package dotty.tools
package dotc
package core
import SymDenotations.{ SymDenotation, NoDenotation }
import Contexts.{Context, ContextBase}
import Names.Name
import Names.TypeName
import Symbols.NoSymbol
import Symbols._
import Types._, Periods._, Flags._, Transformers._
import io.AbstractFile
import Decorators.SymbolIteratorDecorator
/** Denotations represent the meaning of symbols and named types.
* The following diagram shows how the principal types of denotations
* and their denoting entities relate to each other. Lines ending in
* a down-arrow `v` are member methods. The two methods shown in the diagram are
* "symbol" and "deref". Both methods are parameterized by the current context,
* and are effectively indexed by current period.
*
* Lines ending in a horizontal line mean subtying (right is a subtype of left).
*
* NamedType------NamedTypeWithSignature
*
* | | Symbol---------ClassSymbol
* | | | |
* | denot | denot | denot | denot
* v v v v
* Denotation-+-----SingleDenotation-+------SymDenotation-+----ClassDenotation
* | |
* +-----MultiDenotation |
* |
* +--UniqueRefDenotation
* +--JointRefDenotation
*
* Here's a short summary of the classes in this diagram.
*
* NamedType A type consisting of a prefix type and a name, with fields
* prefix: Type
* name: Name
* NamedTypeWithSignature A named type that has in addition a signature to select an overloaded variant, with new field
* signature: Signature
* Symbol A label for a definition or declaration in one compiler run
* ClassSymbol A symbol representing a class
* Denotation The meaning of a named type or symbol during a period
* MultiDenotation A denotation representing several overloaded members
* SingleDenotation A denotation representing a non-overloaded member or definition, with main fields
* symbol: Symbol
* info: Type
* UniqueRefDenotation A denotation referring to a single definition with some member type
* JointRefDenotation A denotation referring to a member that could resolve to several definitions
* SymDenotation A denotation representing a single definition with its original type, with main fields
* name: Name
* owner: Symbol
* flags: Flags
* privateWithin: Symbol
* annotations: List[Annotation]
* ClassDenotation A denotation representing a single class definition.
*/
object Denotations {
/** The signature of a denotation.
* Overloaded denotations with the same name are distinguished by
* their signatures. A signature is a list of the fully qualified names
* of the type symbols of the erasure of the parameters of the
* denotation. For instance a definition
*
* def f(x: Int)(y: List[String]): String
*
* would have signature
*
* List("scala.Int".toTypeName, "scala.collection.immutable.List".toTypeName)
*/
type Signature = List[TypeName]
/** The signature of a val or parameterless def, as opposed
* to List(), which is the signature of a zero-parameter def.
*/
val NotAMethod: Signature = List(Names.EmptyTypeName)
/** A denotation is the result of resolving
* a name (either simple identifier or select) during a given period.
*
* Denotation has two subclasses: MultiDenotation and SingleDenotation.
*
* A SingleDenotation refers to a `symbol` and a type (`info`) that the symbol has
* when seen from the reference.
*
* Denotations can be combined with `&` and `|`.
* & is conjunction, | is disjunction.
*
* `&` will create an overloaded denotation from two
* non-overloaded denotations if their signatures differ.
* Analogously `|` of two denotations with different signatures will give
* an empty denotation `NoDenotation`.
*
* A denotation might refer to `NoSymbol`. This is the case if the denotation
* was produced from a disjunction of two denotations with different symbols
* and there was no common symbol in a superclass that could substitute for
* both symbols. Here is an example:
*
* Say, we have:
*
* class A { def f: A }
* class B { def f: B }
* val x: A | B = if (test) new A else new B
* val y = x.f
*
* Then the denotation of `y` is `SingleDenotation(NoSymbol, A | B)`.
*/
abstract class Denotation extends DotClass {
/** The referencing symbol, exists only for non-overloaded denotations */
def symbol: Symbol
/** The type info of the denotation, exists only for non-overloaded denotations */
def info: Type
/** The period during which this denotation is valid. */
def validFor: Period
/** Is this a reference to a type symbol? */
def isType: Boolean
/** Is this a reference to a term symbol? */
def isTerm: Boolean = !isType
/** Is this denotation overloaded? */
def isOverloaded = isInstanceOf[MultiDenotation]
/** The signature of the denotation */
def signature(implicit ctx: Context): Signature
/** Resolve overloaded denotation to pick the one with the given signature */
def atSignature(sig: Signature)(implicit ctx: Context): SingleDenotation
/** The variant of this denotation that's current in the given context. */
def current(implicit ctx: Context): Denotation
/** Does this denotation exist?
* A denotation does not exist if it has NoType as an info.
* This is the case for NoDenotation, and also for SymDenotations
* that come from package members (classes or modules) where no
* corresponding symbol was found in a classfile or source.
*/
def exists: Boolean = true
/** If this denotation does not exist, fallback to alternative */
def orElse(that: => Denotation) = if (this.exists) this else that
/** The set of alternative single-denotations making up this denotation */
def alternatives(implicit ctx: Context): List[SingleDenotation] =
altsWith(scala.Function.const(true))
/** The alternatives of this denotation that satisfy the predicate `p`. */
def altsWith(p: Symbol => Boolean)(implicit ctx: Context): List[SingleDenotation]
/** The unique alternative of this denotation that satisfies the predicate `p`,
* or NoDenotation if no satisfying alternative exists.
* @throws TypeError if there is at more than one alternative that satisfies `p`.
*/
def suchThat(p: Symbol => Boolean)(implicit ctx: Context): SingleDenotation
/** Does this denotation have an alternative that satisfies the predicate `p`? */
def hasAltWith(p: Symbol => Boolean)(implicit ctx: Context): Boolean
/** If this denotation is overloaded, filter with given predicate.
* If result is still overloaded throw a TypeError.
* Note: disambiguate is slightly different from suchThat in that
* single-denotations that do not satisfy the predicate are left alone
* (whereas suchThat would map them to NoDenotation).
*/
def disambiguate(p: Symbol => Boolean)(implicit ctx: Context): SingleDenotation = this match {
case sdenot: SingleDenotation => sdenot
case mdenot => suchThat(p)
}
/** Return symbol in this denotation that satisfies the given predicate.
* Throw a `TypeError` if predicate fails to disambiguate symbol.
* Return a stubsymbol if no alternative satisfies the predicate.
*/
def requiredSymbol(p: Symbol => Boolean, source: AbstractFile = null)(implicit ctx: Context): Symbol = {
val sym = disambiguate(p).symbol
if (sym.exists) sym else {
val firstSym = ((NoSymbol: Symbol) /: alternatives.map(_.symbol)) (_ orElse _)
val owner = if (firstSym.exists) firstSym.owner else NoSymbol
ctx.newStubSymbol(owner, firstSym.name, source)
}
}
/** Form a denotation by conjoining with denotation `that` */
def & (that: Denotation)(implicit ctx: Context): Denotation =
if (this eq that) this
else if (!this.exists) that
else if (!that.exists) this
else that match {
case that: SingleDenotation =>
val r = mergeDenot(this, that)
if (r.exists) r else MultiDenotation(this, that)
case that @ MultiDenotation(denot1, denot2) =>
this & denot1 & denot2
}
/** Try to merge denot1 and denot2 without adding a new signature.
* If unsuccessful, return NoDenotation.
*/
private def mergeDenot(denot1: Denotation, denot2: SingleDenotation)(implicit ctx: Context): Denotation = denot1 match {
case denot1 @ MultiDenotation(denot11, denot12) =>
val d1 = mergeDenot(denot11, denot2)
if (d1.exists) denot1.derivedMultiDenotation(d1, denot2)
else {
val d2 = mergeDenot(denot12, denot2)
if (d2.exists) denot1.derivedMultiDenotation(denot11, d2)
else NoDenotation
}
case denot1: SingleDenotation =>
if (denot1 eq denot2) denot1
else if (denot1.signature == denot2.signature) {
/** symbols eligible for a joint denotation are:
* - type symbols, as long as they are not classes
* - term symbols, where concrete symbols take precedence over abstract ones.
