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/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala.tools.nsc
package transform
import symtab._
import Flags._
import scala.annotation.tailrec
import scala.collection.mutable
import scala.reflect.NameTransformer
import scala.reflect.internal.util.ListOfNil
abstract class Mixin extends Transform with ast.TreeDSL with AccessorSynthesis {
import global._
import definitions._
import CODE._
/** The name of the phase: */
val phaseName: String = "mixin"
/** Some trait methods need to be implemented in subclasses, so they cannot be private.
*
* We used to publicize during explicitouter (for some reason), so the condition is a bit more involved now it's done here
* (need to exclude lambdaLIFTED methods, as they do not exist during explicitouter and thus did not need to be excluded...)
*
* They may be protected, now that traits are compiled 1:1 to interfaces.
* The same disclaimers about mapping Scala's notion of visibility to Java's apply:
* we cannot emit PROTECTED methods in interfaces on the JVM,
* but knowing that these trait methods are protected means we won't emit static forwarders.
*
* JVMS: "Methods of interfaces may have any of the flags in Table 4.6-A set
* except ACC_PROTECTED, ACC_FINAL, ACC_SYNCHRONIZED, and ACC_NATIVE (JLS §9.4)."
*
* TODO: can we just set the right flags from the start??
* could we use the final flag to indicate a private method is really-really-private?
*/
def publicizeTraitMethod(sym: Symbol): Unit = {
if ((sym hasFlag PRIVATE) && !(sym hasFlag LIFTED) && ( // lambdalifted methods can remain private
// super accessors by definition must be implemented in a subclass, so can't be private
// TODO: why are they ever private in a trait to begin with!?!? (could just name mangle them to begin with)
// TODO: can we add the SYNTHESIZE_IMPL_IN_SUBCLASS flag to super accessors symbols?
(sym hasFlag SUPERACCESSOR)
// an accessor / module *may* need to be implemented in a subclass, and thus cannot be private
// TODO: document how we get here (lambdalift? fields has already made accessors not-private)
|| (sym hasFlag ACCESSOR | MODULE) && (sym hasFlag SYNTHESIZE_IMPL_IN_SUBCLASS)))
sym.makeNotPrivate(sym.owner)
// no need to make trait methods not-protected
// (we used to have to move them to another class when interfaces could not have concrete methods)
// see note in `synthFieldsAndAccessors` in Fields.scala
// if (sym hasFlag PROTECTED) sym setFlag notPROTECTED
}
/** This map contains a binding (class -> info) if
* the class with this info at phase mixinPhase has been treated for mixin composition
*/
private val treatedClassInfos = perRunCaches.newMap[Symbol, Type]() withDefaultValue NoType
// --------- helper functions -----------------------------------------------
/** A member of a trait is implemented statically if its implementation after the
* mixin transform is RHS of the method body (destined to be in an interface default method)
*
* To be statically implemented, a member must be a method that belonged to the trait's implementation class
* before (i.e. it is not abstract). Not statically implemented are
* - non-private modules: these are implemented directly in the mixin composition class
* (private modules, on the other hand, are implemented statically, but their
* module variable is not. all such private modules are lifted, because
* non-lifted private modules have been eliminated in ExplicitOuter)
* - field accessors and superaccessors
*/
private def isImplementedStatically(sym: Symbol) = (
(sym.isMethod || ((sym hasFlag MODULE) && !sym.isStatic))
// TODO: ^^^ non-static modules should have been turned into methods by fields by now, no? maybe the info transformer hasn't run???
&& notDeferred(sym)
&& sym.owner.isTrait
&& (!sym.isModule || sym.hasFlag(PRIVATE | LIFTED))
&& (!(sym hasFlag (ACCESSOR | SUPERACCESSOR)) || (sym hasFlag LAZY))
&& !sym.isPrivate
&& !sym.hasAllFlags(LIFTED | MODULE | METHOD)
&& !sym.isConstructor
&& (!sym.hasFlag(notPRIVATE | LIFTED) || sym.hasFlag(ACCESSOR | SUPERACCESSOR | MODULE))
)
/** Returns the symbol that is accessed by a super-accessor in a mixin composition.
