if (hasErrors(problems)) {
            throw new ToolchainsBuilderException("Error building toolchains", problems);
        }

        return new DefaultToolchainsBuilderResult(effective, problems);
    }

    private boolean hasErrors(List<BuilderProblem> problems) {
        if (problems != null) {
            for (BuilderProblem problem : problems) {

import java.util.ArrayList;
import java.util.List;

/**
 * Collects problems that are encountered during settings building.
 *
 */
class DefaultProblemCollector implements ProblemCollector {

    private final List<Problem> problems;

    private String source;

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

    @Override

            }
        }

        if (hasErrors(problems)) {
            throw new SettingsBuilderException("Error building settings", problems);
        }

        return new DefaultSettingsBuilderResult(effective, problems);
    }

    private boolean hasErrors(List<BuilderProblem> problems) {
        if (problems != null) {
            for (BuilderProblem problem : problems) {

    }

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

    public DefaultModelBuilderResult setProblems(List<ModelProblem> problems) {
        if (problems != null) {
            this.problems = new ArrayList<>(problems);
        } else {
            this.problems.clear();
        }

        return this;
    }

    public String toString() {

            DefaultModelProblemCollector problems)
            throws ModelBuilderException {
        Model inputModel = readRawModel(request, problems);
        if (problems.hasFatalErrors()) {
            throw problems.newModelBuilderException();
        }

        inputModel = activateFileModel(inputModel, request, result, problems);

        problems.setRootModel(inputModel);

                for (ModelProblem problem : result.getProblems()) {
                    String loc = ModelProblemUtils.formatLocation(problem, result.getProjectId());
                    LOGGER.warn("{}{}", problem.getMessage(), ((loc != null && !loc.isEmpty()) ? " @ " + loc : ""));
                }

                problems = true;
            }
        }

        if (problems) {
            LOGGER.warn("");

        SimpleProblemCollector problems = new SimpleProblemCollector();
        validator.validate(settings, problems);
        assertEquals(4, problems.messages.size());
        assertContains(problems.messages.get(0), "'mirrors.mirror.id' must not be 'local'");
        assertContains(problems.messages.get(1), "'mirrors.mirror.url' for local is missing");

                    return defaultModelBuilder.readRawModel(req, problems);
                } catch (ModelBuilderException e) {
                    // gathered with problem collector
                }
                return null;
            }
        };
    }

    private boolean addEdge(Path from, Path p, DefaultModelProblemCollector problems) {
        try {
            dag.addEdge(from.toString(), p.toString());

     * @param problems The problems that were encountered, may be {@code null}.
     */
    DefaultProjectBuildingResult(String projectId, File pomFile, List<ModelProblem> problems) {
        this.projectId = (projectId != null) ? projectId : "";
        this.pomFile = pomFile;
        this.project = null;
        this.problems = problems != null ? problems : Collections.emptyList();

        List<? extends ValueSource> valueSources = createValueSources(model, projectDir, request, problems);
        List<? extends InterpolationPostProcessor> postProcessors = createPostProcessors(model, projectDir, request);

        InnerInterpolator innerInterpolator = createInterpolator(valueSources, postProcessors, request, problems);