package dotty.tools.dotc
package transform
import dotty.tools.dotc.transform.TreeTransforms.{TransformerInfo, TreeTransform, TreeTransformer}
import dotty.tools.dotc.ast.{Trees, tpd}
import scala.collection.{ mutable, immutable }
import ValueClasses._
import scala.annotation.tailrec
import core._
import Types._, Contexts._, Constants._, Names._, NameOps._, Flags._, DenotTransformers._
import SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._, Scopes._, Denotations._
import util.Positions._
import Decorators._
import Symbols._, TypeUtils._
/** This class performs the following functions:
*
* (1) Adds super accessors for all super calls that either
* appear in a trait or have as a target a member of some outer class.
*
* (2) Adds protected accessors if the access to the protected member happens
* in a class which is not a subclass of the member's owner.
*
* It also checks that:
*
* (1) Symbols accessed from super are not abstract, or are overridden by
* an abstract override.
*
* (2) If a symbol accessed from super is defined in a real class (not a trait),
* there are no abstract members which override this member in Java's rules
* (see SI-4989; such an access would lead to illegal bytecode)
*
* (3) Super calls do not go to some synthetic members of Any (see isDisallowed)
*
* (4) Super calls do not go to synthetic field accessors
*/
class SuperAccessors(thisTransformer: DenotTransformer) {
import tpd._
/** Some parts of trees will get a new owner in subsequent phases.
* These are value class methods, which will become extension methods.
* (By-name arguments used to be included also, but these
* don't get a new class anymore, they are just wrapped in a new method).
*
* These regions will have to be treated specially for the purpose
* of adding accessors. For instance, super calls from these regions
* always have to go through an accessor.
*
* The `invalidEnclClass` field, if different from NoSymbol,
* contains the symbol that is not a valid owner.
*/
private var invalidEnclClass: Symbol = NoSymbol
private def withInvalidCurrentClass[A](trans: => A)(implicit ctx: Context): A = {
val saved = invalidEnclClass
invalidEnclClass = ctx.owner
try trans
finally invalidEnclClass = saved
}
private def validCurrentClass(implicit ctx: Context): Boolean =
ctx.owner.enclosingClass != invalidEnclClass
/** List buffers for new accessor definitions, indexed by class */
private val accDefs = mutable.Map[Symbol, mutable.ListBuffer[Tree]]()
/** A super accessor call corresponding to `sel` */
private def superAccessorCall(sel: Select)(implicit ctx: Context) = {
val Select(qual, name) = sel
val sym = sel.symbol
val clazz = qual.symbol.asClass
var superName = name.superName
if (clazz is Trait) superName = superName.expandedName(clazz)
val superInfo = sel.tpe.widenSingleton.ensureMethodic
val superAcc = clazz.info.decl(superName)
.suchThat(_.signature == superInfo.signature).symbol
.orElse {
ctx.debuglog(s"add super acc ${sym.showLocated} to $clazz")
val deferredOrPrivate = if (clazz is Trait) Deferred | ExpandedName else Private
val acc = ctx.newSymbol(
clazz, superName, SuperAccessor | Artifact | Method | deferredOrPrivate,
superInfo, coord = sym.coord).enteredAfter(thisTransformer)
// Diagnostic for SI-7091
if (!accDefs.contains(clazz))
ctx.error(s"Internal error: unable to store accessor definition in ${clazz}. clazz.hasPackageFlag=${clazz is Package}. Accessor required for ${sel} (${sel.show})", sel.pos)
else accDefs(clazz) += DefDef(acc, EmptyTree)
acc
}
This(clazz).select(superAcc).withPos(sel.pos)
}
/** Check selection `super.f` for conforming to rules. If necessary,
* replace by a super accessor call.
*/
private def transformSuperSelect(sel: Select)(implicit ctx: Context): Tree = {
val Select(sup @ Super(_, mix), name) = sel
val sym = sel.symbol
assert(sup.symbol.exists, s"missing symbol in $sel: ${sup.tpe}")
val clazz = sup.symbol.asClass
if (sym.isTerm && !sym.is(Method, butNot = Accessor) && !ctx.owner.is(ParamForwarder))
// ParamForwaders as installed ParamForwarding.scala do use super calls to vals
ctx.error(s"super may be not be used on ${sym.underlyingSymbol}", sel.pos)
else if (isDisallowed(sym))
ctx.error(s"super not allowed here: use this.${sel.name.decode} instead", sel.pos)
else if (sym is Deferred) {
val member = sym.overridingSymbol(clazz)
if (!mix.name.isEmpty ||
!member.exists ||
!((member is AbsOverride) && member.isIncompleteIn(clazz)))
ctx.error(
i"${sym.showLocated} is accessed from super. It may not be abstract unless it is overridden by a member declared `abstract' and `override'",
sel.pos)
else ctx.log(i"ok super $sel ${sym.showLocated} $member $clazz ${member.isIncompleteIn(clazz)}")
}
else if (mix.name.isEmpty && !(sym.owner is Trait))
// SI-4989 Check if an intermediate class between `clazz` and `sym.owner` redeclares the method as abstract.
