Scala Implicit class and overloading an existing function - scala

Question

Any idea how to get the following to work:
trait HttpTransport {
def doGet(str: String): String
}
trait CoreGet {
def GET(str: String)(implicit imp:String): List[String]
}
trait VerbGet extends CoreGet with HttpTransport {
override def GET(str: String)(implicit imp:String): List[String]= {
println("->VerbGet.GET")
val str1 = doGet(str)
// and more biz logic calls here
List(s"\nverb (biz logic) called url $str and got '${str1}'>")
}
}
// PlayGet {
implicit class ExtendCoreGet(coreGet: CoreGet) {
def GET[A](url: String)(implicit imp:String, imp2: List[A]): List[A]= {
println(s"->ExtendCoreGet.GET($url)")
val coreGetResult = coreGet.GET(url)
coreGetResult.flatMap(_ => imp2)
}
}
trait Play extends HttpTransport {
override def doGet(str: String): String = {
println("->Play.doGet")
s"\nPlay.doGet($str)>"
}
}
val client = new VerbGet with Play
client.GET("www.go.com")("hello", List("1")) //<-- does not compile
Compiler error:
too many arguments (2) for method GET: (implicit imp:
String)List[String]
You can play with the code here:
https://scastie.scala-lang.org/arminio/tN9NfdxGQUmusrNL0lJ78w

Answer 1

It looks like you are trying extend functionality of VerbGet. You need to fix two things:
1. ExtendCoreGet must extend AnyVal to add more methods.
2. You can add new functionality by adding new method say GET2 but you can't overload existing method. Renmaed your GET to GET2 or something meaningful.
ExtendCoreGet definition should be
implicit class ExtendCoreGet(val coreGet: CoreGet) extends AnyVal {
def GET2[A](url: String)(implicit imp:String, imp2: List[A]): List[A]= {
coreGet.GET(url).flatMap(_ => imp2)
}
}