From the D Blog: The Evolution of the accessors Library

[Mario Kröplin via Digitalmars-d-announce]

On Wednesday, 6 September 2017 at 18:11:28 UTC, Joakim wrote:
> - There's no resolution to the Flag type issue: you should say 
> whether you filed a bug, as you did with the issue in the 
> private classes section, or if you were able to work around it.

We asked in the forum whether this is a bug:
https://forum.dlang.org/thread/igsxmowtguwvngnqullx@forum.dlang.org

The answer was ... inconclusive.

So, we worked around the problem:
https://github.com/funkwerk/accessors/blob/master/src/accessors.d#L223