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|
/* NSC -- new Scala compiler
* Copyrights 2005-2010 LAMP/EPFL
* @author Martin Odersky
*/
// $Id$
package scala.tools.nsc
package transform
import symtab._
import Flags._
import scala.tools.nsc.util.Position
import scala.collection.mutable.{ListBuffer, HashMap}
abstract class CleanUp extends Transform with ast.TreeDSL {
import global._
import definitions._
import CODE._
/** the following two members override abstract members in Transform */
val phaseName: String = "cleanup"
protected def newTransformer(unit: CompilationUnit): Transformer =
new CleanUpTransformer(unit)
class CleanUpTransformer(unit: CompilationUnit) extends Transformer {
private val newDefs = new ListBuffer[Tree]
private val newInits = new ListBuffer[Tree]
private val classConstantMeth = new HashMap[String, Symbol]
private val symbolStaticFields = new HashMap[String, (Symbol, Tree, Tree)]
private var localTyper: analyzer.Typer = null
private lazy val serializableAnnotation =
AnnotationInfo(SerializableAttr.tpe, Nil, Nil)
private lazy val serialVersionUIDAnnotation = {
val attr = definitions.getClass("scala.SerialVersionUID")
AnnotationInfo(attr.tpe, List(Literal(Constant(0))), List())
}
private object MethodDispatchType extends scala.Enumeration {
val NO_CACHE, MONO_CACHE, POLY_CACHE = Value
}
import MethodDispatchType.{ NO_CACHE, MONO_CACHE, POLY_CACHE }
private def dispatchType() = settings.refinementMethodDispatch.value match {
case "no-cache" => NO_CACHE
case "mono-cache" => MONO_CACHE
case "poly-cache" => POLY_CACHE
}
private def typedWithPos(pos: Position)(tree: Tree) =
localTyper typed { atPos(pos)(tree) }
override def transformUnit(unit: CompilationUnit) =
unit.body = transform(unit.body)
/** A value class is defined to be only Java-compatible values: unit is
* not part of it, as opposed to isValueClass in definitions. scala.Int is
* a value class, java.lang.Integer is not. */
def isJavaValueClass(sym: Symbol) = boxedClass contains sym
override def transform(tree: Tree): Tree = tree match {
/* Transforms dynamic calls (i.e. calls to methods that are undefined
* in the erased type space) to -- dynamically -- unsafe calls using
* reflection. This is used for structural sub-typing of refinement
* types, but may be used for other dynamic calls in the future.
* For 'a.f(b)' it will generate something like:
* 'a.getClass().
* ' getMethod("f", Array(classOf[b.type])).
* ' invoke(a, Array(b))
* plus all the necessary casting/boxing/etc. machinery required
* for type-compatibility (see fixResult).
*
* USAGE CONTRACT:
* There are a number of assumptions made on the way a dynamic apply
* is used. Assumptions relative to type are handled by the erasure
* phase.
* - The applied arguments are compatible with AnyRef, which means
* that an argument tree typed as AnyVal has already been extended
* with the necessary boxing calls. This implies that passed
* arguments might not be strictly compatible with the method's
* parameter types (a boxed integer while int is expected).
* - The expected return type is an AnyRef, even when the method's
* return type is an AnyVal. This means that the tree containing the
* call has already been extended with the necessary unboxing calls
* (or is happy with the boxed type).
* - The type-checker has prevented dynamic applies on methods which
* parameter's erased types are not statically known at the call site.
