Special case -0.0 when constant folding.

dart/frog/leg/lib/js_helper.dart

Index: dart/frog/leg/lib/js_helper.dart
diff --git a/dart/frog/leg/lib/js_helper.dart b/dart/frog/leg/lib/js_helper.dart
index 6c534e90f663c6203e24d558ce69cb792792849d..1817c5ad354d622daacaa43be50a6bf39e0bec11 100644
--- a/dart/frog/leg/lib/js_helper.dart
+++ b/dart/frog/leg/lib/js_helper.dart
@@ -1141,7 +1141,13 @@ class MathNatives {
     checkNull(str);
     if (str is !String) throw new IllegalArgumentException();
     var ret = JS('num', @'parseFloat($0)', str);
-    if (ret.isNaN() && str != 'NaN') throw new BadNumberFormatException(str);
+    if (ret == 0 && (str.startsWith("0x") || str.startsWith("0X"))) {
+      // TODO(ahe): This is unspecified, but tested by co19.

[floitsch, 2012/02/29 15:33:46]

please file a bug that this should not be allowed.

[ahe, 2012/02/29 18:42:55]

I have filed a co19 bug.

+      ret = JS('num', @'parseInt($0)', str);
+    }
+    if (ret.isNaN() && str != 'NaN' && str != '-NaN') {
+      throw new BadNumberFormatException(str);
+    }
     return ret;
   }