SI-4176 A repeat dose of repeated parameter type sanitization.

 - During eta expansion, treat parameters of type A* as Seq[A]
 - Do the same for method/class parameters as referred to by an Ident.

Also fixes SI-5967, which shows up during pattern matching.

5 files changed, 35 insertions, 15 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/TreeGen.scala b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
index 3a527676b4..be5909a67f 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeGen.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
@@ -213,17 +213,14 @@ abstract class TreeGen extends reflect.internal.TreeGen with TreeDSL {
   def wildcardStar(tree: Tree) =
     atPos(tree.pos) { Typed(tree, Ident(tpnme.WILDCARD_STAR)) }
 
-  def paramToArg(vparam: Symbol) = {
-    val arg = Ident(vparam)
-    if (isRepeatedParamType(vparam.tpe)) wildcardStar(arg)
-    else arg
-  }
+  def paramToArg(vparam: Symbol): Tree =
+    paramToArg(Ident(vparam), isRepeatedParamType(vparam.tpe))
 
-  def paramToArg(vparam: ValDef) = {
-    val arg = Ident(vparam.name)
-    if (treeInfo.isRepeatedParamType(vparam.tpt)) wildcardStar(arg)
-    else arg
-  }
+  def paramToArg(vparam: ValDef): Tree =
+    paramToArg(Ident(vparam.name), treeInfo.isRepeatedParamType(vparam.tpt))
+
+  def paramToArg(arg: Ident, isRepeatedParam: Boolean): Tree  =
+    if (isRepeatedParam) wildcardStar(arg) else arg
 
   /** Make forwarder to method `target`, passing all parameters in `params` */
   def mkForwarder(target: Tree, vparamss: List[List[Symbol]]) =
diff --git a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
index e1fb683aa9..a4d9cdaffe 100644
--- a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
@@ -107,11 +107,20 @@ trait EtaExpansion { self: Analyzer =>
      */
     def expand(tree: Tree, tpe: Type): Tree = tpe match {
       case mt @ MethodType(paramSyms, restpe) if !mt.isImplicit =>
-        val params = paramSyms map (sym =>
-          ValDef(Modifiers(SYNTHETIC | PARAM),
-                 sym.name.toTermName, TypeTree(sym.tpe) , EmptyTree))
+        val params: List[(ValDef, Boolean)] = paramSyms.map {
+          sym =>
+            val origTpe = sym.tpe
+            val isRepeated = definitions.isRepeatedParamType(origTpe)
+            // SI-4176 Don't leak A* in eta-expanded function types. See t4176b.scala
+            val droppedStarTpe = if (settings.etaExpandKeepsStar.value) origTpe else dropRepeatedParamType(origTpe)
+            val valDef = ValDef(Modifiers(SYNTHETIC | PARAM), sym.name.toTermName, TypeTree(droppedStarTpe), EmptyTree)
+            (valDef, isRepeated)
+        }
         atPos(tree.pos.makeTransparent) {
-          Function(params, expand(Apply(tree, params map gen.paramToArg), restpe))
+          val args = params.map {
+            case (valDef, isRepeated) => gen.paramToArg(Ident(valDef.name), isRepeated)
+          }
+          Function(params.map(_._1), expand(Apply(tree, args), restpe))
         }
       case _ =>
         tree
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 69d3fd7f47..04d9d67d68 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -4687,7 +4687,10 @@ trait Typers extends Modes with Adaptations with Tags {
             )
             val (tree2, pre2) = makeAccessible(tree1, defSym, pre, qual)
             // assert(pre.typeArgs isEmpty) // no need to add #2416-style check here, right?
-            stabilize(tree2, pre2, mode, pt)
+            val tree3 = stabilize(tree2, pre2, mode, pt)
+            // SI-5967 Important to replace param type A* with Seq[A] when seen from from a reference, to avoid
+            //         inference errors in pattern matching.
+            tree3 setType dropRepeatedParamType(tree3.tpe)
           }
         }
       }
diff --git a/test/files/pos/t4176b.scala b/test/files/pos/t4176b.scala
new file mode 100644
index 0000000000..11914c50c8
--- /dev/null
+++ b/test/files/pos/t4176b.scala
@@ -0,0 +1,5 @@
+object Test {
+	 def foo(a: String*) = a
+	 val fooEta = foo _
+	 (foo: Seq[String] => Seq[String])
+}
diff --git a/test/files/pos/t5967.scala b/test/files/pos/t5967.scala
new file mode 100644
index 0000000000..eb9bd6dfa7
--- /dev/null
+++ b/test/files/pos/t5967.scala
@@ -0,0 +1,6 @@
+object Test {
+	def f(a: Int*) = a match {
+	  case 0 :: Nil => "List(0)! My favorite Seq!"
+	  case _ => a.toString
+	}
+}