Scala example source code file (GlbLubs.scala)
The GlbLubs.scala Scala example source code
package scala
package reflect
package internal
package tpe
import scala.collection.mutable
import scala.annotation.tailrec
import util.Statistics
import Variance._
private[internal] trait GlbLubs {
self: SymbolTable =>
import definitions._
import TypesStats._
private final val printLubs = scala.sys.props contains "scalac.debug.lub"
private final val strictInference = settings.strictInference
/** In case anyone wants to turn off lub verification without reverting anything. */
private final val verifyLubs = true
private def printLubMatrix(btsMap: Map[Type, List[Type]], depth: Depth) {
import util.TableDef
import TableDef.Column
def str(tp: Type) = {
if (tp == NoType) ""
else {
val s = ("" + tp).replaceAll("""[\w.]+\.(\w+)""", "$1")
if (s.length < 60) s
else (s take 57) + "..."
}
}
val sorted = btsMap.toList.sortWith((x, y) => x._1.typeSymbol isLess y._1.typeSymbol)
val maxSeqLength = sorted.map(_._2.size).max
val padded = sorted map (_._2.padTo(maxSeqLength, NoType))
val transposed = padded.transpose
val columns: List[Column[List[Type]]] = mapWithIndex(sorted) {
case ((k, v), idx) =>
Column(str(k), (xs: List[Type]) => str(xs(idx)), left = true)
}
val tableDef = TableDef(columns: _*)
val formatted = tableDef.table(transposed)
println("** Depth is " + depth + "\n" + formatted)
}
/** From a list of types, find any which take type parameters
* where the type parameter bounds contain references to other
* any types in the list (including itself.)
*
* @return List of symbol pairs holding the recursive type
* parameter and the parameter which references it.
*/
def findRecursiveBounds(ts: List[Type]): List[(Symbol, Symbol)] = {
if (ts.isEmpty) Nil
else {
val sym = ts.head.typeSymbol
require(ts.tail forall (_.typeSymbol == sym), ts)
for (p <- sym.typeParams ; in <- sym.typeParams ; if in.info.bounds contains p) yield
p -> in
}
}
// only called when strictInference
private def willViolateRecursiveBounds(tp: Type, ts: List[Type], tsElimSub: List[Type]) = {
val typeSym = ts.head.typeSymbol // we're uniform, the `.head` is as good as any.
def fbounds = findRecursiveBounds(ts) map (_._2)
def isRecursive = typeSym.typeParams exists fbounds.contains
isRecursive && (transposeSafe(tsElimSub map (_.normalize.typeArgs)) match {
case Some(arggsTransposed) =>
val mergedTypeArgs = (tp match { case et: ExistentialType => et.underlying; case _ => tp}).typeArgs
exists3(typeSym.typeParams, mergedTypeArgs, arggsTransposed) {
(param, arg, lubbedArgs) =>
val isExistential = arg.typeSymbol.isExistentiallyBound
val isInFBound = fbounds contains param
val wasLubbed = !lubbedArgs.exists(_ =:= arg)
(!isExistential && isInFBound && wasLubbed)
}
case None => false
})
}
/** Given a matrix `tsBts` whose columns are basetype sequences (and the symbols `tsParams` that should be interpreted as type parameters in this matrix),
* compute its least sorted upwards closed upper bound relative to the following ordering <= between lists of types:
*
* xs <= ys iff forall y in ys exists x in xs such that x <: y
*
* @arg tsParams for each type in the original list of types `ts0`, its list of type parameters (if that type is a type constructor)
* (these type parameters may be referred to by type arguments in the BTS column of those types,
* and must be interpreted as bound variables; i.e., under a type lambda that wraps the types that refer to these type params)
* @arg tsBts a matrix whose columns are basetype sequences
* the first row is the original list of types for which we're computing the lub
* (except that type constructors have been applied to their dummyArgs)
* @See baseTypeSeq for a definition of sorted and upwards closed.
