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/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Martin odersky
*/
package scala.tools.nsc
package transform
/** This phase maps ErasedValueTypes to the underlying unboxed representation and
* performs peephole optimizations.
*/
trait PostErasure extends InfoTransform with TypingTransformers {
val global: Global
import global._
import treeInfo._
val phaseName: String = "posterasure"
def newTransformer(unit: CompilationUnit): Transformer = new PostErasureTransformer(unit)
override def changesBaseClasses = false
object elimErasedValueType extends TypeMap {
def apply(tp: Type) = tp match {
case ConstantType(Constant(tp: Type)) => ConstantType(Constant(apply(tp)))
case ErasedValueType(tref) => enteringErasure(erasure.erasedValueClassArg(tref))
case _ => mapOver(tp)
}
}
def transformInfo(sym: Symbol, tp: Type) = elimErasedValueType(tp)
class PostErasureTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {
override def transform(tree: Tree) = {
def finish(res: Tree) = logResult(s"Posterasure reduction\n Old: $tree\n New")(res)
/** We use the name of the operation being performed and not the symbol
* itself because the symbol hails from the boxed class, and this transformation
* exists to operate directly on the values. So we are for instance looking
* up == on an lhs of type Int, whereas the symbol which has been passed in
* is from java.lang.Integer.
*/
def binop(lhs: Tree, op: Symbol, rhs: Tree) =
finish(localTyper typed (Apply(Select(lhs, op.name) setPos tree.pos, rhs :: Nil) setPos tree.pos))
super.transform(tree) setType elimErasedValueType(tree.tpe) match {
case AsInstanceOf(v, tpe) if v.tpe <:< tpe => finish(v) // x.asInstanceOf[X] ==> x
case ValueClass.BoxAndUnbox(v) => finish(v) // (new B(v)).unbox ==> v
case ValueClass.BoxAndCompare(v1, op, v2) => binop(v1, op, v2) // new B(v1) == new B(v2) ==> v1 == v2
case tree => tree
}
}
}
}
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