class type error while working with generic method in scala -

below code snippet...a bit testing mode code snippet.i trying create method through can change return type.

while calling method getting exception "class type expected object found"

trait  trait b extends {   def aba[t](a:int):t }  class d  class c extends b {   def aba[d](a:int) = {     println("asasas")     new d   } } 

the actual error in scala 2.11 is

:13: error: class type required d found

which means can't instantiate generic type d - d class shadowed [d] definition

you can't override t (as part of aba's method signature) due liskov substitution principle change behaviour (and signature) subclass. can define t type member:

trait  trait b extends {   type t   def aba(a:int):t }  class d   class c extends b {   type t = d   def aba(a:int): t = {     println("asasas")     new d   } }