error:
       … while calling anonymous lambda

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/attrsets.nix:816:24:

          815|     let f = attrPath:
          816|       zipAttrsWith (n: values:
             |                        ^
          817|         let here = attrPath ++ [n]; in

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:486:16:

          485|       # Run all the tests and code coverage
          486|       checks = removeRecurseForDerivations checks;
             |                ^
          487|       inherit

       … while calling 'removeRecurseForDerivations'

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:471:33:

          470|
          471|   removeRecurseForDerivations = x:
             |                                 ^
          472|     let clean = builtins.removeAttrs x ["recurseForDerivations"];

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:510:20:

          509|         , apps ? mkFlakeApps haskellPackages
          510|         , checks ? mkFlakeChecks (collectChecks' haskellPackages)
             |                    ^
          511|         , coverage ? {}

       … while calling 'mkFlakeChecks'

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:459:19:

          458|   # Flatten the result of collectChecks or collectChecks' for use in flake `checks`
          459|   mkFlakeChecks = allChecks:
             |                   ^
          460|     foldrAttrVals

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:460:5:

          459|   mkFlakeChecks = allChecks:
          460|     foldrAttrVals
             |     ^
          461|       (package: acc:

       … while calling 'foldrAttrVals'

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:37:25:

           36|
           37|   foldrAttrVals = f: z: attrs:
             |                         ^
           38|     lib.foldr f z (builtins.attrValues attrs);

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:38:5:

           37|   foldrAttrVals = f: z: attrs:
           38|     lib.foldr f z (builtins.attrValues attrs);
             |     ^
           39|

       … while calling 'foldr'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/lists.nix:53:20:

           52|   */
           53|   foldr = op: nul: list:
             |                    ^
           54|     let

       … from call site

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/lists.nix:60:8:

           59|         else op (elemAt list n) (fold' (n + 1));
           60|     in fold' 0;
             |        ^
           61|

       … while calling 'fold''

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/lists.nix:56:15:

           55|       len = length list;
           56|       fold' = n:
             |               ^
           57|         if n == len

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:469:8:

          468|       { }
          469|       (removeRecurseForDerivations allChecks);
             |        ^
          470|

       … while calling 'removeRecurseForDerivations'

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:471:33:

          470|
          471|   removeRecurseForDerivations = x:
             |                                 ^
          472|     let clean = builtins.removeAttrs x ["recurseForDerivations"];

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:510:35:

          509|         , apps ? mkFlakeApps haskellPackages
          510|         , checks ? mkFlakeChecks (collectChecks' haskellPackages)
             |                                   ^
          511|         , coverage ? {}

       … while calling 'collectChecks'

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:184:31:

          183|   # This can be used to collect all the test runs in your project, so that can be run in CI.
          184|   collectChecks = packageSel: haskellPackages:
             |                               ^
          185|     let packageFilter = name: package: (package.isHaskell or false) && packageSel package;

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:186:8:

          185|     let packageFilter = name: package: (package.isHaskell or false) && packageSel package;
          186|     in recurseIntoAttrs (lib.mapAttrs (_: p: p.checks) (lib.filterAttrs packageFilter haskellPackages));
             |        ^
          187|

       … while calling 'recurseIntoAttrs'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/attrsets.nix:1018:5:

         1017|     # An attribute set to scan for derivations.
         1018|     attrs:
             |     ^
         1019|     attrs // { recurseForDerivations = true; };

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:186:57:

          185|     let packageFilter = name: package: (package.isHaskell or false) && packageSel package;
          186|     in recurseIntoAttrs (lib.mapAttrs (_: p: p.checks) (lib.filterAttrs packageFilter haskellPackages));
             |                                                         ^
          187|

       … while calling 'filterAttrs'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/attrsets.nix:309:5:

          308|     # The attribute set to filter
          309|     set:
             |     ^
          310|     listToAttrs (concatMap (name: let v = set.${name}; in if pred name v then [(nameValuePair name v)] else []) (attrNames set));

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/default.nix:507:29:

          506|           selectPackages ? haskellLib.selectProjectPackages
          507|         , haskellPackages ? selectPackages project.hsPkgs
             |                             ^
          508|         , packages ? mkFlakePackages haskellPackages

       … while calling 'filterAttrs'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/attrsets.nix:309:5:

