return nil
		}

		if s.walkMu != nil {
			s.walkMu.Lock()
		}
		entries, err := s.ListDir(ctx, "", opts.Bucket, current, -1)
		if s.walkMu != nil {
			s.walkMu.Unlock()
		}
		if err != nil {
			// Folder could have gone away in-between
			if err != errVolumeNotFound && err != errFileNotFound {
				internalLogOnceIf(ctx, err, "metacache-walk-scan-dir")
			}

		if n.Elt != nil {
			Walk(v, n.Elt)
		}

	case *FuncLit:
		Walk(v, n.Type)
		Walk(v, n.Body)

	case *CompositeLit:
		if n.Type != nil {
			Walk(v, n.Type)
		}
		walkList(v, n.Elts)

	case *ParenExpr:
		Walk(v, n.X)

	case *SelectorExpr:
		Walk(v, n.X)
		Walk(v, n.Sel)

	case *IndexExpr:
		Walk(v, n.X)
		Walk(v, n.Index)

	case *IndexListExpr:
		Walk(v, n.X)

	call.Fun = walkExpr(call.Fun, &init)

	if len(init) > 0 {
		init.Append(n)
		return ir.NewBlockStmt(n.Pos(), init)
	}
	return n
}

// walkIf walks an OIF node.
func walkIf(n *ir.IfStmt) ir.Node {
	n.Cond = walkExpr(n.Cond, n.PtrInit())
	walkStmtList(n.Body)
	walkStmtList(n.Else)
	return n

			ir.CurFunc.SetHasDefer(true)
			ir.CurFunc.SetOpenCodedDeferDisallowed(true)
		}
	}

	walkCall1(n, init)
	return n
}

func walkCall1(n *ir.CallExpr, init *ir.Nodes) {
	if n.Walked() {
		return // already walked
	}
	n.SetWalked(true)

	if n.Op() == ir.OCALLMETH {
		base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
	}

	args := n.Args
	params := n.Fun.Type().Params()

    def "type walker should correctly visit empty type"() {
        given:
        def visitor = new TestStaticMetadataVisitor()

        when:
        TypeMetadataWalker.typeWalker(typeMetadataStore, TestNested.class).walk(TypeToken.of(MyEmptyTask), visitor)

        then:
        visitor.all == ["null::MyEmptyTask"]
    }

    def "instance walker should correctly visit instance with null values"() {

                    if (visitingNodes.containsEntry(successor, currentSegment)) {
                        if (!walkedShouldRunAfterEdges.isEmpty()) {
                            //remove the last walked should run after edge and restore state from before walking it
                            GraphEdge toBeRemoved = walkedShouldRunAfterEdges.pop();
                            // Should run after edges only exist between tasks, so this cast is safe

    @Rule
    SetSystemProperties setSystemPropertiesRule

    protected abstract List<T> getWalkers()

    def "basic directory walking works - walker: #walkerInstance.class.simpleName"() {
        given:
        def rootDir = tmpDir.createDir("root")
        def rootTextFile = rootDir.file("a.txt").createFile()

				} else {
					ast.Walk(r, kv.Key)
				}
				ast.Walk(r, kv.Value)
			} else {
				ast.Walk(r, e)
			}
		}

	case *ast.InterfaceType:
		r.openScope(n.Pos())
		defer r.closeScope()
		r.walkFieldList(n.Methods, ast.Fun)

	// Statements
	case *ast.LabeledStmt:
		r.declare(n, nil, r.labelScope, ast.Lbl, n.Label)
		ast.Walk(r, n.Stmt)

	case *ast.AssignStmt:

     */
    Stream<FileSystemLocationSnapshot> roots();

    /**
     * Walks the whole hierarchy represented by this snapshot.
     *
     * The walk is depth first.
     */
    SnapshotVisitResult accept(FileSystemSnapshotHierarchyVisitor visitor);

    /**
     * Walks the whole hierarchy represented by this snapshot.
     *
     * The walk is depth first.
     */

                generateFilesAndSubDirectories(subDir, fileCount, dirCount, maxDepth, currentDepth + 1, fileIdGenerator)
            }
        }
    }

    def "file walker sees a snapshot of file metadata even if files are deleted after walking has started"() {
        given:
        def rootDir = tmpDir.createDir("root")
        long minimumTimestamp = (System.currentTimeMillis() / 1000 * 1000) - 2000