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Fix #4785: Change typing rule for wildcard star args #5577

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Merged
merged 2 commits into from
Dec 9, 2018
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Fix #4785: Change typing rule for wildcard star args #5577

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106749e
Fix #4785: Change typing rule for wildcard star args
allanrenucci Dec 7, 2018
47d969f
Revert 3c4b6bd
allanrenucci Dec 7, 2018
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/core/TypeApplications.scala
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Expand Up @@ -497,7 +497,7 @@ class TypeApplications(val self: Type) extends AnyVal {
}

/** The element type of a sequence or array */
def elemType(implicit ctx: Context): Type = self match {
def elemType(implicit ctx: Context): Type = self.widenDealias match {
case defn.ArrayOf(elemtp) => elemtp
case JavaArrayType(elemtp) => elemtp
case _ => self.baseType(defn.SeqClass).argInfos.headOption.getOrElse(NoType)
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39 changes: 19 additions & 20 deletions compiler/src/dotty/tools/dotc/transform/ElimRepeated.scala
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Expand Up @@ -71,40 +71,39 @@ class ElimRepeated extends MiniPhase with InfoTransformer { thisPhase =>
transformTypeOfTree(tree)

override def transformApply(tree: Apply)(implicit ctx: Context): Tree = {
val formals =
ctx.atPhase(thisPhase) { implicit ctx =>
tree.fun.tpe.widen.asInstanceOf[MethodType].paramInfos
}
val args1 = tree.args.zipWithConserve(formals) { (arg, formal) =>
arg match {
case arg: Typed if isWildcardStarArg(arg) =>
if (tree.fun.symbol.is(JavaDefined) && arg.expr.tpe.derivesFrom(defn.SeqClass))
seqToArray(arg.expr, formal.underlyingIfRepeated(isJava = true))
else arg.expr
case arg => arg
}
val args = tree.args.mapConserve {
case arg: Typed if isWildcardStarArg(arg) =>
val isJavaDefined = tree.fun.symbol.is(JavaDefined)
val tpe = arg.expr.tpe
if (isJavaDefined && tpe.derivesFrom(defn.SeqClass))
seqToArray(arg.expr)
else if (!isJavaDefined && tpe.derivesFrom(defn.ArrayClass))
arrayToSeq(arg.expr)
else
arg.expr
case arg => arg
}
transformTypeOfTree(cpy.Apply(tree)(tree.fun, args1))
transformTypeOfTree(cpy.Apply(tree)(tree.fun, args))
}

/** Convert sequence argument to Java array of type `pt` */
private def seqToArray(tree: Tree, pt: Type)(implicit ctx: Context): Tree = tree match {
/** Convert sequence argument to Java array */
private def seqToArray(tree: Tree)(implicit ctx: Context): Tree = tree match {
case SeqLiteral(elems, elemtpt) =>
JavaSeqLiteral(elems, elemtpt)
case app@Apply(fun, args) if defn.WrapArrayMethods().contains(fun.symbol) => // rewrite a call to `wrapXArray(arr)` to `arr`
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Why was this optimization dropped?

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@allanrenucci allanrenucci Dec 9, 2018 •
edited
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It is no longer needed. When calling into java repeated we used to insert an implicit conversion from Array to Seq that we later reverted. For example:

def test(xs: Array[String]) = Paths.get("Hello", xs: _*)

Before this patch:

// after frontend:
def test(xs: Array[String]) = Paths.get("Hello", wrapRefArray[String](xs):String*)

// after elimRepeated
def test(xs: Array[String]): = Paths.get("Hello", xs)

After this patch:

// after frontend:
def test(xs: Array[String]) = Paths.get("Hello", xs:String*) // no more call to wrapRefArray

// after elimRepeated
def test(xs: Array[String]): = Paths.get("Hello", xs)

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Thanks for explaining!

args.head
case _ =>
val elemType = tree.tpe.elemType
var elemClass = elemType.classSymbol
if (defn.NotRuntimeClasses contains elemClass) elemClass = defn.ObjectClass
if (defn.NotRuntimeClasses.contains(elemClass)) elemClass = defn.ObjectClass
ref(defn.DottyArraysModule)
.select(nme.seqToArray)
.appliedToType(elemType)
.appliedTo(tree, Literal(Constant(elemClass.typeRef)))
.ensureConforms(pt)
// Because of phantomclasses, the Java array's type might not conform to the return type
}

/** Convert Java array argument to Scala Seq */
private def arrayToSeq(tree: Tree)(implicit ctx: Context): Tree =
tpd.wrapArray(tree, tree.tpe.elemType)

override def transformTypeApply(tree: TypeApply)(implicit ctx: Context): Tree =
transformTypeOfTree(tree)

