Bug 28510 java build path inconsistency [build path]
20021216 select rt.jar in the package explorer open properties it allows you to set the javadoc location but for source attachment you are sent somewhere else it's inconsistent - on the java build path they both look sort of the same (they sit under the same node in the tree)
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/CPListElement.java
break;
			case IClasspathEntry.CPE_LIBRARY:
			case IClasspathEntry.CPE_VARIABLE:
				createAttributeElement(SOURCEATTACHMENT, null);
				createAttributeElement(JAVADOC, null);
				break;
			case IClasspathEntry.CPE_PROJECT:
			case IClasspathEntry.CPE_CONTAINER:
				break;
			default:
		}
	}
	
	public IClasspathEntry getClasspathEntry() {
		if (fCachedEntry == null) {
			fCachedEntry= newClasspathEntry();
		}
		return fCachedEntry;
	}
	
	private IClasspathEntry newClasspathEntry() {
		switch (fEntryKind) {
			case IClasspathEntry.CPE_SOURCE:
				IPath outputLocation= (IPath) getAttribute(OUTPUT);
				IPath[] exclusionPattern= (IPath[]) getAttribute(EXCLUSION);
				return JavaCore.newSourceEntry(fPath, exclusionPattern, outputLocation);
			case IClasspathEntry.CPE_LIBRARY:
				IPath attach= (IPath) getAttribute(SOURCEATTACHMENT);
				return JavaCore.newLibraryEntry(fPath, attach, null, isExported());
			case IClasspathEntry.CPE_PROJECT: