Compilation issues with tracing - attribute 'feature' missing

[evanjs]

I remember seeing something like this before with Carnix, though I'm not sure this is the same thing.

Generated a Cargo.nix and tried to build, but it fails with attribute 'feature' missing, which resolves to the spin crate dependency for tracing.

    "tracing 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)"
      = rec {
        crateName = "tracing";
        version = "0.1.9";
        edition = "2018";
        sha256 = "003dkgx7agd5g5hdmwayi927hzzr8gk0ghh83n4xg83k0x0wcv61";
        authors = [
          "Tokio Contributors <team@tokio.rs>"
        ];
        dependencies = {
          "cfg-if" = "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)";
          "log" = {
            packageId = "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)";
            optional = true;
          };
          "spin" = {
            packageId = "spin 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)";
            target = (!(target."feature" == "std"));
          };
          "tracing-attributes" = "tracing-attributes 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)";
          "tracing-core" = {
            packageId = "tracing-core 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)";
            usesDefaultFeatures = false;
          };
        };
        features = {
          "default" = [ "std" ];
          "log-always" = [ "log" ];
          "std" = [ "tracing-core/std" ];
        };
        resolvedDefaultFeatures = [ "default" "log" "std" ];
      };

This is the line in particular that it reports:

target = (!(target."feature" == "std"));

---

nix-info -m

• system: "x86_64-linux"
• host os: Linux 5.3.6, NixOS, 19.09.840.8bf142e001b (Loris)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3
• channels(root): "nixos-19.09.840.8bf142e001b, nixos-stable-19.09.789.7952807791d, nixos-unstable-20.03pre196586.b943338ea58, nixos-unstable-small-20.03pre196834.33366cce147, nixpkgs-unstable-20.03pre196811.7818f30cc4b"
• channels(evanjs): ""
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

crate2nix version: crate2nix 0.6.0-alpha.0