Scala example source code file (Constructors.scala)
The Constructors.scala Scala example source code
/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author
*/
package scala.tools.nsc
package transform
import scala.collection.{ mutable, immutable }
import scala.collection.mutable.ListBuffer
import symtab.Flags._
/** This phase converts classes with parameters into Java-like classes with
* fields, which are assigned to from constructors.
*/
abstract class Constructors extends Statics with Transform with ast.TreeDSL {
import global._
import definitions._
/** the following two members override abstract members in Transform */
val phaseName: String = "constructors"
protected def newTransformer(unit: CompilationUnit): Transformer =
new ConstructorTransformer(unit)
private val guardedCtorStats: mutable.Map[Symbol, List[Tree]] = perRunCaches.newMap[Symbol, List[Tree]]()
private val ctorParams: mutable.Map[Symbol, List[Symbol]] = perRunCaches.newMap[Symbol, List[Symbol]]()
class ConstructorTransformer(unit: CompilationUnit) extends Transformer {
/*
* Inspect for obvious out-of-order initialization; concrete, eager vals or vars, declared in this class,
* for which a reference to the member precedes its definition.
*/
private def checkUninitializedReads(cd: ClassDef) {
val stats = cd.impl.body
val clazz = cd.symbol
def checkableForInit(sym: Symbol) = (
(sym ne null)
&& (sym.isVal || sym.isVar)
&& !(sym hasFlag LAZY | DEFERRED | SYNTHETIC)
)
val uninitializedVals = mutable.Set[Symbol](
stats collect { case vd: ValDef if checkableForInit(vd.symbol) => vd.symbol.accessedOrSelf }: _*
)
if (uninitializedVals.size > 1)
log("Checking constructor for init order issues among: " + uninitializedVals.toList.map(_.name.toString.trim).distinct.sorted.mkString(", "))
for (stat <- stats) {
// Checking the qualifier symbol is necessary to prevent a selection on
// another instance of the same class from potentially appearing to be a forward
// reference on the member in the current class.
def check(tree: Tree) = {
for (t <- tree) t match {
case t: RefTree if uninitializedVals(t.symbol.accessedOrSelf) && t.qualifier.symbol == clazz =>
unit.warning(t.pos, s"Reference to uninitialized ${t.symbol.accessedOrSelf}")
case _ =>
}
}
stat match {
case vd: ValDef =>
// doing this first allows self-referential vals, which to be a conservative
// warner we will do because it's possible though difficult for it to be useful.
uninitializedVals -= vd.symbol.accessedOrSelf
if (!vd.symbol.isLazy)
check(vd.rhs)
case _: MemberDef => // skip other member defs
case t => check(t) // constructor body statement
}
}
} // end of checkUninitializedReads()
override def transform(tree: Tree): Tree = {
tree match {
case cd @ ClassDef(mods0, name0, tparams0, impl0) if !cd.symbol.isInterface && !isPrimitiveValueClass(cd.symbol) =>
if(cd.symbol eq AnyValClass) {
cd
}
else {
checkUninitializedReads(cd)
val tplTransformer = new TemplateTransformer(unit, impl0)
treeCopy.ClassDef(cd, mods0, name0, tparams0, tplTransformer.transformed)
}
case _ =>
super.transform(tree)
}
}
} // ConstructorTransformer
/*
* Summary
* -------
*
* The following gets elided unless they're actually needed:
* (a) parameter-accessor fields for non-val, non-var, constructor-param-symbols, as well as
* (b) outer accessors of a final class which don't override anything.
*
*
* Gory details
* ------------
*
* The constructors phase elides
*
* (a) parameter-accessor fields for non-val, non-var, constructor-param-symbols
* provided they're only accessed within the primary constructor;
*
* as well as
*
* (b) outer accessors directly owned by the class of interest,
* provided that class is final, they don't override anything, and moreover they aren't accessed anywhere.
* An outer accessor is backed by a param-accessor field.
* If an outer-accessor can be elided then its supporting field can be elided as well.
*
* Once the potential candidates for elision are known (as described above) it remains to visit
* those program locations where they might be accessed, and only those.
*
* What trees can be visited at this point?
* To recap, by the time the constructors phase runs, local definitions have been hoisted out of their original owner.
* Moreover, by the time elision is about to happen, the `intoConstructors` rewriting
* of template-level statements has taken place (the resulting trees can be found in `constrStatBuf`).
*
* That means:
*
* - nested classes are to be found in `defBuf`
*
* - value and method definitions are also in `defBuf` and none of them contains local methods or classes.
*
* - auxiliary constructors are to be found in `auxConstructorBuf`
*
* Coming back to the question which trees may contain accesses:
*
* (c) regarding parameter-accessor fields, all candidates in (a) are necessarily private-local,
* and thus may only be accessed from value or method definitions owned by the current class
* (ie there's no point drilling down into nested classes).
*
* (d) regarding candidates in (b), they are accesible from all places listed in (c) and in addition
* from nested classes (nested at any number of levels).
*
* In all cases, we're done with traversing as soon as all candidates have been ruled out.
*
* Finally, the whole affair of eliding is avoided for DelayedInit subclasses,
* given that for them usually nothing gets elided anyway.
* That's a consequence from re-locating the post-super-calls statements from their original location
* (the primary constructor) into a dedicated synthetic method that an anon-closure may invoke, as required by DelayedInit.
*
*/
private trait OmittablesHelper { self: TemplateTransformer =>
/*
* Initially populated with all elision candidates.
* Trees are traversed, and those candidates are removed which are actually needed.
* After that, `omittables` doesn't shrink anymore: each symbol it contains can be unlinked from clazz.info.decls.
*/
val omittables = mutable.Set.empty[Symbol]
def populateOmittables() {
omittables.clear()
if(isDelayedInitSubclass) {
return
}
def isParamCandidateForElision(sym: Symbol) = (sym.isParamAccessor && sym.isPrivateLocal)
def isOuterCandidateForElision(sym: Symbol) = (sym.isOuterAccessor && sym.owner.isEffectivelyFinal && !sym.isOverridingSymbol)
val paramCandidatesForElision: Set[ /*Field*/ Symbol] = (clazz.info.decls.toSet filter isParamCandidateForElision)
val outerCandidatesForElision: Set[ /*Method*/ Symbol] = (clazz.info.decls.toSet filter isOuterCandidateForElision)
omittables ++= paramCandidatesForElision
omittables ++= outerCandidatesForElision
val bodyOfOuterAccessor: Map[Symbol, DefDef] =
defBuf.collect { case dd: DefDef if outerCandidatesForElision(dd.symbol) => dd.symbol -> dd }.toMap
// no point traversing further once omittables is empty, all candidates ruled out already.
object detectUsages extends Traverser {
private def markUsage(sym: Symbol) {
omittables -= debuglogResult("omittables -= ")(sym)
// recursive call to mark as needed the field supporting the outer-accessor-method.
bodyOfOuterAccessor get sym foreach (this traverse _.rhs)
}
override def traverse(tree: Tree): Unit = if (omittables.nonEmpty) {
def sym = tree.symbol
tree match {
// don't mark as "needed" the field supporting this outer-accessor, ie not just yet.
case _: DefDef if outerCandidatesForElision(sym) => ()
case _: Select if omittables(sym) => markUsage(sym) ; super.traverse(tree)
case _ => super.traverse(tree)
}
}
def walk(xs: Seq[Tree]) = xs.iterator foreach traverse
}
if (omittables.nonEmpty) {
detectUsages walk defBuf
detectUsages walk auxConstructorBuf
}
}
def mustBeKept(sym: Symbol) = !omittables(sym)
} // OmittablesHelper
/*
* TemplateTransformer rewrites DelayedInit subclasses.
* The list of statements that will end up in the primary constructor can be split into:
*
* (a) up to and including the super-constructor call.
* These statements can occur only in the (bytecode-level) primary constructor.
*
* (b) remaining statements
*
* The purpose of DelayedInit is leaving (b) out of the primary constructor and have their execution "delayed".
*
* The rewriting to achieve "delayed initialization" involves:
* (c) an additional, synthetic, public method encapsulating (b)
* (d) an additional, synthetic closure whose argless apply() just invokes (c)
* (e) after executing the statements in (a),
* the primary constructor instantiates (d) and passes it as argument
* to a `delayedInit()` invocation on the current instance.
