fixup! Provide hackage and stackage from haskell.nix

Author: rvl

default.nix

@@ -67,12 +67,14 @@ let
       }@args:
 
       let
+        # The Stackage release referenced in the stack config
+        pkg-def = stackage.${stack-pkgs.resolver};
         # The compiler referenced in the stack config
-        compiler = (stack-pkgs.overlay hackage).compiler.nix-name;
+        compiler = (stack-pkgs.overlay hackage).compiler or (pkg-def hackage).compiler;
       in self.mkPkgSet {
-        pkg-def = stackage.${stack-pkgs.resolver};
+        inherit pkg-def;
         pkg-def-overlays = [ stack-pkgs.overlay ] ++ pkg-def-overlays;
-        modules = [ ghcHackagePatches.${compiler} ] ++ modules;
+        modules = [ ghcHackagePatches.${compiler.nix-name} ] ++ modules;
       };
 
     # Programs for generating Nix expressions from Cabal and Stack