Disallow xs: _* vararg syntax and use xs* instead

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -2343,12 +2343,13 @@ object Parsers {
           val isVarargSplice = location.inArgs && followingIsVararg()
           in.nextToken()
           if isVarargSplice then
-            report.errorOrMigrationWarning(
-              em"The syntax `x: _*` is no longer supported for vararg splices; use `x*` instead${rewriteNotice(`future-migration`)}",
-              in.sourcePos(uscoreStart),
-              future)
-            if sourceVersion == `future-migration` then
-              patch(source, Span(t.span.end, in.lastOffset), "*")
+            if !in.featureEnabled(Feature.ascriptionVarargsUnpacking) then
+              report.errorOrMigrationWarning(
+                em"The syntax `x: _*` is no longer supported for vararg splices; use `x*` instead${rewriteNotice(`3.4-migration`)}",
+                in.sourcePos(uscoreStart),
+                `3.4`)
+              if sourceVersion == `3.4-migration` then
+                patch(source, Span(t.span.end, in.lastOffset), "*")
           else if opStack.nonEmpty then
             report.errorOrMigrationWarning(
               em"""`_*` can be used only for last argument of method application.

project/Build.scala

@@ -1008,7 +1008,10 @@ object Build {
         Seq("-sourcepath", ((Compile/sourceManaged).value / "scala-library-src").toString)
       },
       Compile / doc / scalacOptions += "-Ydocument-synthetic-types",
-      scalacOptions += "-Ycompile-scala2-library",
+      scalacOptions ++= Seq(
+        "-Ycompile-scala2-library",
+        "-language:deprecated.ascriptionVarargsUnpacking",
+      ),
       scalacOptions -= "-Xfatal-warnings",
       ivyConfigurations += SourceDeps.hide,
       transitiveClassifiers := Seq("sources"),
@@ -1361,6 +1364,7 @@ object Build {
     dependsOn(`scala3-library-bootstrappedJS`).
     settings(
       bspEnabled := false,
+      scalacOptions += "-language:deprecated.ascriptionVarargsUnpacking",
       scalacOptions --= Seq("-Xfatal-warnings", "-deprecation"),
 
       // Required to run Scala.js tests.

sbt-test/sbt-dotty/scaladoc/src/main/scala/PatternMatching.scala

@@ -70,8 +70,8 @@ object PatternMatching {
 
     // http://dotty.epfl.ch/docs/reference/changed/vararg-patterns.html
     def containsConsecutive(list: List[Int]): Boolean = list match {
-      case List(a, b, xs: _ *) => if (a == b) true else containsConsecutive(b :: xs.toList)
-      case List(a, _ : _*) => false
+      case List(a, b, xs*) => if (a == b) true else containsConsecutive(b :: xs.toList)
+      case List(a, _*) => false
       case Nil => false
     }
 
@@ -86,7 +86,7 @@ object PatternMatching {
     import seqPattern._
 
     def greet(fullName: String) = fullName match {
-      case Names(lastName, firstName, _: _*) => "Good morning, " + firstName + " " + lastName + "!"
+      case Names(lastName, firstName, _*) => "Good morning, " + firstName + " " + lastName + "!"
       case _ => "Welcome! Please make sure to fill in your name!"
     }
 

tests/explicit-nulls/neg/varargs.scala

@@ -17,34 +17,34 @@ class Varargs {
     f1(null) // error
     f1("")
     f1("", null) // error
-    f1(null: _*) // error
+    f1(null*) // error
 
-    f1(xs1: _*)
-    f1(xs2: _*) // error
-    f1(xs3: _*) // error
-    f1(xs4: _*) // error
+    f1(xs1*)
+    f1(xs2*) // error
+    f1(xs3*) // error
+    f1(xs4*) // error
 
-    f1(ys1: _*)
-    f1(ys2: _*) // error
-    f1(ys3: _*) // error
-    f1(ys4: _*) // error
+    f1(ys1*)
+    f1(ys2*) // error
+    f1(ys3*) // error
+    f1(ys4*) // error
   }
 
   def test2 = {
     f2()
     f2(null)
     f2("")
     f2("", null)
-    f2(null: _*) // error
+    f2(null*) // error
 
-    f2(xs1: _*)
-    f2(xs2: _*)
-    f2(xs3: _*) // error
-    f2(xs4: _*) // error
+    f2(xs1*)
+    f2(xs2*)
+    f2(xs3*) // error
+    f2(xs4*) // error
 
-    f2(ys1: _*)
-    f2(ys2: _*)
-    f2(ys3: _*) // error
-    f2(ys4: _*) // error
+    f2(ys1*)
+    f2(ys2*)
+    f2(ys3*) // error
+    f2(ys4*) // error
   }
 }

tests/explicit-nulls/unsafe-common/unsafe-java-varargs-src/S.scala

@@ -12,8 +12,8 @@ class S {
   val arg3: Array[String] | Null = ???
   val arg4: Array[String | Null] | Null = ???
 
