SI-8376 Fix overload resolution with Java varargs

When comparing specificity of two vararg `MethodTypes`, `isAsSpecific`
gets to:

```
  case mt @ MethodType(_, _) if bothAreVarargs =>
    checkIsApplicable(mt.paramTypes mapConserve repeatedToSingle)
```

The formal parameter type of a Java varargs parameter is represented
as `tq"${defintions.JavaRepeatedParamClass}[$elemTp]"`. For a Scala
repeated parameter, we instead use `defintions.RepeatedParamClass`.

`bothAreVarargs` detects `JavaRepeatedParamClass`, by virtue of:

```
def isRepeatedParamType(tp: Type)      = isScalaRepeatedParamType(tp) || isJavaRepeatedParamType(tp)
```

But, `repeatedToSingle` only considers `RepeatedParamClass`.

This bug was ostensibly masked in 2.10.3, but became apparent after
a not-quite-refactoring in 0fe56b9770. It would be good to pin that
change down to a particular line, but I haven't managed that yet.

3 files changed, 25 insertions, 1 deletions

diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index 558e1aa611..b2bfceb570 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -410,7 +410,8 @@ trait Definitions extends api.StandardDefinitions {
       else if (isScalaRepeatedParamType(tp)) elementExtract(RepeatedParamClass, tp) orElse tp
       else tp
     )
-    def repeatedToSingle(tp: Type): Type                     = elementExtract(RepeatedParamClass, tp) orElse tp
+    def repeatedToSingle(tp: Type): Type                     = elementExtract(RepeatedParamClass, tp) orElse elementExtract(JavaRepeatedParamClass, tp) orElse tp
+     // We don't need to deal with JavaRepeatedParamClass here, as `repeatedToSeq` is only called in the patmat translation for Scala sources.
     def repeatedToSeq(tp: Type): Type                        = elementTransform(RepeatedParamClass, tp)(seqType) orElse tp
     def seqToRepeated(tp: Type): Type                        = elementTransform(SeqClass, tp)(scalaRepeatedType) orElse tp
     def isReferenceArray(tp: Type)                           = elementTest(ArrayClass, tp)(_ <:< AnyRefTpe)
diff --git a/test/files/pos/t8376/BindingsX.java b/test/files/pos/t8376/BindingsX.java
new file mode 100644
index 0000000000..165fdaf5f6
--- /dev/null
+++ b/test/files/pos/t8376/BindingsX.java
@@ -0,0 +1,13 @@
+/**
+ * A simple Java class implementing methods similar to new JavaFX `Bindings`.
+ */
+public final class BindingsX {
+
+    public static void select(String root, String... steps) {
+        throw new UnsupportedOperationException("Not implemented");
+    }
+
+    public static void select(Object root, String... steps) {
+        throw new UnsupportedOperationException("Not implemented");
+    }
+}
diff --git a/test/files/pos/t8376/Test.scala b/test/files/pos/t8376/Test.scala
new file mode 100644
index 0000000000..ba078a3532
--- /dev/null
+++ b/test/files/pos/t8376/Test.scala
@@ -0,0 +1,10 @@
+class Test {
+  BindingsX.select("", "") // okay in 2.10, fails in 2.11
+
+  BindingsY.select1("", "") // okay in both
+}
+
+object BindingsY {
+  def select1(root: String, steps: String*) = ()  
+  def select1(root: Any, steps: String*) = ()
+}