implement null aware ops, fixes #249

lib/src/checker/checker.dart

Index: lib/src/checker/checker.dart
diff --git a/lib/src/checker/checker.dart b/lib/src/checker/checker.dart
index 1cabddd764ee02584ce2fa7c6aa0e6d121dead82..a93b3cede1f8bfe3271286acb6fbca47ea9b9bf2 100644
--- a/lib/src/checker/checker.dart
+++ b/lib/src/checker/checker.dart
@@ -375,7 +375,10 @@ class CodeChecker extends RecursiveAstVisitor {
   @override
   void visitConstructorFieldInitializer(ConstructorFieldInitializer node) {
     var field = node.fieldName;
-    DartType staticType = rules.elementType(field.staticElement);

[vsm, 2015/08/25 21:47:26]

FWIW, I recently changed rules.elementType to return dynamicType if the arg is
null.  (It was breaking some tests under sdk - forget which one.)

[Jennifer Messerly, 2015/08/25 22:13:11]

Nice! reverted this

+    var element = field.staticElement;
+    DartType staticType = element != null
+        ? rules.elementType(element)
+        : rules.provider.dynamicType;
     checkAssignment(node.expression, staticType);
     node.visitChildren(this);
   }
@@ -776,6 +779,8 @@ class CodeChecker extends RecursiveAstVisitor {
           break;
         case TokenType.BANG_EQ:
           break;
+        case TokenType.QUESTION_QUESTION:
+          break;
         default:
           assert(false);
       }