Scala example source code file (Mixin.scala)
The Mixin.scala Scala example source code
/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Martin Odersky
*/
package scala.tools.nsc
package transform
import symtab._
import Flags._
import scala.collection.{ mutable, immutable }
abstract class Mixin extends InfoTransform with ast.TreeDSL {
import global._
import definitions._
import CODE._
/** The name of the phase: */
val phaseName: String = "mixin"
/** The phase might set the following new flags: */
override def phaseNewFlags: Long = lateMODULE | notOVERRIDE
/** 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
/** Map a lazy, mixedin field accessor to it's trait member accessor */
private val initializer = perRunCaches.newMap[Symbol, Symbol]()
// --------- helper functions -----------------------------------------------
/** A member of a trait is implemented statically if its implementation after the
* mixin transform is in the static implementation module. 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, except for lazy value accessors which become initializer
* methods in the impl class (because they can have arbitrary initializers)
*/
private def isImplementedStatically(sym: Symbol) = (
sym.owner.isImplClass
&& sym.isMethod
&& (!sym.isModule || sym.hasFlag(PRIVATE | LIFTED))
&& (!(sym hasFlag (ACCESSOR | SUPERACCESSOR)) || sym.isLazy)
)
/** A member of a trait is static only if it belongs only to the
* implementation class, not the interface, and it is implemented
* statically.
*/
private def isStaticOnly(sym: Symbol) =
isImplementedStatically(sym) && sym.isImplOnly
/** A member of a trait is forwarded if it is implemented statically and it
* is also visible in the trait's interface. In that case, a forwarder to
* the member's static implementation will be added to the class that
* inherits the trait.
*/
private def isForwarded(sym: Symbol) =
isImplementedStatically(sym) && !sym.isImplOnly
/** Maps the type of an implementation class to its interface;
* maps all other types to themselves.
*/
private def toInterface(tp: Type): Type =
enteringMixin(tp.typeSymbol.toInterface).tpe
private def isFieldWithBitmap(field: Symbol) = {
field.info // ensure that nested objects are transformed
// For checkinit consider normal value getters
// but for lazy values only take into account lazy getters
field.isLazy && field.isMethod && !field.isDeferred
}
/** Does this field require an initialized bit?
* Note: fields of classes inheriting DelayedInit are not checked.
* This is because the they are neither initialized in the constructor
* nor do they have a setter (not if they are vals anyway). The usual
* logic for setting bitmaps does therefor not work for such fields.
* That's why they are excluded.
* Note: The `checkinit` option does not check if transient fields are initialized.
*/
private def needsInitFlag(sym: Symbol) = (
settings.checkInit
&& sym.isGetter
&& !sym.isInitializedToDefault
&& !isConstantType(sym.info.finalResultType) // SI-4742
&& !sym.hasFlag(PARAMACCESSOR | SPECIALIZED | LAZY)
&& !sym.accessed.hasFlag(PRESUPER)
&& !sym.isOuterAccessor
&& !(sym.owner isSubClass DelayedInitClass)
&& !(sym.accessed hasAnnotation TransientAttr)
)
/** Maps all parts of this type that refer to implementation classes to
* their corresponding interfaces.
*/
private val toInterfaceMap = new TypeMap {
def apply(tp: Type): Type = mapOver( tp match {
case TypeRef(pre, sym, args) if sym.isImplClass =>
typeRef(pre, enteringMixin(sym.toInterface), args)
case _ => tp
})
}
/** The implementation class corresponding to a currently compiled interface.
* todo: try to use Symbol.implClass instead?
*/
private def implClass(iface: Symbol) = iface.implClass orElse (erasure implClass iface)
/** 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 member 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, member: Symbol, mixinClass: Symbol): Symbol =
exitingSpecialize {
var bcs = base.info.baseClasses.dropWhile(mixinClass != _).tail
var sym: Symbol = NoSymbol
debuglog("starting rebindsuper " + base + " " + member + ":" + member.tpe +
" " + mixinClass + " " + base.info.baseClasses + "/" + bcs)
while (!bcs.isEmpty && sym == NoSymbol) {
if (settings.debug) {
val other = bcs.head.info.nonPrivateDecl(member.name)
debuglog("rebindsuper " + bcs.head + " " + other + " " + other.tpe +
" " + other.isDeferred)
}
sym = member.matchingSymbol(bcs.head, base.thisType).suchThat(sym => !sym.hasFlag(DEFERRED | BRIDGE))
bcs = bcs.tail
}
sym
}
// --------- type transformation -----------------------------------------------
def isConcreteAccessor(member: Symbol) =
member.hasAccessorFlag && (!member.isDeferred || (member hasFlag lateDEFERRED))
/** 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 =>
isConcreteAccessor(sym) &&
!sym.hasFlag(MIXEDIN) &&
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("new member of " + clazz + ":" + member.defString)
clazz.info.decls enter member setFlag MIXEDIN
}
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)
}
newSym
}
/** Add getters and setters for all non-module fields of an implementation
* class to its interface unless they are already present. This is done
* only once per class. The mixedin flag is used to remember whether late
* members have been added to an interface.
* - lazy fields don't get a setter.
