Add a few more known non-null cases

test/codegen/notnull.dart

 // Copyright (c) 2015, 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 notnull;
 
 void intAssignments() {
   var i = 0;
   i &= 1;
   i |= 1;
@@ skipping 76 matching lines @@
 
   int j = 1;
   j = i == 1 ? 1 : null;
   print(j + 1);
 }
 
 void optParams([int x, int y = 1]) {
   print(x + y);
 }
 
-void namedParams({int x, int y : 1}) {
+void namedParams({int x, int y: 1}) {
   print(x + y);
 }
 
 void forLoops(int length()) {
   for (int i = 0; i < 10; i++) {
     print(i + 1);
   }
   for (int i = 0; i < length(); i++) {
     print(i + 1);
   }
@@ skipping 88 matching lines @@
   } catch (e) {
     print(e + 1);
   }
   try {
     (null as dynamic).foo();
   } catch (e, trace) {
     print('${(e is String) ? e : e.toString()} at $trace');
   }
 }
 
+cascadesOnNull() {
+  dynamic x = null;
+  print((x
+    ..toString()
+    ..runtimeType)
+      .hashCode);
+
+  Object y = null;
+  print((y
+    ..toString()
+    ..runtimeType)
+      .hashCode);
+}
+
 main() {
   intAssignments();
   doubleAssignments();
   boolAssignments();
   nullableLocals(1);
   optParams(1, 2);
   namedParams(x: 1, y: 2);
   forLoops(() => 10);
   increments();
   conditionals(true);
   calls();
   localEscapes();
   controlFlow();
+  cascadesOnNull();
 
   nullableCycle();
   nonNullableCycle();
 }