Fix #253 (#420)

Provides initial implementation for java.lang.Class::getComponentType.

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

@@ -1,7 +1,7 @@
 package java.lang
 
-import scala.scalanative.native.Ptr
-import scala.scalanative.runtime.Type
+import scalanative.native.Ptr
+import scalanative.runtime.{Array => _, _}
 
 final class _Class[A](val ty: Ptr[Type]) {
   def getName(): String = (!ty).name
@@ -15,10 +15,21 @@ final class _Class[A](val ty: Ptr[Type]) {
       false
   }
 
+  def getComponentType(): _Class[_] = {
+    if (ty == typeof[BooleanArray]) classOf[scala.Boolean]
+    else if (ty == typeof[CharArray]) classOf[scala.Char]
+    else if (ty == typeof[ByteArray]) classOf[scala.Byte]
+    else if (ty == typeof[ShortArray]) classOf[scala.Short]
+    else if (ty == typeof[IntArray]) classOf[scala.Int]
+    else if (ty == typeof[LongArray]) classOf[scala.Long]
+    else if (ty == typeof[FloatArray]) classOf[scala.Float]
+    else if (ty == typeof[DoubleArray]) classOf[scala.Double]
+    else classOf[java.lang.Object]
+  }
+
   // TODO:
   def getInterfaces(): Array[_Class[_]] = ???
   def getSuperclass(): _Class[_]        = ???
-  def getComponentType(): _Class[_]     = ???
   def isArray(): scala.Boolean          = ???
 }
 

unit-tests/src/main/scala/java/lang/ClassSuite.scala

@@ -0,0 +1,17 @@
+package java.lang
+
+object ClassSuite extends tests.Suite {
+  test("getComponentType") {
+    assert(Array(false).getClass.getComponentType == classOf[scala.Boolean])
+    assert(Array('0').getClass.getComponentType == classOf[scala.Char])
+    assert(Array(0.toByte).getClass.getComponentType == classOf[scala.Byte])
+    assert(Array(0.toShort).getClass.getComponentType == classOf[scala.Short])
+    assert(Array(0).getClass.getComponentType == classOf[scala.Int])
+    assert(Array(0L).getClass.getComponentType == classOf[scala.Long])
+    assert(Array(0F).getClass.getComponentType == classOf[scala.Float])
+    assert(Array(0D).getClass.getComponentType == classOf[scala.Double])
+    assert(
+      Array(new java.lang.Object).getClass.getComponentType == classOf[
+        java.lang.Object])
+  }
+}

unit-tests/src/main/scala/scala/scalanative/issues/_253Suite.scala

@@ -0,0 +1,13 @@
+package scala.scalanative.issues
+
+object _253Suite extends tests.Suite {
+  test("#253") {
+    class Cell(val value: Int)
+
+    val arr     = Array(new Cell(1), new Cell(2))
+    val reverse = arr.reverse
+
+    assert(reverse(0).value == 2)
+    assert(reverse(1).value == 1)
+  }
+}