*
* @param base The class in which everything is mixed together
* @param acc The symbol statically referred to by the superaccessor in the trait
* @param mixinClass The mixin class that produced the superaccessor
*/
private def rebindSuper(base: Symbol, acc: Symbol, mixinClass: Symbol): Symbol =
exitingSpecialize {
val site = base.thisType
// the specialized version T$sp of a trait T will have a super accessor that has the same alias
// as the super accessor in trait T; we must rebind super
// from the vantage point of the original trait T, not the specialized T$sp
// (it's inserted in the base class seq late in the game and doesn't count as a super class in the super-call scheme)
val superTargetClass = if (mixinClass.isSpecialized) unspecializedSymbol(mixinClass) else mixinClass
var bcs = base.info.baseClasses.dropWhile(superTargetClass != _).tail
var sym: Symbol = NoSymbol
// println(s"starting rebindsuper $base mixing in from $mixinClass: $acc : ${acc.tpe} of ${acc.owner} ; looking for super in $bcs (all bases: ${base.info.baseClasses})")
// don't rebind to specialized members unless we're looking for the super of a specialized member,
// since we can't jump back and forth between the unspecialized name and specialized one
// (So we jump into the non-specialized world and stay there until we hit our super.)
val likeSpecialized = if (acc.isSpecialized) 0 else SPECIALIZED
while (sym == NoSymbol && bcs.nonEmpty) {
sym = acc.matchingSymbol(bcs.head, site).suchThat(sym => !sym.hasFlag(DEFERRED | BRIDGE | likeSpecialized))
bcs = bcs.tail
}
// println(s"rebound $base from $mixinClass to $sym in ${sym.owner} ($bcs)")
// Having a matching symbol is not enough: its info should also be a subtype
// of the superaccessor's type, see test/files/run/t11351.scala
if ((sym ne acc) && sym.exists && !(sym.isErroneous || (site.memberInfo(sym) <:< site.memberInfo(acc))))
reporter.error(base.pos, s"illegal trait super target found for $acc required by $mixinClass;" +
s"\n found : ${exitingTyper{sym.defStringSeenAs(site.memberInfo(sym))}} in ${sym.owner};" +
s"\n expected: ${exitingTyper{acc.defStringSeenAs(site.memberInfo(acc))}} in ${acc.owner}")
sym
}
// --------- type transformation -----------------------------------------------
@inline final def notDeferred(sym: Symbol) = fields.notDeferredOrSynthImpl(sym)
/** Is member overridden (either directly or via a bridge) in base class sequence `bcs`? */
def isOverriddenAccessor(member: Symbol, bcs: List[Symbol]): Boolean = beforeOwnPhase {
def hasOverridingAccessor(clazz: Symbol) = {
clazz.info.nonPrivateDecl(member.name).alternatives.exists(
sym =>
sym.hasFlag(ACCESSOR) &&
!sym.hasFlag(MIXEDIN) &&
notDeferred(sym) &&
matchesType(sym.tpe, member.tpe, alwaysMatchSimple = true))
}
( bcs.head != member.owner
&& (hasOverridingAccessor(bcs.head) || isOverriddenAccessor(member, bcs.tail))
)
}
/** Add given member to given class, and mark member as mixed-in.
*/
def addMember(clazz: Symbol, member: Symbol): Symbol = {
debuglog(s"mixing into $clazz: ${member.defString}")
// This attachment is used to instruct the backend about which methods in traits require
// a static trait impl method. We remove this from the new symbol created for the method
// mixed into the subclass.
member.removeAttachment[NeedStaticImpl.type]
clazz.info.decls enter member setFlag MIXEDIN resetFlag JAVA_DEFAULTMETHOD
}
def cloneAndAddMember(mixinClass: Symbol, mixinMember: Symbol, clazz: Symbol): Symbol =
addMember(clazz, cloneBeforeErasure(mixinClass, mixinMember, clazz))
def cloneBeforeErasure(mixinClass: Symbol, mixinMember: Symbol, clazz: Symbol): Symbol = {
val newSym = enteringErasure {
// since we used `mixinMember` from the interface that represents the trait that's
// being mixed in, have to instantiate the interface type params (that may occur in mixinMember's
// info) as they are seen from the class. We can't use the member that we get from the
// implementation class, as it's a clone that was made after erasure, and thus it does not
// know its info at the beginning of erasure anymore.
val sym = mixinMember cloneSymbol clazz
val erasureMap = erasure.erasure(mixinMember)
val erasedInterfaceInfo: Type = erasureMap(mixinMember.info)
val specificForwardInfo = (clazz.thisType baseType mixinClass) memberInfo mixinMember
val forwarderInfo =
if (erasureMap(specificForwardInfo) =:= erasedInterfaceInfo)
specificForwardInfo
else {
erasedInterfaceInfo
}
// Optimize: no need if mixinClass has no typeparams.