          308|     # The attribute set to filter
          309|     set:
             |     ^
          310|     listToAttrs (concatMap (name: let v = set.${name}; in if pred name v then [(nameValuePair name v)] else []) (attrNames set));

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/overlays/haskell.nix:658:27:

          657|               callProjectResults = callCabalProjectToNix config;
          658|               plan-pkgs = importAndFilterProject {
             |                           ^
          659|                 inherit (callProjectResults) projectNix sourceRepos src;

       … while calling anonymous lambda

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/import-and-filter-project.nix:5:1:

            4| { pkgs, haskellLib }:
            5| { projectNix, sourceRepos, src }:
             | ^
            6| let

       … while evaluating derivation 'cardano-cli-plan-to-nix-pkgs'
         whose name attribute is located at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/pkgs/stdenv/generic/make-derivation.nix:300:7

       … while evaluating attribute 'buildCommand' of derivation 'cardano-cli-plan-to-nix-pkgs'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/pkgs/build-support/trivial-builders/default.nix:87:14:

           86|       enableParallelBuilding = true;
           87|       inherit buildCommand name;
             |              ^
           88|       passAsFile = [ "buildCommand" ]

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/call-cabal-project-to-nix.nix:253:9:

          252|       '' +
          253|         pkgs.lib.optionalString (builtins.length sourceReposEval != 0) (''
             |         ^
          254|         chmod +w -R ./cabal.project

       … while calling 'optionalString'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/strings.nix:243:5:

          242|     # String to return if condition is true
          243|     string: if cond then string else "";
             |     ^
          244|

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/call-cabal-project-to-nix.nix:259:11:

          258|         # Add replacement `source-repository-package` blocks pointing to the minimal git repos
          259|         ( pkgs.lib.strings.concatMapStrings (f: ''
             |           ^
          260|               echo "source-repository-package" >> ./cabal.project

       … while calling 'concatMapStrings'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/lib/strings.nix:60:25:

           59|   */
           60|   concatMapStrings = f: list: concatStrings (map f list);
             |                         ^
           61|

       … while calling anonymous lambda

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/call-cabal-project-to-nix.nix:259:46:

          258|         # Add replacement `source-repository-package` blocks pointing to the minimal git repos
          259|         ( pkgs.lib.strings.concatMapStrings (f: ''
             |                                              ^
          260|               echo "source-repository-package" >> ./cabal.project

       … while evaluating derivation 'source-repository-package'
         whose name attribute is located at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/pkgs/stdenv/generic/make-derivation.nix:300:7

       … while evaluating attribute 'buildCommand' of derivation 'source-repository-package'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/pkgs/build-support/trivial-builders/default.nix:87:14:

           86|       enableParallelBuilding = true;
           87|       inherit buildCommand name;
             |              ^
           88|       passAsFile = [ "buildCommand" ]

       … from call site

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/call-cabal-project-to-nix.nix:207:56:

          206|               in __trace "WARNING: No sha256 found for source-repository-package ${repoData.url} ref=${repoData.ref or "(unspecified)"} rev=${repoData.rev or "(unspecified)"} download may fail in restricted mode (hydra)"
          207|                 (__trace "Consider adding `--sha256: ${hashPath drv}` to the ${cabalProjectFileName} file or passing in a sha256map argument"
             |                                                        ^
          208|                  drv);

       … while calling 'hashPath'

         at /nix/store/bdkxqq0n6h0jqxkxzhdnj9dccwvlw6cz-source/lib/call-cabal-project-to-nix.nix:182:14:

          181|
          182|   hashPath = path:
             |              ^
          183|     builtins.readFile (pkgs.runCommand "hash-path" { preferLocalBuild = true; }

       … while evaluating derivation 'hash-path'
         whose name attribute is located at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/pkgs/stdenv/generic/make-derivation.nix:300:7

       … while evaluating attribute 'buildCommand' of derivation 'hash-path'

         at /nix/store/75yg5df22m25b8pk2qmw843ydnbl0rsk-source/pkgs/build-support/trivial-builders/default.nix:87:14:

           86|       enableParallelBuilding = true;
           87|       inherit buildCommand name;
             |              ^
           88|       passAsFile = [ "buildCommand" ]

       error: fetchTree argument 'ref' is null while a string, Boolean or integer is expected