$ nix-build shell.nix -A dwnTool --show-trace
error: while evaluating the attribute 'buildCommand' of the derivation 'dwn' at /nix/store/9yjrxr1b9c31xir2hm8xbp1mpbr2irhj-nixos-18.09.1420.5d4a1a3897e/nixos/pkgs/stdenv/generic/make-derivation.nix:177:11:
nix-repl has been removed because it's not maintained anymore, use `nix repl` instead. Also see https://github.com/NixOS/nixpkgs/pull/44903
Removing this dependency (and the dwn-nix-repl symlink altogether) appears to resolve the immediate issue.
Removing this dependency (and the
dwn-nix-repl
symlink altogether) appears to resolve the immediate issue.