// !!! JZ Really? What about the effect of abstract types, prefix?
if (mixinClass.typeParams.isEmpty) sym
else {
sym modifyInfo (_ => forwarderInfo)
avoidTypeParamShadowing(mixinMember, sym)
sym
}
}
newSym
}
// scala/bug#11523 rename method type parameters that shadow enclosing class type parameters in the host class
// of the mixin forwarder
private def avoidTypeParamShadowing(mixinMember: Symbol, forwarder: Symbol): Unit = {
def isForwarderTparam(sym: Symbol) = {
val owner = sym.owner
// TODO fix forwarder's info should not refer to tparams of mixinMember, fix cloning in caller!
// try forwarderInfo.cloneInfo(sym)
owner == forwarder || owner == mixinMember
}
val symTparams: mutable.Map[Name, Symbol] = mutable.Map.from(forwarder.typeParams.iterator.map(t => (t.name, t)))
forwarder.info.foreach {
case TypeRef(_, tparam, _) if tparam.isTypeParameter && !isForwarderTparam(tparam) =>
symTparams.get(tparam.name).foreach{ symTparam =>
debuglog(s"Renaming ${symTparam} (owned by ${symTparam.owner}, a mixin forwarder hosted in ${forwarder.enclClass.fullNameString}) to avoid shadowing enclosing type parameter of ${tparam.owner.fullNameString})")
symTparam.name = symTparam.name.append(NameTransformer.NAME_JOIN_STRING)
symTparams.remove(tparam.name) // only rename once
}
case _ =>
}
}
def publicizeTraitMethods(clazz: Symbol): Unit = {
if (treatedClassInfos(clazz) != clazz.info) {
treatedClassInfos(clazz) = clazz.info
assert(phase == currentRun.mixinPhase, phase)
for (member <- clazz.info.decls) {
if (member.isMethod) publicizeTraitMethod(member)
else {
assert(member.isTerm && !member.isDeferred, member)
assert(member hasFlag PRESUPER, s"unexpected $member in $clazz ${member.debugFlagString}")
clazz.info.decls.unlink(member)
}
}
debuglog("new defs of " + clazz + " = " + clazz.info.decls)
}
}
def registerRequiredDirectInterface(alias: Symbol, clazz: Symbol, msg: Type => String): Unit = {
val owner = alias.owner
if (owner.isJavaDefined && owner.isInterface) {
if (!clazz.parentSymbolsIterator.contains(owner)) {
val suggestedParent = exitingTyper(clazz.info.baseType(owner))
reporter.error(clazz.pos, msg(suggestedParent))
} else
erasure.requiredDirectInterfaces.getOrElseUpdate(clazz, mutable.Set.empty) += owner
}
}
/** Add all members to be mixed in into a (non-trait-) class
* These are:
* for every mixin trait T that is not also inherited by the superclass:
* add late interface members to T and then:
* - if a member M of T is forwarded to the implementation class, add
* a forwarder for M unless one exists already.
* The alias of the forwarder is the static member it forwards to.
* - for every abstract accessor in T, add a field and an implementation for that accessor
* - for every super accessor in T, add an implementation of that accessor
* - for every module in T, add a module
*/
def addMixedinMembers(clazz: Symbol, unit: CompilationUnit): Unit = {
def cloneAndAddMixinMember(mixinClass: Symbol, mixinMember: Symbol): Symbol = (
cloneAndAddMember(mixinClass, mixinMember, clazz)
setPos clazz.pos
resetFlag DEFERRED
)
/* Mix in members of implementation class mixinClass into class clazz */
def mixinTraitForwarders(mixinClass: Symbol): Unit = {
def isMemberOfClass(member: Symbol): Boolean =
clazz.info.findMember(member.name, 0, 0L, stableOnly = false).alternatives.contains(member)
for (member <- mixinClass.info.decls)
if (isImplementedStatically(member) && member.overridingSymbol(clazz) == NoSymbol && isMemberOfClass(member)) {
def genForwarder(required: Boolean): Unit = {
val owner = member.owner
val isJavaInterface = owner.isJavaDefined && owner.isInterface
if (isJavaInterface && !clazz.parentSymbolsIterator.contains(owner)) {
if (required) {
val text = s"Unable to implement a mixin forwarder for $member in $clazz unless interface ${owner.name} is directly extended by $clazz."
