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/* NSC -- new scala compiler
* Copyright 2005 LAMP/EPFL
* @author Martin Odersky
*/
// $Id$
package scala.tools.nsc.typechecker;
abstract class ConstantFolder {
val global: Global;
import global._;
import definitions._;
private val NoValue = new Object();
/** If tree is a constant operation, replace with result. */
def apply(tree: Tree): Tree = fold(tree, tree match {
case Apply(Select(Literal(x), op), List(Literal(y))) => foldBinop(op, x, y)
case Select(Literal(x), op) => foldUnop(op, x)
case _ => NoValue
});
/** If tree is a constant value that can be converted to type `pt', perform the conversion */
def apply(tree: Tree, pt: Type): Tree = fold(tree, tree.tpe match {
case ConstantType(base, value) => foldTyped(value, pt)
case _ => NoValue
});
private def fold(tree: Tree, value: Any): Tree =
if (value != NoValue && value != ()) tree setType ConstantType(literalType(value), value)
else tree;
private def foldUnop(op: Name, value: Any): Any = Pair(op, value) match {
case Pair(nme.ZNOT, x: boolean) => !x
case Pair(nme.NOT , x: int ) => ~x
case Pair(nme.NOT , x: long ) => ~x
case Pair(nme.ADD , x: int ) => +x
case Pair(nme.ADD , x: long ) => +x
case Pair(nme.ADD , x: float ) => +x
case Pair(nme.ADD , x: double ) => +x
case Pair(nme.SUB , x: int ) => -x
case Pair(nme.SUB , x: long ) => -x
case Pair(nme.SUB , x: float ) => -x
case Pair(nme.SUB , x: double ) => -x
case _ => NoValue
}
private def foldBinop(op: Name, lvalue: Any, rvalue: Any): Any = Triple(op, lvalue, rvalue) match {
case Triple(nme.ZOR , x: boolean, y: boolean) => x | y
case Triple(nme.OR , x: boolean, y: boolean) => x | y
case Triple(nme.OR , x: int , y: int ) => x | y
case Triple(nme.OR , x: long , y: long ) => x | y
case Triple(nme.XOR , x: boolean, y: boolean) => x ^ y
case Triple(nme.XOR , x: int , y: int ) => x ^ y
case Triple(nme.XOR , x: long , y: long ) => x ^ y
case Triple(nme.ZAND, x: boolean, y: boolean) => x & y
case Triple(nme.AND , x: boolean, y: boolean) => x & y
case Triple(nme.AND , x: int , y: int ) => x & y
case Triple(nme.AND , x: long , y: long ) => x & y
case Triple(nme.LSL , x: int , y: int ) => x << y
case Triple(nme.LSL , x: long , y: int ) => x << y
case Triple(nme.LSL , x: long , y: long ) => x << y
case Triple(nme.LSR , x: int , y: int ) => x >>> y
case Triple(nme.LSR , x: long , y: int ) => x >>> y
case Triple(nme.LSR , x: long , y: long ) => x >>> y
case Triple(nme.ASR , x: int , y: int ) => x >> y
case Triple(nme.ASR , x: long , y: int ) => x >> y
case Triple(nme.ASR , x: long , y: long ) => x >> y
case Triple(nme.EQ , x: boolean, y: boolean) => x == y
case Triple(nme.EQ , x: int , y: int ) => x == y
case Triple(nme.EQ , x: long , y: long ) => x == y
case Triple(nme.EQ , x: float , y: float ) => x == y
case Triple(nme.EQ , x: double , y: double ) => x == y
case Triple(nme.NE , x: boolean, y: boolean) => x != y
case Triple(nme.NE , x: int , y: int ) => x != y
case Triple(nme.NE , x: long , y: long ) => x != y
case Triple(nme.NE , x: float , y: float ) => x != y
case Triple(nme.NE , x: double , y: double ) => x != y
case Triple(nme.LT , x: int , y: int ) => x < y
case Triple(nme.LT , x: long , y: long ) => x < y
case Triple(nme.LT , x: float , y: float ) => x < y
case Triple(nme.LT , x: double , y: double ) => x < y
case Triple(nme.GT , x: int , y: int ) => x > y
case Triple(nme.GT , x: long , y: long ) => x > y
case Triple(nme.GT , x: float , y: float ) => x > y
case Triple(nme.GT , x: double , y: double ) => x > y
case Triple(nme.LE , x: int , y: int ) => x <= y
case Triple(nme.LE , x: long , y: long ) => x <= y
case Triple(nme.LE , x: float , y: float ) => x <= y
