It seems that I was not in a great shape yesterday. There are some errors in my message.
Indeed, a set of _range[ '0'..'9']_ will occupy 58 bits rounded to 64, not 9 bits rounded to 16. I will have to declare _Digit_ as a _range[0..9]_ to use only 10 bits (not 9!) rounded to 16 and, in this case, the warning is no longer emitted as _Digit_ includes the null value. For my problem I can (and will) use a _range[0..9]_. In some cases, it may not be the right solution, so my question is still valid, I think, and the solution proposed by _mratsim_ is the way to hide the warning.