*/
def isEligible(sym1: Symbol, sym2: Symbol) =
if (sym1.isType) !sym1.isClass
else sym1.exists && (
!(sym1 is Deferred) || !sym2.exists || (sym2 is Deferred))
/** Convert class info C to bounds C..C */
def normalize(info: Type) =
if (isType) info.bounds else info
val sym1 = denot1.symbol
val info1 = denot1.info
val sym2 = denot2.symbol
val info2 = denot2.info
val sym1Eligible = isEligible(sym1, sym2)
val sym2Eligible = isEligible(sym2, sym1)
val bounds1 = normalize(info1)
val bounds2 = normalize(info2)
if (sym2Eligible && bounds2 <:< bounds1) denot2
else if (sym1Eligible && bounds1 <:< bounds2) denot1
else new JointRefDenotation(
if (sym2Eligible) sym2 else sym1,
bounds1 & bounds2,
denot1.validFor & denot2.validFor)
} else NoDenotation
}
/** Form a choice between this denotation and that one.
* @param pre The prefix type of the members of the denotation, used
* to determine an accessible symbol if it exists.
*/
def | (that: Denotation)(pre: Type)(implicit ctx: Context): Denotation = {
def lubSym(sym1: Symbol, sym2: Symbol): Symbol = {
def qualifies(sym: Symbol) =
sym.isAccessibleFrom(pre) && sym2.owner.isSubClass(sym.owner)
sym1.allOverriddenSymbols findSymbol qualifies
}
def throwError = throw new MatchError(s"$this | $that")
if (this eq that) this
else if (!this.exists) this
else if (!that.exists) that
else this match {
case denot1 @ MultiDenotation(denot11, denot12) =>
denot1.derivedMultiDenotation((denot11 | that)(pre), (denot12 | that)(pre))
case _ =>
that match {
case denot2 @ MultiDenotation(denot21, denot22) =>
denot2.derivedMultiDenotation((this | denot21)(pre), (this | denot22)(pre))
case denot2: SingleDenotation =>
this match {
case denot1: SingleDenotation =>
if (denot1.signature != denot2.signature) NoDenotation
else new JointRefDenotation(
lubSym(denot1.symbol, denot2.symbol),
denot1.info | denot2.info,
denot1.validFor & denot2.validFor)
case _ =>
throwError
}
case _ =>
throwError
}
}
}
def show(implicit ctx: Context): String = ctx.show(this)
}
/** An overloaded denotation consisting of the alternatives of both given denotations.
*/
case class MultiDenotation(denot1: Denotation, denot2: Denotation) extends Denotation {
final def symbol = unsupported("symbol")
final def info = unsupported("info")
final def validFor = denot1.validFor & denot2.validFor
final def isType = false
def signature(implicit ctx: Context) = unsupported("signature")
def atSignature(sig: Signature)(implicit ctx: Context): SingleDenotation =
denot1.atSignature(sig) orElse denot2.atSignature(sig)
def current(implicit ctx: Context): Denotation =
derivedMultiDenotation(denot1.current, denot2.current)
def altsWith(p: Symbol => Boolean)(implicit ctx: Context): List[SingleDenotation] =
denot1.altsWith(p) ++ denot2.altsWith(p)
def suchThat(p: Symbol => Boolean)(implicit ctx: Context): SingleDenotation = {
val sd1 = denot1.suchThat(p)
val sd2 = denot2.suchThat(p)
if (sd1.exists)
if (sd2.exists) throw new TypeError(s"failure to disambiguate overloaded reference $this")
else sd1
else sd2
}
def hasAltWith(p: Symbol => Boolean)(implicit ctx: Context): Boolean =
denot1.hasAltWith(p) || denot2.hasAltWith(p)
def derivedMultiDenotation(d1: Denotation, d2: Denotation) =
if ((d1 eq denot1) && (d2 eq denot2)) this else MultiDenotation(d1, d2)
}
/** A non-overloaded denotation */
abstract class SingleDenotation extends Denotation with PreDenotation {
override def isType = info.isInstanceOf[TypeType]
override def signature(implicit ctx: Context): Signature = {
if (isType) NotAMethod
else info match {
case tp: PolyType =>
tp.resultType match {
case mt: MethodType => mt.signature
case _ => List()
}
case mt: MethodType => mt.signature
case _ => NotAMethod
}
}
def derivedSingleDenotation(symbol: Symbol, info: Type): SingleDenotation =
if ((symbol eq this.symbol) && (info eq this.info)) this
else newLikeThis(symbol, info)
protected def newLikeThis(symbol: Symbol, info: Type): SingleDenotation = this
def orElse(that: => SingleDenotation) = if (this.exists) this else that
def altsWith(p: Symbol => Boolean)(implicit ctx: Context): List[SingleDenotation] =
if (p(symbol)) this :: Nil else Nil
def suchThat(p: Symbol => Boolean)(implicit ctx: Context): SingleDenotation =
if (p(symbol)) this else NoDenotation
def hasAltWith(p: Symbol => Boolean)(implicit ctx: Context): Boolean =
p(symbol)
def atSignature(sig: Signature)(implicit ctx: Context): SingleDenotation =
if (sig == signature) this else NoDenotation
// ------ Transformations -----------------------------------------
private[this] var _validFor: Period = Nowhere
def validFor = _validFor
def validFor_=(p: Period) =
_validFor = p
/** The next SingleDenotation in this run, with wrap-around from last to first.
