SI-7556 Fix runtime reflection involving ScalaLongSignature

Scala type information is stored in classfiles in encoded in a String
in the ScalaSignature annotation. When it is too big for a single
String, it is split into an array of Strings in a different annotation,
ScalaLongSignature.

The enclosed test, with a class containing 3000 methods, uses the latter.
It exposes a bug in the way runtime reflection decodes that data.

It must concatentate and *then* decode, rather that the other way around.

1 files changed, 4 insertions, 9 deletions

diff --git a/src/reflect/scala/reflect/runtime/JavaMirrors.scala b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
index ccc727451c..55f08f0586 100644
--- a/src/reflect/scala/reflect/runtime/JavaMirrors.scala
+++ b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
@@ -567,15 +567,10 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni
             loadBytes[Array[String]]("scala.reflect.ScalaLongSignature") match {
               case Some(slsig) =>
                 info(s"unpickling Scala $clazz and $module with long Scala signature")
-                val byteSegments = slsig map (_.getBytes)
-                val lens = byteSegments map ByteCodecs.decode
-                val bytes = Array.ofDim[Byte](lens.sum)
-                var len = 0
-                for ((bs, l) <- byteSegments zip lens) {
-                  bs.copyToArray(bytes, len, l)
-                  len += l
-                }
-                unpickler.unpickle(bytes, 0, clazz, module, jclazz.getName)
+                val encoded = slsig flatMap (_.getBytes)
+                val len = ByteCodecs.decode(encoded)
+                val decoded = encoded.take(len)
+                unpickler.unpickle(decoded, 0, clazz, module, jclazz.getName)
               case None =>
                 // class does not have a Scala signature; it's a Java class
                 info("translating reflection info for Java " + jclazz) //debug