* This is necessary to allow dispatching the call to the correct
* method (dispatching on paramters is static in Scala). In practice,
* this limitation only arises when the called method is defined as a
* refinement, where the refinement defines a parameter based on a
* type variable. */
case ad@ApplyDynamic(qual0, params) =>
def mkName(s: String = "") =
if (s == "") unit.fresh newName ad.pos
else unit.fresh.newName(ad.pos, s)
def mkTerm(s: String = "") = newTermName(mkName(s))
val typedPos = typedWithPos(ad.pos) _
assert(ad.symbol.isPublic)
var qual: Tree = qual0
/* ### CREATING THE METHOD CACHE ### */
def addStaticVariableToClass(forName: String, forType: Type, forInit: Tree, isFinal: Boolean): Symbol = {
val varSym = currentClass.newVariable(ad.pos, mkName(forName))
.setFlag(PRIVATE | STATIC | MUTABLE | SYNTHETIC)
.setInfo(forType)
if (isFinal) varSym setFlag FINAL else varSym addAnnotation AnnotationInfo(VolatileAttr.tpe, Nil, Nil)
currentClass.info.decls enter varSym
val varDef = typedPos( VAL(varSym) === forInit )
newDefs append transform(varDef)
val varInit = typedPos( REF(varSym) === forInit )
newInits append transform(varInit)
varSym
}
def addStaticMethodToClass(forName: String, forArgsTypes: List[Type], forResultType: Type)
(forBody: Pair[Symbol, List[Symbol]] => Tree): Symbol = {
val methSym = currentClass.newMethod(ad.pos, mkName(forName))
.setFlag(STATIC | SYNTHETIC)
methSym.setInfo(MethodType(methSym.newSyntheticValueParams(forArgsTypes), forResultType))
currentClass.info.decls enter methSym
val methDef = typedPos( DefDef(methSym, { forBody(Pair(methSym, methSym.paramss(0))) }) )
newDefs append transform(methDef)
methSym
}
def fromTypesToClassArrayLiteral(paramTypes: List[Type]): Tree =
ArrayValue(TypeTree(ClassClass.tpe), paramTypes map LIT)
def theTypeClassArray =
TypeRef(ArrayClass.tpe.prefix, ArrayClass, List(ClassClass.tpe))
/* ... */
def reflectiveMethodCache(method: String, paramTypes: List[Type]): Symbol = dispatchType match {
case NO_CACHE =>
/* Implementation of the cache is as follows for method "def xyz(a: A, b: B)":
var reflParams$Cache: Array[Class[_]] = Array[JClass](classOf[A], classOf[B])
def reflMethod$Method(forReceiver: JClass[_]): JMethod =
forReceiver.getMethod("xyz", reflParams$Cache)
*/
val reflParamsCacheSym: Symbol =
addStaticVariableToClass("reflParams$Cache", theTypeClassArray, fromTypesToClassArrayLiteral(paramTypes), true)
addStaticMethodToClass("reflMethod$Method", List(ClassClass.tpe), MethodClass.tpe) {
case Pair(reflMethodSym, List(forReceiverSym)) =>
(REF(forReceiverSym) DOT Class_getMethod)(LIT(method), REF(reflParamsCacheSym))
}
case MONO_CACHE =>
/* Implementation of the cache is as follows for method "def xyz(a: A, b: B)"
(but with a SoftReference wrapping reflClass$Cache, similarly in the poly Cache) :
var reflParams$Cache: Array[Class[_]] = Array[JClass](classOf[A], classOf[B])
var reflMethod$Cache: JMethod = null
var reflClass$Cache: JClass[_] = null
def reflMethod$Method(forReceiver: JClass[_]): JMethod = {
if (reflClass$Cache != forReceiver) {
reflMethod$Cache = forReceiver.getMethod("xyz", reflParams$Cache)
reflClass$Cache = forReceiver
}
reflMethod$Cache
}
*/
val reflParamsCacheSym: Symbol =
addStaticVariableToClass("reflParams$Cache", theTypeClassArray, fromTypesToClassArrayLiteral(paramTypes), true)
val reflMethodCacheSym: Symbol =
addStaticVariableToClass("reflMethod$Cache", MethodClass.tpe, NULL, false)
val reflClassCacheSym: Symbol =
addStaticVariableToClass("reflClass$Cache", SoftReferenceClass.tpe, NULL, false)
def getMethodSym = ClassClass.tpe member nme.getMethod_
def isCacheEmpty(receiver: Symbol): Tree =
reflClassCacheSym.IS_NULL() OR (reflClassCacheSym.GET() ANY_NE REF(receiver))
addStaticMethodToClass("reflMethod$Method", List(ClassClass.tpe), MethodClass.tpe) {
case Pair(reflMethodSym, List(forReceiverSym)) =>
BLOCK(
IF (isCacheEmpty(forReceiverSym)) THEN BLOCK(
REF(reflMethodCacheSym) === ((REF(forReceiverSym) DOT getMethodSym)(LIT(method), REF(reflParamsCacheSym))) ,
REF(reflClassCacheSym) === gen.mkSoftRef(REF(forReceiverSym)),
UNIT
) ENDIF,
REF(reflMethodCacheSym)
)
}
case POLY_CACHE =>
/* Implementation of the cache is as follows for method "def xyz(a: A, b: B)"
(but with the addition of a SoftReference wrapped around the MethodCache holder
so that it does not interfere with classloader garbage collection, see ticket
#2365 for details):
var reflParams$Cache: Array[Class[_]] = Array[JClass](classOf[A], classOf[B])
var reflPoly$Cache: scala.runtime.MethodCache = new EmptyMethodCache()
def reflMethod$Method(forReceiver: JClass[_]): JMethod = {
var method: JMethod = reflPoly$Cache.find(forReceiver)
if (method != null)
return method
else {
method = forReceiver.getMethod("xyz", reflParams$Cache)
reflPoly$Cache = reflPoly$Cache.add(forReceiver, method)
return method
}
}
*/
val reflParamsCacheSym: Symbol =
addStaticVariableToClass("reflParams$Cache", theTypeClassArray, fromTypesToClassArrayLiteral(paramTypes), true)
def mkNewPolyCache = gen.mkSoftRef(NEW(TypeTree(EmptyMethodCacheClass.tpe)))
val reflPolyCacheSym: Symbol = addStaticVariableToClass("reflPoly$Cache", SoftReferenceClass.tpe, mkNewPolyCache, false)
def getPolyCache = fn(REF(reflPolyCacheSym), nme.get) AS_ATTR MethodCacheClass.tpe
addStaticMethodToClass("reflMethod$Method", List(ClassClass.tpe), MethodClass.tpe)
{ case Pair(reflMethodSym, List(forReceiverSym)) =>
val methodSym = reflMethodSym.newVariable(ad.pos, mkTerm("method")) setInfo MethodClass.tpe
BLOCK(
IF (getPolyCache ANY_EQ NULL) THEN (REF(reflPolyCacheSym) === mkNewPolyCache) ENDIF,
VAL(methodSym) === ((getPolyCache DOT methodCache_find)(REF(forReceiverSym))) ,
IF (REF(methodSym) OBJ_!= NULL) .
THEN (Return(REF(methodSym)))
ELSE {
def methodSymRHS = ((REF(forReceiverSym) DOT Class_getMethod)(LIT(method), REF(reflParamsCacheSym)))
def cacheRHS = ((getPolyCache DOT methodCache_add)(REF(forReceiverSym), REF(methodSym)))
BLOCK(
REF(methodSym) === methodSymRHS,
REF(reflPolyCacheSym) === gen.mkSoftRef(cacheRHS),
Return(REF(methodSym))
)
}
)
}
}
/* ### HANDLING METHODS NORMALLY COMPILED TO OPERATORS ### */
val testForNumber: Tree = (qual IS_OBJ BoxedNumberClass.tpe) OR (qual IS_OBJ BoxedCharacterClass.tpe)
val testForBoolean: Tree = (qual IS_OBJ BoxedBooleanClass.tpe)
val testForNumberOrBoolean = testForNumber OR testForBoolean
val getPrimitiveReplacementForStructuralCall: PartialFunction[Name, (Symbol, Tree)] = {
val testsForNumber = Map() ++ List(
nme.UNARY_+ -> "positive",
nme.UNARY_- -> "negate",
nme.UNARY_~ -> "complement",
nme.ADD -> "add",
nme.SUB -> "subtract",
nme.MUL -> "multiply",
nme.DIV -> "divide",
nme.MOD -> "takeModulo",
nme.LSL -> "shiftSignedLeft",
nme.LSR -> "shiftLogicalRight",
nme.ASR -> "shiftSignedRight",
nme.LT -> "testLessThan",
nme.LE -> "testLessOrEqualThan",
nme.GE -> "testGreaterOrEqualThan",
nme.GT -> "testGreaterThan",
nme.toByte -> "toByte",
nme.toShort -> "toShort",
nme.toChar -> "toCharacter",
nme.toInt -> "toInteger",
nme.toLong -> "toLong",
nme.toFloat -> "toFloat",
nme.toDouble-> "toDouble"
)
val testsForBoolean = Map() ++ List(
nme.UNARY_! -> "takeNot",
nme.ZOR -> "takeConditionalOr",
nme.ZAND -> "takeConditionalAnd"
)
val testsForNumberOrBoolean = Map() ++ List(
nme.OR -> "takeOr",
nme.XOR -> "takeXor",
nme.AND -> "takeAnd",
nme.EQ -> "testEqual",
nme.NE -> "testNotEqual"
)
def get(name: String) = getMember(BoxesRunTimeClass, name)
/** Begin partial function. */
{
case x if testsForNumber contains x => (get(testsForNumber(x)), testForNumber)
case x if testsForBoolean contains x => (get(testsForBoolean(x)), testForBoolean)
case x if testsForNumberOrBoolean contains x => (get(testsForNumberOrBoolean(x)), testForNumberOrBoolean)
}
}
/* ### BOXING PARAMS & UNBOXING RESULTS ### */
/* Transforms the result of a reflective call (always an AnyRef) to
* the actual result value (an AnyRef too). The transformation
* depends on the method's static return type.
