Bug 82231 [build path] Hard to find type restriction compiler problem preferences
I20050104-1600 There compiler preference page contains a Warning/Error node with many sub-entries . I tried to find where I could change the 'warning' for the access of internal types to 'error'. No luck until I realized that the Build node also contains Warning/Error settings.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/BuildPathsBlock.java
project.create(desc, monitor);
				monitor= null;
			}
			if (!project.isOpen()) {
				project.open(monitor);
				monitor= null;
			}
		} finally {
			if (monitor != null) {
				monitor.done();
			}
		}
	}
	public static void addJavaNature(IProject project, IProgressMonitor monitor) throws CoreException {
		if (monitor != null && monitor.isCanceled()) {
			throw new OperationCanceledException();
		}
		if (!project.hasNature(JavaCore.NATURE_ID)) {
			IProjectDescription description = project.getDescription();
			String[] prevNatures= description.getNatureIds();
			String[] newNatures= new String[prevNatures.length + 1];
			System.arraycopy(prevNatures, 0, newNatures, 0, prevNatures.length);
			newNatures[prevNatures.length]= JavaCore.NATURE_ID;
			description.setNatureIds(newNatures);
			project.setDescription(description, monitor);
		} else {
			monitor.worked(1);
		}
	}