To reproduce and get a stack overflow fairly quickly run:

nix -L build .#crate2nix-stack-overflow-repro --no-link --show-trace

We can however do better. You can use a patched nix version to get a trace from before the overflow happens:

nix -L run .#nix-stack-overflow  -- -L build .#crate2nix-stack-overflow-repro --no-link --show-trace

This latter will take a while. I recommend suffixing something like 2>&1 | tee /tmp/log as the output will be quite large.