added example of compiler issue; unable to create 'size' and 'empty' properties on Collection<T> and java.util.Map<T> it seems? wonder if its a qualified name issue - qualified names don't seem to be allowed on extension properties - will raise an issue...

testlib/test/MapTest.kt

@@ -32,4 +32,12 @@ class MapTest() : TestSupport() {
 
     assertEquals(1, data.size())
   }
+
+  /** TODO can't seem to define size/empty properties for Map
+  fun testSizeAndEmpty() {
+    assert{ data.empty }
+
+    assertEquals(data.size, 0)
+  }
+  */
 }