The Ant code completion when editing a build.xml file is currently outdated (based on Ant 1.5). This functionality is driven by the ant-complete.xml file found in the XML Plugin (a sort of DTD for Ant). I created an Ant task that when run will generate an updated ant-complete.xml based on the version of Ant used when running the task (it uses the Introspection Helper to see all available task/types and their attributes/sub-elements). I created a patch for the build.xml of the XML Plugin so that when built, it will also update the ant-complete.xml file as part of the build. This will keep this file from getting out of date in future releases of the XML Plugin (assuming that new versions of Ant are used when building for a release). Also, this is useful for those who wish to build the plugin themselves as it will allow them to use Ant code copletion with their specific types and tasks which may be added to their local Ant installations.

I recently created a bug report which has these changes attached - http://sourceforge.net/tracker/index.php?func=detail&aid=1432414&group_id=588&atid=565475