Scala example source code file (Erasure.scala)
The Scala Erasure.scala source code/* NSC -- new Scala compiler
* Copyright 2005-2011 LAMP/EPFL
* @author Martin Odersky
*/
package scala.tools.nsc
package transform
import scala.tools.nsc.symtab.classfile.ClassfileConstants._
import scala.collection.{ mutable, immutable }
import symtab._
import Flags._
abstract class Erasure extends AddInterfaces
with typechecker.Analyzer
with TypingTransformers
with ast.TreeDSL
{
import global._
import definitions._
import CODE._
val phaseName: String = "erasure"
def newTransformer(unit: CompilationUnit): Transformer =
new ErasureTransformer(unit)
override def keepsTypeParams = false
// -------- erasure on types --------------------------------------------------------
/** An extractor object for generic arrays */
object GenericArray {
/** Is `tp` an unbounded generic type (i.e. which could be instantiated
* with primitive as well as class types)?.
*/
private def genericCore(tp: Type): Type = tp.normalize match {
case TypeRef(_, sym, _) if sym.isAbstractType && !sym.owner.isJavaDefined =>
tp
case ExistentialType(tparams, restp) =>
genericCore(restp)
case _ =>
NoType
}
/** If `tp` is of the form Array[...Array[T]...] where `T` is an abstract type
* then Some(N, T) where N is the number of Array constructors enclosing `T`,
* otherwise None. Existentials on any level are ignored.
*/
def unapply(tp: Type): Option[(Int, Type)] = tp.normalize match {
case TypeRef(_, ArrayClass, List(arg)) =>
genericCore(arg) match {
case NoType =>
unapply(arg) match {
case Some((level, core)) => Some((level + 1, core))
case None => None
}
case core =>
Some(1, core)
}
case ExistentialType(tparams, restp) =>
unapply(restp)
case _ =>
None
}
}
// A type function from T => Class[U], used to determine the return
// type of getClass calls. The returned type is:
//
// 1. If T is a value type, Class[T].
// 2. If T is anonymous or a refinement type, calculate the intersection
// dominator of the parents T', and Class[_ <: T'].
// 3. If T is a phantom type (Any or AnyVal), Class[_].
// 4. Otherwise, Class[_ <: T].
//
// Note: AnyVal cannot be Class[_ <: AnyVal] because if the static type of the
// receiver is AnyVal, it implies the receiver is boxed, so the correct
// class object is that of java.lang.Integer, not Int.
//
// TODO: If T is final, return type could be Class[T]. Should it?
def getClassReturnType(tp: Type): Type = {
def mkClass(targs: List[Type]) = typeRef(ClassClass.tpe.prefix, ClassClass, targs)
val tparams = ClassClass.typeParams
val sym = tp.typeSymbol
if (tparams.isEmpty) mkClass(Nil) // call must be coming post-erasure
else if (isValueClass(sym)) mkClass(List(tp.widen))
else if (sym.isLocalClass) getClassReturnType(erasure.intersectionDominator(tp.parents))
else {
val eparams = typeParamsToExistentials(ClassClass, tparams)
val upperBound = if (isPhantomClass(sym)) AnyClass.tpe else tp.widen
existentialAbstraction(
eparams,
mkClass(List(eparams.head setInfo TypeBounds.upper(upperBound) tpe))
)
}
}
private def unboundedGenericArrayLevel(tp: Type): Int = tp match {
case GenericArray(level, core) if !(core <:< AnyRefClass.tpe) => level
case _ => 0
}
// @M #2585 when generating a java generic signature that includes a selection of an inner class p.I, (p = `pre`, I = `cls`)
// must rewrite to p'.I, where p' refers to the class that directly defines the nested class I
// see also #2585 marker in javaSig: there, type arguments must be included (use pre.baseType(cls.owner))
// requires cls.isClass
@inline private def rebindInnerClass(pre: Type, cls: Symbol): Type =
if (cls.owner.isClass) cls.owner.tpe else pre // why not cls.isNestedClass?
/** The erasure |T| of a type T. This is:
*
* - For a constant type, itself.
* - For a type-bounds structure, the erasure of its upper bound.
* - For every other singleton type, the erasure of its supertype.
* - For a typeref scala.Array+[T] where T is an abstract type, AnyRef.
* - For a typeref scala.Array+[T] where T is not an abstract type, scala.Array+[|T|].
* - For a typeref scala.Any or scala.AnyVal, java.lang.Object.
* - For a typeref scala.Unit, scala.runtime.BoxedUnit.
* - For a typeref P.C[Ts] where C refers to a class, |P|.C.
* (Where P is first rebound to the class that directly defines C.)
* - For a typeref P.C[Ts] where C refers to an alias type, the erasure of C's alias.
* - For a typeref P.C[Ts] where C refers to an abstract type, the
* erasure of C's upper bound.
* - For a non-empty type intersection (possibly with refinement),
* the erasure of its first parent.
* - For an empty type intersection, java.lang.Object.
* - For a method type (Fs)scala.Unit, (|Fs|)scala#Unit.
* - For any other method type (Fs)Y, (|Fs|)|T|.
* - For a polymorphic type, the erasure of its result type.
* - For the class info type of java.lang.Object, the same type without any parents.
* - For a class info type of a value class, the same type without any parents.
* - For any other class info type with parents Ps, the same type with
* parents |Ps|, but with duplicate references of Object removed.
