Only use compact with GHC 8.2, as per the documentation for compact

default.nix

@@ -1,4 +1,4 @@
-{ compiler    ? "ghc822" # "ghc842" also works
+{ compiler    ? "ghc822"
 , doProfiling ? false
 , doBenchmark ? false
 , doTracing   ? false
@@ -11,8 +11,6 @@
     config.allowUnfree = true;
     config.allowBroken = false;
   }
-# , nixpkgs     ? import ((import <nixpkgs> {}).fetchFromGitHub {
-#     owner = "NixOS"; repo = "nixpkgs"; inherit rev sha256; }) {
 }:
 
 let inherit (nixpkgs) pkgs;
@@ -27,16 +25,6 @@ let inherit (nixpkgs) pkgs;
         cryptohash-sha512 = doJailbreak super.cryptohash-sha512;
         serialise         = dontCheck super.serialise;
 
-        compact =
-          if compiler == "ghc842"
-          then doJailbreak super.compact
-          else super.compact;
-
-        ghc-compact =
-          if compiler == "ghc802"
-          then super.ghc-compact_0_1_0_0
-          else null;
-
         ghc-datasize =
           if doProfiling
           then null

hnix.cabal

@@ -2,7 +2,7 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 339a47c09afbfb01628bdac8a438e325c3abeec0f6abe983c634c15eafe94fc3
+-- hash: 811d6e9cc2046442e375ad2773d8a96490f8f823e10ef44e726aec59374287bf
 
 name:           hnix
 version:        0.5.1
@@ -529,7 +529,7 @@ library
     ghc-options: -fexpose-all-unfoldings -fspecialise-aggressively -O2
   if flag(tracing)
     cpp-options: -DENABLE_TRACING=1
-  if os(linux)
+  if os(linux) && impl(ghc >= 8.2) && impl(ghc < 8.3)
     build-depends:
         compact
   if !impl(ghcjs)
@@ -597,7 +597,7 @@ executable hnix
     ghc-options: -fexpose-all-unfoldings -fspecialise-aggressively -O2
   if flag(tracing)
     cpp-options: -DENABLE_TRACING=1
-  if os(linux)
+  if os(linux) && impl(ghc >= 8.2) && impl(ghc < 8.3)
     build-depends:
         compact
   if !impl(ghcjs)
@@ -666,7 +666,7 @@ test-suite hnix-tests
     ghc-options: -fexpose-all-unfoldings -fspecialise-aggressively -O2
   if flag(tracing)
     cpp-options: -DENABLE_TRACING=1
-  if os(linux)
+  if os(linux) && impl(ghc >= 8.2) && impl(ghc < 8.3)
     build-depends:
         compact
   if !impl(ghcjs)
@@ -715,7 +715,7 @@ benchmark hnix-benchmarks
     ghc-options: -fexpose-all-unfoldings -fspecialise-aggressively -O2
   if flag(tracing)
     cpp-options: -DENABLE_TRACING=1
-  if os(linux)
+  if os(linux) && impl(ghc >= 8.2) && impl(ghc < 8.3)
     build-depends:
         compact
   if !impl(ghcjs)

package.yaml

@@ -81,7 +81,7 @@ when:
   - condition: flag(tracing)
     cpp-options: -DENABLE_TRACING=1
 
-  - condition: os(linux)
+  - condition: "os(linux) && impl(ghc >= 8.2) && impl(ghc < 8.3)"
     dependencies:
       - compact