io.circe.generic.util.macros.ExportMacros.scala Maven / Gradle / Ivy

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package io.circe.generic.util.macros

import io.circe.{ Decoder, ObjectEncoder }
import io.circe.export.Exported
import io.circe.generic.decoding.DerivedDecoder
import io.circe.generic.encoding.DerivedObjectEncoder
import macrocompat.bundle
import scala.reflect.macros.whitebox

@bundle
class ExportMacros(val c: whitebox.Context) {
  import c.universe._

  final def exportDecoder[D[x] <: DerivedDecoder[x], A](implicit
    D: c.WeakTypeTag[D[_]],
    A: c.WeakTypeTag[A]
  ): c.Expr[Exported[Decoder[A]]] = {
    val target = appliedType(D.tpe.typeConstructor, A.tpe)

    c.typecheck(q"_root_.shapeless.lazily[$target]", silent = true) match {
      case EmptyTree => c.abort(c.enclosingPosition, s"Unable to infer value of type $target")
      case t => c.Expr[Exported[Decoder[A]]](
        q"new _root_.io.circe.export.Exported($t: _root_.io.circe.Decoder[$A])"
      )
    }
  }

  final def exportEncoder[E[x] <: DerivedObjectEncoder[x], A](implicit
    E: c.WeakTypeTag[E[_]],
    A: c.WeakTypeTag[A]
  ): c.Expr[Exported[ObjectEncoder[A]]] = {
    val target = appliedType(E.tpe.typeConstructor, A.tpe)

    c.typecheck(q"_root_.shapeless.lazily[$target]", silent = true) match {
      case EmptyTree => c.abort(c.enclosingPosition, s"Unable to infer value of type $target")
      case t => c.Expr[Exported[ObjectEncoder[A]]](
        q"new _root_.io.circe.export.Exported($t: _root_.io.circe.ObjectEncoder[$A])"
      )
    }
  }
}