*/
def addLateInterfaceMembers(clazz: Symbol) {
if (treatedClassInfos(clazz) != clazz.info) {
treatedClassInfos(clazz) = clazz.info
assert(phase == currentRun.mixinPhase, phase)
/* Create a new getter. Getters are never private or local. They are
* always accessors and deferred. */
def newGetter(field: Symbol): Symbol = {
// println("creating new getter for "+ field +" : "+ field.info +" at "+ field.locationString+(field hasFlag MUTABLE))
val newFlags = field.flags & ~PrivateLocal | ACCESSOR | lateDEFERRED | ( if (field.isMutable) 0 else STABLE )
// TODO preserve pre-erasure info?
clazz.newMethod(field.getterName, field.pos, newFlags) setInfo MethodType(Nil, field.info)
}
/* Create a new setter. Setters are never private or local. They are
* always accessors and deferred. */
def newSetter(field: Symbol): Symbol = {
//println("creating new setter for "+field+field.locationString+(field hasFlag MUTABLE))
val setterName = field.setterName
val newFlags = field.flags & ~PrivateLocal | ACCESSOR | lateDEFERRED
val setter = clazz.newMethod(setterName, field.pos, newFlags)
// TODO preserve pre-erasure info?
setter setInfo MethodType(setter.newSyntheticValueParams(List(field.info)), UnitTpe)
if (field.needsExpandedSetterName)
setter.name = nme.expandedSetterName(setter.name, clazz)
setter
}
clazz.info // make sure info is up to date, so that implClass is set.
val impl = implClass(clazz) orElse abort("No impl class for " + clazz)
for (member <- impl.info.decls) {
if (!member.isMethod && !member.isModule && !member.isModuleVar) {
assert(member.isTerm && !member.isDeferred, member)
if (member.getter(impl).isPrivate) {
member.makeNotPrivate(clazz) // this will also make getter&setter not private
}
val getter = member.getter(clazz)
if (getter == NoSymbol) addMember(clazz, newGetter(member))
if (!member.tpe.isInstanceOf[ConstantType] && !member.isLazy) {
val setter = member.setter(clazz)
if (setter == NoSymbol) addMember(clazz, newSetter(member))
}
}
}
debuglog("new defs of " + clazz + " = " + clazz.info.decls)
}
}
/** 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) {
def cloneAndAddMixinMember(mixinClass: Symbol, mixinMember: Symbol): Symbol = (
cloneAndAddMember(mixinClass, mixinMember, clazz)
setPos clazz.pos
resetFlag DEFERRED | lateDEFERRED
)
/* Mix in members of implementation class mixinClass into class clazz */
def mixinImplClassMembers(mixinClass: Symbol, mixinInterface: Symbol) {
if (!mixinClass.isImplClass) debugwarn ("Impl class flag is not set " +
((mixinClass.debugLocationString, mixinInterface.debugLocationString)))
for (member <- mixinClass.info.decls ; if isForwarded(member)) {
val imember = member overriddenSymbol mixinInterface
imember overridingSymbol clazz match {
case NoSymbol =>
if (clazz.info.findMember(member.name, 0, lateDEFERRED, stableOnly = false).alternatives contains imember)
cloneAndAddMixinMember(mixinInterface, imember).asInstanceOf[TermSymbol] setAlias member
case _ =>
}
}
}
/* Mix in members of trait mixinClass into class clazz. Also,
* for each lazy field in mixinClass, add a link from its mixed in member to its
* initializer method inside the implclass.
*/
def mixinTraitMembers(mixinClass: Symbol) {
// For all members of a trait's interface do:
for (mixinMember <- mixinClass.info.decls) {
if (isConcreteAccessor(mixinMember)) {
if (isOverriddenAccessor(mixinMember, clazz.info.baseClasses))
devWarning(s"Overridden concrete accessor: ${mixinMember.fullLocationString}")
else {
// mixin field accessors
val mixedInAccessor = cloneAndAddMixinMember(mixinClass, mixinMember)
if (mixinMember.isLazy) {
initializer(mixedInAccessor) = (
implClass(mixinClass).info.decl(mixinMember.name)
orElse abort("Could not find initializer for " + mixinMember.name)
)
}
if (!mixinMember.isSetter)
mixinMember.tpe match {
case MethodType(Nil, ConstantType(_)) =>
// mixinMember is a constant; only getter is needed
;
case MethodType(Nil, TypeRef(_, UnitClass, _)) =>
// mixinMember is a value of type unit. No field needed
;
case _ => // otherwise mixin a field as well
// 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 | LAZY)
| ( if (mixinMember.hasStableFlag) 0 else MUTABLE )
)
addMember(clazz, sym setFlag newFlags setAnnotations accessed.annotations)
}
}
}
else if (mixinMember.isSuperAccessor) { // 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 =>
unit.error(clazz.pos, "Member %s of mixin %s is missing a concrete super implementation.".format(
mixinMember.alias, mixinClass))
case alias1 =>
superAccessor.asInstanceOf[TermSymbol] setAlias alias1
}
}
else if (mixinMember.isMethod && mixinMember.isModule && mixinMember.hasNoFlags(LIFTED | BRIDGE)) {
// mixin objects: todo what happens with abstract objects?
addMember(clazz, mixinMember.cloneSymbol(clazz, mixinMember.flags & ~(DEFERRED | lateDEFERRED)) setPos clazz.pos)
}
}
}
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 hasFlag lateINTERFACE) {
// @SEAN: adding trait tracking so we don't have to recompile transitive closures
unit.depends += mc
addLateInterfaceMembers(mc)
mixinTraitMembers(mc)
mixinImplClassMembers(implClass(mc), mc)
}
}
/** The info transform for this phase does the following:
* - The parents of every class are mapped from implementation class to interface
* - Implementation classes become modules that inherit nothing
* and that define all.
*/
override def transformInfo(sym: Symbol, tp: Type): Type = tp match {
case ClassInfoType(parents, decls, clazz) =>
var parents1 = parents
var decls1 = decls
if (!clazz.isPackageClass) {
exitingMixin(clazz.owner.info)
if (clazz.isImplClass) {
clazz setFlag lateMODULE
var sourceModule = clazz.owner.info.decls.lookup(sym.name.toTermName)
if (sourceModule == NoSymbol) {
sourceModule = (
clazz.owner.newModuleSymbol(sym.name.toTermName, sym.pos, MODULE)
setModuleClass sym.asInstanceOf[ClassSymbol]
)
clazz.owner.info.decls enter sourceModule
}
else {
sourceModule setPos sym.pos
if (sourceModule.flags != MODULE) {
log("!!! Directly setting sourceModule flags from %s to MODULE".format(sourceModule.flagString))
sourceModule.flags = MODULE
}
}
sourceModule setInfo sym.tpe
// Companion module isn't visible for anonymous class at this point anyway
assert(clazz.sourceModule != NoSymbol || clazz.isAnonymousClass, s"$clazz has no sourceModule: $sym ${sym.tpe}")
parents1 = List()
decls1 = newScopeWith(decls.toList filter isImplementedStatically: _*)
} else if (!parents.isEmpty) {
parents1 = parents.head :: (parents.tail map toInterface)
}
}
//decls1 = enteringPhase(phase.next)(newScopeWith(decls1.toList: _*))//debug
if ((parents1 eq parents) && (decls1 eq decls)) tp
else ClassInfoType(parents1, decls1, clazz)
case MethodType(params, restp) =>
toInterfaceMap(
if (isImplementedStatically(sym)) {
val ownerParam = sym.newSyntheticValueParam(toInterface(sym.owner.typeOfThis))
MethodType(ownerParam :: params, restp)
} else
tp)
case _ =>
tp
}
/** Return 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.
*/
def singleUseFields(templ: Template): scala.collection.Map[Symbol, List[Symbol]] = {
val usedIn = mutable.HashMap[Symbol, List[Symbol]]() withDefaultValue Nil
object SingleUseTraverser extends Traverser {
override def traverse(tree: Tree) {
tree match {
case Assign(lhs, rhs) => traverse(rhs) // assignments don't count
case _ =>
if (tree.hasSymbolField && tree.symbol != NoSymbol) {
val sym = tree.symbol
if ((sym.hasAccessorFlag || (sym.isTerm && !sym.isMethod))
&& sym.isPrivate
&& !(currentOwner.isGetter && currentOwner.accessed == sym) // getter
&& !definitions.isPrimitiveValueClass(sym.tpe.resultType.typeSymbol)
&& sym.owner == templ.symbol.owner
&& !sym.isLazy
&& !tree.isDef) {
debuglog("added use in: " + currentOwner + " -- " + tree)
usedIn(sym) ::= currentOwner
}
}
super.traverse(tree)
}
}
}
SingleUseTraverser(templ)
debuglog("usedIn: " + usedIn)
usedIn filter {
case (_, member :: Nil) => member.isValue && member.isLazy
case _ => false
}
}
// --------- term transformation -----------------------------------------------
protected def newTransformer(unit: CompilationUnit): Transformer =
new MixinTransformer(unit)
class MixinTransformer(unit : CompilationUnit) extends Transformer {
/** Within a static implementation method: the parameter referring to the
* current object. Undefined everywhere else.
*/
private var self: Symbol = _
/** The rootContext used for typing */
private val rootContext =
erasure.NoContext.make(EmptyTree, rootMirror.RootClass, newScope)
/** The typer */
private var localTyper: erasure.Typer = _
private def typedPos(pos: Position)(tree: Tree): Tree = localTyper.typedPos(pos)(tree)
/** Map lazy values to the fields they should null after initialization. */
private var lazyValNullables: Map[Symbol, Set[Symbol]] = _
/** Map a field symbol to a unique integer denoting its position in the class layout.
* For each class, fields defined by the class come after inherited fields. Mixed-in
* fields count as fields defined by the class itself.
*/
private val fieldOffset = perRunCaches.newMap[Symbol, Int]()
private val bitmapKindForCategory = perRunCaches.newMap[Name, ClassSymbol]()
// ByteClass, IntClass, LongClass
private def bitmapKind(field: Symbol): ClassSymbol = bitmapKindForCategory(bitmapCategory(field))
private def flagsPerBitmap(field: Symbol): Int = bitmapKind(field) match {
case BooleanClass => 1
case ByteClass => 8
case IntClass => 32
case LongClass => 64
}
/** 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 trait, add all late interface members to the class info
* - For every static implementation method:
* - remove override flag
* - create a new method definition that also has a `self` parameter
* (which comes first) Iuli: this position is assumed by tail call elimination
* on a different receiver. Storing a new 'this' assumes it is located at
* index 0 in the local variable table. See 'STORE_THIS' and GenASM.
