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/* NSC -- new Scala compiler
* Copyright 2005-2010 LAMP/EPFL
* Author: Paul Phillips
*/
package scala.tools.nsc
package matching
import symtab.Flags
import scala.reflect.NameTransformer.decode
import PartialFunction._
/** Patterns are wrappers for Trees with enhanced semantics.
*
* @author Paul Phillips
*/
trait Patterns extends ast.TreeDSL {
self: transform.ExplicitOuter =>
import global.{ typer => _, _ }
import definitions._
import CODE._
import Debug._
import treeInfo.{ unbind, isStar, isVarPattern, isVariableName }
type PatternMatch = MatchMatrix#PatternMatch
private type PatternVar = MatrixContext#PatternVar
// Fresh patterns
def emptyPatterns(i: Int): List[Pattern] = List.fill(i)(NoPattern)
def emptyTrees(i: Int): List[Tree] = List.fill(i)(EmptyTree)
// An empty pattern
def NoPattern = WildcardPattern()
// The constant null pattern
def NullPattern = LiteralPattern(NULL)
// The Nil pattern
def NilPattern = Pattern(gen.mkNil)
// 8.1.1
case class VariablePattern(tree: Ident) extends NamePattern {
val Ident(name) = tree
require(isVarPattern(tree) && name != nme.WILDCARD)
override def irrefutableFor(tpe: Type) = true
override def description = "%s".format(name)
}
// 8.1.1 (b)
case class WildcardPattern() extends Pattern {
val tree = EmptyTree
override def irrefutableFor(tpe: Type) = true
override def isDefault = true
override def description = "_"
}
// 8.1.2
case class TypedPattern(tree: Typed) extends Pattern {
private val Typed(expr, tpt) = tree
override def subpatternsForVars: List[Pattern] = List(Pattern(expr))
override def irrefutableFor(tpe: Type) = tpe <:< tree.tpe
override def simplify(pv: PatternVar) = Pattern(expr) match {
case ExtractorPattern(ua) if pv.sym.tpe <:< tpt.tpe => this rebindTo expr
case _ => this
}
override def description = "Typ(%s: %s)".format(Pattern(expr), tpt)
}
// 8.1.3
case class LiteralPattern(tree: Literal) extends Pattern {
val Literal(const @ Constant(value)) = tree
def isSwitchable = cond(const.tag) { case ByteTag | ShortTag | IntTag | CharTag => true }
def intValue = const.intValue
override def description = {
val s = if (value == null) "null" else value.toString()
"Lit(%s)".format(s)
}
}
// 8.1.4 (a)
case class ApplyIdentPattern(tree: Apply) extends ApplyPattern with NamePattern {
// XXX - see bug 3411 for code which violates this assumption
// require (!isVarPattern(fn) && args.isEmpty)
val ident @ Ident(name) = fn
override def sufficientType = Pattern(ident).equalsCheck
override def simplify(pv: PatternVar) = this.rebindToObjectCheck()
override def description = "Id(%s)".format(name)
}
// 8.1.4 (b)
case class ApplySelectPattern(tree: Apply) extends ApplyPattern with SelectPattern {
require (args.isEmpty)
val Apply(select: Select, _) = tree
override def sufficientType = mkSingletonFromQualifier
override def simplify(pv: PatternVar) = this.rebindToObjectCheck()
override def description = backticked match {
case Some(s) => "this." + s
case _ => "Sel(%s.%s)".format(Pattern(qualifier), name)
}
}
// 8.1.4 (c)
case class StableIdPattern(tree: Select) extends SelectPattern {
def select = tree
override def description = "St(%s)".format(printableSegments.mkString(" . "))
private def printableSegments =
pathSegments filter (x => !x.isEmpty && (x.toString != "$iw"))
}
// 8.1.4 (d)
case class ObjectPattern(tree: Apply) extends ApplyPattern { // NamePattern?
