How is a forwarding constructor implemented in a programming language?

In Flutter (Dart), a redirecting constructor allows one constructor to call another to avoid code duplication. This is done using a colon and the name of the other constructor after the parameter list.

Example:

class Point {
  final int x, y;

  Point(this.x, this.y);

  // Redirecting constructor that creates a point on the X axis
  Point.alongXAxis(int x) : this(x, 0);
}

void main() {
  var p = Point.alongXAxis(5);
  print('x: ${p.x}, y: ${p.y}'); // x: 5, y: 0
}