* - for all other types, the type itself (with any sub-components erased)
*/
object erasure extends TypeMap {
// Compute the dominant part of the intersection type with given `parents` according to new spec.
def intersectionDominator(parents: List[Type]): Type =
if (parents.isEmpty) ObjectClass.tpe
else {
val psyms = parents map (_.typeSymbol)
if (psyms contains ArrayClass) {
// treat arrays specially
arrayType(
intersectionDominator(
parents filter (_.typeSymbol == ArrayClass) map (_.typeArgs.head)))
} else {
// implement new spec for erasure of refined types.
def isUnshadowed(psym: Symbol) =
!(psyms exists (qsym => (psym ne qsym) && (qsym isNonBottomSubClass psym)))
val cs = parents.iterator.filter { p => // isUnshadowed is a bit expensive, so try classes first
val psym = p.typeSymbol
psym.initialize
psym.isClass && !psym.isTrait && isUnshadowed(psym)
}
(if (cs.hasNext) cs else parents.iterator.filter(p => isUnshadowed(p.typeSymbol))).next()
}
}
def apply(tp: Type): Type = {
tp match {
case ConstantType(_) =>
tp
case st: SubType =>
apply(st.supertype)
case TypeRef(pre, sym, args) =>
if (sym == ArrayClass)
if (unboundedGenericArrayLevel(tp) == 1) ObjectClass.tpe
else if (args.head.typeSymbol == NothingClass || args.head.typeSymbol == NullClass) arrayType(ObjectClass.tpe)
else typeRef(apply(pre), sym, args map this)
else if (sym == AnyClass || sym == AnyValClass || sym == SingletonClass || sym == NotNullClass) erasedTypeRef(ObjectClass)
else if (sym == UnitClass) erasedTypeRef(BoxedUnitClass)
else if (sym.isRefinementClass) apply(intersectionDominator(tp.parents))
else if (sym.isClass) typeRef(apply(rebindInnerClass(pre, sym)), sym, List()) // #2585
else apply(sym.info) // alias type or abstract type
case PolyType(tparams, restpe) =>
apply(restpe)
case ExistentialType(tparams, restpe) =>
apply(restpe)
case mt @ MethodType(params, restpe) =>
MethodType(
cloneSymbols(params) map (p => p.setInfo(apply(p.tpe))),
if (restpe.typeSymbol == UnitClass)
erasedTypeRef(UnitClass)
else if (settings.YdepMethTpes.value)
// this replaces each typeref that refers to an argument by the type `p.tpe` of the actual argument p (p in params)
apply(mt.resultType(params map (_.tpe)))
else
apply(restpe))
case RefinedType(parents, decls) =>
apply(intersectionDominator(parents))
case AnnotatedType(_, atp, _) =>
apply(atp)
case ClassInfoType(parents, decls, clazz) =>
ClassInfoType(
if (clazz == ObjectClass || isValueClass(clazz)) Nil
else if (clazz == ArrayClass) List(erasedTypeRef(ObjectClass))
else removeDoubleObject(parents map this),
decls, clazz)
case _ =>
mapOver(tp)
}
}
}
private object NeedsSigCollector extends TypeCollector(false) {
def traverse(tp: Type) {
if (!result) {
tp match {
case st: SubType =>
traverse(st.supertype)
case TypeRef(pre, sym, args) =>
if (sym == ArrayClass) args foreach traverse
else if (sym.isTypeParameterOrSkolem || sym.isExistentiallyBound || !args.isEmpty) result = true
else if (sym.isClass) traverse(rebindInnerClass(pre, sym)) // #2585
else if (!sym.owner.isPackageClass) traverse(pre)
case PolyType(_, _) | ExistentialType(_, _) =>
result = true
case RefinedType(parents, decls) =>
if (!parents.isEmpty) traverse(parents.head)
case ClassInfoType(parents, _, _) =>
parents foreach traverse
case AnnotatedType(_, atp, _) =>
traverse(atp)
case _ =>
mapOver(tp)
}
}
}
}
private def needsJavaSig(tp: Type) = !settings.Ynogenericsig.value && NeedsSigCollector.collect(tp)
// only refer to type params that will actually make it into the sig, this excludes:
// * higher-order type parameters
// * type parameters appearing in method parameters
// * type members not visible in an enclosing template
private def isTypeParameterInSig(sym: Symbol, initialSymbol: Symbol) = (
!sym.isHigherOrderTypeParameter &&
sym.isTypeParameterOrSkolem && (
(initialSymbol.enclClassChain.exists(sym isNestedIn _)) ||
traceSig("isMethod", (initialSymbol, initialSymbol.typeParams)) {
(initialSymbol.isMethod && initialSymbol.typeParams.contains(sym))
}
)
)
// Ensure every '.' in the generated signature immediately follows
// a close angle bracket '>'. Any which do not are replaced with '$'.
// This arises due to multiply nested classes in the face of the
// rewriting explained at rebindInnerClass. This should be done in a
// more rigorous way up front rather than catching it after the fact,
// but that will be more involved.
private def dotCleanup(sig: String): String = {
var last: Char = '\0'
sig map {
case '.' if last != '>' => last = '.' ; '$'
case ch => last = ch ; ch
}
}
// for debugging signatures: traces logic given system property
private val traceProp = (sys.BooleanProp keyExists "scalac.sigs.trace").value // performance: get the value here
private val traceSig = util.Tracer(traceProp)
/** This object is only used for sanity testing when -check:genjvm is set.
* In that case we make sure that the erasure of the `normalized' type
* is the same as the erased type that's generated. Normalization means
* unboxing some primitive types and further simplifications as they are done in jsig.
*/
val prepareSigMap = new TypeMap {
def squashBoxed(tp: Type): Type = tp.normalize match {
case t @ RefinedType(parents, decls) =>
val parents1 = parents mapConserve squashBoxed
if (parents1 eq parents) tp
else RefinedType(parents1, decls)
case t @ ExistentialType(tparams, tpe) =>
val tpe1 = squashBoxed(tpe)
if (tpe1 eq tpe) t
else ExistentialType(tparams, tpe1)
case t =>
if (boxedClass contains t.typeSymbol) ObjectClass.tpe
else tp
}
def apply(tp: Type): Type = tp.normalize match {
case tp1 @ TypeBounds(lo, hi) =>
val lo1 = squashBoxed(apply(lo))
val hi1 = squashBoxed(apply(hi))
if ((lo1 eq lo) && (hi1 eq hi)) tp1
else TypeBounds(lo1, hi1)
case tp1 @ TypeRef(pre, sym, args) =>
def argApply(tp: Type) = {
val tp1 = apply(tp)
if (tp1.typeSymbol == UnitClass) ObjectClass.tpe
else squashBoxed(tp1)
}
if (sym == ArrayClass && args.nonEmpty)
if (unboundedGenericArrayLevel(tp1) == 1) ObjectClass.tpe
else mapOver(tp1)
else if (sym == AnyClass || sym == AnyValClass || sym == SingletonClass)
ObjectClass.tpe
else if (sym == UnitClass)
BoxedUnitClass.tpe
else if (sym == NothingClass)
RuntimeNothingClass.tpe
else if (sym == NullClass)
RuntimeNullClass.tpe
else {
val pre1 = apply(pre)
val args1 = args mapConserve argApply
if ((pre1 eq pre) && (args1 eq args)) tp1
else TypeRef(pre1, sym, args1)
}
case tp1 @ MethodType(params, restpe) =>
val params1 = mapOver(params)
val restpe1 = if (restpe.normalize.typeSymbol == UnitClass) UnitClass.tpe else apply(restpe)
if ((params1 eq params) && (restpe1 eq restpe)) tp1
else MethodType(params1, restpe1)
case tp1 @ RefinedType(parents, decls) =>
val parents1 = parents mapConserve apply
if (parents1 eq parents) tp1
else RefinedType(parents1, decls)
case t @ ExistentialType(tparams, tpe) =>
val tpe1 = apply(tpe)
if (tpe1 eq tpe) t
else ExistentialType(tparams, tpe1)
case tp1: ClassInfoType =>
tp1
case tp1 =>
mapOver(tp1)
}
}
/** The Java signature of type 'info', for symbol sym. The symbol is used to give the right return
* type for constructors.
