Simplify and fix instantiation of recursive types.

tests/language/cyclic_type_test.dart

Index: tests/language/cyclic_type_test.dart
===================================================================
--- tests/language/cyclic_type_test.dart	(revision 34737)
+++ tests/language/cyclic_type_test.dart	(working copy)
@@ -10,23 +10,57 @@
   get t => T;
 }
 
-class Derived<T> extends Base<Derived<Derived<T>>> {}
+// Derived<T> is contractive.
+class Derived<T> extends Base<Derived<T>> {}  /// 00: ok
 
-class Derived1<T> extends Base<Derived2<T>> {}
+// Derived<T> is contractive.
+class Derived<T> extends Base<Derived<Derived<int>>> {}  /// 01: ok
 
-class Derived2<T> extends Base<Derived1<Derived2<T>>> {}
+// Derived<T> is non-contractive.
+class Derived<T> extends Base<Derived<Derived<T>>> {}  /// 02: ok
 
+// Derived1<U> and Derived2<V> are contractive.
+class Derived1<U> extends Base<Derived2<U>> {}   /// 03: ok
+class Derived2<V> extends Base<Derived1<V>> {}   /// 03: ok
+
+// Derived1<U> and Derived2<V> are non-contractive.
+class Derived1<U> extends Base<Derived2<U>> {}   /// 04: ok
+class Derived2<V> extends Base<Derived1<Derived2<V>>> {}   /// 04: ok
+
 main() {
-  var d = new Derived();
-  Expect.equals("Derived<Derived>", d.t.toString());
-  d = new Derived<bool>();
-  Expect.equals("Derived<Derived<bool>>", d.t.toString());
-  d = new Derived<Derived>();
-  Expect.equals("Derived<Derived<Derived>>", d.t.toString());
-  d = new Derived1();
-  Expect.equals("Derived2", d.t.toString());
-  d = new Derived2();
-  Expect.equals("Derived1<Derived2>", d.t.toString());
-  d = new Derived2<Derived1<int>>();
-  Expect.equals("Derived1<Derived2<Derived1<int>>>", d.t.toString());
+  var d;
+  d = new Derived();  /// 00: continued
+  Expect.equals("Derived", d.t.toString());  /// 00: continued
+  d = new Derived<bool>();  /// 00: continued
+  Expect.equals("Derived<bool>", d.t.toString());  /// 00: continued
+  d = new Derived<Derived>();  /// 00: continued
+  Expect.equals("Derived<Derived>", d.t.toString());  /// 00: continued
+
+  d = new Derived();  /// 01: continued
+  Expect.equals("Derived<Derived<int>>", d.t.toString());  /// 01: continued
+  d = new Derived<bool>();  /// 01: continued
+  Expect.equals("Derived<Derived<int>>", d.t.toString());  /// 01: continued
+  d = new Derived<Derived>();  /// 01: continued
+  Expect.equals("Derived<Derived<int>>", d.t.toString());  /// 01: continued
+
+  d = new Derived();  /// 02: continued
+  Expect.equals("Derived<Derived>", d.t.toString());  /// 02: continued
+  d = new Derived<bool>();  /// 02: continued
+  Expect.equals("Derived<Derived<bool>>", d.t.toString());  /// 02: continued
+  d = new Derived<Derived>();  /// 02: continued
+  Expect.equals("Derived<Derived<Derived>>", d.t.toString());  /// 02: continued
+
+  d = new Derived1();  /// 03: continued
+  Expect.equals("Derived2", d.t.toString());  /// 03: continued
+  d = new Derived2();  /// 03: continued
+  Expect.equals("Derived1", d.t.toString());  /// 03: continued
+  d = new Derived2<Derived1<int>>();  /// 03: continued
+  Expect.equals("Derived1<Derived1<int>>", d.t.toString());  /// 03: continued
+
+  d = new Derived1();  /// 04: continued
+  Expect.equals("Derived2", d.t.toString());  /// 04: continued
+  d = new Derived2();  /// 04: continued
+  Expect.equals("Derived1<Derived2>", d.t.toString());  /// 04: continued
+  d = new Derived2<Derived1<int>>();  /// 04: continued
+  Expect.equals("Derived1<Derived2<Derived1<int>>>", d.t.toString());  /// 04: continued
 }