Records with 0 fields generate invalid verilog

[nakengelhardt]

When defining a record with no fields, as in
_layout = []
and then using raw_bits(), it will generate invalid verilog, e.g.:
assign {} = x;

[jordens]

Should it silently drop logic related to the Record or should it error?

[nakengelhardt]

Silently drop would be the preferred solution in my case, since I use it to build generic logic where the contents of the Record change with the application (and some simply don't need extra data).

[jordens]

Hmm. That might lead to tough questions if the Record (or its raw_bits()) is used in expressions. What's the boolean of a zero length signal? Can it be signed? How does it extend? If you drop a zero length signal from an expression and nothing is left, do you drop entire assignment? It might need to be an error.

[whitequark]

Triage: fixed in nMigen, where 0-bit signals are explicitly valid.