Flipped varargs eta-expansion behavior.

(T*)U now eta-expands to Seq[T] => U, not T* => U.  There is a
transition command line switch to get the old behavior for any who
may have relied upon it:

  -Yeta-expand-keeps-star

Closes SI-4176, no review.

git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@25809 5e8d7ff9-d8ef-0310-90f0-a4852d11357a

src/compiler/scala/reflect/internal/Types.scala

@@ -3092,7 +3092,7 @@ A type's typeSymbol should never be inspected directly.
   // Or false for Seq[A] => Seq[A]
   //   (It will rewrite A* everywhere but method parameters.)
   //   This is the specified behavior.
-  private final val etaExpandKeepsStar = true
+  protected def etaExpandKeepsStar = false
   
   object dropRepeatedParamType extends TypeMap {
     def apply(tp: Type): Type = tp match {

src/compiler/scala/tools/nsc/Global.scala

@@ -300,6 +300,12 @@ class Global(var currentSettings: Settings, var reporter: Reporter) extends Symb
     def lubDebug      = (sys.props contains "scalac.debug.lub")
   }
 
+  // The current division between scala.reflect.* and scala.tools.nsc.* is pretty
+  // clunky.  It is often difficult to have a setting influence something without having
+  // to create it on that side.  For this one my strategy is a constant def at the file
+  // where I need it, and then an override in Global with the setting.
+  override protected val etaExpandKeepsStar = settings.etaExpandKeepsStar.value
+
   // True if -Xscript has been set, indicating a script run.
   def isScriptRun = opt.script.isDefined
 

src/compiler/scala/tools/nsc/settings/ScalaSettings.scala

@@ -168,6 +168,7 @@ trait ScalaSettings extends AbsScalaSettings
   val Ynotnull      = BooleanSetting    ("-Ynotnull", "Enable (experimental and incomplete) scala.NotNull.")
   val YdepMethTpes  = BooleanSetting    ("-Ydependent-method-types", "Allow dependent method types.")
   val YmethodInfer  = BooleanSetting    ("-Yinfer-argument-types", "Infer types for arguments of overriden methods.")
+  val etaExpandKeepsStar = BooleanSetting("-Yeta-expand-keeps-star", "Eta-expand varargs methods to T* rather than Seq[T].  This is a temporary option to ease transition.")
   val noSelfCheck   = BooleanSetting    ("-Yno-self-type-checks", "Suppress check for self-type conformance among inherited members.")
   val YvirtClasses  = false // too embryonic to even expose as a -Y //BooleanSetting    ("-Yvirtual-classes", "Support virtual classes")
 

test/files/neg/eta-expand-star.check

@@ -0,0 +1,4 @@
+eta-expand-star.scala:6: error: too many arguments for method apply: (v1: Seq[T])Unit in trait Function1
+    g(1, 2)
+     ^
+one error found

test/files/neg/eta-expand-star.scala

@@ -0,0 +1,8 @@
+object Test {
+  def f[T](xs: T*): Unit = ()
+  def g[T] = f[T] _
+
+  def main(args: Array[String]): Unit = {
+    g(1, 2)
+  }
+}

test/files/run/byname.scala

@@ -36,13 +36,13 @@ def testVarargs(x: Int*) = x.reduceLeft((x: Int, y: Int) => x + y)
 test("varargs", 4, testVarargs(1, 2, 1))
 
 val testVarargsR = testVarargs _
-test("varargs r", 4, testVarargsR(1, 2, 1))
+test("varargs r", 4, testVarargsR(Seq(1, 2, 1)))
 
 def testAll(x: Int, y: => Int, z: Int*) = x + y + z.size
 test("all", 5, testAll(1, 2, 22, 23))
 
 val testAllR = testAll _
-test("all r", 7, testAllR(2, 3, 34, 35))
+test("all r", 7, testAllR(2, 3, Seq(34, 35)))
 
 val testAllS: (Int, =>Int, Int*) => Int = testAll _
 test("all s", 8, testAllS(1, 5, 78, 89))
@@ -73,7 +73,7 @@ def testCVV(a: Int*)(z: String, b: Int*) = a.size + b.size
 test("cvv", 3, testCVV(1, 2)("", 8))
 
 val testCVVR = testCVV _
-test("cvv r", 3, testCVVR(1)("", 8, 9))
+test("cvv r", 3, testCVVR(Seq(1))("", Seq(8, 9)))
 
 val testCVVRS: (String, Int*) => Int = testCVV(2, 3)
 test("cvv rs", 4, testCVVRS("", 5, 6))

test/files/run/eta-expand-star.check

@@ -0,0 +1 @@
+hello

test/files/run/eta-expand-star.scala

@@ -0,0 +1,8 @@
+object Test {
+  def f[T](xs: T*): T = xs.head
+  def g[T] = f[T] _
+
+  def main(args: Array[String]): Unit = {
+    println(g("hello" +: args))
+  }
+}

test/files/run/eta-expand-star2.check

@@ -0,0 +1 @@
+hello

test/files/run/eta-expand-star2.flags

@@ -0,0 +1 @@
+-Yeta-expand-keeps-star

test/files/run/eta-expand-star2.scala

@@ -0,0 +1,8 @@
+object Test {
+  def f[T](xs: T*): T = xs.head
+  def g[T] = f[T] _
+
+  def main(args: Array[String]): Unit = {
+    println(g("hello"))
+  }
+}