Scala 中隐式值方法的类型参数 - Circe

Question

Scala 中隐式值方法的类型参数 - Circe

Eli*_*doo 2 generics scala implicit circe

我是 Scala 新手，正在使用它circe来建模和序列化一些 API 响应。我发现自己使用以下样板

sealed trait SomeTrait

object SomeTrait {
    implicit val someEncoder: Encoder[SomeTrait] = deriveEncoder[SomeTrait]
    implicit val someDecoder: Decoder[SomeTrait] = deriveDecoder[SomeTrait]

    <code>
}

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相反，我想使用泛型，并定义类似的东西

trait SerializableTrait[A] {
    implicit val someEncoder: Encoder[A] = deriveEncoder[A]
    implicit val someDecoder: Decoder[A] = deriveDecoder[A]
}

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然后多次使用扩展：

sealed trait SomeTrait

object SomeTrait extends SerializableTrait[SomeTrain] {

    <code>
}

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但我得到的could not find Lazy implicit value of type io.circe.generic.encoding.DerivedAsObjectEncoder解码器也是类似的。

我知道我可能正在尝试实现circle.auto功能，但我想了解这种用法有什么问题。理想情况下，我希望编译器dervieEncoder/Decoder仅在实际需要时在非类型参数化特征内评估。

Answer 1

Dmy*_*tin 5

您的问题类似于Scala 中值类的隐式 Json Formatter。就在那里 json 库是 play-json 并且您正在使用 Circe。

deriveEncoder和deriveDecoder是宏（实际上不是宏本身，但它们称为宏）。所以你不能在你想要的地方打电话给他们。deriveEncoder[A]并deriveDecoder[A]试图扩展其中A不是案例类或密封特征（具有案例类子级）而是抽象类型（类型参数）。

将一些公共代码提取到特征并扩展该特征是避免代码重复的 OOP 方法，但宏是一种不同的范例，即元编程。对于元编程，您不能总是遵循 OOP 原则。

如果您想推迟宏的扩展，您可以将隐式宏设为隐式宏。这很重要，因为在您的代码中deriveEncoder[A]，和deriveDecoder[A]现在被调用（扩展）为抽象A，但对于隐式宏，它们将在稍后请求隐式时被调用（扩展），即当A被推断为具体的密封特征或案例类时。

// in a different subproject

import io.circe.{Decoder, Encoder}
import scala.language.experimental.macros
import scala.reflect.macros.whitebox // libraryDependencies += scalaOrganization.value % "scala-reflect" % scalaVersion.value

trait SerializableTrait[A] {
  implicit def someEncoder: Encoder[A] = macro SerializableTraitMacros.someEncoderImpl[A]
  implicit def someDecoder: Decoder[A] = macro SerializableTraitMacros.someDecoderImpl[A]
}

class SerializableTraitMacros(val c: whitebox.Context) {
  import c.universe._

  val semiauto = q"_root_.io.circe.generic.semiauto"

  def someEncoderImpl[A: WeakTypeTag]: Tree = q"$semiauto.deriveEncoder[${weakTypeOf[A]}]"
  def someDecoderImpl[A: WeakTypeTag]: Tree = q"$semiauto.deriveDecoder[${weakTypeOf[A]}]"
}

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现在，您不需要在案例类或密封特征的伴随对象中定义隐式。你只需要让伴生对象SerializableTrait按照你想要的方式延伸

import io.circe.{Decoder, Encoder}

sealed trait SomeTrait

object SomeTrait extends SerializableTrait[SomeTrait]

case class A(i: Int, s: String) extends SomeTrait // the sealed trait must have at least one case-class child

implicitly[Encoder[SomeTrait]] // compiles
implicitly[Decoder[SomeTrait]] // compiles

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使用scalacOptions += "-Ymacro-debug-lite"（也许也"-Xlog-implicits"有用）你可以看到 Circe 实际上为该特征生成了哪些编解码器实例

