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/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Paul Phillips
*/
package scala
package tools
package nsc
package transform
package patmat
/** This is scalac-specific logic layered on top of the scalac-agnostic
* "matching products to patterns" logic defined in PatternExpander.
*/
trait ScalacPatternExpanders {
val global: Global
import global._
import definitions._
import treeInfo._
import analyzer._
type PatternAligned = ScalacPatternExpander#Aligned
implicit class AlignedOps(val aligned: PatternAligned) {
import aligned._
def expectedTypes = typedPatterns map (_.tpe)
def unexpandedFormals = extractor.varargsTypes
}
trait ScalacPatternExpander extends PatternExpander[Tree, Type] {
def NoPattern = EmptyTree
def NoType = global.NoType
def newPatterns(patterns: List[Tree]): Patterns = patterns match {
case init :+ last if isStar(last) => Patterns(init, last)
case _ => Patterns(patterns, NoPattern)
}
def elementTypeOf(tpe: Type) = {
val seq = repeatedToSeq(tpe)
( typeOfMemberNamedHead(seq)
orElse typeOfMemberNamedApply(seq)
orElse definitions.elementType(ArrayClass, seq)
)
}
def newExtractor(whole: Type, fixed: List[Type], repeated: Repeated, typeOfSinglePattern: Type): Extractor =
logResult(s"newExtractor($whole, $fixed, $repeated, $typeOfSinglePattern")(Extractor(whole, fixed, repeated, typeOfSinglePattern))
def newExtractor(whole: Type, fixed: List[Type], repeated: Repeated): Extractor = newExtractor(whole, fixed, repeated, tupleType(fixed))
// Turn Seq[A] into Repeated(Seq[A], A, A*)
def repeatedFromSeq(seqType: Type): Repeated = {
val elem = elementTypeOf(seqType)
val repeated = scalaRepeatedType(elem)
Repeated(seqType, elem, repeated)
}
// Turn A* into Repeated(Seq[A], A, A*)
def repeatedFromVarargs(repeated: Type): Repeated =
Repeated(repeatedToSeq(repeated), repeatedToSingle(repeated), repeated)
/** In this case we are basing the pattern expansion on a case class constructor.
* The argument is the MethodType carried by the primary constructor.
*/
def applyMethodTypes(method: Type): Extractor = {
val whole = method.finalResultType
method.paramTypes match {
case init :+ last if isScalaRepeatedParamType(last) => newExtractor(whole, init, repeatedFromVarargs(last))
case tps => newExtractor(whole, tps, NoRepeated)
}
}
/** In this case, expansion is based on an unapply or unapplySeq method.
* Unfortunately the MethodType does not carry the information of whether
* it was unapplySeq, so we have to funnel that information in separately.
*/
def unapplyMethodTypes(context: Context, whole: Type, result: Type, isSeq: Boolean): Extractor = {
if (result =:= BooleanTpe) newExtractor(whole, Nil, NoRepeated)
else {
val getResult = typeOfMemberNamedGet(result)
def noGetError() = {
val name = "unapply" + (if (isSeq) "Seq" else "")
context.error(context.tree.pos, s"The result type of an $name method must contain a member `get` to be used as an extractor pattern, no such member exists in ${result}")
}
val expanded = getResult match {
case global.NoType => noGetError(); Nil
case rawGet if !hasSelectors(rawGet) => rawGet :: Nil
case rawGet => typesOfSelectors(rawGet)
}
expanded match {
case init :+ last if isSeq => newExtractor(whole, init, repeatedFromSeq(last), getResult)
case tps => newExtractor(whole, tps, NoRepeated, getResult)
}
}
}
}
object alignPatterns extends ScalacPatternExpander {
private def validateAligned(context: Context, tree: Tree, aligned: Aligned): Aligned = {
import aligned._
def owner = tree.symbol.owner
def offering = extractor.offeringString
def symString = tree.symbol.fullLocationString
def offerString = if (extractor.isErroneous) "" else s" offering $offering"
def arityExpected = ( if (extractor.hasSeq) "at least " else "" ) + productArity
def err(msg: String) = context.error(tree.pos, msg)
def warn(msg: String) = context.warning(tree.pos, msg)
def arityError(what: String) = err(s"$what patterns for $owner$offerString: expected $arityExpected, found $totalArity")
if (isStar && !isSeq)
err("Star pattern must correspond with varargs or unapplySeq")
else if (elementArity < 0)
arityError("not enough")
else if (elementArity > 0 && !isSeq)
arityError("too many")
else if (settings.warnStarsAlign && isSeq && productArity > 0 && elementArity > 0) warn {
if (isStar) "Sequence wildcard (_*) does not align with repeated case parameter or extracted sequence; the result may be unexpected."
else "A repeated case parameter or extracted sequence is not matched by a sequence wildcard (_*), and may fail at runtime."
}
aligned
}
def apply(context: Context, sel: Tree, args: List[Tree]): Aligned = {
val fn = sel match {
case Unapplied(fn) => fn
case _ => sel
}
val patterns = newPatterns(args)
val isUnapply = sel.symbol.name == nme.unapply
val extractor = sel.symbol.name match {
case nme.unapply => unapplyMethodTypes(context, firstParamType(fn.tpe), sel.tpe, isSeq = false)
case nme.unapplySeq => unapplyMethodTypes(context, firstParamType(fn.tpe), sel.tpe, isSeq = true)
case _ => applyMethodTypes(fn.tpe)
}
/** Rather than let the error that is SI-6675 pollute the entire matching
* process, we will tuple the extractor before creation Aligned so that
* it contains known good values.
*/
def productArity = extractor.productArity
def acceptMessage = if (extractor.isErroneous) "" else s" to hold ${extractor.offeringString}"
val requiresTupling = isUnapply && patterns.totalArity == 1 && productArity > 1
val normalizedExtractor = if (requiresTupling) {
val tupled = extractor.asSinglePattern
if (effectivePatternArity(args) == 1 && isTupleType(extractor.typeOfSinglePattern)) {
val sym = sel.symbol.owner
currentRun.reporting.deprecationWarning(sel.pos, sym, s"${sym} expects $productArity patterns$acceptMessage but crushing into $productArity-tuple to fit single pattern (SI-6675)")
}
tupled
} else extractor
validateAligned(context, fn, Aligned(patterns, normalizedExtractor))
}
def apply(context: Context, tree: Tree): Aligned = tree match {
case Apply(fn, args) => apply(context, fn, args)
case UnApply(fn, args) => apply(context, fn, args)
}
}
}
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