*/
def lubList(ts: List[Type], depth: Depth): List[Type] = {
var lubListDepth = Depth.Zero
// This catches some recursive situations which would otherwise
// befuddle us, e.g. pos/hklub0.scala
def isHotForTs(xs: List[Type]) = ts exists (_.typeParams == xs.map(_.typeSymbol))
def elimHigherOrderTypeParam(tp: Type) = tp match {
case TypeRef(_, _, args) if args.nonEmpty && isHotForTs(args) =>
logResult("Retracting dummies from " + tp + " in lublist")(tp.typeConstructor)
case _ => tp
}
// pretypes is a tail-recursion-preserving accumulator.
@tailrec
def loop(pretypes: List[Type], tsBts: List[List[Type]]): List[Type] = {
lubListDepth = lubListDepth.incr
if (tsBts.isEmpty || (tsBts exists typeListIsEmpty)) pretypes.reverse
else if (tsBts.tail.isEmpty) pretypes.reverse ++ tsBts.head
else {
// ts0 is the 1-dimensional frontier of symbols cutting through 2-dimensional tsBts.
// Invariant: all symbols "under" (closer to the first row) the frontier
// are smaller (according to _.isLess) than the ones "on and beyond" the frontier
val ts0 = tsBts map (_.head)
// Is the frontier made up of types with the same symbol?
val isUniformFrontier = (ts0: @unchecked) match {
case t :: ts => ts forall (_.typeSymbol == t.typeSymbol)
}
// Produce a single type for this frontier by merging the prefixes and arguments of those
// typerefs that share the same symbol: that symbol is the current maximal symbol for which
// the invariant holds, i.e., the one that conveys most information regarding subtyping. Before
// merging, strip targs that refer to bound tparams (when we're computing the lub of type
// constructors.) Also filter out all types that are a subtype of some other type.
if (isUniformFrontier) {
val tails = tsBts map (_.tail)
val ts1 = elimSub(ts0, depth) map elimHigherOrderTypeParam
mergePrefixAndArgs(ts1, Covariant, depth) match {
case NoType => loop(pretypes, tails)
case tp if strictInference && willViolateRecursiveBounds(tp, ts0, ts1) =>
log(s"Breaking recursion in lublist, advancing frontier and discaring merged prefix/args from $tp")
loop(pretypes, tails)
case tp =>
loop(tp :: pretypes, tails)
}
} else {
// frontier is not uniform yet, move it beyond the current minimal symbol;
// lather, rinse, repeat
val sym = minSym(ts0)
val newtps = tsBts map (ts => if (ts.head.typeSymbol == sym) ts.tail else ts)
if (printLubs) {
val str = (newtps.zipWithIndex map { case (tps, idx) =>
tps.map(" " + _ + "\n").mkString(" (" + idx + ")\n", "", "\n")
}).mkString("")
println("Frontier(\n" + str + ")")
printLubMatrix((ts zip tsBts).toMap, lubListDepth)
}
loop(pretypes, newtps)
}
}
}
val initialBTSes = ts map (_.baseTypeSeq.toList)
if (printLubs)
printLubMatrix((ts zip initialBTSes).toMap, depth)
loop(Nil, initialBTSes)
}
/** The minimal symbol of a list of types (as determined by `Symbol.isLess`). */
private def minSym(tps: List[Type]): Symbol =
(tps.head.typeSymbol /: tps.tail) {
(sym1, tp2) => if (tp2.typeSymbol isLess sym1) tp2.typeSymbol else sym1
}
/** A minimal type list which has a given list of types as its base type sequence */
def spanningTypes(ts: List[Type]): List[Type] = ts match {
case List() => List()
case first :: rest =>
first :: spanningTypes(
rest filter (t => !first.typeSymbol.isSubClass(t.typeSymbol)))
}
/** Eliminate from list of types all elements which are a supertype