*/
def javaSig(sym0: Symbol, info: Type): Option[String] = atPhase(currentRun.erasurePhase) {
def boxedSig(tp: Type) = jsig(tp, primitiveOK = false)
def hiBounds(bounds: TypeBounds): List[Type] = bounds.hi.normalize match {
case RefinedType(parents, _) => parents map normalize
case tp => tp :: Nil
}
def jsig(tp0: Type, existentiallyBound: List[Symbol] = Nil, toplevel: Boolean = false, primitiveOK: Boolean = true): String = {
val tp = tp0.dealias
tp match {
case st: SubType =>
jsig(st.supertype, existentiallyBound, toplevel, primitiveOK)
case ExistentialType(tparams, tpe) =>
jsig(tpe, tparams, toplevel, primitiveOK)
case TypeRef(pre, sym, args) =>
def argSig(tp: Type) =
if (existentiallyBound contains tp.typeSymbol) {
val bounds = tp.typeSymbol.info.bounds
if (!(AnyRefClass.tpe <:< bounds.hi)) "+" + boxedSig(bounds.hi)
else if (!(bounds.lo <:< NullClass.tpe)) "-" + boxedSig(bounds.lo)
else "*"
} else {
boxedSig(tp)
}
def classSig: String =
"L"+atPhase(currentRun.icodePhase)(sym.fullName + global.genJVM.moduleSuffix(sym)).replace('.', '/')
def classSigSuffix: String =
"."+sym.name
// If args isEmpty, Array is being used as a higher-kinded type
if (sym == ArrayClass && args.nonEmpty) {
if (unboundedGenericArrayLevel(tp) == 1) jsig(ObjectClass.tpe)
else ARRAY_TAG.toString+(args map (jsig(_))).mkString
}
else if (isTypeParameterInSig(sym, sym0)) {
assert(!sym.isAliasType, "Unexpected alias type: " + sym)
TVAR_TAG.toString+sym.name+";"
}
else if (sym == AnyClass || sym == AnyValClass || sym == SingletonClass)
jsig(ObjectClass.tpe)
else if (sym == UnitClass)
jsig(BoxedUnitClass.tpe)
else if (sym == NothingClass)
jsig(RuntimeNothingClass.tpe)
else if (sym == NullClass)
jsig(RuntimeNullClass.tpe)
else if (isValueClass(sym)) {
if (!primitiveOK) jsig(ObjectClass.tpe)
else if (sym == UnitClass) jsig(BoxedUnitClass.tpe)
else abbrvTag(sym).toString
}
else if (sym.isClass) {
val preRebound = pre.baseType(sym.owner) // #2585
traceSig("sym.isClass", (sym.ownerChain, preRebound, sym0.enclClassChain)) {
dotCleanup(
(
if (needsJavaSig(preRebound)) {
val s = jsig(preRebound, existentiallyBound)
if (s.charAt(0) == 'L') s.substring(0, s.length - 1) + classSigSuffix
else classSig
}
else classSig
) + (
if (args.isEmpty) "" else
"<"+(args map argSig).mkString+">"
) + (
";"
)
)
}
}
else jsig(erasure(tp), existentiallyBound, toplevel, primitiveOK)
case PolyType(tparams, restpe) =>
assert(tparams.nonEmpty)
def boundSig(bounds: List[Type]) = {
val (isTrait, isClass) = bounds partition (_.typeSymbol.isTrait)
":" + (
if (isClass.isEmpty) "" else boxedSig(isClass.head)
) + (
isTrait map (x => ":" + boxedSig(x)) mkString
)
}
def paramSig(tsym: Symbol) = tsym.name + boundSig(hiBounds(tsym.info.bounds))
val paramString = if (toplevel) tparams map paramSig mkString ("<", "", ">") else ""
traceSig("PolyType", (tparams, restpe))(paramString + jsig(restpe))
case MethodType(params, restpe) =>
"("+(params map (_.tpe) map (jsig(_))).mkString+")"+
(if (restpe.typeSymbol == UnitClass || sym0.isConstructor) VOID_TAG.toString else jsig(restpe))
case RefinedType(parent :: _, decls) =>
boxedSig(parent)
case ClassInfoType(parents, _, _) =>
(parents map (boxedSig(_))).mkString
case AnnotatedType(_, atp, _) =>
jsig(atp, existentiallyBound, toplevel, primitiveOK)
case BoundedWildcardType(bounds) =>
println("something's wrong: "+sym0+":"+sym0.tpe+" has a bounded wildcard type")
jsig(bounds.hi, existentiallyBound, toplevel, primitiveOK)
case _ =>
val etp = erasure(tp)
if (etp eq tp) throw new UnknownSig
else jsig(etp)
}
}
traceSig("javaSig", (sym0, info)) {
if (needsJavaSig(info)) {
try Some(jsig(info, toplevel = true))
catch { case ex: UnknownSig => None }
}
else None
}
}
class UnknownSig extends Exception
/** Type reference after erasure */
def erasedTypeRef(sym: Symbol): Type =
typeRef(erasure(sym.owner.tpe), sym, List())
/** Remove duplicate references to class Object in a list of parent classes */
private def removeDoubleObject(tps: List[Type]): List[Type] = tps match {
case List() => List()
case tp :: tps1 =>
if (tp.typeSymbol == ObjectClass) tp :: tps1.filter(_.typeSymbol != ObjectClass)
else tp :: removeDoubleObject(tps1)
}
/** The symbol's erased info. This is the type's erasure, except for the following symbols:
*
* - For $asInstanceOf : [T]T
* - For $isInstanceOf : [T]scala#Boolean
* - For class Array : [T]C where C is the erased classinfo of the Array class.
