cabal: stopping GHC 8.4 support

https://github.com/haskell-nix/hnix/issues/885

.github/workflows/Cabal-Linux.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ghc: [ "8.10", "8.4" ]
+        ghc: [ "8.10", "8.6" ]
     steps:
 
       - name: "Git checkout"

.github/workflows/On-Release-Cabal-Linux.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       matrix:
         # Since CI by default tests boundary GHCs, test middle versions of GHCs
-        ghc: [ "8.8", "8.6"]
+        ghc: [ "8.8" ]
     steps:
       - name: "Git checkout"
         uses: actions/checkout@v2

hnix.cabal

@@ -397,7 +397,7 @@ library
   build-depends:
       aeson >= 1.4.2 && < 1.6
     , array >= 0.4 && < 0.6
-    , base >= 4.11 && < 5
+    , base >= 4.12 && < 5
     , binary >= 0.8.5 && < 0.9
     , bytestring >= 0.10.8 && < 0.11
     , comonad >= 5.0.4 && < 5.1

src/Nix/Reduce.hs

@@ -40,7 +40,12 @@ import           Control.Monad.Fail
 import           Control.Monad.Fix
 import           Control.Monad.IO.Class
 import           Control.Monad.Reader
-import           Control.Monad.State.Strict
+import           Control.Monad.State.Strict     ( MonadState
+                                                , StateT
+                                                , gets
+                                                , modify
+                                                , evalStateT
+                                                )
 import           Data.Bifunctor                 ( first )
 import           Data.Fix                       ( Fix(..), foldFix, foldFixM )
 import           Data.HashMap.Lazy              ( HashMap )