Use List instead of Link in the type system.

tests/compiler/dart2js/subtype_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library subtype_test;
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'type_test_helper.dart';
 import 'package:compiler/implementation/dart_types.dart';
@@ skipping 539 matching lines @@
       class H<T extends S, S extends T> {}
       class I<T extends S, S extends U, U extends T> {}
       class J<T extends S, S extends U, U extends S> {}
       """).then((env) {
     void expect(bool expectSubtype, DartType T, DartType S,
                 {bool expectMoreSpecific}) {
       testTypes(env, T, S, expectSubtype, expectMoreSpecific);
     }
 
     ClassElement A = env.getElement('A');
-    TypeVariableType A_T = A.thisType.typeArguments.head;
+    TypeVariableType A_T = A.thisType.typeArguments[0];
     ClassElement B = env.getElement('B');
-    TypeVariableType B_T = B.thisType.typeArguments.head;
+    TypeVariableType B_T = B.thisType.typeArguments[0];
     ClassElement C = env.getElement('C');
-    TypeVariableType C_T = C.thisType.typeArguments.head;
+    TypeVariableType C_T = C.thisType.typeArguments[0];
     ClassElement D = env.getElement('D');
-    TypeVariableType D_T = D.thisType.typeArguments.head;
+    TypeVariableType D_T = D.thisType.typeArguments[0];
     ClassElement E = env.getElement('E');
-    TypeVariableType E_T = E.thisType.typeArguments.head;
-    TypeVariableType E_S = E.thisType.typeArguments.tail.head;
+    TypeVariableType E_T = E.thisType.typeArguments[0];
+    TypeVariableType E_S = E.thisType.typeArguments[1];
     ClassElement F = env.getElement('F');
-    TypeVariableType F_T = F.thisType.typeArguments.head;
-    TypeVariableType F_S = F.thisType.typeArguments.tail.head;
+    TypeVariableType F_T = F.thisType.typeArguments[0];
+    TypeVariableType F_S = F.thisType.typeArguments[1];
     ClassElement G = env.getElement('G');
-    TypeVariableType G_T = G.thisType.typeArguments.head;
+    TypeVariableType G_T = G.thisType.typeArguments[0];
     ClassElement H = env.getElement('H');
-    TypeVariableType H_T = H.thisType.typeArguments.head;
-    TypeVariableType H_S = H.thisType.typeArguments.tail.head;
+    TypeVariableType H_T = H.thisType.typeArguments[0];
+    TypeVariableType H_S = H.thisType.typeArguments[1];
     ClassElement I = env.getElement('I');
-    TypeVariableType I_T = I.thisType.typeArguments.head;
-    TypeVariableType I_S = I.thisType.typeArguments.tail.head;
-    TypeVariableType I_U = I.thisType.typeArguments.tail.tail.head;
+    TypeVariableType I_T = I.thisType.typeArguments[0];
+    TypeVariableType I_S = I.thisType.typeArguments[1];
+    TypeVariableType I_U = I.thisType.typeArguments[2];
     ClassElement J = env.getElement('J');
-    TypeVariableType J_T = J.thisType.typeArguments.head;
-    TypeVariableType J_S = J.thisType.typeArguments.tail.head;
-    TypeVariableType J_U = J.thisType.typeArguments.tail.tail.head;
+    TypeVariableType J_T = J.thisType.typeArguments[0];
+    TypeVariableType J_S = J.thisType.typeArguments[1];
+    TypeVariableType J_U = J.thisType.typeArguments[2];
 
     DartType Object_ = env['Object'];
     DartType num_ = env['num'];
     DartType int_ = env['int'];
     DartType String_ = env['String'];
     DartType dynamic_ = env['dynamic'];
 
     // class A<T> {}
     expect(true, A_T, Object_);
     expect(false, A_T, num_);
@@ skipping 152 matching lines @@
     expect(false, J_U, num_);
     expect(false, J_U, int_);
     expect(false, J_U, String_);
     expect(true, J_U, dynamic_);
     expect(false, J_U, J_T);
     expect(true, J_U, J_S);
     expect(true, J_U, J_U);
     expect(false, J_U, A_T);
   }));
 }