Merge pull request scala-js#3217 from sjrd/scala-agnostic-j-l-class

Make java.lang.Class agnostic of Scala

Author: gzm0

javalanglib/src/main/scala/java/lang/Class.scala

@@ -11,15 +11,17 @@ private trait ScalaJSClassData[A] extends js.Object {
   val isRawJSType: scala.Boolean = js.native
 
   def isInstance(obj: Object): scala.Boolean = js.native
-  def getFakeInstance(): Object = js.native
+  def isAssignableFrom(that: ScalaJSClassData[_]): scala.Boolean = js.native
 
   def getSuperclass(): Class[_ >: A] = js.native
   def getComponentType(): Class[_] = js.native
 
   def newArrayOfThisClass(dimensions: js.Array[Int]): AnyRef = js.native
 }
 
-final class Class[A] private (data: ScalaJSClassData[A]) extends Object {
+final class Class[A] private (data0: Object) extends Object {
+  private val data: ScalaJSClassData[A] =
+    data0.asInstanceOf[ScalaJSClassData[A]]
 
   override def toString(): String = {
     (if (isInterface()) "interface " else
@@ -30,30 +32,7 @@ final class Class[A] private (data: ScalaJSClassData[A]) extends Object {
     data.isInstance(obj)
 
   def isAssignableFrom(that: Class[_]): scala.Boolean =
-    if (this.isPrimitive || that.isPrimitive) {
-      /* This differs from the JVM specification to mimic the behavior of
-       * runtime type tests of primitive numeric types.
-       */
-      (this eq that) || {
-        if (this eq classOf[scala.Short])
-          (that eq classOf[scala.Byte])
-        else if (this eq classOf[scala.Int])
-          (that eq classOf[scala.Byte]) || (that eq classOf[scala.Short])
-        else if (this eq classOf[scala.Float])
-          (that eq classOf[scala.Byte]) || (that eq classOf[scala.Short]) ||
-          (that eq classOf[scala.Int])
-        else if (this eq classOf[scala.Double])
-          (that eq classOf[scala.Byte]) || (that eq classOf[scala.Short]) ||
-          (that eq classOf[scala.Int])  || (that eq classOf[scala.Float])
-        else
-          false
-      }
-    } else {
-      this.isInstance(that.getFakeInstance())
-    }
-
-  private def getFakeInstance(): Object =
-    data.getFakeInstance()
+    this.data.isAssignableFrom(that.data)
 
   def isInterface(): scala.Boolean =
     data.isInterface