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Diffstat (limited to 'src/dotty/tools/dotc/core/TypeComparer.scala')
| -rw-r--r-- | src/dotty/tools/dotc/core/TypeComparer.scala | 1502 |
1 files changed, 0 insertions, 1502 deletions
diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala deleted file mode 100644 index f78820fff..000000000 --- a/src/dotty/tools/dotc/core/TypeComparer.scala +++ /dev/null @@ -1,1502 +0,0 @@ -package dotty.tools -package dotc -package core - -import Types._, Contexts._, Symbols._, Flags._, Names._, NameOps._, Denotations._ -import Decorators._ -import StdNames.{nme, tpnme} -import collection.mutable -import util.{Stats, DotClass, SimpleMap} -import config.Config -import config.Printers.{typr, constr, subtyping, noPrinter} -import TypeErasure.{erasedLub, erasedGlb} -import TypeApplications._ -import scala.util.control.NonFatal - -/** Provides methods to compare types. - */ -class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling { - implicit val ctx: Context = initctx - - val state = ctx.typerState - import state.constraint - - private var pendingSubTypes: mutable.Set[(Type, Type)] = null - private var recCount = 0 - - private var needsGc = false - - /** Is a subtype check in progress? In that case we may not - * permanently instantiate type variables, because the corresponding - * constraint might still be retracted and the instantiation should - * then be reversed. - */ - def subtypeCheckInProgress: Boolean = { - val result = recCount > 0 - if (result) { - constr.println("*** needsGC ***") - needsGc = true - } - result - } - - /** For statistics: count how many isSubTypes are part of successful comparisons */ - private var successCount = 0 - private var totalCount = 0 - - private var myAnyClass: ClassSymbol = null - private var myNothingClass: ClassSymbol = null - private var myNullClass: ClassSymbol = null - private var myObjectClass: ClassSymbol = null - private var myAnyType: TypeRef = null - private var myNothingType: TypeRef = null - - def AnyClass = { - if (myAnyClass == null) myAnyClass = defn.AnyClass - myAnyClass - } - def NothingClass = { - if (myNothingClass == null) myNothingClass = defn.NothingClass - myNothingClass - } - def NullClass = { - if (myNullClass == null) myNullClass = defn.NullClass - myNullClass - } - def ObjectClass = { - if (myObjectClass == null) myObjectClass = defn.ObjectClass - myObjectClass - } - def AnyType = { - if (myAnyType == null) myAnyType = AnyClass.typeRef - myAnyType - } - def NothingType = { - if (myNothingType == null) myNothingType = NothingClass.typeRef - myNothingType - } - - /** Indicates whether a previous subtype check used GADT bounds */ - var GADTused = false - - /** Record that GADT bounds of `sym` were used in a subtype check. - * But exclude constructor type parameters, as these are aliased - * to the corresponding class parameters, which does not constitute - * a true usage of a GADT symbol. - */ - private def GADTusage(sym: Symbol) = { - if (!sym.owner.isConstructor) GADTused = true - true - } - - // Subtype testing `<:<` - - def topLevelSubType(tp1: Type, tp2: Type): Boolean = { - if (tp2 eq NoType) return false - if ((tp2 eq tp1) || (tp2 eq WildcardType)) return true - try isSubType(tp1, tp2) - finally - if (Config.checkConstraintsSatisfiable) - assert(isSatisfiable, constraint.show) - } - - protected def isSubType(tp1: Type, tp2: Type): Boolean = ctx.traceIndented(s"isSubType ${traceInfo(tp1, tp2)}", subtyping) { - if (tp2 eq NoType) false - else if (tp1 eq tp2) true - else { - val saved = constraint - val savedSuccessCount = successCount - try { - recCount = recCount + 1 - val result = - if (recCount < Config.LogPendingSubTypesThreshold) firstTry(tp1, tp2) - else monitoredIsSubType(tp1, tp2) - recCount = recCount - 1 - if (!result) constraint = saved - else if (recCount == 0 && needsGc) { - state.gc() - needsGc = false - } - if (Stats.monitored) recordStatistics(result, savedSuccessCount) - result - } catch { - case NonFatal(ex) => - if (ex.isInstanceOf[AssertionError]) showGoal(tp1, tp2) - recCount -= 1 - constraint = saved - successCount = savedSuccessCount - throw ex - } - } - } - - private def monitoredIsSubType(tp1: Type, tp2: Type) = { - if (pendingSubTypes == null) { - pendingSubTypes = new mutable.HashSet[(Type, Type)] - ctx.log(s"!!! deep subtype recursion involving ${tp1.show} <:< ${tp2.show}, constraint = ${state.constraint.show}") - ctx.log(s"!!! constraint = ${constraint.show}") - //if (ctx.settings.YnoDeepSubtypes.value) { - // new Error("deep subtype").printStackTrace() - //} - assert(!ctx.settings.YnoDeepSubtypes.value) - if (Config.traceDeepSubTypeRecursions && !this.isInstanceOf[ExplainingTypeComparer]) - ctx.log(TypeComparer.explained(implicit ctx => ctx.typeComparer.isSubType(tp1, tp2))) - } - val p = (tp1, tp2) - !pendingSubTypes(p) && { - try { - pendingSubTypes += p - firstTry(tp1, tp2) - } finally { - pendingSubTypes -= p - } - } - } - - private def firstTry(tp1: Type, tp2: Type): Boolean = tp2 match { - case tp2: NamedType => - def compareNamed(tp1: Type, tp2: NamedType): Boolean = { - implicit val ctx: Context = this.ctx - tp2.info match { - case info2: TypeAlias => isSubType(tp1, info2.alias) - case _ => tp1 match { - case tp1: NamedType => - tp1.info match { - case info1: TypeAlias => - if (isSubType(info1.alias, tp2)) return true - if (tp1.prefix.isStable) return false - // If tp1.prefix is stable, the alias does contain all information about the original ref, so - // there's no need to try something else. (This is important for performance). - // To see why we cannot in general stop here, consider: - // - // trait C { type A } - // trait D { type A = String } - // (C & D)#A <: C#A - // - // Following the alias leads to the judgment `String <: C#A` which is false. - // However the original judgment should be true. - case _ => - } - val sym1 = - if (tp1.symbol.is(ModuleClass) && tp2.symbol.is(ModuleVal)) - // For convenience we want X$ <:< X.type - // This is safe because X$ self-type is X.type - tp1.symbol.companionModule - else - tp1.symbol - if ((sym1 ne NoSymbol) && (sym1 eq tp2.symbol)) - ctx.erasedTypes || - sym1.isStaticOwner || - isSubType(tp1.prefix, tp2.prefix) || - thirdTryNamed(tp1, tp2) - else - ( (tp1.name eq tp2.name) - && isSubType(tp1.prefix, tp2.prefix) - && tp1.signature == tp2.signature - && !tp1.isInstanceOf[WithFixedSym] - && !tp2.isInstanceOf[WithFixedSym] - ) || - thirdTryNamed(tp1, tp2) - case _ => - secondTry(tp1, tp2) - } - } - } - compareNamed(tp1, tp2) - case tp2: ProtoType => - isMatchedByProto(tp2, tp1) - case