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Compiler for the Scala Programming Language
/* 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._
import util.TreeSet
/** This phase converts classes with parameters into Java-like classes with
* fields, which are assigned to from constructors.
*/
abstract class Constructors extends 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 {
def transformClassTemplate(impl: Template): Template = {
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)
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 = {
stats find (_.symbol.isPrimaryConstructor) match {
case Some(ddef @ DefDef(_, _, _, List(vparams), _, rhs @ Block(_, _))) =>
ConstrInfo(ddef, vparams map (_.symbol), rhs)
case x =>
// AnyVal constructor is OK
assert(clazz eq AnyValClass, "no constructor in template: impl = " + impl)
return 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(nme.getterName(acc.originalName))
// 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
}
}
var usesSpecializedField: Boolean = false
// A transformer for expressions that go into the constructor
val intoConstructorTransformer = new Transformer {
def isParamRef(sym: Symbol) =
sym.isParamAccessor &&
sym.owner == clazz &&
!(clazz isSubClass DelayedInitClass) &&
!(sym.isGetter && sym.accessed.isVariable) &&
!sym.isSetter
private def possiblySpecialized(s: Symbol) = specializeTypes.specializedTypeVars(s).nonEmpty
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 (isParamRef(tree.symbol) && !possiblySpecialized(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 (isParamRef(tree.symbol) && !possiblySpecialized(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 (specializeTypes.specializedTypeVars(tree.symbol).nonEmpty)
usesSpecializedField = true
super.transform(tree)
case _ =>
super.transform(tree)
}
}
// 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) {
IF (from OBJ_EQ NULL) THEN Throw(NullPointerExceptionClass.tpe) 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 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)
// 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 (
vdef => nme.localToGetter(vdef.name) == 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(_, _, _, rhs) =>
// 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 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)
}
// ----------- avoid making fields for symbols that are not accessed --------------
// A sorted set of symbols that are known to be accessed outside the primary constructor.
val accessedSyms = new TreeSet[Symbol]((x, y) => x isLess y)
// a list of outer accessor symbols and their bodies
var outerAccessors: List[(Symbol, Tree)] = List()
// Could symbol's definition be omitted, provided it is not accessed?
// This is the case if the symbol is defined in the current class, and
// ( the symbol is an object private parameter accessor field, or
// the symbol is an outer accessor of a final class which does not override another outer accessor. )
def maybeOmittable(sym: Symbol) = sym.owner == clazz && (
sym.isParamAccessor && sym.isPrivateLocal ||
sym.isOuterAccessor && sym.owner.isEffectivelyFinal && !sym.isOverridingSymbol &&
!(clazz isSubClass DelayedInitClass)
)
// Is symbol known to be accessed outside of the primary constructor,
// or is it a symbol whose definition cannot be omitted anyway?
def mustbeKept(sym: Symbol) = !maybeOmittable(sym) || (accessedSyms contains sym)
// A traverser to set accessedSyms and outerAccessors
val accessTraverser = new Traverser {
override def traverse(tree: Tree) = {
tree match {
case DefDef(_, _, _, _, _, body)
if (tree.symbol.isOuterAccessor && tree.symbol.owner == clazz && clazz.isEffectivelyFinal) =>
debuglog("outerAccessors += " + tree.symbol.fullName)
outerAccessors ::= ((tree.symbol, body))
case Select(_, _) =>
if (!mustbeKept(tree.symbol)) {
debuglog("accessedSyms += " + tree.symbol.fullName)
accessedSyms addEntry tree.symbol
}
super.traverse(tree)
case _ =>
super.traverse(tree)
}
}
}
// first traverse all definitions except outeraccesors
// (outeraccessors are avoided in accessTraverser)
for (stat <- defBuf.iterator ++ auxConstructorBuf.iterator)
accessTraverser.traverse(stat)
// then traverse all bodies of outeraccessors which are accessed themselves
// note: this relies on the fact that an outer accessor never calls another
// outer accessor in the same class.
for ((accSym, accBody) <- outerAccessors)
if (mustbeKept(accSym)) accessTraverser.traverse(accBody)
// 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 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.