*
* There may be several `SingleDenotation`s with different validity
* representing the same underlying definition at different phases.
* These are called a "flock". Flock members are generated by
* @See current. Flock members are connected in a ring
* with their `nextInRun` fields.
*
* There are the following invariants concerning flock members
*
* 1) validity periods are non-overlapping
* 2) the union of all validity periods is a contiguous
* interval.
*/
var nextInRun: SingleDenotation = this
/** The version of this SingleDenotation that was valid in the first phase
* of this run.
*/
def initial: SingleDenotation = {
var current = nextInRun
while (current.validFor.code > this._validFor.code) current = current.nextInRun
current
}
/** Produce a denotation in the same flock that is valid for given context
* If one doesn't already exist, create it.
* Pre: validFor.runId == ctx.period.runId.
* Usually called when !(validFor contains ctx.period)
* (even though this is not a precondition).
*/
def current(implicit ctx: Context): SingleDenotation = {
val currentPeriod = ctx.period
val valid = _validFor
assert(valid.runId == currentPeriod.runId)
var current = this
if (currentPeriod.code > valid.code) {
// search for containing period as long as nextInRun increases.
var next = nextInRun
while (next.validFor.code > valid.code &&
!(next.validFor contains currentPeriod)) {
current = next
next = next.nextInRun
}
if (next.validFor.code > valid.code) {
// in this case, next.validFor contains currentPeriod
current = next
} else {
// not found, current points to highest existing variant
var startPid = current.validFor.lastPhaseId + 1
val transformers = ctx.transformersFor(current)
val transformer = transformers.nextTransformer(startPid)
next = transformer transform current
if (next eq current)
startPid = current.validFor.firstPhaseId
else {
current.nextInRun = next
current = next
}
current.validFor = Period(
currentPeriod.runId, startPid, transformer.lastPhaseId)
}
} else {
// currentPeriod < valid; in this case a version must exist
// but to be defensive we check for infinite loop anyway
var cnt = 0
do {
current = current.nextInRun
cnt += 1
assert(cnt <= MaxPossiblePhaseId)
} while (!(current.validFor contains currentPeriod))
}
current
}
final def asSymDenotation = asInstanceOf[SymDenotation]
// ------ PreDenotation ops ----------------------------------------------
def first = this
def toDenot(implicit ctx: Context) = this
def containsSig(sig: Signature)(implicit ctx: Context) =
signature == sig
def filterDisjoint(denots: PreDenotation)(implicit ctx: Context): PreDenotation =
if (denots.containsSig(signature)) NoDenotation else this
def filterExcluded(flags: FlagSet)(implicit ctx: Context): PreDenotation =
if (symbol is flags) NoDenotation else this
def filterAccessibleFrom(pre: Type)(implicit ctx: Context): PreDenotation =
if (symbol.isAccessibleFrom(pre)) this else NoDenotation
def asSeenFrom(pre: Type)(implicit ctx: Context): PreDenotation =
derivedSingleDenotation(symbol, info.asSeenFrom(pre, symbol.owner))
}
class UniqueRefDenotation(val symbol: Symbol,
val info: Type,
initValidFor: Period) extends SingleDenotation {
validFor = initValidFor
override protected def newLikeThis(s: Symbol, i: Type): SingleDenotation = new UniqueRefDenotation(s, i, validFor)
}
class JointRefDenotation(val symbol: Symbol,
val info: Type,
initValidFor: Period) extends SingleDenotation {
validFor = initValidFor
override protected def newLikeThis(s: Symbol, i: Type): SingleDenotation = new JointRefDenotation(s, i, validFor)
}
class ErrorDenotation(implicit ctx: Context) extends SingleDenotation {
val symbol = NoSymbol
val info = NoType
validFor = Period.allInRun(ctx.runId)
}
// --------------- PreDenotations -------------------------------------------------
/** A PreDenotation represents a group of single denotations
* It is used as an optimization to avoid forming MultiDenotations too eagerly.
