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author | Adriaan Moors <adriaan.moors@typesafe.com> | 2016-02-10 11:46:15 -0800 |
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committer | Adriaan Moors <adriaan.moors@typesafe.com> | 2016-02-10 11:46:15 -0800 |
commit | da3f7177232e7c0732d5b7d2929dbb8271d7b395 (patch) | |
tree | 71b1f31626991ed3b9cd92af6bd6605588866f8c | |
parent | 78c378c97c51600cac1cf42edd050aceb2366026 (diff) | |
download | scala-da3f7177232e7c0732d5b7d2929dbb8271d7b395.tar.gz scala-da3f7177232e7c0732d5b7d2929dbb8271d7b395.tar.bz2 scala-da3f7177232e7c0732d5b7d2929dbb8271d7b395.zip |
Towards understanding `TypeRef`'s `transformInfo`/`baseType`
By reducing excessive factoring, we can save an extraneous call
to `asSeenFrom`, and hopefully in a following commit figure out
a bigger problem with `baseType` that is causing wrong subtyping results.
This commit is a pure refactoring, save for the dropped ASF call,
which is explained below.
To motivate the following change to `relativeInfo`:
```
private[Types] def relativeInfo = /*trace(s"relativeInfo(${safeToString}})")*/{
if (relativeInfoPeriod != currentPeriod) {
- val memberInfo = pre.memberInfo(sym)
- relativeInfoCache = transformInfo(memberInfo)
+ relativeInfoCache = memberInfoInstantiated
```
Let's consolidate the two removed line in this new method:
```
def memberInfoInstantiated = transformInfo(pre.memberInfo(sym))
```
To understand what `transformInfo` does, take these helpers spread over
various `*TypeRef` traits, and consolidate them:
```
- def asSeenFromOwner(tp: Type) = tp.asSeenFrom(pre, sym.owner)
// regular type refs:
- def transformInfo(tp: Type): Type = appliedType(asSeenFromOwner(tp), args)
// for no-args type refs:
- override def transformInfo(tp: Type): Type = appliedType(asSeenFromOwner(tp), dummyArgs)
```
By removing the dynamic dispatch, we get the following method
(given `require(args0 ne Nil, this)` in `ArgsTypeRef`,
and `args eq Nil` by construction in `NoArgsTypeRef` ):
```
def transformInfo(tp: Type) =
appliedType(tp.asSeenFrom(pre, sym.owner), if (args.isEmpty) dummyArgs else args)
```
Inlining `memberInfo`, which is defined as:
```
def memberInfo(sym: Symbol): Type = {
require(sym ne NoSymbol, this)
sym.info.asSeenFrom(this, sym.owner)
}
```
gives us:
```
def memberInfoInstantiated = transformInfo(sym.info.asSeenFrom(pre, sym.owner))
```
Inlining `transformInfo` as reworked above:
```
def memberInfoInstantiated =
appliedType(sym.info.asSeenFrom(pre, sym.owner).asSeenFrom(pre, sym.owner),
if (args.isEmpty) dummyArgs else args)
```
Whoops! One `asSeenFrom` should do...