* - For Array[T].<init> : {scala#Int)Array[T]
* - For a type parameter : A type bounds type consisting of the erasures of its bounds.
*/
def transformInfo(sym: Symbol, tp: Type): Type = {
if (sym == Object_asInstanceOf)
sym.info
else if (sym == Object_isInstanceOf || sym == ArrayClass)
PolyType(sym.info.typeParams, erasure(sym.info.resultType))
else if (sym.isAbstractType)
TypeBounds(WildcardType, WildcardType)
else if (sym.isTerm && sym.owner == ArrayClass) {
if (sym.isClassConstructor)
tp match {
case MethodType(params, TypeRef(pre, sym, args)) =>
MethodType(cloneSymbols(params) map (p => p.setInfo(erasure(p.tpe))),
typeRef(erasure(pre), sym, args))
}
else if (sym.name == nme.apply)
tp
else if (sym.name == nme.update)
(tp: @unchecked) match {
case MethodType(List(index, tvar), restpe) =>
MethodType(List(index.cloneSymbol.setInfo(erasure(index.tpe)), tvar),
erasedTypeRef(UnitClass))
}
else erasure(tp)
} else if (
sym.owner != NoSymbol &&
sym.owner.owner == ArrayClass &&
sym == Array_update.paramss.head(1)) {
// special case for Array.update: the non-erased type remains, i.e. (Int,A)Unit
// since the erasure type map gets applied to every symbol, we have to catch the
// symbol here
tp
} else {
/*
val erased =
if (sym.isGetter && sym.tpe.isInstanceOf[MethodType])
erasure mapOver sym.tpe // for getters, unlike for normal methods, always convert Unit to BoxedUnit.
else
erasure(tp)
*/
transformMixinInfo(erasure(tp))
}
}
val deconstMap = new TypeMap {
def apply(tp: Type): Type = tp match {
case PolyType(_, _) => mapOver(tp)
case MethodType(_, _) => mapOver(tp) // nullarymethod was eliminated during uncurry
case _ => tp.deconst
}
}
// Methods on Any/Object which we rewrite here while we still know what
// is a primitive and what arrived boxed.
private lazy val interceptedMethods = Set[Symbol](Any_##, Object_##, Any_getClass) ++ (
// Each value class has its own getClass for ultra-precise class object typing.
ScalaValueClasses map (_.tpe member nme.getClass_)
)
// -------- erasure on trees ------------------------------------------
override def newTyper(context: Context) = new Eraser(context)
/** An extractor object for boxed expressions
object Boxed {
def unapply(tree: Tree): Option[Tree] = tree match {
case LabelDef(name, params, Boxed(rhs)) =>
Some(treeCopy.LabelDef(tree, name, params, rhs) setType rhs.tpe)
case Select(_, _) if tree.symbol == BoxedUnit_UNIT =>
Some(Literal(()) setPos tree.pos setType UnitClass.tpe)
case Block(List(unboxed), ret @ Select(_, _)) if ret.symbol == BoxedUnit_UNIT =>
Some(if (unboxed.tpe.typeSymbol == UnitClass) tree
else Block(List(unboxed), Literal(()) setPos tree.pos setType UnitClass.tpe))
case Apply(fn, List(unboxed)) if isBox(fn.symbol) =>
Some(unboxed)
case _ =>
None
}
}
*/
/** The modifier typer which retypes with erased types. */
class Eraser(context: Context) extends Typer(context) {
private def safeToRemoveUnbox(cls: Symbol): Boolean =
(cls == definitions.NullClass) || isBoxedValueClass(cls)
/** Box `tree' of unboxed type */
private def box(tree: Tree): Tree = tree match {
case LabelDef(name, params, rhs) =>
val rhs1 = box(rhs)
treeCopy.LabelDef(tree, name, params, rhs1) setType rhs1.tpe
case _ =>
typedPos(tree.pos)(tree.tpe.typeSymbol match {
case UnitClass =>
if (treeInfo isPureExpr tree) REF(BoxedUnit_UNIT)
else BLOCK(tree, REF(BoxedUnit_UNIT))
case NothingClass => tree // a non-terminating expression doesn't need boxing
case x =>
assert(x != ArrayClass)
tree match {
/** Can't always remove a Box(Unbox(x)) combination because the process of boxing x
* may lead to throwing an exception.
*
* This is important for specialization: calls to the super constructor should not box/unbox specialized
* fields (see TupleX). (ID)
*/
case Apply(boxFun, List(arg)) if isUnbox(tree.symbol) && safeToRemoveUnbox(arg.tpe.typeSymbol) =>
log("boxing an unbox: " + tree + " and replying with " + arg)
arg
case _ =>
(REF(boxMethod(x)) APPLY tree) setPos (tree.pos) setType ObjectClass.tpe
}
})
}
/** Unbox `tree` of boxed type to expected type `pt`.
*
* @param tree the given tree
* @param pt the expected type.
* @return the unboxed tree
*/
private def unbox(tree: Tree, pt: Type): Tree = tree match {
/*
case Boxed(unboxed) =>
println("unbox shorten: "+tree) // this never seems to kick in during build and test; therefore disabled.
adaptToType(unboxed, pt)
*/
case LabelDef(name, params, rhs) =>
val rhs1 = unbox(rhs, pt)
treeCopy.LabelDef(tree, name, params, rhs1) setType rhs1.tpe
case _ =>
typedPos(tree.pos)(pt.typeSymbol match {
case UnitClass =>
if (treeInfo isPureExpr tree) UNIT
else BLOCK(tree, UNIT)
case x =>
assert(x != ArrayClass)
(REF(unboxMethod(pt.typeSymbol)) APPLY tree) setType pt
})
}
/** Generate a synthetic cast operation from tree.tpe to pt.
