fixes Manifest.Nothing and Manifest.Null

Also introduces an important change to Manifest.Nothing and Manifest.Null.
Previously their `erasure` was equal to classOf[Object]. Now it's correctly
set to classOf[scala.runtime.Nothing$] and classOf[scala.runtime.Null$]
correspondingly.

See a discussion here:
https://groups.google.com/forum/#!topic/scala-internals/Y0ALGo7QPqE

2 files changed, 11 insertions, 6 deletions

diff --git a/src/library/scala/reflect/ClassTag.scala b/src/library/scala/reflect/ClassTag.scala
index 373fdb4129..aaef959d7c 100644
--- a/src/library/scala/reflect/ClassTag.scala
+++ b/src/library/scala/reflect/ClassTag.scala
@@ -2,7 +2,7 @@ package scala.reflect
 
 import java.lang.{ Class => jClass }
 import language.{implicitConversions, existentials}
-import scala.runtime.ScalaRunTime.{ arrayClass }
+import scala.runtime.ScalaRunTime.{ arrayClass, arrayElementClass }
 
 /** A `ClassTag[T]` wraps a runtime class, which can be accessed via the `runtimeClass` method.
  *
@@ -60,7 +60,12 @@ trait ClassTag[T] extends ClassManifestDeprecatedApis[T] with Equals with Serial
   override def canEqual(x: Any) = x.isInstanceOf[ClassTag[_]]
   override def equals(x: Any) = x.isInstanceOf[ClassTag[_]] && this.runtimeClass == x.asInstanceOf[ClassTag[_]].runtimeClass
   override def hashCode = scala.runtime.ScalaRunTime.hash(runtimeClass)
-  override def toString = "ClassTag[" + runtimeClass + "]"
+  override def toString = {
+    def prettyprint(clazz: jClass[_]): String =
+      if (clazz.isArray) s"Array[${prettyprint(arrayElementClass(clazz))}]" else
+      clazz.getName
+    prettyprint(runtimeClass)
+  }
 }
 
 object ClassTag {
diff --git a/src/library/scala/reflect/Manifest.scala b/src/library/scala/reflect/Manifest.scala
index 8289fdab69..f2a23f4372 100644
--- a/src/library/scala/reflect/Manifest.scala
+++ b/src/library/scala/reflect/Manifest.scala
@@ -176,13 +176,13 @@ object ManifestFactory {
     private def readResolve(): Any = Manifest.AnyVal
   }
 
-  val Null: Manifest[scala.Null] = new PhantomManifest[scala.Null](ObjectTYPE, "Null") {
+  val Null: Manifest[scala.Null] = new PhantomManifest[scala.Null](NullTYPE, "Null") {
     override def <:<(that: ClassManifest[_]): Boolean =
       (that ne null) && (that ne Nothing) && !(that <:< AnyVal)
     private def readResolve(): Any = Manifest.Null
   }
 
-  val Nothing: Manifest[scala.Nothing] = new PhantomManifest[scala.Nothing](ObjectTYPE, "Nothing") {
+  val Nothing: Manifest[scala.Nothing] = new PhantomManifest[scala.Nothing](NothingTYPE, "Nothing") {
     override def <:<(that: ClassManifest[_]): Boolean = (that ne null)
     private def readResolve(): Any = Manifest.Nothing
   }
@@ -217,8 +217,8 @@ object ManifestFactory {
   def classType[T](prefix: Manifest[_], clazz: Predef.Class[_], args: Manifest[_]*): Manifest[T] =
     new ClassTypeManifest[T](Some(prefix), clazz, args.toList)
 
-  private abstract class PhantomManifest[T](override val runtimeClass: Predef.Class[_],
-                                            override val toString: String) extends ClassTypeManifest[T](None, runtimeClass, Nil) {
+  private abstract class PhantomManifest[T](_runtimeClass: Predef.Class[_],
+                                            override val toString: String) extends ClassTypeManifest[T](None, _runtimeClass, Nil) {
     override def equals(that: Any): Boolean = this eq that.asInstanceOf[AnyRef]
     override val hashCode = System.identityHashCode(this)
   }