reporter.error(clazz.pos, text)
}
} else {
if (isJavaInterface)
erasure.requiredDirectInterfaces.getOrElseUpdate(clazz, mutable.Set.empty) += owner
cloneAndAddMixinMember(mixinClass, member).asInstanceOf[TermSymbol] setAlias member
}
}
// `member` is a concrete method defined in `mixinClass`, which is a base class of
// `clazz`, and the method is not overridden in `clazz`. A forwarder is needed if:
//
// - A non-trait base class of `clazz` defines a matching method. Example:
// class C {def f: Int}; trait T extends C {def f = 1}; class D extends T
// Even if C.f is abstract, the forwarder in D is needed, otherwise the JVM would
// resolve `D.f` to `C.f`, see jvms-6.5.invokevirtual.
//
// - There exists another concrete, matching method in a parent interface `p` of
// `clazz`, and the `mixinClass` does not itself extend `p`. In this case the
// forwarder is needed to disambiguate. Example:
// trait T1 {def f = 1}; trait T2 extends T1 {override def f = 2}; class C extends T2
// In C we don't need a forwarder for f because T2 extends T1, so the JVM resolves
// C.f to T2.f non-ambiguously. See jvms-5.4.3.3, "maximally-specific method".
// trait U1 {def f = 1}; trait U2 {self:U1 => override def f = 2}; class D extends U2
// In D the forwarder is needed, the interfaces U1 and U2 are unrelated at the JVM
// level.
@tailrec
def existsCompetingMethod(baseClasses: List[Symbol]): Boolean = baseClasses match {
case baseClass :: rest =>
if (baseClass ne mixinClass) {
val m = member.overriddenSymbol(baseClass)
val isCompeting = m.exists && {
!m.owner.isTraitOrInterface ||
(!m.isDeferred && !mixinClass.isNonBottomSubClass(m.owner))
}
isCompeting || existsCompetingMethod(rest)
} else existsCompetingMethod(rest)
case _ => false
}
def generateJUnitForwarder: Boolean = {
settings.mixinForwarderChoices.isAtLeastJunit &&
member.annotations.nonEmpty &&
JUnitAnnotations.exists(annot => annot.exists && member.hasAnnotation(annot))
}
def generateSerializationForwarder: Boolean = {
(member.name == nme.readResolve || member.name == nme.writeReplace) && member.info.paramss == ListOfNil
}
if (existsCompetingMethod(clazz.baseClasses) || generateJUnitForwarder || generateSerializationForwarder)
genForwarder(required = true)
else if (settings.mixinForwarderChoices.isTruthy)
genForwarder(required = false)
}
}
/* Mix in members of trait mixinClass into class clazz.
*/
def mixinTraitMembers(mixinClass: Symbol): Unit = {
// For all members of a trait's interface do:
for (mixinMember <- mixinClass.info.decls) {
if (mixinMember.hasFlag(SUPERACCESSOR)) { // mixin super accessors
val superAccessor = addMember(clazz, mixinMember.cloneSymbol(clazz)) setPos clazz.pos
assert(superAccessor.alias != NoSymbol, superAccessor)
rebindSuper(clazz, mixinMember.alias, mixinClass) match {
case NoSymbol =>
reporter.error(clazz.pos, "Member %s of mixin %s is missing a concrete super implementation.".format(
mixinMember.alias, mixinClass))
case alias1 =>
registerRequiredDirectInterface(alias1, clazz, parent =>
s"Unable to implement a super accessor required by trait ${mixinClass.name} unless $parent is directly extended by $clazz.")
if (alias1.isValue && !alias1.isMethod || alias1.isAccessor)
reporter.error(clazz.pos, s"parent $mixinClass has a super call to method ${mixinMember.alias.fullNameString}, which binds to the value ${alias1.fullNameString}. Super calls can only target methods.")
superAccessor.asInstanceOf[TermSymbol] setAlias alias1
}
}
else if (mixinMember.hasFlag(ACCESSOR) && notDeferred(mixinMember)
&& (mixinMember hasFlag PARAMACCESSOR)
&& !isOverriddenAccessor(mixinMember, clazz.info.baseClasses)) {
// mixin accessor for constructor parameter
// (note that a paramaccessor cannot have a constant type as it must have a user-defined type)
cloneAndAddMixinMember(mixinClass, mixinMember)
val name = mixinMember.name
if (!nme.isSetterName(name)) {
// enteringPhase: the private field is moved to the implementation class by erasure,
// so it can no longer be found in the mixinMember's owner (the trait)
val accessed = enteringPickler(mixinMember.accessed)
// #3857, need to retain info before erasure when cloning (since cloning only
// carries over the current entry in the type history)
val sym = enteringErasure {
// so we have a type history entry before erasure
clazz.newValue(mixinMember.localName, mixinMember.pos).setInfo(mixinMember.tpe.resultType)
}
sym updateInfo mixinMember.tpe.resultType // info at current phase
val newFlags = (
(PrivateLocal)
| (mixinMember getFlag MUTABLE)
| (if (mixinMember.hasStableFlag) 0 else MUTABLE)
)
addMember(clazz, sym setFlag newFlags setAnnotations accessed.annotations)
}
}
}
}
if (clazz.isJavaDefined || treatedClassInfos(clazz) == clazz.info)
return
treatedClassInfos(clazz) = clazz.info
assert(!clazz.isTrait && clazz.info.parents.nonEmpty, clazz)
// first complete the superclass with mixed in members
addMixedinMembers(clazz.superClass, unit)
for (mc <- clazz.mixinClasses ; if mc.isTrait) {
// @SEAN: adding trait tracking so we don't have to recompile transitive closures
unit.registerDependency(mc)
publicizeTraitMethods(mc)
mixinTraitMembers(mc)
mixinTraitForwarders(mc)
}
}
// --------- term transformation -----------------------------------------------
protected def newTransformer(unit: CompilationUnit): AstTransformer =
new MixinTransformer(unit)
class MixinTransformer(unit : CompilationUnit) extends AstTransformer with AccessorTreeSynthesis {
/** The typer */
private var localTyper: erasure.Typer = _
protected def typedPos(pos: Position)(tree: Tree): Tree = localTyper.typedPos(pos)(tree)
/** The rootContext used for typing */
private val rootContext =
erasure.NoContext.make(EmptyTree, rootMirror.RootClass, newScope)
private val nullables = mutable.AnyRefMap[Symbol, Map[Symbol, List[Symbol]]]()
/** The first transform; called in a pre-order traversal at phase mixin
* (that is, every node is processed before its children).
* What transform does:
* - For every non-trait class, add all mixed in members to the class info.
* - For every non-trait class, assign null to singly used private fields after use in lazy initialization.
*/
private def preTransform(tree: Tree): Tree = {
val sym = tree.symbol
tree match {
case Template(parents, self, body) =>
localTyper = erasure.newTyper(rootContext.make(tree, currentOwner))
exitingMixin(currentOwner.owner.info)//todo: needed?
if (!currentOwner.isTrait && !isPrimitiveValueClass(currentOwner))
addMixedinMembers(currentOwner, unit)
else if (currentOwner.isTrait)
publicizeTraitMethods(currentOwner)
if (!currentOwner.isTrait)
nullables(currentOwner) = lazyValNullables(currentOwner, body)
tree
case dd: DefDef if dd.symbol.name.endsWith(nme.LAZY_SLOW_SUFFIX) =>
val fieldsToNull = nullables.getOrElse(sym.enclClass, Map()).getOrElse(sym, Nil)
if (fieldsToNull.isEmpty) dd
else {
deriveDefDef(dd) {
case blk@Block(stats, expr) =>
assert(dd.symbol.originalOwner.isClass, dd.symbol)
def nullify(sym: Symbol) = {
sym.accessedOrSelf.setFlag(MUTABLE)
Select(gen.mkAttributedThis(sym.enclClass), sym.accessedOrSelf) === NULL
}
val stats1 = stats ::: fieldsToNull.map(nullify)
treeCopy.Block(blk, stats1, expr)
case tree =>
devWarning("Unexpected tree shape in lazy slow path")
tree
}
}
case _ => tree
}
}
/** Map lazy values to the fields they should null after initialization. */
def lazyValNullables(clazz: Symbol, templStats: List[Tree]): Map[Symbol, List[Symbol]] = {
// if there are no lazy fields, take the fast path and save a traversal of the whole AST
if (!clazz.info.decls.exists(_.isLazy)) Map()
else {
// A map of single-use fields to the lazy value that uses them during initialization.
