Merge pull request #771 from retronym/ticket/4176-2

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

2 files changed, 17 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
index 177d1ddf19..69b27045ab 100644
--- a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
@@ -109,11 +109,20 @@ 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 d251109dc4..a167180267 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -4686,7 +4686,10 @@ 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)
           }
         }
       }