tp2: BoundType => - tp2 == tp1 || secondTry(tp1, tp2) - case tp2: TypeVar => - isSubType(tp1, tp2.underlying) - case tp2: WildcardType => - def compareWild = tp2.optBounds match { - case TypeBounds(_, hi) => isSubType(tp1, hi) - case NoType => true - } - compareWild - case tp2: LazyRef => - !tp2.evaluating && isSubType(tp1, tp2.ref) - case tp2: AnnotatedType => - isSubType(tp1, tp2.tpe) // todo: refine? - case tp2: ThisType => - def compareThis = { - val cls2 = tp2.cls - tp1 match { - case tp1: ThisType => - // We treat two prefixes A.this, B.this as equivalent if - // A's selftype derives from B and B's selftype derives from A. - val cls1 = tp1.cls - cls1.classInfo.selfType.derivesFrom(cls2) && - cls2.classInfo.selfType.derivesFrom(cls1) - case tp1: NamedType if cls2.is(Module) && cls2.eq(tp1.widen.typeSymbol) => - cls2.isStaticOwner || - isSubType(tp1.prefix, cls2.owner.thisType) || - secondTry(tp1, tp2) - case _ => - secondTry(tp1, tp2) - } - } - compareThis - case tp2: SuperType => - def compareSuper = tp1 match { - case tp1: SuperType => - isSubType(tp1.thistpe, tp2.thistpe) && - isSameType(tp1.supertpe, tp2.supertpe) - case _ => - secondTry(tp1, tp2) - } - compareSuper - case AndType(tp21, tp22) => - isSubType(tp1, tp21) && isSubType(tp1, tp22) - case OrType(tp21, tp22) => - if (tp21.stripTypeVar eq tp22.stripTypeVar) isSubType(tp1, tp21) - else secondTry(tp1, tp2) - case TypeErasure.ErasedValueType(tycon1, underlying2) => - def compareErasedValueType = tp1 match { - case TypeErasure.ErasedValueType(tycon2, underlying1) => - (tycon1.symbol eq tycon2.symbol) && isSameType(underlying1, underlying2) - case _ => - secondTry(tp1, tp2) - } - compareErasedValueType - case ErrorType => - true - case _ => - secondTry(tp1, tp2) - } - - private def secondTry(tp1: Type, tp2: Type): Boolean = tp1 match { - case tp1: NamedType => - tp1.info match { - case info1: TypeAlias => - if (isSubType(info1.alias, tp2)) return true - if (tp1.prefix.isStable) return false - case _ => - } - thirdTry(tp1, tp2) - case tp1: PolyParam => - def flagNothingBound = { - if (!frozenConstraint && tp2.isRef(defn.NothingClass) && state.isGlobalCommittable) { - def msg = s"!!! instantiated to Nothing: $tp1, constraint = ${constraint.show}" - if (Config.failOnInstantiationToNothing) assert(false, msg) - else ctx.log(msg) - } - true - } - def comparePolyParam = - ctx.mode.is(Mode.TypevarsMissContext) || - isSubTypeWhenFrozen(bounds(tp1).hi, tp2) || { - if (canConstrain(tp1)) addConstraint(tp1, tp2, fromBelow = false) && flagNothingBound - else thirdTry(tp1, tp2) - } - comparePolyParam - case tp1: ThisType => - val cls1 = tp1.cls - tp2 match { - case tp2: TermRef if cls1.is(Module) && cls1.eq(tp2.widen.typeSymbol) => - cls1.isStaticOwner || - isSubType(cls1.owner.thisType, tp2.prefix) || - thirdTry(tp1, tp2) - case _ => - thirdTry(tp1, tp2) - } - case tp1: SkolemType => - tp2 match { - case tp2: SkolemType if !ctx.phase.isTyper && tp1.info <:< tp2.info => true - case _ => thirdTry(tp1, tp2) - } - case tp1: TypeVar => - isSubType(tp1.underlying, tp2) - case tp1: WildcardType => - def compareWild = tp1.optBounds match { - case TypeBounds(lo, _) => isSubType(lo, tp2) - case _ => true - } - compareWild - case tp1: LazyRef => - // If `tp1` is in train of being evaluated, don't force it - // because that would cause an assertionError. Return false instead. - // See i859.scala for an example where we hit this case. - !tp1.evaluating && isSubType(tp1.ref, tp2) - case tp1: AnnotatedType => - isSubType(tp1.tpe, tp2) - case AndType(tp11, tp12) => - if (tp11.stripTypeVar eq tp12.stripTypeVar) isSubType(tp11, tp2) - else thirdTry(tp1, tp2) - case tp1 @ OrType(tp11, tp12) => - def joinOK = tp2.dealias match { - case tp12: HKApply => - // If we apply the default algorithm for `A[X] | B[Y] <: C[Z]` where `C` is a - // type parameter, we will instantiate `C` to `A` and then fail when comparing - // with `B[Y]`. To do the right thing, we need to instantiate `C` to the - // common superclass of `A` and `B`. - isSubType(tp1.join, tp2) - case _ => - false - } - joinOK || isSubType(tp11, tp2) && isSubType(tp12, tp2) - case ErrorType => - true - case _ => - thirdTry(tp1, tp2) - } - - private def thirdTryNamed(tp1: Type, tp2: NamedType): Boolean = tp2.info match { - case TypeBounds(lo2, _) => - def compareGADT: Boolean = { - val gbounds2 = ctx.gadt.bounds(tp2.symbol) - (gbounds2 != null) && - (isSubTypeWhenFrozen(tp1, gbounds2.lo) || - narrowGADTBounds(tp2, tp1, isUpper = false)) && - GADTusage(tp2.symbol) - } - ((frozenConstraint || !isCappable(tp1)) && isSubType(tp1, lo2) || - compareGADT || - fourthTry(tp1, tp2)) - - case _ => - val cls2 = tp2.symbol - if (cls2.isClass) { - val base = tp1.baseTypeRef(cls2) - if (base.exists && (base ne tp1)) return isSubType(base, tp2) - if (cls2 == defn.SingletonClass && tp1.isStable) return true - } - fourthTry(tp1, tp2) - } - - private def thirdTry(tp1: Type, tp2: Type): Boolean = tp2 match { - case tp2: NamedType => - thirdTryNamed(tp1, tp2) - case tp2: PolyParam => - def comparePolyParam = - (ctx.mode is Mode.TypevarsMissContext) || - isSubTypeWhenFrozen(tp1, bounds(tp2).lo) || { - if (canConstrain(tp2)) addConstraint(tp2, tp1.widenExpr, fromBelow = true) - else fourthTry(tp1, tp2) - } - comparePolyParam - case tp2: RefinedType => - def compareRefinedSlow: Boolean = { - val name2 = tp2.refinedName - isSubType(tp1, tp2.parent) && - (name2 == nme.WILDCARD || hasMatchingMember(name2, tp1, tp2)) - } - def compareRefined: Boolean = { - val tp1w = tp1.widen - val skipped2 = skipMatching(tp1w, tp2) - if ((skipped2 eq tp2) || !Config.fastPathForRefinedSubtype) - tp1 match { - case tp1: AndType => - // Delay calling `compareRefinedSlow` because looking up a member - // of an `AndType` can lead to a cascade of subtyping checks - // This twist is needed to make collection/generic/ParFactory.scala compile - fourthTry(tp1, tp2) || compareRefinedSlow - case _ => - compareRefinedSlow || fourthTry(tp1, tp2) - } - else // fast path, in particular for refinements resulting from parameterization. - isSubRefinements(tp1w.asInstanceOf[RefinedType], tp2, skipped2) && - isSubType(tp1, skipped2) - } - compareRefined - case tp2: RecType => - def compareRec = tp1.safeDealias match { - case tp1: RecType => - val rthis1 = RecThis(tp1) - isSubType(tp1.parent, tp2.parent.substRecThis(tp2, rthis1)) - case _ => - val tp1stable = ensureStableSingleton(tp1) - isSubType(fixRecs(tp1stable, tp1stable.widenExpr), tp2.parent.substRecThis(tp2, tp1stable)) - } - compareRec - case tp2 @ HKApply(tycon2, args2) => - compareHkApply2(tp1, tp2, tycon2, args2) - case tp2 @ PolyType(tparams2, body2) => - def compareHkLambda: Boolean = tp1.stripTypeVar match { - case tp1 @ PolyType(tparams1, body1) => - /* Don't compare bounds of lambdas under language:Scala2, or t2994 will fail - * The issue is that, logically, bounds should compare contravariantly, - * but that would invalidate a pattern exploited in t2994: - * - * [X0 <: Number] -> Number <:< [X0] -> Any - * - * Under the new scheme, `[X0] -> Any` is NOT a kind that subsumes - * all other bounds. You'd have to write `[X0 >: Any <: Nothing] -> Any` instead. - * This might look weird, but is the only logically correct way to do it. - * - * Note: it would be nice if this could trigger a migration warning, but I - * am not sure how, since the code is buried so deep in subtyping logic. - */ - def boundsOK = - ctx.scala2Mode || - tparams1.corresponds(tparams2)((tparam1, tparam2) => - isSubType(tparam2.paramBounds.subst(tp2, tp1), tparam1.paramBounds)) - val saved = comparedPolyTypes - comparedPolyTypes += tp1 - comparedPolyTypes += tp2 - try - variancesConform(tparams1, tparams2) && - boundsOK && - isSubType(body1, body2.subst(tp2, tp1)) - finally comparedPolyTypes = saved - case _ => - if (!tp1.isHK) { - tp2 match { - case EtaExpansion(tycon2) if tycon2.symbol.isClass => - return isSubType(tp1, tycon2) - case _ => - } - } - fourthTry(tp1, tp2) - } - compareHkLambda - case OrType(tp21, tp22) => - // Rewrite T1 <: (T211 & T212) | T22 to T1 <: (T211 | T22) and T1 <: (T212 | T22) - // and analogously for T1 <: T21 | (T221 & T222) - // `|' types to the right of <: are problematic, because - // we have to choose one constraint set or another, which might cut off - // solutions. The rewriting delays the point where we have to choose. - tp21 match { - case AndType(tp211, tp212) => - return isSubType(tp1, OrType(tp211, tp22)) && isSubType(tp1, OrType(tp212, tp22)) - case _ => - } - tp22 match { - case AndType(tp221, tp222) => - return isSubType(tp1, OrType(tp21, tp221)) && isSubType(tp1, OrType(tp21, tp222)) - case _ => - } - either(isSubType(tp1, tp21), isSubType(tp1, tp22)) || fourthTry(tp1, tp2) - case tp2 @ MethodType(_, formals2) => - def compareMethod = tp1 match { - case tp1 @ MethodType(_, formals1) => - (tp1.signature consistentParams tp2.signature) && - matchingParams(formals1, formals2, tp1.isJava, tp2.isJava) && - tp1.isImplicit == tp2.isImplicit && // needed? - isSubType(tp1.resultType, tp2.resultType.subst(tp2, tp1)) - case _ => - false - } - compareMethod - case tp2 @ ExprType(restpe2) => - def compareExpr = tp1 match { - // We allow ()T to be a subtype of => T. - // We need some subtype relationship between them so that e.g. - // def toString and def toString() don't clash when seen - // as members of the same type. And it seems most logical to take - // ()T <:< => T, since everything one can do with a => T one can - // also do with a ()T by automatic () insertion. - case tp1 @ MethodType(Nil, _) => isSubType(tp1.resultType, restpe2) - case _ => isSubType(tp1.widenExpr, restpe2) - } - compareExpr - case tp2 @ TypeBounds(lo2, hi2) => - def compareTypeBounds = tp1 match { - case tp1 @ TypeBounds(lo1, hi1) => - (tp2.variance > 0 && tp1.variance >= 0 || (lo2 eq NothingType) || isSubType(lo2, lo1)) && - (tp2.variance < 0 && tp1.variance <= 0 || (hi2 eq AnyType) || isSubType(hi1, hi2)) - case tp1: ClassInfo => - tp2 contains tp1 - case _ => - false - } - compareTypeBounds - case ClassInfo(pre2, cls2, _, _, _) => - def compareClassInfo = tp1 match { - case ClassInfo(pre1, cls1, _, _, _) => - (cls1 eq cls2) && isSubType(pre1, pre2) - case _ => - false - } - compareClassInfo - case _ => - fourthTry(tp1, tp2) - } - - private def fourthTry(tp1: Type, tp2: Type): Boolean = tp1 match { - case tp1: TypeRef => - tp1.info match { - case TypeBounds(_, hi1) => - def compareGADT = { - val gbounds1 = ctx.gadt.bounds(tp1.symbol) - (gbounds1 != null) && - (isSubTypeWhenFrozen(gbounds1.hi, tp2) || - narrowGADTBounds(tp1, tp2, isUpper = true)) && - GADTusage(tp1.symbol) - } - isSubType(hi1, tp2) || compareGADT - case _ => - def isNullable(tp: Type): Boolean = tp.widenDealias match { - case tp: TypeRef => tp.symbol.isNullableClass - case tp: RefinedOrRecType => isNullable(tp.parent) - case AndType(tp1, tp2) => isNullable(tp1) && isNullable(tp2) - case OrType(tp1, tp2) => isNullable(tp1) || isNullable(tp2) - case _ => false - } - (tp1.symbol eq NothingClass) && tp2.isValueTypeOrLambda || - (tp1.symbol eq NullClass) && isNullable(tp2) - } - case tp1: SingletonType => - /** if `tp2 == p.type` and `p: q.type` then try `tp1 <:< q.type` as a last effort.*/ - def comparePaths = tp2 match { - case tp2: TermRef => - tp2.info.widenExpr match { - case tp2i: SingletonType => - isSubType(tp1, tp2i) // see z1720.scala for a case where this can arise even in typer. - case _ => false - } - case _ => - false - } - isNewSubType(tp1.underlying.widenExpr, tp2) || comparePaths - case tp1: RefinedType => - isNewSubType(tp1.parent, tp2) - case tp1: RecType => - isNewSubType(tp1.parent, tp2) - case tp1 @ HKApply(tycon1, args1) => - compareHkApply1(tp1, tycon1, args1, tp2) - case EtaExpansion(tycon1) => - isSubType(tycon1, tp2) - case AndType(tp11, tp12) => - // Rewrite (T111 | T112) & T12 <: T2 to (T111 & T12) <: T2 and (T112 | T12) <: T2 - // and analogously for T11 & (T121 | T122) & T12 <: T2 - // `&' types to the left of <: are problematic, because - // we have to choose one constraint set or another, which might cut off - // solutions. The rewriting delays the point where we have to choose. - tp11 match { - case OrType(tp111, tp112) => - return isSubType(AndType(tp111, tp12), tp2) && isSubType(AndType(tp112, tp12), tp2) - case _ => - } - tp12 match { - case OrType(tp121, tp122) => - return isSubType(AndType(tp11, tp121), tp2) && isSubType(AndType(tp11, tp122), tp2) - case _ => - } - either(isSubType(tp11, tp2), isSubType(tp12, tp2)) - case JavaArrayType(elem1) => - def compareJavaArray = tp2 match { - case JavaArrayType(elem2) => isSubType(elem1, elem2) - case _ => tp2 isRef ObjectClass - } - compareJavaArray - case tp1: ExprType if ctx.phase.id > ctx.gettersPhase.id => - // getters might have converted T to => T, need to compensate. - isSubType(tp1.widenExpr, tp2) - case _ => - false - } - - /** Subtype test for the hk application `tp2 = tycon2[args2]`. - */ - def compareHkApply2(tp1: Type, tp2: HKApply, tycon2: Type, args2: List[Type]): Boolean = { - val tparams = tycon2.typeParams - if (tparams.isEmpty) return false // can happen for ill-typed programs, e.g. neg/tcpoly_overloaded.scala - - /** True if `tp1` and `tp2` have compatible type constructors and their - * corresponding arguments are subtypes relative to their variance (see `isSubArgs`). - */ - def isMatchingApply(tp1: Type): Boolean = tp1 match { - case HKApply(tycon1, args1) => - tycon1.dealias match { - case tycon1: PolyParam => - (tycon1 == tycon2 || - canConstrain(tycon1) && tryInstantiate(tycon1, tycon2)) && - isSubArgs(args1, args2, tparams) - case tycon1: TypeRef => - tycon2.dealias match { - case tycon2: TypeRef if tycon1.symbol == tycon2.symbol => - isSubType(tycon1.prefix, tycon2.prefix) && - isSubArgs(args1, args2, tparams) - case _ => - false - } - case tycon1: TypeVar => - isMatchingApply(tycon1.underlying) - case tycon1: AnnotatedType => - isMatchingApply(tycon1.underlying) - case _ => - false - } - case _ => - false - } - - /** `param2` can be instantiated to a type application prefix of the LHS - * or to a type application prefix of one of the LHS base class instances - * and the resulting type application is a supertype of `tp1`, - * or fallback to fourthTry. - */ - def canInstantiate(tycon2: PolyParam): Boolean = { - - /** Let - * - * `tparams_1, ..., tparams_k-1` be the type parameters of the rhs - * `tparams1_1, ..., tparams1_n-1` be the type parameters of the constructor of the lhs - * `args1_1, ..., args1_n-1` be the type arguments of the lhs - * `d = n - k` - * - * Returns `true` iff `d >= 0` and `tycon2` can be instantiated to - * - * [tparams1_d, ... tparams1_n-1] -> tycon1a[args_1, ..., args_d-1, tparams_d, ... tparams_n-1] - * - * such that the resulting type application is a supertype of `tp1`. - */ - def tyconOK(tycon1a: Type, args1: List[Type]) = { - var tycon1b = tycon1a - val tparams1a = tycon1a.typeParams - val lengthDiff = tparams1a.length - tparams.length - lengthDiff >= 0 && { - val tparams1 = tparams1a.drop(lengthDiff) - variancesConform(tparams1, tparams) && { - if (lengthDiff > 0) - tycon1b = PolyType(tparams1.map(_.paramName), tparams1.map(_.paramVariance))( - tl => tparams1.map(tparam => tl.lifted(tparams, tparam.paramBounds).bounds), - tl => tycon1a.appliedTo(args1.take(lengthDiff) ++ - tparams1.indices.toList.map(PolyParam(tl, _)))) - (ctx.mode.is(Mode.TypevarsMissContext) || - tryInstantiate(tycon2, tycon1b.ensureHK)) && - isSubType(tp1, tycon1b.appliedTo(args2)) - } - } - } - - tp1.widen match { - case tp1w @ HKApply(tycon1, args1) => - tyconOK(tycon1, args1) - case tp1w => - tp1w.typeSymbol.isClass && { - val classBounds = tycon2.classSymbols - def liftToBase(bcs: List[ClassSymbol]): Boolean = bcs match { - case bc :: bcs1 => - classBounds.exists(bc.derivesFrom) && - tyconOK(tp1w.baseTypeRef(bc), tp1w.baseArgInfos(bc)) || - liftToBase(bcs1) - case _ => - false - } - liftToBase(tp1w.baseClasses) - } || - fourthTry(tp1, tp2) - } - } - - /** Fall back to comparing either with `fourthTry` or against the lower - * approximation of the rhs. - * @param tyconLo The type constructor's lower approximation. - */ - def fallback(tyconLo: Type) = - either(fourthTry(tp1, tp2), isSubType(tp1, tyconLo.applyIfParameterized(args2))) - - /** Let `tycon2bounds` be the bounds of the RHS type constructor `tycon2`. - * Let `app2 = tp2` where the type constructor of `tp2` is replaced by - * `tycon2bounds.lo`. - * If both bounds are the same, continue with `tp1 <:< app2`. - * otherwise continue with either - * - * tp1 <:< tp2 using fourthTry (this might instantiate params in tp1) - * tp1 <:< app2 using isSubType (this might instantiate params in tp2) - */ - def compareLower(tycon2bounds: TypeBounds, tyconIsTypeRef: Boolean): Boolean = - if (tycon2bounds.lo eq tycon2bounds.hi) - isSubType(tp1, - if (tyconIsTypeRef) tp2.superType - else tycon2bounds.lo.applyIfParameterized(args2)) - else - fallback(tycon2bounds.lo) - - tycon2 match { - case param2: PolyParam => - isMatchingApply(tp1) || { - if (canConstrain(param2)) canInstantiate(param2) - else compareLower(bounds(param2), tyconIsTypeRef = false) - } - case tycon2: TypeRef => - isMatchingApply(tp1) || - compareLower(tycon2.info.bounds, tyconIsTypeRef = true) - case _: TypeVar | _: AnnotatedType => - isSubType(tp1, tp2.superType) - case tycon2: HKApply => - fallback(tycon2.lowerBound) - case _ => - false - } - } - - /** Subtype test for the hk application `tp1 = tycon1[args1]`. - */ - def compareHkApply1(tp1: HKApply, tycon1: Type, args1: List[Type], tp2: Type): Boolean = - tycon1 match { - case param1: PolyParam => - def canInstantiate = tp2 match { - case AppliedType(tycon2, args2) => - tryInstantiate(param1, tycon2.ensureHK) && isSubArgs(args1, args2, tycon2.typeParams) - case _ => - false - } - canConstrain(param1) && canInstantiate || - isSubType(bounds(param1).hi.applyIfParameterized(args1), tp2) - case tycon1: TypeProxy => - isSubType(tp1.superType, tp2) - case _ => - false - } - - /** Subtype test for corresponding arguments in `args1`, `args2` according to - * variances in type parameters `tparams`. - */ - def isSubArgs(args1: List[Type], args2: List[Type], tparams: List[TypeParamInfo]): Boolean = - if (args1.isEmpty) args2.isEmpty - else args2.nonEmpty && { - val v = tparams.head.paramVariance - (v > 0 || isSubType(args2.head, args1.head)) && - (v < 0 || isSubType(args1.head, args2.head)) - } && isSubArgs(args1.tail, args2.tail, tparams) - - /** Test whether `tp1` has a base type of the form `B[T1, ..., Tn]` where - * - `B` derives from one of the class symbols of `tp2`, - * - the type parameters of `B` match one-by-one the variances of `tparams`, - * - `B` satisfies predicate `p`. - */ - private def testLifted(tp1: Type, tp2: Type, tparams: List[TypeParamInfo], p: Type => Boolean): Boolean = { - val classBounds = tp2.classSymbols - def recur(bcs: List[ClassSymbol]): Boolean = bcs match { - case bc :: bcs1 => - val baseRef = tp1.baseTypeRef(bc) - (classBounds.exists(bc.derivesFrom) && - variancesConform(baseRef.typeParams, tparams) && - p(baseRef.appliedTo(tp1.baseArgInfos(bc))) - || - recur(bcs1)) - case nil => - false - } - recur(tp1.baseClasses) - } - - /** Replace any top-level recursive type `{ z => T }` in `tp` with - * `[z := anchor]T`. - */ - private def fixRecs(anchor: SingletonType, tp: Type): Type = { - def fix(tp: Type): Type = tp.stripTypeVar match { - case tp: RecType => fix(tp.parent).substRecThis(tp, anchor) - case tp @ RefinedType(parent, rname, rinfo) => tp.derivedRefinedType(fix(parent), rname, rinfo) - case tp: PolyParam => fixOrElse(bounds(tp).hi, tp) - case tp: TypeProxy => fixOrElse(tp.underlying, tp) - case tp: AndOrType => tp.derivedAndOrType(fix(tp.tp1), fix(tp.tp2)) - case