Question

鉴于shapeless type class derivation example (with Show)。

如果有案例对象，如何使其适应工作：

case object Snafu extends Super

目前在宏扩展期间无法编译异常：

scala.ScalaReflectionException: <none> is not a term
    at scala.reflect.api.Symbols$SymbolApi$class.asTerm(Symbols.scala:199)
    at scala.reflect.internal.Symbols$SymbolContextApiImpl.asTerm(Symbols.scala:79)
    at shapeless.GenericMacros$Helper$class.mkTransCase(generic.scala:394)
    at shapeless.GenericMacros$$anon$2.mkTransCase(generic.scala:122)
    at shapeless.GenericMacros$Helper$class.mkToReprCase(generic.scala:411)
    at shapeless.GenericMacros$$anon$2.mkToReprCase(generic.scala:122)
    at shapeless.GenericMacros$Helper$$anonfun$19.apply(generic.scala:573)
    at shapeless.GenericMacros$Helper$$anonfun$19.apply(generic.scala:573)
    at scala.Function2$$anonfun$tupled$1.apply(Function2.scala:54)
    at scala.Function2$$anonfun$tupled$1.apply(Function2.scala:53)
    at scala.collection.immutable.List.map(List.scala:272)
    at shapeless.GenericMacros$Helper$class.mkCases(generic.scala:338)
    at shapeless.GenericMacros$$anon$2.mkCases(generic.scala:122)
    at shapeless.GenericMacros$Helper$class.deriveInstance(generic.scala:573)
    at shapeless.GenericMacros$$anon$2.deriveInstance(generic.scala:122)
    at shapeless.GenericMacros$.deriveInstanceAux(generic.scala:131)
    at shapeless.GenericMacros$.deriveLabelledInstance(generic.scala:117)
    implicit val showInstance = Show[Super]
                                    ^

Answer 1

刚从Twitter上的Miles那里得到答案： https://twitter.com/milessabin/status/541954842076659712

很快就会解决。

LabelledTypeClass不适用于带有case对象的ADT

1 个答案: