Add DerivingVia newtype for generic arbitrary

Add a newtype, GenericArbitrary, which can be used with -XDerivingVia to
derive Arbitrary instances for types with Generic, via patching
generic-arbitrary to expose the underlying typeclass it uses for
surfacing the type information.

1 files changed, 5 insertions, 2 deletions

diff --git a/default.nix b/default.nix
index 7cf9f4beb451..ca163c8e56d7 100644
--- a/default.nix
+++ b/default.nix
@@ -1,8 +1,11 @@
-{ nixpkgs ? import ./nixpkgs.nix {}, compiler ? "ghc865" }:
+{ nixpkgs ? import ./nixpkgs.nix {}
+, compiler ? "ghc865" }:
 let
   inherit (nixpkgs) pkgs;
   all-hies = import (fetchTarball "https://github.com/infinisil/all-hies/tarball/master") {};
   hie = all-hies.selection { selector = p: { inherit (p) ghc865; }; };
-  xanthous = pkgs.haskellPackages.callPackage (import ./pkg.nix { inherit nixpkgs; }) {};
+  xanthous = (pkgs.haskellPackages
+    .extend (import ./haskell-overlay.nix { inherit nixpkgs; }))
+    .callPackage (import ./pkg.nix { inherit nixpkgs; }) {};
 in
 xanthous // { inherit hie; }