* In turn, `delayedInit()` is a method defined as abstract in the `DelayedInit` trait
* so that it can be overridden (for an example see `scala.App`)
*
* The following helper methods prepare Trees as part of this rewriting:
*
* (f) `delayedEndpointDef()` prepares (c).
* A transformer, `constrStatTransformer`, is used to re-locate statements (b) from template-level
* to become statements in method (c). The main task here is re-formulating accesses to params
* of the primary constructors (to recap, (c) has zero-params) in terms of param-accessor fields.
* In a Delayed-Init subclass, each class-constructor gets a param-accessor field because `mustbeKept()` forces it.
*
* (g) `delayedInitClosure()` prepares (d)
*
* (h) `delayedInitCall()` prepares the `delayedInit()` invocation referred to in (e)
*
* Both (c) and (d) are added to the Template returned by `transformClassTemplate()`
*
* A note of historic interest: Previously the rewriting for DelayedInit would include in the closure body
* all of the delayed initialization sequence, which in turn required:
* - reformulating "accesses-on-this" into "accesses-on-outer", and
* - adding public getters and setters.
*
* @param stats the statements in (b) above
*
* @return the DefDef for (c) above
*
* */
private trait DelayedInitHelper { self: TemplateTransformer =>
private def delayedEndpointDef(stats: List[Tree]): DefDef = {
val methodName = currentUnit.freshTermName("delayedEndpoint$" + clazz.fullNameAsName('$').toString + "$")
val methodSym = clazz.newMethod(methodName, impl.pos, SYNTHETIC | FINAL)
methodSym setInfoAndEnter MethodType(Nil, UnitTpe)
// changeOwner needed because the `stats` contained in the DefDef were owned by the template, not long ago.
val blk = Block(stats, gen.mkZero(UnitTpe)).changeOwner(impl.symbol -> methodSym)
val delayedDD = localTyper typed { DefDef(methodSym, Nil, blk) }
delayedDD.asInstanceOf[DefDef]
}
private def delayedInitClosure(delayedEndPointSym: MethodSymbol): ClassDef = {
val satelliteClass = localTyper.typed {
atPos(impl.pos) {
val closureClass = clazz.newClass(nme.delayedInitArg.toTypeName, impl.pos, SYNTHETIC | FINAL)
val closureParents = List(AbstractFunctionClass(0).tpe)
closureClass setInfoAndEnter new ClassInfoType(closureParents, newScope, closureClass)
val outerField: TermSymbol = (
closureClass
newValue(nme.OUTER, impl.pos, PrivateLocal | PARAMACCESSOR)
setInfoAndEnter clazz.tpe
)
val applyMethod: MethodSymbol = (
closureClass
newMethod(nme.apply, impl.pos, FINAL)
setInfoAndEnter MethodType(Nil, ObjectTpe)
)
val outerFieldDef = ValDef(outerField)
val closureClassTyper = localTyper.atOwner(closureClass)
val applyMethodTyper = closureClassTyper.atOwner(applyMethod)
def applyMethodStat =
applyMethodTyper.typed {
atPos(impl.pos) {
val receiver = Select(This(closureClass), outerField)
Apply(Select(receiver, delayedEndPointSym), Nil)
}
}
val applyMethodDef = DefDef(
sym = applyMethod,
vparamss = ListOfNil,
rhs = Block(applyMethodStat, gen.mkAttributedRef(BoxedUnit_UNIT)))
ClassDef(
sym = closureClass,
constrMods = Modifiers(0),
vparamss = List(List(outerFieldDef)),
body = applyMethodDef :: Nil,
superPos = impl.pos)
}
}
satelliteClass.asInstanceOf[ClassDef]
}
private def delayedInitCall(closure: Tree) = localTyper.typedPos(impl.pos) {
gen.mkMethodCall(This(clazz), delayedInitMethod, Nil, List(New(closure.symbol.tpe, This(clazz))))
}
def rewriteDelayedInit() {
/* XXX This is not corect: remainingConstrStats.nonEmpty excludes too much,
* but excluding it includes too much. The constructor sequence being mimicked
* needs to be reproduced with total fidelity.
*
* See test case files/run/bug4680.scala, the output of which is wrong in many
* particulars.
*/
val needsDelayedInit = (isDelayedInitSubclass && remainingConstrStats.nonEmpty)
if (needsDelayedInit) {
val delayedHook: DefDef = delayedEndpointDef(remainingConstrStats)
defBuf += delayedHook
val hookCallerClass = {
// transform to make the closure-class' default constructor assign the the outer instance to its param-accessor field.
val drillDown = new ConstructorTransformer(unit)
drillDown transform delayedInitClosure(delayedHook.symbol.asInstanceOf[MethodSymbol])
}
defBuf += hookCallerClass
remainingConstrStats = delayedInitCall(hookCallerClass) :: Nil
}
}
} // DelayedInitHelper
private trait GuardianOfCtorStmts { self: TemplateTransformer =>
/* Return a single list of statements, merging the generic class constructor with the
* specialized stats. The original statements are retyped in the current class, and
* assignments to generic fields that have a corresponding specialized assignment in
* `specializedStats` are replaced by the specialized assignment.
*/
private def mergeConstructors(genericClazz: Symbol, originalStats: List[Tree], specializedStats: List[Tree]): List[Tree] = {
val specBuf = new ListBuffer[Tree]
specBuf ++= specializedStats
def specializedAssignFor(sym: Symbol): Option[Tree] =
specializedStats find {
case Assign(sel @ Select(This(_), _), _) =>
sel.symbol.isSpecialized && (nme.unspecializedName(sel.symbol.getterName) == sym.getterName)
case _ => false
}
/* Rewrite calls to ScalaRunTime.array_update to the proper apply method in scala.Array.
* Erasure transforms Array.update to ScalaRunTime.update when the element type is a type
* variable, but after specialization this is a concrete primitive type, so it would
* be an error to pass it to array_update(.., .., Object).
*/
def rewriteArrayUpdate(tree: Tree): Tree = {
val arrayUpdateMethod = currentRun.runDefinitions.arrayUpdateMethod
val adapter = new Transformer {
override def transform(t: Tree): Tree = t match {
case Apply(fun @ Select(receiver, method), List(xs, idx, v)) if fun.symbol == arrayUpdateMethod =>
localTyper.typed(Apply(gen.mkAttributedSelect(xs, arrayUpdateMethod), List(idx, v)))
case _ => super.transform(t)
}
}
adapter.transform(tree)
}
log("merging: " + originalStats.mkString("\n") + "\nwith\n" + specializedStats.mkString("\n"))
val res = for (s <- originalStats; stat = s.duplicate) yield {
log("merge: looking at " + stat)
val stat1 = stat match {
case Assign(sel @ Select(This(_), field), _) =>
specializedAssignFor(sel.symbol).getOrElse(stat)
case _ => stat
}
if (stat1 ne stat) {
log("replaced " + stat + " with " + stat1)
specBuf -= stat1
}
if (stat1 eq stat) {
assert(ctorParams(genericClazz).length == constrInfo.constrParams.length)
// this is just to make private fields public
(new specializeTypes.ImplementationAdapter(ctorParams(genericClazz), constrInfo.constrParams, null, true))(stat1)
val stat2 = rewriteArrayUpdate(stat1)
// statements coming from the original class need retyping in the current context
debuglog("retyping " + stat2)
val d = new specializeTypes.Duplicator(Map[Symbol, Type]())
d.retyped(localTyper.context1.asInstanceOf[d.Context],
stat2,
genericClazz,
clazz,
Map.empty)
} else
stat1
}
if (specBuf.nonEmpty)
println("residual specialized constructor statements: " + specBuf)
res
}
/* Add an 'if' around the statements coming after the super constructor. This
* guard is necessary if the code uses specialized fields. A specialized field is
* initialized in the subclass constructor, but the accessors are (already) overridden
* and pointing to the (empty) fields. To fix this, a class with specialized fields
* will not run its constructor statements if the instance is specialized. The specialized
* subclass includes a copy of those constructor statements, and runs them. To flag that a class
* has specialized fields, and their initialization should be deferred to the subclass, method
* 'specInstance$' is added in phase specialize.
