This is a good practice, even better would be checking the type or class.
> "String +(Object other) Converts other to a string and creates a new string by concatenating this string with the converted other. "
This is a bad idea, now I have a gripe with dart.
http://qconlondon.com/london-2009/presentation/Null+Referenc...
Like I said, I'm not particularly a fan of Dart.
ie. data Maybe a = Nothing | Just a data Either a b = Left a | Right b instead of (err,result) like in go
I don't think this is right, and seems to be bad wording on part of the documentation. I don't have any access to an interpreter right now, besides the Google AppSpot in-browser console, but adding a String Object and a Date Object to a new variable does not alter either object or do a forced alter on the existing objects, but rather creates a new string object.
Though, I can't tell if either the date object, or the first string object in this example are altered, it appears that they aren't changed during concatenation: http://try-dart-lang.appspot.com/s/KSAX
The gripe comes from overloading the + operator, for all I can tell. That's at least the point of the author of the blog post, having + for addition and concatination, with poor type support.
The blog claims that "1" + 1 = "11" (exactly what the docs state here) and claims the same for 1 + "1".