Implement new scope rules for type variables (issue 5230).

tests/language/type_parameter_test.dart

 // Copyright (c) 2012, 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.
 
 class A<T> {
   Function closure;
   A._(this.closure);
 
   factory A() {
     return new A._(() => new Set<T>());
   }
 
   A.bar() {
     closure = () => new Set<T>();
   }
 
   static
   T /// 01: static type warning, dynamic type error
   staticMethod(
   T /// 02: static type warning, dynamic type error
   a) {
     final
     T /// 03: static type warning, dynamic type error
-    a = null;
+    a = "not_null";
     print(a);
+    return a;
   }
 
   static final
   T /// 04: static type warning, dynamic type error
-  staticField = null;
+  staticField = "not_null";
+
+  // Assigning null to a malformed type is not a dynamic error.
+  static
+  T staticMethod2(T a) {
+    final T a = null;
+    print(a);
+    return a;
+  }
+
+  static final T staticField2 = null;
 }
 
 main() {
   var s = ((new A()).closure)();
   Expect.isTrue(s is Set);
 
   s = ((new A.bar()).closure)();
   Expect.isTrue(s is Set);
 
   s = ((new A<int>()).closure)();
   Expect.isTrue(s is Set<int>);
   Expect.isFalse(s is Set<double>);
 
   s = ((new A<int>.bar()).closure)();
   Expect.isTrue(s is Set<int>);
   Expect.isFalse(s is Set<double>);
 
-  A.staticMethod(null);
+  A.staticMethod("not_null");
   print(A.staticField);
+
+  A.staticMethod2(null);
+  print(A.staticField2);
 }