basic enum example

This is partly with a view to eventually abstracting away much of the boilerplate.

flake.nix

@@ -13,20 +13,70 @@
     };
   };
   outputs =
-    inputs@{ nix-haskell, ... }:
+    inputs:
     inputs.flake-utils.lib.eachSystem [ "x86_64-linux" ] (system:
     let
       pkgs = (import inputs.nixpkgs { inherit system; }).extend (import inputs.rust-overlay);
-      nix-haskell = import inputs.nix-haskell { inherit system inputs; };
       crane = (inputs.crane.mkLib pkgs).overrideToolchain (p: p.rust-bin.selectLatestNightlyWith (
         toolchain: toolchain.default.override {
-          extensions = [ "rust-src" ];
+          extensions = [ "rust-src" "rust-analyzer" ];
           targets = [ "x86_64-unknown-linux-gnu" ];
         }
       ));
-      project =
+      addLibcIncludeDir =
-        (nix-haskell (import ./project.nix { inherit (inputs) hls-src hs-bindgen-src libclang-src; inherit garnet-rs; })
+        ''
-        ).project.haskell-nix;
+          export C_INCLUDE_PATH="${pkgs.stdenv.cc.libc.dev}/include''${C_INCLUDE_PATH:+:$C_INCLUDE_PATH}"
+        '';
+      project = (import inputs.nix-haskell { inherit system inputs; } {
+        name = "garnet";
+        src = ./.;
+        compiler-nix-name = "ghc914";
+        source-repository-packages = {
+          # not on Hackage yet: https://well-typed.com/blog/2026/02/hs-bindgen-alpha
+          # we're using more recent versions than in that post, because we want record-dot support:
+          # https://github.com/well-typed/hs-bindgen/issues/1829#issuecomment-4081875451
+          c-expr-dsl = inputs.hs-bindgen-src + "/c-expr-dsl";
+          c-expr-runtime = inputs.hs-bindgen-src + "/c-expr-runtime";
+          hs-bindgen = inputs.hs-bindgen-src + "/hs-bindgen";
+          hs-bindgen-runtime = inputs.hs-bindgen-src + "/hs-bindgen-runtime";
+          libclang-bindings = inputs.libclang-src;
+        };
+        overrides = [
+          ({ pkgs, ... }: {
+            packages.libclang-bindings.components.library = {
+              build-tools = [ pkgs.llvmPackages.llvm ];
+              libs = [ pkgs.llvmPackages.libclang ];
+            };
+            packages.garnet.components.library = {
+              preBuild = addLibcIncludeDir;
+              preConfigure = ''
+                mkdir -p rust/target/debug
+                ln -s ${garnet-rs}/include/garnet_rs.h rust/target/debug/garnet_rs.h
+              '';
+              preInstall = ''
+                cp ${garnet-rs}/lib/libCgarnet_rs.a dist/build/libCgarnet_rs.a
+              '';
+              configureFlags = [ "--extra-lib-dirs=${garnet-rs}/lib" ];
+            };
+          })
+        ];
+        shell = {
+          tools = {
+            cabal = "latest";
+            haskell-language-server = {
+              src = inputs.hls-src;
+              sha256map = {
+                "https://github.com/snowleopard/alga" = {
+                  "d4e43fb42db05413459fb2df493361d5a666588a" = "0s1mlnl64wj7pkg3iipv5bb4syy3bhxwqzqv93zqlvkyfn64015i";
+                };
+              };
+            };
+          };
+          withHoogle = false;
+          withHaddock = true;
+          shellHook = addLibcIncludeDir;
+        };
+      }).project.haskell-nix;
       garnet-rs = crane.buildPackage {
         src = crane.cleanCargoSource ./rust;
         doCheck = false;
@@ -52,7 +102,6 @@
         packages = with pkgs; [
           bacon
           ghcid
-          rust-analyzer
         ];
       };
     });

garnet.cabal

@@ -29,6 +29,7 @@ common common
         NoMonomorphismRestriction
         OverloadedRecordDot
         OverloadedStrings
+        PatternSynonyms
         RecordWildCards
         ViewPatterns
     ghc-options:

lib/GarnetRs/Raw.hs

@@ -29,18 +29,9 @@ import HsBindgen.TH
 import Language.Haskell.TH
 import System.Process
 
-do
-    systemDirs <- -- TODO bit of a hack
-        map (Dir . T.unpack . T.strip)
-            . concatMap (takeWhile (maybe False ((== ' ') . fst) . T.uncons) . dropWhile T.null . T.lines)
-            . drop 1
-            . T.splitOn "search starts here:"
-            . T.pack
-            . thd3
-            <$> runIO (readProcessWithExitCode "cpp" ["-v"] "")
 withHsBindgen
     def
-            { clang = def{extraIncludeDirs = Pkg "rust/target/debug" : systemDirs}
+        { clang = def{extraIncludeDirs = [Pkg "rust/target/debug"]}
         , fieldNamingStrategy = OmitFieldPrefixes
         }
     def

lib/GarnetRs/Wrapped.hs

@@ -1,5 +1,3 @@
-{-# LANGUAGE PatternSynonyms #-}
-
 -- TODO automate this sort of high level wrapper boilerplate
 -- or look at upstream plans: https://github.com/well-typed/hs-bindgen/issues?q=state%3Aopen%20label%3A%22highlevel%22
 module GarnetRs.Wrapped (
@@ -66,27 +64,27 @@ withBTree =
                 Raw.Fork_Body (unsafeFromPtr lPtr) (unsafeFromPtr rPtr)
 