* - for units (void), the reflective call will return null: a new
* boxed unit is generated.
* - otherwise, the value is simply casted to the expected type. This
* is enough even for value (int et al.) values as the result of
* a dynamic call will box them as a side-effect. */
/* ### CALLING THE APPLY ### */
def callAsReflective(paramTypes: List[Type], resType: Type, structResType: Type): Tree = localTyper typed {
def fixResult(tree: Tree): Tree = localTyper typed {
structResType.typeSymbol match {
case UnitClass => BLOCK(tree, REF(BoxedUnit_UNIT))
case ObjectClass => tree
case _ => tree AS_ATTR structResType
}
}
val qualSym = qual.tpe.typeSymbol
val methSym = ad.symbol
def args = qual :: params
/** Normal non-Array call */
def defaultCall = {
// reflective method call machinery
val invokeName = MethodClass.tpe member nme.invoke_ // reflect.Method.invoke(...)
def cache = REF(reflectiveMethodCache(ad.symbol.name.toString, paramTypes)) // cache Symbol
def lookup = Apply(cache, List(qual GETCLASS)) // get Method object from cache
def invokeArgs = ArrayValue(TypeTree(ObjectClass.tpe), params) // args for invocation
def invocation = (lookup DOT invokeName)(qual, invokeArgs) // .invoke(qual, ...)
// exception catching machinery
val invokeExc = currentOwner.newValue(ad.pos, mkTerm()) setInfo InvocationTargetExceptionClass.tpe
def catchVar = Bind(invokeExc, Typed(Ident(nme.WILDCARD), TypeTree(InvocationTargetExceptionClass.tpe)))
def catchBody = Throw(Apply(Select(Ident(invokeExc), nme.getCause), Nil))
// try { method.invoke } catch { case e: InvocationTargetExceptionClass => throw e.getCause() }
fixResult( TRY (invocation) CATCH { CASE (catchVar) ==> catchBody } ENDTRY )
}
def useValueOperator =
isMaybeBoxed(qualSym) && // may be a boxed value class
(getPrimitiveReplacementForStructuralCall isDefinedAt methSym.name) &&
((resType :: paramTypes) forall (x => isJavaValueClass(x.typeSymbol))) // issue #1110
def isArrayMethodSignature =
(methSym.name == nme.length && params.isEmpty) ||
(methSym.name == nme.update && (structResType.typeSymbol eq UnitClass)) ||
(methSym.name == nme.apply && params.size == 1) ||
(methSym.name == nme.clone_ && params.isEmpty)
def isDefinitelyArray = isArrayMethodSignature && (qualSym == ArrayClass)
def isMaybeArray = isArrayMethodSignature && (qualSym == ObjectClass) // precondition: !isDefinitelyArray
def genArrayCall = methSym.name match {
case nme.length => REF(boxMethod(IntClass)) APPLY (REF(arrayLengthMethod) APPLY args)
case nme.update => REF(arrayUpdateMethod) APPLY List(args(0), (REF(unboxMethod(IntClass)) APPLY args(1)), args(2))
case nme.apply => REF(arrayApplyMethod) APPLY List(args(0), (REF(unboxMethod(IntClass)) APPLY args(1)))
case nme.clone_ => REF(arrayCloneMethod) APPLY List(args(0))
}
def genArrayTest = {
def oneTest(s: Symbol) = qual IS_OBJ arrayType(s.tpe)
OR((ObjectClass :: ScalaValueClasses filterNot (_ eq UnitClass)) map oneTest: _*)
}
val callCode =
if (useValueOperator) {
val (operator, test) = getPrimitiveReplacementForStructuralCall(methSym.name)
IF (test) THEN fixResult(REF(operator) APPLY args) ELSE defaultCall
}
else if (isDefinitelyArray) genArrayCall
else if (isMaybeArray) IF (genArrayTest) THEN genArrayCall ELSE defaultCall
else defaultCall
localTyper typed callCode
}
if (settings.refinementMethodDispatch.value == "invoke-dynamic") {