* - Map implementation class types in type-apply's to their interfaces
* - Remove all fields in implementation classes
*/
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 hasFlag lateINTERFACE)
addLateInterfaceMembers(currentOwner)
tree
case DefDef(_, _, _, vparams :: Nil, _, _) =>
if (currentOwner.isImplClass) {
if (isImplementedStatically(sym)) {
sym setFlag notOVERRIDE
self = sym.newValueParameter(nme.SELF, sym.pos) setInfo toInterface(currentOwner.typeOfThis)
val selfdef = ValDef(self) setType NoType
copyDefDef(tree)(vparamss = List(selfdef :: vparams))
}
else EmptyTree
}
else {
if (currentOwner.isTrait && sym.isSetter && !enteringPickler(sym.isDeferred)) {
sym.addAnnotation(TraitSetterAnnotationClass)
}
tree
}
// !!! What is this doing, and why is it only looking for exactly
// one type parameter? It would seem to be
// "Map implementation class types in type-apply's to their interfaces"
// from the comment on preTransform, but is there some way we should know
// that impl class types in type applies can only appear in single
// type parameter type constructors?
case Apply(tapp @ TypeApply(fn, List(arg)), List()) =>
if (arg.tpe.typeSymbol.isImplClass) {
val ifacetpe = toInterface(arg.tpe)
arg setType ifacetpe
tapp setType MethodType(Nil, ifacetpe)
tree setType ifacetpe
}
tree
case ValDef(_, _, _, _) if currentOwner.isImplClass =>
EmptyTree
case _ =>
tree
}
}
/** Create an identifier which references self parameter.
*/
private def selfRef(pos: Position) =
gen.mkAttributedIdent(self) setPos pos
/** Replace a super reference by this or the self parameter, depending
* on whether we are in an implementation class or not.
* Leave all other trees unchanged.
*/
private def transformSuper(tree: Tree) = tree match {
case Super(qual, _) =>
transformThis(qual)
case _ =>
tree
}
/** Replace a this reference to the current implementation class by the self
* parameter. Leave all other trees unchanged.
*/
private def transformThis(tree: Tree) = tree match {
case This(_) if tree.symbol.isImplClass =>
assert(tree.symbol == currentOwner.enclClass)
selfRef(tree.pos)
case _ =>
tree
}
/** Create a static reference to given symbol `sym` of the
* form `M.sym` where M is the symbol's implementation module.
*/
private def staticRef(sym: Symbol): Tree = {
sym.owner.info //todo: needed?
sym.owner.owner.info //todo: needed?
if (sym.owner.sourceModule eq NoSymbol)
abort(s"Cannot create static reference to $sym because ${sym.safeOwner} has no source module")
else
REF(sym.owner.sourceModule) DOT sym
}
def needsInitAndHasOffset(sym: Symbol) =
needsInitFlag(sym) && (fieldOffset contains sym)
/** Examines the symbol and returns a name indicating what brand of
* bitmap it requires. The possibilities are the BITMAP_* vals
* defined in StdNames. If it needs no bitmap, nme.NO_NAME.
*/
def bitmapCategory(field: Symbol): Name = {
import nme._
val isNormal = (
if (isFieldWithBitmap(field)) true
// bitmaps for checkinit fields are not inherited
else if (needsInitFlag(field) && !field.isDeferred) false
else return NO_NAME
)
if (field.accessed hasAnnotation TransientAttr) {
if (isNormal) BITMAP_TRANSIENT
else BITMAP_CHECKINIT_TRANSIENT
} else {
if (isNormal) BITMAP_NORMAL
else BITMAP_CHECKINIT
}
}
/** Add all new definitions to a non-trait class
* These fall into the following categories:
* - for a trait interface:
* - abstract accessors for all fields in the implementation class
* - for a non-trait class:
* - A field for every in a mixin class
* - Setters and getters for such fields
* - getters for mixed in lazy fields are completed
* - module variables and module creators for every module in a mixin class
* (except if module is lifted -- in this case the module variable
* is local to some function, and the creator method is static.)
* - 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 newDefs = mutable.ListBuffer[Tree]()
/* Attribute given tree and anchor at given position */
def attributedDef(pos: Position, tree: Tree): Tree = {
debuglog("add new def to " + clazz + ": " + tree)
typedPos(pos)(tree)
}
/* The position of given symbol, or, if this is undefined,
* the position of the current class.
*/
def position(sym: Symbol) =
if (sym.pos == NoPosition) clazz.pos else sym.pos
/* Add tree at given position as new definition */
def addDef(pos: Position, tree: Tree) {
newDefs += attributedDef(pos, tree)
}
/* Add new method definition.
*
* @param sym The method symbol.
* @param rhs The method body.
*/
def addDefDef(sym: Symbol, rhs: Tree = EmptyTree) = addDef(position(sym), DefDef(sym, rhs))
def addValDef(sym: Symbol, rhs: Tree = EmptyTree) = addDef(position(sym), ValDef(sym, rhs))
/* Add `newdefs` to `stats`, removing any abstract method definitions
* in `stats` that are matched by some symbol defined in
* `newDefs`.
*/
def add(stats: List[Tree], newDefs: List[Tree]) = {
val newSyms = newDefs map (_.symbol)
def isNotDuplicate(tree: Tree) = tree match {
case DefDef(_, _, _, _, _, _) =>
val sym = tree.symbol
!(sym.isDeferred &&
(newSyms exists (nsym => nsym.name == sym.name && (nsym.tpe matches sym.tpe))))
case _ =>
true
}
if (newDefs.isEmpty) stats
else newDefs ::: (stats filter isNotDuplicate)
}
/* 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 body = atPos(stat.pos)(Apply(Select(Super(clazz, tpnme.EMPTY), stat.symbol.alias), vparams map (v => Ident(v.symbol))))
val pt = stat.symbol.tpe.resultType
copyDefDef(stat)(rhs = enteringMixin(transform(localTyper.typed(body, pt))))
case _ =>
stat
}
/*
* Return the bitmap field for 'offset'. Depending on the hierarchy it is possible to reuse
* the bitmap of its parents. If that does not exist yet we create one.
