*            {@link ModelProblem.Severity#ERROR}.
     * @param source The source of the problem, may be {@code null}.
     * @param lineNumber The one-based index of the line containing the error or {@code -1} if unknown.
     * @param columnNumber The one-based index of the column containing the error or {@code -1} if unknown.
     * @param exception The exception that caused this problem, may be {@code null}.
     */

     * @param source A hint about the source of the problem like a file path, may be {@code null}.
     * @param lineNumber The one-based index of the line containing the problem or {@code -1} if unknown.
     * @param columnNumber The one-based index of the column containing the problem or {@code -1} if unknown.
     * @param exception The exception that caused this problem, may be {@code null}.
     */
    DefaultProblem(

     * @param message The detail message of the problem, may be {@code null}.
     * @param line The one-based index of the line containing the problem or {@code -1} if unknown.
     * @param column The one-based index of the column containing the problem or {@code -1} if unknown.
     * @param cause The cause of the problem, may be {@code null}.
     */

         * processes one artifact at a time and hence cannot associate the artifacts from the same project to use the
         * same version index. Allowing the caller to pass in metadata from a previous deployment allows to re-establish
         * the association between the artifacts of the same project.
         */

    // ------------------------------------------------------------------------
    public void addChild(int index, MetadataTreeNode kid) {
        if (kid == null) {
            return;
        }

        if (children == null) {
            children = new MetadataTreeNode[nChildren];
        }

        children[index % nChildren] = kid;
    }

    // ------------------------------------------------------------------

                : Set.of();
        String base = "default-" + goal;
        String id = base;
        for (int index = 1; existingIds.contains(id); index++) {
            id = base + '-' + index;
        }
        return id;
    }

    private record DefaultPackaging(String id, Type type, Map<String, PluginContainer> plugins) implements Packaging {}

            sessionForThisModule.setCurrentProject(null);
        }
    }

    public int size() {
        return items.size();
    }

    public ProjectSegment get(int index) {
        return items.get(index);
    }

    public Set<String> getReactorProjectKeys() {
        Set<String> projectKeys = new HashSet<>(items.size() * 2);
        for (ProjectSegment projectBuild : items) {

     * @param source A hint about the source of the problem like a file path, may be {@code null}.
     * @param lineNumber The one-based index of the line containing the problem or {@code -1} if unknown.
     * @param columnNumber The one-based index of the column containing the problem or {@code -1} if unknown.
     * @param exception The exception that caused this problem, may be {@code null}.
     */

         * processes one artifact at a time and hence cannot associate the artifacts from the same project to use the
         * same version index. Allowing the caller to pass in metadata from a previous deployment allows to re-establish
         * the association between the artifacts of the same project.
         */

     *
     * @throws IllegalStateException when underlying type is not a parameterized one.
     */
    public <U> Key<U> getTypeParameter(int index) {
        if (type instanceof ParameterizedType) {
            return new KeyImpl<>(((ParameterizedType) type).getActualTypeArguments()[index], null);
        }
        throw new IllegalStateException("Expected type from key " + getDisplayString() + " to be parameterized");
    }