/* val guardCallSite: Tree = {
val cachedClass = addStaticVariableToClass("cachedClass", definitions.ClassClass.tpe, EmptyTree)
val tmpVar = currentOwner.newVariable(ad.pos, unit.fresh.newName(ad.pos, "x")).setInfo(definitions.AnyRefClass.tpe)
atPos(ad.pos)(Block(List(
ValDef(tmpVar, transform(qual))),
If(Apply(Select(gen.mkAttributedRef(cachedClass), nme.EQ), List(getClass(Ident(tmpVar)))),
Block(List(Assign(gen.mkAttributedRef(cachedClass), getClass(Ident(tmpVar)))),
treeCopy.ApplyDynamic(ad, Ident(tmpVar), transformTrees(params))),
EmptyTree)))
}
//println(guardCallSite)
*/
localTyper.typed(treeCopy.ApplyDynamic(ad, transform(qual), transformTrees(params)))
}
else {
/* ### BODY OF THE TRANSFORMATION -> remember we're in case ad@ApplyDynamic(qual, params) ### */
/* This creates the tree that does the reflective call (see general comment
* on the apply-dynamic tree for its format). This tree is simply composed
* of three succesive calls, first to getClass on the callee, then to
* getMethod on the classs, then to invoke on the method.
* - getMethod needs an array of classes for choosing one amongst many
* overloaded versions of the method. This is provided by paramTypeClasses
* and must be done on the static type as Scala's dispatching is static on
* the parameters.
* - invoke needs an array of AnyRefs that are the method's arguments. The
* erasure phase guarantees that any parameter passed to a dynamic apply
* is compatible (through boxing). Boxed ints et al. is what invoke expects
* when the applied method expects ints, hence no change needed there.
* - in the end, the result of invoke must be fixed, again to deal with arrays.
* This is provided by fixResult. fixResult will cast the invocation's result
* to the method's return type, which is generally ok, except when this type
* is a value type (int et al.) in which case it must cast to the boxed version
* because invoke only returns object and erasure made sure the result is
* expected to be an AnyRef. */
val t: Tree = ad.symbol.tpe match {
case MethodType(mparams, resType) =>
assert(params.length == mparams.length)
typedPos {
val sym = currentOwner.newValue(ad.pos, mkTerm("qual")) setInfo qual0.tpe
qual = REF(sym)
def structResType = if (isJavaValueClass(resType.typeSymbol)) boxedClass(resType.typeSymbol).tpe else resType
BLOCK(
VAL(sym) === qual0,
callAsReflective(mparams map (_.tpe), resType, structResType)
)
}
}
/* For testing purposes, the dynamic application's condition
* can be printed-out in great detail. Remove? */
if (settings.debug.value) {
def paramsToString(xs: Any*) = xs map (_.toString) mkString ", "
val mstr = ad.symbol.tpe match {
case MethodType(mparams, resType) =>
"""| with
| - declared parameter types: '%s'
| - passed argument types: '%s'
| - result type: '%s'""" .
stripMargin.format(
paramsToString(mparams),
paramsToString(params),
resType.toString
)
case _ => ""
}
Console.printf("""Dynamically application '%s.%s(%s)' %s - resulting code: '%s'""",
List(qual, ad.symbol.name, paramsToString(params), mstr, t) map (_.toString) : _*
)
}
/* We return the dynamic call tree, after making sure no other
* clean-up transformation are to be applied on it. */
transform(t)
}
/* ### END OF DYNAMIC APPLY TRANSFORM ### */
/* Some cleanup transformations add members to templates (classes, traits, etc).
