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/* NSC -- new Scala compiler
* Copyright 2005-2009 LAMP/EPFL
* @author Martin Odersky
*/
// $Id$
package scala.tools.nsc.typechecker
import scala.collection.mutable.ListBuffer
import symtab.Flags._
/** This trait ...
*
* @author Martin Odersky
* @version 1.0
*/
trait EtaExpansion { self: Analyzer =>
import global._
import posAssigner.atPos
object etaExpansion {
def unapply(tree: Tree): Option[(List[ValDef], Tree, List[Tree])] = tree match {
case Function(vparams, Apply(fn, args))
if (List.forall2(vparams, args) {
case (vparam, Ident(name)) => vparam.name == name
case _ => false
}) =>
Some((vparams, fn, args))
case _ =>
None
}
}
/** <p>
* Expand partial function applications of type <code>type</code>.
* </p><pre>
* p.f(es_1)...(es_n)
* ==> {
* <b>private synthetic val</b> eta$f = p.f // if p is not stable
* ...
* <b>private synthetic val</b> eta$e_i = e_i // if e_i is not stable
* ...
* (ps_1 => ... => ps_m => eta$f([es_1])...([es_m])(ps_1)...(ps_m))
* }</pre>
* <p>
* tree is already attributed
* </p>
*/
def etaExpand(unit : CompilationUnit, tree: Tree): Tree = {
val tpe = tree.tpe
val symbolHash = if (!inIDE) "" else Integer.toString(tree.symbol.hashCode, 10 + ('z' - 'a')) + "$"
var cnt = 0 // for NoPosition
def freshName(pos : util.Position, n : Int) = {
cnt += 1
if (!inIDE) {
newTermName(unit.fresh.newName(pos, "eta$" + (cnt - 1) + "$"))
} else if (pos == util.NoPosition) {
// nothing we can do, hope for no conflict!
newTermName(("eta$" + symbolHash + (cnt - 1)))
} else
newTermName(unit.fresh.newName(pos, "eta$" + symbolHash + (cnt - 1) + "$"))
// Martin to Sean: I removed the
// else if (n == 0) branch and changed `n' in the line above to `(cnt - 1)'
// this was necessary because otherwise curried eta-expansions would get the same
// symbol. An example which failes test/files/run/Course-2002-02.scala
// todo: review and get rid of the `n' argument (which is unused right now).
}
// { cnt = cnt + 1; newTermName("eta$" + cnt) }
val defs = new ListBuffer[Tree]
/** Append to <code>defs</code> value definitions for all non-stable
* subexpressions of the function application <code>tree</code>.
*
* @param tree ...
* @return ...
*/
def liftoutPrefix(tree: Tree): Tree = {
def liftout(tree: Tree): Tree =
if (treeInfo.isPureExpr(tree)) tree
else {
val vname: Name = freshName(tree.pos, 0)
defs += atPos(tree.pos)(ValDef(Modifiers(SYNTHETIC), vname, TypeTree(), tree))
Ident(vname) setPos tree.pos
}
tree match {
case Apply(fn, args) =>
copy.Apply(tree, liftoutPrefix(fn), List.mapConserve(args)(liftout)) setType null
case TypeApply(fn, args) =>
copy.TypeApply(tree, liftoutPrefix(fn), args) setType null
case Select(qual, name) =>
copy.Select(tree, liftout(qual), name) setSymbol NoSymbol setType null
case Ident(name) =>
tree
}
}
/** Eta-expand lifted tree.
*
* @param tree ...
* @param tpe ...
* @return ...
*/
def expand(tree: Tree, tpe: Type): Tree = tpe match {
case mt: ImplicitMethodType =>
tree
case MethodType(formals, restpe) =>
var cnt0 = 0
def cnt = {
cnt0 += 1
cnt0 - 1
}
val params = formals map (formal =>
ValDef(Modifiers(SYNTHETIC | PARAM), freshName(tree.pos, cnt), TypeTree(formal), EmptyTree))
atPos(tree.pos)(Function(params, expand(Apply(tree, params map gen.paramToArg), restpe)))
//atPos(tree.pos)(Function(params, expand(Apply(tree, args), restpe)))
case _ =>
tree
}
val tree1 = liftoutPrefix(tree)
atPos(tree.pos)(Block(defs.toList, expand(tree1, tpe)))
}
}
|
