fix mkSnapshot

Author: Travis Whitaker

overlays/haskell.nix

@@ -165,7 +165,11 @@ final: prev: {
             };
 
         # Package sets for all stackage snapshots.
-        snapshots = import ../snapshots.nix { inherit (final) lib ghc-boot-packages; inherit mkPkgSet stackage excludeBootPackages; };
+        snapshots = import ../snapshots.nix {
+          inherit (final) lib ghc-boot-packages;
+          inherit mkPkgSet stackage excludeBootPackages;
+          hackage = hackageForStack;
+        };
         # Pick a recent LTS snapshot to be our "default" package set.
         haskellPackages =
             if final.stdenv.targetPlatform.isAarch64 && final.stdenv.buildPlatform.isAarch64

snapshots.nix

@@ -6,12 +6,13 @@
 # A particular package in a snapshot would be accessed with:
 #   snapshots."lts-13.18".conduit
 
-{ lib, mkPkgSet, stackage, excludeBootPackages, ghc-boot-packages }:
+{ lib, mkPkgSet, stackage, excludeBootPackages, ghc-boot-packages, hackage }:
 
 with lib;
 
 let
   mkSnapshot = name: pkg-def: (let pkgSet = mkPkgSet {
+    inherit hackage;
     pkg-def = excludeBootPackages null pkg-def;
     # ghc-boot-packages are needed for the reinstallable ghc library and
     # are constructed from the patched ghc source.