* When inside a template (i.e. the body of one of its members), two maps
* (newDefs and newInits) are available in the tree transformer. Any mapping from
* a symbol to a MemberDef (DefDef, ValDef, etc.) that is in newDefs once the
* transformation of the template is finished will be added as a member to the
* template. Any mapping from a symbol to a tree that is in newInits, will be added
* as a statement of the form "symbol = tree" to the beginning of the default
* constructor. */
case Template(parents, self, body) =>
localTyper = typer.atOwner(tree, currentClass)
val transformedTemplate = if (!forMSIL) {
classConstantMeth.clear
newDefs.clear
newInits.clear
var newBody =
transformTrees(body)
val firstConstructor =
treeInfo.firstConstructor(newBody)
newBody =
transformTrees(newDefs.toList) ::: (
for (member <- newBody) yield member match {
case thePrimaryConstructor@DefDef(mods, name, tparams, vparamss, tpt, rhs) if (thePrimaryConstructor == firstConstructor) =>
val newRhs = rhs match {
case theRhs@Block(stats, expr) =>
treeCopy.Block(theRhs, transformTrees(newInits.toList) ::: stats, expr)
}
treeCopy.DefDef(thePrimaryConstructor, mods, name, tparams, vparamss, tpt, newRhs)
case notThePrimaryConstructor =>
notThePrimaryConstructor
}
)
treeCopy.Template(tree, parents, self, newBody)
}
else super.transform(tree)
applySymbolFieldInitsToStaticCtor(transformedTemplate.asInstanceOf[Template]) // postprocess to include static ctors
case Literal(c) if (c.tag == ClassTag) && !forMSIL=>
val tpe = c.typeValue
typedWithPos(tree.pos) {
if (isValueClass(tpe.typeSymbol)) {
if (tpe.typeSymbol == UnitClass)
Select(REF(BoxedUnit_TYPE), BoxedUnit_TYPE)
else
Select(REF(boxedModule(tpe.typeSymbol)), nme.TYPE_)
}
else tree
}
/* MSIL requires that the stack is empty at the end of a try-block.
* Hence, we here rewrite all try blocks with a result != {Unit, All} such that they
* store their result in a local variable. The catch blocks are adjusted as well.
* The try tree is subsituted by a block whose result expression is read of that variable. */
case theTry @ Try(block, catches, finalizer)
if theTry.tpe.typeSymbol != definitions.UnitClass && theTry.tpe.typeSymbol != definitions.NothingClass =>
val tpe = theTry.tpe.widen
val tempVar = currentOwner.newValue(theTry.pos, unit.fresh.newName(theTry.pos, "exceptionResult"))
.setInfo(tpe).setFlag(Flags.MUTABLE)
def assignBlock(rhs: Tree) = super.transform(BLOCK(Ident(tempVar) === transform(rhs)))
val newBlock = assignBlock(block)
val newCatches = for (CaseDef(pattern, guard, body) <- catches) yield
(CASE(super.transform(pattern)) IF (super.transform(guard))) ==> assignBlock(body)
val newTry = Try(newBlock, newCatches, super.transform(finalizer))
localTyper typed { BLOCK(VAL(tempVar) === EmptyTree, newTry, Ident(tempVar)) }
/* Adds @serializable annotation to anonymous function classes */
case cdef @ ClassDef(mods, name, tparams, impl) =>
if (settings.target.value == "jvm-1.5") {
val sym = cdef.symbol
// is this an anonymous function class?
if (sym.isAnonymousFunction && !sym.hasAnnotation(SerializableAttr)) {
sym addAnnotation serializableAnnotation
sym addAnnotation serialVersionUIDAnnotation
}
}
super.transform(tree)
/*
* This transformation should identify Scala symbol invocations in the tree and replace them
* with references to a static member. Also, whenever a class has at least a single symbol invocation
* somewhere in its methods, a new static member should be created and initialized for that symbol.
* For instance, say we have a Scala class:
*
* class Cls {
* // ...
* def someSymbol = `symbolic
* // ...
* }
*
* After transformation, this class looks like this:
*
* class Cls {
* private "static" val <some_name>$symbolic = Symbol("symbolic")
* // ...
* def someSymbol = <some_name>$symbolic
* // ...
