Using multiple Scala TypeClass instances in function parameters -

i created group of case classes want implement different behaviors using scala typeclass. code sample below works expected.

case class querybuilder(s: string)  abstract class a() case class b() extends case class c() extends  abstract class s() case class x() extends s case class y() extends s  trait buildablequery[t] {   def toquery(p: t): querybuilder } implicit object bquerybuilder extends buildablequery[b] {   def toquery(p: b): querybuilder = { querybuilder("query of b") } } implicit object cquerybuilder extends buildablequery[c] {   def toquery(p: c): querybuilder = { querybuilder("query of c") } } implicit object xquerybuilder extends buildablequery[x] {   def toquery(p: x): querybuilder = { querybuilder("query of x") } } implicit object yquerybuilder extends buildablequery[y] {   def toquery(p: y): querybuilder = { querybuilder("query of y") } }  def toquery[a: buildablequery](value: a): querybuilder =   (implicitly[buildablequery[a]]).toquery(value)  println(toquery(b()).s) // query of b println(toquery(c()).s) // query of c println(toquery(x()).s) // query of x println(toquery(y()).s) // query of y 

so far good. can use method toquery of defined types.

my problem: want create function returns buildablequery combining abstract classes a , s.

i tried creating new implicit object defines behavior new case class consisting of combination of a , s. when using in function, not compile.

case class as[i <: a, p <: s](a: i, s: p) implicit object asquerybuilder extends buildablequery[as[b, x]] {   def toquery(p: as[b, x]): querybuilder = { querybuilder("query of bx") } }  // not compile... // error: not find implicit value evidence parameter of type buildablequery[as[a,s]] def func(a: a, s: s): querybuilder = toquery(as(a,s))  // not compile... // error: not find implicit value evidence parameter of type buildablequery[as[i,p]] def func2[i <: a: buildablequery, p <: s: buildablequery](a: i, s: p): querybuilder =    toquery(as(a,s)) 

does solution exist problem?

update

if want define as[i, p] instances particular values of i , p, that's possible—you can define asquerybuilder in question, , require instance in methods use type class:

def func(a: a, s: s)(implicit bq: buildablequery[as[a, s]]): querybuilder = toquery(as(a,s))  def func2[i <: a: buildablequery, p <: s: buildablequery](a: i, s: p)(implicit   bq: buildablequery[as[i, p]] ): querybuilder = toquery(as(a, s)) 

now these compile if appropriate instances available.

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original answer

it sounds want create instances generically, not as[b, x]. can generic method:

implicit def asquerybuilder[i <: a, p <: s]: buildablequery[as[i, p]] =   new buildablequery[as[i, p]] {      def toquery(p: as[i, p]): querybuilder = { querybuilder("query of as") } } 

now examples compile.

as side note, using same name (toquery) both type class method , type class syntax method can make things little difficult. may want rename 1 e.g. syntax method available in definition of type class instance's toquery.