t278.scala:5: error: overloaded method value a with alternatives:
  => C.this.A => Unit <and>
  => () => Unit
 does not take type parameters
  println(a[A])
          ^
t278.scala:4: error: method a is defined twice
  conflicting symbols both originated in file 't278.scala'
  def a = (p:A) => ()
      ^
two errors found