* of some other element of the list. */
private def elimSuper(ts: List[Type]): List[Type] = ts match {
case List() => List()
case List(t) => List(t)
case t :: ts1 =>
val rest = elimSuper(ts1 filter (t1 => !(t <:< t1)))
if (rest exists (t1 => t1 <:< t)) rest else t :: rest
}
/** Eliminate from list of types all elements which are a subtype
* of some other element of the list. */
private def elimSub(ts: List[Type], depth: Depth): List[Type] = {
def elimSub0(ts: List[Type]): List[Type] = ts match {
case List() => List()
case List(t) => List(t)
case t :: ts1 =>
val rest = elimSub0(ts1 filter (t1 => !isSubType(t1, t, depth.decr)))
if (rest exists (t1 => isSubType(t, t1, depth.decr))) rest else t :: rest
}
val ts0 = elimSub0(ts)
if (ts0.isEmpty || ts0.tail.isEmpty) ts0
else {
val ts1 = ts0 mapConserve (t => elimAnonymousClass(t.dealiasWiden))
if (ts1 eq ts0) ts0
else elimSub(ts1, depth)
}
}
private def stripExistentialsAndTypeVars(ts: List[Type]): (List[Type], List[Symbol]) = {
val quantified = ts flatMap {
case ExistentialType(qs, _) => qs
case t => List()
}
def stripType(tp: Type): Type = tp match {
case ExistentialType(_, res) =>
res
case tv@TypeVar(_, constr) =>
if (tv.instValid) stripType(constr.inst)
else if (tv.untouchable) tv
else abort("trying to do lub/glb of typevar "+tp)
case t => t
}
val strippedTypes = ts mapConserve stripType
(strippedTypes, quantified)
}
/** Does this set of types have the same weak lub as
* it does regular lub? This is exposed so lub callers
* can discover whether the trees they are typing will
* may require further adaptation. It may return false
* negatives, but it will not return false positives.
*/
def sameWeakLubAsLub(tps: List[Type]) = tps match {
case Nil => true
case tp :: Nil => !typeHasAnnotations(tp)
case tps => !(tps exists typeHasAnnotations) && !(tps forall isNumericValueType)
}
/** If the arguments are all numeric value types, the numeric
* lub according to the weak conformance spec. If any argument
* has type annotations, take the lub of the unannotated type
* and call the analyzerPlugin method annotationsLub so it can
* be further altered. Otherwise, the regular lub.
*/
def weakLub(tps: List[Type]): Type = (
if (tps.isEmpty)
NothingTpe
else if (tps forall isNumericValueType)
numericLub(tps)
else if (tps exists typeHasAnnotations)
annotationsLub(lub(tps map (_.withoutAnnotations)), tps)
else
lub(tps)
)
def numericLub(ts: List[Type]) =
ts reduceLeft ((t1, t2) =>
if (isNumericSubType(t1, t2)) t2
else if (isNumericSubType(t2, t1)) t1
else IntTpe)
private val _lubResults = new mutable.HashMap[(Depth, List[Type]), Type]
def lubResults = _lubResults
private val _glbResults = new mutable.HashMap[(Depth, List[Type]), Type]
def glbResults = _glbResults
def lub(ts: List[Type]): Type = ts match {
case Nil => NothingTpe
case t :: Nil => t
case _ =>
if (Statistics.canEnable) Statistics.incCounter(lubCount)
val start = if (Statistics.canEnable) Statistics.pushTimer(typeOpsStack, lubNanos) else null
try {
val res = lub(ts, lubDepth(ts))
// If the number of unapplied type parameters in all incoming
// types is consistent, and the lub does not match that, return
// the type constructor of the calculated lub instead. This
// is because lubbing type constructors tends to result in types
// which have been applied to dummies or Nothing.