*/
def bitmapFor(clazz0: Symbol, offset: Int, field: Symbol): Symbol = {
val category = bitmapCategory(field)
val bitmapName = nme.newBitmapName(category, offset / flagsPerBitmap(field)).toTermName
val sym = clazz0.info.decl(bitmapName)
assert(!sym.isOverloaded, sym)
def createBitmap: Symbol = {
val bitmapKind = bitmapKindForCategory(category)
val sym = clazz0.newVariable(bitmapName, clazz0.pos) setInfo bitmapKind.tpe
enteringTyper(sym addAnnotation VolatileAttr)
category match {
case nme.BITMAP_TRANSIENT | nme.BITMAP_CHECKINIT_TRANSIENT => sym addAnnotation TransientAttr
case _ =>
}
val init = bitmapKind match {
case BooleanClass => ValDef(sym, FALSE)
case _ => ValDef(sym, ZERO)
}
sym setFlag PrivateLocal
clazz0.info.decls.enter(sym)
addDef(clazz0.pos, init)
sym
}
sym orElse createBitmap
}
def maskForOffset(offset: Int, sym: Symbol, kind: ClassSymbol): Tree = {
def realOffset = offset % flagsPerBitmap(sym)
if (kind == LongClass ) LIT(1L << realOffset) else LIT(1 << realOffset)
}
/* Return an (untyped) tree of the form 'Clazz.this.bmp = Clazz.this.bmp | mask'. */
def mkSetFlag(clazz: Symbol, offset: Int, valSym: Symbol, kind: ClassSymbol): Tree = {
val bmp = bitmapFor(clazz, offset, valSym)
def mask = maskForOffset(offset, valSym, kind)
def x = This(clazz) DOT bmp
def newValue = if (kind == BooleanClass) TRUE else (x GEN_| (mask, kind))
x === newValue
}
/* Return an (untyped) tree of the form 'clazz.this.bitmapSym & mask (==|!=) 0', the
* precise comparison operator depending on the value of 'equalToZero'.
*/
def mkTest(clazz: Symbol, mask: Tree, bitmapSym: Symbol, equalToZero: Boolean, kind: ClassSymbol): Tree = {
val bitmapTree = (This(clazz) DOT bitmapSym)
def lhs = bitmapTree GEN_& (mask, kind)
kind match {
case BooleanClass =>
if (equalToZero) NOT(bitmapTree)
else bitmapTree
case _ =>
if (equalToZero) lhs GEN_== (ZERO, kind)
else lhs GEN_!= (ZERO, kind)
}
}
def mkSlowPathDef(clazz: Symbol, lzyVal: Symbol, cond: Tree, syncBody: List[Tree],
stats: List[Tree], retVal: Tree, attrThis: Tree, args: List[Tree]): Symbol = {
val defSym = clazz.newMethod(nme.newLazyValSlowComputeName(lzyVal.name.toTermName), lzyVal.pos, PRIVATE)
val params = defSym newSyntheticValueParams args.map(_.symbol.tpe)
defSym setInfoAndEnter MethodType(params, lzyVal.tpe.resultType)
val rhs: Tree = (gen.mkSynchronizedCheck(attrThis, cond, syncBody, stats)).changeOwner(currentOwner -> defSym)
val strictSubst = new TreeSymSubstituterWithCopying(args.map(_.symbol), params)
addDef(position(defSym), DefDef(defSym, strictSubst(BLOCK(rhs, retVal))))
defSym
}
def mkFastPathLazyBody(clazz: Symbol, lzyVal: Symbol, cond: Tree, syncBody: List[Tree],
stats: List[Tree], retVal: Tree): Tree = {
mkFastPathBody(clazz, lzyVal, cond, syncBody, stats, retVal, gen.mkAttributedThis(clazz), List())
}
def mkFastPathBody(clazz: Symbol, lzyVal: Symbol, cond: Tree, syncBody: List[Tree],
stats: List[Tree], retVal: Tree, attrThis: Tree, args: List[Tree]): Tree = {
val slowPathSym: Symbol = mkSlowPathDef(clazz, lzyVal, cond, syncBody, stats, retVal, attrThis, args)
If(cond, fn (This(clazz), slowPathSym, args.map(arg => Ident(arg.symbol)): _*), retVal)
}
/* Always copy the tree if we are going to perform sym substitution,
* otherwise we will side-effect on the tree that is used in the fast path
*/
class TreeSymSubstituterWithCopying(from: List[Symbol], to: List[Symbol]) extends TreeSymSubstituter(from, to) {
override def transform(tree: Tree): Tree =
if (tree.hasSymbolField && from.contains(tree.symbol))
super.transform(tree.duplicate)
else super.transform(tree.duplicate)
override def apply[T <: Tree](tree: T): T = if (from.isEmpty) tree else super.apply(tree)
}
/* return a 'lazified' version of rhs. It uses double-checked locking to ensure
* initialization is performed at most once. For performance reasons the double-checked
* locking is split into two parts, the first (fast) path checks the bitmap without
* synchronizing, and if that fails it initializes the lazy val within the
* synchronization block (slow path). This way the inliner should optimize
* the fast path because the method body is small enough.
* Private fields used only in this initializer are subsequently set to null.
*
* @param clazz The class symbol
* @param lzyVal The symbol of this lazy field
* @param init The tree which initializes the field ( f = <rhs> )
* @param offset The offset of this field in the flags bitmap
*
* The result will be a tree of the form
* { if ((bitmap&n & MASK) == 0) this.l$compute()
* else l$
*
* ...
