rebasing and reviewer changes

Primarily refactoring `(Ident, Option<NodeId>)` to `Segment`

src/libsyntax/parse/parser.rs

@@ -2137,7 +2137,7 @@ impl<'a> Parser<'a> {
             PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
         } else {
             // Generic arguments are not found.
-            PathSegment::from_ident(ident,)
+            PathSegment::from_ident(ident)
         })
     }