Answer by micimize for Dart: spread operator for constructor

Now that dart has both the spread operator and class extensions, you could abuse both to add ...spread support to static methods. While I doubt this is a good idea, I made a working dartpad (gist) to demonstrate. The end result looks something like:

final Border spreadBorder = Border.fromSides([  ...Border(    left: BorderSide(color: Colors.pink),    right: BorderSide(color: Colors.pinkAccent),  ).sides,  ...Border(    top: BorderSide(color: Colors.blue),    bottom: BorderSide(color: Colors.blueAccent),  ).sides,]).scale(5);enum _Side { top, right, bottom, left }extension SpreadBorder on Border {  Iterable<MapEntry<_Side, BorderSide>> get sides {    return () sync* {      if (top != BorderSide.none) {        yield MapEntry(_Side.top, top);      }      // ...other yields    }();  }  static Border fromSides(Iterable<MapEntry<_Side, BorderSide>> parts) {    BorderSide top, right, bottom, left;    for (final borderPart in parts) {      switch (borderPart.key) {        case _Side.top:          top = borderPart.value;          break;        // ... other cases      }    }    return Border(      top: top,      right: right,      bottom: bottom,      left: left,    );  }}