shorter alternative of constructor with parameter

[Suliman via Digitalmars-d]

> I mean to use syntactic sugar sparingly, not for minor features 
> like this. The trouble is that it makes code non-verbose, which 
> would make D code more difficult to read for those unfamiliar 
> with the language.

Less code make code more easy to read. I do not think that such 
reduce amount of code make code-understanding harder.

I am sure that in Dart 80% (or even more) programmers will use 
reduced constructor.