Fix extracting top level xml elements (#262)

xml-stdlib/shared/src/main/scala/rapture/xml-stdlib/ast.scala

@@ -25,6 +25,7 @@ private[stdlib] object StdlibAst extends XmlBufferAst {
 
   override def dereferenceObject(obj: Any, element: String): Any = obj match {
     case n: Node if n.child.exists(_.label == element) => n \ element
+    case ns: NodeSeq if ns.exists(_.label == element) => ns.filter(_.label == element)
     case ns: NodeSeq if ns.exists(_.child.exists(_.label == element)) => ns \ element
     case _ => throw MissingValueException()
   }

xml-test/shared/src/test/scala/rapture/xml-test/tests.scala

@@ -183,6 +183,11 @@ abstract class XmlTests(ast: XmlAst, parser: Parser[String, XmlAst]) extends Tes
     Xml(1648).toString
   } returns "xml\"\"\"1648\"\"\""
 
+  val `Extract top level xml elements` = test {
+    val fooXML = Xml(Foo("Joe", 10))
+    fooXML.alpha.as[String]
+  } returns "Joe"
+
   /*val `Serialize array` = test {
     Json(List(1, 2, 3)).toString
   } returns "123"

xml/shared/src/main/scala/rapture/xml/ast.scala

@@ -21,15 +21,15 @@ import scala.util._
 
 trait XmlAst {
 
-  /** Dereferences the named element within the JSON object. */
+  /** Dereferences the named element within the XML object. */
   def dereferenceObject(obj: Any, element: String): Any =
     getObject(obj)(element)
 
-  /** Returns at `Iterator[String]` over the names of the elements in the JSON object. */
+  /** Returns at `Iterator[String]` over the names of the elements in the XML object. */
   def getKeys(obj: Any): Iterator[String] =
     getObject(obj).keys.iterator
 
-  /** Gets the indexed element from the parsed JSON array. */
+  /** Gets the indexed element from the parsed XML array. */
   def dereferenceArray(array: Any, element: Int): Any =
     getArray(array)(element)
 
@@ -41,7 +41,7 @@ trait XmlAst {
 
   def isNull(any: Any): Boolean
 
-  /** Extracts a JSON object as a `Map[String, Any]` from the parsed JSON. */
+  /** Extracts a XML object as a `Map[String, Any]` from the parsed XML. */
   def getObject(obj: Any): Map[String, Any]
 
   def getChildren(obj: Any): Seq[Any] = {
@@ -51,7 +51,7 @@ trait XmlAst {
 
   def fromObject(obj: Map[String, Any]): Any
 
-  /** Extracts a JSON array as a `Seq[Any]` from the parsed JSON. */
+  /** Extracts a XML array as a `Seq[Any]` from the parsed XML. */
   def getArray(array: Any): Seq[Any]
 
   def fromArray(array: Seq[Any]): Any