path: root/compiler/src/dotty/tools/dotc/core/Constants.scala

package dotty.tools.dotc
package core

import Types._, Symbols._, Contexts._
import printing.Printer

object Constants {

  final val NoTag      = 0
  final val UnitTag    = 1
  final val BooleanTag = 2
  final val ByteTag    = 3
  final val ShortTag   = 4
  final val CharTag    = 5
  final val IntTag     = 6
  final val LongTag    = 7
  final val FloatTag   = 8
  final val DoubleTag  = 9
  final val StringTag  = 10
  final val NullTag    = 11
  final val ClazzTag   = 12
  // For supporting java enumerations inside java annotations (see ClassfileParser)
  final val EnumTag    = 13

  case class Constant(value: Any) extends printing.Showable {
    import java.lang.Double.doubleToRawLongBits
    import java.lang.Float.floatToRawIntBits

    val tag: Int = value match {
      case null         => NullTag
      case x: Unit      => UnitTag
      case x: Boolean   => BooleanTag
      case x: Byte      => ByteTag
      case x: Short     => ShortTag
      case x: Int       => IntTag
      case x: Long      => LongTag
      case x: Float     => FloatTag
      case x: Double    => DoubleTag
      case x: String    => StringTag
      case x: Char      => CharTag
      case x: Type      => ClazzTag
      case x: Symbol    => EnumTag
      case _            => throw new Error("bad constant value: " + value + " of class " + value.getClass)
    }

    def isByteRange: Boolean  = isIntRange && Byte.MinValue <= intValue && intValue <= Byte.MaxValue
    def isShortRange: Boolean = isIntRange && Short.MinValue <= intValue && intValue <= Short.MaxValue
    def isCharRange: Boolean  = isIntRange && Char.MinValue <= intValue && intValue <= Char.MaxValue
    def isIntRange: Boolean   = ByteTag <= tag && tag <= IntTag
    def isLongRange: Boolean  = ByteTag <= tag && tag <= LongTag
    def isFloatRange: Boolean = ByteTag <= tag && tag <= FloatTag
    def isNumeric: Boolean    = ByteTag <= tag && tag <= DoubleTag
    def isNonUnitAnyVal       = BooleanTag <= tag && tag <= DoubleTag
    def isAnyVal              = UnitTag <= tag && tag <= DoubleTag

    def tpe(implicit ctx: Context): Type = tag match {
      case UnitTag    => defn.UnitType
      case BooleanTag => defn.BooleanType
      case ByteTag    => defn.ByteType
      case ShortTag   => defn.ShortType
      case CharTag    => defn.CharType
      case IntTag     => defn.IntType
      case LongTag    => defn.LongType
      case FloatTag   => defn.FloatType
      case DoubleTag  => defn.DoubleType
      case StringTag  => defn.StringType
      case NullTag    => defn.NullType
      case ClazzTag   => defn.ClassType(typeValue)
      case EnumTag    => defn.EnumType(symbolValue)
    }

    /** We need the equals method to take account of tags as well as values.
     */
    override def equals(other: Any): Boolean = other match {
      case that: Constant =>
        this.tag == that.tag && equalHashValue == that.equalHashValue
      case _ => false
    }

    def isNaN = value match {
      case f: Float  => f.isNaN
      case d: Double => d.isNaN
      case _ => false
    }

    def booleanValue: Boolean =
      if (tag == BooleanTag) value.asInstanceOf[Boolean]
      else throw new Error("value " + value + " is not a boolean")

    def byteValue: Byte = tag match {
      case ByteTag   => value.asInstanceOf[Byte]
      case ShortTag  => value.asInstanceOf[Short].toByte
      case CharTag   => value.asInstanceOf[Char].toByte
      case IntTag    => value.asInstanceOf[Int].toByte
      case LongTag   => value.asInstanceOf[Long].toByte
      case FloatTag  => value.asInstanceOf[Float].toByte
      case DoubleTag => value.asInstanceOf[Double].toByte
      case _         => throw new Error("value " + value + " is not a Byte")
    }

    def shortValue: Short = tag match {
      case ByteTag   => value.asInstanceOf[Byte].toShort
      case ShortTag  => value.asInstanceOf[Short]
      case CharTag   => value.asInstanceOf[Char].toShort
      case IntTag    => value.asInstanceOf[Int].toShort
      case LongTag   => value.asInstanceOf[Long].toShort
      case FloatTag  => value.asInstanceOf[Float].toShort
      case DoubleTag => value.asInstanceOf[Double].toShort
      case _         => throw new Error("value " + value + " is not a Short")
    }

    def charValue: Char = tag match {
      case ByteTag   => value.asInstanceOf[Byte].toChar
      case ShortTag  => value.asInstanceOf[Short].toChar
      case CharTag   => value.asInstanceOf[Char]
      case IntTag    => value.asInstanceOf[Int].toChar
      case LongTag   => value.asInstanceOf[Long].toChar
      case FloatTag  => value.asInstanceOf[Float].toChar
      case DoubleTag => value.asInstanceOf[Double].toChar
      case _         => throw new Error("value " + value + " is not a Char")
    }

