Extract_fa does not extract half adder

[viyelesay]

extract_fa command extracts full adders but does not extract half adder. Yosys uses full adder instead of half addder and connects carry in input to zero. Please check the attached file for the issue.
adderissue.zip

[whitequark]

Yosys does not have a half adder cell, so the pass uses a $fa cell to represent half adders.

[viyelesay]

Thanks for your reply. It would be nice if it also supports $fa cell.