 hello :: ByteString -> IO ()
-hello = flip useAsCString $ Raw.hello . unsafeFromPtr
+hello bs = useAsCString bs \ptr -> Raw.hello $ unsafeFromPtr ptr
 
 helloStruct :: T -> IO ()
-helloStruct = flip with (Raw.hello_struct . unsafeFromPtr) . convertT
+helloStruct t = with (convertT t) \ptr -> Raw.hello_struct $ unsafeFromPtr ptr
 
 helloEnum :: Raw.E -> IO ()
-helloEnum = flip with (Raw.hello_enum . unsafeFromPtr)
+helloEnum e = with e \ptr -> Raw.hello_enum $ unsafeFromPtr ptr
 
 helloShape :: Shape -> IO ()
-helloShape = flip with (Raw.hello_shape . unsafeFromPtr) . convertShape
+helloShape s = with (convertShape s) \ptr -> Raw.hello_shape $ unsafeFromPtr ptr
 
 add :: Int64 -> Int64 -> Int64
 add = Raw.add
 
 sumTree :: BTree Int64 -> Int64
-sumTree = unsafePerformIO . flip withBTree (flip with $ Raw.sum_tree . unsafeFromPtr)
+sumTree t = unsafePerformIO $ withBTree t \tc -> with tc \ptr -> Raw.sum_tree $ unsafeFromPtr ptr
 
 sumSlice :: V.Vector Int64 -> Int64
-sumSlice v = unsafePerformIO $ V.unsafeWith v \p -> Raw.sum_slice (unsafeFromPtr p) (fromIntegral $ V.length v)
+sumSlice v = unsafePerformIO $ V.unsafeWith v \ptr -> Raw.sum_slice (unsafeFromPtr ptr) (fromIntegral $ V.length v)
 
 printOptional :: Maybe Int8 -> IO ()
 printOptional = \case
-    Nothing -> Raw.print_optional (unsafeFromPtr nullPtr)
+    Nothing -> Raw.print_optional $ unsafeFromPtr nullPtr
-    Just t -> with t (Raw.print_optional . unsafeFromPtr)
+    Just t -> with t \ptr -> Raw.print_optional $ unsafeFromPtr ptr

project.nix

@@ -1,54 +0,0 @@
-{ hls-src
-, hs-bindgen-src
-, libclang-src
-, garnet-rs
-}:
-{
-  name = "garnet";
-  src = ./.;
-  compiler-nix-name = "ghc914";
-  source-repository-packages = {
-    # not on Hackage yet: https://well-typed.com/blog/2026/02/hs-bindgen-alpha
-    # we're using more recent versions than in that post, because we want record-dot support:
-    # https://github.com/well-typed/hs-bindgen/issues/1829#issuecomment-4081875451
-    c-expr-dsl = hs-bindgen-src + "/c-expr-dsl";
-    c-expr-runtime = hs-bindgen-src + "/c-expr-runtime";
-    hs-bindgen = hs-bindgen-src + "/hs-bindgen";
-    hs-bindgen-runtime = hs-bindgen-src + "/hs-bindgen-runtime";
-    libclang-bindings = libclang-src;
-  };
-  overrides = [
-    ({ pkgs, ... }: {
-      packages.libclang-bindings.components.library = {
-        build-tools = [ pkgs.llvmPackages.llvm ];
-        libs = [ pkgs.llvmPackages.libclang ];
-      };
-    })
-    (_: {
-      packages.garnet.components.library = {
-        preConfigure = ''
-          mkdir -p rust/target/debug
-          ln -s ${garnet-rs}/include/garnet_rs.h rust/target/debug/garnet_rs.h
-          ln -s ${garnet-rs}/lib/libCgarnet_rs.a rust/target/debug/libCgarnet_rs.a
-        '';
-        preInstall = ''
-          cp ${garnet-rs}/lib/libCgarnet_rs.a dist/build/libCgarnet_rs.a
-        '';
-        configureFlags = [ "--extra-lib-dirs=${garnet-rs}/lib" ];
-      };
-    })
-  ];
-  shell = {
-    tools = {
-      cabal = "latest";
-      haskell-language-server = {
-        src = hls-src;
-        sha256map = {
-          "https://github.com/snowleopard/alga"."d4e43fb42db05413459fb2df493361d5a666588a" = "0s1mlnl64wj7pkg3iipv5bb4syy3bhxwqzqv93zqlvkyfn64015i";
-        };
-      };
-    };
-    withHoogle = false;
-    withHaddock = true;
-  };
-}

rust/lib.rs

@@ -11,7 +11,7 @@ fn say_hello(name: &str) {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello(c: *const c_char) -> () {
+extern "C" fn hello(c: *const c_char) {
     say_hello(unsafe { CStr::from_ptr(c) }.to_str().unwrap())
 }
 
@@ -23,7 +23,7 @@ struct T {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello_struct(t: &T) -> () {
+extern "C" fn hello_struct(t: &T) {
     say_hello(&format!("{:?}", t))
 }
 
@@ -48,7 +48,7 @@ enum Shape {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello_shape(s: &Shape) -> () {
+extern "C" fn hello_shape(s: &Shape) {
     say_hello(&format!("{:?}", s))
 }