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

10 files changed, 49 insertions, 44 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)
   }
diff --git a/test/files/run/classtags_core.check b/test/files/run/classtags_core.check
index 6519db2178..5a9b41fd6d 100644
--- a/test/files/run/classtags_core.check
+++ b/test/files/run/classtags_core.check
@@ -1,30 +1,30 @@
 true

-ClassTag[byte]

+Byte

 true

-ClassTag[short]

+Short

 true

-ClassTag[char]

+Char

 true

-ClassTag[int]

+Int

 true

-ClassTag[long]

+Long

 true

-ClassTag[float]

+Float

 true

-ClassTag[double]

+Double

 true

-ClassTag[boolean]

+Boolean

 true

-ClassTag[void]

+Unit

 true

-ClassTag[class java.lang.Object]

+Any

 true

-ClassTag[class java.lang.Object]

+AnyVal

 true

-ClassTag[class java.lang.Object]

+Object

 true

-ClassTag[class java.lang.Object]

+Object

 true

-ClassTag[class scala.runtime.Null$]

+Null

 true

-ClassTag[class scala.runtime.Nothing$]

+Nothing

diff --git a/test/files/run/classtags_multi.check b/test/files/run/classtags_multi.check
index 3a7f16c3a0..68cee4841d 100644
--- a/test/files/run/classtags_multi.check
+++ b/test/files/run/classtags_multi.check
@@ -1,5 +1,5 @@
-ClassTag[int]

-ClassTag[class [I]

-ClassTag[class [[I]

-ClassTag[class [[[I]

-ClassTag[class [[[[I]

+Int

+Array[int]

+Array[Array[int]]

+Array[Array[Array[int]]]

+Array[Array[Array[Array[int]]]]

diff --git a/test/files/run/interop_classtags_are_classmanifests.check b/test/files/run/interop_classtags_are_classmanifests.check
index 7a0a829af2..c07ed0e657 100644
--- a/test/files/run/interop_classtags_are_classmanifests.check
+++ b/test/files/run/interop_classtags_are_classmanifests.check
@@ -1,3 +1,3 @@
-ClassTag[int]

-ClassTag[class java.lang.String]

-ClassTag[class [I]

+Int

+java.lang.String

+Array[int]

diff --git a/test/files/run/t5881.check b/test/files/run/t5881.check
index 477fb935a8..8e596e9323 100644
--- a/test/files/run/t5881.check
+++ b/test/files/run/t5881.check
@@ -1,2 +1,2 @@
-ClassTag[class scala.collection.immutable.List]

-ClassTag[class scala.collection.immutable.List]

+scala.collection.immutable.List

+scala.collection.immutable.List

diff --git a/test/files/run/valueclasses-classtag-basic.check b/test/files/run/valueclasses-classtag-basic.check
index 0c13986b32..554c75e074 100644
--- a/test/files/run/valueclasses-classtag-basic.check
+++ b/test/files/run/valueclasses-classtag-basic.check
@@ -1 +1 @@
-ClassTag[class Foo]

+Foo

diff --git a/test/files/run/valueclasses-classtag-existential.check b/test/files/run/valueclasses-classtag-existential.check
index 95e94e7aee..15ac02630f 100644
--- a/test/files/run/valueclasses-classtag-existential.check
+++ b/test/files/run/valueclasses-classtag-existential.check
@@ -1 +1 @@
-ClassTag[class java.lang.Object]

+Object

diff --git a/test/files/run/valueclasses-classtag-generic.check b/test/files/run/valueclasses-classtag-generic.check
index 0c13986b32..554c75e074 100644
--- a/test/files/run/valueclasses-classtag-generic.check
+++ b/test/files/run/valueclasses-classtag-generic.check
@@ -1 +1 @@
-ClassTag[class Foo]

+Foo

diff --git a/test/files/run/virtpatmat_typetag.check b/test/files/run/virtpatmat_typetag.check
index f9800b84d0..eaa9f3361f 100644
--- a/test/files/run/virtpatmat_typetag.check
+++ b/test/files/run/virtpatmat_typetag.check
@@ -1,10 +1,10 @@
-1 is not a ClassTag[int]; it's a class java.lang.Integer
-1 is a ClassTag[class java.lang.Integer]
-1 is not a ClassTag[class java.lang.String]; it's a class java.lang.Integer
-true is a ClassTag[class java.lang.Object]
-woele is a ClassTag[class java.lang.String]
-1 is not a ClassTag[int]; it's a class java.lang.Integer
-1 is a ClassTag[class java.lang.Integer]
-1 is not a ClassTag[class java.lang.String]; it's a class java.lang.Integer
-true is a ClassTag[class java.lang.Object]
-woele is a ClassTag[class java.lang.String]
+1 is not a Int; it's a class java.lang.Integer

+1 is a java.lang.Integer

+1 is not a java.lang.String; it's a class java.lang.Integer

+true is a Any

+woele is a java.lang.String

+1 is not a Int; it's a class java.lang.Integer

+1 is a java.lang.Integer

+1 is not a java.lang.String; it's a class java.lang.Integer

+true is a Any

+woele is a java.lang.String