case Triple(nme.LE , x: double , y: double ) => x <= y
case Triple(nme.GE , x: int , y: int ) => x >= y
case Triple(nme.GE , x: long , y: long ) => x >= y
case Triple(nme.GE , x: float , y: float ) => x >= y
case Triple(nme.GE , x: double , y: double ) => x >= y
case Triple(nme.ADD , x: int , y: int ) => x + y
case Triple(nme.ADD , x: long , y: long ) => x + y
case Triple(nme.ADD , x: float , y: float ) => x + y
case Triple(nme.ADD , x: double , y: double ) => x + y
case Triple(nme.ADD , x: String , y: String ) => x + y
case Triple(nme.SUB , x: int , y: int ) => x - y
case Triple(nme.SUB , x: long , y: long ) => x - y
case Triple(nme.SUB , x: float , y: float ) => x - y
case Triple(nme.SUB , x: double , y: double ) => x - y
case Triple(nme.MUL , x: int , y: int ) => x * y
case Triple(nme.MUL , x: long , y: long ) => x * y
case Triple(nme.MUL , x: float , y: float ) => x * y
case Triple(nme.MUL , x: double , y: double ) => x * y
case Triple(nme.DIV , x: int , y: int ) => x / y
case Triple(nme.DIV , x: long , y: long ) => x / y
case Triple(nme.DIV , x: float , y: float ) => x / y
case Triple(nme.DIV , x: double , y: double ) => x / y
case Triple(nme.MOD , x: int , y: int ) => x % y
case Triple(nme.MOD , x: long , y: long ) => x % y
case Triple(nme.MOD , x: float , y: float ) => x % y
case Triple(nme.MOD , x: double , y: double ) => x % y
case _ => NoValue
}
/** Widen constant value to conform to given type */
private def foldTyped(value: Any, pt: Type): Any = {
val target = pt.symbol;
value match {
case x: byte =>
if (target == ShortClass) x.asInstanceOf[short]
else if (target == CharClass) x.asInstanceOf[char]
else if (target == IntClass) x.asInstanceOf[int]
else if (target == LongClass) x.asInstanceOf[long]
else if (target == FloatClass) x.asInstanceOf[float]
else if (target == DoubleClass) x.asInstanceOf[double]
else NoValue
case x: short =>
if (target == IntClass) x.asInstanceOf[int]
else if (target == LongClass) x.asInstanceOf[long]
else if (target == FloatClass) x.asInstanceOf[float]
else if (target == DoubleClass) x.asInstanceOf[double]
else NoValue
case x: char =>
if (target == IntClass) x.asInstanceOf[int]
else if (target == LongClass) x.asInstanceOf[long]
else if (target == FloatClass) x.asInstanceOf[float]
else if (target == DoubleClass) x.asInstanceOf[double]
else NoValue
case x: int =>
if (target == ByteClass && -128 <= x && x <= 127) x.asInstanceOf[byte]
else if (target == ShortClass && -32768 <= x && x <= 32767) x.asInstanceOf[short]
else if (target == CharClass && 0 <= x && x <= 65535) x.asInstanceOf[char]
else if (target == LongClass) x.asInstanceOf[long]
else if (target == FloatClass) x.asInstanceOf[float]
else if (target == DoubleClass) x.asInstanceOf[double]
else NoValue
case x: long =>
if (target == FloatClass) x.asInstanceOf[float]
else if (target == DoubleClass) x.asInstanceOf[double]
else NoValue
case x: float =>
if (target == DoubleClass) x.asInstanceOf[double]
else NoValue
case x =>
NoValue
}
}
def literalType(value: Any): Type =
if (value.isInstanceOf[unit]) UnitClass.tpe
else if (value.isInstanceOf[boolean]) BooleanClass.tpe
else if (value.isInstanceOf[byte]) ByteClass.tpe
else if (value.isInstanceOf[short]) ShortClass.tpe
else if (value.isInstanceOf[char]) CharClass.tpe
else if (value.isInstanceOf[int]) IntClass.tpe
else if (value.isInstanceOf[long]) LongClass.tpe
else if (value.isInstanceOf[float]) FloatClass.tpe
else if (value.isInstanceOf[double]) DoubleClass.tpe
else if (value.isInstanceOf[String]) StringClass.tpe
else if (value == null) AllRefClass.tpe
else throw new FatalError("unexpected literal value: " + value);
}
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