Existential printing, plus more compiler testing infrastructure.

Direct compiler internals testing. It's really easy, you should probably
use it about 1000 times each. Look at the test:

  run/existentials-in-compiler.scala

The checkfile contains the (string representations of the) actual
existentials from the compiler to make sure they correspond properly to
the ones in the source.

Existentials were being printed with wildcards too freely; this has been
tightened up.

1 files changed, 20 insertions, 8 deletions

diff --git a/src/compiler/scala/reflect/internal/Definitions.scala b/src/compiler/scala/reflect/internal/Definitions.scala
index e05ac1087b..5b2c61701d 100644
--- a/src/compiler/scala/reflect/internal/Definitions.scala
+++ b/src/compiler/scala/reflect/internal/Definitions.scala
@@ -586,14 +586,6 @@ trait Definitions extends reflect.api.StandardDefinitions {
       case _                                    => NoType
     }
 
-    /** To avoid unchecked warnings on polymorphic classes, translate
-     *  a Foo[T] into a Foo[_] for use in the pattern matcher.
-     */
-    def typeCaseType(clazz: Symbol) = clazz.tpe.normalize match {
-      case TypeRef(_, sym, args) if args.nonEmpty => newExistentialType(sym.typeParams, clazz.tpe)
-      case tp                                     => tp
-    }
-
     def seqType(arg: Type)       = appliedType(SeqClass.typeConstructor, List(arg))
     def arrayType(arg: Type)     = appliedType(ArrayClass.typeConstructor, List(arg))
     def byNameType(arg: Type)    = appliedType(ByNameParamClass.typeConstructor, List(arg))
@@ -609,6 +601,26 @@ trait Definitions extends reflect.api.StandardDefinitions {
     def vmClassType(arg: Type): Type = ClassType(arg)
     def vmSignature(sym: Symbol, info: Type): String = signature(info)    // !!!
 
+    /** Given a class symbol C with type parameters T1, T2, ... Tn
+     *  which have upper/lower bounds LB1/UB1, LB1/UB2, ..., LBn/UBn,
+     *  returns an existential type of the form
+     *
+     *    C[E1, ..., En] forSome { E1 >: LB1 <: UB1 ... en >: LBn <: UBn }.
+     */
+    def classExistentialType(clazz: Symbol): Type =
+      newExistentialType(clazz.typeParams, clazz.tpe)
+
+    /** Given type U, creates a Type representing Class[_ <: U].
+     */
+    def boundedClassType(upperBound: Type) =
+      appliedTypeAsUpperBounds(ClassClass.typeConstructor, List(upperBound))
+
+    /** To avoid unchecked warnings on polymorphic classes, translate
+     *  a Foo[T] into a Foo[_] for use in the pattern matcher.
+     */
+    @deprecated("Use classExistentialType", "2.10.0")
+    def typeCaseType(clazz: Symbol): Type = classExistentialType(clazz)
+
     //
     // .NET backend
     //