diff options
Diffstat (limited to 'src/reflect')
| -rw-r--r-- | src/reflect/scala/reflect/internal/tpe/TypeMaps.scala | 81 |
1 files changed, 51 insertions, 30 deletions
diff --git a/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala b/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala index f427813c01..07c9242bf3 100644 --- a/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala +++ b/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala @@ -863,31 +863,24 @@ private[internal] trait TypeMaps { private val existentials = new Array[Symbol](actuals.size) def existentialsNeeded: List[Symbol] = existentials.iterator.filter(_ ne null).toList - private object StableArg { - def unapply(param: Symbol) = Arg unapply param map actuals filter (tp => - tp.isStable && (tp.typeSymbol != NothingClass) - ) - } - private object Arg { - def unapply(param: Symbol) = Some(params indexOf param) filter (_ >= 0) - } - - def apply(tp: Type): Type = mapOver(tp) match { - // unsound to replace args by unstable actual #3873 - case SingleType(NoPrefix, StableArg(arg)) => arg - // (soundly) expand type alias selections on implicit arguments, - // see depmet_implicit_oopsla* test cases -- typically, `param.isImplicit` - case tp1 @ TypeRef(SingleType(NoPrefix, Arg(pid)), sym, targs) => - val arg = actuals(pid) - val res = typeRef(arg, sym, targs) - if (res.typeSymbolDirect.isAliasType) res.dealias else tp1 - // don't return the original `tp`, which may be different from `tp1`, - // due to dropping annotations - case tp1 => tp1 + private object StableArgTp { + // type of actual arg corresponding to param -- if the type is stable + def unapply(param: Symbol): Option[Type] = (params indexOf param) match { + case -1 => None + case pid => + val tp = actuals(pid) + if (tp.isStable && (tp.typeSymbol != NothingClass)) Some(tp) + else None + } } - /* Return the type symbol for referencing a parameter inside the existential quantifier. - * (Only needed if the actual is unstable.) + /** Return the type symbol for referencing a parameter that's instantiated to an unstable actual argument. + * + * To soundly abstract over an unstable value (x: T) while retaining the most type information, + * use `x.type forSome { type x.type <: T with Singleton}` + * `typeOf[T].narrowExistentially(symbolOf[x])`. + * + * See also: captureThis in AsSeenFromMap. */ private def existentialFor(pid: Int) = { if (existentials(pid) eq null) { @@ -900,6 +893,38 @@ private[internal] trait TypeMaps { existentials(pid) } + private object UnstableArgTp { + // existential quantifier and type of corresponding actual arg with unstable type + def unapply(param: Symbol): Option[(Symbol, Type)] = (params indexOf param) match { + case -1 => None + case pid => + val sym = existentialFor(pid) + Some((sym, sym.tpe_*)) // refers to an actual value, must be kind-* + } + } + + private object StabilizedArgTp { + def unapply(param: Symbol): Option[Type] = + param match { + case StableArgTp(tp) => Some(tp) // (1) + case UnstableArgTp(_, tp) => Some(tp) // (2) + case _ => None + } + } + + /** instantiate `param.type` to the (sound approximation of the) type `T` + * of the actual argument `arg` that was passed in for `param` + * + * (1) If `T` is stable, we can just use that. + * + * (2) SI-3873: it'd be unsound to instantiate `param.type` to an unstable `T`, + * so we approximate to `X forSome {type X <: T with Singleton}` -- we can't soundly say more. + */ + def apply(tp: Type): Type = tp match { + case SingleType(NoPrefix, StabilizedArgTp(tp)) => tp + case _ => mapOver(tp) + } + //AM propagate more info to annotations -- this seems a bit ad-hoc... (based on code by spoon) override def mapOver(arg: Tree, giveup: ()=>Nothing): Tree = { // TODO: this should be simplified; in the stable case, one can @@ -922,13 +947,9 @@ private[internal] trait TypeMaps { // Both examples are from run/constrained-types.scala. object treeTrans extends Transformer { override def transform(tree: Tree): Tree = tree.symbol match { - case StableArg(actual) => - gen.mkAttributedQualifier(actual, tree.symbol) - case Arg(pid) => - val sym = existentialFor(pid) - Ident(sym) copyAttrs tree setType typeRef(NoPrefix, sym, Nil) - case _ => - super.transform(tree) + case StableArgTp(tp) => gen.mkAttributedQualifier(tp, tree.symbol) + case UnstableArgTp(quant, tp) => Ident(quant) copyAttrs tree setType tp + case _ => super.transform(tree) } } treeTrans transform arg |