw_stmt(&s.node)).hash(self.st); visit::walk_stmt(self, s)
         }
 
-        fn visit_view_item(&mut self, i: &ViewItem) {
-            // Two kinds of view items can affect the ABI for a crate:
-            // exported `pub use` view items (since that may expose
-            // items that downstream crates can call), and `use
-            // foo::Trait`, since changing that may affect method
-            // resolution.
-            //
-            // The simplest approach to handling both of the above is
-            // just to adopt the same simple-minded (fine-grained)
-            // hash that I am deploying elsewhere here.
-            SawViewItem.hash(self.st); visit::walk_view_item(self, i)
-        }
-
         fn visit_foreign_item(&mut self, i: &ForeignItem) {
             // FIXME (#14132) ideally we would incorporate privacy (or
             // perhaps reachability) somewhere here, so foreign items