/**
 * Defines events that the model builder fires during construction of the effective model. When a listener encounters
 * errors while processing the event, it can report these problems via {@link ModelBuildingEvent#getProblems()}.
 * Note: To cope with future extensions to this interface, it is strongly recommended to extend
 * {@link AbstractModelBuildingListener} rather than to directly implement this interface.
 *

                }

                @Nonnull
                @Override
                public Collection<BuilderProblem> getProblems() {
                    return new MappedCollection<>(res.getProblems(), this::toProblem);
                }

                private BuilderProblem toProblem(ModelProblem problem) {
                    return new BuilderProblem() {

                getProblems(problem.getSeverity()).add(problem);
                return true;
            }
            return false;
        }

        @Override
        public Stream<P> problems(BuilderProblem.Severity severity) {
            requireNonNull(severity, "severity");
            return getProblems(severity).stream();
        }

            }
        }

        if (hasErrors(problems.getProblems())) {
            throw new SettingsBuildingException(problems.getProblems());
        }

        return new DefaultSettingsBuildingResult(userSettings, problems.getProblems());
    }

    private boolean hasErrors(List<SettingsProblem> problems) {
        if (problems != null) {

     */
    PersistedToolchains getEffectiveToolchains();

    /**
     * Return a list of problems, if any.
     *
     * @return a list of problems, never {@code null}.
     */
    List<Problem> getProblems();

    public Model getModel() {
        return model;
    }

    @Override
    public ModelBuildingRequest getRequest() {
        return request;
    }

    @Override
    public ModelProblemCollector getProblems() {
        return problems;
    }

    private String source;

    DefaultProblemCollector(List<Problem> problems) {
        this.problems = (problems != null) ? problems : new ArrayList<>();
    }

    @Override
    public List<Problem> getProblems() {
        return problems;
    }

    @Override
    public void setSource(String source) {
        this.source = source;
    }

    @Override

     *
     * @return The container used to collect problems that were encountered, never {@code null}.
     */
    ModelProblemCollector getProblems();

     *
     * @param source a source
     */
    void setSource(String source);

    /**
     *
     * @return the collected Problems, never {@code null}
     */
    List<Problem> getProblems();

        }
    }

    /**
     * Gets the problems that caused this exception.
     *
     * @return The problems that caused this exception, never {@code null}.
     */
    public List<Problem> getProblems() {
        return problems;
    }

    private static String toMessage(List<Problem> problems) {
        StringWriter buffer = new StringWriter(1024);

        PrintWriter writer = new PrintWriter(buffer);