com.avsystem.commons.macros.misc.SealedMacros.scala Maven / Gradle / Ivy

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AVSystem commons library for Scala

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package com.avsystem.commons
package macros.misc

import com.avsystem.commons.macros.AbstractMacroCommons

import scala.reflect.macros.blackbox

class SealedMacros(ctx: blackbox.Context) extends AbstractMacroCommons(ctx) {

  import c.universe._

  final lazy val OrderedEnumType: Type = staticType(tq"$MiscPkg.OrderedEnum")

  def caseObjectsFor[T: WeakTypeTag]: Tree = instrument {
    val tpe = weakTypeOf[T]
    knownSubtypes(tpe).map { subtypes =>
      val objects = subtypes.map(subTpe => singleValueFor(subTpe)
        .getOrElse(abort(s"All possible values of a SealedEnum must be objects but $subTpe is not")))
      val result = q"$ListObj(..$objects)"
      if (tpe <:< OrderedEnumType) q"$result.sorted" else result
    }.getOrElse(abort(s"$tpe is not a sealed trait or class"))
  }

  def instancesFor[TC: WeakTypeTag, T: WeakTypeTag]: Tree = instrument {
    val tpe = weakTypeOf[T]
    def instanceTpe(forTpe: Type): Type = weakTypeOf[TC] match {
      case TypeRef(pre, sym, Nil) => internal.typeRef(pre, sym, List(forTpe))
      case _ => abort(s"expected type constructor")
    }
    val subtypes = knownSubtypes(tpe).getOrElse(abort(s"$tpe is not a sealed hierarchy root"))
    q"${subtypes.map(st => q"""$ImplicitsObj.infer[${instanceTpe(st)}]("")""")}"
  }
}