This fixes the build. The deprecated constructor This was removed. It is no longer exported from dependent-sum. I've replaced all occurrences with Some (which exists since dependent-sum 0.5). The current lower bound for dependent-sum is 0.6.1. Additionally, I've dropped support for base < 4.9 because it simplifies maintenance and the dependent-sum bound requires base at least 4.9 anyway.
This fixes the build. The deprecated constructor This was removed. It is no longer exported from dependent-sum. I've replaced all occurrences with Some (which exists since dependent-sum 0.5). The current lower bound for dependent-sum is 0.6.1. Additionally, I've dropped support for base < 4.9 because it simplifies maintenance and the dependent-sum bound requires base at least 4.9 anyway.