It was recently added, but apparently removed again. (I don't know the exact reasons). Edit. you can see the announcement here: https://plus.google.com/1098663

It was recently added, but apparently removed again. (I don't know the exact reasons). Edit. you can see the announcement here: https://plus.google.com/109866369054280216564/posts/XbjvN5QVpn9 https://plus.google.com/109866369054280216564/posts/XbjvN5QV... Edit2. Removal of the feature: https://code.google.com/p/dart/issues/detail?id=16425 https://code.google.com/p/dart/issues/detail?id=16425