// Each field has to be private and defined in the enclosing class, and there must
// be exactly one lazy value using it.
//
// Such fields will be nulled after the initializer has memoized the lazy value.
val singleUseFields: Map[Symbol, List[Symbol]] = {
val usedIn = mutable.HashMap[Symbol, List[Symbol]]() withDefaultValue Nil
object SingleUseTraverser extends InternalTraverser {
override def traverse(tree: Tree): Unit = {
tree match {
// assignment targets don't count as a dereference -- only check the rhs
case Assign(_, rhs) => traverse(rhs)
case tree: RefTree if tree.symbol != NoSymbol =>
val sym = tree.symbol
// println(s"$sym in ${sym.owner} from $currentOwner ($tree)")
if ((sym.hasAccessorFlag || (sym.isTerm && !sym.isMethod)) && sym.isPrivate && !sym.isLazy && !sym.isModule // non-lazy private field or its accessor
&& !definitions.isPrimitiveValueClass(sym.tpe.resultType.typeSymbol) // primitives don't hang on to significant amounts of heap
&& sym.owner == currentOwner.enclClass && !(currentOwner.isGetter && currentOwner.accessed == sym)) {
// println("added use in: " + currentOwner + " -- " + tree)
usedIn(sym) ::= currentOwner
}
tree.traverse(this)
case _ => tree.traverse(this)
}
}
}
templStats foreach SingleUseTraverser.apply
// println("usedIn: " + usedIn)
// only consider usages from non-transient lazy vals (scala/bug#9365)
val singlyUsedIn = usedIn.filter {
case (_, member :: Nil) if member.name.endsWith(nme.LAZY_SLOW_SUFFIX) =>
val lazyAccessor = member.owner.info.decl(member.name.stripSuffix(nme.LAZY_SLOW_SUFFIX))
!lazyAccessor.accessedOrSelf.hasAnnotation(TransientAttr)
case _ => false
}.toMap
// println("singlyUsedIn: " + singlyUsedIn)
singlyUsedIn
}
val map = mutable.Map[Symbol, Set[Symbol]]() withDefaultValue Set()
// invert the map to see which fields can be nulled for each non-transient lazy val
for ((field, users) <- singleUseFields; lazyFld <- users) map(lazyFld) += field
map.view.mapValues(_.toList.sortBy(_.id)).toMap
}
}
/** Add all new definitions to a non-trait class
*
* These fall into the following categories:
* - for a trait interface:
* - abstract accessors for all paramaccessor or early initialized fields
* - for a non-trait class:
* - field and accessor implementations for each inherited paramaccessor or early initialized field
* - A super accessor for every super accessor in a mixin class
* - Forwarders for all methods that are implemented statically
*
* All superaccessors are completed with right-hand sides (@see completeSuperAccessor)
*
* @param clazz The class to which definitions are added
*/
private def addNewDefs(clazz: Symbol, stats: List[Tree]): List[Tree] = {
val accessorSynth = new UncheckedAccessorSynth(clazz)
import accessorSynth._
// for all symbols `sym` in the class definition, which are mixed in by mixinTraitMembers
for (sym <- clazz.info.decls ; if sym hasFlag MIXEDIN) {
// if current class is a trait, add an abstract method for accessor `sym`
// ditto for a super accessor (will get an RHS in completeSuperAccessor)
if (clazz.isTrait || sym.isSuperAccessor) addDefDef(sym)
// implement methods mixed in from a supertrait (the symbols were created by mixinTraitMembers)
else if (sym.hasFlag(ACCESSOR) && !sym.hasFlag(DEFERRED)) {
assert(sym hasFlag (PARAMACCESSOR), s"mixed in $sym from $clazz is not param?!?")
