firFunctionDeclarations.add(function)
            super.visitFunction(function)
        }

        override fun visitLoop(loop: FirLoop) {
            firLoopStatements.add(loop)
            super.visitLoop(loop)
        }

        override fun visitReturnExpression(returnExpression: FirReturnExpression) {

    /**
     * Visit the root of each complete hierarchy contained in the set.
     */
    public abstract void visitRoots(RootVisitor visitor);

    public interface RootVisitor {
        void visitRoot(String absolutePath);
    }

    /**
     * The empty set.
     */
    public static FileHierarchySet empty() {
        return EMPTY;
    }

    }

    @Override
    public void walk(T root, V visitor) {
        Class<?> nodeType = resolveType(root);
        TypeMetadata typeMetadata = typeMetadataStore.getTypeMetadata(nodeType);
        visitor.visitRoot(typeMetadata, root);
        Map<T, String> nestedNodesOnPath = nestedNodeToQualifiedNameMapFactory.get();
        nestedNodesOnPath.put(root, "<root>");
        walkChildren(root, typeMetadata, null, visitor, nestedNodesOnPath);

            this.newRoot = newRoot;
            this.invalidator = invalidator;
        }

        @Override
        public void visitRoot(String absolutePath) {
            newRoot = invalidator.invalidate(absolutePath, newRoot);
        }

        public SnapshotHierarchy getNewRoot() {
            return newRoot;
        }
    }

        private final List<CollectedNode> nested = []

        protected void addNode(CollectedNode node) {
            all.add(node)
        }

        @Override
        void visitRoot(TypeMetadata typeMetadata, T value) {
            def node = new CollectedNode(typeMetadata, null, String.valueOf(value))
            addNode(node)
            roots.add(node)
        }

        @Override