D语言类变量的别名

import std.stdio; 

class Shape { 
   int area; 
}

class Square : Shape { 
   string name() const @property { 
      return "Square"; 
   } 
   alias Shape.area squareArea; 
}

void main() { 
   auto square = new Square;  
   square.squareArea = 42;  
   writeln(square.name); 
   writeln(square.squareArea); 
}