*/
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(_), _), rhs) =>
( (sel.symbol hasFlag SPECIALIZED)
&& (nme.unspecializedName(nme.localToGetter(sel.symbol.name)) == nme.localToGetter(sym.name))
)
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 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 == constrParams.length)
// this is just to make private fields public
(new specializeTypes.ImplementationAdapter(ctorParams(genericClazz), 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 (usesSpecializedField && shouldGuard && stats.nonEmpty) {
// save them for duplication in the specialized subclass
guardedCtorStats(clazz) = stats
ctorParams(clazz) = 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
}
/*
def isInitDef(stat: Tree) = stat match {
case dd: DefDef => dd.symbol == delayedInitMethod
case _ => false
}
*/
/** Create a getter or a setter and enter into `clazz` scope
*/
def addAccessor(sym: Symbol, name: TermName, flags: Long) = {
val m = clazz.newMethod(name, sym.pos, flags & ~(LOCAL | PRIVATE)) setPrivateWithin clazz
clazz.info.decls enter m
}
def addGetter(sym: Symbol): Symbol = {
val getr = addAccessor(
sym, nme.getterName(sym.name), getterFlags(sym.flags))
getr setInfo MethodType(List(), sym.tpe)
defBuf += localTyper.typedPos(sym.pos)(DefDef(getr, Select(This(clazz), sym)))
getr
}
def addSetter(sym: Symbol): Symbol = {
sym setFlag MUTABLE
val setr = addAccessor(
sym, nme.getterToSetter(nme.getterName(sym.name)), setterFlags(sym.flags))
setr setInfo MethodType(setr.newSyntheticValueParams(List(sym.tpe)), UnitClass.tpe)
defBuf += localTyper.typed {
//util.trace("adding setter def for "+setr) {
atPos(sym.pos) {
DefDef(setr, paramss =>
Assign(Select(This(clazz), sym), Ident(paramss.head.head)))
}//}
}
setr
}
def ensureAccessor(sym: Symbol)(acc: => Symbol) =
if (sym.owner == clazz && !sym.isMethod && sym.isPrivate) { // there's an access to a naked field of the enclosing class
var getr = acc
getr makeNotPrivate clazz
getr
} else {
if (sym.owner == clazz) sym makeNotPrivate clazz
NoSymbol
}
def ensureGetter(sym: Symbol): Symbol = ensureAccessor(sym) {
val getr = sym.getter(clazz)
if (getr != NoSymbol) getr else addGetter(sym)
}
def ensureSetter(sym: Symbol): Symbol = ensureAccessor(sym) {
var setr = sym.setter(clazz, hasExpandedName = false)
if (setr == NoSymbol) setr = sym.setter(clazz, hasExpandedName = true)
if (setr == NoSymbol) setr = addSetter(sym)
setr
}
def delayedInitClosure(stats: List[Tree]) =
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 = (
closureClass
newValue(nme.OUTER, impl.pos, PrivateLocal | PARAMACCESSOR)
setInfoAndEnter clazz.tpe
)
val applyMethod = (
closureClass
newMethod(nme.apply, impl.pos, FINAL)
setInfoAndEnter MethodType(Nil, ObjectClass.tpe)
)
val outerFieldDef = ValDef(outerField)
val closureClassTyper = localTyper.atOwner(closureClass)
val applyMethodTyper = closureClassTyper.atOwner(applyMethod)
val constrStatTransformer = new Transformer {
override def transform(tree: Tree): Tree = tree match {
case This(_) if tree.symbol == clazz =>
applyMethodTyper.typed {
atPos(tree.pos) {
Select(This(closureClass), outerField)
}
}
case _ =>
super.transform {
tree match {
case Select(qual, _) =>
val getter = ensureGetter(tree.symbol)
if (getter != NoSymbol)
applyMethodTyper.typed {
atPos(tree.pos) {
Apply(Select(qual, getter), List())
}
}
else tree
case Assign(lhs @ Select(qual, _), rhs) =>
val setter = ensureSetter(lhs.symbol)
if (setter != NoSymbol)
applyMethodTyper.typed {
atPos(tree.pos) {
Apply(Select(qual, setter), List(rhs))
}
}
else tree
case _ =>
tree.changeOwner(impl.symbol -> applyMethod)
}
}
}
}
def applyMethodStats = constrStatTransformer.transformTrees(stats)
val applyMethodDef = DefDef(
sym = applyMethod,
vparamss = ListOfNil,
rhs = Block(applyMethodStats, gen.mkAttributedRef(BoxedUnit_UNIT)))
ClassDef(
sym = closureClass,
constrMods = Modifiers(0),
vparamss = List(List(outerFieldDef)),
argss = ListOfNil,
body = List(applyMethodDef),
superPos = impl.pos)
}
}
def delayedInitCall(closure: Tree) = localTyper.typedPos(impl.pos) {
gen.mkMethodCall(This(clazz), delayedInitMethod, Nil, List(New(closure.symbol.tpe, This(clazz))))
}
/** 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) = (tree.symbol ne null) && tree.symbol.isConstructor
val (pre, rest0) = stats span (!isConstr(_))
val (supercalls, rest) = rest0 span (isConstr(_))
(pre ::: supercalls, rest)
}
var (uptoSuperStats, remainingConstrStats) = splitAtSuper(constrStatBuf.toList)
/** 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 =
(clazz isSubClass DelayedInitClass) /*&& !(defBuf exists isInitDef)*/ && remainingConstrStats.nonEmpty
if (needsDelayedInit) {
val dicl = new ConstructorTransformer(unit) transform delayedInitClosure(remainingConstrStats)
defBuf += dicl
remainingConstrStats = List(delayedInitCall(dicl))
}
// 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
deriveTemplate(impl)(_ => defBuf.toList filter (stat => mustbeKept(stat.symbol)))
} // transformClassTemplate
override def transform(tree: Tree): Tree =
tree match {
case ClassDef(_,_,_,_) if !tree.symbol.isInterface && !isPrimitiveValueClass(tree.symbol) =>
deriveClassDef(tree)(transformClassTemplate)
case _ =>
super.transform(tree)
}
} // ConstructorTransformer
}