* @pre pt eq pt.normalize
*/
private def cast(tree: Tree, pt: Type): Tree = {
if (pt.typeSymbol == UnitClass) {
// See SI-4731 for one example of how this occurs.
log("Attempted to cast to Unit: " + tree)
tree.duplicate setType pt
}
else tree AS_ATTR pt
}
private def isUnboxedValueMember(sym: Symbol) =
sym != NoSymbol && isValueClass(sym.owner)
/** Adapt `tree` to expected type `pt`.
*
* @param tree the given tree
* @param pt the expected type
* @return the adapted tree
*/
private def adaptToType(tree: Tree, pt: Type): Tree = {
if (settings.debug.value && pt != WildcardType)
log("adapting " + tree + ":" + tree.tpe + " : " + tree.tpe.parents + " to " + pt)//debug
if (tree.tpe <:< pt)
tree
else if (isValueClass(tree.tpe.typeSymbol) && !isValueClass(pt.typeSymbol))
adaptToType(box(tree), pt)
else if (tree.tpe.isInstanceOf[MethodType] && tree.tpe.params.isEmpty) {
assert(tree.symbol.isStable, "adapt "+tree+":"+tree.tpe+" to "+pt)
adaptToType(Apply(tree, List()) setPos tree.pos setType tree.tpe.resultType, pt)
} else if (pt <:< tree.tpe)
cast(tree, pt)
else if (isValueClass(pt.typeSymbol) && !isValueClass(tree.tpe.typeSymbol))
adaptToType(unbox(tree, pt), pt)
else
cast(tree, pt)
}
// @PP 1/25/2011: This is less inaccurate than it was (I removed
// BoxedAnyArray, asInstanceOf$erased, and other long ago eliminated symbols)
// but I do not think it yet describes the code beneath it.
/** Replace member references as follows:
*
* - `x == y` for == in class Any becomes `x equals y` with equals in class Object.
* - `x != y` for != in class Any becomes `!(x equals y)` with equals in class Object.
* - x.asInstanceOf[T] becomes x.$asInstanceOf[T]
* - x.isInstanceOf[T] becomes x.$isInstanceOf[T]
* - x.m where m is some other member of Any becomes x.m where m is a member of class Object.
* - x.m where x has unboxed value type T and m is not a directly translated member of T becomes T.box(x).m
* - x.m where x is a reference type and m is a directly translated member of value type T becomes x.TValue().m
* - All forms of x.m where x is a boxed type and m is a member of an unboxed class become
* x.m where m is the corresponding member of the boxed class.
*/
private def adaptMember(tree: Tree): Tree = {
//Console.println("adaptMember: " + tree);
tree match {
case Apply(TypeApply(sel @ Select(qual, name), List(targ)), List()) if tree.symbol == Any_asInstanceOf =>
val qual1 = typedQualifier(qual, NOmode, ObjectClass.tpe) // need to have an expected type, see #3037
val qualClass = qual1.tpe.typeSymbol
val targClass = targ.tpe.typeSymbol
/*
if (isNumericValueClass(qualClass) && isNumericValueClass(targClass))
// convert numeric type casts
atPos(tree.pos)(Apply(Select(qual1, "to" + targClass.name), List()))
else
*/
if (isValueClass(targClass)) unbox(qual1, targ.tpe)
else tree
case Select(qual, name) if (name != nme.CONSTRUCTOR) =>
if (tree.symbol == NoSymbol)
tree
else if (tree.symbol == Any_asInstanceOf)
adaptMember(atPos(tree.pos)(Select(qual, Object_asInstanceOf)))
else if (tree.symbol == Any_isInstanceOf)
adaptMember(atPos(tree.pos)(Select(qual, Object_isInstanceOf)))
else if (tree.symbol.owner == AnyClass)
adaptMember(atPos(tree.pos)(Select(qual, getMember(ObjectClass, name))))
else {
var qual1 = typedQualifier(qual)
if ((isValueClass(qual1.tpe.typeSymbol) && !isUnboxedValueMember(tree.symbol)))
qual1 = box(qual1)
else if (!isValueClass(qual1.tpe.typeSymbol) && isUnboxedValueMember(tree.symbol))
qual1 = unbox(qual1, tree.symbol.owner.tpe)
if (isValueClass(tree.symbol.owner) && !isValueClass(qual1.tpe.typeSymbol))
tree.symbol = NoSymbol
else if (qual1.tpe.isInstanceOf[MethodType] && qual1.tpe.params.isEmpty) {
assert(qual1.symbol.isStable, qual1.symbol);
qual1 = Apply(qual1, List()) setPos qual1.pos setType qual1.tpe.resultType
} else if (!(qual1.isInstanceOf[Super] || (qual1.tpe.typeSymbol isSubClass tree.symbol.owner))) {
assert(tree.symbol.owner != ArrayClass)
qual1 = cast(qual1, tree.symbol.owner.tpe)
}
treeCopy.Select(tree, qual1, name)
}
case SelectFromArray(qual, name, erasure) =>
var qual1 = typedQualifier(qual)
if (!(qual1.tpe <:< erasure)) qual1 = cast(qual1, erasure)
Select(qual1, name) copyAttrs tree
case _ =>
tree
}
}
/** A replacement for the standard typer's adapt method.
*/
override protected def adapt(tree: Tree, mode: Int, pt: Type, original: Tree = EmptyTree): Tree =
adaptToType(tree, pt)
/** A replacement for the standard typer's `typed1' method.