```
+ final protected def memberInfoInstantiated: Type =
+ appliedType(sym.info.asSeenFrom(pre, sym.owner), if (args.isEmpty) dummyArgs else args)
```
-rw-r--r-- | src/reflect/scala/reflect/internal/Types.scala | 165 |
1 files changed, 71 insertions, 94 deletions
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala index e53b47e808..1b0251a642 100644 --- a/src/reflect/scala/reflect/internal/Types.scala +++ b/src/reflect/scala/reflect/internal/Types.scala @@ -462,7 +462,7 @@ trait Types * the empty list for all other types */ def boundSyms: immutable.Set[Symbol] = emptySymbolSet - /** Replace formal type parameter symbols with actual type arguments. + /** Replace formal type parameter symbols with actual type arguments. ErrorType on arity mismatch. * * Amounts to substitution except for higher-kinded types. (See overridden method in TypeRef) -- @M */ @@ -1867,53 +1867,13 @@ trait Types override def isHigherKinded = false override def typeParams = Nil - override def transform(tp: Type): Type = { - // This situation arises when a typevar is encountered for which - // too little information is known to determine its kind, and - // it later turns out not to have kind *. See SI-4070. Only - // logging it for now. - val tparams = sym.typeParams - if (tparams.size != args.size) - devWarning(s"$this.transform($tp), but tparams.isEmpty and args=$args") - def asSeenFromInstantiated(tp: Type) = - asSeenFromOwner(tp).instantiateTypeParams(tparams, args) - // If we're called with a poly type, and we were to run the `asSeenFrom`, over the entire - // type, we can end up with new symbols for the type parameters (clones from TypeMap). - // The subsequent substitution of type arguments would fail. This problem showed up during - // the fix for SI-8046, however the solution taken there wasn't quite right, and led to - // SI-8170. - // - // Now, we detect the PolyType before both the ASF *and* the substitution, and just operate - // on the result type. - // - // TODO: Revisit this and explore the questions raised: - // - // AM: I like this better than the old code, but is there any way the tparams would need the ASF treatment as well? - // JZ: I think its largely irrelevant, as they are no longer referred to in the result type. - // In fact, you can get away with returning a type of kind * here and the sky doesn't fall: - // `case PolyType(`tparams`, result) => asSeenFromInstantiated(result)` - // But I thought it was better to retain the kind. - // AM: I've been experimenting with apply-type-args-then-ASF, but running into cycles. - // In general, it seems iffy the tparams can never occur in the result - // then we might as well represent the type as a no-arg typeref. - // AM: I've also been trying to track down uses of transform (pretty generic name for something that - // does not seem that widely applicable). - // It's kind of a helper for computing baseType (since it tries to propagate our type args to some - // other type, which has to be related to this type for that to make sense). - // - tp match { - case PolyType(`tparams`, result) => PolyType(tparams, asSeenFromInstantiated(result)) - case _ => asSeenFromInstantiated(tp) - } - } - // note: does not go through typeRef. There's no need to because // neither `pre` nor `sym` changes. And there's a performance // advantage to call TypeRef directly. override def typeConstructor = TypeRef(pre, sym, Nil) } - class ModuleTypeRef(pre0: Type, sym0: Symbol) extends NoArgsTypeRef(pre0, sym0) with ClassTypeRef { + class ModuleTypeRef(pre0: Type, sym0: Symbol) extends NoArgsTypeRef(pre0, sym0) { require(sym.isModuleClass, sym) private[this] var narrowedCache: Type = _ override def narrow = { @@ -1935,7 +1895,7 @@ trait Types require(sym.isPackageClass, sym) override protected def finishPrefix(rest: String) = packagePrefix + rest } - class RefinementTypeRef(pre0: Type, sym0: Symbol) extends NoArgsTypeRef(pre0, sym0) with ClassTypeRef { + class RefinementTypeRef(pre0: Type, sym0: Symbol) extends NoArgsTypeRef(pre0, sym0) { require(sym.isRefinementClass, sym) // I think this is okay, but see #1241 (r12414), #2208, and