*/
trait PreDenotation {
/** A denotation in the group exists */
def exists: Boolean
/** First denotation in the group */
def first: Denotation
/** Convert to full denotation by &-ing all elements */
def toDenot(implicit ctx: Context): Denotation
/** Group contains a denotation with given signature */
def containsSig(sig: Signature)(implicit ctx: Context): Boolean
/** Keep only those denotations in this group which have a signature
* that's not already defined by `denots`.
*/
def filterDisjoint(denots: PreDenotation)(implicit ctx: Context): PreDenotation
/** Keep only those denotations in this group whose flags do not intersect
* with given `flags`.
*/
def filterExcluded(flags: FlagSet)(implicit ctx: Context): PreDenotation
/** Keep only those denotations in this group which are accessible from
* type `pre`.
*/
def filterAccessibleFrom(pre: Type)(implicit ctx: Context): PreDenotation
/** The denotations as seen from given prefix type `pre`.
* @pre All denotations need to have an existing symbol.
*/
def asSeenFrom(pre: Type)(implicit ctx: Context): PreDenotation
/** The union of two groups. */
def union(that: PreDenotation) =
if (!this.exists) that
else if (that.exists) this
else DenotUnion(this, that)
}
case class DenotUnion(denots1: PreDenotation, denots2: PreDenotation) extends PreDenotation {
assert(denots1.exists && denots2.exists)
def exists = true
def first = denots1.first
def toDenot(implicit ctx: Context) = denots1.toDenot & denots2.toDenot
def containsSig(sig: Signature)(implicit ctx: Context) =
(denots1 containsSig sig) || (denots2 containsSig sig)
//def filter(p: Symbol => Boolean)(implicit ctx: Context) =
// derivedUnion(denots1 filter p, denots2 filter p)
def filterDisjoint(denots: PreDenotation)(implicit ctx: Context): PreDenotation =
derivedUnion(denots1 filterDisjoint denots, denots2 filterDisjoint denots)
def filterExcluded(flags: FlagSet)(implicit ctx: Context): PreDenotation =
derivedUnion(denots1 filterExcluded flags, denots2 filterExcluded flags)
def filterAccessibleFrom(pre: Type)(implicit ctx: Context): PreDenotation =
derivedUnion(denots1 filterAccessibleFrom pre, denots2 filterAccessibleFrom pre)
def asSeenFrom(pre: Type)(implicit ctx: Context): PreDenotation =
derivedUnion(denots1.asSeenFrom(pre), denots2.asSeenFrom(pre))
private def derivedUnion(denots1: PreDenotation, denots2: PreDenotation) =
if ((denots1 eq this.denots1) && (denots2 eq this.denots2)) this
else denots1 union denots2
}
// --------------- Context Base Trait -------------------------------
trait DenotationsBase { this: ContextBase =>
/** The current denotation of the static reference given by path. */
def staticRef(path: Name)(implicit ctx: Context): Denotation = {
def recur(path: Name, len: Int): Denotation = {
val point = path.lastIndexOf('.', len - 1)
val owner =
if (point > 0) recur(path.toTermName, point).disambiguate(_.isParameterless)
else if (path.isTermName) defn.RootClass.denot
else defn.EmptyPackageClass.denot
if (!owner.exists) NoDenotation
else {
val name = path slice (point + 1, len)
val result = owner.info.member(name)
if (result.exists) result
else {
val alt = missingHook(owner.symbol, name)
if (alt.exists) alt.denot
else result
}
}
}
recur(path, path.length)
}
/** If we are looking for a non-existing term name in a package,
* assume it is a package for which we do not have a directory and
* enter it.
*/
def missingHook(owner: Symbol, name: Name)(implicit ctx: Context): Symbol =
if (owner.isPackage && name.isTermName)
ctx.newCompletePackageSymbol(owner, name.asTermName).entered
else
NoSymbol
}
}
