Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

Area

- [ ] devkit
- [x] schematics

Versions

node --version
v6.9.1

npm --version
5.6.0

package.json
"@angular-devkit/core": "^0.4.2",
"@angular-devkit/schematics": "^0.4.2",
"@schematics/angular": "^0.4.2",

macOS - High Sierra

Repro steps

const dir = tree.getDir('folder');
const folders = dir.subdirs; // <-folders contain the names of the files

Desired functionality

My expectation would be for subdir to return an array of subdirectories.