    def intValue: Int = tag match {
      case ByteTag   => value.asInstanceOf[Byte].toInt
      case ShortTag  => value.asInstanceOf[Short].toInt
      case CharTag   => value.asInstanceOf[Char].toInt
      case IntTag    => value.asInstanceOf[Int]
      case LongTag   => value.asInstanceOf[Long].toInt
      case FloatTag  => value.asInstanceOf[Float].toInt
      case DoubleTag => value.asInstanceOf[Double].toInt
      case _         => throw new Error("value " + value + " is not an Int")
    }

    def longValue: Long = tag match {
      case ByteTag   => value.asInstanceOf[Byte].toLong
      case ShortTag  => value.asInstanceOf[Short].toLong
      case CharTag   => value.asInstanceOf[Char].toLong
      case IntTag    => value.asInstanceOf[Int].toLong
      case LongTag   => value.asInstanceOf[Long]
      case FloatTag  => value.asInstanceOf[Float].toLong
      case DoubleTag => value.asInstanceOf[Double].toLong
      case _         => throw new Error("value " + value + " is not a Long")
    }

    def floatValue: Float = tag match {
      case ByteTag   => value.asInstanceOf[Byte].toFloat
      case ShortTag  => value.asInstanceOf[Short].toFloat
      case CharTag   => value.asInstanceOf[Char].toFloat
      case IntTag    => value.asInstanceOf[Int].toFloat
      case LongTag   => value.asInstanceOf[Long].toFloat
      case FloatTag  => value.asInstanceOf[Float]
      case DoubleTag => value.asInstanceOf[Double].toFloat
      case _         => throw new Error("value " + value + " is not a Float")
    }

    def doubleValue: Double = tag match {
      case ByteTag   => value.asInstanceOf[Byte].toDouble
      case ShortTag  => value.asInstanceOf[Short].toDouble
      case CharTag   => value.asInstanceOf[Char].toDouble
      case IntTag    => value.asInstanceOf[Int].toDouble
      case LongTag   => value.asInstanceOf[Long].toDouble
      case FloatTag  => value.asInstanceOf[Float].toDouble
      case DoubleTag => value.asInstanceOf[Double]
      case _         => throw new Error("value " + value + " is not a Double")
    }

    /** Convert constant value to conform to given type.
     */
    def convertTo(pt: Type)(implicit ctx: Context): Constant = {
      def classBound(pt: Type): Type = pt.dealias.stripTypeVar match {
        case tref: TypeRef if !tref.symbol.isClass => classBound(tref.info.bounds.lo)
        case param: TypeParamRef =>
          ctx.typerState.constraint.entry(param) match {
            case TypeBounds(lo, hi) =>
              if (hi.classSymbol.isPrimitiveValueClass) hi //constrain further with high bound
              else classBound(lo)
            case NoType => classBound(param.binder.paramInfos(param.paramNum).lo)
            case inst => classBound(inst)
          }
        case pt => pt
      }
      val target = classBound(pt).typeSymbol
      if (target == tpe.typeSymbol)
        this
      else if ((target == defn.ByteClass) && isByteRange)
        Constant(byteValue)
      else if (target == defn.ShortClass && isShortRange)
        Constant(shortValue)
      else if (target == defn.CharClass && isCharRange)
        Constant(charValue)
      else if (target == defn.IntClass && isIntRange)
        Constant(intValue)
      else if (target == defn.LongClass && isLongRange)
        Constant(longValue)
      else if (target == defn.FloatClass && isFloatRange)
        Constant(floatValue)
      else if (target == defn.DoubleClass && isNumeric)
        Constant(doubleValue)
      else
        null
    }

    def stringValue: String = value.toString

    def toText(printer: Printer) = printer.toText(this)

    def typeValue: Type     = value.asInstanceOf[Type]
    def symbolValue: Symbol = value.asInstanceOf[Symbol]

    /**
     * Consider two `NaN`s to be identical, despite non-equality
     * Consider -0d to be distinct from 0d, despite equality
     *
     * We use the raw versions (i.e. `floatToRawIntBits` rather than `floatToIntBits`)
     * to avoid treating different encodings of `NaN` as the same constant.
     * You probably can't express different `NaN` varieties as compile time
     * constants in regular Scala code, but it is conceivable that you could
     * conjure them with a macro.
     */
    private def equalHashValue: Any = value match {
      case f: Float  => floatToRawIntBits(f)
      case d: Double => doubleToRawLongBits(d)
      case v         => v
    }

    override def hashCode: Int = {
      import scala.util.hashing.MurmurHash3._
      val seed = 17
      var h = seed
      h = mix(h, tag.##) // include tag in the hash, otherwise 0, 0d, 0L, 0f collide.
      h = mix(h, equalHashValue.##)
      finalizeHash(h, length = 2)
    }
  }
}