-  j.foo(arg1: _*)
-  j.foo(arg2: _*)
-  j.foo(arg3: _*) // error
-  j.foo(arg4: _*) // error
+  j.foo(arg1*)
+  j.foo(arg2*)
+  j.foo(arg3*) // error
+  j.foo(arg4*) // error
 }

tests/explicit-nulls/unsafe-common/unsafe-java-varargs.scala

@@ -24,15 +24,15 @@ def test2 = {
   val ys3: Array[String | Null] | Null = ???
   val ys4: Array[String] | Null = ???
 
-  Paths.get("", xs1: _*)
-  Paths.get("", xs2: _*)
-  Paths.get("", xs3: _*) // error
-  Paths.get("", xs4: _*) // error
+  Paths.get("", xs1*)
+  Paths.get("", xs2*)
+  Paths.get("", xs3*) // error
+  Paths.get("", xs4*) // error
 
-  Paths.get("", ys1: _*)
-  Paths.get("", ys2: _*)
-  Paths.get("", ys3: _*) // error
-  Paths.get("", ys4: _*) // error
+  Paths.get("", ys1*)
+  Paths.get("", ys2*)
+  Paths.get("", ys3*) // error
+  Paths.get("", ys4*) // error
 
-  Paths.get("", null: _*) // error
+  Paths.get("", null*) // error
 }

tests/neg/i6622d.scala

@@ -3,7 +3,7 @@ import scala.compiletime.*
 object Test {
 
   def main(args: Array[String]): Unit = {
-    println(StringContext("abc").code(Seq.empty[Any]:_*)) // error
+    println(StringContext("abc").code(Seq.empty[Any]*)) // error
   }
 
 }

tests/neg/i6622e.scala

@@ -3,7 +3,7 @@ import scala.compiletime.*
 object Test {
 
   def main(args: Array[String]): Unit = {
-    println(StringContext(Seq.empty[String]:_*).code(Seq.empty[Any]:_*)) // error
+    println(StringContext(Seq.empty[String]*).code(Seq.empty[Any]*)) // error
   }
 
 }

tests/patmat/exhaustive_heuristics.scala

@@ -18,8 +18,8 @@ object Test {
   // well, in truth, we do rewrite List() to Nil, but otherwise we do nothing
   // the full rewrite List(a, b) to a :: b :: Nil, for example is planned (but not sure it's a good idea)
   List(true, false) match {
-    case List(_, _, _:_*) =>
-    case List(node, _:_*)  =>
+    case List(_, _, _*) =>
+    case List(node, _*)  =>
     case Nil =>
   }
 

tests/pos-deep-subtype/i7580.scala

@@ -1,5 +1,5 @@
 
 def foo =
-  val List(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a22, a23, _:_*) = List.fill(25)(0)
+  val List(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a22, a23, _*) = List.fill(25)(0)
 
   ()

tests/pos-special/stdlib/collection/StringOps.scala

@@ -862,7 +862,7 @@ final class StringOps(private val s: String) extends AnyVal {
     *  @param groupNames The names of the groups in the pattern, in the order they appear.
     */
   @deprecated("use inline group names like (?<year>X) instead", "2.13.7")
-  def r(groupNames: String*): Regex = new Regex(s, groupNames: _*)
+  def r(groupNames: String*): Regex = new Regex(s, groupNames*)
 
   /**
    * @throws java.lang.IllegalArgumentException  If the string does not contain a parsable `Boolean`.
@@ -987,7 +987,7 @@ final class StringOps(private val s: String) extends AnyVal {
     *  @throws java.lang.IllegalArgumentException
     */
   def format(args : Any*): String =
-    java.lang.String.format(s, args map unwrapArg: _*)
+    java.lang.String.format(s, args map unwrapArg*)
 
