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Is it possible to read parameterized/polymorphic case classes ?

See original GitHub issue

I’m sorry for flooding upicke with issues 😃 But I got utterly stuck on reading :

case class What[E](a: TypeThatHasAReaderAvailable[E])


The problem is here :

[info] exception during macro expansion: 
[info] scala.ScalaReflectionException: value apply encapsulates multiple overloaded alternatives and cannot be treated as a method. Consider invoking `<offending symbol>.asTerm.alternatives` and manually picking the required method
[info]  at scala.reflect.api.Symbols$SymbolApi$class.asMethod(Symbols.scala:228)
[info]  at scala.reflect.internal.Symbols$SymbolContextApiImpl.asMethod(Symbols.scala:82)
[info]  at upickle.Macros$.picklerFor(Macros.scala:121)
[info]  at upickle.Macros$.macroRImpl(Macros.scala:32)
[info]       val res = read[ResponseMessage[Vertex]](

I tried even invoke the macro supplying the type parameters directly to it, but it failed the same way :

    import scala.language.experimental.macros
    def macroR[T]: Reader[T] = macro Macros.macroRImpl[T]
    val a = macroR[What[Ever]]

Would you please give me a hint here?

Issue Analytics

  • State:closed
  • Created 9 years ago
  • Comments:7 (6 by maintainers)

github_iconTop GitHub Comments

ForNeVeRcommented, Aug 8, 2015

@lihaoyi I think that should be mentioned in the documentation.

l15k4commented, Sep 5, 2014

@lihaoyi you were right, I must have made a mistake somewhere else.

def poly[T: Reader](whatever: String): T = read[T](whatever)

is really valid.

Read more comments on GitHub >

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