Bug 9159 Classpath wizard should not complain when adding missing source folder
Build 20020125 - Define a project A with source folder 'src1'. - Go to the .classpath file and edit it to insert one extra line: <classpathentry kind="src" path="src2"/> below the line referring to first source folder: <classpathentry kind="src" path="src1"/>. - Now, try to add this missing source folder 'src2', it isn't allowed by the wizard, one has to add a basic folder instead. Note: It is not such an uncommon scenario, the classpath modification could simply occur by catching up with a shared classpath having one more source folder on it, and which is locally missing.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/BuildPathsBlock.java
CPListElement elem= new CPListElement(entryKind, path, res, curr.getSourceAttachmentPath(), curr.getSourceAttachmentRootPath(), isExported);
				if (projectExists) {
					elem.setIsMissing(isMissing);
				}
				newClassPath.add(elem);
			}
		}
		List exportedEntries = new ArrayList();
		for (int i= 0; i < newClassPath.size(); i++) {
			CPListElement curr= (CPListElement) newClassPath.get(i);
			if (curr.isExported() || curr.getEntryKind() == IClasspathEntry.CPE_SOURCE) {
				exportedEntries.add(curr);
			}
		}
		
		
		fBuildPathDialogField.setText(outputLocation.makeRelative().toString());
		fClassPathList.setElements(newClassPath);
		fClassPathList.setCheckedElements(exportedEntries);
		if (fSourceContainerPage != null) {
			fSourceContainerPage.init(fCurrJProject);
			fProjectsPage.init(fCurrJProject);
			fLibrariesPage.init(fCurrJProject);
		}
		
		doStatusLineUpdate();
	}