   /** Like `format(args*)` but takes an initial `Locale` parameter
     *  which influences formatting as in `java.lang.String`'s format.
@@ -1003,7 +1003,7 @@ final class StringOps(private val s: String) extends AnyVal {
     *  @throws java.lang.IllegalArgumentException
     */
   def formatLocal(l: java.util.Locale, args: Any*): String =
-    java.lang.String.format(l, s, args map unwrapArg: _*)
+    java.lang.String.format(l, s, args map unwrapArg*)
 
   def compare(that: String): Int = s.compareTo(that)
 

tests/pos-special/stdlib/collection/View.scala

@@ -80,7 +80,7 @@ object View extends IterableFactory[View] {
 
   def newBuilder[A]: Builder[A, View[A]] = ArrayBuffer.newBuilder[A].mapResult(from)
 
-  override def apply[A](xs: A*): View[A] = new Elems(xs: _*)
+  override def apply[A](xs: A*): View[A] = new Elems(xs*)
 
   /** The empty view */
   @SerialVersionUID(3L)

tests/pos/i13349.scala

@@ -26,6 +26,6 @@ object Stream {
   def empty[A]: Stream[A] = Empty
 
   def apply[A](as: A*): Stream[A] =
-    if (as.isEmpty) empty else cons(as.head, apply(as.tail: _*))
+    if (as.isEmpty) empty else cons(as.head, apply(as.tail*))
 
 }

tests/pos/i16105.scala

@@ -6,7 +6,7 @@ trait QuerySQLSyntaxProvider[S <: SQLSyntaxSupport[A], A]{
 }
 
 def include(syntaxProviders: QuerySQLSyntaxProvider[_, _]*) = {
-  syntax(syntaxProviders.map(_.resultName): _*)
+  syntax(syntaxProviders.map(_.resultName)*)
 }
 
 def syntax(resultNames: ResultNameSQLSyntaxProvider[_, _]*) = ???

tests/pos/i16562.scala

@@ -2,7 +2,7 @@ class Test:
   val a: Array[Any] = Array[Any]()
   val b: Array[Any] = Array[Any]()
 
-  def ko(p: Boolean): Unit = foo((if p then a else b): _*)
-  def ok(p: Boolean): Unit = foo({ val x = if p then a else b; x }: _*)
+  def ko(p: Boolean): Unit = foo((if p then a else b)*)
+  def ok(p: Boolean): Unit = foo({ val x = if p then a else b; x }*)
 
   def foo(in: Any*): Unit = ()

tests/pos/i4984.scala

@@ -17,10 +17,10 @@ class Test {
   }
 
   def test2(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(x, y, xs:_*) => xs
+    case Array2(x, y, xs*) => xs
   }
 
   def test3(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(xs:_*) => xs
+    case Array2(xs*) => xs
   }
 }

tests/pos/i5039.scala

@@ -1,5 +1,5 @@
 class I0 {
-  List(null:_*)
-  List[Null](null:_*)
-  List[Nothing](null:_*)
+  List(null*)
+  List[Null](null*)
+  List[Nothing](null*)
 }

tests/pos/i9050.scala

@@ -3,5 +3,5 @@ object Foo {
   val foo = scala.collection.mutable.ArrayBuffer.empty[Seq[Double]]
   val bar = Seq.empty[Double]
   foo.append(bar)
-  foo.append(Seq(bar):_*)
+  foo.append(Seq(bar)*)
 }

tests/pos/t0305.scala

@@ -3,5 +3,5 @@ object Test extends App {
   def foo(is:Int*) = 1;
   def foo(i:Int) = 2;
 
-  assert(foo( List(3):_* ) == 1)
+  assert(foo( List(3)* ) == 1)
 }

tests/run-macros/f-interpolator-tests.scala

@@ -401,7 +401,7 @@ object StringContextTestUtils:
     // Use this String interpolator to avoid problems with a locale-dependent decimal mark.
     def locally(numbers: String*): String =
       val numbersWithCorrectLocale = numbers.map(applyProperLocale)
-      sc.s(numbersWithCorrectLocale: _*)
+      sc.s(numbersWithCorrectLocale*)
 