*/
override protected def typed1(tree: Tree, mode: Int, pt: Type): Tree = {
val tree1 = try {
super.typed1(adaptMember(tree), mode, pt)
} catch {
case er: TypeError =>
Console.println("exception when typing " + tree)
Console.println(er.msg + " in file " + context.owner.sourceFile)
er.printStackTrace
abort()
case ex: Exception =>
//if (settings.debug.value)
Console.println("exception when typing " + tree);
throw ex
}
def adaptCase(cdef: CaseDef): CaseDef = {
val body1 = adaptToType(cdef.body, tree1.tpe)
treeCopy.CaseDef(cdef, cdef.pat, cdef.guard, body1) setType body1.tpe
}
def adaptBranch(branch: Tree): Tree =
if (branch == EmptyTree) branch else adaptToType(branch, tree1.tpe);
tree1 match {
case If(cond, thenp, elsep) =>
treeCopy.If(tree1, cond, adaptBranch(thenp), adaptBranch(elsep))
case Match(selector, cases) =>
treeCopy.Match(tree1, selector, cases map adaptCase)
case Try(block, catches, finalizer) =>
treeCopy.Try(tree1, adaptBranch(block), catches map adaptCase, finalizer)
case Ident(_) | Select(_, _) =>
if (tree1.symbol.isOverloaded) {
val first = tree1.symbol.alternatives.head
val sym1 = tree1.symbol.filter {
alt => alt == first || !(first.tpe looselyMatches alt.tpe)
}
if (tree.symbol ne sym1) {
tree1.symbol = sym1
tree1.tpe = sym1.tpe
}
}
tree1
case _ =>
tree1
}
}
}
/** The erasure transformer */
class ErasureTransformer(unit: CompilationUnit) extends Transformer {
/** Emit an error if there is a double definition. This can happen if:
*
* - A template defines two members with the same name and erased type.
* - A template defines and inherits two members `m` with different types,
* but their erased types are the same.
* - A template inherits two members `m` with different types,
* but their erased types are the same.
*/
private def checkNoDoubleDefs(root: Symbol) {
def doubleDefError(sym1: Symbol, sym2: Symbol) {
// the .toString must also be computed at the earlier phase
def atRefc[T](op: => T) = atPhase[T](currentRun.refchecksPhase.next)(op)
val tpe1 = atRefc(root.thisType.memberType(sym1))
val tpe2 = atRefc(root.thisType.memberType(sym2))
if (!tpe1.isErroneous && !tpe2.isErroneous)
unit.error(
if (sym1.owner == root) sym1.pos else root.pos,
(if (sym1.owner == sym2.owner) "double definition:\n"
else if (sym1.owner == root) "name clash between defined and inherited member:\n"
else "name clash between inherited members:\n") +
sym1 + ":" + atRefc(tpe1.toString) +
(if (sym1.owner == root) "" else sym1.locationString) + " and\n" +
sym2 + ":" + atRefc(tpe2.toString) +
(if (sym2.owner == root) " at line " + (sym2.pos).line else sym2.locationString) +
"\nhave same type" +
(if (atRefc(tpe1 =:= tpe2)) "" else " after erasure: " + atPhase(phase.next)(sym1.tpe)))
sym1.setInfo(ErrorType)
}
val decls = root.info.decls
var e = decls.elems
while (e ne null) {
if (e.sym.isTerm) {
var e1 = decls.lookupNextEntry(e)
while (e1 ne null) {
if (atPhase(phase.next)(e1.sym.info =:= e.sym.info)) doubleDefError(e.sym, e1.sym)
e1 = decls.lookupNextEntry(e1)
}
}
e = e.next
}
val opc = new overridingPairs.Cursor(root) {
override def exclude(sym: Symbol): Boolean =
(!sym.isTerm || sym.isPrivate || super.exclude(sym)
// specialized members have no type history before 'specialize', causing double def errors for curried defs
|| !sym.hasTypeAt(currentRun.refchecksPhase.id))
override def matches(sym1: Symbol, sym2: Symbol): Boolean =
atPhase(phase.next)(sym1.tpe =:= sym2.tpe)
}
while (opc.hasNext) {
if (!atPhase(currentRun.refchecksPhase.next)(
root.thisType.memberType(opc.overriding) matches
root.thisType.memberType(opc.overridden))) {
if (settings.debug.value)
log("" + opc.overriding.locationString + " " +
opc.overriding.infosString +
opc.overridden.locationString + " " +
opc.overridden.infosString)
doubleDefError(opc.overriding, opc.overridden)
}
opc.next
}
}
/*
for (bc <- root.info.baseClasses.tail; other <- bc.info.decls.toList) {
if (other.isTerm && !other.isConstructor && !(other hasFlag (PRIVATE | BRIDGE))) {
for (member <- root.info.nonPrivateMember(other.name).alternatives) {
if (member != other &&
!(member hasFlag BRIDGE) &&
atPhase(phase.next)(member.tpe =:= other.tpe) &&
!atPhase(refchecksPhase.next)(
root.thisType.memberType(member) matches root.thisType.memberType(other))) {
if (settings.debug.value) log("" + member.locationString + " " + member.infosString + other.locationString + " " + other.infosString);
doubleDefError(member, other)
}
}
}
}
*/
/** Add bridge definitions to a template. This means:
*
* If there is a concrete member `m` which overrides a member in a base
* class of the template, and the erased types of the two members differ,
* and the two members are not inherited or defined by some parent class
* of the template, then a bridge from the overridden member `m1` to the
* member `m0` is added. The bridge has the erased type of `m1` and
* forwards to `m0`.
*
* No bridge is added if there is already a bridge to `m0` with the erased
* type of `m1` in the template.