ts.map(_.typeParams.size).distinct match {
case x :: Nil if res.typeParams.size != x =>
logResult(s"Stripping type args from lub because $res is not consistent with $ts")(res.typeConstructor)
case _ =>
res
}
}
finally {
lubResults.clear()
glbResults.clear()
if (Statistics.canEnable) Statistics.popTimer(typeOpsStack, start)
}
}
/** The least upper bound wrt <:< of a list of types */
protected[internal] def lub(ts: List[Type], depth: Depth): Type = {
def lub0(ts0: List[Type]): Type = elimSub(ts0, depth) match {
case List() => NothingTpe
case List(t) => t
case ts @ PolyType(tparams, _) :: _ =>
val tparams1 = map2(tparams, matchingBounds(ts, tparams).transpose)((tparam, bounds) =>
tparam.cloneSymbol.setInfo(glb(bounds, depth)))
PolyType(tparams1, lub0(matchingInstTypes(ts, tparams1)))
case ts @ (mt @ MethodType(params, _)) :: rest =>
MethodType(params, lub0(matchingRestypes(ts, mt.paramTypes)))
case ts @ NullaryMethodType(_) :: rest =>
NullaryMethodType(lub0(matchingRestypes(ts, Nil)))
case ts @ TypeBounds(_, _) :: rest =>
TypeBounds(glb(ts map (_.bounds.lo), depth), lub(ts map (_.bounds.hi), depth))
case ts @ AnnotatedType(annots, tpe) :: rest =>
annotationsLub(lub0(ts map (_.withoutAnnotations)), ts)
case ts =>
lubResults get ((depth, ts)) match {
case Some(lubType) =>
lubType
case None =>
lubResults((depth, ts)) = AnyTpe
val res = if (depth.isNegative) AnyTpe else lub1(ts)
lubResults((depth, ts)) = res
res
}
}
def lub1(ts0: List[Type]): Type = {
val (ts, tparams) = stripExistentialsAndTypeVars(ts0)
val lubBaseTypes: List[Type] = lubList(ts, depth)
val lubParents = spanningTypes(lubBaseTypes)
val lubOwner = commonOwner(ts)
val lubBase = intersectionType(lubParents, lubOwner)
val lubType =
if (phase.erasedTypes || depth.isZero ) lubBase
else {
val lubRefined = refinedType(lubParents, lubOwner)
val lubThisType = lubRefined.typeSymbol.thisType
val narrowts = ts map (_.narrow)
def excludeFromLub(sym: Symbol) = (
sym.isClass
|| sym.isConstructor
|| !sym.isPublic
|| isGetClass(sym)
|| sym.isFinal
|| narrowts.exists(t => !refines(t, sym))
)
def lubsym(proto: Symbol): Symbol = {
val prototp = lubThisType.memberInfo(proto)
val syms = narrowts map (t =>
t.nonPrivateMember(proto.name).suchThat(sym =>
sym.tpe matches prototp.substThis(lubThisType.typeSymbol, t)))
if (syms contains NoSymbol) NoSymbol
else {
val symtypes =
map2(narrowts, syms)((t, sym) => t.memberInfo(sym).substThis(t.typeSymbol, lubThisType))
if (proto.isTerm) // possible problem: owner of info is still the old one, instead of new refinement class
proto.cloneSymbol(lubRefined.typeSymbol).setInfoOwnerAdjusted(lub(symtypes, depth.decr))
else if (symtypes.tail forall (symtypes.head =:= _))
proto.cloneSymbol(lubRefined.typeSymbol).setInfoOwnerAdjusted(symtypes.head)
else {
def lubBounds(bnds: List[TypeBounds]): TypeBounds =
TypeBounds(glb(bnds map (_.lo), depth.decr), lub(bnds map (_.hi), depth.decr))
lubRefined.typeSymbol.newAbstractType(proto.name.toTypeName, proto.pos)
.setInfoOwnerAdjusted(lubBounds(symtypes map (_.bounds)))
}
}
}
def refines(tp: Type, sym: Symbol): Boolean = {
val syms = tp.nonPrivateMember(sym.name).alternatives
!syms.isEmpty && (syms forall (alt =>
// todo alt != sym is strictly speaking not correct, but without it we lose
// efficiency.
alt != sym && !specializesSym(lubThisType, sym, tp, alt, depth)))
}
// add a refinement symbol for all non-class members of lubBase
// which are refined by every type in ts.
for (sym <- lubBase.nonPrivateMembers ; if !excludeFromLub(sym)) {
try lubsym(sym) andAlso (addMember(lubThisType, lubRefined, _, depth))
catch {
case ex: NoCommonType =>
}
}
if (lubRefined.decls.isEmpty) lubBase
else if (!verifyLubs) lubRefined
else {
// Verify that every given type conforms to the calculated lub.
