From 494ba94518c9b40b7bf600ec7b70561842375597 Mon Sep 17 00:00:00 2001 From: Adriaan Moors Date: Tue, 29 Jan 2013 00:13:14 -0800 Subject: don't store subpats bound to underscore also, tweak fix in place for SI-5158 to appease SI-6941 don't store mutable fields from scala.* as we can assume these classes are well-behaved and do not mutate their case class fields --- .../tools/nsc/typechecker/PatternMatching.scala | 64 ++++++++++++++++++---- 1 file changed, 53 insertions(+), 11 deletions(-) (limited to 'src') diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala index f32ca4bd8e..8ae2e0a3b8 100644 --- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala +++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala @@ -647,6 +647,11 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL case bp => bp } + // never store these in local variables (for PreserveSubPatBinders) + lazy val ignoredSubPatBinders = (subPatBinders zip args).collect{ + case (b, PatternBoundToUnderscore()) => b + }.toSet + def subPatTypes: List[Type] = if(isSeq) { val TypeRef(pre, SeqClass, args) = seqTp @@ -750,13 +755,16 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL def treeMaker(binder: Symbol, binderKnownNonNull: Boolean, pos: Position): TreeMaker = { val paramAccessors = binder.constrParamAccessors // binders corresponding to mutable fields should be stored (SI-5158, SI-6070) + // make an exception for classes under the scala package as they should be well-behaved, + // to optimize matching on List val mutableBinders = - if (paramAccessors exists (_.isMutable)) + if (!binder.info.typeSymbol.hasTransOwner(ScalaPackageClass) && + (paramAccessors exists (_.isMutable))) subPatBinders.zipWithIndex.collect{ case (binder, idx) if paramAccessors(idx).isMutable => binder } else Nil // checks binder ne null before chaining to the next extractor - ProductExtractorTreeMaker(binder, lengthGuard(binder))(subPatBinders, subPatRefs(binder), mutableBinders, binderKnownNonNull) + ProductExtractorTreeMaker(binder, lengthGuard(binder))(subPatBinders, subPatRefs(binder), mutableBinders, binderKnownNonNull, ignoredSubPatBinders) } // reference the (i-1)th case accessor if it exists, otherwise the (i-1)th tuple component @@ -792,7 +800,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // the extractor call (applied to the binder bound by the flatMap corresponding to the previous (i.e., enclosing/outer) pattern) val extractorApply = atPos(pos)(spliceApply(patBinderOrCasted)) val binder = freshSym(pos, pureType(resultInMonad)) // can't simplify this when subPatBinders.isEmpty, since UnitClass.tpe is definitely wrong when isSeq, and resultInMonad should always be correct since it comes directly from the extractor's result type - ExtractorTreeMaker(extractorApply, lengthGuard(binder), binder)(subPatBinders, subPatRefs(binder), resultType.typeSymbol == BooleanClass, checkedLength, patBinderOrCasted) + ExtractorTreeMaker(extractorApply, lengthGuard(binder), binder)(subPatBinders, subPatRefs(binder), resultType.typeSymbol == BooleanClass, checkedLength, patBinderOrCasted, ignoredSubPatBinders) } override protected def seqTree(binder: Symbol): Tree = @@ -849,6 +857,16 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL } } + object PatternBoundToUnderscore { + def unapply(pat: Tree): Boolean = pat match { + case Bind(nme.WILDCARD, _) => true // don't skip when binding an interesting symbol! + case Ident(nme.WILDCARD) => true + case Alternative(ps) => ps forall (PatternBoundToUnderscore.unapply(_)) + case Typed(PatternBoundToUnderscore(), _) => true + case _ => false + } + } + object Bound { def unapply(t: Tree): Option[(Symbol, Tree)] = t match { case t@Bind(n, p) if (t.symbol ne null) && (t.symbol ne NoSymbol) => // pos/t2429 does not satisfy these conditions @@ -1016,10 +1034,17 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL trait PreserveSubPatBinders extends TreeMaker { val subPatBinders: List[Symbol] val subPatRefs: List[Tree] + val ignoredSubPatBinders: Set[Symbol] // unless `debugInfoEmitVars`, this set should contain the bare minimum for correctness // mutable case class fields need to be stored regardless (SI-5158, SI-6070) -- see override in ProductExtractorTreeMaker - def storedBinders: Set[Symbol] = if (debugInfoEmitVars) subPatBinders.toSet else Set.empty + // sub patterns bound to wildcard (_) are never stored as they can't be referenced + // dirty debuggers will have to get dirty to see the wildcards + lazy val storedBinders: Set[Symbol] = + (if (debugInfoEmitVars) subPatBinders.toSet else Set.empty) ++ extraStoredBinders -- ignoredSubPatBinders + + // e.g., mutable fields of a case class in ProductExtractorTreeMaker + def extraStoredBinders: Set[Symbol] def emitVars = storedBinders.nonEmpty @@ -1040,10 +1065,22 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL Substitution(subPatBinders, subPatRefs) >> super.subPatternsAsSubstitution import CODE._ - def bindSubPats(in: Tree): Tree = if (!emitVars) in + def bindSubPats(in: Tree): Tree = + if (!emitVars) in else { - val (subPatBindersStored, subPatRefsStored) = stored.unzip - Block(map2(subPatBindersStored.toList, subPatRefsStored.toList)(VAL(_) === _), in) + // binders in `subPatBindersStored` that are referenced by tree `in` + val usedBinders = new collection.mutable.HashSet[Symbol]() + // all potentially stored subpat binders + val potentiallyStoredBinders = stored.unzip._1.toSet + // compute intersection of all symbols in the tree `in` and all potentially stored subpat binders + in.foreach(t => if (potentiallyStoredBinders(t.symbol)) usedBinders += t.symbol) + + if (usedBinders.isEmpty) in + else { + // only store binders actually used + val (subPatBindersStored, subPatRefsStored) = stored.filter{case (b, _) => usedBinders(b)}.unzip + Block(map2(subPatBindersStored.toList, subPatRefsStored.toList)(VAL(_) === _), in) + } } } @@ -1063,7 +1100,11 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL val subPatRefs: List[Tree], extractorReturnsBoolean: Boolean, val checkedLength: Option[Int], - val prevBinder: Symbol) extends FunTreeMaker with PreserveSubPatBinders { + val prevBinder: Symbol, + val ignoredSubPatBinders: Set[Symbol] + ) extends FunTreeMaker with PreserveSubPatBinders { + + def extraStoredBinders: Set[Symbol] = Set() def chainBefore(next: Tree)(casegen: Casegen): Tree = { val condAndNext = extraCond match { @@ -1107,14 +1148,15 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL val subPatBinders: List[Symbol], val subPatRefs: List[Tree], val mutableBinders: List[Symbol], - binderKnownNonNull: Boolean) extends FunTreeMaker with PreserveSubPatBinders { + binderKnownNonNull: Boolean, + val ignoredSubPatBinders: Set[Symbol] + ) extends FunTreeMaker with PreserveSubPatBinders { import CODE._ val nextBinder = prevBinder // just passing through // mutable binders must be stored to avoid unsoundness or seeing mutation of fields after matching (SI-5158, SI-6070) - // (the implementation could be optimized by duplicating code from `super.storedBinders`, but this seems more elegant) - override def storedBinders: Set[Symbol] = super.storedBinders ++ mutableBinders.toSet + def extraStoredBinders: Set[Symbol] = mutableBinders.toSet def chainBefore(next: Tree)(casegen: Casegen): Tree = { val nullCheck = REF(prevBinder) OBJ_NE NULL -- cgit v1.2.3