Avro4s: The argument types of an anonymous function must be fully known. (SLS 8.5)

Question

I am trying to map the fields of a case class using the avro4s FieldMapper.

implicit val short: FieldMapper = {
  case "fieldName1" => "fieldName2"
}

But I'm receiving the following error:

Error:(20, 39) missing parameter type for expanded function
The argument types of an anonymous function must be fully known. (SLS 8.5)
Expected type was: com.sksamuel.avro4s.FieldMapper
    implicit val short: FieldMapper = {

I found similar questions related to this error:

• Scala: Type missing parameter type for expanded function The argument types of an anonymous function must be fully known. (SLS 8.5)
• Scala missing parameter type for expanded function The argument types of an anonymous function must be fully known. (SLS 8.5)
• The argument types of an anonymous function must be fully known. (SLS 8.5)

However I could not derive a solution for my particular problem.

Any help is appreciated!