* def l$compute() = { synchronized(this) {
* if ((bitmap$n & MASK) == 0) {
* init // l$ = <rhs>
* bitmap$n = bimap$n | MASK
* }}
* l$
* }
*
* ...
* this.f1 = null
* ... this.fn = null
* }
* where bitmap$n is a byte, int or long value acting as a bitmap of initialized values.
* The kind of the bitmap determines how many bit indicators for lazy vals are stored in it.
* For Int bitmap it is 32 and then 'n' in the above code is: (offset / 32),
* the MASK is (1 << (offset % 32)).
* If the class contains only a single lazy val then the bitmap is represented
* as a Boolean and the condition checking is a simple bool test.
*/
def mkLazyDef(clazz: Symbol, lzyVal: Symbol, init: List[Tree], retVal: Tree, offset: Int): Tree = {
def nullify(sym: Symbol) = Select(This(clazz), sym.accessedOrSelf) === LIT(null)
val bitmapSym = bitmapFor(clazz, offset, lzyVal)
val kind = bitmapKind(lzyVal)
val mask = maskForOffset(offset, lzyVal, kind)
def cond = mkTest(clazz, mask, bitmapSym, equalToZero = true, kind)
val nulls = lazyValNullables(lzyVal).toList sortBy (_.id) map nullify
def syncBody = init ::: List(mkSetFlag(clazz, offset, lzyVal, kind), UNIT)
if (nulls.nonEmpty)
log("nulling fields inside " + lzyVal + ": " + nulls)
typedPos(init.head.pos)(mkFastPathLazyBody(clazz, lzyVal, cond, syncBody, nulls, retVal))
}
def mkInnerClassAccessorDoubleChecked(attrThis: Tree, rhs: Tree, moduleSym: Symbol, args: List[Tree]): Tree =
rhs match {
case Block(List(assign), returnTree) =>
val Assign(moduleVarRef, _) = assign
val cond = Apply(Select(moduleVarRef, Object_eq), List(NULL))
mkFastPathBody(clazz, moduleSym, cond, List(assign), List(NULL), returnTree, attrThis, args)
case _ =>
abort(s"Invalid getter $rhs for module in $clazz")
}
def mkCheckedAccessor(clazz: Symbol, retVal: Tree, offset: Int, pos: Position, fieldSym: Symbol): Tree = {
val sym = fieldSym.getter(fieldSym.owner)
val bitmapSym = bitmapFor(clazz, offset, sym)
val kind = bitmapKind(sym)
val mask = maskForOffset(offset, sym, kind)
val msg = s"Uninitialized field: ${unit.source}: ${pos.line}"
val result =
IF (mkTest(clazz, mask, bitmapSym, equalToZero = false, kind)) .
THEN (retVal) .
ELSE (Throw(NewFromConstructor(UninitializedFieldConstructor, LIT(msg))))
typedPos(pos)(BLOCK(result, retVal))
}
/* Complete lazy field accessors. Applies only to classes,
* for it's own (non inherited) lazy fields. If 'checkinit'
* is enabled, getters that check for the initialized bit are
* generated, and the class constructor is changed to set the
* initialized bits.
*/
def addCheckedGetters(clazz: Symbol, stats: List[Tree]): List[Tree] = {
def dd(stat: DefDef) = {
val sym = stat.symbol
def isUnit = sym.tpe.resultType.typeSymbol == UnitClass
def isEmpty = stat.rhs == EmptyTree
if (sym.isLazy && !isEmpty && !clazz.isImplClass) {
assert(fieldOffset contains sym, sym)
deriveDefDef(stat) {
case t if isUnit => mkLazyDef(clazz, sym, List(t), UNIT, fieldOffset(sym))
case Block(stats, res) =>
mkLazyDef(clazz, sym, stats, Select(This(clazz), res.symbol), fieldOffset(sym))
case t => t // pass specialized lazy vals through
}
}
else if (needsInitFlag(sym) && !isEmpty && !clazz.hasFlag(IMPLCLASS | TRAIT)) {
assert(fieldOffset contains sym, sym)
deriveDefDef(stat)(rhs =>
(mkCheckedAccessor(clazz, _: Tree, fieldOffset(sym), stat.pos, sym))(
if (sym.tpe.resultType.typeSymbol == UnitClass) UNIT
else rhs
)
)
}
else if (sym.isConstructor) {
deriveDefDef(stat)(addInitBits(clazz, _))
}
else if (settings.checkInit && !clazz.isTrait && sym.isSetter) {
val getter = sym.getter(clazz)
if (needsInitFlag(getter) && fieldOffset.isDefinedAt(getter))
deriveDefDef(stat)(rhs => Block(List(rhs, localTyper.typed(mkSetFlag(clazz, fieldOffset(getter), getter, bitmapKind(getter)))), UNIT))
else stat
}
else if (sym.isModule && (!clazz.isTrait || clazz.isImplClass) && !sym.isBridge) {
deriveDefDef(stat)(rhs =>
typedPos(stat.pos)(
mkInnerClassAccessorDoubleChecked(
// Martin to Hubert: I think this can be replaced by selfRef(tree.pos)
// @PP: It does not seem so, it crashes for me trying to bootstrap.