require(!fn.isType && isModule)
override def sufficientType = tpe.narrow
override def simplify(pv: PatternVar) = this.rebindToObjectCheck()
override def description = "Obj(%s)".format(fn)
}
// 8.1.4 (e)
case class SimpleIdPattern(tree: Ident) extends NamePattern {
val Ident(name) = tree
override def description = "Id(%s)".format(name)
}
// 8.1.5
case class ConstructorPattern(tree: Apply) extends ApplyPattern with NamePattern {
require(fn.isType && this.isCaseClass)
def name = tpe.typeSymbol.name
def cleanName = tpe.typeSymbol.decodedName
def hasPrefix = tpe.prefix.prefixString != ""
def prefixedName =
if (hasPrefix) "%s.%s".format(tpe.prefix.prefixString, cleanName)
else cleanName
private def isColonColon = cleanName == "::"
override def subpatterns(pm: MatchMatrix#PatternMatch) =
if (pm.head.isCaseClass) toPats(args)
else super.subpatterns(pm)
override def simplify(pv: PatternVar) =
if (args.isEmpty) this rebindToEmpty tree.tpe
else this
override def description = {
if (isColonColon) "%s :: %s".format(Pattern(args(0)), Pattern(args(1)))
else "%s(%s)".format(name, toPats(args).mkString(", "))
}
// XXX todo
// override def irrefutableFor(tpe: Type) = false
}
// 8.1.6
case class TuplePattern(tree: Apply) extends ApplyPattern {
// XXX todo
// override def irrefutableFor(tpe: Type) = false
override def description = "((%s))".format(args.size, toPats(args).mkString(", "))
}
// 8.1.7
case class ExtractorPattern(tree: UnApply) extends UnapplyPattern {
private val Apply(fn, _) = unfn
private val MethodType(List(arg, _*), _) = fn.tpe
private def uaTyped = Typed(tree, TypeTree(arg.tpe)) setType arg.tpe
override def necessaryType = arg.tpe
override def simplify(pv: PatternVar) =
if (pv.sym.tpe <:< arg.tpe) this
else this rebindTo uaTyped
override def description = "UnApp(%s => %s)".format(necessaryType, resTypesString)
}
// 8.1.8 (unapplySeq calls)
case class SequenceExtractorPattern(tree: UnApply) extends UnapplyPattern with SequenceLikePattern {
lazy val UnApply(
Apply(TypeApply(Select(_, nme.unapplySeq), List(tptArg)), _),
List(ArrayValue(_, elems))
) = tree
/** For folding a list into a well-typed x :: y :: etc :: tree. */
private def listFolder = {
val tpe = tptArg.tpe
val MethodType(_, TypeRef(pre, sym, _)) = ConsClass.primaryConstructor.tpe
val consRef = typeRef(pre, sym, List(tpe))
val listRef = typeRef(pre, ListClass, List(tpe))
def fold(x: Tree, xs: Tree) = unbind(x) match {
case _: Star => Pattern(x) rebindTo WILD(x.tpe) boundTree // this is using boundVariables instead of deepBoundVariables
case _ =>
val dummyMethod = new TermSymbol(NoSymbol, NoPosition, "matching$dummy")
val consType = MethodType(dummyMethod newSyntheticValueParams List(tpe, listRef), consRef)
Apply(TypeTree(consType), List(x, xs)) setType consRef
}
fold _
}
// @pre: is not right-ignoring (no star pattern) ; no exhaustivity check
override def simplify(pv: PatternVar) = {
pv.sym setFlag Flags.TRANS_FLAG
this rebindTo elems.foldRight(gen.mkNil)(listFolder)
}
override def description = "UnSeq(%s => %s)".format(tptArg, resTypesString)
}
trait SequenceLikePattern extends Pattern {
def elems: List[Tree]
def elemPatterns = toPats(elems)
def nonStarPatterns: List[Pattern] = if (hasStar) elemPatterns.init else elemPatterns
def nonStarLength = nonStarPatterns.length
def isAllDefaults = nonStarPatterns forall (_.isDefault)
def isShorter(other: SequenceLikePattern) = nonStarLength < other.nonStarLength
def isSameLength(other: SequenceLikePattern) = nonStarLength == other.nonStarLength
}
// 8.1.8 (b) (literal ArrayValues)
case class SequencePattern(tree: ArrayValue) extends Pattern with SequenceLikePattern {
lazy val ArrayValue(elemtpt, elems) = tree
override def subpatternsForVars: List[Pattern] = elemPatterns
override def description = "Seq(%s)".format(elemPatterns mkString ", ")
}
// 8.1.8 (c)
case class StarPattern(tree: Star) extends Pattern {
val Star(elem) = tree
override def description = "_*"
}
// XXX temporary?
case class ThisPattern(tree: This) extends NamePattern {
val This(name) = tree
override def description = "this"
}
// 8.1.9
// InfixPattern ... subsumed by Constructor/Extractor Patterns
// 8.1.10
case class AlternativePattern(tree: Alternative) extends Pattern {
private lazy val Alternative(subtrees) = tree
private def alts = toPats(subtrees)
override def description = "Alt(%s)".format(alts mkString " | ")
}
// 8.1.11
// XMLPattern ... for now, subsumed by SequencePattern, but if we want
// to make it work right, it probably needs special handling.
