error: unhandled error reached main: error.A
error return trace (most recent call last):
  fa at 247-failable-or-chain-propagate.sx:14:17
  main at 247-failable-or-chain-propagate.sx:19:10
  fa at 247-failable-or-chain-propagate.sx:14:17
  main at 247-failable-or-chain-propagate.sx:19:10
  fa at 247-failable-or-chain-propagate.sx:14:17
  main at 247-failable-or-chain-propagate.sx:19:10
