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package dotty.tools.dotc.core
import Contexts._, Types._, Symbols._, Names._, Flags._, Scopes._
trait TypeOps { this: Context =>
def newSkolemSingleton(underlying: Type) = TermRef.withSym(NoPrefix, newSkolem(underlying))
final def asSeenFrom(tp: Type, pre: Type, cls: Symbol, theMap: AsSeenFromMap): Type = {
def toPrefix(pre: Type, cls: Symbol, thiscls: ClassSymbol): Type = ctx.debugTraceIndented(s"toPrefix($pre, $cls, $thiscls)") {
if ((pre eq NoType) || (pre eq NoPrefix) || (cls is PackageClass))
tp
else if (thiscls.derivesFrom(cls) && pre.baseType(thiscls).exists)
pre match {
case SuperType(thispre, _) => thispre
case _ => pre
}
else
toPrefix(pre.baseType(cls).normalizedPrefix, cls.owner, thiscls)
}
ctx.debugTraceIndented(s"$tp.asSeenFrom($pre, $cls)") { // !!! DEBUG
tp match {
case tp: NamedType =>
val sym = tp.symbol
if (sym.isStatic) tp
else {
val tp1 = tp.derivedNamedType(asSeenFrom(tp.prefix, pre, cls, theMap))
// Here's an explanation why we short-circuit instantiated type parameters.
// Say you have This is translated to:
//
// class List[type T] ==> class List { type T; val hd: T }
// xs: List[Int] ==> List { type T = Int }
//
// Then with the line above, xs.hd would have type xs.T
//
// But in Scala 2.x, its type is Int, which is the dealiased version
// of xs.T. With the logic below, we get the same outcome as for 2.x.
if ((tp1 ne tp) && (sym is (TypeParam, butNot = Deferred))) tp1.dealias // todo: why not TypeArgument?
else tp1
}
case ThisType(thiscls) =>
toPrefix(pre, cls, thiscls)
case _: BoundType | NoPrefix =>
tp
case tp: RefinedType =>
tp.derivedRefinedType(
asSeenFrom(tp.parent, pre, cls, theMap),
tp.refinedName,
asSeenFrom(tp.refinedInfo, pre, cls, theMap))
// case tp: ClassInfo => !!! disabled for now
// tp.derivedClassInfo(asSeenFrom(tp.prefix, pre, cls, theMap))
case _ =>
(if (theMap != null) theMap else new AsSeenFromMap(pre, cls))
.mapOver(tp)
}
}
}
class AsSeenFromMap(pre: Type, cls: Symbol) extends TypeMap {
def apply(tp: Type) = asSeenFrom(tp, pre, cls, this)
}
final def isVolatile(tp: Type): Boolean = {
/** Pre-filter to avoid expensive DNF computation */
def needsChecking(tp: Type, isPart: Boolean): Boolean = tp match {
case tp: TypeRef =>
tp.info match {
case TypeBounds(lo, hi) =>
if (lo eq hi) needsChecking(hi, isPart)
else isPart || tp.controlled(isVolatile(hi))
case _ => false
}
case tp: RefinedType =>
needsChecking(tp.parent, true)
case tp: TypeProxy =>
needsChecking(tp.underlying, isPart)
case AndType(l, r) =>
needsChecking(l, true) || needsChecking(r, true)
case OrType(l, r) =>
isPart || needsChecking(l, isPart) && needsChecking(r, isPart)
case _ =>
false
}
needsChecking(tp, false) && {
tp.DNF forall { case (parents, refinedNames) =>
val absParents = parents filter (_.symbol is Deferred)
absParents.size >= 2 || {
val ap = absParents.head
(parents exists (p =>
(p ne ap) || p.abstractMemberNames(tp).nonEmpty)) ||
(refinedNames & tp.abstractMemberNames()).nonEmpty ||
isVolatile(ap)
}
}
}
}
/** Normalize a list of parent types of class `cls` that may contain refinements
* to a list of typerefs, by converting all refinements to member
* definitions in scope `decls`. Can add members to `decls` as a side-effect.
*/
def normalizeToRefs(parents: List[Type], cls: ClassSymbol, decls: Scope): List[TypeRef] = {
def enterArgBinding(formal: Symbol, info: Type) = {
val typeArgFlag = if (formal is Local) TypeArgument else EmptyFlags
val sym = ctx.newSymbol(cls, formal.name, formal.flags & RetainedTypeArgFlags | typeArgFlag, info)
cls.enter(sym, decls)
}
/** If we just entered the type argument binding
*
* type From = To
*
* and there is a type argument binding in a parent in `prefs` of the form
*
* type X = From
*
* then also add the binding
*
* type X = To
*
* to the current scope, provided (1) variances of both aliases are the same, and
* (2) X is not yet defined in current scope. This "short-circuiting" prevents
* long chains of aliases which would have to be traversed in type comparers.
*/
def forwardRefs(from: Symbol, to: Type, prefs: List[TypeRef]) = to match {
case to @ TypeBounds(lo1, hi1) if lo1 eq hi1 =>
for (pref <- prefs)
for (argSym <- pref.decls)
if (argSym is TypeArgument) {
argSym.info match {
case info @ TypeBounds(lo2 @ TypeRef(ThisType(_), name), hi2) =>
if (name == from.name &&
(lo2 eq hi2) &&
info.variance == to.variance &&
!decls.lookup(argSym.name).exists) {
// println(s"short-circuit ${argSym.name} was: ${argSym.info}, now: $to")
enterArgBinding(argSym, to)
}
case _ =>
}
}
case _ =>
}
// println(s"normalizing $parents of $cls in ${cls.owner}") // !!! DEBUG
var refinements = Map[TypeName, Type]()
var formals = Map[TypeName, Symbol]()
def normalizeToRef(tp: Type): TypeRef = tp match {
case tp @ RefinedType(tp1, name: TypeName) =>
refinements = refinements.updated(name,
refinements get name match {
case Some(info) => info & tp.refinedInfo
case none => tp.refinedInfo
})
formals = formals.updated(name, tp1.typeParamNamed(name))
normalizeToRef(tp1)
case tp: TypeRef =>
tp
case ErrorType =>
defn.AnyClass.typeConstructor
case _ =>
throw new TypeError(s"unexpected parent type: $tp")
}
val parentRefs = parents map normalizeToRef
for ((name, tpe) <- refinements) {
assert(decls.lookup(name) == NoSymbol, // DEBUG
s"redefinition of ${decls.lookup(name).debugString} in ${cls.showLocated}")
enterArgBinding(formals(name), tpe)
}
// These two loops cannot be fused because second loop assumes that
// all arguments have been entered in `decls`.
for ((name, tpe) <- refinements) {
forwardRefs(formals(name), tpe, parentRefs)
}
parentRefs
}
}
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