*/
private def bridgeDefs(owner: Symbol): (List[Tree], immutable.Set[Symbol]) = {
var toBeRemoved: immutable.Set[Symbol] = immutable.Set()
//println("computing bridges for " + owner)//DEBUG
assert(phase == currentRun.erasurePhase)
val site = owner.thisType
val bridgesScope = new Scope
val bridgeTarget = new mutable.HashMap[Symbol, Symbol]
var bridges: List[Tree] = List()
val opc = atPhase(currentRun.explicitouterPhase) {
new overridingPairs.Cursor(owner) {
override def parents: List[Type] = List(owner.info.parents.head)
override def exclude(sym: Symbol): Boolean =
!sym.isMethod || sym.isPrivate || super.exclude(sym)
}
}
while (opc.hasNext) {
val member = opc.overriding
val other = opc.overridden
//Console.println("bridge? " + member + ":" + member.tpe + member.locationString + " to " + other + ":" + other.tpe + other.locationString)//DEBUG
if (atPhase(currentRun.explicitouterPhase)(!member.isDeferred)) {
val otpe = erasure(other.tpe)
val bridgeNeeded = atPhase(phase.next) (
!(other.tpe =:= member.tpe) &&
!(deconstMap(other.tpe) =:= deconstMap(member.tpe)) &&
{ var e = bridgesScope.lookupEntry(member.name)
while ((e ne null) && !((e.sym.tpe =:= otpe) && (bridgeTarget(e.sym) == member)))
e = bridgesScope.lookupNextEntry(e)
(e eq null)
}
);
if (bridgeNeeded) {
val bridge = other.cloneSymbolImpl(owner)
.setPos(owner.pos)
.setFlag(member.flags | BRIDGE)
.resetFlag(ACCESSOR | DEFERRED | LAZY | lateDEFERRED)
// the parameter symbols need to have the new owner
bridge.setInfo(otpe.cloneInfo(bridge))
bridgeTarget(bridge) = member
atPhase(phase.next) { owner.info.decls.enter(bridge) }
if (other.owner == owner) {
//println("bridge to same: "+other+other.locationString)//DEBUG
atPhase(phase.next) { owner.info.decls.unlink(other) }
toBeRemoved += other
}
bridgesScope enter bridge
bridges =
atPhase(phase.next) {
atPos(bridge.pos) {
val bridgeDef =
DefDef(bridge,
member.tpe match {
case MethodType(List(), ConstantType(c)) => Literal(c)
case _ =>
(((Select(This(owner), member): Tree) /: bridge.paramss)
((fun, vparams) => Apply(fun, vparams map Ident)))
});
if (settings.debug.value)
log("generating bridge from " + other + "(" + Flags.flagsToString(bridge.flags) + ")" + ":" + otpe + other.locationString + " to " + member + ":" + erasure(member.tpe) + member.locationString + " =\n " + bridgeDef);
bridgeDef
}
} :: bridges
}
}
opc.next
}
(bridges, toBeRemoved)
}
/*
for (bc <- site.baseClasses.tail; other <- bc.info.decls.toList) {
if (other.isMethod && !other.isConstructor) {
for (member <- site.nonPrivateMember(other.name).alternatives) {
if (member != other &&
!(member hasFlag DEFERRED) &&
(site.memberType(member) matches site.memberType(other)) &&
!(site.parents exists (p =>
(p.symbol isSubClass member.owner) && (p.symbol isSubClass other.owner)))) {
...
}
}
*/
def addBridges(stats: List[Tree], base: Symbol): List[Tree] =
if (base.isTrait) stats
else {
val (bridges, toBeRemoved) = bridgeDefs(base)
if (bridges.isEmpty) stats
else (stats filterNot (stat => toBeRemoved contains stat.symbol)) ::: bridges
}
/** Transform tree at phase erasure before retyping it.
* This entails the following:
*
* - Remove all type parameters in class and method definitions.
* - Remove all abstract and alias type definitions.
* - Remove all type applications other than those involving a type test or cast.
* - Remove all empty trees in statements and definitions in a PackageDef.
* - Check that there are no double definitions in a template.
* - Add bridge definitions to a template.
* - Replace all types in type nodes and the EmptyTree object by their erasure.
* Type nodes of type Unit representing result types of methods are left alone.
* - Given a selection q.s, where the owner of `s` is not accessible but the
* type symbol of q's type qT is accessible, insert a cast (q.asInstanceOf[qT]).s
* This prevents illegal access errors (see #4283).
* - Reset all other type attributes to null, thus enforcing a retyping.
*/
private val preTransformer = new TypingTransformer(unit) {
def preErase(tree: Tree): Tree = tree match {
case ClassDef(mods, name, tparams, impl) =>
if (settings.debug.value)
log("defs of " + tree.symbol + " = " + tree.symbol.info.decls)
treeCopy.ClassDef(tree, mods, name, List(), impl)
case DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
treeCopy.DefDef(tree, mods, name, List(), vparamss, tpt, rhs)
case TypeDef(_, _, _, _) =>
EmptyTree
case Apply(instanceOf @ TypeApply(fun @ Select(qual, name), args @ List(arg)), List()) // !!! todo: simplify by having GenericArray also extract trees
if ((fun.symbol == Any_isInstanceOf || fun.symbol == Object_isInstanceOf) &&
unboundedGenericArrayLevel(arg.tpe) > 0) =>
val level = unboundedGenericArrayLevel(arg.tpe)
def isArrayTest(arg: Tree) =
gen.mkRuntimeCall("isArray", List(arg, Literal(Constant(level))))
global.typer.typedPos(tree.pos) {
if (level == 1) isArrayTest(qual)
else
gen.evalOnce(qual, currentOwner, unit) { qual1 =>
gen.mkAnd(
Apply(TypeApply(Select(qual1(), fun.symbol),
List(TypeTree(erasure(arg.tpe)))),
List()),
isArrayTest(qual1()))
}
}
case TypeApply(fun, args) if (fun.symbol.owner != AnyClass &&
fun.symbol != Object_asInstanceOf &&
fun.symbol != Object_isInstanceOf) =>
// leave all other type tests/type casts, remove all other type applications
preErase(fun)
case Apply(fn @ Select(qual, name), args) if (fn.symbol.owner == ArrayClass) =>
if (unboundedGenericArrayLevel(qual.tpe.widen) == 1)
// convert calls to apply/update/length on generic arrays to
// calls of ScalaRunTime.array_xxx method calls
global.typer.typedPos(tree.pos) { gen.mkRuntimeCall("array_"+name, qual :: args) }
else
// store exact array erasure in map to be retrieved later when we might
// need to do the cast in adaptMember
treeCopy.Apply(
tree,
SelectFromArray(qual, name, erasure(qual.tpe)).copyAttrs(fn),
args)
case Apply(fn @ Select(qual, _), Nil) if interceptedMethods(fn.symbol) =>
if (fn.symbol == Any_## || fn.symbol == Object_##) {
// This is unattractive, but without it we crash here on ().## because after
// erasure the ScalaRunTime.hash overload goes from Unit => Int to BoxedUnit => Int.