// In theory this should not be necessary, but higher-order type
// parameters are not handled correctly.
val ok = ts forall { t =>
isSubType(t, lubRefined, depth) || {
if (settings.debug || printLubs) {
Console.println(
"Malformed lub: " + lubRefined + "\n" +
"Argument " + t + " does not conform. Falling back to " + lubBase
)
}
false
}
}
// If not, fall back on the more conservative calculation.
if (ok) lubRefined
else lubBase
}
}
// dropIllegalStarTypes is a localized fix for SI-6897. We should probably
// integrate that transformation at a lower level in master, but lubs are
// the likely and maybe only spot they escape, so fixing here for 2.10.1.
existentialAbstraction(tparams, dropIllegalStarTypes(lubType))
}
if (printLubs) {
println(indent + "lub of " + ts + " at depth "+depth)//debug
indent = indent + " "
assert(indent.length <= 100)
}
if (Statistics.canEnable) Statistics.incCounter(nestedLubCount)
val res = lub0(ts)
if (printLubs) {
indent = indent stripSuffix " "
println(indent + "lub of " + ts + " is " + res)//debug
}
res
}
val GlbFailure = new Throwable
/** A global counter for glb calls in the `specializes` query connected to the `addMembers`
* call in `glb`. There's a possible infinite recursion when `specializes` calls
* memberType, which calls baseTypeSeq, which calls mergePrefixAndArgs, which calls glb.
* The counter breaks this recursion after two calls.
* If the recursion is broken, no member is added to the glb.
*/
private var globalGlbDepth = Depth.Zero
private final val globalGlbLimit = Depth(2)
/** The greatest lower bound of a list of types (as determined by `<:<`). */
def glb(ts: List[Type]): Type = elimSuper(ts) match {
case List() => AnyTpe
case List(t) => t
case ts0 =>
if (Statistics.canEnable) Statistics.incCounter(lubCount)
val start = if (Statistics.canEnable) Statistics.pushTimer(typeOpsStack, lubNanos) else null
try {
glbNorm(ts0, lubDepth(ts0))
} finally {
lubResults.clear()
glbResults.clear()
if (Statistics.canEnable) Statistics.popTimer(typeOpsStack, start)
}
}
protected[internal] def glb(ts: List[Type], depth: Depth): Type = elimSuper(ts) match {
case List() => AnyTpe
case List(t) => t
case ts0 => glbNorm(ts0, depth)
}
/** The greatest lower bound of a list of types (as determined by `<:<`), which have been normalized
* with regard to `elimSuper`. */
protected def glbNorm(ts: List[Type], depth: Depth): Type = {
def glb0(ts0: List[Type]): Type = ts0 match {
case List() => AnyTpe
case List(t) => t
case ts @ PolyType(tparams, _) :: _ =>
val tparams1 = map2(tparams, matchingBounds(ts, tparams).transpose)((tparam, bounds) =>
tparam.cloneSymbol.setInfo(lub(bounds, depth)))
PolyType(tparams1, glbNorm(matchingInstTypes(ts, tparams1), depth))
case ts @ (mt @ MethodType(params, _)) :: rest =>
MethodType(params, glbNorm(matchingRestypes(ts, mt.paramTypes), depth))
case ts @ NullaryMethodType(_) :: rest =>
NullaryMethodType(glbNorm(matchingRestypes(ts, Nil), depth))
case ts @ TypeBounds(_, _) :: rest =>
TypeBounds(lub(ts map (_.bounds.lo), depth), glb(ts map (_.bounds.hi), depth))
case ts =>
glbResults get ((depth, ts)) match {
case Some(glbType) =>
glbType
case _ =>
glbResults((depth, ts)) = NothingTpe
val res = if (depth.isNegative) NothingTpe else glb1(ts)
glbResults((depth, ts)) = res
res
}
}
def glb1(ts0: List[Type]): Type = {
try {
val (ts, tparams) = stripExistentialsAndTypeVars(ts0)
val glbOwner = commonOwner(ts)
def refinedToParents(t: Type): List[Type] = t match {
case RefinedType(ps, _) => ps flatMap refinedToParents
case _ => List(t)
}
def refinedToDecls(t: Type): List[Scope] = t match {
case RefinedType(ps, decls) =>
val dss = ps flatMap refinedToDecls
if (decls.isEmpty) dss else decls :: dss