* }
*
* The reasoning behind this transformation is the following. Symbols get interned - they are stored
* in a global map which is protected with a lock. The reason for this is making equality checks
* quicker. But calling Symbol.apply, although it does return a unique symbol, accesses a locked object,
* making symbol access slow. To solve this, the unique symbol from the global symbol map in Symbol
* is accessed only once during class loading, and after that, the unique symbol is in the static
* member. Hence, it is cheap to both reach the unique symbol and do equality checks on it.
*
* And, finally, be advised - scala symbol literal and the Symbol class of the compiler
* have little in common.
*/
case symapp @ Apply(Select(Select(a @ Ident(nme.scala_), b @ nme.Symbol), nme.apply),
List(Literal(Constant(symname: String)))) =>
// add the symbol name to a map if it's not there already
val rhs = gen.mkCast(Apply(gen.scalaDot(nme.Symbol), List(Literal(Constant(symname)))), symbolType)
val (staticFieldSym, sfdef, sfinit) = getSymbolStaticField(symapp.pos, symname, rhs, symapp)
// create a reference to a static field
val ntree = typedWithPos(symapp.pos)(REF(staticFieldSym))
super.transform(ntree)
case _ =>
super.transform(tree)
}
/* Returns the symbol and the tree for the symbol field interning a reference to a symbol 'synmname'.
* If it doesn't exist, i.e. the symbol is encountered the first time,
* it creates a new static field definition and initalization and returns it.
*/
private def getSymbolStaticField(pos: Position, symname: String, rhs: Tree, tree: Tree): (Symbol, Tree, Tree) =
symbolStaticFields.getOrElseUpdate(symname, {
val freshname = unit.fresh.newName(pos, "symbol$")
val theTyper = typer.atOwner(tree, currentClass)
// create a symbol for the static field
val stfieldSym = currentClass.newVariable(pos, freshname)
.setFlag(PRIVATE | STATIC | SYNTHETIC | FINAL)
.setInfo(symbolType)
currentClass.info.decls enter stfieldSym
// create field definition and initialization
val stfieldDef = theTyper.typed { atPos(pos)(VAL(stfieldSym) === rhs) }
val stfieldInit = theTyper.typed { atPos(pos)(REF(stfieldSym) === rhs) }
// add field definition to new defs
newDefs append stfieldDef
(stfieldSym, stfieldDef, stfieldInit)
})
/* returns a list of all trees for symbol static fields, and clear the list */
private def flushSymbolFieldsInitializations: List[Tree] = {
val fields = (symbolStaticFields.valuesIterator map (_._3)).toList
symbolStaticFields.clear
fields
}
/* finds the static ctor DefDef tree within the template if it exists. */
def findStaticCtor(template: Template): Option[Tree] =
template.body find {
case defdef @ DefDef(mods, nme.CONSTRUCTOR, tparam, vparam, tp, rhs) => defdef.symbol hasFlag STATIC
case _ => false
}
/* changes the template for the class so that it contains a static constructor with symbol fields inits,
* augments an existing static ctor if one already existed.
*/
def applySymbolFieldInitsToStaticCtor(template: Template): Template = {
val symbolInitTrees = flushSymbolFieldsInitializations
if (symbolInitTrees.isEmpty) template
else {
val theTyper = typer.atOwner(template, currentClass)
val newCtor = findStaticCtor(template) match {
// in case there already were static ctors - augment existing ones
// currently, however, static ctors aren't being generated anywhere else
case Some(ctor @ DefDef(mods, name, tparams, vparamss, tpt, rhs)) =>
// modify existing static ctor
val newBlock = rhs match {
case block @ Block(stats, expr) =>
// need to add inits to existing block
treeCopy.Block(block, symbolInitTrees ::: stats, expr)
case term: TermTree =>
// need to create a new block with inits and the old term
treeCopy.Block(term, symbolInitTrees, term)
}
treeCopy.DefDef(ctor, mods, name, tparams, vparamss, tpt, newBlock)
case None =>
// create new static ctor
val staticCtorSym = currentClass.newConstructor(template.pos)
.setFlag(STATIC)
.setInfo(UnitClass.tpe)
val rhs = Block(symbolInitTrees, Literal(()))
val staticCtorTree = DefDef(staticCtorSym, rhs)
theTyper.typed { atPos(template.pos)(staticCtorTree) }
}
treeCopy.Template(template, template.parents, template.self, newCtor :: template.body)
}
}
} // CleanUpTransformer
}
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