Integration of Constants

1 files changed, 214 insertions, 4 deletions

diff --git a/src/dotty/tools/dotc/core/Constants.scala b/src/dotty/tools/dotc/core/Constants.scala
index 94e22cdd4..825ce60f1 100644
--- a/src/dotty/tools/dotc/core/Constants.scala
+++ b/src/dotty/tools/dotc/core/Constants.scala
@@ -1,12 +1,222 @@
 package dotty.tools.dotc
 package core
 
-import Types._
+import Types._, Symbols._, Contexts._
 
 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) {
-    def tpe: Type = ???
-  }
+    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.UnitClass.typeConstructor
+      case BooleanTag => defn.BooleanClass.typeConstructor
+      case ByteTag    => defn.ByteClass.typeConstructor
+      case ShortTag   => defn.ShortClass.typeConstructor
+      case CharTag    => defn.CharClass.typeConstructor
+      case IntTag     => defn.IntClass.typeConstructor
+      case LongTag    => defn.LongClass.typeConstructor
+      case FloatTag   => defn.FloatClass.typeConstructor
+      case DoubleTag  => defn.DoubleClass.typeConstructor
+      case StringTag  => defn.StringClass.typeConstructor
+      case NullTag    => defn.NullClass.typeConstructor
+      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")
+    }
 
-}
\ No newline at end of file
+    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 = {
+      val target = 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 show(implicit ctx: Context) = ctx.show(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)
+    }
+  }
+}