Fix for SI-5859, inapplicable varargs.

And other polishing related to varargs handling.

7 files changed, 50 insertions, 38 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
index b04a736fd3..059d32fcb5 100644
--- a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
@@ -118,7 +118,7 @@ trait EtaExpansion { self: Analyzer =>
             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 droppedStarTpe = if (settings.etaExpandKeepsStar.value) origTpe else dropIllegalStarTypes(origTpe)
             val valDef = ValDef(Modifiers(SYNTHETIC | PARAM), sym.name.toTermName, TypeTree(droppedStarTpe), EmptyTree)
             (valDef, isRepeated)
         }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
index 48abfd7a2c..6558379c51 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -1593,10 +1593,10 @@ trait Infer extends Checkable {
         }
         // Drop those that use a default; keep those that use vararg/tupling conversion.
         mtypes exists (t =>
-          !t.typeSymbol.hasDefaultFlag && {
-            compareLengths(t.params, argtpes) < 0 ||  // tupling (*)
-            hasExactlyNumParams(t, argtpes.length)    // same nb or vararg
-          }
+          !t.typeSymbol.hasDefaultFlag && (
+               compareLengths(t.params, argtpes) < 0  // tupling (*)
+            || hasExactlyNumParams(t, argtpes.length) // same nb or vararg
+          )
         )
         // (*) more arguments than parameters, but still applicable: tupling conversion works.
         //     todo: should not return "false" when paramTypes = (Unit) no argument is given
@@ -1623,15 +1623,18 @@ trait Infer extends Checkable {
       case OverloadedType(pre, alts) =>
         val pt = if (pt0.typeSymbol == UnitClass) WildcardType else pt0
         tryTwice { isSecondTry =>
-          debuglog("infer method alt "+ tree.symbol +" with alternatives "+
-                (alts map pre.memberType) +", argtpes = "+ argtpes +", pt = "+ pt)
+          debuglog(s"infer method alt ${tree.symbol} with alternatives ${alts map pre.memberType} argtpes=$argtpes pt=$pt")
 
-          val applicable = resolveOverloadedMethod(argtpes, {
-            alts filter { alt =>
-              inSilentMode(context)(isApplicable(undetparams, followApply(pre.memberType(alt)), argtpes, pt)) &&
-              (!varArgsOnly || isVarArgsList(alt.tpe.params))
-            }
-          })
+          def varargsApplicableCheck(alt: Symbol) = !varArgsOnly || (
+               isVarArgsList(alt.tpe.params)
+            && (argtpes.size >= alt.tpe.params.size) // must be checked now due to SI-5859
+          )
+          val applicable = resolveOverloadedMethod(argtpes,
+            alts filter (alt =>
+                 varargsApplicableCheck(alt)
+              && inSilentMode(context)(isApplicable(undetparams, followApply(pre memberType alt), argtpes, pt))
+            )
+          )
 
           def improves(sym1: Symbol, sym2: Symbol) = {
             // util.trace("improve "+sym1+sym1.locationString+" on "+sym2+sym2.locationString)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index abd433b929..f562a251e3 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -800,7 +800,7 @@ trait Namers extends MethodSynthesis {
           false
       }
 
-      val tpe1 = dropRepeatedParamType(tpe.deconst)
+      val tpe1 = dropIllegalStarTypes(tpe.deconst)
       val tpe2 = tpe1.widen
 
       // This infers Foo.type instead of "object Foo"
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 5e1f52830c..4b08f3ee80 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -60,23 +60,8 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
     super.transformInfo(sym, tp)
   }
 
-  val toJavaRepeatedParam = new TypeMap {
-    def apply(tp: Type) = tp match {
-      case TypeRef(pre, RepeatedParamClass, args) =>
-        typeRef(pre, JavaRepeatedParamClass, args)
-      case _ =>
-        mapOver(tp)
-    }
-  }
-
-  val toScalaRepeatedParam = new TypeMap {
-    def apply(tp: Type): Type = tp match {
-      case TypeRef(pre, JavaRepeatedParamClass, args) =>
-        typeRef(pre, RepeatedParamClass, args)
-      case _ =>
-        mapOver(tp)
-    }
-  }
+  val toJavaRepeatedParam  = new SubstSymMap(RepeatedParamClass -> JavaRepeatedParamClass)
+  val toScalaRepeatedParam = new SubstSymMap(JavaRepeatedParamClass -> RepeatedParamClass)
 
   def accessFlagsToString(sym: Symbol) = flagsToString(
     sym getFlag (PRIVATE | PROTECTED),
@@ -1483,8 +1468,11 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
     }
     private def isRepeatedParamArg(tree: Tree) = currentApplication match {
       case Apply(fn, args) =>
-        !args.isEmpty && (args.last eq tree) &&
-        fn.tpe.params.length == args.length && isRepeatedParamType(fn.tpe.params.last.tpe)
+        (    args.nonEmpty
+          && (args.last eq tree)
+          && (fn.tpe.params.length == args.length)
+          && isRepeatedParamType(fn.tpe.params.last.tpe)
+        )
       case _ =>
         false
     }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 3a443ea2c0..dc6beaf5c6 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -4988,7 +4988,7 @@ trait Typers extends Modes with Adaptations with Tags {
             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)
+            tree3 setType dropIllegalStarTypes(tree3.tpe)
           }
         }
       }
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index 2c036b3308..97ad02c8a9 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -3800,12 +3800,16 @@ trait Types extends api.Types { self: SymbolTable =>
   //   This is the specified behavior.
   protected def etaExpandKeepsStar = false
 
-  object dropRepeatedParamType extends TypeMap {
+  /** Turn any T* types into Seq[T] except when
+   *  in method parameter position.
+   */
+  object dropIllegalStarTypes extends TypeMap {
     def apply(tp: Type): Type = tp match {
       case MethodType(params, restpe) =>
-        MethodType(params, apply(restpe))
-      case PolyType(tparams, restpe) =>
-        PolyType(tparams, apply(restpe))
+        // Not mapping over params
+        val restpe1 = apply(restpe)
+        if (restpe eq restpe1) tp
+        else MethodType(params, restpe1)
       case TypeRef(_, RepeatedParamClass, arg :: Nil) =>
         seqType(arg)
       case _ =>
@@ -4618,6 +4622,8 @@ trait Types extends api.Types { self: SymbolTable =>
 
   /** A map to implement the `substSym` method. */
   class SubstSymMap(from: List[Symbol], to: List[Symbol]) extends SubstMap(from, to) {
+    def this(pairs: (Symbol, Symbol)*) = this(pairs.toList.map(_._1), pairs.toList.map(_._2))
+
     protected def toType(fromtp: Type, sym: Symbol) = fromtp match {
       case TypeRef(pre, _, args) => copyTypeRef(fromtp, pre, sym, args)
       case SingleType(pre, _) => singleType(pre, sym)
diff --git a/test/files/pos/t5859.scala b/test/files/pos/t5859.scala
new file mode 100644
index 0000000000..2a31e68ee5
--- /dev/null
+++ b/test/files/pos/t5859.scala
@@ -0,0 +1,15 @@
+
+class A {
+  def f(xs: List[Int], ys: AnyRef*) = ()
+  def f(xs: AnyRef*) = ()
+
+  f()
+  f(List[AnyRef](): _*)
+  f(List(): _*)
+  f(Nil: _*)
+  f(Array(): _*)
+  f(Array[AnyRef](): _*)
+  f(List(1))
+  f(List(1), Nil: _*)
+  f(List(1), Array(): _*)
+}