Add nix dev shell

Author: kleinreact

finite.cabal

@@ -1,5 +1,5 @@
 name:                finite
-version:             1.4.1.3
+version:             1.4.1.4
 synopsis:            Finite ranges via types
 description:         A framework for capturing finite ranges with
                      types, where the sizes of the ranges are not

flake.lock

@@ -0,0 +1,58 @@
+{
+  description = "Nix flake for the finite package";
+
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = { self, nixpkgs, flake-utils } :
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+
+        ghcVersions = [ "ghc910" "ghc9121" ];
+        defaultGhcVersion = "ghc9121";
+
+        makeOverlay = compilerVersion:
+          let
+            overrideFile = ./. + "/nix/override-${compilerVersion}.nix";
+
+            overrides =
+              if builtins.pathExists overrideFile then
+                import overrideFile { inherit pkgs; }
+              else
+                f: p: { };
+
+            hsOverlay =
+              pkgs.haskell.packages.${compilerVersion}.override {
+                inherit overrides;
+              };
+
+            pkgSrcOverrides = pkgs.haskell.lib.compose.packageSourceOverrides {
+              finite = ./.;
+            };
+          in
+            hsOverlay.extend pkgSrcOverrides;
+
+        overlays = nixpkgs.lib.attrsets.genAttrs ghcVersions makeOverlay;
+
+        makeDevShell = compilerVersion:
+          with overlays.${compilerVersion};
+          shellFor {
+            name = compilerVersion;
+            packages = p: [
+              # project packages
+              p.finite
+            ];
+            nativeBuildInputs = [
+              # Haskell dependencies
+              # cabal-install
+            ];
+          };
+
+        shells = pkgs.lib.attrsets.genAttrs ghcVersions makeDevShell;
+      in {
+        devShells = shells // { default = shells.${defaultGhcVersion}; };
+      });
+}