Bug Report or Feature Request (mark with an x)

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

Command (mark with an x)

- [ ] new
- [ ] build
- [ ] serve
- [ ] test
- [ ] e2e
- [ X ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Versions

Angular CLI 6.1.1
Windows 10
Node 10.7.0
Yarn 1.9.2

Repro steps

Upgrade to the latest version of Angular 6.1.1 (Works okay on 6.1.0)
run ng g module modules/test2 --flat
or just ng g module modules/test2
or just ng g module test2
or just ng g m test2

Interestingly, it works when generating modules with routing flag, but haven't had any success with any other flags

ng g module modules/test2 --flat -routing or ng g module test2 --routing works.

The log given by the failure

I am getting a simple message without any other details attached:

Tree type is not supported.

Not enough information to help me troubleshoot where the problem is. I tried this on two of my projects.

Desired functionality

Should generate a new module in the specified location.

UPDATE

I also deleted the entire node_modules folder and re installed the packages without success. Downgrading back to 6.1.0 works as expected.