typedTypeConstructor in Typers @@ -1951,7 +1911,6 @@ trait Types // represented as existential types. override def isHigherKinded = (typeParams ne Nil) override def typeParams = if (isDefinitionsInitialized) sym.typeParams else sym.unsafeTypeParams - private def isRaw = !phase.erasedTypes && isRawIfWithoutArgs(sym) override def instantiateTypeParams(formals: List[Symbol], actuals: List[Type]): Type = if (isHigherKinded) { @@ -1964,17 +1923,6 @@ trait Types else super.instantiateTypeParams(formals, actuals) - override def transform(tp: Type): Type = { - val res = asSeenFromOwner(tp) - if (isHigherKinded && !isRaw) - res.instantiateTypeParams(typeParams, dummyArgs) - else - res - } - - override def transformInfo(tp: Type): Type = - appliedType(asSeenFromOwner(tp), dummyArgs) - override def narrow = if (sym.isModuleClass) singleType(pre, sym.sourceModule) else super.narrow @@ -1986,15 +1934,6 @@ trait Types if (isHigherKinded) etaExpand else super.normalizeImpl } - trait ClassTypeRef extends TypeRef { - // !!! There are scaladoc-created symbols arriving which violate this require. - // require(sym.isClass, sym) - - override def baseType(clazz: Symbol): Type = - if (sym == clazz) this - else transform(sym.info.baseType(clazz)) - } - trait NonClassTypeRef extends TypeRef { require(sym.isNonClassType, sym) @@ -2011,32 +1950,11 @@ trait Types private[Types] def relativeInfo = /*trace(s"relativeInfo(${safeToString}})")*/{ if (relativeInfoPeriod != currentPeriod) { - val memberInfo = pre.memberInfo(sym) - relativeInfoCache = transformInfo(memberInfo) + relativeInfoCache = memberInfoInstantiated relativeInfoPeriod = currentPeriod } relativeInfoCache } - - override def baseType(clazz: Symbol): Type = - if (sym == clazz) this else baseTypeOfNonClassTypeRef(this, clazz) - } - - protected def baseTypeOfNonClassTypeRef(tpe: NonClassTypeRef, clazz: Symbol) = try { - basetypeRecursions += 1 - if (basetypeRecursions < LogPendingBaseTypesThreshold) - tpe.relativeInfo.baseType(clazz) - else if (pendingBaseTypes contains tpe) - if (clazz == AnyClass) clazz.tpe else NoType - else - try { - pendingBaseTypes += tpe - tpe.relativeInfo.baseType(clazz) - } finally { - pendingBaseTypes -= tpe - } - } finally { - basetypeRecursions -= 1 } trait AliasTypeRef extends NonClassTypeRef { @@ -2130,7 +2048,7 @@ trait Types val symInfo = sym.info if (thisInfoCache == null || (symInfo ne symInfoCache)) { symInfoCache = symInfo - thisInfoCache = transformInfo(symInfo) match { + thisInfoCache = memberInfoInstantiated match { // If a subtyping cycle is not detected here, we'll likely enter an infinite // loop before a sensible error can be issued. SI-5093 is one example. case x: SubType if x.supertype eq this => @@ -2193,7 +2111,70 @@ trait Types // formal type parameters with actual ones. If tp is higher kinded, // the "actual" type arguments are types that simply reference the // corresponding type parameters (unbound type variables) - def transform(tp: Type): Type + final def transform(tp: Type): Type = + if (args.isEmpty) { + if (isHigherKinded && (phase.erasedTypes || !isRawIfWithoutArgs(sym))) + tp.asSeenFrom(pre, sym.owner).instantiateTypeParams(typeParams, dummyArgs) + else + tp.asSeenFrom(pre, sym.owner) + } else { + // This situation arises when a typevar is encountered for which + // too little information is known to determine its kind, and + // it later turns out not to have kind *. See SI-4070. Only + // logging it for now. + val tparams = sym.typeParams + if (!sameLength(tparams, args)) devWarning(s"$this.transform($tp), but tparams.isEmpty and args=$args") + + // If we're called with a poly type, and we were to run the `asSeenFrom`, over the entire + // type, we can end up with new symbols for the type parameters (clones from TypeMap). + // The subsequent substitution of type arguments would fail. This problem showed up during + // the fix for SI-8046, however the solution taken there wasn't quite right, and led to + // SI-8170. + // + // Now, we detect the PolyType before both the ASF *and* the substitution, and just operate + // on the result type. + // + // TODO: Revisit this and explore the questions raised: + // + // AM: I like this better than the old code, but is there any way the tparams would need the ASF treatment as well? + // JZ: I think its largely irrelevant, as they are no longer referred to in the result type. + // In fact, you can get away with returning a type of kind * here and the sky doesn't fall: + // `case PolyType(`tparams`, result) => asSeenFromInstantiated(result)` + // But I thought it was better to retain the kind. + // AM: I've been experimenting with apply-type-args-then-ASF, but running into cycles. + // In general, it seems iffy the tparams can never occur in the result + // then we might as well represent the type as a no-arg typeref. + // AM: I've also been trying to track down uses of transform (pretty generic name for something that + // does not seem that widely applicable). + // It's kind of a helper for computing baseType (since it tries to propagate our type args to some + // other type, which has to be related to this type for that to make sense). + // + tp match { + case PolyType(`tparams`, result) => PolyType(tparams, result.asSeenFrom(pre, sym.owner).instantiateTypeParams(tparams, args)) + case _ => tp.asSeenFrom(pre, sym.owner).instantiateTypeParams(tparams, args) + } + } + + final override def baseType(clazz: Symbol): Type = + if (sym == clazz) this + else if (sym.isClass) transform(sym.info.baseType(clazz)) + else baseTypeOfNonClassTypeRef(clazz) + + //@M! use appliedType on the polytype that represents the bounds (or if aliastype, the rhs) + final protected def memberInfoInstantiated: Type = + appliedType(sym.info.asSeenFrom(pre, sym.owner), if (args.isEmpty) dummyArgs else args) + + private def baseTypeOfNonClassTypeRef(clazz: Symbol) = + try { + basetypeRecursions += 1 + if (basetypeRecursions >= LogPendingBaseTypesThreshold) baseTypeOfNonClassTypeRefLogged(clazz) + else memberInfoInstantiated.baseType(clazz) + } finally basetypeRecursions -= 1 + + private def baseTypeOfNonClassTypeRefLogged(clazz: Symbol) = + if (pendingBaseTypes add this) try memberInfoInstantiated.baseType(clazz) finally pendingBaseTypes -= this + else if (clazz == AnyClass) clazz.tpe + else NoType // eta-expand, subtyping relies on eta-expansion of higher-kinded types protected def normalizeImpl: Type = if (isHigherKinded) etaExpand else super.normalize @@ -2226,13 +2207,9 @@ trait Types // (they are allowed to be rebound more liberally) def coevolveSym(pre1: Type): Symbol = sym - //@M! use appliedType on the polytype that represents the bounds (or if aliastype, the rhs) - def transformInfo(tp: Type): Type = appliedType(asSeenFromOwner(tp), args) - def thisInfo = sym.info def initializedTypeParams = sym.info.typeParams def typeParamsMatchArgs = sameLength(initializedTypeParams, args) - def asSeenFromOwner(tp: Type) = tp.asSeenFrom(pre, sym.owner) override def baseClasses = thisInfo.baseClasses override def baseTypeSeqDepth = baseTypeSeq.maxDepth @@ -2363,10 +2340,10 @@ trait Types // No longer defined as anonymous classes in `object TypeRef` to avoid an unnecessary outer pointer. private final class AliasArgsTypeRef(pre: Type, sym: Symbol, args: List[Type]) extends ArgsTypeRef(pre, sym, args) with AliasTypeRef private final class AbstractArgsTypeRef(pre: Type, sym: Symbol, args: List[Type]) extends ArgsTypeRef(pre, sym, args) with AbstractTypeRef - private final class ClassArgsTypeRef(pre: Type, sym: Symbol, args: List[Type]) extends ArgsTypeRef(pre, sym, args) with ClassTypeRef + private final class ClassArgsTypeRef(pre: Type, sym: Symbol, args: List[Type]) extends ArgsTypeRef(pre, sym, args) private final class AliasNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym) with AliasTypeRef private final class AbstractNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym) with AbstractTypeRef - private final class ClassNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym) with ClassTypeRef + private final class ClassNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym) object TypeRef extends TypeRefExtractor { def apply(pre: Type, sym: Symbol, args: List[Type]): Type = unique({ |