Correctly collect defaults from type alises in astconv

src/test/compile-fail/default_ty_param_type_alias.rs

@@ -1,17 +0,0 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-use std::collections::HashMap;
-
-type IntMap<K=usize> = HashMap<K, usize>;
-
-fn main() {
-    let x = IntMap::new();
-}