*/
def guardSpecializedInitializer(stats: List[Tree]): List[Tree] = if (settings.nospecialization.value) stats else {
// // split the statements in presuper and postsuper
// var (prefix, postfix) = stats0.span(tree => !((tree.symbol ne null) && tree.symbol.isConstructor))
// if (postfix.nonEmpty) {
// prefix = prefix :+ postfix.head
// postfix = postfix.tail
// }
if (shouldGuard && usesSpecializedField && stats.nonEmpty) {
// save them for duplication in the specialized subclass
guardedCtorStats(clazz) = stats
ctorParams(clazz) = constrInfo.constrParams
val tree =
If(
Apply(
CODE.NOT (
Apply(gen.mkAttributedRef(specializedFlag), List())),
List()),
Block(stats, Literal(Constant(()))),
EmptyTree)
List(localTyper.typed(tree))
}
else if (clazz.hasFlag(SPECIALIZED)) {
// add initialization from its generic class constructor
val genericName = nme.unspecializedName(clazz.name)
val genericClazz = clazz.owner.info.decl(genericName.toTypeName)
assert(genericClazz != NoSymbol, clazz)
guardedCtorStats.get(genericClazz) match {
case Some(stats1) => mergeConstructors(genericClazz, stats1, stats)
case None => stats
}
} else stats
}
} // GuardianOfCtorStmts
private class TemplateTransformer(val unit: CompilationUnit, val impl: Template)
extends StaticsTransformer
with DelayedInitHelper
with OmittablesHelper
with GuardianOfCtorStmts {
val clazz = impl.symbol.owner // the transformed class
val stats = impl.body // the transformed template body
val localTyper = typer.atOwner(impl, clazz)
val specializedFlag: Symbol = clazz.info.decl(nme.SPECIALIZED_INSTANCE)
val shouldGuard = (specializedFlag != NoSymbol) && !clazz.hasFlag(SPECIALIZED)
val isDelayedInitSubclass = (clazz isSubClass DelayedInitClass)
case class ConstrInfo(
constr: DefDef, // The primary constructor
constrParams: List[Symbol], // ... and its parameters
constrBody: Block // ... and its body
)
// decompose primary constructor into the three entities above.
val constrInfo: ConstrInfo = {
val ddef = (stats find (_.symbol.isPrimaryConstructor))
ddef match {
case Some(ddef @ DefDef(_, _, _, List(vparams), _, rhs @ Block(_, _))) =>
ConstrInfo(ddef, vparams map (_.symbol), rhs)
case x =>
abort("no constructor in template: impl = " + impl)
}
}
import constrInfo._
// The parameter accessor fields which are members of the class
val paramAccessors = clazz.constrParamAccessors
// The constructor parameter corresponding to an accessor
def parameter(acc: Symbol): Symbol = parameterNamed(acc.unexpandedName.getterName)
// The constructor parameter with given name. This means the parameter
// has given name, or starts with given name, and continues with a `$` afterwards.
def parameterNamed(name: Name): Symbol = {
def matchesName(param: Symbol) = param.name == name || param.name.startsWith(name + nme.NAME_JOIN_STRING)
(constrParams filter matchesName) match {
case Nil => abort(name + " not in " + constrParams)
case p :: _ => p
}
}
/*
* `usesSpecializedField` makes a difference in deciding whether constructor-statements
* should be guarded in a `shouldGuard` class, ie in a class that's the generic super-class of
* one or more specialized sub-classes.
*
* Given that `usesSpecializedField` isn't read for any other purpose than the one described above,
* we skip setting `usesSpecializedField` in case the current class isn't `shouldGuard` to start with.
* That way, trips to a map in `specializeTypes` are saved.
*/
var usesSpecializedField: Boolean = false
// A transformer for expressions that go into the constructor
private class IntoCtorTransformer extends Transformer {
private def isParamRef(sym: Symbol) = (sym.isParamAccessor && sym.owner == clazz)
// Terminology: a stationary location is never written after being read.
private def isStationaryParamRef(sym: Symbol) = (
isParamRef(sym) &&
!(sym.isGetter && sym.accessed.isVariable) &&
!sym.isSetter
)
private def possiblySpecialized(s: Symbol) = specializeTypes.specializedTypeVars(s).nonEmpty
/*
* whether `sym` denotes a param-accessor (ie a field) that fulfills all of:
* (a) has stationary value, ie the same value provided via the corresponding ctor-arg; and
* (b) isn't subject to specialization. We might be processing statements for:
* (b.1) the constructur in the generic (super-)class; or
* (b.2) the constructor in the specialized (sub-)class.
