One of the tactics I end up using in Verilog, for better or worse, is to define enums with a'0 value (repeat 0s for the size of the variable), and '1 value (repeat 1s for the size of the value)
'0 stays as "null"-like (e.g INVALID), and '1 (which would be 0xFF in an 8 bit byte for instance) becomes "something, but I'm not sure what" (e.g. UNKNOWN).
Definitely has the same issues as referenced when needing to grow the variable, and the times where it's useful aren't super common, but I do feel like the general concept of an unknown-but-not-invalid value can help with tracking down errors in processing chains
Definitely do run into the need to "beware" though with enums for sure.
'0 stays as "null"-like (e.g INVALID), and '1 (which would be 0xFF in an 8 bit byte for instance) becomes "something, but I'm not sure what" (e.g. UNKNOWN).
Definitely has the same issues as referenced when needing to grow the variable, and the times where it's useful aren't super common, but I do feel like the general concept of an unknown-but-not-invalid value can help with tracking down errors in processing chains Definitely do run into the need to "beware" though with enums for sure.