Can an enum type mix another enum type?

I have a enum type defined as:

enum type OpportunityStatus {
Identified
Assigned
Completed
}

I want another enum that has everything in OpportunityStatus, and Pending and Closed.

I have tried the following but it gives me provisioning error "missing '{' at 'mixes'".
enum type NewOpportunityStatus mixes OpportunityStatus {
Pending
Closed
}

Is extending/mixing enum possible?

In 7.9, you can

enum type HttpStatus {

OK = 200

BAD_REQUEST = 400

NOT_FOUND = 404

}

enum type ImageUploadHttpStatus mixes HttpStatus {

TOO_BLURRY = 460

}