//scalac: {
//  val inst$macro$14: io.circe.generic.encoding.DerivedAsObjectEncoder[App.SomeTrait] = {
//    final class anon$someEncoder$macro$13 extends _root_.scala.Serializable {
//      def <init>() = {
//        super.<init>();
//        ()
//      };
//      lazy val inst$macro$1: io.circe.generic.encoding.DerivedAsObjectEncoder[App.SomeTrait] = encoding.this.DerivedAsObjectEncoder.deriveEncoder[App.SomeTrait, shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](shapeless.this.LabelledGeneric.materializeCoproduct[App.SomeTrait, (Symbol @@ String("A")) :: shapeless.HNil, App.A :+: shapeless.CNil, shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](DefaultSymbolicLabelling.instance[App.SomeTrait, (Symbol @@ String("A")) :: shapeless.HNil](::.apply[Symbol @@ String("A"), shapeless.HNil.type](scala.Symbol.apply("A").asInstanceOf[Symbol @@ String("A")], HNil)), Generic.instance[App.SomeTrait, App.A :+: shapeless.CNil](((p: App.SomeTrait) => Coproduct.unsafeMkCoproduct((p: p: @_root_.scala.unchecked) match {
//  case (_: App.A) => 0
//}, p).asInstanceOf[App.A :+: shapeless.CNil]), ((x$1: App.A :+: shapeless.CNil) => Coproduct.unsafeGet(x$1).asInstanceOf[App.SomeTrait])), coproduct.this.ZipWithKeys.cpZipWithKeys[Symbol @@ String("A"), App.A, shapeless.HNil, shapeless.CNil](coproduct.this.ZipWithKeys.cnilZipWithKeys, Witness.mkWitness[Symbol with shapeless.tag.Tagged[String("A")]](scala.Symbol.apply("A").asInstanceOf[Symbol @@ String("A")].asInstanceOf[Symbol with shapeless.tag.Tagged[String("A")]])), scala.this.<:<.refl[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]), shapeless.Lazy.apply[io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]](inst$macro$2)).asInstanceOf[io.circe.generic.encoding.DerivedAsObjectEncoder[App.SomeTrait]];
//      lazy val inst$macro$2: io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out] = ({
//  final class $anon extends io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out] {
//    def <init>() = {
//      super.<init>();
//      ()
//    };
//    private[this] val circeGenericEncoderForA = shapeless.Lazy.apply[io.circe.generic.encoding.DerivedAsObjectEncoder[App.A]](inst$macro$3).value;
//    final def encodeObject(a: shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out): io.circe.JsonObject = shapeless.Inr.apply[Nothing, shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](a) match {
//      case shapeless.Inr((circeGenericInrBindingForA @ _)) => circeGenericInrBindingForA match {
//        case shapeless.Inl((circeGenericInlBindingForA @ _)) => io.circe.JsonObject.singleton("A", $anon.this.circeGenericEncoderForA.apply(circeGenericInlBindingForA))
//        case shapeless.Inr(_) => scala.sys.`package`.error("Cannot encode CNil")
//      }
//    }
//  };
//  new $anon()
//}: io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]).asInstanceOf[io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]];
//      lazy val inst$macro$3: io.circe.generic.encoding.DerivedAsObjectEncoder[App.A] = encoding.this.DerivedAsObjectEncoder.deriveEncoder[App.A, shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](shapeless.this.LabelledGeneric.materializeProduct[App.A, (Symbol @@ String("i")) :: (Symbol @@ String("s")) :: shapeless.HNil, Int :: String :: shapeless.HNil, shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](DefaultSymbolicLabelling.instance[App.A, (Symbol @@ String("i")) :: (Symbol @@ String("s")) :: shapeless.HNil](::.apply[Symbol @@ String("i"), (Symbol @@ String("s")) :: shapeless.HNil.type](scala.Symbol.apply("i").asInstanceOf[Symbol @@ String("i")], ::.apply[Symbol @@ String("s"), shapeless.HNil.type](scala.Symbol.apply("s").asInstanceOf[Symbol @@ String("s")], HNil))), Generic.instance[App.A, Int :: String :: shapeless.HNil](((x0$3: App.A) => x0$3 match {
//  case App.this.A((i$macro$10 @ _), (s$macro$11 @ _)) => ::.apply[Int, String :: shapeless.HNil.type](i$macro$10, ::.apply[String, shapeless.HNil.type](s$macro$11, HNil)).asInstanceOf[Int :: String :: shapeless.HNil]
//}), ((x0$4: Int :: String :: shapeless.HNil) => x0$4 match {
//  case ::((i$macro$8 @ _), ::((s$macro$9 @ _), HNil)) => App.this.A.apply(i$macro$8, s$macro$9)
//})), hlist.this.ZipWithKeys.hconsZipWithKeys[Symbol @@ String("i"), Int, (Symbol @@ String("s")) :: shapeless.HNil, String :: shapeless.HNil, shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](hlist.this.ZipWithKeys.hconsZipWithKeys[Symbol @@ String("s"), String, shapeless.HNil, shapeless.HNil, shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](hlist.this.ZipWithKeys.hnilZipWithKeys, Witness.mkWitness[Symbol with shapeless.tag.Tagged[String("s")]](scala.Symbol.apply("s").asInstanceOf[Symbol @@ String("s")].asInstanceOf[Symbol with shapeless.tag.Tagged[String("s")]])), Witness.mkWitness[Symbol with shapeless.tag.Tagged[String("i")]](scala.Symbol.apply("i").asInstanceOf[Symbol @@ String("i")].asInstanceOf[Symbol with shapeless.tag.Tagged[String("i")]])), scala.this.<:<.refl[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out]), shapeless.Lazy.apply[io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out]](inst$macro$12)).asInstanceOf[io.circe.generic.encoding.DerivedAsObjectEncoder[App.A]];
//      lazy val inst$macro$12: io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out] = ({
//  final class $anon extends io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out] {
//    def <init>() = {
//      super.<init>();
//      ()
//    };
//    private[this] val circeGenericEncoderFori = circe.this.Encoder.encodeInt;
//    private[this] val circeGenericEncoderFors = circe.this.Encoder.encodeString;
//    final def encodeObject(a: shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out): io.circe.JsonObject = a match {
//      case shapeless.::((circeGenericHListBindingFori @ _), shapeless.::((circeGenericHListBindingFors @ _), shapeless.HNil)) => io.circe.JsonObject.fromIterable(scala.collection.immutable.Vector.apply[(String, io.circe.Json)](scala.Tuple2.apply[String, io.circe.Json]("i", $anon.this.circeGenericEncoderFori.apply(circeGenericHListBindingFori)), scala.Tuple2.apply[String, io.circe.Json]("s", $anon.this.circeGenericEncoderFors.apply(circeGenericHListBindingFors))))
//    }
//  };
//  new $anon()
//}: io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out]).asInstanceOf[io.circe.generic.encoding.ReprAsObjectEncoder[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out]]
//    };
//    new anon$someEncoder$macro$13().inst$macro$1
//  };
//  _root_.shapeless.Lazy.apply[io.circe.generic.encoding.DerivedAsObjectEncoder[App.SomeTrait]](inst$macro$14)
//}

