This is a code producing a Segmentation Fault, but correctly compiles:

public interface Bar : Object {
	public abstract string name { get; set; }
	public abstract string get_text ();
}

public class BarC : Object, Bar {
	public string name { get; set; }
	public string get_text () { return "BarC"; }
}


public class BarD : BarC, Bar {
	public new string get_text () { return "BarD"; }
}

public void main () {
	var c = new BarD ();
	c.name = "D Class";
	stdout.printf (c.name+"\n");
	stdout.printf ((c as BarC).name+"\n");
	stdout.printf ((c as Bar).name+"\n");
	
	stdout.printf (c.get_text ()+"\n");
	stdout.printf ((c as BarC).get_text ()+"\n");
	stdout.printf ((c as Bar).get_text ()+"\n");
}

Code at Comment #1, produce at runtime a infinite call to property name.

By removing interface declaration at class BarD to have:

public class BarD : BarC {
	public new string get_text () { return "BarD"; }
}

The program compiles an run with following results:

D Class
D Class
D Class

BarD
BarC
BarC


But now you can see method Bar.get_text() is not overrided by BarD, so when using Bar interface to access a BarD object you will be using BarC implementation.

So no way to override Bar.get_text() from BarD. By using following syntax:

public new string Bar.get_text () { return "BarD"; }

Should be possible to override BarC.get_text() implementation with the one provided by BarD.

*** This bug has been marked as a duplicate of bug 648897 ***