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8 changes: 6 additions & 2 deletions compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala
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Expand Up @@ -153,8 +153,12 @@ trait TypeAssigner {
if (!sym.is(SyntheticOrPrivate) && sym.owner.isClass) checkNoPrivateLeaks(sym, pos)
else sym.info

def seqToRepeated(tree: Tree)(implicit ctx: Context): Tree =
Typed(tree, TypeTree(tree.tpe.widen.translateParameterized(defn.SeqClass, defn.RepeatedParamClass)))
private def toRepeated(tree: Tree, from: ClassSymbol)(implicit ctx: Context): Tree =
Typed(tree, TypeTree(tree.tpe.widen.translateParameterized(from, defn.RepeatedParamClass)))

def seqToRepeated(tree: Tree)(implicit ctx: Context): Tree = toRepeated(tree, defn.SeqClass)

def arrayToRepeated(tree: Tree)(implicit ctx: Context): Tree = toRepeated(tree, defn.ArrayClass)

/** A denotation exists really if it exists and does not point to a stale symbol. */
final def reallyExists(denot: Denotation)(implicit ctx: Context): Boolean = try
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20 changes: 18 additions & 2 deletions compiler/src/dotty/tools/dotc/typer/Typer.scala
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Expand Up @@ -546,6 +546,7 @@ class Typer extends Namer
}
case _ => ifExpr
}

def ascription(tpt: Tree, isWildcard: Boolean) = {
val underlyingTreeTpe =
if (isRepeatedParamType(tpt)) TypeTree(defn.SeqType.appliedTo(pt :: Nil))
Expand All @@ -557,11 +558,26 @@ class Typer extends Namer
else typed(tree.expr, tpt.tpe.widenSkolem)
assignType(cpy.Typed(tree)(expr1, tpt), underlyingTreeTpe)
}
if (untpd.isWildcardStarArg(tree))

if (untpd.isWildcardStarArg(tree)) {
def typedWildcardStarArgExpr = {
val tpdExpr = typedExpr(tree.expr)
tpdExpr.tpe.widenDealias match {
case defn.ArrayOf(_) =>
val starType = defn.ArrayType.appliedTo(WildcardType)
val exprAdapted = adapt(tpdExpr, starType)
arrayToRepeated(exprAdapted)
case _ =>
val starType = defn.SeqType.appliedTo(defn.AnyType)
val exprAdapted = adapt(tpdExpr, starType)
seqToRepeated(exprAdapted)
}
}
cases(
ifPat = ascription(TypeTree(defn.RepeatedParamType.appliedTo(pt)), isWildcard = true),
ifExpr = seqToRepeated(typedExpr(tree.expr, defn.SeqType.appliedTo(defn.AnyType))),
ifExpr = typedWildcardStarArgExpr,
wildName = nme.WILDCARD_STAR)
}
else {
def typedTpt = checkSimpleKinded(typedType(tree.tpt))
def handlePattern: Tree = {
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4 changes: 2 additions & 2 deletions tests/neg/repeatedArgs213.scala
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Expand Up @@ -33,11 +33,11 @@ class repeatedArgs {
bar("a", "b", "c")
bar(xs: _*)
bar(ys: _*) // error: immutable.Seq expected, found Seq
bar(zs: _*) // error: immutable.Seq expected, found Array
bar(zs: _*) // old-error: Remove (compiler generated) Array to Seq convertion in 2.13?

Paths.get("Hello", "World")
Paths.get("Hello", xs: _*)
Paths.get("Hello", ys: _*) // error: immutable.Seq expected, found Seq
Paths.get("Hello", zs: _*) // error: immutable.Seq expected, found Array
Paths.get("Hello", zs: _*)
}
}
15 changes: 15 additions & 0 deletions tests/pos/i4785.scala
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@@ -0,0 +1,15 @@
import scala.Predef.Set // unimport Predef.wrapRefArray

import java.nio.file.Paths

class i4785 {
def bar(xs: String*) = xs.length

def test(xs: Seq[String], ys: Array[String]) = {
Paths.get("Hello", xs: _*)
Paths.get("Hello", ys: _*)

bar(xs: _*)
bar(ys: _*)
}
}
4 changes: 4 additions & 0 deletions tests/pos/repeatedArgs.scala
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@@ -1,5 +1,6 @@
import scala.collection.{immutable, mutable}
import java.nio.file.Paths
import java.util.concurrent.ForkJoinTask

class repeatedArgs {
def bar(xs: String*): Int = xs.length
Expand All @@ -19,4 +20,7 @@ class repeatedArgs {
val x: collection.Seq[String] = others
// val y: immutable.Seq[String] = others // ok in 2.13
}

def invokeAll[T](tasks: ForkJoinTask[T]*): Unit = ForkJoinTask.invokeAll(tasks: _*)
def invokeAll2(tasks: ForkJoinTask[_]*): Unit = ForkJoinTask.invokeAll(tasks: _*)
}