tp => tp - } - def fixOrElse(tp: Type, fallback: Type) = { - val tp1 = fix(tp) - if (tp1 ne tp) tp1 else fallback - } - fix(tp) - } - - /** Returns true iff the result of evaluating either `op1` or `op2` is true, - * trying at the same time to keep the constraint as wide as possible. - * E.g, if - * - * tp11 <:< tp12 = true with post-constraint c1 - * tp12 <:< tp22 = true with post-constraint c2 - * - * and c1 subsumes c2, then c2 is kept as the post-constraint of the result, - * otherwise c1 is kept. - * - * This method is used to approximate a solution in one of the following cases - * - * T1 & T2 <:< T3 - * T1 <:< T2 | T3 - * - * In the first case (the second one is analogous), we have a choice whether we - * want to establish the subtyping judgement using - * - * T1 <:< T3 or T2 <:< T3 - * - * as a precondition. Either precondition might constrain type variables. - * The purpose of this method is to pick the precondition that constrains less. - * The method is not complete, because sometimes there is no best solution. Example: - * - * A? & B? <: T - * - * Here, each precondition leads to a different constraint, and neither of - * the two post-constraints subsumes the other. - */ - private def either(op1: => Boolean, op2: => Boolean): Boolean = { - val preConstraint = constraint - op1 && { - val leftConstraint = constraint - constraint = preConstraint - if (!(op2 && subsumes(leftConstraint, constraint, preConstraint))) { - if (constr != noPrinter && !subsumes(constraint, leftConstraint, preConstraint)) - constr.println(i"CUT - prefer $leftConstraint over $constraint") - constraint = leftConstraint - } - true - } || op2 - } - - /** Like tp1 <:< tp2, but returns false immediately if we know that - * the case was covered previously during subtyping. - */ - private def isNewSubType(tp1: Type, tp2: Type): Boolean = - if (isCovered(tp1) && isCovered(tp2)) { - //println(s"useless subtype: $tp1 <:< $tp2") - false - } else isSubType(tp1, tp2) - - /** Does type `tp1` have a member with name `name` whose normalized type is a subtype of - * the normalized type of the refinement `tp2`? - * Normalization is as follows: If `tp2` contains a skolem to its refinement type, - * rebase both itself and the member info of `tp` on a freshly created skolem type. - */ - protected def hasMatchingMember(name: Name, tp1: Type, tp2: RefinedType): Boolean = { - val rinfo2 = tp2.refinedInfo - val mbr = tp1.member(name) - - def qualifies(m: SingleDenotation) = isSubType(m.info, rinfo2) - - def memberMatches: Boolean = mbr match { // inlined hasAltWith for performance - case mbr: SingleDenotation => qualifies(mbr) - case _ => mbr hasAltWith qualifies - } - - // special case for situations like: - // class C { type T } - // val foo: C - // foo.type <: C { type T {= , <: , >:} foo.T } - def selfReferentialMatch = tp1.isInstanceOf[SingletonType] && { - rinfo2 match { - case rinfo2: TypeBounds => - val mbr1 = tp1.select(name) - !defn.isBottomType(tp1.widen) && - (mbr1 =:= rinfo2.hi || (rinfo2.hi ne rinfo2.lo) && mbr1 =:= rinfo2.lo) - case _ => false - } - } - - /*>|>*/ ctx.traceIndented(i"hasMatchingMember($tp1 . $name :? ${tp2.refinedInfo}) ${mbr.info.show} $rinfo2", subtyping) /*<|<*/ { - memberMatches || selfReferentialMatch - } - } - - final def ensureStableSingleton(tp: Type): SingletonType = tp.stripTypeVar match { - case tp: SingletonType if tp.isStable => tp - case tp: ValueType => SkolemType(tp) - case tp: TypeProxy => ensureStableSingleton(tp.underlying) - } - - /** Skip refinements in `tp2` which match corresponding refinements in `tp1`. - * "Match" means: - * - they appear in the same order, - * - they refine the same names, - * - the refinement in `tp1` is an alias type, and - * - neither refinement refers back to the refined type via a refined this. - * @return The parent type of `tp2` after skipping the matching refinements. - */ - private def skipMatching(tp1: Type, tp2: RefinedType): Type = tp1 match { - case tp1 @ RefinedType(parent1, name1, rinfo1: TypeAlias) if name1 == tp2.refinedName => - tp2.parent match { - case parent2: RefinedType => skipMatching(parent1, parent2) - case parent2 => parent2 - } - case _ => tp2 - } - - /** Are refinements in `tp1` pairwise subtypes of the refinements of `tp2` - * up to parent type `limit`? - * @pre `tp1` has the necessary number of refinements, they are type aliases, - * and their names match the corresponding refinements in `tp2`. - * Further, no refinement refers back to the refined type via a refined this. - * The precondition is established by `skipMatching`. - */ - private def isSubRefinements(tp1: RefinedType, tp2: RefinedType, limit: Type): Boolean = { - def hasSubRefinement(tp1: RefinedType, refine2: Type): Boolean = { - isSubType(tp1.refinedInfo, refine2) || { - // last effort: try to adapt variances of higher-kinded types if this is sound. - val adapted2 = refine2.adaptHkVariances(tp1.parent.member(tp1.refinedName).symbol.info) - adapted2.ne(refine2) && hasSubRefinement(tp1, adapted2) - } - } - hasSubRefinement(tp1, tp2.refinedInfo) && ( - (tp2.parent eq limit) || - isSubRefinements( - tp1.parent.asInstanceOf[RefinedType], tp2.parent.asInstanceOf[RefinedType], limit)) - } - - /** A type has been covered previously in subtype checking if it - * is some combination of TypeRefs that point to classes, where the - * combiners are RefinedTypes, RecTypes, AndTypes or AnnotatedTypes. - * One exception: Refinements referring to basetype args are never considered - * to be already covered. This is necessary because such refined types might - * still need to be compared with a compareAliasRefined. - */ - private def isCovered(tp: Type): Boolean = tp.dealias.stripTypeVar match { - case tp: TypeRef => tp.symbol.isClass && tp.symbol != NothingClass && tp.symbol != NullClass - case tp: ProtoType => false - case tp: RefinedOrRecType => isCovered(tp.parent) - case tp: AnnotatedType => isCovered(tp.underlying) - case AndType(tp1, tp2) => isCovered(tp1) && isCovered(tp2) - case _ => false - } - - /** Defer constraining type variables when compared against prototypes */ - def isMatchedByProto(proto: ProtoType, tp: Type) = tp.stripTypeVar match { - case tp: PolyParam if constraint contains tp => true - case _ => proto.isMatchedBy(tp) - } - - /** Can type `tp` be constrained from above by adding a constraint to - * a typevar that it refers to? In that case we have to be careful not - * to approximate with the lower bound of a type in `thirdTry`. Instead, - * we should first unroll `tp1` until we hit the type variable and bind the - * type