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/* NSC -- new Scala compiler
* Copyright 2005-2007 LAMP/EPFL
* Copyright 2007 Google Inc. All Rights Reserved.
* Author: bqe@google.com (Burak Emir)
*/
// $Id$
package scala.tools.nsc.matching
/** Translation of pattern matching
*
* @author Burak Emir
*/
trait TransMatcher { self: transform.ExplicitOuter with PatternNodes with ParallelMatching with CodeFactory =>
import global._
import definitions._
import posAssigner.atPos
import symtab.Flags
import typer.typed
import collection.mutable.ListBuffer
var cunit: CompilationUnit = _ // memory leak?
def fresh = cunit.fresh
var nPatterns = 0
var resultType: Type = _
// cache these
final val settings_debug = settings.debug.value
final val settings_squeeze = settings.Xsqueeze.value == "on"
final val settings_casetags = settings.Xcasetags.value == "on"
final def hasRegularPattern(pats1: List[Tree]): Boolean = {
var pats = pats1; while(pats ne Nil) {
if(isRegularPattern(pats.head)) { return true; } else { pats = pats.tail }
}
return false
}
final def isRegularPattern(pat: Tree): Boolean = {
pat match {
case Alternative(trees) => hasRegularPattern(trees)
case Star(t) => true
case Ident(_) => false
case Bind(n, pat1) => isRegularPattern(pat1)
case Sequence(trees) => true // cause there are ArrayValues now
case ArrayValue(tt, trees) => hasRegularPattern(trees)
case Apply(fn, trees) => hasRegularPattern(trees)
case Literal(_) => false
case Select(_, _) => false
case Typed(_, _) => false
case UnApply(_,trees) => hasRegularPattern(trees)
}
}
// @todo: this should be isNotRegular :-/ premature opt src of all evil
// check special case Seq(p1,...,pk,_*) where pi not regular
protected def isRightIgnoring(p: ArrayValue): Boolean = {
def isDefaultStar(p: Tree): Boolean = p match {
case Bind(_, q) => isDefaultStar(q)
case Star(Ident(nme.WILDCARD)) => true
case _ => false
}
p match {
case ArrayValue(s, trees) =>
var ts = trees
var c: Tree = null
while ((ts ne Nil) && {c = ts.head; ts = ts.tail; !isRegularPattern(c)}) {}
(ts eq Nil) && isDefaultStar(c)
}
}
/** a casedef with sequence subpatterns like
*
* case ..x @ ().. => body
*
* should be replaced straight away with
*
* case .. () .. => val x = Nil; body
*/
def isRegular(pats: List[CaseDef]): (List[CaseDef],Boolean) = {
var existsReg = false
var isReg = false
var nilVars: List[Symbol] = null
def isRegular1(pat: Tree): Tree = pat match {
case Alternative(trees) =>
copy.Alternative(pat, trees map { isRegular1 })
case Star(t) =>
isReg = true; copy.Star(pat, isRegular1(t))
case Ident(_) =>
pat
case Bind(id, empt @ Sequence(List())) =>
nilVars = pat.symbol :: nilVars
empt
case Bind(n, pat1) =>
copy.Bind(pat, n, isRegular1(pat1))
case Sequence(trees) =>
isReg = true
copy.Sequence(pat, trees map { isRegular1 })
case UnApply(fn, args) => copy.UnApply(pat, fn, args map { isRegular1 })
case app @ Apply(fn, List(pat2@ ArrayValue( tt, List(b @ Bind(id, Star(wc @ Ident(nme.WILDCARD))))))) if (app.tpe.typeSymbol.flags & Flags.CASE) == 0 =>
val tpe1:Type = pat2.tpe.widen.baseType( definitions.SeqClass ).typeArgs(0)
val tpe = appliedType(definitions.SeqClass.typeConstructor, List(tpe1))
b.symbol.setInfo(tpe)
b.setType(tpe)
copy.Bind(b, id, wc)
case app @ Apply(fn, List(pat2@ ArrayValue( tt, List(b @ Bind(id, Star(wc @ Ident(nme.WILDCARD))))))) => // a pattern of the form MyCaseConstructor(foo@_*)
val tpe1:Type = pat2.tpe.widen.baseType( definitions.SeqClass ).typeArgs(0)
val tpe = appliedType(definitions.SeqClass.typeConstructor, List(tpe1))
