diff options
Diffstat (limited to 'src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala')
| -rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala | 186 |
1 files changed, 145 insertions, 41 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala index b0745b4c09..4b53802d95 100644 --- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala +++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala @@ -409,15 +409,9 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // example check: List[Int] <:< ::[Int] // TODO: extractor.paramType may contain unbound type params (run/t2800, run/t3530) - val (typeTestTreeMaker, patBinderOrCasted) = - if (needsTypeTest(patBinder.info.widen, extractor.paramType)) { - // chain a type-testing extractor before the actual extractor call - // it tests the type, checks the outer pointer and casts to the expected type - // TODO: the outer check is mandated by the spec for case classes, but we do it for user-defined unapplies as well [SPEC] - // (the prefix of the argument passed to the unapply must equal the prefix of the type of the binder) - val treeMaker = TypeTestTreeMaker(patBinder, patBinder, extractor.paramType, extractor.paramType)(pos, extractorArgTypeTest = true) - (List(treeMaker), treeMaker.nextBinder) - } else { + // `patBinderOrCasted` is assigned the result of casting `patBinder` to `extractor.paramType` + val (typeTestTreeMaker, patBinderOrCasted, binderKnownNonNull) = + if (patBinder.info.widen <:< extractor.paramType) { // no type test needed, but the tree maker relies on `patBinderOrCasted` having type `extractor.paramType` (and not just some type compatible with it) // SI-6624 shows this is necessary because apparently patBinder may have an unfortunate type (.decls don't have the case field accessors) // TODO: get to the bottom of this -- I assume it happens when type checking infers a weird type for an unapply call @@ -426,10 +420,21 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL if (settings.developer.value && !(patBinder.info =:= extractor.paramType)) devWarning(s"resetting info of $patBinder: ${patBinder.info} to ${extractor.paramType}") */ - (Nil, patBinder setInfo extractor.paramType) + (Nil, patBinder setInfo extractor.paramType, false) + } else { + // chain a type-testing extractor before the actual extractor call + // it tests the type, checks the outer pointer and casts to the expected type + // TODO: the outer check is mandated by the spec for case classes, but we do it for user-defined unapplies as well [SPEC] + // (the prefix of the argument passed to the unapply must equal the prefix of the type of the binder) + val treeMaker = TypeTestTreeMaker(patBinder, patBinder, extractor.paramType, extractor.paramType)(pos, extractorArgTypeTest = true) + + // check whether typetest implies patBinder is not null, + // even though the eventual null check will be on patBinderOrCasted + // it'll be equal to patBinder casted to extractor.paramType anyway (and the type test is on patBinder) + (List(treeMaker), treeMaker.nextBinder, treeMaker.impliesBinderNonNull(patBinder)) } - withSubPats(typeTestTreeMaker :+ extractor.treeMaker(patBinderOrCasted, pos), extractor.subBindersAndPatterns: _*) + withSubPats(typeTestTreeMaker :+ extractor.treeMaker(patBinderOrCasted, binderKnownNonNull, pos), extractor.subBindersAndPatterns: _*) } @@ -622,8 +627,13 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // to which type should the previous binder be casted? def paramType : Type - // binder has been casted to paramType if necessary - def treeMaker(binder: Symbol, pos: Position): TreeMaker + /** Create the TreeMaker that embodies this extractor call + * + * `binder` has been casted to `paramType` if necessary + * `binderKnownNonNull` indicates whether the cast implies `binder` cannot be null + * when `binderKnownNonNull` is `true`, `ProductExtractorTreeMaker` does not do a (redundant) null check on binder + */ + def treeMaker(binder: Symbol, binderKnownNonNull: Boolean, pos: Position): TreeMaker // `subPatBinders` are the variables bound by this pattern in the following patterns // subPatBinders are replaced by references to the relevant part of the extractor's result (tuple component, seq element, the result as-is) @@ -637,6 +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 @@ -731,17 +746,25 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL def isSeq: Boolean = rawSubPatTypes.nonEmpty && isRepeatedParamType(rawSubPatTypes.last) protected def rawSubPatTypes = constructorTp.paramTypes - // binder has type paramType - def treeMaker(binder: Symbol, pos: Position): TreeMaker = { + /** Create the TreeMaker that embodies this extractor call + * + * `binder` has been casted to `paramType` if necessary + * `binderKnownNonNull` indicates whether the cast implies `binder` cannot be null + * when `binderKnownNonNull` is `true`, `ProductExtractorTreeMaker` does not do a (redundant) null check on binder + */ + 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) + 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 @@ -763,11 +786,21 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL def resultType = tpe.finalResultType def isSeq = extractorCall.symbol.name == nme.unapplySeq - def treeMaker(patBinderOrCasted: Symbol, pos: Position): TreeMaker = { + /** Create the TreeMaker that embodies this extractor call + * + * `binder` has been casted to `paramType` if necessary + * `binderKnownNonNull` is not used in this subclass + * + * TODO: implement review feedback by @retronym: + * Passing the pair of values around suggests: + * case class Binder(sym: Symbol, knownNotNull: Boolean). + * Perhaps it hasn't reached critical mass, but it would already clean things up a touch. + */ + def treeMaker(patBinderOrCasted: Symbol, binderKnownNonNull: Boolean, pos: Position): TreeMaker = { // 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 = @@ -824,6 +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 @@ -991,10 +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 @@ -1015,10 +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) + } } } @@ -1038,7 +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 { @@ -1081,27 +1147,35 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL case class ProductExtractorTreeMaker(prevBinder: Symbol, extraCond: Option[Tree])( val subPatBinders: List[Symbol], val subPatRefs: List[Tree], - val mutableBinders: List[Symbol]) extends FunTreeMaker with PreserveSubPatBinders { + val mutableBinders: List[Symbol], + 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 - val cond = extraCond map (nullCheck AND _) getOrElse nullCheck - casegen.ifThenElseZero(cond, bindSubPats(substitution(next))) + val cond = + if (binderKnownNonNull) extraCond + else (extraCond map (nullCheck AND _) + orElse Some(nullCheck)) + + cond match { + case Some(cond) => + casegen.ifThenElseZero(cond, bindSubPats(substitution(next))) + case _ => + bindSubPats(substitution(next)) + } } override def toString = "P"+(prevBinder.name, extraCond getOrElse "", localSubstitution) } - // typetag-based tests are inserted by the type checker - def needsTypeTest(tp: Type, pt: Type): Boolean = !(tp <:< pt) - object TypeTestTreeMaker { // factored out so that we can consistently generate other representations of the tree that implements the test // (e.g. propositions for exhaustivity and friends, boolean for isPureTypeTest) @@ -1115,12 +1189,14 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL def equalsTest(pat: Tree, testedBinder: Symbol): Result def eqTest(pat: Tree, testedBinder: Symbol): Result def and(a: Result, b: Result): Result + def tru: Result } object treeCondStrategy extends TypeTestCondStrategy { import CODE._ type Result = Tree def and(a: Result, b: Result): Result = a AND b + def tru = TRUE_typed def typeTest(testedBinder: Symbol, expectedTp: Type) = codegen._isInstanceOf(testedBinder, expectedTp) def nonNullTest(testedBinder: Symbol) = REF(testedBinder) OBJ_NE NULL def equalsTest(pat: Tree, testedBinder: Symbol) = codegen._equals(pat, testedBinder) @@ -1151,6 +1227,19 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL def equalsTest(pat: Tree, testedBinder: Symbol): Result = false def eqTest(pat: Tree, testedBinder: Symbol): Result = false def and(a: Result, b: Result): Result = false // we don't and type tests, so the conjunction must include at least one false + def tru = true + } + + def nonNullImpliedByTestChecker(binder: Symbol) = new TypeTestCondStrategy { + type Result = Boolean + + def typeTest(testedBinder: Symbol, expectedTp: Type): Result = testedBinder eq binder + def outerTest(testedBinder: Symbol, expectedTp: Type): Result = false + def nonNullTest(testedBinder: Symbol): Result = testedBinder eq binder + def equalsTest(pat: Tree, testedBinder: Symbol): Result = false // could in principle analyse pat and see if it's statically known to be non-null + def eqTest(pat: Tree, testedBinder: Symbol): Result = false // could in principle analyse pat and see if it's statically known to be non-null + def and(a: Result, b: Result): Result = a || b + def tru = false } } @@ -1220,10 +1309,16 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // I think it's okay: // - the isInstanceOf test includes a test for the element type // - Scala's arrays are invariant (so we don't drop type tests unsoundly) - case _ if (expectedTp <:< AnyRefClass.tpe) && !needsTypeTest(testedBinder.info.widen, expectedTp) => - // do non-null check first to ensure we won't select outer on null - if (outerTestNeeded) and(nonNullTest(testedBinder), outerTest(testedBinder, expectedTp)) - else nonNullTest(testedBinder) + case _ if testedBinder.info.widen <:< expectedTp => + // if the expected type is a primitive value type, it cannot be null and it cannot have an outer pointer + // since the types conform, no further checking is required + if (expectedTp.typeSymbol.isPrimitiveValueClass) tru + // have to test outer and non-null only when it's a reference type + else if (expectedTp <:< AnyRefClass.tpe) { + // do non-null check first to ensure we won't select outer on null + if (outerTestNeeded) and(nonNullTest(testedBinder), outerTest(testedBinder, expectedTp)) + else nonNullTest(testedBinder) + } else default case _ => default } @@ -1235,6 +1330,8 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // is this purely a type test, e.g. no outer check, no equality tests (used in switch emission) def isPureTypeTest = renderCondition(pureTypeTestChecker) + def impliesBinderNonNull(binder: Symbol) = renderCondition(nonNullImpliedByTestChecker(binder)) + override def toString = "TT"+(expectedTp, testedBinder.name, nextBinderTp) } @@ -1733,6 +1830,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL def nonNullTest(testedBinder: Symbol) = NonNullCond(binderToUniqueTree(testedBinder)) def equalsTest(pat: Tree, testedBinder: Symbol) = EqualityCond(binderToUniqueTree(testedBinder), unique(pat)) def eqTest(pat: Tree, testedBinder: Symbol) = EqualityCond(binderToUniqueTree(testedBinder), unique(pat)) // TODO: eq, not == + def tru = TrueCond } ttm.renderCondition(condStrategy) case EqualityTestTreeMaker(prevBinder, patTree, _) => EqualityCond(binderToUniqueTree(prevBinder), unique(patTree)) @@ -3694,11 +3792,17 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // nextBinder: T // next == MatchMonad[U] // returns MatchMonad[U] - def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree = - ifThenElseZero(cond, BLOCK( - VAL(nextBinder) === res, - next - )) + def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree = { + val rest = + // only emit a local val for `nextBinder` if it's actually referenced in `next` + if (next.exists(_.symbol eq nextBinder)) + BLOCK( + VAL(nextBinder) === res, + next + ) + else next + ifThenElseZero(cond, rest) + } // guardTree: Boolean // next: MatchMonad[T] |