variable with (the corresponding type in) `tp2` instead. - */ - private def isCappable(tp: Type): Boolean = tp match { - case tp: PolyParam => constraint contains tp - case tp: TypeProxy => isCappable(tp.underlying) - case tp: AndOrType => isCappable(tp.tp1) || isCappable(tp.tp2) - case _ => false - } - - /** Narrow gadt.bounds for the type parameter referenced by `tr` to include - * `bound` as an upper or lower bound (which depends on `isUpper`). - * Test that the resulting bounds are still satisfiable. - */ - private def narrowGADTBounds(tr: NamedType, bound: Type, isUpper: Boolean): Boolean = - ctx.mode.is(Mode.GADTflexible) && !frozenConstraint && { - val tparam = tr.symbol - typr.println(i"narrow gadt bound of $tparam: ${tparam.info} from ${if (isUpper) "above" else "below"} to $bound ${bound.isRef(tparam)}") - if (bound.isRef(tparam)) false - else bound match { - case bound: TypeRef - if bound.symbol.is(BindDefinedType) && - ctx.gadt.bounds.contains(bound.symbol) && - !tr.symbol.is(BindDefinedType) => - // Avoid having pattern-bound types in gadt bounds, - // as these might be eliminated once the pattern is typechecked. - // Pattern-bound type symbols should be narrowed first, only if that fails - // should symbols in the environment be constrained. - narrowGADTBounds(bound, tr, !isUpper) - case _ => - val oldBounds = ctx.gadt.bounds(tparam) - val newBounds = - if (isUpper) TypeBounds(oldBounds.lo, oldBounds.hi & bound) - else TypeBounds(oldBounds.lo | bound, oldBounds.hi) - isSubType(newBounds.lo, newBounds.hi) && - { ctx.gadt.setBounds(tparam, newBounds); true } - } - } - - // Tests around `matches` - - /** A function implementing `tp1` matches `tp2`. */ - final def matchesType(tp1: Type, tp2: Type, relaxed: Boolean): Boolean = tp1.widen match { - case tp1: MethodType => - tp2.widen match { - case tp2: MethodType => - tp1.isImplicit == tp2.isImplicit && - matchingParams(tp1.paramTypes, tp2.paramTypes, tp1.isJava, tp2.isJava) && - matchesType(tp1.resultType, tp2.resultType.subst(tp2, tp1), relaxed) - case tp2 => - relaxed && tp1.paramNames.isEmpty && - matchesType(tp1.resultType, tp2, relaxed) - } - case tp1: PolyType => - tp2.widen match { - case tp2: PolyType => - sameLength(tp1.paramNames, tp2.paramNames) && - matchesType(tp1.resultType, tp2.resultType.subst(tp2, tp1), relaxed) - case _ => - false - } - case _ => - tp2.widen match { - case _: PolyType => - false - case tp2: MethodType => - relaxed && tp2.paramNames.isEmpty && - matchesType(tp1, tp2.resultType, relaxed) - case tp2 => - relaxed || isSameType(tp1, tp2) - } - } - - /** Are `syms1` and `syms2` parameter lists with pairwise equivalent types? */ - def matchingParams(formals1: List[Type], formals2: List[Type], isJava1: Boolean, isJava2: Boolean): Boolean = formals1 match { - case formal1 :: rest1 => - formals2 match { - case formal2 :: rest2 => - (isSameTypeWhenFrozen(formal1, formal2) - || isJava1 && (formal2 isRef ObjectClass) && (formal1 isRef AnyClass) - || isJava2 && (formal1 isRef ObjectClass) && (formal2 isRef AnyClass)) && - matchingParams(rest1, rest2, isJava1, isJava2) - case nil => - false - } - case nil => - formals2.isEmpty - } - - /** Do generic types `poly1` and `poly2` have type parameters that - * have the same bounds (after renaming one set to the other)? - */ - def matchingTypeParams(poly1: PolyType, poly2: PolyType): Boolean = - (poly1.paramBounds corresponds poly2.paramBounds)((b1, b2) => - isSameType(b1, b2.subst(poly2, poly1))) - - // Type equality =:= - - /** Two types are the same if are mutual subtypes of each other */ - def isSameType(tp1: Type, tp2: Type): Boolean = - if (tp1 eq NoType) false - else if (tp1 eq tp2) true - else isSubType(tp1, tp2) && isSubType(tp2, tp1) - - /** Same as `isSameType` but also can be applied to overloaded TermRefs, where - * two overloaded refs are the same if they have pairwise equal alternatives - */ - def isSameRef(tp1: Type, tp2: Type): Boolean = ctx.traceIndented(s"isSameRef($tp1, $tp2") { - def isSubRef(tp1: Type, tp2: Type): Boolean = tp1 match { - case tp1: TermRef if tp1.isOverloaded => - tp1.alternatives forall (isSubRef(_, tp2)) - case _ => - tp2 match { - case tp2: TermRef if tp2.isOverloaded => - tp2.alternatives exists (isSubRef(tp1, _)) - case _ => - isSubType(tp1, tp2) - } - } - isSubRef(tp1, tp2) && isSubRef(tp2, tp1) - } - - /** The greatest lower bound of two types */ - def glb(tp1: Type, tp2: Type): Type = /*>|>*/ ctx.traceIndented(s"glb(${tp1.show}, ${tp2.show})", subtyping, show = true) /*<|<*/ { - if (tp1 eq tp2) tp1 - else if (!tp1.exists) tp2 - else if (!tp2.exists) tp1 - else if ((tp1 isRef AnyClass) || (tp2 isRef NothingClass)) tp2 - else if ((tp2 isRef AnyClass) || (tp1 isRef NothingClass)) tp1 - else tp2 match { // normalize to disjunctive normal form if possible. - case OrType(tp21, tp22) => - tp1 & tp21 | tp1 & tp22 - case _ => - tp1 match { - case OrType(tp11, tp12) => - tp11 & tp2 | tp12 & tp2 - case _ => - val t1 = mergeIfSub(tp1, tp2) - if (t1.exists) t1 - else { - val t2 = mergeIfSub(tp2, tp1) - if (t2.exists) t2 - else tp1 match { - case tp1: ConstantType => - tp2 match { - case tp2: ConstantType => - // Make use of the fact that the intersection of two constant types - // types which are not subtypes of each other is known to be empty. - // Note: The same does not apply to singleton types in general. - // E.g. we could have a pattern match against `x.type & y.type` - // which might succeed if `x` and `y` happen to be the same ref - // at run time. It would not work to replace that with `Nothing`. - // However, maybe we can still apply the replacement to - // types which are not explicitly written. - defn.NothingType - case _ => andType(tp1, tp2) - } - case _ => andType(tp1, tp2) - } - } - } - } - } - - /** The greatest lower bound of a list types */ - final def glb(tps: List[Type]): Type = - ((defn.AnyType: Type) /: tps)(glb) - - /** The least upper bound of two types - * @note We do not admit singleton types in or-types as lubs. - */ - def lub(tp1: Type, tp2: Type): Type = /*>|>*/ ctx.traceIndented(s"lub(${tp1.show}, ${tp2.show})", subtyping, show = true) /*<|<*/ { - if (tp1 eq tp2) tp1 - else if (!tp1.exists) tp1 - else if (!tp2.exists) tp2 - else if ((tp1 isRef AnyClass) || (tp2 isRef NothingClass)) tp1 - else if ((tp2 isRef AnyClass) || (tp1 isRef NothingClass)) tp2 - else { - val t1 = mergeIfSuper(tp1, tp2) - if (t1.exists) t1 - else { - val t2 = mergeIfSuper(tp2, tp1) - if (t2.exists) t2 - else { - val tp1w = tp1.widen - val tp2w = tp2.widen - if ((tp1 ne tp1w) || (tp2 ne tp2w)) lub(tp1w, tp2w) - else