if (clazz.isImplClass) gen.mkAttributedIdent(stat.vparamss.head.head.symbol) else gen.mkAttributedThis(clazz),
rhs, sym, stat.vparamss.head
)
)
)
}
else stat
}
stats map {
case defn: DefDef => dd(defn)
case stat => stat
}
}
class AddInitBitsTransformer(clazz: Symbol) extends Transformer {
private def checkedGetter(lhs: Tree) = {
val sym = clazz.info decl lhs.symbol.getterName suchThat (_.isGetter)
if (needsInitAndHasOffset(sym)) {
debuglog("adding checked getter for: " + sym + " " + lhs.symbol.flagString)
List(localTyper typed mkSetFlag(clazz, fieldOffset(sym), sym, bitmapKind(sym)))
}
else Nil
}
override def transformStats(stats: List[Tree], exprOwner: Symbol) = {
// !!! Ident(self) is never referenced, is it supposed to be confirming
// that self is anything in particular?
super.transformStats(
stats flatMap {
case stat @ Assign(lhs @ Select(This(_), _), rhs) => stat :: checkedGetter(lhs)
// remove initialization for default values
case Apply(lhs @ Select(Ident(self), _), EmptyTree.asList) if lhs.symbol.isSetter => Nil
case stat => List(stat)
},
exprOwner
)
}
}
/* Adds statements to set the 'init' bit for each field initialized
* in the body of a constructor.
*/
def addInitBits(clazz: Symbol, rhs: Tree): Tree =
new AddInitBitsTransformer(clazz) transform rhs
// begin addNewDefs
/* Fill the map from fields to offset numbers.
* Instead of field symbols, the map keeps their getter symbols. This makes
* code generation easier later.
*/
def buildBitmapOffsets() {
def fold(fields: List[Symbol], category: Name) = {
var idx = 0
fields foreach { f =>
fieldOffset(f) = idx
idx += 1
}
if (idx == 0) ()
else if (idx == 1) bitmapKindForCategory(category) = BooleanClass
else if (idx < 9) bitmapKindForCategory(category) = ByteClass
else if (idx < 33) bitmapKindForCategory(category) = IntClass
else bitmapKindForCategory(category) = LongClass
}
clazz.info.decls.toList groupBy bitmapCategory foreach {
case (nme.NO_NAME, _) => ()
case (category, fields) => fold(fields, category)
}
}
buildBitmapOffsets()
var stats1 = addCheckedGetters(clazz, stats)
def getterBody(getter: Symbol) = {
assert(getter.isGetter)
val readValue = getter.tpe match {
// A field "final val f = const" in a trait generates a getter with a ConstantType.
case MethodType(Nil, ConstantType(c)) =>
Literal(c)
case _ =>
// if it is a mixed-in lazy value, complete the accessor
if (getter.isLazy) {
val isUnit = isUnitGetter(getter)
val initCall = Apply(staticRef(initializer(getter)), gen.mkAttributedThis(clazz) :: Nil)
val selection = fieldAccess(getter)
val init = if (isUnit) initCall else atPos(getter.pos)(Assign(selection, initCall))
val returns = if (isUnit) UNIT else selection
mkLazyDef(clazz, getter, List(init), returns, fieldOffset(getter))
}
// For a field of type Unit in a trait, no actual field is generated when being mixed in.
else if (isUnitGetter(getter)) UNIT
else fieldAccess(getter)
}
if (!needsInitFlag(getter)) readValue
else mkCheckedAccessor(clazz, readValue, fieldOffset(getter), getter.pos, getter)
}
def setterBody(setter: Symbol) = {
val getter = setter.getterIn(clazz)
// A trait with a field of type Unit creates a trait setter (invoked by the
// implementation class constructor), like for any other trait field.
// However, no actual field is created in the class that mixes in the trait.
// Therefore the setter does nothing (except setting the -Xcheckinit flag).
val setInitFlag =
if (!needsInitFlag(getter)) Nil
else List(mkSetFlag(clazz, fieldOffset(getter), getter, bitmapKind(getter)))
val fieldInitializer =
if (isUnitGetter(getter)) Nil
else List(Assign(fieldAccess(setter), Ident(setter.firstParam)))
(fieldInitializer ::: setInitFlag) match {
case Nil => UNIT
// If there's only one statement, the Block factory does not actually create a Block.
case stats => Block(stats: _*)
}
}
def isUnitGetter(getter: Symbol) = getter.tpe.resultType.typeSymbol == UnitClass
def fieldAccess(accessor: Symbol) = Select(This(clazz), accessor.accessed)
def isOverriddenSetter(sym: Symbol) =
nme.isTraitSetterName(sym.name) && {
val other = sym.nextOverriddenSymbol
isOverriddenAccessor(other.getter(other.owner), clazz.info.baseClasses)
}
// for all symbols `sym` in the class definition, which are mixed in:
for (sym <- clazz.info.decls ; if sym hasFlag MIXEDIN) {
// if current class is a trait interface, add an abstract method for accessor `sym`
if (clazz hasFlag lateINTERFACE) {
addDefDef(sym)
}
// if class is not a trait add accessor definitions
else if (!clazz.isTrait) {
if (isConcreteAccessor(sym)) {
// add accessor definitions
addDefDef(sym, {
if (sym.isSetter) {
// If this is a setter of a mixed-in field which is overridden by another mixin,
// the trait setter of the overridden one does not need to do anything - the
// trait setter of the overriding field will initialize the field.
if (isOverriddenSetter(sym)) UNIT
else setterBody(sym)
}
else getterBody(sym)
})
}
else if (sym.isModule && !(sym hasFlag LIFTED | BRIDGE)) {
// add modules
val vsym = sym.owner.newModuleVarSymbol(sym)
addDef(position(sym), ValDef(vsym))
// !!! TODO - unravel the enormous duplication between this code and
// eliminateModuleDefs in RefChecks.
