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

Author: eddyb

src/librustc_typeck/collect.rs

@@ -540,6 +540,7 @@ pub fn convert(ccx: &CrateCtxt, it: &ast::Item) {
     debug!("convert: item {} with id {}", token::get_ident(it.ident), it.id);
     match it.node {
         // These don't define types.
+        ast::ItemExternCrate(_) | ast::ItemUse(_) |
         ast::ItemForeignMod(_) | ast::ItemMod(_) | ast::ItemMac(_) => {}
         ast::ItemEnum(ref enum_definition, ref generics) => {
             let scheme = ty_of_item(ccx, it);
@@ -979,6 +980,7 @@ pub fn ty_of_item<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>, it: &ast::Item)
             tcx.tcache.borrow_mut().insert(local_def(it.id), scheme.clone());
             return scheme;
         }
+        ast::ItemExternCrate(_) | ast::ItemUse(_) |
         ast::ItemImpl(..) | ast::ItemMod(_) |
         ast::ItemForeignMod(_) | ast::ItemMac(_) => panic!(),
     }

src/librustc_typeck/variance.rs

@@ -379,6 +379,8 @@ impl<'a, 'tcx, 'v> Visitor<'v> for TermsContext<'a, 'tcx> {
                 visit::walk_item(self, item);
             }
 
+            ast::ItemExternCrate(_) |
+            ast::ItemUse(_) |
             ast::ItemImpl(..) |
             ast::ItemStatic(..) |
             ast::ItemConst(..) |
@@ -531,6 +533,8 @@ impl<'a, 'tcx, 'v> Visitor<'v> for ConstraintContext<'a, 'tcx> {
                 }
             }
 
+            ast::ItemExternCrate(_) |
+            ast::ItemUse(_) |
             ast::ItemStatic(..) |
             ast::ItemConst(..) |
             ast::ItemFn(..) |