case _ => List()
}
val ts1 = ts flatMap refinedToParents
val glbBase = intersectionType(ts1, glbOwner)
val glbType =
if (phase.erasedTypes || depth.isZero) glbBase
else {
val glbRefined = refinedType(ts1, glbOwner)
val glbThisType = glbRefined.typeSymbol.thisType
def glbsym(proto: Symbol): Symbol = {
val prototp = glbThisType.memberInfo(proto)
val syms = for (t <- ts;
alt <- (t.nonPrivateMember(proto.name).alternatives)
if glbThisType.memberInfo(alt) matches prototp
) yield alt
val symtypes = syms map glbThisType.memberInfo
assert(!symtypes.isEmpty)
proto.cloneSymbol(glbRefined.typeSymbol).setInfoOwnerAdjusted(
if (proto.isTerm) glb(symtypes, depth.decr)
else {
def isTypeBound(tp: Type) = tp match {
case TypeBounds(_, _) => true
case _ => false
}
def glbBounds(bnds: List[Type]): TypeBounds = {
val lo = lub(bnds map (_.bounds.lo), depth.decr)
val hi = glb(bnds map (_.bounds.hi), depth.decr)
if (lo <:< hi) TypeBounds(lo, hi)
else throw GlbFailure
}
val symbounds = symtypes filter isTypeBound
var result: Type =
if (symbounds.isEmpty)
TypeBounds.empty
else glbBounds(symbounds)
for (t <- symtypes if !isTypeBound(t))
if (result.bounds containsType t) result = t
else throw GlbFailure
result
})
}
if (globalGlbDepth < globalGlbLimit)
try {
globalGlbDepth = globalGlbDepth.incr
val dss = ts flatMap refinedToDecls
for (ds <- dss; sym <- ds.iterator)
if (globalGlbDepth < globalGlbLimit && !specializesSym(glbThisType, sym, depth))
try {
addMember(glbThisType, glbRefined, glbsym(sym), depth)
} catch {
case ex: NoCommonType =>
}
} finally {
globalGlbDepth = globalGlbDepth.decr
}
if (glbRefined.decls.isEmpty) glbBase else glbRefined
}
existentialAbstraction(tparams, glbType)
} catch {
case GlbFailure =>
if (ts forall (t => NullTpe <:< t)) NullTpe
else NothingTpe
}
}
// if (settings.debug.value) { println(indent + "glb of " + ts + " at depth "+depth); indent = indent + " " } //DEBUG
if (Statistics.canEnable) Statistics.incCounter(nestedLubCount)
glb0(ts)
// if (settings.debug.value) { indent = indent.substring(0, indent.length() - 2); log(indent + "glb of " + ts + " is " + res) }//DEBUG
}
/** All types in list must be polytypes with type parameter lists of
* same length as tparams.
* Returns list of list of bounds infos, where corresponding type
* parameters are renamed to tparams.
*/
private def matchingBounds(tps: List[Type], tparams: List[Symbol]): List[List[Type]] = {
def getBounds(tp: Type): List[Type] = tp match {
case PolyType(tparams1, _) if sameLength(tparams1, tparams) =>
tparams1 map (tparam => tparam.info.substSym(tparams1, tparams))
case tp =>
if (tp ne tp.normalize) getBounds(tp.normalize)
else throw new NoCommonType(tps)
}
tps map getBounds
}
/** All types in list must be polytypes with type parameter lists of
* same length as tparams.
* Returns list of instance types, where corresponding type
* parameters are renamed to tparams.
*/
private def matchingInstTypes(tps: List[Type], tparams: List[Symbol]): List[Type] = {
def transformResultType(tp: Type): Type = tp match {
case PolyType(tparams1, restpe) if sameLength(tparams1, tparams) =>
restpe.substSym(tparams1, tparams)
case tp =>
if (tp ne tp.normalize) transformResultType(tp.normalize)
else throw new NoCommonType(tps)
}
tps map transformResultType
}
/** All types in list must be method types with equal parameter types.
* Returns list of their result types.
*/
private def matchingRestypes(tps: List[Type], pts: List[Type]): List[Type] =
tps map {
case mt @ MethodType(params1, res) if isSameTypes(mt.paramTypes, pts) =>
res
case NullaryMethodType(res) if pts.isEmpty =>
res
case _ =>
throw new NoCommonType(tps)
}
}
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