Decoding many, many fields with Circe.

circe.scala

import cats._
import cats.implicits._
import io.circe._
import io.circe.generic.semiauto._

implicit lazy val guildDecoder: Decoder[Guild] =
  (c: HCursor) =>
    implicitly[Monad[Either[DecodingFailure, ?]]] sequence Vector(
      c.downField("id").as[Snowflake],
      c.downField("name").as[String],
      c.downField("icon").as[Option[String]],
      c.downField("splash").as[Option[String]],
      c.downField("owner_id").as[Snowflake],
      c.downField("region").as[String],
      c.downField("afk_channel_id").as[Option[String]],
      c.downField("afk_timeout").as[Int],
      c.downField("embed_enabled").as[Option[Boolean]],
      c.downField("embed_channel_id").as[Option[Snowflake]],
      c.downField("verification_level").as[Int],
      c.downField("default_message_notifications").as[Int],
      c.downField("roles").as[Vector[Role]],
      c.downField("emojis").as[Vector[Emoji]],
      c.downField("features").as[Vector[String]],
      c.downField("mfa_level").as[Int],
      c.downField("joined_at").as[String],
      c.downField("large").as[Boolean],
      c.downField("unavailable").as[Boolean],
      c.downField("member_count").as[Int],
      c.downField("voice_states").as[Vector[VoiceState]],
      c.downField("members").as[Vector[GuildMember]],
      c.downField("channels").as[Vector[GuildChannel]],
      c.downField("presences").as[Vector[PresenceUpdate]]
    ) map { v =>
      Guild(
        id = v(0).asInstanceOf[Snowflake],
        name = v(1).asInstanceOf[String],
        icon = v(2).asInstanceOf[Option[String]],
        splash = v(3).asInstanceOf[Option[String]],
        ownerId = v(4).asInstanceOf[Snowflake],
        region = v(5).asInstanceOf[String],
        afkChannelId = v(6).asInstanceOf[Option[String]],
        afkTimeout = v(7).asInstanceOf[Int],
        embedEnabled = v(8).asInstanceOf[Option[Boolean]],
        embedChannelId = v(9).asInstanceOf[Option[Snowflake]],
        verificationLevel = v(10).asInstanceOf[Int],
        defaultMessageNotifications = v(11).asInstanceOf[Int],
        roles = v(12).asInstanceOf[Vector[Role]],
        emojis = v(13).asInstanceOf[Vector[Emoji]],
        features = v(14).asInstanceOf[Vector[String]],
        mfaLevel = v(15).asInstanceOf[Int],
        joinedAt = v(16).asInstanceOf[String],
        large = v(17).asInstanceOf[Boolean],
        unavailable = v(18).asInstanceOf[Boolean],
        memberCount = v(19).asInstanceOf[Int],
        voiceStates = v(20).asInstanceOf[Vector[VoiceState]],
        members = v(21).asInstanceOf[Vector[GuildMember]],
        channels = v(22).asInstanceOf[Vector[GuildChannel]],
        presences = v(23).asInstanceOf[Vector[PresenceUpdate]]
      )
    }