Add :kind command to REPL

:kind command diplays the kind of types and type constructors in Scala
syntax notation.

    scala> :kind (Int, Int) => Int
    scala.Function2's kind is F[-A1,-A2,+A3]

1 files changed, 42 insertions, 0 deletions

diff --git a/src/repl/scala/tools/nsc/interpreter/package.scala b/src/repl/scala/tools/nsc/interpreter/package.scala
index 52a085080b..f82c38f5e7 100644
--- a/src/repl/scala/tools/nsc/interpreter/package.scala
+++ b/src/repl/scala/tools/nsc/interpreter/package.scala
@@ -10,6 +10,7 @@ import scala.reflect.{ classTag, ClassTag }
 import scala.reflect.runtime.{ universe => ru }
 import scala.reflect.{ClassTag, classTag}
 import scala.reflect.api.{Mirror, TypeCreator, Universe => ApiUniverse}
+import scala.util.control.Exception.catching
 
 /** The main REPL related classes and values are as follows.
  *  In addition to standard compiler classes Global and Settings, there are:
@@ -127,6 +128,47 @@ package object interpreter extends ReplConfig with ReplStrings {
       ""
     }
 
+    def kindCommandInternal(expr: String, verbose: Boolean): Unit = {
+      val catcher = catching(classOf[MissingRequirementError],
+                             classOf[ScalaReflectionException])
+      def typeFromTypeString: Option[ClassSymbol] = catcher opt {
+        exprTyper.typeOfTypeString(expr).typeSymbol.asClass
+      }
+      def typeFromNameTreatedAsTerm: Option[ClassSymbol] = catcher opt {
+        val moduleClass = exprTyper.typeOfExpression(expr).typeSymbol
+        moduleClass.linkedClassOfClass.asClass
+      }
+      def typeFromFullName: Option[ClassSymbol] = catcher opt {
+        intp.global.rootMirror.staticClass(expr)
+      }
+      def typeOfTerm: Option[TypeSymbol] = replInfo(symbolOfLine(expr)).typeSymbol match {
+        case sym: TypeSymbol => Some(sym)
+        case _ => None
+      }
+      (typeFromTypeString orElse typeFromNameTreatedAsTerm orElse typeFromFullName orElse typeOfTerm) foreach { sym => 
+        val (kind, tpe) = exitingTyper { 
+          val tpe = sym.tpeHK
+          (intp.global.inferKind(NoPrefix)(tpe, sym.owner), tpe)
+        }
+        echoKind(tpe, kind, verbose)
+      }
+    }
+
+    def echoKind(tpe: Type, kind: Kind, verbose: Boolean) {
+      def typeString(tpe: Type): String = {
+        tpe match {
+          case TypeRef(_, sym, _) => typeString(sym.typeSignature)
+          case RefinedType(_, _)  => tpe.toString
+          case _                  => tpe.typeSymbol.fullName
+        }
+      }
+      printAfterTyper(typeString(tpe) + "'s kind is " + kind.scalaNotation)
+      if (verbose) {
+        echo(kind.starNotation)
+        echo(kind.description)
+      }
+    }
+
     /** TODO -
      *  -n normalize
      *  -l label with case class parameter names