/* NSC -- new Scala compiler * Copyright 2005-2011 LAMP/EPFL * @author Martin Odersky */ package scala.tools.nsc package typechecker import scala.collection.mutable.ListBuffer import symtab.Flags._ /** This trait ... * * @author Martin Odersky * @version 1.0 */ trait EtaExpansion { self: Analyzer => import global._ object etaExpansion { private def isMatch(vparam: ValDef, arg: Tree) = arg match { case Ident(name) => vparam.name == name case _ => false } def unapply(tree: Tree): Option[(List[ValDef], Tree, List[Tree])] = tree match { case Function(vparams, Apply(fn, args)) if (vparams corresponds args)(isMatch) => Some((vparams, fn, args)) case _ => None } } /**
* Expand partial function applications of type type
.
*
* p.f(es_1)...(es_n) * ==> { * private synthetic val eta$f = p.f // if p is not stable * ... * private synthetic val eta$e_i = e_i // if e_i is not stable * ... * (ps_1 => ... => ps_m => eta$f([es_1])...([es_m])(ps_1)...(ps_m)) * }*
* tree is already attributed *
*/ def etaExpand(unit : CompilationUnit, tree: Tree): Tree = { val tpe = tree.tpe var cnt = 0 // for NoPosition def freshName() = { cnt += 1 unit.freshTermName("eta$" + (cnt - 1) + "$") } val defs = new ListBuffer[Tree] /** Append todefs
value definitions for all non-stable
* subexpressions of the function application tree
.
*
* @param tree ...
* @return ...
*/
def liftoutPrefix(tree: Tree): Tree = {
def liftout(tree: Tree): Tree =
if (treeInfo.isExprSafeToInline(tree)) tree
else {
val vname: Name = freshName()
// Problem with ticket #2351 here
defs += atPos(tree.pos) {
ValDef(Modifiers(SYNTHETIC), vname.toTermName, TypeTree(), tree)
}
Ident(vname) setPos tree.pos.focus
}
val tree1 = tree match {
// a partial application using named arguments has the following form:
// { val qual$1 = qual
// val x$1 = arg1
// [...]
// val x$n = argn
// qual$1.fun(x$1, ..)..(.., x$n) }
// Eta-expansion has to be performed on `fun`
case Block(stats, fun) =>
defs ++= stats
liftoutPrefix(fun)
case Apply(fn, args) =>
treeCopy.Apply(tree, liftoutPrefix(fn), args mapConserve (liftout)) setType null
case TypeApply(fn, args) =>
treeCopy.TypeApply(tree, liftoutPrefix(fn), args) setType null
case Select(qual, name) =>
treeCopy.Select(tree, liftout(qual), name) setSymbol NoSymbol setType null
case Ident(name) =>
tree
}
if (tree1 ne tree) tree1 setPos tree1.pos.makeTransparent
tree1
}
/** Eta-expand lifted tree.
*/
def expand(tree: Tree, tpe: Type): Tree = tpe match {
case mt @ MethodType(paramSyms, restpe) if !mt.isImplicit =>
val params = paramSyms map (sym =>
ValDef(Modifiers(SYNTHETIC | PARAM),
sym.name.toTermName, TypeTree(sym.tpe) , EmptyTree))
atPos(tree.pos.makeTransparent) {
Function(params, expand(Apply(tree, params map gen.paramToArg), restpe))
}
case _ =>
tree
}
val tree1 = liftoutPrefix(tree)
atPos(tree.pos)(Block(defs.toList, expand(tree1, tpe)))
}
}