private def abortUnknownTree(tree: Tree) =
abort("Unknown Tree reached pattern matcher: %s/%s".format(tree, tree.getClass))
object Pattern {
// a small tree -> pattern cache
private val cache = new collection.mutable.HashMap[Tree, Pattern]
def unadorn(x: Tree): Tree = x match {
case Typed(expr, _) => unadorn(expr)
case Bind(_, x) => unadorn(x)
case _ => x
}
def isRightIgnoring(t: Tree) = cond(unadorn(t)) {
case ArrayValue(_, xs) if !xs.isEmpty => isStar(unadorn(xs.last))
}
def apply(tree: Tree): Pattern = {
if (cache contains tree)
return cache(tree)
val p = tree match {
case x: Bind => apply(unbind(tree)) withBoundTree x
case EmptyTree => WildcardPattern()
case Ident(nme.WILDCARD) => WildcardPattern()
case x @ Alternative(ps) => AlternativePattern(x)
case x: Apply => ApplyPattern(x)
case x: Typed => TypedPattern(x)
case x: Literal => LiteralPattern(x)
case x: UnApply => UnapplyPattern(x)
case x: Ident => if (isVarPattern(x)) VariablePattern(x) else SimpleIdPattern(x)
case x: ArrayValue => SequencePattern(x)
case x: Select => StableIdPattern(x)
case x: Star => StarPattern(x)
case x: This => ThisPattern(x) // XXX ?
case _ => abortUnknownTree(tree)
}
cache(tree) = p
// limiting the trace output
p match {
case WildcardPattern() => p
case _: LiteralPattern => p
case _ => tracing("Pattern", p)
}
}
def unapply(other: Any): Option[(Tree, List[Symbol])] = other match {
case x: Tree => unapply(Pattern(x))
case x: Pattern => Some((x.tree, x.boundVariables))
case _ => None
}
}
object UnapplyPattern {
private object UnapplySeq {
private object TypeApp {
def unapply(x: Any) = condOpt(x) {
case TypeApply(sel @ Select(stor, nme.unapplySeq), List(tpe)) if stor.symbol eq ListModule => tpe
}
}
def unapply(x: UnApply) = condOpt(x) {
case UnApply(Apply(TypeApp(tptArg), _), List(ArrayValue(_, xs))) => (tptArg, xs)
}
}
def apply(x: UnApply): Pattern = {
x match {
case UnapplySeq(_, _) => SequenceExtractorPattern(x)
case _ => ExtractorPattern(x)
}
}
}
// right now a tree like x @ Apply(fn, Nil) where !fn.isType
// is handled by creating a singleton type:
//
// val stype = Types.singleType(x.tpe.prefix, x.symbol)
//
// and then passing that as a type argument to EqualsPatternClass:
//
// val tpe = typeRef(NoPrefix, EqualsPatternClass, List(stype))
//
// then creating a Typed pattern and rebinding.
//
// val newpat = Typed(EmptyTree, TypeTree(tpe)) setType tpe)
//
// This is also how Select(qual, name) is handled.
object ApplyPattern {
def apply(x: Apply): Pattern = {
val Apply(fn, args) = x
def isModule = x.symbol.isModule || x.tpe.termSymbol.isModule
def isTuple = isTupleTypeOrSubtype(fn.tpe)
if (fn.isType) {
if (isTuple) TuplePattern(x)
else ConstructorPattern(x)
}
else if (args.isEmpty) {
if (isModule) ObjectPattern(x)
else fn match {
case _: Ident => ApplyIdentPattern(x)
case _: Select => ApplySelectPattern(x)
}
}
else abortUnknownTree(x)
}
}
/** Some intermediate pattern classes with shared structure **/
sealed trait SelectPattern extends NamePattern {
def select: Select
lazy val Select(qualifier, name) = select
def pathSegments = getPathSegments(tree)
def backticked: Option[String] = qualifier match {
case _: This if isVariableName(name) => Some("`%s`".format(name))
case _ => None
}
protected def getPathSegments(t: Tree): List[Name] = t match {
case Select(q, name) => name :: getPathSegments(q)
case Apply(f, Nil) => getPathSegments(f)
case _ => Nil
}
protected def mkSingletonFromQualifier = {
def pType = qualifier match {
case _: Apply => PseudoType(tree)
case _ => singleType(Pattern(qualifier).necessaryType, sym)
}
qualifier.tpe match {
case t: ThisType => singleType(t, sym) // this.X
case _ => pType
}
}
}
sealed trait NamePattern extends Pattern {
def name: Name
override def sufficientType = tpe.narrow
override def simplify(pv: PatternVar) = this.rebindToEqualsCheck()
override def description = name.toString()
}
sealed trait UnapplyPattern extends Pattern {
lazy val UnApply(unfn, args) = tree
override def subpatternsForVars: List[Pattern] = toPats(args)
def resTypes = analyzer.unapplyTypeList(unfn.symbol, unfn.tpe)
def resTypesString = resTypes match {
case Nil => "Boolean"
case xs => xs.mkString(", ")
}
private def isSameFunction(f1: Tree, f2: Tree) =
(f1.symbol == f2.symbol) && (f1 equalsStructure f2)
// XXX args
def isSameUnapply(other: UnapplyPattern) =
isSameFunction(unfn, other.unfn)
}
sealed trait ApplyPattern extends Pattern {
protected lazy val Apply(fn, args) = tree
override def subpatternsForVars: List[Pattern] = toPats(args)
override def dummies =
if (!this.isCaseClass) Nil
else emptyPatterns(sufficientType.typeSymbol.caseFieldAccessors.size)
def isConstructorPattern = fn.isType
}
sealed abstract class Pattern extends PatternBindingLogic {
val tree: Tree
// returns either a simplification of this pattern or identity.
