Specifying common responses for HTTP ops?

[sfre-coop]

I'd like to do something like this:

alias PermanentError = BadRequestResponse | UnauthorizedResponse | ForbiddenResponse;
alias TransientError = Response<500> | Response<503>;
alias Errors = PermanentError | TransientError;

model Error {
    messageId: string,
    message: string,
    correlationId?: string,
}

@post
op anOperation(
    @header contentType: "application/json",
    @body operationContents: OperationContents
    ): (Receipt & AcceptedResponse) | (Errors & BadRequestResponse);

but it complains that it can't do the intersection with a non-model type.

Is there a way to do something like this?