orType(tp1w, tp2w) // no need to check subtypes again - } - } - } - } - - /** The least upper bound of a list of types */ - final def lub(tps: List[Type]): Type = - ((defn.NothingType: Type) /: tps)(lub) - - /** Merge `t1` into `tp2` if t1 is a subtype of some &-summand of tp2. - */ - private def mergeIfSub(tp1: Type, tp2: Type): Type = - if (isSubTypeWhenFrozen(tp1, tp2)) - if (isSubTypeWhenFrozen(tp2, tp1)) tp2 else tp1 // keep existing type if possible - else tp2 match { - case tp2 @ AndType(tp21, tp22) => - val lower1 = mergeIfSub(tp1, tp21) - if (lower1 eq tp21) tp2 - else if (lower1.exists) lower1 & tp22 - else { - val lower2 = mergeIfSub(tp1, tp22) - if (lower2 eq tp22) tp2 - else if (lower2.exists) tp21 & lower2 - else NoType - } - case _ => - NoType - } - - /** Merge `tp1` into `tp2` if tp1 is a supertype of some |-summand of tp2. - */ - private def mergeIfSuper(tp1: Type, tp2: Type): Type = - if (isSubTypeWhenFrozen(tp2, tp1)) - if (isSubTypeWhenFrozen(tp1, tp2)) tp2 else tp1 // keep existing type if possible - else tp2 match { - case tp2 @ OrType(tp21, tp22) => - val higher1 = mergeIfSuper(tp1, tp21) - if (higher1 eq tp21) tp2 - else if (higher1.exists) higher1 | tp22 - else { - val higher2 = mergeIfSuper(tp1, tp22) - if (higher2 eq tp22) tp2 - else if (higher2.exists) tp21 | higher2 - else NoType - } - case _ => - NoType - } - - /** Form a normalized conjunction of two types. - * Note: For certain types, `&` is distributed inside the type. This holds for - * all types which are not value types (e.g. TypeBounds, ClassInfo, - * ExprType, MethodType, PolyType). Also, when forming an `&`, - * instantiated TypeVars are dereferenced and annotations are stripped. - * Finally, refined types with the same refined name are - * opportunistically merged. - * - * Sometimes, the conjunction of two types cannot be formed because - * the types are in conflict of each other. In particular: - * - * 1. Two different class types are conflicting. - * 2. A class type conflicts with a type bounds that does not include the class reference. - * 3. Two method or poly types with different (type) parameters but the same - * signature are conflicting - * - * In these cases, a MergeError is thrown. - */ - final def andType(tp1: Type, tp2: Type, erased: Boolean = ctx.erasedTypes) = ctx.traceIndented(s"glb(${tp1.show}, ${tp2.show})", subtyping, show = true) { - val t1 = distributeAnd(tp1, tp2) - if (t1.exists) t1 - else { - val t2 = distributeAnd(tp2, tp1) - if (t2.exists) t2 - else if (erased) erasedGlb(tp1, tp2, isJava = false) - else liftIfHK(tp1, tp2, AndType(_, _), _ & _) - } - } - - /** Form a normalized conjunction of two types. - * Note: For certain types, `|` is distributed inside the type. This holds for - * all types which are not value types (e.g. TypeBounds, ClassInfo, - * ExprType, MethodType, PolyType). Also, when forming an `|`, - * instantiated TypeVars are dereferenced and annotations are stripped. - * - * Sometimes, the disjunction of two types cannot be formed because - * the types are in conflict of each other. (@see `andType` for an enumeration - * of these cases). In cases of conflict a `MergeError` is raised. - * - * @param erased Apply erasure semantics. If erased is true, instead of creating - * an OrType, the lub will be computed using TypeCreator#erasedLub. - */ - final def orType(tp1: Type, tp2: Type, erased: Boolean = ctx.erasedTypes) = { - val t1 = distributeOr(tp1, tp2) - if (t1.exists) t1 - else { - val t2 = distributeOr(tp2, tp1) - if (t2.exists) t2 - else if (erased) erasedLub(tp1, tp2) - else liftIfHK(tp1, tp2, OrType(_, _), _ | _) - } - } - - /** `op(tp1, tp2)` unless `tp1` and `tp2` are type-constructors with at least - * some unnamed type parameters. - * In the latter case, combine `tp1` and `tp2` under a type lambda like this: - * - * [X1, ..., Xn] -> op(tp1[X1, ..., Xn], tp2[X1, ..., Xn]) - * - * Note: There is a tension between named and positional parameters here, which - * is impossible to resolve completely. Say you have - * - * C[type T], D[type U] - * - * Then do you expand `C & D` to `[T] -> C[T] & D[T]` or not? Under the named - * type parameter interpretation, this would be wrong whereas under the traditional - * higher-kinded interpretation this would be required. The problem arises from - * allowing both interpretations. A possible remedy is to be somehow stricter - * in where we allow which interpretation. - */ - private def liftIfHK(tp1: Type, tp2: Type, op: (Type, Type) => Type, original: (Type, Type) => Type) = { - val tparams1 = tp1.typeParams - val tparams2 = tp2.typeParams - if (tparams1.isEmpty) - if (tparams2.isEmpty) op(tp1, tp2) - else original(tp1, tp2.appliedTo(tp2.typeParams.map(_.paramBoundsAsSeenFrom(tp2)))) - else if (tparams2.isEmpty) - original(tp1.appliedTo(tp1.typeParams.map(_.paramBoundsAsSeenFrom(tp1))), tp2) - else - PolyType( - paramNames = tpnme.syntheticTypeParamNames(tparams1.length), - variances = (tparams1, tparams2).zipped.map((tparam1, tparam2) => - (tparam1.paramVariance + tparam2.paramVariance) / 2))( - paramBoundsExp = tl => (tparams1, tparams2).zipped.map((tparam1, tparam2) => - tl.lifted(tparams1, tparam1.paramBoundsAsSeenFrom(tp1)).bounds & - tl.lifted(tparams2, tparam2.paramBoundsAsSeenFrom(tp2)).bounds), - resultTypeExp = tl => - original(tl.lifted(tparams1, tp1).appliedTo(tl.paramRefs), - tl.lifted(tparams2, tp2).appliedTo(tl.paramRefs))) - } - - /** Try to distribute `&` inside type, detect and handle conflicts - * @pre !(tp1 <: tp2) && !(tp2 <:< tp1) -- these cases were handled before - */ - private def distributeAnd(tp1: Type, tp2: Type): Type = tp1 match { - // opportunistically merge same-named refinements - // this does not change anything semantically (i.e. merging or not merging - // gives =:= types), but it keeps the type smaller. - case tp1: RefinedType => - tp2 match { - case tp2: RefinedType if tp1.refinedName == tp2.refinedName => - // Given two refinements `T1 { X = S1 }` and `T2 { X = S2 }`, if `S1 =:= S2` - // (possibly by instantiating type parameters), rewrite to `T1 & T2 { X = S1 }`. - // Otherwise rewrite to `T1 & T2 { X B }` where `B` is the conjunction of - // the bounds of `X` in `T1` and `T2`. - // The first rule above is contentious because it cuts the constraint set. - // But without it we would replace the two aliases by - // `T { X >: S1 | S2 <: S1 & S2 }`, which looks weird and is probably - // not what's intended. - val rinfo1 = tp1.refinedInfo - val rinfo2 = tp2.refinedInfo - val parent = tp1.parent & tp2.parent - val rinfo = - if (rinfo1.isAlias && rinfo2.isAlias && isSameType(rinfo1, rinfo2)) - rinfo1 - else - rinfo1 & rinfo2 - tp1.derivedRefinedType(parent, tp1.refinedName, rinfo) - case _ => - NoType - } - case tp1: RecType => - tp1.rebind(distributeAnd(tp1.parent, tp2)) - case ExprType(rt1) => - tp2 match { - case ExprType(rt2) => - ExprType(rt1 & rt2) - case _ => - rt1 & tp2 - } - case tp1: TypeVar if tp1.isInstantiated => - tp1.underlying & tp2 - case tp1: AnnotatedType => - tp1.underlying & tp2 - case _ => - NoType - } - - /** Try to distribute `|` inside type, detect and handle conflicts - * Note that, unlike for `&`, a disjunction cannot be pushed into - * a refined or applied type. Example: - * - * List[T] | List[U] is not the same as List[T | U]. - * - * The rhs is a proper supertype of the lhs. - */ - private def distributeOr(tp1: Type, tp2: Type): Type = tp1 match { - case ExprType(rt1) => - ExprType(rt1 | tp2.widenExpr) - case tp1: TypeVar if tp1.isInstantiated => - tp1.underlying | tp2 - case tp1: AnnotatedType => - tp1.underlying | tp2 - case _ => - NoType - } - - /** Show type, handling type types better than the default */ - private def showType(tp: Type)(implicit ctx: Context) = tp match { - case ClassInfo(_, cls, _, _, _) => cls.showLocated - case bounds: TypeBounds => "type bounds" + bounds.show - case _ => tp.show - } - - /** A comparison function to pick a winner in case of a merge conflict */ - private def isAsGood(tp1: Type, tp2: Type): Boolean = tp1 match { - case tp1: ClassInfo => - tp2 match { - case tp2: ClassInfo => - isSubTypeWhenFrozen(tp1.prefix, tp2.prefix) || (tp1.cls.owner derivesFrom tp2.cls.owner) - case _ => - false - } - case tp1: PolyType => - tp2 match { - case tp2: PolyType => - tp1.typeParams.length == tp2.typeParams.length && - isAsGood(tp1.resultType, tp2.resultType.subst(tp2, tp1)) - case _ => - false - } - case tp1: MethodType => - tp2 match { - case tp2: MethodType => - def asGoodParams(formals1: List[Type], formals2: List[Type]) = - (formals2 corresponds formals1)(isSubTypeWhenFrozen) - asGoodParams(tp1.paramTypes, tp2.paramTypes) && - (!asGoodParams(tp2.paramTypes, tp1.paramTypes) || - isAsGood(tp1.resultType, tp2.resultType)) - case _ => - false - } - case _ => - false - } - - /** A new type comparer of the same type as this one, using the given context. */ - def copyIn(ctx: Context) = new TypeComparer(ctx) - - // ----------- Diagnostics -------------------------------------------------- - - /** A hook for showing subtype traces. Overridden in ExplainingTypeComparer */ - def traceIndented[T](str: String)(op: => T): T = op - - private def traceInfo(tp1: Type, tp2: Type) = - s"${tp1.show} <:< ${tp2.show}" + { - if (ctx.settings.verbose.value || Config.verboseExplainSubtype) { - s" ${tp1.getClass}, ${tp2.getClass}" + - (if (frozenConstraint) " frozen" else "") + - (if (ctx.mode is Mode.TypevarsMissContext) " tvars-miss-ctx" else "") - } - else "" - } - - /** Show subtype goal that led to an assertion failure */ - def showGoal(tp1: Type, tp2: Type)(implicit ctx: Context) = { - println(ex"assertion failure for $tp1 <:< $tp2, frozen = $frozenConstraint") - def explainPoly(tp: Type) = tp match { - case tp: PolyParam => ctx.echo(s"polyparam ${tp.show} found in ${tp.binder.show}") - case tp: TypeRef if tp.symbol.exists => ctx.echo(s"typeref ${tp.show} found in ${tp.symbol.owner.show}") - case tp: TypeVar => ctx.echo(s"typevar ${tp.show}, origin = ${tp.origin}") - case _ => ctx.echo(s"${tp.show} is a ${tp.getClass}") - } - explainPoly(tp1) - explainPoly(tp2) - } - - /** Record statistics about the total number of subtype checks - * and the number of "successful" subtype checks, i.e. checks - * that form part of a subtype derivation tree that's ultimately successful. - */ - def recordStatistics(result: Boolean, prevSuccessCount: Int) = { - // Stats.record(s"isSubType ${tp1.show} <:< ${tp2.show}") - totalCount += 1 - if (result) successCount += 1 else successCount = prevSuccessCount - if (recCount == 0) { - Stats.record("successful subType", successCount) - Stats.record("total subType", totalCount) - successCount = 0 - totalCount = 0 - } - } -} - -object TypeComparer { - - /** Show trace of comparison operations when performing `op` as result string */ - def explained[T](op: Context => T)(implicit ctx: Context): String = { - val nestedCtx = ctx.fresh.setTypeComparerFn(new ExplainingTypeComparer(_)) - op(nestedCtx) - nestedCtx.typeComparer.toString - } -} - -/** A type comparer that can record traces of subtype operations */ -class ExplainingTypeComparer(initctx: Context) extends TypeComparer(initctx) { - private var indent = 0 - private val b = new StringBuilder - - private var skipped = false - - override def traceIndented[T](str: String)(op: => T): T = - if (skipped) op - else { - indent += 2 - b append "\n" append (" " * indent) append "==> " append str - val res = op - b append "\n" append (" " * indent) append "<== " append str append " = " append show(res) - indent -= 2 - res - } - - private def show(res: Any) = res match { - case res: printing.Showable if !ctx.settings.Yexplainlowlevel.value => res.show - case _ => String.valueOf(res) - } - - override def isSubType(tp1: Type, tp2: Type) = - traceIndented(s"${show(tp1)} <:< ${show(tp2)}${if (Config.verboseExplainSubtype) s" ${tp1.getClass} ${tp2.getClass}" else ""}${if (frozenConstraint) " frozen" else ""}") { - super.isSubType(tp1, tp2) - } - - override def hasMatchingMember(name: Name, tp1: Type, tp2: RefinedType): Boolean = - traceIndented(s"hasMatchingMember(${show(tp1)} . $name, ${show(tp2.refinedInfo)}), member = ${show(tp1.member(name).info)}") { - super.hasMatchingMember(name, tp1, tp2) - } - - override def lub(tp1: Type, tp2: Type) = - traceIndented(s"lub(${show(tp1)}, ${show(tp2)})") { - super.lub(tp1, tp2) - } - - override def glb(tp1: Type, tp2: Type) = - traceIndented(s"glb(${show(tp1)}, ${show(tp2)})") { - super.glb(tp1, tp2) - } - - override def addConstraint(param: PolyParam, bound: Type, fromBelow: Boolean): Boolean = - traceIndented(i"add constraint $param ${if (fromBelow) ">:" else "<:"} $bound $frozenConstraint, constraint = ${ctx.typerState.constraint}") { - super.addConstraint(param, bound, fromBelow) - } - - override def copyIn(ctx: Context) = new ExplainingTypeComparer(ctx) - - override def compareHkApply2(tp1: Type, tp2: HKApply, tycon2: Type, args2: List[Type]): Boolean = { - def addendum = "" - traceIndented(i"compareHkApply $tp1, $tp2$addendum") { - super.compareHkApply2(tp1, tp2, tycon2, args2) - } - } - - override def toString = "Subtype trace:" + { try b.toString finally b.clear() } -} |