* (c) isn't part of a DelayedInit subclass.
*/
private def canBeSupplanted(sym: Symbol) = (!isDelayedInitSubclass && isStationaryParamRef(sym) && !possiblySpecialized(sym))
override def transform(tree: Tree): Tree = tree match {
case Apply(Select(This(_), _), List()) =>
// references to parameter accessor methods of own class become references to parameters
// outer accessors become references to $outer parameter
if (canBeSupplanted(tree.symbol))
gen.mkAttributedIdent(parameter(tree.symbol.accessed)) setPos tree.pos
else if (tree.symbol.outerSource == clazz && !clazz.isImplClass)
gen.mkAttributedIdent(parameterNamed(nme.OUTER)) setPos tree.pos
else
super.transform(tree)
case Select(This(_), _) if canBeSupplanted(tree.symbol) =>
// references to parameter accessor field of own class become references to parameters
gen.mkAttributedIdent(parameter(tree.symbol)) setPos tree.pos
case Select(_, _) if shouldGuard => // reasoning behind this guard in the docu of `usesSpecializedField`
if (possiblySpecialized(tree.symbol)) {
usesSpecializedField = true
}
super.transform(tree)
case _ =>
super.transform(tree)
}
}
private val intoConstructorTransformer = new IntoCtorTransformer
// Move tree into constructor, take care of changing owner from `oldowner` to constructor symbol
def intoConstructor(oldowner: Symbol, tree: Tree) =
intoConstructorTransformer transform tree.changeOwner(oldowner -> constr.symbol)
// Should tree be moved in front of super constructor call?
def canBeMoved(tree: Tree) = tree match {
case ValDef(mods, _, _, _) => (mods hasFlag PRESUPER | PARAMACCESSOR)
case _ => false
}
// Create an assignment to class field `to` with rhs `from`
def mkAssign(to: Symbol, from: Tree): Tree =
localTyper.typedPos(to.pos) { Assign(Select(This(clazz), to), from) }
// Create code to copy parameter to parameter accessor field.
// If parameter is $outer, check that it is not null so that we NPE
// here instead of at some unknown future $outer access.
def copyParam(to: Symbol, from: Symbol): Tree = {
import CODE._
val result = mkAssign(to, Ident(from))
if (from.name != nme.OUTER ||
from.tpe.typeSymbol.isPrimitiveValueClass) result
else localTyper.typedPos(to.pos) {
// `throw null` has the same effect as `throw new NullPointerException`, see JVM spec on instruction `athrow`
IF (from OBJ_EQ NULL) THEN Throw(gen.mkZero(ThrowableTpe)) ELSE result
}
}
// The list of definitions that go into class
val defBuf = new ListBuffer[Tree]
// The auxiliary constructors, separate from the defBuf since they should
// follow the primary constructor
val auxConstructorBuf = new ListBuffer[Tree]
// The list of statements that go into the constructor after and including the superclass constructor call
val constrStatBuf = new ListBuffer[Tree]
// The list of early initializer statements that go into constructor before the superclass constructor call
val constrPrefixBuf = new ListBuffer[Tree]
// The early initialized field definitions of the class (these are the class members)
val presupers = treeInfo.preSuperFields(stats)
// The list of statements that go into the class initializer
val classInitStatBuf = new ListBuffer[Tree]
// generate code to copy pre-initialized fields
for (stat <- constrBody.stats) {
constrStatBuf += stat
stat match {
case ValDef(mods, name, _, _) if (mods hasFlag PRESUPER) =>
// stat is the constructor-local definition of the field value
val fields = presupers filter (_.getterName == name)
assert(fields.length == 1)
val to = fields.head.symbol
if (!to.tpe.isInstanceOf[ConstantType])
constrStatBuf += mkAssign(to, Ident(stat.symbol))
case _ =>
}
}
// Triage all template definitions to go into defBuf/auxConstructorBuf, constrStatBuf, or constrPrefixBuf.
