Unexplained compile error using mixins in reach version f79282c4

[temptemp3]

Not sure what to make of this reach compile error.

Command: ./reach compile

Output:

REACH_VERSION: f79282c4
reachc: error[RE0094]: unused variable: d at reach standard library:606:19:id

  reach standard library:606:19:id

  

For further explanation of this error, see: https://docs.reach.sh/rsh/errors/#RE0094

The reach program I am trying to compile is here:
https://github.com/temptemp3/arc-72/blob/discussions/1570/index.rsh