1. Create a new Drools project:

File -> New -> Other -> Drools Project
Choose Name, click Next
Check all options
Choose Drools Runtime, click Finish

2. Open sample.drl file

3. Invoke Code Assist bellow line with import statement. It works. Context menu with available statements is displayed

4. Invoke Code Assist at the beginning of line with m : Message( status ... . No context menu is displayed

It's was working in JBDS 4.0.0.GA version.