//scalac: {
//  val inst$macro$14: io.circe.generic.decoding.DerivedDecoder[App.SomeTrait] = {
//    final class anon$someDecoder$macro$13 extends _root_.scala.Serializable {
//      def <init>() = {
//        super.<init>();
//        ()
//      };
//      lazy val inst$macro$1: io.circe.generic.decoding.DerivedDecoder[App.SomeTrait] = decoding.this.DerivedDecoder.deriveDecoder[App.SomeTrait, shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](shapeless.this.LabelledGeneric.materializeCoproduct[App.SomeTrait, (Symbol @@ String("A")) :: shapeless.HNil, App.A :+: shapeless.CNil, shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](DefaultSymbolicLabelling.instance[App.SomeTrait, (Symbol @@ String("A")) :: shapeless.HNil](::.apply[Symbol @@ String("A"), shapeless.HNil.type](scala.Symbol.apply("A").asInstanceOf[Symbol @@ String("A")], HNil)), Generic.instance[App.SomeTrait, App.A :+: shapeless.CNil](((p: App.SomeTrait) => Coproduct.unsafeMkCoproduct((p: p: @_root_.scala.unchecked) match {
//  case (_: App.A) => 0
//}, p).asInstanceOf[App.A :+: shapeless.CNil]), ((x$1: App.A :+: shapeless.CNil) => Coproduct.unsafeGet(x$1).asInstanceOf[App.SomeTrait])), coproduct.this.ZipWithKeys.cpZipWithKeys[Symbol @@ String("A"), App.A, shapeless.HNil, shapeless.CNil](coproduct.this.ZipWithKeys.cnilZipWithKeys, Witness.mkWitness[Symbol with shapeless.tag.Tagged[String("A")]](scala.Symbol.apply("A").asInstanceOf[Symbol @@ String("A")].asInstanceOf[Symbol with shapeless.tag.Tagged[String("A")]])), scala.this.<:<.refl[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]), shapeless.Lazy.apply[io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]](inst$macro$2)).asInstanceOf[io.circe.generic.decoding.DerivedDecoder[App.SomeTrait]];
//      lazy val inst$macro$2: io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out] = ({
//  final class $anon extends io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out] {
//    def <init>() = {
//      super.<init>();
//      ()
//    };
//    private[this] val circeGenericDecoderForA = shapeless.Lazy.apply[io.circe.generic.decoding.DerivedDecoder[App.A]](inst$macro$3).value;
//    final def apply(c: io.circe.HCursor): io.circe.Decoder.Result[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out] = {
//      val result = c.downField("A");
//      if (result.succeeded)
//        scala.Some.apply[io.circe.Decoder.Result[App.A]]($anon.this.circeGenericDecoderForA.tryDecode(result))
//      else
//        scala.None
//    } match {
//      case scala.Some((result @ _)) => result match {
//        case scala.util.Right((v @ _)) => scala.util.Right.apply[Nothing, shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](ReprDecoder.injectLeftValue[Symbol @@ String("A"), App.A, shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](v))
//        case scala.util.Left((err @ _)) => scala.util.Left.apply[io.circe.DecodingFailure, Nothing](err)
//      }
//      case scala.None => (scala.util.Left.apply[io.circe.DecodingFailure, shapeless.CNil](io.circe.DecodingFailure.apply("JSON decoding to CNil should never happen", c.history)): scala.util.Either[io.circe.DecodingFailure, shapeless.CNil]) match {
//        case scala.util.Right((v @ _)) => scala.util.Right.apply[Nothing, shapeless.Inr[Nothing,shapeless.CNil]](shapeless.Inr.apply[Nothing, shapeless.CNil](v))
//        case scala.util.Left((err @ _)) => scala.util.Left.apply[io.circe.DecodingFailure, Nothing](err)
//      }
//    };
//    final override def decodeAccumulating(c: io.circe.HCursor): io.circe.Decoder.AccumulatingResult[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out] = {
//      val result = c.downField("A");