for (intermediateClass <- clazz.info.baseClasses.tail.takeWhile(_ != sym.owner)) {
val overriding = sym.overridingSymbol(intermediateClass)
if ((overriding is (Deferred, butNot = AbsOverride)) && !(overriding.owner is Trait))
ctx.error(
s"${sym.showLocated} cannot be directly accessed from ${clazz} because ${overriding.owner} redeclares it as abstract",
sel.pos)
}
if (name.isTermName && mix.name.isEmpty &&
((clazz is Trait) || clazz != ctx.owner.enclosingClass || !validCurrentClass))
superAccessorCall(sel)(ctx.withPhase(thisTransformer.next))
else sel
}
/** Disallow some super.XX calls targeting Any methods which would
* otherwise lead to either a compiler crash or runtime failure.
*/
private def isDisallowed(sym: Symbol)(implicit ctx: Context) = {
val d = defn
import d._
(sym eq Any_isInstanceOf) ||
(sym eq Any_asInstanceOf) ||
(sym eq Any_==) ||
(sym eq Any_!=) ||
(sym eq Any_##)
}
/** Replace `sel` (or `sel[targs]` if `targs` is nonempty) with a protected accessor
* call, if necessary.
*/
private def ensureProtectedAccessOK(sel: Select, targs: List[Tree])(implicit ctx: Context) = {
val sym = sel.symbol
if (sym.isTerm && !sel.name.isOuterSelect && needsProtectedAccessor(sym, sel.pos)) {
ctx.debuglog("Adding protected accessor for " + sel)
protectedAccessorCall(sel, targs)
} else sel
}
/** Add a protected accessor, if needed, and return a tree that calls
* the accessor and returns the same member. The result is already
* typed.
*/
private def protectedAccessorCall(sel: Select, targs: List[Tree])(implicit ctx: Context): Tree = {
val Select(qual, _) = sel
val sym = sel.symbol.asTerm
val clazz = hostForAccessorOf(sym, currentClass)
assert(clazz.exists, sym)
ctx.debuglog("Decided for host class: " + clazz)
val accName = sym.name.protectedAccessorName
// if the result type depends on the this type of an enclosing class, the accessor
// has to take an object of exactly this type, otherwise it's more general
val receiverType =
if (isThisType(sym.info.finalResultType)) clazz.thisType
else clazz.classInfo.selfType
val accType = {
def accTypeOf(tpe: Type): Type = tpe match {
case tpe: PolyType =>
tpe.derivedLambdaType(tpe.paramNames, tpe.paramInfos, accTypeOf(tpe.resultType))
case _ =>
MethodType(receiverType :: Nil)(mt => tpe.substThis(sym.owner.asClass, mt.newParamRef(0)))
}
accTypeOf(sym.info)
}
val protectedAccessor = clazz.info.decl(accName).suchThat(_.signature == accType.signature).symbol orElse {
val newAcc = ctx.newSymbol(
clazz, accName, Artifact, accType, coord = sel.pos).enteredAfter(thisTransformer)
val code = polyDefDef(newAcc, trefs => vrefss => {
val (receiver :: _) :: tail = vrefss
val base = receiver.select(sym).appliedToTypes(trefs)
(base /: vrefss)(Apply(_, _))
})
ctx.debuglog("created protected accessor: " + code)
accDefs(clazz) += code
newAcc
}
val res = This(clazz)
.select(protectedAccessor)
.appliedToTypeTrees(targs)
.appliedTo(qual)
.withPos(sel.pos)
ctx.debuglog(s"Replaced $sel with $res")
res
}
def isProtectedAccessor(tree: Tree)(implicit ctx: Context): Boolean = tree match {
case Apply(TypeApply(Select(_, name), _), qual :: Nil) => name.isProtectedAccessorName
case _ => false
}
/** Add a protected accessor, if needed, and return a tree that calls
* the accessor and returns the same member. The result is already
* typed.
