Add support for multiple levels

Add a data structure, based on the zipper comonad, which provides
support for multiple levels, each of which is its own entity map. The
current level is provided by coreturn, which the `entities` lens has
been updated to use. Nothing currently supports going up or down levels
yet - that's coming next.

1 files changed, 3 insertions, 0 deletions

diff --git a/haskell-overlay.nix b/haskell-overlay.nix
index d3775316ad..fff1c21741 100644
--- a/haskell-overlay.nix
+++ b/haskell-overlay.nix
@@ -29,4 +29,7 @@ in self: super: with pkgs.haskell.lib; rec {
       };
       version = "0.12.0";
     };
+
+  comonad-extras = appendPatch (markUnbroken super.comonad-extras)
+    [ ./build/update-comonad-extras.patch ];
 }