// add accessor definitions
addDefDef(sym, accessorBody(sym))
}
else if (!sym.isMethod) addValDef(sym) // field
else if (!sym.isMacro) { // forwarder
assert(sym.alias != NoSymbol, (sym, sym.debugFlagString, clazz))
// debuglog("New forwarder: " + sym.defString + " => " + sym.alias.defString)
addDefDef(sym, Apply(SuperSelect(clazz, sym.alias), sym.paramss.head.map(Ident(_))))
}
}
val implementedAccessors = implementWithNewDefs(stats)
if (clazz.isTrait)
implementedAccessors filter {
case vd: ValDef => assert(vd.symbol.hasFlag(PRESUPER | PARAMACCESSOR), s"unexpected valdef $vd in trait $clazz"); false
case _ => true
}
else {
/* If `stat` is a superaccessor, complete it by adding a right-hand side.
* Note: superaccessors are always abstract until this point.
* The method to call in a superaccessor is stored in the accessor symbol's alias field.
* The rhs is:
* super.A(xs) where A is the super accessor's alias and xs are its formal parameters.
* This rhs is typed and then mixin transformed.
*/
def completeSuperAccessor(stat: Tree) = stat match {
case DefDef(_, _, _, vparams :: Nil, _, EmptyTree) if stat.symbol.isSuperAccessor =>
val alias = stat.symbol.alias
debuglog(s"implementing super accessor in $clazz for ${stat.symbol} --> ${alias.owner} . ${alias}")
registerRequiredDirectInterface(alias, clazz, parent =>
s"Unable to implement a super accessor, $parent needs to be directly extended by $clazz.")
val body = atPos(stat.pos)(Apply(SuperSelect(clazz, alias), vparams map (v => Ident(v.symbol))))
val pt = stat.symbol.tpe.resultType
copyDefDef(stat)(rhs = enteringMixin(transform(localTyper.typed(body, pt))))
case _ =>
stat
}
implementedAccessors map completeSuperAccessor
}
}
/** The transform that gets applied to a tree after it has been completely
* traversed and possible modified by a preTransform.
* This step will
* - change parents of templates to conform to parents in the symbol info
* - add all new definitions to a class or interface
* - remove widening casts
* - change calls to methods which are defined only in implementation classes
* to static calls of methods in implementation modules (@see staticCall)
* - change super calls to methods in implementation classes to static calls
* (@see staticCall)
*/
private def postTransform(tree: Tree): Tree = {
val sym = tree.symbol
tree match {
case templ @ Template(parents, self, body) =>
// change parents of templates to conform to parents in the symbol info
val parents1 = currentOwner.info.parents map (t => TypeTree(t) setPos tree.pos)
// add all new definitions to current class or interface
val statsWithNewDefs = addNewDefs(currentOwner, body)
statsWithNewDefs foreach {
case dd: DefDef if isTraitMethodRequiringStaticImpl(dd) =>
dd.symbol.updateAttachment(NeedStaticImpl)
case _ =>
}
treeCopy.Template(tree, parents1, self, statsWithNewDefs)
case Select(qual, name) if sym.owner.isTrait && !sym.isMethod =>
assert(sym.hasFlag(PARAMACCESSOR | PRESUPER), s"!!! Unexpected reference to field $sym in trait $currentOwner")
// refer to fields in some trait an abstract getter in the interface.
val ifaceGetter = sym getterIn sym.owner
if (ifaceGetter == NoSymbol) abort("No getter for " + sym + " in " + sym.owner)
else typedPos(tree.pos)((qual DOT ifaceGetter)())
case Assign(Apply(lhs @ Select(qual, _), List()), rhs) =>
// assign to fields in some trait via an abstract setter in the interface.
// Note that the case above has added the empty application.
val setter = lhs.symbol.setterIn(lhs.symbol.owner.tpe.typeSymbol) setPos lhs.pos
typedPos(tree.pos)((qual DOT setter)(rhs))
case _ =>
tree
}
}
/** The main transform method.
* This performs pre-order traversal preTransform at mixin phase;
* when coming back, it performs a postTransform at phase after.
*/
override def transform(tree: Tree): Tree = {
val saved = localTyper
val tree1 = preTransform(tree).transform(this)
// localTyper needed when not flattening inner classes. parts after an
// inner class will otherwise be typechecked with a wrong scope
try exitingMixin(postTransform(tree1))
finally localTyper = saved
}
}
private def isTraitMethodRequiringStaticImpl(dd: DefDef): Boolean = {
val sym = dd.symbol
dd.rhs.nonEmpty &&
sym.owner.isTrait &&
!sym.isPrivate && // no need to put implementations of private methods into a static method
!sym.hasFlag(Flags.STATIC)
}
case object NeedStaticImpl extends PlainAttachment
}