val rhs = gen.newModule(sym, vsym.tpe)
val assignAndRet = gen.mkAssignAndReturn(vsym, rhs)
val attrThis = gen.mkAttributedThis(clazz)
val rhs1 = mkInnerClassAccessorDoubleChecked(attrThis, assignAndRet, sym, List())
addDefDef(sym, rhs1)
}
else if (!sym.isMethod) {
// add fields
addValDef(sym)
}
else if (sym.isSuperAccessor) {
// add superaccessors
addDefDef(sym)
}
else {
// add forwarders
assert(sym.alias != NoSymbol, sym)
// debuglog("New forwarder: " + sym.defString + " => " + sym.alias.defString)
if (!sym.isMacro) addDefDef(sym, Apply(staticRef(sym.alias), gen.mkAttributedThis(clazz) :: sym.paramss.head.map(Ident)))
}
}
}
stats1 = add(stats1, newDefs.toList)
if (!clazz.isTrait) stats1 = stats1 map completeSuperAccessor
stats1
}
private def nullableFields(templ: Template): Map[Symbol, Set[Symbol]] = {
val scope = templ.symbol.owner.info.decls
// if there are no lazy fields, take the fast path and save a traversal of the whole AST
if (scope exists (_.isLazy)) {
val map = mutable.Map[Symbol, Set[Symbol]]() withDefaultValue Set()
// check what fields can be nulled for
for ((field, users) <- singleUseFields(templ); lazyFld <- users)
map(lazyFld) += field
map.toMap
}
else Map()
}
/** The transform that gets applied to a tree after it has been completely
* traversed and possible modified by a preTransform.
* This step will
* - change every node type that refers to an implementation class to its
* corresponding interface, unless the node's symbol is an implementation class.
* - 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)
* - change `this` in implementation modules to references to the self parameter
* - refer to fields in some implementation class via an abstract method in the interface.
*/
private def postTransform(tree: Tree): Tree = {
def siteWithinImplClass = currentOwner.enclClass.isImplClass
val sym = tree.symbol
// change every node type that refers to an implementation class to its
// corresponding interface, unless the node's symbol is an implementation class.
if (tree.tpe.typeSymbol.isImplClass && ((sym eq null) || !sym.isImplClass))
tree modifyType toInterface
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)
// mark fields which can be nulled afterward
lazyValNullables = nullableFields(templ) withDefaultValue Set()
// add all new definitions to current class or interface
treeCopy.Template(tree, parents1, self, addNewDefs(currentOwner, body))
// remove widening casts
case Apply(TypeApply(Select(qual, _), targ :: _), _) if isCastSymbol(sym) && (qual.tpe <:< targ.tpe) =>
qual
case Apply(Select(qual, _), args) =>
/* Changes `qual.m(args)` where m refers to an implementation
* class method to Q.m(S, args) where Q is the implementation module of
* `m` and S is the self parameter for the call, which
* is determined as follows:
* - if qual != super, qual itself
* - if qual == super, and we are in an implementation class,
* the current self parameter.
* - if qual == super, and we are not in an implementation class, `this`
*/
def staticCall(target: Symbol) = {
def implSym = implClass(sym.owner).info.member(sym.name)
assert(target ne NoSymbol,
List(sym + ":", sym.tpe, sym.owner, implClass(sym.owner), implSym,
enteringPrevPhase(implSym.tpe), phase) mkString " "
)
typedPos(tree.pos)(Apply(staticRef(target), transformSuper(qual) :: args))
}
if (isStaticOnly(sym)) {
// change calls to methods which are defined only in implementation
// classes to static calls of methods in implementation modules
staticCall(sym)
}
else qual match {
case Super(_, mix) =>
// change super calls to methods in implementation classes to static calls.
// Transform references super.m(args) as follows:
// - if `m` refers to a trait, insert a static call to the corresponding static
// implementation
// - otherwise return tree unchanged
assert(
!(mix == tpnme.EMPTY && siteWithinImplClass),
"illegal super in trait: " + currentOwner.enclClass + " " + tree
)
if (sym.owner hasFlag lateINTERFACE) {
if (sym.hasAccessorFlag) {
assert(args.isEmpty, args)
val sym1 = sym.overridingSymbol(currentOwner.enclClass)
typedPos(tree.pos)((transformSuper(qual) DOT sym1)())
}
else {
staticCall(enteringPrevPhase(sym.overridingSymbol(implClass(sym.owner))))
}
}
else {
assert(!siteWithinImplClass, currentOwner.enclClass)
tree
}
case _ =>
tree
}
case This(_) =>
transformThis(tree)
case Select(Super(_, _), name) =>
tree
case Select(qual, name) if sym.owner.isImplClass && !isStaticOnly(sym) =>
assert(!sym.isMethod, "no method allowed here: %s%s %s".format(sym, sym.isImplOnly, sym.flagString))
// refer to fields in some implementation class via an abstract
// getter in the interface.
val iface = toInterface(sym.owner.tpe).typeSymbol
val ifaceGetter = sym getter iface
if (ifaceGetter == NoSymbol) abort("No getter for " + sym + " in " + iface)
else typedPos(tree.pos)((qual DOT ifaceGetter)())
case Assign(Apply(lhs @ Select(qual, _), List()), rhs) =>
// assign to fields in some implementation class via an abstract
// setter in the interface.
def setter = lhs.symbol.setter(toInterface(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 = super.transform(preTransform(tree))
// 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
}
}
}
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