Make int and double nullable by default

lib/src/codegen/js_codegen.dart

Index: lib/src/codegen/js_codegen.dart
diff --git a/lib/src/codegen/js_codegen.dart b/lib/src/codegen/js_codegen.dart
index ab8d555d827b05ef5f41e18a4824d46e2e50037d..b952719eaf83fd958ce922f14cda57e66bdbf3f6 100644
--- a/lib/src/codegen/js_codegen.dart
+++ b/lib/src/codegen/js_codegen.dart
@@ -1047,9 +1047,30 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
 
   bool unaryOperationIsPrimitive(DartType t) => typeIsPrimitiveInJS(t);
 
+  bool _isNonNullableExpression(Expression expr) {

[Jennifer Messerly, 2015/03/03 19:14:30]

add a TODO that this will go away when we have not-nullable types in the type
system?

it's nice, but a shame we'll lose info if you assign an expr to a variable.

[vsm, 2015/03/03 19:29:41]

Done.

+    if (expr is Literal && expr is! NullLiteral) {
+      return true;
+    }
+    if (expr is ParenthesizedExpression) {
+      return _isNonNullableExpression(expr.expression);
+    }
+    DartType type = null;
+    if (expr is BinaryExpression) {
+      type = rules.getStaticType(expr.leftOperand);
+    } else if (expr is PrefixExpression) {
+      type = rules.getStaticType(expr.operand);
+    } else if (expr is PostfixExpression) {
+      type = rules.getStaticType(expr.operand);
+    }
+    if (type != null && typeIsPrimitiveInJS(type)) {
+      return true;
+    }
+    return false;
+  }
+
   JS.Expression notNull(Expression expr) {
     var type = rules.getStaticType(expr);
-    if (rules.isNonNullableType(type)) {
+    if (rules.isNonNullableType(type) || _isNonNullableExpression(expr)) {
       return _visit(expr);
     } else {
       return js.call('dart.notNull(#)', _visit(expr));