*/
private def protectedAccessor(tree: Select, targs: List[Tree])(implicit ctx: Context): Tree = {
val Select(qual, _) = tree
val sym = tree.symbol.asTerm
val clazz = hostForAccessorOf(sym, currentClass)
assert(clazz.exists, sym)
ctx.debuglog("Decided for host class: " + clazz)
val accName = sym.name.protectedAccessorName
// if the result type depends on the this type of an enclosing class, the accessor
// has to take an object of exactly this type, otherwise it's more general
val receiverType =
if (isThisType(sym.info.finalResultType)) clazz.thisType
else clazz.classInfo.selfType
def accTypeOf(tpe: Type): Type = tpe match {
case tpe: PolyType =>
tpe.derivedLambdaType(tpe.paramNames, tpe.paramInfos, accTypeOf(tpe.resultType))
case _ =>
MethodType(receiverType :: Nil)(mt => tpe.substThis(sym.owner.asClass, mt.newParamRef(0)))
}
val accType = accTypeOf(sym.info)
val protectedAccessor = clazz.info.decl(accName).suchThat(_.signature == accType.signature).symbol orElse {
val newAcc = ctx.newSymbol(
clazz, accName, Artifact, accType, coord = tree.pos).enteredAfter(thisTransformer)
val code = polyDefDef(newAcc, trefs => vrefss => {
val (receiver :: _) :: tail = vrefss
val base = receiver.select(sym).appliedToTypes(trefs)
(base /: vrefss)(Apply(_, _))
})
ctx.debuglog("created protected accessor: " + code)
accDefs(clazz) += code
newAcc
}
val res = This(clazz)
.select(protectedAccessor)
.appliedToTypeTrees(targs)
.appliedTo(qual)
.withPos(tree.pos)
ctx.debuglog(s"Replaced $tree with $res")
res
}
/** Add an accessor for field, if needed, and return a selection tree for it .
* The result is not typed.
*/
private def protectedSetter(tree: Select)(implicit ctx: Context): Tree = {
val field = tree.symbol.asTerm
val clazz = hostForAccessorOf(field, currentClass)
assert(clazz.exists, field)
ctx.debuglog("Decided for host class: " + clazz)
val accName = field.name.protectedSetterName
val accType = MethodType(clazz.classInfo.selfType :: field.info :: Nil, defn.UnitType)
val protectedAccessor = clazz.info.decl(accName).symbol orElse {
val newAcc = ctx.newSymbol(
clazz, accName, Artifact, accType, coord = tree.pos).enteredAfter(thisTransformer)
val code = DefDef(newAcc, vrefss => {
val (receiver :: value :: Nil) :: Nil = vrefss
Assign(receiver.select(field), value).withPos(tree.pos)
})
ctx.debuglog("created protected setter: " + code)
accDefs(clazz) += code
newAcc
}
This(clazz).select(protectedAccessor).withPos(tree.pos)
}
/** Does `sym` need an accessor when accessed from `currentClass`?
* A special case arises for classes with explicit self-types. If the
* self type is a Java class, and a protected accessor is needed, we issue
* an error. If the self type is a Scala class, we don't add an accessor.
* An accessor is not needed if the access boundary is larger than the
* enclosing package, since that translates to 'public' on the host sys.
* (as Java has no real package nesting).
*
* If the access happens inside a 'trait', access is more problematic since
* the implementation code is moved to an '$class' class which does not
* inherit anything. Since we can't (yet) add accessors for 'required'
* classes, this has to be signaled as error.
* FIXME Need to better understand this logic
*/
private def needsProtectedAccessor(sym: Symbol, pos: Position)(implicit ctx: Context): Boolean = {
val clazz = currentClass
val host = hostForAccessorOf(sym, clazz)
val selfType = host.classInfo.selfType
def accessibleThroughSubclassing =
validCurrentClass && (selfType <:< sym.owner.typeRef) && !clazz.is(Trait)
val isCandidate = (
sym.is(Protected)
&& sym.is(JavaDefined)
&& !sym.effectiveOwner.is(Package)
&& !accessibleThroughSubclassing
&& (sym.enclosingPackageClass != currentClass.enclosingPackageClass)
&& (sym.enclosingPackageClass == sym.accessBoundary(sym.enclosingPackageClass))
)
def isSelfType = !(host.typeRef <:< selfType) && {
if (selfType.typeSymbol.is(JavaDefined))
ctx.restrictionError(s"cannot accesses protected $sym from within $clazz with self type $selfType", pos)
true
}
def isJavaProtected = host.is(Trait) && sym.is(JavaDefined) && {
ctx.restrictionError(
s"""$clazz accesses protected $sym inside a concrete trait method.