for (stat <- stats) stat match {
case DefDef(_,_,_,_,_,rhs) =>
// methods with constant result type get literals as their body
// all methods except the primary constructor go into template
stat.symbol.tpe match {
case MethodType(List(), tp @ ConstantType(c)) =>
defBuf += deriveDefDef(stat)(Literal(c) setPos _.pos setType tp)
case _ =>
if (stat.symbol.isPrimaryConstructor) ()
else if (stat.symbol.isConstructor) auxConstructorBuf += stat
else defBuf += stat
}
case ValDef(mods, _, _, rhs) if !mods.hasStaticFlag =>
// val defs with constant right-hand sides are eliminated.
// for all other val defs, an empty valdef goes into the template and
// the initializer goes as an assignment into the constructor
// if the val def is an early initialized or a parameter accessor, it goes
// before the superclass constructor call, otherwise it goes after.
// Lazy vals don't get the assignment in the constructor.
if (!stat.symbol.tpe.isInstanceOf[ConstantType]) {
if (rhs != EmptyTree && !stat.symbol.isLazy) {
val rhs1 = intoConstructor(stat.symbol, rhs)
(if (canBeMoved(stat)) constrPrefixBuf else constrStatBuf) += mkAssign(
stat.symbol, rhs1)
}
defBuf += deriveValDef(stat)(_ => EmptyTree)
}
case ValDef(_, _, _, rhs) =>
// Add static initializer statements to classInitStatBuf and remove the rhs from the val def.
classInitStatBuf += mkAssign(stat.symbol, rhs)
defBuf += deriveValDef(stat)(_ => EmptyTree)
case ClassDef(_, _, _, _) =>
// classes are treated recursively, and left in the template
defBuf += new ConstructorTransformer(unit).transform(stat)
case _ =>
// all other statements go into the constructor
constrStatBuf += intoConstructor(impl.symbol, stat)
}
populateOmittables()
// Initialize all parameters fields that must be kept.
val paramInits = paramAccessors filter mustBeKept map { acc =>
// Check for conflicting symbol amongst parents: see bug #1960.
// It would be better to mangle the constructor parameter name since
// it can only be used internally, but I think we need more robust name
// mangling before we introduce more of it.
val conflict = clazz.info.nonPrivateMember(acc.name) filter (s => s.isGetter && !s.isOuterField && s.enclClass.isTrait)
if (conflict ne NoSymbol)
unit.error(acc.pos, "parameter '%s' requires field but conflicts with %s".format(acc.name, conflict.fullLocationString))
copyParam(acc, parameter(acc))
}
/* Return a pair consisting of (all statements up to and including superclass and trait constr calls, rest) */
def splitAtSuper(stats: List[Tree]) = {
def isConstr(tree: Tree): Boolean = tree match {
case Block(_, expr) => isConstr(expr) // SI-6481 account for named argument blocks
case _ => (tree.symbol ne null) && tree.symbol.isConstructor
}
val (pre, rest0) = stats span (!isConstr(_))
val (supercalls, rest) = rest0 span (isConstr(_))
(pre ::: supercalls, rest)
}
val (uptoSuperStats, remainingConstrStats0) = splitAtSuper(constrStatBuf.toList)
var remainingConstrStats = remainingConstrStats0
rewriteDelayedInit()
// Assemble final constructor
defBuf += deriveDefDef(constr)(_ =>
treeCopy.Block(
constrBody,
paramInits ::: constrPrefixBuf.toList ::: uptoSuperStats :::
guardSpecializedInitializer(remainingConstrStats),
constrBody.expr))
// Followed by any auxiliary constructors
defBuf ++= auxConstructorBuf
// Unlink all fields that can be dropped from class scope
for (sym <- clazz.info.decls ; if !mustBeKept(sym))
clazz.info.decls unlink sym
// Eliminate all field definitions that can be dropped from template
val templateWithoutOmittables: Template = deriveTemplate(impl)(_ => defBuf.toList filter (stat => mustBeKept(stat.symbol)))
// Add the static initializers
val transformed: Template = addStaticInits(templateWithoutOmittables, classInitStatBuf, localTyper)
} // TemplateTransformer
}
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