b.symbol.setInfo(tpe)
b.setType(tpe)
copy.Apply(pat, fn, List(copy.Bind(b, id, wc)))
case av @ ArrayValue(s, trees) =>
if (isRightIgnoring(av)) pat
else copy.ArrayValue(pat, s, (trees map { isRegular1 }))
case Apply(fn, List(Sequence(List()))) =>
pat
case Apply(fn, trees) =>
copy.Apply(pat, fn, (trees map { isRegular1 }))
case Literal(_) =>
pat
case Select(_, _) =>
pat
case Typed(_, _) =>
pat
case This(_) =>
val stpe = mkThisType(pat.tpe.typeSymbol)
Typed(Ident(nme.WILDCARD) setType stpe, TypeTree(stpe))
}
var res = new ListBuffer[CaseDef]
val it = pats.elements; while (it.hasNext) {
nilVars = Nil
val cdef = it.next
val newt = isRegular1(cdef.pat)
existsReg = existsReg || isReg
val nbody = if (nilVars.isEmpty) cdef.body else
atPos(cdef.body.pos)(
Block(nilVars map {
x => ValDef(x, Ident(definitions.NilModule))
}, cdef.body)
)
res += copy.CaseDef(cdef, newt, cdef.guard, nbody)
}
(res.toList, existsReg)
}
/** handles all translation of pattern matching
*/
def handlePattern(selector: Tree, ocases: List[CaseDef], doCheckExhaustive: Boolean, owner: Symbol, handleOuter: Tree => Tree): Tree = {
val (cases, containsReg) = isRegular(ocases)
// @todo: remove unused variables
if (containsReg) {
cunit.error(selector.pos, "regular expressions not yet implemented")
//sel
EmptyTree
} else {
implicit val theOwner = owner
if (settings_debug) {
Console.println("****")
Console.println("**** initalize, selector = "+selector+" selector.tpe = "+selector.tpe)
Console.println("**** doCheckExhaustive == "+doCheckExhaustive)
}
implicit val rep = new RepFactory(handleOuter)
try {
val tmps = new ListBuffer[Symbol]
val vds = new ListBuffer[Tree]
var root:Symbol = newVar(selector.pos, selector.tpe)
if (!doCheckExhaustive)
root.setFlag(symtab.Flags.TRANS_FLAG)
var vdef:Tree = typed{ValDef(root, selector)}
var theFailTree:Tree = ThrowMatchError(selector.pos, mkIdent(root))
if (definitions.isTupleType(selector.tpe)) selector match {
case app @ Apply(fn, args)
if (fn.symbol eq selector.tpe.decls.lookup(nme.CONSTRUCTOR)) &&
(cases forall { x => x match {
case CaseDef(Apply(fn, pargs),_,_) => true ;
case CaseDef(Ident(nme.WILDCARD),_,_) => true ;
case _ => false
}}) =>
var i = 0
var as = args
while(as ne Nil) {
val ti = as.head
val v = newVar(ti.pos, cunit.fresh.newName("tp"), selector.tpe.typeArgs(i))
if (!doCheckExhaustive)
v.setFlag(symtab.Flags.TRANS_FLAG)
vds += typedValDef(v, ti)
tmps += v
i = i + 1
as = as.tail
}
theFailTree = ThrowMatchError(selector.pos, copy.Apply(app, fn, tmps.toList map mkIdent))
case _ =>
tmps += root
vds += vdef
} else {
tmps += root
vds += vdef
}
val irep = initRep(tmps.toList, cases, rep)
implicit val fail: Tree = theFailTree
val mch = typed{ repToTree(irep)}
var dfatree = typed{Block(vds.toList, mch)}
// cannot use squeezedBlock because of side-effects, see t275
//DEBUG("**** finished\n"+dfatree.toString)
var bx = 0; var cs = cases; while(cs ne Nil) {
if (!rep.isReached(bx)) {
cunit.error(cs.head.asInstanceOf[CaseDef].body.pos, "unreachable code")
}
cs = cs.tail
bx += 1
}
dfatree = rep.cleanup(dfatree)
resetTrav.traverse(dfatree)
return dfatree
} catch {
case e => e.printStackTrace(); throw new FatalError(e.getMessage())
}
}
}
object resetTrav extends Traverser {
override def traverse(x: Tree): Unit = x match {
case vd @ ValDef(_, _, _, _) =>
if (vd.symbol hasFlag symtab.Flags.SYNTHETIC) {
vd.symbol resetFlag symtab.Flags.TRANS_FLAG
vd.symbol resetFlag symtab.Flags.MUTABLE
}
case _ =>
super.traverse(x)
}
}
}
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