diff --git a/Cargo.nix b/Cargo.nix
new file mode 100644
index 0000000..facad84
--- /dev/null
+++ b/Cargo.nix
@@ -0,0 +1,2717 @@
+
+# This file was @generated by crate2nix 0.9.0-alpha.1 with the command:
+#   "generate"
+# See https://github.com/kolloch/crate2nix for more info.
+
+{ nixpkgs ? <nixpkgs>
+, pkgs ? import nixpkgs { config = {}; }
+, lib ? pkgs.lib
+, stdenv ? pkgs.stdenv
+, buildRustCrate ? pkgs.buildRustCrate
+  # This is used as the `crateOverrides` argument for `buildRustCrate`.
+, defaultCrateOverrides ? pkgs.defaultCrateOverrides
+  # The features to enable for the root_crate or the workspace_members.
+, rootFeatures ? [ "default" ]
+  # If true, throw errors instead of issueing deprecation warnings.
+, strictDeprecation ? false
+  # Used for conditional compilation based on CPU feature detection.
+, targetFeatures ? []
+  # Whether to perform release builds: longer compile times, faster binaries.
+, release ? true
+  # Additional crate2nix configuration if it exists.
+, crateConfig
+  ? if builtins.pathExists ./crate-config.nix
+    then pkgs.callPackage ./crate-config.nix {}
+    else {}
+}:
+
+rec {
+  #
+  # "public" attributes that we attempt to keep stable with new versions of crate2nix.
+  #
+
+  rootCrate = rec {
+    packageId = "colmena";
+
+    # Use this attribute to refer to the derivation building your root crate package.
+    # You can override the features with rootCrate.build.override { features = [ "default" "feature1" ... ]; }.
+    build = internal.buildRustCrateWithFeatures {
+      inherit packageId;
+    };
+
+    # Debug support which might change between releases.
+    # File a bug if you depend on any for non-debug work!
+    debug = internal.debugCrate { inherit packageId; };
+  };
+  # Refer your crate build derivation by name here.
+  # You can override the features with
+  # workspaceMembers."${crateName}".build.override { features = [ "default" "feature1" ... ]; }.
+  workspaceMembers = {
+    "colmena" = rec {
+      packageId = "colmena";
+      build = internal.buildRustCrateWithFeatures {
+        packageId = "colmena";
+      };
+
+      # Debug support which might change between releases.
+      # File a bug if you depend on any for non-debug work!
+      debug = internal.debugCrate { inherit packageId; };
+    };
+  };
+
+  # A derivation that joins the outputs of all workspace members together.
+  allWorkspaceMembers = pkgs.symlinkJoin {
+      name = "all-workspace-members";
+      paths =
+        let members = builtins.attrValues workspaceMembers;
+        in builtins.map (m: m.build) members;
+  };
+
+  #
+  # "internal" ("private") attributes that may change in every new version of crate2nix.
+  #
+
+  internal = rec {
+    # Build and dependency information for crates.
+    # Many of the fields are passed one-to-one to buildRustCrate.
+    #
+    # Noteworthy:
+    # * `dependencies`/`buildDependencies`: similar to the corresponding fields for buildRustCrate.
+    #   but with additional information which is used during dependency/feature resolution.
+    # * `resolvedDependencies`: the selected default features reported by cargo - only included for debugging.
+    # * `devDependencies` as of now not used by `buildRustCrate` but used to
+    #   inject test dependencies into the build
+
+    crates = {
+      "ansi_term" = rec {
+        crateName = "ansi_term";
+        version = "0.11.0";
+        edition = "2015";
+        sha256 = "16wpvrghvd0353584i1idnsgm0r3vchg8fyrm0x8ayv1rgvbljgf";
+        authors = [
+          "ogham@bsago.me"
+          "Ryan Scheel (Havvy) <ryan.havvy@gmail.com>"
+          "Josh Triplett <josh@joshtriplett.org>"
+        ];
+        dependencies = [
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: (target."os" == "windows");
+            features = [ "errhandlingapi" "consoleapi" "processenv" ];
+          }
+        ];
+        
+      };
+      "async-trait" = rec {
+        crateName = "async-trait";
+        version = "0.1.42";
+        edition = "2018";
+        sha256 = "0gd13pqgw5m6l4bqwjkickq13c4v0jxzxs5i4dwmldrlgvklafld";
+        procMacro = true;
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "full" "visit-mut" ];
+          }
+        ];
+        
+      };
+      "atty" = rec {
+        crateName = "atty";
+        version = "0.2.14";
+        edition = "2015";
+        sha256 = "1s7yslcs6a28c5vz7jwj63lkfgyx8mx99fdirlhi9lbhhzhrpcyr";
+        authors = [
+          "softprops <d.tangren@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "hermit-abi";
+            packageId = "hermit-abi";
+            target = { target, features }: (target."os" == "hermit");
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+            usesDefaultFeatures = false;
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "consoleapi" "processenv" "minwinbase" "minwindef" "winbase" ];
+          }
+        ];
+        
+      };
+      "autocfg" = rec {
+        crateName = "autocfg";
+        version = "1.0.1";
+        edition = "2015";
+        sha256 = "0jj6i9zn4gjl03kjvziqdji6rwx8ykz8zk2ngpc331z2g3fk3c6d";
+        authors = [
+          "Josh Stone <cuviper@gmail.com>"
+        ];
+        
+      };
+      "bitflags" = rec {
+        crateName = "bitflags";
+        version = "1.2.1";
+        edition = "2015";
+        sha256 = "14qnd5nq8p2almk79m4m8ydqhd413yaxsyjp5xd19g3mikzf47fg";
+        authors = [
+          "The Rust Project Developers"
+        ];
+        features = {
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "bytes" = rec {
+        crateName = "bytes";
+        version = "0.6.0";
+        edition = "2018";
+        sha256 = "05ivrcbgl4f7z2zzm9hbsi8cy66spi70xlm6fp16zsq4ylsvrp70";
+        authors = [
+          "Carl Lerche <me@carllerche.com>"
+          "Sean McArthur <sean@seanmonstar.com>"
+        ];
+        features = {
+          "default" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "default" "std" ];
+      };
+      "cfg-if 0.1.10" = rec {
+        crateName = "cfg-if";
+        version = "0.1.10";
+        edition = "2018";
+        sha256 = "08h80ihs74jcyp24cd75wwabygbbdgl05k6p5dmq8akbr78vv1a7";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        features = {
+          "rustc-dep-of-std" = [ "core" "compiler_builtins" ];
+        };
+      };
+      "cfg-if 1.0.0" = rec {
+        crateName = "cfg-if";
+        version = "1.0.0";
+        edition = "2018";
+        sha256 = "1za0vb97n4brpzpv8lsbnzmq5r8f2b0cpqqr0sy8h5bn751xxwds";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        features = {
+          "rustc-dep-of-std" = [ "core" "compiler_builtins" ];
+        };
+      };
+      "clap" = rec {
+        crateName = "clap";
+        version = "2.33.3";
+        edition = "2015";
+        sha256 = "00i065a58987k1sbzqmlz721rw521zcg08jmsh40gi3khp3qmr9p";
+        authors = [
+          "Kevin K. <kbknapp@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "ansi_term";
+            packageId = "ansi_term";
+            optional = true;
+            target = { target, features }: (!target."windows");
+          }
+          {
+            name = "atty";
+            packageId = "atty";
+            optional = true;
+          }
+          {
+            name = "bitflags";
+            packageId = "bitflags";
+          }
+          {
+            name = "strsim";
+            packageId = "strsim";
+            optional = true;
+          }
+          {
+            name = "textwrap";
+            packageId = "textwrap";
+          }
+          {
+            name = "unicode-width";
+            packageId = "unicode-width";
+          }
+          {
+            name = "vec_map";
+            packageId = "vec_map";
+            optional = true;
+          }
+        ];
+        features = {
+          "color" = [ "ansi_term" "atty" ];
+          "default" = [ "suggestions" "color" "vec_map" ];
+          "doc" = [ "yaml" ];
+          "lints" = [ "clippy" ];
+          "suggestions" = [ "strsim" ];
+          "wrap_help" = [ "term_size" "textwrap/term_size" ];
+          "yaml" = [ "yaml-rust" ];
+        };
+        resolvedDefaultFeatures = [ "ansi_term" "atty" "color" "default" "strsim" "suggestions" "vec_map" ];
+      };
+      "colmena" = rec {
+        crateName = "colmena";
+        version = "0.1.0";
+        edition = "2018";
+        crateBin = [
+          { name = "colmena"; path = "src/main.rs"; }
+        ];
+        src = lib.cleanSourceWith { filter = sourceFilter;  src = ./.; };
+        authors = [
+          "Zhaofeng Li <hello@zhaofeng.li>"
+        ];
+        dependencies = [
+          {
+            name = "async-trait";
+            packageId = "async-trait";
+          }
+          {
+            name = "clap";
+            packageId = "clap";
+          }
+          {
+            name = "console";
+            packageId = "console";
+          }
+          {
+            name = "futures";
+            packageId = "futures";
+          }
+          {
+            name = "glob";
+            packageId = "glob";
+          }
+          {
+            name = "indicatif";
+            packageId = "indicatif";
+          }
+          {
+            name = "log";
+            packageId = "log";
+          }
+          {
+            name = "serde";
+            packageId = "serde";
+            features = [ "derive" ];
+          }
+          {
+            name = "serde_json";
+            packageId = "serde_json";
+          }
+          {
+            name = "snafu";
+            packageId = "snafu";
+          }
+          {
+            name = "tempfile";
+            packageId = "tempfile";
+          }
+          {
+            name = "tokio";
+            packageId = "tokio";
+            features = [ "full" ];
+          }
+        ];
+        
+      };
+      "console" = rec {
+        crateName = "console";
+        version = "0.13.0";
+        edition = "2018";
+        sha256 = "022ai0jbbawngrx396qppwgzk4pk3v2fdwckzamvz6h154jsn2m5";
+        authors = [
+          "Armin Ronacher <armin.ronacher@active-4.com>"
+        ];
+        dependencies = [
+          {
+            name = "encode_unicode";
+            packageId = "encode_unicode";
+            target = { target, features }: target."windows";
+          }
+          {
+            name = "lazy_static";
+            packageId = "lazy_static";
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+          }
+          {
+            name = "regex";
+            packageId = "regex";
+            optional = true;
+            usesDefaultFeatures = false;
+            features = [ "std" ];
+          }
+          {
+            name = "terminal_size";
+            packageId = "terminal_size";
+          }
+          {
+            name = "unicode-width";
+            packageId = "unicode-width";
+            optional = true;
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "winbase" "winuser" "consoleapi" "processenv" "wincon" ];
+          }
+          {
+            name = "winapi-util";
+            packageId = "winapi-util";
+            optional = true;
+            target = { target, features }: target."windows";
+          }
+        ];
+        features = {
+          "ansi-parsing" = [ "regex" ];
+          "default" = [ "unicode-width" "ansi-parsing" "windows-console-colors" ];
+          "windows-console-colors" = [ "ansi-parsing" "winapi-util" ];
+        };
+        resolvedDefaultFeatures = [ "ansi-parsing" "default" "regex" "unicode-width" "winapi-util" "windows-console-colors" ];
+      };
+      "doc-comment" = rec {
+        crateName = "doc-comment";
+        version = "0.3.3";
+        edition = "2015";
+        sha256 = "043sprsf3wl926zmck1bm7gw0jq50mb76lkpk49vasfr6ax1p97y";
+        libName = "doc_comment";
+        authors = [
+          "Guillaume Gomez <guillaume1.gomez@gmail.com>"
+        ];
+        features = {
+        };
+      };
+      "encode_unicode" = rec {
+        crateName = "encode_unicode";
+        version = "0.3.6";
+        edition = "2015";
+        sha256 = "07w3vzrhxh9lpjgsg2y5bwzfar2aq35mdznvcp3zjl0ssj7d4mx3";
+        authors = [
+          "Torbjørn Birch Moltu <t.b.moltu@lyse.net>"
+        ];
+        features = {
+          "default" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "default" "std" ];
+      };
+      "futures" = rec {
+        crateName = "futures";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "1l434mh7p5na5c3c7lih575hszqc515r9idk62fm5rhz1820qfwv";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "futures-channel";
+            packageId = "futures-channel";
+            usesDefaultFeatures = false;
+            features = [ "sink" ];
+          }
+          {
+            name = "futures-core";
+            packageId = "futures-core";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-executor";
+            packageId = "futures-executor";
+            optional = true;
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-io";
+            packageId = "futures-io";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-sink";
+            packageId = "futures-sink";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-task";
+            packageId = "futures-task";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-util";
+            packageId = "futures-util";
+            usesDefaultFeatures = false;
+            features = [ "sink" ];
+          }
+        ];
+        features = {
+          "alloc" = [ "futures-core/alloc" "futures-task/alloc" "futures-sink/alloc" "futures-channel/alloc" "futures-util/alloc" ];
+          "async-await" = [ "futures-util/async-await" "futures-util/async-await-macro" ];
+          "bilock" = [ "futures-util/bilock" ];
+          "cfg-target-has-atomic" = [ "futures-core/cfg-target-has-atomic" "futures-task/cfg-target-has-atomic" "futures-channel/cfg-target-has-atomic" "futures-util/cfg-target-has-atomic" ];
+          "compat" = [ "std" "futures-util/compat" ];
+          "default" = [ "std" "async-await" "executor" ];
+          "executor" = [ "std" "futures-executor/std" ];
+          "io-compat" = [ "compat" "futures-util/io-compat" ];
+          "read-initializer" = [ "futures-io/read-initializer" "futures-util/read-initializer" ];
+          "std" = [ "alloc" "futures-core/std" "futures-task/std" "futures-io/std" "futures-sink/std" "futures-util/std" "futures-util/io" "futures-util/channel" ];
+          "thread-pool" = [ "executor" "futures-executor/thread-pool" ];
+          "unstable" = [ "futures-core/unstable" "futures-task/unstable" "futures-channel/unstable" "futures-io/unstable" "futures-util/unstable" ];
+          "write-all-vectored" = [ "futures-util/write-all-vectored" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "async-await" "default" "executor" "futures-executor" "std" ];
+      };
+      "futures-channel" = rec {
+        crateName = "futures-channel";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "0r7y228kkhwx9jj3ny5ppmw2gvw0capm6ig8dzppgqd4g9l0jwab";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "futures-core";
+            packageId = "futures-core";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-sink";
+            packageId = "futures-sink";
+            optional = true;
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+          "alloc" = [ "futures-core/alloc" ];
+          "cfg-target-has-atomic" = [ "futures-core/cfg-target-has-atomic" ];
+          "default" = [ "std" ];
+          "sink" = [ "futures-sink" ];
+          "std" = [ "alloc" "futures-core/std" ];
+          "unstable" = [ "futures-core/unstable" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "futures-sink" "sink" "std" ];
+      };
+      "futures-core" = rec {
+        crateName = "futures-core";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "0j0pixxv8dmqas1h5cgy92z4r9lpmnlis8ls22v17yrgnwqy2z44";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        features = {
+          "default" = [ "std" ];
+          "std" = [ "alloc" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "default" "std" ];
+      };
+      "futures-executor" = rec {
+        crateName = "futures-executor";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "0r8ayj6g08d1i0hj2v6g5zr3hzlkxpqlkpf1awq0105qd0mjpajc";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "futures-core";
+            packageId = "futures-core";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-task";
+            packageId = "futures-task";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-util";
+            packageId = "futures-util";
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+          "default" = [ "std" ];
+          "std" = [ "futures-core/std" "futures-task/std" "futures-util/std" ];
+          "thread-pool" = [ "std" "num_cpus" ];
+        };
+        resolvedDefaultFeatures = [ "std" ];
+      };
+      "futures-io" = rec {
+        crateName = "futures-io";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "1frh7d0n96lczy22al3bkgwpq0p1agbgax5kqh9vv8da33738631";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        features = {
+          "default" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "std" ];
+      };
+      "futures-macro" = rec {
+        crateName = "futures-macro";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "0mjmb46zapb59iilsbljpj7l0hq6w19df0f03p3br5qz5xlqlh3p";
+        procMacro = true;
+        authors = [
+          "Taylor Cramer <cramertj@google.com>"
+          "Taiki Endo <te316e89@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro-hack";
+            packageId = "proc-macro-hack";
+          }
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "full" ];
+          }
+        ];
+        
+      };
+      "futures-sink" = rec {
+        crateName = "futures-sink";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "0gfb1z97q861ki6lqsvpgfn3hnm9w3vkrf82dc00xrff95d1jy7q";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        features = {
+          "default" = [ "std" ];
+          "std" = [ "alloc" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "std" ];
+      };
+      "futures-task" = rec {
+        crateName = "futures-task";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "03ad39v8scy353src2f9dkkvcs24n736iavi8xn45cj8pyslwmbw";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "once_cell";
+            packageId = "once_cell";
+            optional = true;
+            usesDefaultFeatures = false;
+            features = [ "std" ];
+          }
+        ];
+        features = {
+          "default" = [ "std" ];
+          "std" = [ "alloc" "once_cell" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "once_cell" "std" ];
+      };
+      "futures-util" = rec {
+        crateName = "futures-util";
+        version = "0.3.8";
+        edition = "2018";
+        sha256 = "1lnbhpyrypn9giw6122af0pffxfijfz3zm7phrwzp75rlzscy16k";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "futures-channel";
+            packageId = "futures-channel";
+            optional = true;
+            usesDefaultFeatures = false;
+            features = [ "std" ];
+          }
+          {
+            name = "futures-core";
+            packageId = "futures-core";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-io";
+            packageId = "futures-io";
+            optional = true;
+            usesDefaultFeatures = false;
+            features = [ "std" ];
+          }
+          {
+            name = "futures-macro";
+            packageId = "futures-macro";
+            optional = true;
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-sink";
+            packageId = "futures-sink";
+            optional = true;
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "futures-task";
+            packageId = "futures-task";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "memchr";
+            packageId = "memchr";
+            optional = true;
+          }
+          {
+            name = "pin-project";
+            packageId = "pin-project";
+          }
+          {
+            name = "pin-utils";
+            packageId = "pin-utils";
+          }
+          {
+            name = "proc-macro-hack";
+            packageId = "proc-macro-hack";
+            optional = true;
+          }
+          {
+            name = "proc-macro-nested";
+            packageId = "proc-macro-nested";
+            optional = true;
+          }
+          {
+            name = "slab";
+            packageId = "slab";
+            optional = true;
+          }
+        ];
+        features = {
+          "alloc" = [ "futures-core/alloc" "futures-task/alloc" ];
+          "async-await-macro" = [ "async-await" "futures-macro" "proc-macro-hack" "proc-macro-nested" ];
+          "cfg-target-has-atomic" = [ "futures-core/cfg-target-has-atomic" "futures-task/cfg-target-has-atomic" ];
+          "channel" = [ "std" "futures-channel" ];
+          "compat" = [ "std" "futures_01" ];
+          "default" = [ "std" "async-await" "async-await-macro" ];
+          "io" = [ "std" "futures-io" "memchr" ];
+          "io-compat" = [ "io" "compat" "tokio-io" ];
+          "read-initializer" = [ "io" "futures-io/read-initializer" "futures-io/unstable" ];
+          "sink" = [ "futures-sink" ];
+          "std" = [ "alloc" "futures-core/std" "futures-task/std" "slab" ];
+          "unstable" = [ "futures-core/unstable" "futures-task/unstable" ];
+          "write-all-vectored" = [ "io" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "async-await" "async-await-macro" "channel" "futures-channel" "futures-io" "futures-macro" "futures-sink" "io" "memchr" "proc-macro-hack" "proc-macro-nested" "sink" "slab" "std" ];
+      };
+      "getrandom" = rec {
+        crateName = "getrandom";
+        version = "0.1.15";
+        edition = "2018";
+        sha256 = "1rj7psnlrnmsgyj6x2ag4c6367laq4g8kfd6pzamac99xk07nn7w";
+        authors = [
+          "The Rand Project Developers"
+        ];
+        dependencies = [
+          {
+            name = "cfg-if";
+            packageId = "cfg-if 0.1.10";
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+            usesDefaultFeatures = false;
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "wasi";
+            packageId = "wasi";
+            target = { target, features }: (target."os" == "wasi");
+          }
+        ];
+        features = {
+          "rustc-dep-of-std" = [ "compiler_builtins" "core" ];
+          "test-in-browser" = [ "wasm-bindgen" ];
+        };
+        resolvedDefaultFeatures = [ "std" ];
+      };
+      "glob" = rec {
+        crateName = "glob";
+        version = "0.3.0";
+        edition = "2015";
+        sha256 = "0x25wfr7vg3mzxc9x05dcphvd3nwlcmbnxrvwcvrrdwplcrrk4cv";
+        authors = [
+          "The Rust Project Developers"
+        ];
+        
+      };
+      "hermit-abi" = rec {
+        crateName = "hermit-abi";
+        version = "0.1.17";
+        edition = "2018";
+        sha256 = "1s1ss7xypnbpjglmj5k39svzsmni1rqp57a91qi5pyv0yxjmbjjs";
+        authors = [
+          "Stefan Lankes"
+        ];
+        dependencies = [
+          {
+            name = "libc";
+            packageId = "libc";
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+          "rustc-dep-of-std" = [ "core" "compiler_builtins/rustc-dep-of-std" "libc/rustc-dep-of-std" ];
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "indicatif" = rec {
+        crateName = "indicatif";
+        version = "0.15.0";
+        edition = "2018";
+        sha256 = "1r4n50mclyi4c7b9c9mlma1rhchjamw71r3z8vgqcmp24mhvbakv";
+        authors = [
+          "Armin Ronacher <armin.ronacher@active-4.com>"
+        ];
+        dependencies = [
+          {
+            name = "console";
+            packageId = "console";
+          }
+          {
+            name = "lazy_static";
+            packageId = "lazy_static";
+          }
+          {
+            name = "number_prefix";
+            packageId = "number_prefix";
+          }
+          {
+            name = "regex";
+            packageId = "regex";
+            usesDefaultFeatures = false;
+            features = [ "std" ];
+          }
+        ];
+        features = {
+          "improved_unicode" = [ "unicode-segmentation" "unicode-width" "console/unicode-width" ];
+          "with_rayon" = [ "rayon" ];
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "instant" = rec {
+        crateName = "instant";
+        version = "0.1.9";
+        edition = "2018";
+        sha256 = "1v659qqm55misvjijfbl1p7azjp4yynjbwldan8836ynpgp4w4k1";
+        authors = [
+          "sebcrozet <developer@crozet.re>"
+        ];
+        dependencies = [
+          {
+            name = "cfg-if";
+            packageId = "cfg-if 1.0.0";
+          }
+        ];
+        features = {
+          "now" = [ "time" ];
+          "wasm-bindgen" = [ "js-sys" "wasm-bindgen_rs" "web-sys" ];
+        };
+      };
+      "itoa" = rec {
+        crateName = "itoa";
+        version = "0.4.6";
+        edition = "2015";
+        sha256 = "1rnpb7rr8df76gnlk07b9086cn7fc0dxxy1ghh00q6nip7bklvyw";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        features = {
+          "default" = [ "std" ];
+        };
+      };
+      "lazy_static" = rec {
+        crateName = "lazy_static";
+        version = "1.4.0";
+        edition = "2015";
+        sha256 = "0in6ikhw8mgl33wjv6q6xfrb5b9jr16q8ygjy803fay4zcisvaz2";
+        authors = [
+          "Marvin Löbel <loebel.marvin@gmail.com>"
+        ];
+        features = {
+          "spin_no_std" = [ "spin" ];
+        };
+      };
+      "libc" = rec {
+        crateName = "libc";
+        version = "0.2.81";
+        edition = "2015";
+        sha256 = "1jsk82v5snd286ba92lir5snrxl18qm3kjkagz8c97hn0q9q50hl";
+        authors = [
+          "The Rust Project Developers"
+        ];
+        features = {
+          "default" = [ "std" ];
+          "rustc-dep-of-std" = [ "align" "rustc-std-workspace-core" ];
+          "use_std" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "align" "default" "std" ];
+      };
+      "lock_api" = rec {
+        crateName = "lock_api";
+        version = "0.4.2";
+        edition = "2018";
+        sha256 = "04hkhfq308agxg9wwmzh7ncfiyyyhn0d49n07abppzdj6p8zz5nx";
+        authors = [
+          "Amanieu d'Antras <amanieu@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "scopeguard";
+            packageId = "scopeguard";
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+        };
+      };
+      "log" = rec {
+        crateName = "log";
+        version = "0.4.11";
+        edition = "2015";
+        sha256 = "12xzqaflpiljn5cmxsbnbv9sjaj13ykhwsvll0gysbx4blbyvasg";
+        authors = [
+          "The Rust Project Developers"
+        ];
+        dependencies = [
+          {
+            name = "cfg-if";
+            packageId = "cfg-if 0.1.10";
+          }
+        ];
+        features = {
+          "kv_unstable_sval" = [ "kv_unstable" "sval/fmt" ];
+        };
+      };
+      "memchr" = rec {
+        crateName = "memchr";
+        version = "2.3.4";
+        edition = "2015";
+        sha256 = "098m9clfs495illlw00hv2gg67mhm7jflld3msyclvi5m9xc9q8f";
+        authors = [
+          "Andrew Gallant <jamslam@gmail.com>"
+          "bluss"
+        ];
+        features = {
+          "default" = [ "std" ];
+          "use_std" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "default" "std" ];
+      };
+      "mio" = rec {
+        crateName = "mio";
+        version = "0.7.6";
+        edition = "2018";
+        sha256 = "12qsvmsmpijnghgci5i0liskvwxrbg2dz6hc09kgvwaf0s3whfzk";
+        authors = [
+          "Carl Lerche <me@carllerche.com>"
+        ];
+        dependencies = [
+          {
+            name = "libc";
+            packageId = "libc";
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "log";
+            packageId = "log";
+          }
+          {
+            name = "miow";
+            packageId = "miow";
+            target = { target, features }: target."windows";
+          }
+          {
+            name = "ntapi";
+            packageId = "ntapi";
+            target = { target, features }: target."windows";
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "winsock2" "mswsock" ];
+          }
+        ];
+        features = {
+          "os-ext" = [ "os-poll" ];
+          "os-util" = [ "os-ext" ];
+          "pipe" = [ "os-ext" ];
+          "tcp" = [ "net" ];
+          "udp" = [ "net" ];
+          "uds" = [ "net" ];
+        };
+        resolvedDefaultFeatures = [ "default" "net" "os-ext" "os-poll" "os-util" "tcp" "udp" "uds" ];
+      };
+      "miow" = rec {
+        crateName = "miow";
+        version = "0.3.6";
+        edition = "2018";
+        sha256 = "15sqdhh29dqgw5xh59clwv6scbsbvdkbmdc16hbfvyq7b2sw2css";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "socket2";
+            packageId = "socket2";
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            features = [ "std" "fileapi" "handleapi" "ioapiset" "minwindef" "namedpipeapi" "ntdef" "synchapi" "winerror" "winsock2" "ws2def" "ws2ipdef" ];
+          }
+        ];
+        
+      };
+      "ntapi" = rec {
+        crateName = "ntapi";
+        version = "0.3.6";
+        edition = "2018";
+        sha256 = "0i5daj9sr8wyi5jkpwpybln2jqpn59z0mqfc0dpdidipwh1bjsrz";
+        authors = [
+          "MSxDOS <melcodos@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "winapi";
+            packageId = "winapi";
+            features = [ "cfg" "evntrace" "in6addr" "inaddr" "minwinbase" "ntsecapi" "windef" "winioctl" ];
+          }
+        ];
+        features = {
+          "default" = [ "user" ];
+          "impl-default" = [ "winapi/impl-default" ];
+        };
+        resolvedDefaultFeatures = [ "default" "user" ];
+      };
+      "num_cpus" = rec {
+        crateName = "num_cpus";
+        version = "1.13.0";
+        edition = "2015";
+        sha256 = "1cv6yxhz2zbnwn8pn1yn8grg7zsnd523947fby41a737aqvryj85";
+        authors = [
+          "Sean McArthur <sean@seanmonstar.com>"
+        ];
+        dependencies = [
+          {
+            name = "hermit-abi";
+            packageId = "hermit-abi";
+            target = { target, features }: (((target."arch" == "x86_64") || (target."arch" == "aarch64")) && (target."os" == "hermit"));
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+          }
+        ];
+        
+      };
+      "number_prefix" = rec {
+        crateName = "number_prefix";
+        version = "0.3.0";
+        edition = "2015";
+        sha256 = "0slm4mqmpgs6hvz22ycny9lvyvl9ivs80a1lncslp7lszz02zc0p";
+        authors = [
+          "Benjamin Sago <ogham@bsago.me>"
+        ];
+        features = {
+          "default" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "default" "std" ];
+      };
+      "once_cell" = rec {
+        crateName = "once_cell";
+        version = "1.5.2";
+        edition = "2018";
+        sha256 = "183zs1dbmsv24mkafjypf9qwjrx46an58vb004a162l113sl3g8k";
+        authors = [
+          "Aleksey Kladov <aleksey.kladov@gmail.com>"
+        ];
+        features = {
+          "default" = [ "std" ];
+          "std" = [ "alloc" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "default" "std" ];
+      };
+      "parking_lot" = rec {
+        crateName = "parking_lot";
+        version = "0.11.1";
+        edition = "2018";
+        sha256 = "1sqmgaia8zfd5fbnqw2w13ijh7crk3lf9vw4cb52vwlx0an48xvd";
+        authors = [
+          "Amanieu d'Antras <amanieu@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "instant";
+            packageId = "instant";
+          }
+          {
+            name = "lock_api";
+            packageId = "lock_api";
+          }
+          {
+            name = "parking_lot_core";
+            packageId = "parking_lot_core";
+          }
+        ];
+        features = {
+          "deadlock_detection" = [ "parking_lot_core/deadlock_detection" ];
+          "nightly" = [ "parking_lot_core/nightly" "lock_api/nightly" ];
+          "owning_ref" = [ "lock_api/owning_ref" ];
+          "serde" = [ "lock_api/serde" ];
+          "stdweb" = [ "instant/stdweb" ];
+          "wasm-bindgen" = [ "instant/wasm-bindgen" ];
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "parking_lot_core" = rec {
+        crateName = "parking_lot_core";
+        version = "0.8.1";
+        edition = "2018";
+        sha256 = "1l6fhxks1xc8vbcwlz2119canmaql5hfhny51552hibl8awdkinp";
+        authors = [
+          "Amanieu d'Antras <amanieu@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "cfg-if";
+            packageId = "cfg-if 1.0.0";
+          }
+          {
+            name = "instant";
+            packageId = "instant";
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "redox_syscall";
+            packageId = "redox_syscall";
+            target = { target, features }: (target."os" == "redox");
+          }
+          {
+            name = "smallvec";
+            packageId = "smallvec";
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "winnt" "ntstatus" "minwindef" "winerror" "winbase" "errhandlingapi" "handleapi" ];
+          }
+        ];
+        features = {
+          "deadlock_detection" = [ "petgraph" "thread-id" "backtrace" ];
+        };
+      };
+      "pin-project" = rec {
+        crateName = "pin-project";
+        version = "1.0.2";
+        edition = "2018";
+        sha256 = "19qw2nm2kk38v9j16nsm8j3fkh0g8pjq0k4cplx7i2f4q8vj5k4w";
+        authors = [
+          "Taiki Endo <te316e89@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "pin-project-internal";
+            packageId = "pin-project-internal";
+            usesDefaultFeatures = false;
+          }
+        ];
+        
+      };
+      "pin-project-internal" = rec {
+        crateName = "pin-project-internal";
+        version = "1.0.2";
+        edition = "2018";
+        sha256 = "0pwy3m32scf3ypjb9ai151lmaa27vyj06lc64i28l0r31fzx5s7q";
+        procMacro = true;
+        authors = [
+          "Taiki Endo <te316e89@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "full" "visit-mut" ];
+          }
+        ];
+        
+      };
+      "pin-project-lite" = rec {
+        crateName = "pin-project-lite";
+        version = "0.2.0";
+        edition = "2018";
+        sha256 = "070klqy200alrhxb79fxarrrrn0vbwg95dmqw9062vhqxibky1kb";
+        authors = [
+          "Taiki Endo <te316e89@gmail.com>"
+        ];
+        
+      };
+      "pin-utils" = rec {
+        crateName = "pin-utils";
+        version = "0.1.0";
+        edition = "2018";
+        sha256 = "117ir7vslsl2z1a7qzhws4pd01cg2d3338c47swjyvqv2n60v1wb";
+        authors = [
+          "Josef Brandl <mail@josefbrandl.de>"
+        ];
+        
+      };
+      "ppv-lite86" = rec {
+        crateName = "ppv-lite86";
+        version = "0.2.10";
+        edition = "2018";
+        sha256 = "0ms8198kclg4h96ggbziixxmsdl847s648kmbx11zlmjsqjccx5c";
+        authors = [
+          "The CryptoCorrosion Contributors"
+        ];
+        features = {
+          "default" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "simd" "std" ];
+      };
+      "proc-macro-hack" = rec {
+        crateName = "proc-macro-hack";
+        version = "0.5.19";
+        edition = "2018";
+        sha256 = "1rg0kzsj7lj00qj602d3h77spwfz48vixn1wbjp7a4yrq65w9w6v";
+        procMacro = true;
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        
+      };
+      "proc-macro-nested" = rec {
+        crateName = "proc-macro-nested";
+        version = "0.1.6";
+        edition = "2015";
+        sha256 = "0nnwm9bvp1fmr8nqjp8ynrkj97yzpsdh3062li8b0f4hzgd818gb";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        
+      };
+      "proc-macro2" = rec {
+        crateName = "proc-macro2";
+        version = "1.0.24";
+        edition = "2018";
+        sha256 = "0wcabxzrddcjmryndw8fpyxcq6rw63m701vx86xxf03y3bp081qy";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "unicode-xid";
+            packageId = "unicode-xid";
+          }
+        ];
+        features = {
+          "default" = [ "proc-macro" ];
+        };
+        resolvedDefaultFeatures = [ "default" "proc-macro" ];
+      };
+      "quote" = rec {
+        crateName = "quote";
+        version = "1.0.7";
+        edition = "2018";
+        sha256 = "0drzd6pq7whq7qhdvvs8wn6pbb0hhc12pz8wv80fb05ixhbksmma";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+          "default" = [ "proc-macro" ];
+          "proc-macro" = [ "proc-macro2/proc-macro" ];
+        };
+        resolvedDefaultFeatures = [ "default" "proc-macro" ];
+      };
+      "rand" = rec {
+        crateName = "rand";
+        version = "0.7.3";
+        edition = "2018";
+        sha256 = "00sdaimkbz491qgi6qxkv582yivl32m2jd401kzbn94vsiwicsva";
+        authors = [
+          "The Rand Project Developers"
+          "The Rust Project Developers"
+        ];
+        dependencies = [
+          {
+            name = "getrandom";
+            packageId = "getrandom";
+            rename = "getrandom_package";
+            optional = true;
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+            optional = true;
+            usesDefaultFeatures = false;
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "rand_chacha";
+            packageId = "rand_chacha";
+            usesDefaultFeatures = false;
+            target = { target, features }: (!(target."os" == "emscripten"));
+          }
+          {
+            name = "rand_core";
+            packageId = "rand_core";
+          }
+          {
+            name = "rand_hc";
+            packageId = "rand_hc";
+            target = { target, features }: (target."os" == "emscripten");
+          }
+        ];
+        devDependencies = [
+          {
+            name = "rand_hc";
+            packageId = "rand_hc";
+          }
+        ];
+        features = {
+          "alloc" = [ "rand_core/alloc" ];
+          "default" = [ "std" ];
+          "getrandom" = [ "getrandom_package" "rand_core/getrandom" ];
+          "nightly" = [ "simd_support" ];
+          "simd_support" = [ "packed_simd" ];
+          "small_rng" = [ "rand_pcg" ];
+          "std" = [ "rand_core/std" "rand_chacha/std" "alloc" "getrandom" "libc" ];
+          "stdweb" = [ "getrandom_package/stdweb" ];
+          "wasm-bindgen" = [ "getrandom_package/wasm-bindgen" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "default" "getrandom" "getrandom_package" "libc" "std" ];
+      };
+      "rand_chacha" = rec {
+        crateName = "rand_chacha";
+        version = "0.2.2";
+        edition = "2018";
+        sha256 = "00il36fkdbsmpr99p9ksmmp6dn1md7rmnwmz0rr77jbrca2yvj7l";
+        authors = [
+          "The Rand Project Developers"
+          "The Rust Project Developers"
+          "The CryptoCorrosion Contributors"
+        ];
+        dependencies = [
+          {
+            name = "ppv-lite86";
+            packageId = "ppv-lite86";
+            usesDefaultFeatures = false;
+            features = [ "simd" ];
+          }
+          {
+            name = "rand_core";
+            packageId = "rand_core";
+          }
+        ];
+        features = {
+          "default" = [ "std" "simd" ];
+          "std" = [ "ppv-lite86/std" ];
+        };
+        resolvedDefaultFeatures = [ "std" ];
+      };
+      "rand_core" = rec {
+        crateName = "rand_core";
+        version = "0.5.1";
+        edition = "2018";
+        sha256 = "06bdvx08v3rkz451cm7z59xwwqn1rkfh6v9ay77b14f8dwlybgch";
+        authors = [
+          "The Rand Project Developers"
+          "The Rust Project Developers"
+        ];
+        dependencies = [
+          {
+            name = "getrandom";
+            packageId = "getrandom";
+            optional = true;
+          }
+        ];
+        features = {
+          "serde1" = [ "serde" ];
+          "std" = [ "alloc" "getrandom" "getrandom/std" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "getrandom" "std" ];
+      };
+      "rand_hc" = rec {
+        crateName = "rand_hc";
+        version = "0.2.0";
+        edition = "2018";
+        sha256 = "0g31sqwpmsirdlwr0svnacr4dbqyz339im4ssl9738cjgfpjjcfa";
+        authors = [
+          "The Rand Project Developers"
+        ];
+        dependencies = [
+          {
+            name = "rand_core";
+            packageId = "rand_core";
+          }
+        ];
+        
+      };
+      "redox_syscall" = rec {
+        crateName = "redox_syscall";
+        version = "0.1.57";
+        edition = "2015";
+        sha256 = "1kh59fpwy33w9nwd5iyc283yglq8pf2s41hnhvl48iax9mz0zk21";
+        libName = "syscall";
+        authors = [
+          "Jeremy Soller <jackpot51@gmail.com>"
+        ];
+        
+      };
+      "regex" = rec {
+        crateName = "regex";
+        version = "1.4.2";
+        edition = "2015";
+        sha256 = "172bw2yryv65whn3n5vkww4kgk0bq08lx0zbln8xwia7xl9jrkrq";
+        authors = [
+          "The Rust Project Developers"
+        ];
+        dependencies = [
+          {
+            name = "regex-syntax";
+            packageId = "regex-syntax";
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+          "default" = [ "std" "perf" "unicode" "regex-syntax/default" ];
+          "perf" = [ "perf-cache" "perf-dfa" "perf-inline" "perf-literal" ];
+          "perf-cache" = [ "thread_local" ];
+          "perf-literal" = [ "aho-corasick" "memchr" ];
+          "unicode" = [ "unicode-age" "unicode-bool" "unicode-case" "unicode-gencat" "unicode-perl" "unicode-script" "unicode-segment" "regex-syntax/unicode" ];
+          "unicode-age" = [ "regex-syntax/unicode-age" ];
+          "unicode-bool" = [ "regex-syntax/unicode-bool" ];
+          "unicode-case" = [ "regex-syntax/unicode-case" ];
+          "unicode-gencat" = [ "regex-syntax/unicode-gencat" ];
+          "unicode-perl" = [ "regex-syntax/unicode-perl" ];
+          "unicode-script" = [ "regex-syntax/unicode-script" ];
+          "unicode-segment" = [ "regex-syntax/unicode-segment" ];
+          "unstable" = [ "pattern" ];
+          "use_std" = [ "std" ];
+        };
+        resolvedDefaultFeatures = [ "std" ];
+      };
+      "regex-syntax" = rec {
+        crateName = "regex-syntax";
+        version = "0.6.21";
+        edition = "2015";
+        sha256 = "12d176jkgw9749g07zjxz0n78nyvb2nqx3j4sp5aqyphvji1n61v";
+        authors = [
+          "The Rust Project Developers"
+        ];
+        features = {
+          "default" = [ "unicode" ];
+          "unicode" = [ "unicode-age" "unicode-bool" "unicode-case" "unicode-gencat" "unicode-perl" "unicode-script" "unicode-segment" ];
+        };
+      };
+      "remove_dir_all" = rec {
+        crateName = "remove_dir_all";
+        version = "0.5.3";
+        edition = "2015";
+        sha256 = "1rzqbsgkmr053bxxl04vmvsd1njyz0nxvly97aip6aa2cmb15k9s";
+        authors = [
+          "Aaronepower <theaaronepower@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "std" "errhandlingapi" "winerror" "fileapi" "winbase" ];
+          }
+        ];
+        
+      };
+      "ryu" = rec {
+        crateName = "ryu";
+        version = "1.0.5";
+        edition = "2018";
+        sha256 = "0vpqv1dj7fksa6hm3zpk5rbsjs0ifbfy7xwzsyyil0rx37a03lvi";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        features = {
+        };
+      };
+      "scopeguard" = rec {
+        crateName = "scopeguard";
+        version = "1.1.0";
+        edition = "2015";
+        sha256 = "1kbqm85v43rq92vx7hfiay6pmcga03vrjbbfwqpyj3pwsg3b16nj";
+        authors = [
+          "bluss"
+        ];
+        features = {
+          "default" = [ "use_std" ];
+        };
+      };
+      "serde" = rec {
+        crateName = "serde";
+        version = "1.0.118";
+        edition = "2015";
+        sha256 = "0028kv3dh3ix5g7jfws22zb9hcqq4cnpwn2lnlpam1wxhmil5ih6";
+        authors = [
+          "Erick Tryzelaar <erick.tryzelaar@gmail.com>"
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "serde_derive";
+            packageId = "serde_derive";
+            optional = true;
+          }
+        ];
+        devDependencies = [
+          {
+            name = "serde_derive";
+            packageId = "serde_derive";
+          }
+        ];
+        features = {
+          "default" = [ "std" ];
+          "derive" = [ "serde_derive" ];
+        };
+        resolvedDefaultFeatures = [ "default" "derive" "serde_derive" "std" ];
+      };
+      "serde_derive" = rec {
+        crateName = "serde_derive";
+        version = "1.0.118";
+        edition = "2015";
+        sha256 = "1pvj4v8k107ichsnm7jgm9kxyi2lf971x52bmxhm5mcwd4k3akf8";
+        procMacro = true;
+        authors = [
+          "Erick Tryzelaar <erick.tryzelaar@gmail.com>"
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "visit" ];
+          }
+        ];
+        features = {
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "serde_json" = rec {
+        crateName = "serde_json";
+        version = "1.0.60";
+        edition = "2018";
+        sha256 = "0yapc7xxk8dx12691yj0l13008rgvknmc6krvk8jwj7y4x6yh00m";
+        authors = [
+          "Erick Tryzelaar <erick.tryzelaar@gmail.com>"
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "itoa";
+            packageId = "itoa";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "ryu";
+            packageId = "ryu";
+          }
+          {
+            name = "serde";
+            packageId = "serde";
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+          "alloc" = [ "serde/alloc" ];
+          "default" = [ "std" ];
+          "preserve_order" = [ "indexmap" ];
+          "std" = [ "serde/std" ];
+        };
+        resolvedDefaultFeatures = [ "default" "std" ];
+      };
+      "signal-hook-registry" = rec {
+        crateName = "signal-hook-registry";
+        version = "1.2.2";
+        edition = "2015";
+        sha256 = "1ar0dd9q1w952knhs0fx7qfh4iq5jvcvwkw1xg5fmmandh6flcnf";
+        authors = [
+          "Michal 'vorner' Vaner <vorner@vorner.cz>"
+          "Masaki Hara <ackie.h.gmai@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "libc";
+            packageId = "libc";
+          }
+        ];
+        
+      };
+      "slab" = rec {
+        crateName = "slab";
+        version = "0.4.2";
+        edition = "2015";
+        sha256 = "1y59xsa27jk84sxzswjk60xcjf8b4fm5960jwpznrrcmasyva4f1";
+        authors = [
+          "Carl Lerche <me@carllerche.com>"
+        ];
+        
+      };
+      "smallvec" = rec {
+        crateName = "smallvec";
+        version = "1.5.1";
+        edition = "2018";
+        sha256 = "0xcxvc2lh2fj02d91v4dx1l4q14m5rb4yac788bhwxvxdl2lylmf";
+        authors = [
+          "The Servo Project Developers"
+        ];
+        features = {
+        };
+      };
+      "snafu" = rec {
+        crateName = "snafu";
+        version = "0.6.10";
+        edition = "2018";
+        sha256 = "19wwqxwb85pl040qk5xylj0vlznib3xzy9hcv2q0h8qv4qy2vcga";
+        authors = [
+          "Jake Goulding <jake.goulding@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "doc-comment";
+            packageId = "doc-comment";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "snafu-derive";
+            packageId = "snafu-derive";
+          }
+        ];
+        features = {
+          "backtraces" = [ "std" "backtrace" ];
+          "backtraces-impl-backtrace-crate" = [ "backtraces" ];
+          "default" = [ "std" "guide" ];
+          "futures" = [ "futures-core-crate" "pin-project" ];
+          "futures-01" = [ "futures-01-crate" ];
+          "internal-dev-dependencies" = [ "futures-crate" ];
+          "unstable-backtraces-impl-std" = [ "backtraces" "snafu-derive/unstable-backtraces-impl-std" ];
+        };
+        resolvedDefaultFeatures = [ "default" "guide" "std" ];
+      };
+      "snafu-derive" = rec {
+        crateName = "snafu-derive";
+        version = "0.6.10";
+        edition = "2018";
+        sha256 = "0nri7ma06g5kimpcdcm8359a55nmps5f3kcngy0j6bin7jhfy20m";
+        procMacro = true;
+        authors = [
+          "Jake Goulding <jake.goulding@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "full" ];
+          }
+        ];
+        features = {
+        };
+      };
+      "socket2" = rec {
+        crateName = "socket2";
+        version = "0.3.17";
+        edition = "2018";
+        sha256 = "00k98q2ab98j9ffmmsh0wlwck2apy83a7v5bfy122apfpmx98a9c";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "cfg-if";
+            packageId = "cfg-if 1.0.0";
+            target = { target, features }: (target."unix" || (target."os" == "redox"));
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+            target = { target, features }: (target."unix" || (target."os" == "redox"));
+            features = [ "align" ];
+          }
+          {
+            name = "redox_syscall";
+            packageId = "redox_syscall";
+            target = { target, features }: (target."os" == "redox");
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "handleapi" "ws2def" "ws2ipdef" "ws2tcpip" "minwindef" ];
+          }
+        ];
+        features = {
+        };
+      };
+      "strsim" = rec {
+        crateName = "strsim";
+        version = "0.8.0";
+        edition = "2015";
+        sha256 = "0sjsm7hrvjdifz661pjxq5w4hf190hx53fra8dfvamacvff139cf";
+        authors = [
+          "Danny Guo <dannyguo91@gmail.com>"
+        ];
+        
+      };
+      "syn" = rec {
+        crateName = "syn";
+        version = "1.0.54";
+        edition = "2018";
+        sha256 = "0i3z22zvzzsmrsbhi0ivpmv71fgxkcywjnf3alid8srxlrbzjals";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+            optional = true;
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "unicode-xid";
+            packageId = "unicode-xid";
+          }
+        ];
+        features = {
+          "default" = [ "derive" "parsing" "printing" "clone-impls" "proc-macro" ];
+          "printing" = [ "quote" ];
+          "proc-macro" = [ "proc-macro2/proc-macro" "quote/proc-macro" ];
+          "test" = [ "syn-test-suite/all-features" ];
+        };
+        resolvedDefaultFeatures = [ "clone-impls" "default" "derive" "full" "parsing" "printing" "proc-macro" "quote" "visit" "visit-mut" ];
+      };
+      "tempfile" = rec {
+        crateName = "tempfile";
+        version = "3.1.0";
+        edition = "2018";
+        sha256 = "1a9cfdqw70n7bcnkx05aih9xdba8lqazmqlkjpkmn2la6gcj8vks";
+        authors = [
+          "Steven Allen <steven@stebalien.com>"
+          "The Rust Project Developers"
+          "Ashley Mannix <ashleymannix@live.com.au>"
+          "Jason White <jasonaw0@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "cfg-if";
+            packageId = "cfg-if 0.1.10";
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "rand";
+            packageId = "rand";
+          }
+          {
+            name = "redox_syscall";
+            packageId = "redox_syscall";
+            target = { target, features }: (target."os" == "redox");
+          }
+          {
+            name = "remove_dir_all";
+            packageId = "remove_dir_all";
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "fileapi" "handleapi" "winbase" ];
+          }
+        ];
+        
+      };
+      "terminal_size" = rec {
+        crateName = "terminal_size";
+        version = "0.1.15";
+        edition = "2018";
+        sha256 = "1qfb07d040wh3m4yfnbxknda7i5fr56ypnwdwdgmzb1zpn1x3ljb";
+        authors = [
+          "Andrew Chin <achin@eminence32.net>"
+        ];
+        dependencies = [
+          {
+            name = "libc";
+            packageId = "libc";
+            target = { target, features }: (!target."windows");
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "handleapi" "processenv" "winbase" "wincon" "winnt" ];
+          }
+        ];
+        
+      };
+      "textwrap" = rec {
+        crateName = "textwrap";
+        version = "0.11.0";
+        edition = "2015";
+        sha256 = "0q5hky03ik3y50s9sz25r438bc4nwhqc6dqwynv4wylc807n29nk";
+        authors = [
+          "Martin Geisler <martin@geisler.net>"
+        ];
+        dependencies = [
+          {
+            name = "unicode-width";
+            packageId = "unicode-width";
+          }
+        ];
+        
+      };
+      "tokio" = rec {
+        crateName = "tokio";
+        version = "0.3.6";
+        edition = "2018";
+        sha256 = "0z78l7kn4y2qvghsp9dyqgvr1kjvv63pjq3d8nzi31q74lfa42vj";
+        authors = [
+          "Tokio Contributors <team@tokio.rs>"
+        ];
+        dependencies = [
+          {
+            name = "bytes";
+            packageId = "bytes";
+            optional = true;
+          }
+          {
+            name = "futures-core";
+            packageId = "futures-core";
+            optional = true;
+          }
+          {
+            name = "libc";
+            packageId = "libc";
+            optional = true;
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "memchr";
+            packageId = "memchr";
+            optional = true;
+          }
+          {
+            name = "mio";
+            packageId = "mio";
+            optional = true;
+          }
+          {
+            name = "num_cpus";
+            packageId = "num_cpus";
+            optional = true;
+          }
+          {
+            name = "once_cell";
+            packageId = "once_cell";
+            optional = true;
+          }
+          {
+            name = "parking_lot";
+            packageId = "parking_lot";
+            optional = true;
+          }
+          {
+            name = "pin-project-lite";
+            packageId = "pin-project-lite";
+          }
+          {
+            name = "signal-hook-registry";
+            packageId = "signal-hook-registry";
+            optional = true;
+            target = { target, features }: target."unix";
+          }
+          {
+            name = "slab";
+            packageId = "slab";
+            optional = true;
+          }
+          {
+            name = "tokio-macros";
+            packageId = "tokio-macros";
+            optional = true;
+          }
+          {
+            name = "winapi";
+            packageId = "winapi";
+            optional = true;
+            usesDefaultFeatures = false;
+            target = { target, features }: target."windows";
+          }
+        ];
+        buildDependencies = [
+          {
+            name = "autocfg";
+            packageId = "autocfg";
+          }
+        ];
+        devDependencies = [
+          {
+            name = "libc";
+            packageId = "libc";
+            target = {target, features}: target."unix";
+          }
+        ];
+        features = {
+          "full" = [ "fs" "io-util" "io-std" "macros" "net" "parking_lot" "process" "rt" "rt-multi-thread" "signal" "stream" "sync" "time" ];
+          "io-util" = [ "memchr" "bytes" ];
+          "macros" = [ "tokio-macros" ];
+          "net" = [ "libc" "mio/os-poll" "mio/os-util" "mio/tcp" "mio/udp" "mio/uds" ];
+          "process" = [ "bytes" "once_cell" "libc" "mio/os-poll" "mio/os-util" "mio/uds" "signal-hook-registry" "winapi/threadpoollegacyapiset" ];
+          "rt" = [ "slab" ];
+          "rt-multi-thread" = [ "num_cpus" "rt" ];
+          "signal" = [ "once_cell" "libc" "mio/os-poll" "mio/uds" "mio/os-util" "signal-hook-registry" "winapi/consoleapi" ];
+          "stream" = [ "futures-core" ];
+        };
+        resolvedDefaultFeatures = [ "bytes" "default" "fs" "full" "futures-core" "io-std" "io-util" "libc" "macros" "memchr" "mio" "net" "num_cpus" "once_cell" "parking_lot" "process" "rt" "rt-multi-thread" "signal" "signal-hook-registry" "slab" "stream" "sync" "time" "tokio-macros" "winapi" ];
+      };
+      "tokio-macros" = rec {
+        crateName = "tokio-macros";
+        version = "0.3.1";
+        edition = "2018";
+        sha256 = "0iaw1k9qcn3fjgl4qcqwl8if8jjdkldam4cn0j8qybfwnpdhzlr1";
+        procMacro = true;
+        authors = [
+          "Tokio Contributors <team@tokio.rs>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "full" ];
+          }
+        ];
+        
+      };
+      "unicode-width" = rec {
+        crateName = "unicode-width";
+        version = "0.1.8";
+        edition = "2015";
+        sha256 = "1qxizyi6xbcqyi4z79p523ywvmgsfcgfqb3zv3c8i6x1jcc5jdwk";
+        authors = [
+          "kwantam <kwantam@gmail.com>"
+          "Manish Goregaokar <manishsmail@gmail.com>"
+        ];
+        features = {
+          "rustc-dep-of-std" = [ "std" "core" "compiler_builtins" ];
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "unicode-xid" = rec {
+        crateName = "unicode-xid";
+        version = "0.2.1";
+        edition = "2015";
+        sha256 = "0r6mknipyy9vpz8mwmxvkx65ff2ha1n2pxqjj6f46lcn8yrhpzpp";
+        authors = [
+          "erick.tryzelaar <erick.tryzelaar@gmail.com>"
+          "kwantam <kwantam@gmail.com>"
+        ];
+        features = {
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "vec_map" = rec {
+        crateName = "vec_map";
+        version = "0.8.2";
+        edition = "2015";
+        sha256 = "1481w9g1dw9rxp3l6snkdqihzyrd2f8vispzqmwjwsdyhw8xzggi";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+          "Jorge Aparicio <japaricious@gmail.com>"
+          "Alexis Beingessner <a.beingessner@gmail.com>"
+          "Brian Anderson <>"
+          "tbu- <>"
+          "Manish Goregaokar <>"
+          "Aaron Turon <aturon@mozilla.com>"
+          "Adolfo Ochagavía <>"
+          "Niko Matsakis <>"
+          "Steven Fackler <>"
+          "Chase Southwood <csouth3@illinois.edu>"
+          "Eduard Burtescu <>"
+          "Florian Wilkens <>"
+          "Félix Raimundo <>"
+          "Tibor Benke <>"
+          "Markus Siemens <markus@m-siemens.de>"
+          "Josh Branchaud <jbranchaud@gmail.com>"
+          "Huon Wilson <dbau.pp@gmail.com>"
+          "Corey Farwell <coref@rwell.org>"
+          "Aaron Liblong <>"
+          "Nick Cameron <nrc@ncameron.org>"
+          "Patrick Walton <pcwalton@mimiga.net>"
+          "Felix S Klock II <>"
+          "Andrew Paseltiner <apaseltiner@gmail.com>"
+          "Sean McArthur <sean.monstar@gmail.com>"
+          "Vadim Petrochenkov <>"
+        ];
+        features = {
+          "eders" = [ "serde" ];
+        };
+      };
+      "wasi" = rec {
+        crateName = "wasi";
+        version = "0.9.0+wasi-snapshot-preview1";
+        edition = "2018";
+        sha256 = "06g5v3vrdapfzvfq662cij7v8a1flwr2my45nnncdv2galrdzkfc";
+        authors = [
+          "The Cranelift Project Developers"
+        ];
+        features = {
+          "default" = [ "std" ];
+          "rustc-dep-of-std" = [ "compiler_builtins" "core" "rustc-std-workspace-alloc" ];
+        };
+        resolvedDefaultFeatures = [ "default" "std" ];
+      };
+      "winapi" = rec {
+        crateName = "winapi";
+        version = "0.3.9";
+        edition = "2015";
+        sha256 = "06gl025x418lchw1wxj64ycr7gha83m44cjr5sarhynd9xkrm0sw";
+        authors = [
+          "Peter Atashian <retep998@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "winapi-i686-pc-windows-gnu";
+            packageId = "winapi-i686-pc-windows-gnu";
+            target = { target, features }: (stdenv.hostPlatform.config == "i686-pc-windows-gnu");
+          }
+          {
+            name = "winapi-x86_64-pc-windows-gnu";
+            packageId = "winapi-x86_64-pc-windows-gnu";
+            target = { target, features }: (stdenv.hostPlatform.config == "x86_64-pc-windows-gnu");
+          }
+        ];
+        features = {
+          "debug" = [ "impl-debug" ];
+        };
+        resolvedDefaultFeatures = [ "cfg" "consoleapi" "errhandlingapi" "evntrace" "fileapi" "handleapi" "in6addr" "inaddr" "ioapiset" "minwinbase" "minwindef" "mswsock" "namedpipeapi" "ntdef" "ntsecapi" "ntstatus" "processenv" "std" "synchapi" "threadpoollegacyapiset" "winbase" "wincon" "windef" "winerror" "winioctl" "winnt" "winsock2" "winuser" "ws2def" "ws2ipdef" "ws2tcpip" ];
+      };
+      "winapi-i686-pc-windows-gnu" = rec {
+        crateName = "winapi-i686-pc-windows-gnu";
+        version = "0.4.0";
+        edition = "2015";
+        sha256 = "1dmpa6mvcvzz16zg6d5vrfy4bxgg541wxrcip7cnshi06v38ffxc";
+        authors = [
+          "Peter Atashian <retep998@gmail.com>"
+        ];
+        
+      };
+      "winapi-util" = rec {
+        crateName = "winapi-util";
+        version = "0.1.5";
+        edition = "2018";
+        sha256 = "0y71bp7f6d536czj40dhqk0d55wfbbwqfp2ymqf1an5ibgl6rv3h";
+        authors = [
+          "Andrew Gallant <jamslam@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "winapi";
+            packageId = "winapi";
+            target = { target, features }: target."windows";
+            features = [ "std" "consoleapi" "errhandlingapi" "fileapi" "minwindef" "processenv" "winbase" "wincon" "winerror" "winnt" ];
+          }
+        ];
+        
+      };
+      "winapi-x86_64-pc-windows-gnu" = rec {
+        crateName = "winapi-x86_64-pc-windows-gnu";
+        version = "0.4.0";
+        edition = "2015";
+        sha256 = "0gqq64czqb64kskjryj8isp62m2sgvx25yyj3kpc2myh85w24bki";
+        authors = [
+          "Peter Atashian <retep998@gmail.com>"
+        ];
+        
+      };
+    };
+
+    #
+# crate2nix/default.nix (excerpt start)
+#
+
+  /* Target (platform) data for conditional dependencies.
+     This corresponds roughly to what buildRustCrate is setting.
+  */
+  defaultTarget = {
+    unix = true;
+    windows = false;
+    fuchsia = true;
+    test = false;
+
+    # This doesn't appear to be officially documented anywhere yet.
+    # See https://github.com/rust-lang-nursery/rust-forge/issues/101.
+    os =
+      if stdenv.hostPlatform.isDarwin
+      then "macos"
+      else stdenv.hostPlatform.parsed.kernel.name;
+    arch = stdenv.hostPlatform.parsed.cpu.name;
+    family = "unix";
+    env = "gnu";
+    endian =
+      if stdenv.hostPlatform.parsed.cpu.significantByte.name == "littleEndian"
+      then "little" else "big";
+    pointer_width = toString stdenv.hostPlatform.parsed.cpu.bits;
+    vendor = stdenv.hostPlatform.parsed.vendor.name;
+    debug_assertions = false;
+  };
+
+  /* Filters common temp files and build files. */
+  # TODO(pkolloch): Substitute with gitignore filter
+  sourceFilter = name: type:
+    let
+      baseName = builtins.baseNameOf (builtins.toString name);
+    in
+      ! (
+        # Filter out git
+        baseName == ".gitignore"
+        || (type == "directory" && baseName == ".git")
+
+        # Filter out build results
+        || (
+          type == "directory" && (
+            baseName == "target"
+            || baseName == "_site"
+            || baseName == ".sass-cache"
+            || baseName == ".jekyll-metadata"
+            || baseName == "build-artifacts"
+          )
+        )
+
+        # Filter out nix-build result symlinks
+        || (
+          type == "symlink" && lib.hasPrefix "result" baseName
+        )
+
+        # Filter out IDE config
+        || (
+          type == "directory" && (
+            baseName == ".idea" || baseName == ".vscode"
+          )
+        ) || lib.hasSuffix ".iml" baseName
+
+        # Filter out nix build files
+        || baseName == "Cargo.nix"
+
+        # Filter out editor backup / swap files.
+        || lib.hasSuffix "~" baseName
+        || builtins.match "^\\.sw[a-z]$$" baseName != null
+        || builtins.match "^\\..*\\.sw[a-z]$$" baseName != null
+        || lib.hasSuffix ".tmp" baseName
+        || lib.hasSuffix ".bak" baseName
+        || baseName == "tests.nix"
+      );
+
+  /* Returns a crate which depends on successful test execution
+     of crate given as the second argument.
+
+     testCrateFlags: list of flags to pass to the test exectuable
+     testInputs: list of packages that should be available during test execution
+  */
+  crateWithTest = { crate, testCrate, testCrateFlags, testInputs }:
+    assert builtins.typeOf testCrateFlags == "list";
+    assert builtins.typeOf testInputs == "list";
+    let
+      # override the `crate` so that it will build and execute tests instead of
+      # building the actual lib and bin targets We just have to pass `--test`
+      # to rustc and it will do the right thing.  We execute the tests and copy
+      # their log and the test executables to $out for later inspection.
+      test =
+        let
+          drv = testCrate.override
+            (
+              _: {
+                buildTests = true;
+              }
+            );
+        in
+        pkgs.runCommand "run-tests-${testCrate.name}"
+          {
+            inherit testCrateFlags;
+            buildInputs = testInputs;
+          } ''
+          set -ex
+
+          export RUST_BACKTRACE=1
+
+          # recreate a file hierarchy as when running tests with cargo
+
+          # the source for test data
+          ${pkgs.xorg.lndir}/bin/lndir ${crate.src}
+
+          # build outputs
+          testRoot=target/debug
+          mkdir -p $testRoot
+
+          # executables of the crate
+          # we copy to prevent std::env::current_exe() to resolve to a store location
+          for i in ${crate}/bin/*; do
+            cp "$i" "$testRoot"
+          done
+          chmod +w -R .
+
+          # test harness executables are suffixed with a hash, like cargo does
+          # this allows to prevent name collision with the main
+          # executables of the crate
+          hash=$(basename $out)
+          for file in ${drv}/tests/*; do
+            f=$testRoot/$(basename $file)-$hash
+            cp $file $f
+            $f $testCrateFlags 2>&1 | tee -a $out
+          done
+        '';
+    in
+    pkgs.runCommand "${crate.name}-linked"
+      {
+        inherit (crate) outputs crateName;
+        passthru = (crate.passthru or { }) // {
+          inherit test;
+        };
+      } ''
+      echo tested by ${test}
+      ${lib.concatMapStringsSep "\n" (output: "ln -s ${crate.${output}} ${"$"}${output}") crate.outputs}
+    '';
+
+  /* A restricted overridable version of builtRustCratesWithFeatures. */
+  buildRustCrateWithFeatures =
+    { packageId
+    , features ? rootFeatures
+    , crateOverrides ? defaultCrateOverrides
+    , buildRustCrateFunc ? null
+    , runTests ? false
+    , testCrateFlags ? [ ]
+    , testInputs ? [ ]
+    }:
+    lib.makeOverridable
+      (
+        { features
+        , crateOverrides
+        , runTests
+        , testCrateFlags
+        , testInputs
+        }:
+        let
+          buildRustCrateFuncOverriden =
+            if buildRustCrateFunc != null
+            then buildRustCrateFunc
+            else
+              (
+                if crateOverrides == pkgs.defaultCrateOverrides
+                then buildRustCrate
+                else
+                  buildRustCrate.override {
+                    defaultCrateOverrides = crateOverrides;
+                  }
+              );
+          builtRustCrates = builtRustCratesWithFeatures {
+            inherit packageId features;
+            buildRustCrateFunc = buildRustCrateFuncOverriden;
+            runTests = false;
+          };
+          builtTestRustCrates = builtRustCratesWithFeatures {
+            inherit packageId features;
+            buildRustCrateFunc = buildRustCrateFuncOverriden;
+            runTests = true;
+          };
+          drv = builtRustCrates.${packageId};
+          testDrv = builtTestRustCrates.${packageId};
+          derivation =
+            if runTests then
+              crateWithTest
+                {
+                  crate = drv;
+                  testCrate = testDrv;
+                  inherit testCrateFlags testInputs;
+                }
+            else drv;
+        in
+        derivation
+      )
+      { inherit features crateOverrides runTests testCrateFlags testInputs; };
+
+  /* Returns an attr set with packageId mapped to the result of buildRustCrateFunc
+     for the corresponding crate.
+  */
+  builtRustCratesWithFeatures =
+    { packageId
+    , features
+    , crateConfigs ? crates
+    , buildRustCrateFunc
+    , runTests
+    , target ? defaultTarget
+    } @ args:
+      assert (builtins.isAttrs crateConfigs);
+      assert (builtins.isString packageId);
+      assert (builtins.isList features);
+      assert (builtins.isAttrs target);
+      assert (builtins.isBool runTests);
+      let
+        rootPackageId = packageId;
+        mergedFeatures = mergePackageFeatures
+          (
+            args // {
+              inherit rootPackageId;
+              target = target // { test = runTests; };
+            }
+          );
+        buildByPackageId = packageId: buildByPackageIdImpl packageId;
+
+        # Memoize built packages so that reappearing packages are only built once.
+        builtByPackageId =
+          lib.mapAttrs (packageId: value: buildByPackageId packageId) crateConfigs;
+        buildByPackageIdImpl = packageId:
+          let
+            features = mergedFeatures."${packageId}" or [ ];
+            crateConfig' = crateConfigs."${packageId}";
+            crateConfig =
+              builtins.removeAttrs crateConfig' [ "resolvedDefaultFeatures" "devDependencies" ];
+            devDependencies =
+              lib.optionals
+                (runTests && packageId == rootPackageId)
+                (crateConfig'.devDependencies or [ ]);
+            dependencies =
+              dependencyDerivations {
+                inherit builtByPackageId features target;
+                dependencies =
+                  (crateConfig.dependencies or [ ])
+                  ++ devDependencies;
+              };
+            buildDependencies =
+              dependencyDerivations {
+                inherit builtByPackageId features target;
+                dependencies = crateConfig.buildDependencies or [ ];
+              };
+            filterEnabledDependenciesForThis = dependencies: filterEnabledDependencies {
+              inherit dependencies features target;
+            };
+            dependenciesWithRenames =
+              lib.filter (d: d ? "rename")
+                (
+                  filterEnabledDependenciesForThis
+                    (
+                      (crateConfig.buildDependencies or [ ])
+                      ++ (crateConfig.dependencies or [ ])
+                      ++ devDependencies
+                    )
+                );
+            # Crate renames have the form:
+            #
+            # {
+            #    crate_name = [
+            #       { version = "1.2.3"; rename = "crate_name01"; }
+            #    ];
+            #    # ...
+            # }
+            crateRenames =
+              let
+                grouped =
+                  lib.groupBy
+                    (dependency: dependency.name)
+                    dependenciesWithRenames;
+                versionAndRename = dep:
+                  let
+                    package = builtByPackageId."${dep.packageId}";
+                  in
+                  { inherit (dep) rename; version = package.version; };
+              in
+              lib.mapAttrs (name: choices: builtins.map versionAndRename choices) grouped;
+          in
+          buildRustCrateFunc
+            (
+              crateConfig // {
+                src = crateConfig.src or (
+                  pkgs.fetchurl rec {
+                    name = "${crateConfig.crateName}-${crateConfig.version}.tar.gz";
+                    # https://www.pietroalbini.org/blog/downloading-crates-io/
+                    # Not rate-limited, CDN URL.
+                    url = "https://static.crates.io/crates/${crateConfig.crateName}/${crateConfig.crateName}-${crateConfig.version}.crate";
+                    sha256 =
+                      assert (lib.assertMsg (crateConfig ? sha256) "Missing sha256 for ${name}");
+                      crateConfig.sha256;
+                  }
+                );
+                extraRustcOpts = lib.lists.optional (targetFeatures != [ ]) "-C target-feature=${stdenv.lib.concatMapStringsSep "," (x: "+${x}") targetFeatures}";
+                inherit features dependencies buildDependencies crateRenames release;
+              }
+            );
+      in
+      builtByPackageId;
+
+  /* Returns the actual derivations for the given dependencies. */
+  dependencyDerivations =
+    { builtByPackageId
+    , features
+    , dependencies
+    , target
+    }:
+      assert (builtins.isAttrs builtByPackageId);
+      assert (builtins.isList features);
+      assert (builtins.isList dependencies);
+      assert (builtins.isAttrs target);
+      let
+        enabledDependencies = filterEnabledDependencies {
+          inherit dependencies features target;
+        };
+        depDerivation = dependency: builtByPackageId.${dependency.packageId};
+      in
+      map depDerivation enabledDependencies;
+
+  /* Returns a sanitized version of val with all values substituted that cannot
+     be serialized as JSON.
+  */
+  sanitizeForJson = val:
+    if builtins.isAttrs val
+    then lib.mapAttrs (n: v: sanitizeForJson v) val
+    else if builtins.isList val
+    then builtins.map sanitizeForJson val
+    else if builtins.isFunction val
+    then "function"
+    else val;
+
+  /* Returns various tools to debug a crate. */
+  debugCrate = { packageId, target ? defaultTarget }:
+    assert (builtins.isString packageId);
+    let
+      debug = rec {
+        # The built tree as passed to buildRustCrate.
+        buildTree = buildRustCrateWithFeatures {
+          buildRustCrateFunc = lib.id;
+          inherit packageId;
+        };
+        sanitizedBuildTree = sanitizeForJson buildTree;
+        dependencyTree = sanitizeForJson
+          (
+            buildRustCrateWithFeatures {
+              buildRustCrateFunc = crate: {
+                "01_crateName" = crate.crateName or false;
+                "02_features" = crate.features or [ ];
+                "03_dependencies" = crate.dependencies or [ ];
+              };
+              inherit packageId;
+            }
+          );
+        mergedPackageFeatures = mergePackageFeatures {
+          features = rootFeatures;
+          inherit packageId target;
+        };
+        diffedDefaultPackageFeatures = diffDefaultPackageFeatures {
+          inherit packageId target;
+        };
+      };
+    in
+    { internal = debug; };
+
+  /* Returns differences between cargo default features and crate2nix default
+     features.
+
+     This is useful for verifying the feature resolution in crate2nix.
+  */
+  diffDefaultPackageFeatures =
+    { crateConfigs ? crates
+    , packageId
+    , target
+    }:
+      assert (builtins.isAttrs crateConfigs);
+      let
+        prefixValues = prefix: lib.mapAttrs (n: v: { "${prefix}" = v; });
+        mergedFeatures =
+          prefixValues
+            "crate2nix"
+            (mergePackageFeatures { inherit crateConfigs packageId target; features = [ "default" ]; });
+        configs = prefixValues "cargo" crateConfigs;
+        combined = lib.foldAttrs (a: b: a // b) { } [ mergedFeatures configs ];
+        onlyInCargo =
+          builtins.attrNames
+            (lib.filterAttrs (n: v: !(v ? "crate2nix") && (v ? "cargo")) combined);
+        onlyInCrate2Nix =
+          builtins.attrNames
+            (lib.filterAttrs (n: v: (v ? "crate2nix") && !(v ? "cargo")) combined);
+        differentFeatures = lib.filterAttrs
+          (
+            n: v:
+              (v ? "crate2nix")
+              && (v ? "cargo")
+              && (v.crate2nix.features or [ ]) != (v."cargo".resolved_default_features or [ ])
+          )
+          combined;
+      in
+      builtins.toJSON {
+        inherit onlyInCargo onlyInCrate2Nix differentFeatures;
+      };
+
+  /* Returns an attrset mapping packageId to the list of enabled features.
+
+     If multiple paths to a dependency enable different features, the
+     corresponding feature sets are merged. Features in rust are additive.
+  */
+  mergePackageFeatures =
+    { crateConfigs ? crates
+    , packageId
+    , rootPackageId ? packageId
+    , features ? rootFeatures
+    , dependencyPath ? [ crates.${packageId}.crateName ]
+    , featuresByPackageId ? { }
+    , target
+      # Adds devDependencies to the crate with rootPackageId.
+    , runTests ? false
+    , ...
+    } @ args:
+      assert (builtins.isAttrs crateConfigs);
+      assert (builtins.isString packageId);
+      assert (builtins.isString rootPackageId);
+      assert (builtins.isList features);
+      assert (builtins.isList dependencyPath);
+      assert (builtins.isAttrs featuresByPackageId);
+      assert (builtins.isAttrs target);
+      assert (builtins.isBool runTests);
+      let
+        crateConfig = crateConfigs."${packageId}" or (builtins.throw "Package not found: ${packageId}");
+        expandedFeatures = expandFeatures (crateConfig.features or { }) features;
+        depWithResolvedFeatures = dependency:
+          let
+            packageId = dependency.packageId;
+            features = dependencyFeatures expandedFeatures dependency;
+          in
+          { inherit packageId features; };
+        resolveDependencies = cache: path: dependencies:
+          assert (builtins.isAttrs cache);
+          assert (builtins.isList dependencies);
+          let
+            enabledDependencies = filterEnabledDependencies {
+              inherit dependencies target;
+              features = expandedFeatures;
+            };
+            directDependencies = map depWithResolvedFeatures enabledDependencies;
+            foldOverCache = op: lib.foldl op cache directDependencies;
+          in
+          foldOverCache
+            (
+              cache: { packageId, features }:
+                let
+                  cacheFeatures = cache.${packageId} or [ ];
+                  combinedFeatures = sortedUnique (cacheFeatures ++ features);
+                in
+                if cache ? ${packageId} && cache.${packageId} == combinedFeatures
+                then cache
+                else
+                  mergePackageFeatures {
+                    features = combinedFeatures;
+                    featuresByPackageId = cache;
+                    inherit crateConfigs packageId target runTests rootPackageId;
+                  }
+            );
+        cacheWithSelf =
+          let
+            cacheFeatures = featuresByPackageId.${packageId} or [ ];
+            combinedFeatures = sortedUnique (cacheFeatures ++ expandedFeatures);
+          in
+          featuresByPackageId // {
+            "${packageId}" = combinedFeatures;
+          };
+        cacheWithDependencies =
+          resolveDependencies cacheWithSelf "dep"
+            (
+              crateConfig.dependencies or [ ]
+              ++ lib.optionals
+                (runTests && packageId == rootPackageId)
+                (crateConfig.devDependencies or [ ])
+            );
+        cacheWithAll =
+          resolveDependencies
+            cacheWithDependencies "build"
+            (crateConfig.buildDependencies or [ ]);
+      in
+      cacheWithAll;
+
+  /* Returns the enabled dependencies given the enabled features. */
+  filterEnabledDependencies = { dependencies, features, target }:
+    assert (builtins.isList dependencies);
+    assert (builtins.isList features);
+    assert (builtins.isAttrs target);
+
+    lib.filter
+      (
+        dep:
+        let
+          targetFunc = dep.target or (features: true);
+        in
+        targetFunc { inherit features target; }
+        && (
+          !(dep.optional or false)
+          || builtins.any (doesFeatureEnableDependency dep) features
+        )
+      )
+      dependencies;
+
+  /* Returns whether the given feature should enable the given dependency. */
+  doesFeatureEnableDependency = { name, rename ? null, ... }: feature:
+    let
+      prefix = "${name}/";
+      len = builtins.stringLength prefix;
+      startsWithPrefix = builtins.substring 0 len feature == prefix;
+    in
+    (rename == null && feature == name)
+    || (rename != null && rename == feature)
+    || startsWithPrefix;
+
+  /* Returns the expanded features for the given inputFeatures by applying the
+     rules in featureMap.
+
+     featureMap is an attribute set which maps feature names to lists of further
+     feature names to enable in case this feature is selected.
+  */
+  expandFeatures = featureMap: inputFeatures:
+    assert (builtins.isAttrs featureMap);
+    assert (builtins.isList inputFeatures);
+    let
+      expandFeature = feature:
+        assert (builtins.isString feature);
+        [ feature ] ++ (expandFeatures featureMap (featureMap."${feature}" or [ ]));
+      outFeatures = lib.concatMap expandFeature inputFeatures;
+    in
+    sortedUnique outFeatures;
+
+  /*
+     Returns the actual features for the given dependency.
+
+     features: The features of the crate that refers this dependency.
+  */
+  dependencyFeatures = features: dependency:
+    assert (builtins.isList features);
+    assert (builtins.isAttrs dependency);
+    let
+      defaultOrNil =
+        if dependency.usesDefaultFeatures or true
+        then [ "default" ]
+        else [ ];
+      explicitFeatures = dependency.features or [ ];
+      additionalDependencyFeatures =
+        let
+          dependencyPrefix = (dependency.rename or dependency.name) + "/";
+          dependencyFeatures =
+            builtins.filter (f: lib.hasPrefix dependencyPrefix f) features;
+        in
+        builtins.map (lib.removePrefix dependencyPrefix) dependencyFeatures;
+    in
+    defaultOrNil ++ explicitFeatures ++ additionalDependencyFeatures;
+
+  /* Sorts and removes duplicates from a list of strings. */
+  sortedUnique = features:
+    assert (builtins.isList features);
+    assert (builtins.all builtins.isString features);
+    let
+      outFeaturesSet = lib.foldl (set: feature: set // { "${feature}" = 1; }) { } features;
+      outFeaturesUnique = builtins.attrNames outFeaturesSet;
+    in
+    builtins.sort (a: b: a < b) outFeaturesUnique;
+
+  deprecationWarning = message: value:
+    if strictDeprecation
+    then builtins.throw "strictDeprecation enabled, aborting: ${message}"
+    else builtins.trace message value;
+
+  #
+  # crate2nix/default.nix (excerpt end)
+  #
+
+  };
+}
diff --git a/default.nix b/default.nix
new file mode 100644
index 0000000..f930ad2
--- /dev/null
+++ b/default.nix
@@ -0,0 +1,5 @@
+{
+  pkgs ? import ./pkgs.nix,
+}: let
+  cargo = pkgs.callPackage ./Cargo.nix {};
+in cargo.rootCrate.build
diff --git a/nix/sources.json b/nix/sources.json
new file mode 100644
index 0000000..f2d8a9f
--- /dev/null
+++ b/nix/sources.json
@@ -0,0 +1,50 @@
+{
+    "crate2nix": {
+        "branch": "master",
+        "description": "nix build file generator for rust crates",
+        "homepage": "",
+        "owner": "kolloch",
+        "repo": "crate2nix",
+        "rev": "0c81027889259c6a45221a157f9c4a56e7235c85",
+        "sha256": "0wp1i83ralnz0v6a95122d0hfzwlg1281lvv3mzrxcxl8mka8z3n",
+        "type": "tarball",
+        "url": "https://github.com/kolloch/crate2nix/archive/0c81027889259c6a45221a157f9c4a56e7235c85.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "niv": {
+        "branch": "master",
+        "description": "Easy dependency management for Nix projects",
+        "homepage": "https://github.com/nmattia/niv",
+        "owner": "nmattia",
+        "repo": "niv",
+        "rev": "ba57d5a29b4e0f2085917010380ef3ddc3cf380f",
+        "sha256": "1kpsvc53x821cmjg1khvp1nz7906gczq8mp83664cr15h94sh8i4",
+        "type": "tarball",
+        "url": "https://github.com/nmattia/niv/archive/ba57d5a29b4e0f2085917010380ef3ddc3cf380f.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixos-20.09",
+        "description": "Nix Packages collection",
+        "homepage": "",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "b94726217f7cdc02ddf277b65553762d520da196",
+        "sha256": "1v3v7f2apmsdwv1w6hvsxr8whggjbiaxy00k47pxdzyigxv3s400",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/b94726217f7cdc02ddf277b65553762d520da196.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs-mozilla": {
+        "branch": "master",
+        "description": "mozilla related nixpkgs (extends nixos/nixpkgs repo)",
+        "homepage": null,
+        "owner": "mozilla",
+        "repo": "nixpkgs-mozilla",
+        "rev": "8c007b60731c07dd7a052cce508de3bb1ae849b4",
+        "sha256": "1zybp62zz0h077zm2zmqs2wcg3whg6jqaah9hcl1gv4x8af4zhs6",
+        "type": "tarball",
+        "url": "https://github.com/mozilla/nixpkgs-mozilla/archive/8c007b60731c07dd7a052cce508de3bb1ae849b4.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    }
+}
diff --git a/nix/sources.nix b/nix/sources.nix
new file mode 100644
index 0000000..b796fff
--- /dev/null
+++ b/nix/sources.nix
@@ -0,0 +1,171 @@
+# This file has been generated by Niv.
+
+let
+
+  #
+  # The fetchers. fetch_<type> fetches specs of type <type>.
+  #
+
+  fetch_file = pkgs: name: spec:
+    let
+      name' = sanitizeName name + "-src";
+    in
+      if spec.builtin or true then
+        builtins_fetchurl { inherit (spec) url sha256; name = name'; }
+      else
+        pkgs.fetchurl { inherit (spec) url sha256; name = name'; };
+
+  fetch_tarball = pkgs: name: spec:
+    let
+      name' = sanitizeName name + "-src";
+    in
+      if spec.builtin or true then
+        builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
+      else
+        pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
+
+  fetch_git = name: spec:
+    let
+      ref =
+        if spec ? ref then spec.ref else
+          if spec ? branch then "refs/heads/${spec.branch}" else
+            if spec ? tag then "refs/tags/${spec.tag}" else
+              abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
+    in
+      builtins.fetchGit { url = spec.repo; inherit (spec) rev; inherit ref; };
+
+  fetch_local = spec: spec.path;
+
+  fetch_builtin-tarball = name: throw
+    ''[${name}] The niv type "builtin-tarball" is deprecated. You should instead use `builtin = true`.
+        $ niv modify ${name} -a type=tarball -a builtin=true'';
+
+  fetch_builtin-url = name: throw
+    ''[${name}] The niv type "builtin-url" will soon be deprecated. You should instead use `builtin = true`.
+        $ niv modify ${name} -a type=file -a builtin=true'';
+
+  #
+  # Various helpers
+  #
+
+  # https://github.com/NixOS/nixpkgs/pull/83241/files#diff-c6f540a4f3bfa4b0e8b6bafd4cd54e8bR695
+  sanitizeName = name:
+    (
+      concatMapStrings (s: if builtins.isList s then "-" else s)
+        (
+          builtins.split "[^[:alnum:]+._?=-]+"
+            ((x: builtins.elemAt (builtins.match "\\.*(.*)" x) 0) name)
+        )
+    );
+
+  # The set of packages used when specs are fetched using non-builtins.
+  mkPkgs = sources: system:
+    let
+      sourcesNixpkgs =
+        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) { inherit system; };
+      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
+      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
+    in
+      if builtins.hasAttr "nixpkgs" sources
+      then sourcesNixpkgs
+      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
+        import <nixpkgs> {}
+      else
+        abort
+          ''
+            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+            add a package called "nixpkgs" to your sources.json.
+          '';
+
+  # The actual fetching function.
+  fetch = pkgs: name: spec:
+
+    if ! builtins.hasAttr "type" spec then
+      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
+    else if spec.type == "file" then fetch_file pkgs name spec
+    else if spec.type == "tarball" then fetch_tarball pkgs name spec
+    else if spec.type == "git" then fetch_git name spec
+    else if spec.type == "local" then fetch_local spec
+    else if spec.type == "builtin-tarball" then fetch_builtin-tarball name
+    else if spec.type == "builtin-url" then fetch_builtin-url name
+    else
+      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
+
+  # If the environment variable NIV_OVERRIDE_${name} is set, then use
+  # the path directly as opposed to the fetched source.
+  replace = name: drv:
+    let
+      saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
+      ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
+    in
+      if ersatz == "" then drv else ersatz;
+
+  # Ports of functions for older nix versions
+
+  # a Nix version of mapAttrs if the built-in doesn't exist
+  mapAttrs = builtins.mapAttrs or (
+    f: set: with builtins;
+    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
+  );
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295
+  range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1);
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257
+  stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1));
+
+  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269
+  stringAsChars = f: s: concatStrings (map f (stringToCharacters s));
+  concatMapStrings = f: list: concatStrings (map f list);
+  concatStrings = builtins.concatStringsSep "";
+
+  # https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331
+  optionalAttrs = cond: as: if cond then as else {};
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball = { url, name ? null, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchTarball;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchTarball ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
+      else
+        fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl = { url, name ? null, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchurl;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchurl ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
+      else
+        fetchurl attrs;
+
+  # Create the final "sources" from the config
+  mkSources = config:
+    mapAttrs (
+      name: spec:
+        if builtins.hasAttr "outPath" spec
+        then abort
+          "The values in sources.json should not have an 'outPath' attribute"
+        else
+          spec // { outPath = replace name (fetch config.pkgs name spec); }
+    ) config.sources;
+
+  # The "config" used by the fetchers
+  mkConfig =
+    { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
+    , sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile)
+    , system ? builtins.currentSystem
+    , pkgs ? mkPkgs sources system
+    }: rec {
+      # The sources, i.e. the attribute set of spec name to spec
+      inherit sources;
+
+      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
+      inherit pkgs;
+    };
+
+in
+mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }
diff --git a/pkgs.nix b/pkgs.nix
new file mode 100644
index 0000000..26bb456
--- /dev/null
+++ b/pkgs.nix
@@ -0,0 +1,22 @@
+{
+  sources ? import ./nix/sources.nix,
+  rustNightly ? "2020-11-10",
+}: let
+  pkgs = import sources.nixpkgs {
+    overlays = [
+      (import sources.nixpkgs-mozilla)
+      (self: super: let
+        rustChannel = super.rustChannelOf {
+          channel = "nightly";
+          date = rustNightly;
+        };
+      in rec {
+        rustc = rustChannel.rust.override {
+          extensions = [ "rust-src" ];
+        };
+        inherit (rustChannel) cargo rust-fmt rust-std clippy;
+        crate2nix = super.callPackage sources.crate2nix {};
+      })
+    ];
+  };
+in pkgs
diff --git a/shell.nix b/shell.nix
new file mode 100644
index 0000000..c3260a2
--- /dev/null
+++ b/shell.nix
@@ -0,0 +1,8 @@
+let
+  pkgs = import ./pkgs.nix {};
+in pkgs.mkShell {
+  buildInputs = with pkgs; [
+    #rust
+    crate2nix
+  ];
+}
diff --git a/test-shell.nix b/test-shell.nix
new file mode 100644
index 0000000..812d748
--- /dev/null
+++ b/test-shell.nix
@@ -0,0 +1,7 @@
+let
+  pkgs = import ./pkgs.nix {};
+in pkgs.mkShell {
+  buildInputs = with pkgs; [
+    (import ./Cargo.nix {}).rootCrate.build
+  ];
+}