scala - Trait does not conform with type parameter bounds -

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i having issues types. in case have 2 traits base methods, , 1 of them depends on other. after have 2 implementations them. have idea wrong here?

the compiler saying:

type arguments [impldefinition,impldto,impldtoidentifier] not conform trait childoperations's type parameter bounds [c <: types.baset[a,i],a <: types.idobj[i],i <: iidentifier] [error] class imploperations extends parent2(new impldefinition) childoperations[impldefinition, impldto, impldtoidentifier] {

the code:

/*  * generic implementation  */  object types {    type idobj[i <: iidentifier] = anyref {def id: i}    type baset[a, <: iidentifier] = parent1[a] {     def id: foo[i]   }  }  trait iidentifier extends {   def id: long    override def tostring = id.tostring }  class parent1[a](a: string)  class foo[a](a: string)  trait childdefinition[a <: types.idobj[i], <: iidentifier] {   self: parent1[a] =>    def id(a: a): foo[i]  }  class parent2[a](a: a)  trait childoperations[c <: types.baset[a, i], <: types.idobj[i], <: iidentifier] {   self: parent2[c] =>    def get(identifier: i): option[a] }  /*  * concrete implementation  */  case class impldtoidentifier(id: long) extends iidentifier  case class impldto(id: impldtoidentifier, name: string)  class impldefinition extends parent1[impldto]("value") childdefinition[impldto, impldtoidentifier] {   override def id(a: impldto): foo[impldtoidentifier] = ??? }  class imploperations extends parent2(new impldefinition) childoperations[impldefinition, impldto, impldtoidentifier] {   self =>   override def get(identifier: impldtoidentifier): option[impldto] = ??? // here use id method impldefinition }

the problem seems signature of id def in impldefinition. types.baset asks def id: foo[i] impldefinition provides def id(a: impldto): foo[impldtoidentifier] if add def id:foo[impldtoidentifier] = ??? impldefinition class things compile:

class impldefinition extends parent1[impldto]("value") childdefinition[impldto, impldtoidentifier] {   def id:foo[impldtoidentifier] = ???   override def id(a: impldto): foo[impldtoidentifier] = ??? }

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