//      if (result.succeeded)
//        scala.Some.apply[io.circe.Decoder.AccumulatingResult[App.A]]($anon.this.circeGenericDecoderForA.tryDecodeAccumulating(result))
//      else
//        scala.None
//    } match {
//      case scala.Some((result @ _)) => result.map[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](((v: App.A) => ReprDecoder.injectLeftValue[Symbol @@ String("A"), App.A, shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out](v)))
//      case scala.None => cats.data.Validated.invalidNel[io.circe.DecodingFailure, shapeless.CNil](io.circe.DecodingFailure.apply("JSON decoding to CNil should never happen", c.history)).map[shapeless.Inr[Nothing,shapeless.CNil]](((x$3: shapeless.CNil) => shapeless.Inr.apply[Nothing, shapeless.CNil](x$3)))
//    }
//  };
//  new $anon()
//}: io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]).asInstanceOf[io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("A"),App.A] :+: shapeless.ops.coproduct.ZipWithKeys.cnilZipWithKeys.Out]];
//      lazy val inst$macro$3: io.circe.generic.decoding.DerivedDecoder[App.A] = decoding.this.DerivedDecoder.deriveDecoder[App.A, shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](shapeless.this.LabelledGeneric.materializeProduct[App.A, (Symbol @@ String("i")) :: (Symbol @@ String("s")) :: shapeless.HNil, Int :: String :: shapeless.HNil, shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](DefaultSymbolicLabelling.instance[App.A, (Symbol @@ String("i")) :: (Symbol @@ String("s")) :: shapeless.HNil](::.apply[Symbol @@ String("i"), (Symbol @@ String("s")) :: shapeless.HNil.type](scala.Symbol.apply("i").asInstanceOf[Symbol @@ String("i")], ::.apply[Symbol @@ String("s"), shapeless.HNil.type](scala.Symbol.apply("s").asInstanceOf[Symbol @@ String("s")], HNil))), Generic.instance[App.A, Int :: String :: shapeless.HNil](((x0$3: App.A) => x0$3 match {
//  case App.this.A((i$macro$10 @ _), (s$macro$11 @ _)) => ::.apply[Int, String :: shapeless.HNil.type](i$macro$10, ::.apply[String, shapeless.HNil.type](s$macro$11, HNil)).asInstanceOf[Int :: String :: shapeless.HNil]
//}), ((x0$4: Int :: String :: shapeless.HNil) => x0$4 match {
//  case ::((i$macro$8 @ _), ::((s$macro$9 @ _), HNil)) => App.this.A.apply(i$macro$8, s$macro$9)
//})), hlist.this.ZipWithKeys.hconsZipWithKeys[Symbol @@ String("i"), Int, (Symbol @@ String("s")) :: shapeless.HNil, String :: shapeless.HNil, shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](hlist.this.ZipWithKeys.hconsZipWithKeys[Symbol @@ String("s"), String, shapeless.HNil, shapeless.HNil, shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out](hlist.this.ZipWithKeys.hnilZipWithKeys, Witness.mkWitness[Symbol with shapeless.tag.Tagged[String("s")]](scala.Symbol.apply("s").asInstanceOf[Symbol @@ String("s")].asInstanceOf[Symbol with shapeless.tag.Tagged[String("s")]])), Witness.mkWitness[Symbol with shapeless.tag.Tagged[String("i")]](scala.Symbol.apply("i").asInstanceOf[Symbol @@ String("i")].asInstanceOf[Symbol with shapeless.tag.Tagged[String("i")]])), scala.this.<:<.refl[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out]), shapeless.Lazy.apply[io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out]](inst$macro$12)).asInstanceOf[io.circe.generic.decoding.DerivedDecoder[App.A]];
//      lazy val inst$macro$12: io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("i"),Int] :: shapeless.labelled.FieldType[Symbol @@ String("s"),String] :: shapeless.ops.hlist.ZipWithKeys.hnilZipWithKeys.Out] = ({
//  final class $anon extends io.circe.generic.decoding.ReprDecoder[shapeless.labelled.FieldType[Symbol @@ String("i

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