// This must be because some earlier transformation is being skipped on ##, but so
// far I don't know what. For null we now define null.## == 0.
val arg = qual.tpe.typeSymbolDirect match {
case UnitClass => BLOCK(qual, REF(BoxedUnit_UNIT)) // ({ expr; UNIT }).##
case NullClass => LIT(0) // (null: Object).##
case _ => qual
}
Apply(gen.mkAttributedRef(scalaRuntimeHash), List(arg))
}
// Rewrite 5.getClass to ScalaRunTime.anyValClass(5)
else if (isValueClass(qual.tpe.typeSymbol))
Apply(gen.mkAttributedRef(scalaRuntimeAnyValClass), List(qual))
else
tree
case Apply(fn, args) =>
if (fn.symbol == Any_asInstanceOf)
(fn: @unchecked) match {
case TypeApply(Select(qual, _), List(targ)) =>
if (qual.tpe <:< targ.tpe) {
atPos(tree.pos) { Typed(qual, TypeTree(targ.tpe)) }
} else if (isNumericValueClass(qual.tpe.typeSymbol) &&
isNumericValueClass(targ.tpe.typeSymbol)) {
// convert numeric type casts
val cname = newTermName("to" + targ.tpe.typeSymbol.name)
val csym = qual.tpe.member(cname)
assert(csym != NoSymbol)
atPos(tree.pos) { Apply(Select(qual, csym), List()) }
} else
tree
}
// todo: also handle the case where the singleton type is buried in a compound
else if (fn.symbol == Any_isInstanceOf) {
fn match {
case TypeApply(sel @ Select(qual, name), List(targ)) =>
if (qual.tpe != null && isValueClass(qual.tpe.typeSymbol) && targ.tpe != null && targ.tpe <:< AnyRefClass.tpe)
unit.error(sel.pos, "isInstanceOf cannot test if value types are references.")
def mkIsInstanceOf(q: () => Tree)(tp: Type): Tree =
Apply(
TypeApply(
Select(q(), Object_isInstanceOf) setPos sel.pos,
List(TypeTree(tp) setPos targ.pos)) setPos fn.pos,
List()) setPos tree.pos
targ.tpe match {
case SingleType(_, _) | ThisType(_) | SuperType(_, _) =>
val cmpOp = if (targ.tpe <:< AnyValClass.tpe) Any_equals else Object_eq
atPos(tree.pos) {
Apply(Select(qual, cmpOp), List(gen.mkAttributedQualifier(targ.tpe)))
}
case RefinedType(parents, decls) if (parents.length >= 2) =>
// Optimization: don't generate isInstanceOf tests if the static type
// conforms, because it always succeeds. (Or at least it had better.)
// At this writing the pattern matcher generates some instance tests
// involving intersections where at least one parent is statically known true.
// That needs fixing, but filtering the parents here adds an additional
// level of robustness (in addition to the short term fix.)
val parentTests = parents filterNot (qual.tpe <:< _)
if (parentTests.isEmpty) Literal(Constant(true))
else gen.evalOnce(qual, currentOwner, unit) { q =>
atPos(tree.pos) {
parentTests map mkIsInstanceOf(q) reduceRight gen.mkAnd
}
}
case _ =>
tree
}
case _ => tree
}
}
else {
def doDynamic(fn: Tree, qual: Tree): Tree = {
if (fn.symbol.owner.isRefinementClass && fn.symbol.allOverriddenSymbols.isEmpty)
ApplyDynamic(qual, args) setSymbol fn.symbol setPos tree.pos
else tree
}
fn match {
case Select(qual, _) => doDynamic(fn, qual)
case TypeApply(fni@Select(qual, _), _) => doDynamic(fni, qual)// type parameters are irrelevant in case of dynamic call
case _ =>
tree
}
}
case Select(qual, name) =>
val owner = tree.symbol.owner
// println("preXform: "+ (tree, tree.symbol, tree.symbol.owner, tree.symbol.owner.isRefinementClass))
if (owner.isRefinementClass) {
val overridden = tree.symbol.allOverriddenSymbols
assert(!overridden.isEmpty, tree.symbol)
tree.symbol = overridden.head
}
def isAccessible(sym: Symbol) = localTyper.context.isAccessible(sym, sym.owner.thisType)
if (!isAccessible(owner) && qual.tpe != null) {
// Todo: Figure out how qual.tpe could be null in the check above (it does appear in build where SwingWorker.this
// has a null type).
val qualSym = qual.tpe.widen.typeSymbol
if (isAccessible(qualSym) && !qualSym.isPackageClass && !qualSym.isPackageObjectClass) {
// insert cast to prevent illegal access error (see #4283)
// util.trace("insert erasure cast ") (*/
treeCopy.Select(tree, qual AS_ATTR qual.tpe.widen, name) //)
} else tree
} else tree
case Template(parents, self, body) =>
assert(!currentOwner.isImplClass)
//Console.println("checking no dble defs " + tree)//DEBUG
checkNoDoubleDefs(tree.symbol.owner)
treeCopy.Template(tree, parents, emptyValDef, addBridges(body, currentOwner))
case Match(selector, cases) =>
Match(Typed(selector, TypeTree(selector.tpe)), cases)
case Literal(ct) if ct.tag == ClassTag
&& ct.typeValue.typeSymbol != definitions.UnitClass =>
treeCopy.Literal(tree, Constant(erasure(ct.typeValue)))
case _ =>
tree
}
override def transform(tree: Tree): Tree = {
// Reply to "!!! needed?" which adorned the next line: without it, build fails with:
// Exception in thread "main" scala.tools.nsc.symtab.Types$TypeError:
// value array_this is not a member of object scala.runtime.ScalaRunTime
//
// What the heck is array_this? See preTransformer in this file:
// gen.mkRuntimeCall("array_"+name, qual :: args)
if (tree.symbol == ArrayClass && !tree.isType) tree
else {
val tree1 = preErase(tree)
tree1 match {
case EmptyTree | TypeTree() =>
tree1 setType erasure(tree1.tpe)
case DefDef(_, _, _, _, tpt, _) =>
val result = super.transform(tree1) setType null
tpt.tpe = erasure(tree1.symbol.tpe).resultType
result
case _ =>
super.transform(tree1) setType null
}
}
}
}
/** The main transform function: Pretransfom the tree, and then
* re-type it at phase erasure.next.
*/
override def transform(tree: Tree): Tree = {
val tree1 = preTransformer.transform(tree)
atPhase(phase.next) {
val tree2 = mixinTransformer.transform(tree1)
if (settings.debug.value)
log("tree after addinterfaces: \n" + tree2)
newTyper(rootContext(unit, tree, true)).typed(tree2)
}
}
}
}
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