     // Handles cases like locally"3.14" - it's prettier than locally"${"3.14"}".
     def locally(): String = sc.parts.map(applyProperLocale).mkString

tests/run-macros/refined-selectable-macro/Macro_2.scala

@@ -17,7 +17,7 @@ object Macro2 {
     inline def apply[R <: Record](elems: (String, Any)*) : R = ${ applyImpl[R]('elems) }
 
     def applyImpl[R <: Record: Type](elems: Expr[Seq[(String, Any)]])(using Quotes) = {
-      '{ new Record($elems:_*).asInstanceOf[R] }
+      '{ new Record($elems*).asInstanceOf[R] }
     }
 
     def fromUntypedTuple(elems: (String, Any)*): Record = new Record(elems*)

tests/run/i4984b.scala

@@ -17,11 +17,11 @@ object Test {
   }
 
   def test2(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(x, y, xs:_*) => xs
+    case Array2(x, y, xs*) => xs
   }
 
   def test3(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(xs:_*) => xs
+    case Array2(xs*) => xs
   }
 
   def main(args: Array[String]): Unit = {

tests/run/i4984c.scala

@@ -17,11 +17,11 @@ object Test {
   }
 
   def test2(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(x, y, xs:_*) => xs
+    case Array2(x, y, xs*) => xs
   }
 
   def test3(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(xs:_*) => xs
+    case Array2(xs*) => xs
   }
 
   def main(args: Array[String]): Unit = {

tests/run/i4984d.scala

@@ -20,11 +20,11 @@ object Test {
   }
 
   def test2(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(x, y, xs:_*) => xs
+    case Array2(x, y, xs*) => xs
   }
 
   def test3(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(xs:_*) => xs
+    case Array2(xs*) => xs
   }
 
   def main(args: Array[String]): Unit = {

tests/run/i4984e.scala

@@ -21,11 +21,11 @@ object Test {
   }
 
   def test2(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(x, y, xs:_*) => xs
+    case Array2(x, y, xs*) => xs
   }
 
   def test3(xs: Array[Int]): Seq[Int] = xs match {
-    case Array2(xs:_*) => xs
+    case Array2(xs*) => xs
   }
 
   def main(args: Array[String]): Unit = {

tests/run/i8977.scala

@@ -3,9 +3,9 @@ object Test {
 
   def main(args: Array[String]): Unit = {
     System.out.printf("pi = %6.4f\n", pi)
-    System.out.printf("pi = %6.4f\n", Seq[scala.Double](pi):_*)
-    System.out.printf("pi = %6.4f\n", Seq[java.lang.Double](pi):_*)
-    System.out.printf("pi = %6.4f\n", Array[scala.Double](pi):_*)
-    System.out.printf("pi = %6.4f\n", Array[java.lang.Double](pi):_*)
+    System.out.printf("pi = %6.4f\n", Seq[scala.Double](pi)*)
+    System.out.printf("pi = %6.4f\n", Seq[java.lang.Double](pi)*)
+    System.out.printf("pi = %6.4f\n", Array[scala.Double](pi)*)
+    System.out.printf("pi = %6.4f\n", Array[java.lang.Double](pi)*)
   }
 }

tests/run/iterator-from.scala

@@ -56,13 +56,13 @@ object Test extends App {
   0 until maxLength foreach {length =>
     val keyValues = (0 until length map {_ => (R nextInt maxKey, R nextInt maxValue)}).toList
     val keys = keyValues map (_._2)
-    testSet(immutable.BitSet(keys:_*), keys)
-    testSet(immutable.TreeSet(keys:_*), keys)
-    testSet(mutable.TreeSet(keys:_*), keys)
+    testSet(immutable.BitSet(keys*), keys)
+    testSet(immutable.TreeSet(keys*), keys)
+    testSet(mutable.TreeSet(keys*), keys)
     val days = keys map {n => Weekday(n % Weekday.values.size)}
-    testSet(Weekday.ValueSet(days:_*), days)
+    testSet(Weekday.ValueSet(days*), days)
 
-    val treeMap = immutable.TreeMap(keyValues:_*)
+    val treeMap = immutable.TreeMap(keyValues*)
     testMap(treeMap, keyValues)
     testMap(treeMap.view.filterKeys(_ % 2 == 0).to(SortedMap), keyValues  filter (_._1 % 2 == 0))
     testMap(treeMap.view.mapValues(_ + 1).to(SortedMap), keyValues map {case (k,v) => (k, v + 1)})