A few of the plug-ins within my feature define interfaces and abstract
classes that should be visible to plug-in developers after they have
installed the feature and added my plug-ins as dependencies. However, the
classes do not appear to be available unless, after installing the
feature, I go to the plug-ins view and import the plug-in as a source or
binary project. For other plug-ins, such as org.eclipse.ui, adding the
plug-in as a dependency in my plug-in project is all I need to do to be
able to use the packages/classes that org.eclipse.ui exports. What am I
doing wrong? (For now, all packages in all of my plug-ins are in the
"Export Packages" list and "visible to downstream plug-ins" is selected).