|Add an accessor in a class extending ${sym.enclosingClass} as a workaround.""".stripMargin,
pos
)
true
}
isCandidate && !host.is(Package) && !isSelfType && !isJavaProtected
}
/** Return the innermost enclosing class C of referencingClass for which either
* of the following holds:
* - C is a subclass of sym.owner or
* - C is declared in the same package as sym's owner
*/
private def hostForAccessorOf(sym: Symbol, referencingClass: ClassSymbol)(implicit ctx: Context): ClassSymbol =
if (referencingClass.derivesFrom(sym.owner)
|| referencingClass.classInfo.selfType <:< sym.owner.typeRef
|| referencingClass.enclosingPackageClass == sym.owner.enclosingPackageClass) {
assert(referencingClass.isClass, referencingClass)
referencingClass
}
else if (referencingClass.owner.enclosingClass.exists)
hostForAccessorOf(sym, referencingClass.owner.enclosingClass.asClass)
else
referencingClass
/** Is 'tpe' a ThisType, or a type proxy with a ThisType as transitively underlying type? */
private def isThisType(tpe: Type)(implicit ctx: Context): Boolean = tpe match {
case tpe: ThisType => !tpe.cls.is(PackageClass)
case tpe: TypeProxy => isThisType(tpe.underlying)
case _ => false
}
/** Transform select node, adding super and protected accessors as needed */
def transformSelect(tree: Tree, targs: List[Tree])(implicit ctx: Context) = {
val sel @ Select(qual, name) = tree
val sym = sel.symbol
qual match {
case _: This =>
/*
* A trait which extends a class and accesses a protected member
* of that class cannot implement the necessary accessor method
* because its implementation is in an implementation class (e.g.
* Foo$class) which inherits nothing, and jvm access restrictions
* require the call site to be in an actual subclass. So non-trait
* classes inspect their ancestors for any such situations and
* generate the accessors. See SI-2296.
*/
// FIXME (from scalac's SuperAccessors)
// - this should be unified with needsProtectedAccessor, but some
// subtlety which presently eludes me is foiling my attempts.
val shouldEnsureAccessor = (
(currentClass is Trait)
&& (sym is Protected)
&& sym.enclosingClass != currentClass
&& !(sym.owner is PackageClass) // SI-7091 no accessor needed package owned (ie, top level) symbols
&& !(sym.owner is Trait)
&& sym.owner.enclosingPackageClass != currentClass.enclosingPackageClass
&& qual.symbol.info.member(sym.name).exists
&& !needsProtectedAccessor(sym, sel.pos))
if (shouldEnsureAccessor) {
ctx.log("Ensuring accessor for call to protected " + sym.showLocated + " from " + currentClass)
superAccessorCall(sel)
} else
ensureProtectedAccessOK(sel, targs)
case Super(_, mix) =>
transformSuperSelect(sel)
case _ =>
ensureProtectedAccessOK(sel, targs)
}
}
/** Transform assignment, adding a protected setter if needed */
def transformAssign(tree: Tree)(implicit ctx: Context) = {
val Assign(lhs @ Select(qual, name), rhs) = tree
if ((lhs.symbol is Mutable) &&
(lhs.symbol is JavaDefined) &&
needsProtectedAccessor(lhs.symbol, tree.pos)) {
ctx.debuglog("Adding protected setter for " + tree)
val setter = protectedSetter(lhs)
ctx.debuglog("Replaced " + tree + " with " + setter)
setter.appliedTo(qual, rhs)
}
else tree
}
/** Wrap template to template transform `op` with needed initialization and finalization */
def wrapTemplate(tree: Template)(op: Template => Template)(implicit ctx: Context) = {
accDefs(currentClass) = new mutable.ListBuffer[Tree]
val impl = op(tree)
val accessors = accDefs.remove(currentClass).get
if (accessors.isEmpty) impl
else {
val (params, rest) = impl.body span {
case td: TypeDef => !td.isClassDef
case vd: ValOrDefDef => vd.symbol.flags is ParamAccessor
case _ => false
}
cpy.Template(impl)(body = params ++ accessors ++ rest)
}
}
/** Wrap `DefDef` producing operation `op`, potentially setting `invalidClass` info */
def wrapDefDef(ddef: DefDef)(op: => DefDef)(implicit ctx: Context) =
if (isMethodWithExtension(ddef.symbol)) withInvalidCurrentClass(op) else op
}