Volatile type problem

Hi all,
I'm struggling with a volatile type problem which I don't quite understand. I read about it on the SLS but still cannot decipher it. Here is a sample code which exhibits my problem
object TypeTest {
  trait A {    type N <: NLike    type M <: N with MLike        trait NLike    trait MLike extends NLike   }    trait B extends A {    type N <: MyBNLike        trait MyBNLike extends NLike  }    trait C extends A {    type N <: MyCNLike     type M <: N with MyCMLike        trait MyCNLike extends NLike    trait MyCMLike extends MyCNLike with MLike {      def implementMe: String //if you take this away, everything compiles     }  }    trait D extends A with B with C { // If I dont mix C it works.     type N = NLike with MyBNLike with MyCNLike  }}
the compiler error is
overriding type M in trait A with bounds >: Nothing <: C.this.N with C.this.MLike; type M is a volatile type; cannot override a type with non-volatile upper bound     type M <: N with MyCMLike
According to what I understood (which probably is wrong anyway) from the SLS, N in trait A should be declared with a volatile upperbound type, so that others can override it with more volatile types, but I can't figure out how to make it volatile.
Which is the right path to achieve something like the above?
Thanks, cheers.

Sorry I messed up above, its C which doesn't compile with the above error. You can ignore D.


On Wed, Dec 21, 2011 at 4:54 PM, Rodrigo Cano <ioniviil@gmail.com> wrote:

Hi all,
I'm struggling with a volatile type problem which I don't quite understand. I read about it on the SLS but still cannot decipher it. Here is a sample code which exhibits my problem
object TypeTest {
  trait A {    type N <: NLike    type M <: N with MLike        trait NLike    trait MLike extends NLike   }    trait B extends A {    type N <: MyBNLike        trait MyBNLike extends NLike  }    trait C extends A {    type N <: MyCNLike     type M <: N with MyCMLike        trait MyCNLike extends NLike    trait MyCMLike extends MyCNLike with MLike {      def implementMe: String //if you take this away, everything compiles     }  }    trait D extends A with B with C { // If I dont mix C it works.     type N = NLike with MyBNLike with MyCNLike  }}
the compiler error is
overriding type M in trait A with bounds >: Nothing <: C.this.N with C.this.MLike; type M is a volatile type; cannot override a type with non-volatile upper bound     type M <: N with MyCMLike
According to what I understood (which probably is wrong anyway) from the SLS, N in trait A should be declared with a volatile upperbound type, so that others can override it with more volatile types, but I can't figure out how to make it volatile.
Which is the right path to achieve something like the above?
Thanks, cheers.