def simplify(pv: PatternVar): Pattern = this
def simplify(): Pattern = this simplify null
// the right number of dummies for this pattern
def dummies: List[Pattern] = Nil
// 8.1.13
// A pattern p is irrefutable for type T if any of the following applies:
// 1) p is a variable pattern
// 2) p is a typed pattern x: T', and T <: T'
// 3) p is a constructor pattern C(p1,...,pn), the type T is an instance of class C,
// the primary constructor of type T has argument types T1,...,Tn and and each
// pi is irrefutable for Ti.
def irrefutableFor(tpe: Type) = false
// does this pattern completely cover that pattern (i.e. latter cannot be matched)
def completelyCovers(second: Pattern) = false
// Is this a default pattern (untyped "_" or an EmptyTree inserted by the matcher)
def isDefault = false
// what type must a scrutinee have to have any chance of matching this pattern?
def necessaryType = tpe
// what type could a scrutinee have which would automatically indicate a match?
// (nullness and guards will still be checked.)
def sufficientType = tpe
// XXX have to determine if this can be made useful beyond an extractor barrier.
// Default sufficient type might be NothingClass.tpe, tpe.narrow, ...
// the subpatterns for this pattern (at the moment, that means constructor arguments)
def subpatterns(pm: MatchMatrix#PatternMatch): List[Pattern] = pm.dummies
def sym = tree.symbol
def tpe = tree.tpe
def prefix = tpe.prefix
def isEmpty = tree.isEmpty
def isSymValid = (sym != null) && (sym != NoSymbol)
def isModule = sym.isModule || tpe.termSymbol.isModule
def isCaseClass = tpe.typeSymbol hasFlag Flags.CASE
def isObject = isSymValid && prefix.isStable // XXX not entire logic
def unadorn(t: Tree): Tree = Pattern unadorn t
private def isStar(x: Tree) = cond(unadorn(x)) { case Star(_) => true }
private def endsStar(xs: List[Tree]) = xs.nonEmpty && isStar(xs.last)
def isStarSequence = isSequence && hasStar
def isSequence = cond(unadorn(tree)) {
case ArrayValue(_, _) => true
}
def hasStar = cond(unadorn(tree)) {
case ArrayValue(_, xs) if endsStar(xs) => true
}
def setType(tpe: Type): this.type = {
tree setType tpe
this
}
def equalsCheck =
tracing("equalsCheck",
if (sym.isValue) singleType(NoPrefix, sym)
else tpe.narrow
)
/** Standard methods **/
override def equals(other: Any) = other match {
case x: Pattern => this.boundTree == x.boundTree
case _ => super.equals(other)
}
override def hashCode() = boundTree.hashCode()
def description = super.toString()
def bindingsDescription =
if (boundTree.isEmpty) ""
else (boundVariables map (_.name)).mkString("", ", ", " @ ")
final override def toString() = {
if (boundVariables.isEmpty) description
else "%s%s".format(bindingsDescription, description)
}
def toTypeString() = "%s <: x <: %s".format(necessaryType, sufficientType)
}
/*** Extractors ***/
object UnapplyParamType {
def unapply(x: Tree): Option[Type] = condOpt(unbind(x)) {
case UnApply(Apply(fn, _), _) => fn.tpe match {
case m: MethodType => m.paramTypes.head
}
}
}
}
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