cabal2nix evaluation failures

Here's the reproduction:

```nix
let
compiler = "ghc865";

nixpkgs = builtins.fetchTarball {
url = "https://github.com/nh2/nixpkgs/archive/11aa987ea5b5a593c9ca7a38b391804959f905e5.tar.gz";
sha256 = "1wns6051fxpgmszyxjvk7020zzhljjxqxkrnqmyd3b6fah7q4vny";
};

static-haskell-nix = builtins.fetchTarball {
url = "https://github.com/nh2/static-haskell-nix/archive/d24dea3d46a727e1cd93e67458ce2768109efe0a.tar.gz";

sha256 = "0ri4r77md77kmbqmx0j3h0paj538zpq4hki7vy8ycpwssm2xd442";
};

overlay = pkgsNew: pkgsOld: {
haskell = pkgsOld.haskell // {
packages = pkgsOld.haskell.packages // {
"${compiler}" = pkgsOld.haskell.packages."${compiler}".override (old: {
overrides = pkgsNew.haskell.lib.packageSourceOverrides {
dhall = "1.27";
};
}
);
};
};
};

normalPkgs = import nixpkgs {
system = "x86_64-linux";

config = { };

overlays = [ overlay ];
};

staticHaskell = import "${static-haskell-nix}/survey/default.nix" {
inherit compiler normalPkgs;
};

in
staticHaskell.all.dhall
```

Here's the evaluation failure:

```
$ nix build --file ./minimal.nix --show-trace
error: while evaluating the file '/root/dhall-haskell/minimal.nix':
while evaluating the attribute 'all.dhall' at /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:1263:32:
while evaluating the attribute 'dhall' at undefined position:
while evaluating anonymous function at /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:1245:35, called from undefined position:
while evaluating 'isProperHaskellPackage' at /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:84:28, called from /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:1246:15:
while evaluating 'isDerivation' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/attrsets.nix:305:18, called from /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:85:5:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/lib.nix:48:54, called from undefined position:
while evaluating 'callPackageKeepDeriver' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:157:33, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/lib.nix:53:10:
while evaluating 'overrideCabal' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/lib.nix:37:24, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:158:5:
while evaluating 'callPackage' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:114:22, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:158:20:
while evaluating 'callPackageWithScope' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:74:37, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:114:28:
while evaluating 'makeOverridable' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:67:24, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:97:8:
while evaluating 'drvScope' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:87:18, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:69:12:
while evaluating the attribute 'nativeBuildInputs' of the derivation 'cabal2nix-dhall-1.27' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:126:7:
while evaluating 'getOutput' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/attrsets.nix:464:23, called from undefined position:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/stdenv/generic/make-derivation.nix:133:17, called from undefined position:
while evaluating the attribute 'cabal2nix' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:1262:3:
while evaluating 'overrideCabal' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/lib.nix:37:24, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:1262:15:
while evaluating 'override' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:73:20, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/lib.nix:37:28:
while evaluating 'makeOverridable' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:67:24, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:73:29:
while evaluating 'drvScope' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:87:18, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:69:12:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/hackage-packages.nix:45954:6, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/make-package-set.nix:87:27:
while evaluating 'mkDerivation' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/lib.nix:38:20, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/hackage-packages.nix:45960:6:
while evaluating 'override' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:73:20, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/lib.nix:38:25:
while evaluating 'makeOverridable' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:67:24, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:73:29:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/generic-builder.nix:12:1, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:69:12:
while evaluating 'fix' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/fixed-points.nix:19:9, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/generic-builder.nix:240:4:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/generic-builder.nix:240:20, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/fixed-points.nix:19:20:
while evaluating 'optionalAttrs' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/attrsets.nix:331:25, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/development/haskell-modules/generic-builder.nix:511:4:
while evaluating the attribute 'configureFlags' of the derivation 'nix-2.3.1' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/tools/package-management/nix/default.nix:28:14:
while evaluating the attribute 'configurePhase' of the derivation 'busybox-1.30.1-x86_64-unknown-linux-musl' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/stdenv/generic/make-derivation.nix:197:11:
while evaluating the attribute 'cc.targetPrefix' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/stdenv/generic/default.nix:148:14:
while evaluating the attribute 'gcc' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:7605:3:
while evaluating 'addMetaAttrs' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/meta.nix:15:28, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:7765:10:
while evaluating 'wrapCC' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:8625:12, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:7765:19:
while evaluating 'wrapCCWith' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:8604:5, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:8625:16:
while evaluating 'callPackageWith' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:108:35, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/top-level/all-packages.nix:8613:7:
while evaluating 'makeOverridable' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:67:24, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:112:8:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/build-support/cc-wrapper/default.nix:8:1, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:69:12:
while evaluating the attribute 'patches' of the derivation 'musl-1.1.22-x86_64-unknown-linux-musl' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/stdenv/generic/make-derivation.nix:197:11:
while evaluating the attribute 'nativeBuildInputs' of the derivation '300-relative.patch' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/build-support/fetchurl/default.nix:119:3:
while evaluating 'getOutput' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/attrsets.nix:464:23, called from undefined position:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/stdenv/generic/make-derivation.nix:133:17, called from undefined position:
while evaluating 'override' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:73:20, called from /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:697:14:
while evaluating 'makeOverridable' at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:67:24, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:73:29:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:77:28, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:69:12:
while evaluating anonymous function at /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/pkgs/tools/networking/curl/default.nix:1:1, called from /nix/store/7fjx5cza1ijdf6bsnchqn8g5zd0hza33-source/lib/customisation.nix:77:35:
while evaluating 'statify_zlib' at /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:459:18, called from /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:697:41:
attribute 'override' missing, at /nix/store/2yha1cvdl0d3l9p8zv00qhnbrkfx41fr-source/survey/default.nix:460:6
```

I believe this is not the same thing as #9 since that is a build failure whereas this is an evaluation failure.