experiments | ghc: well-typed/generics-sop#89

experiments/ghc/Main.hs

@@ -0,0 +1,41 @@
+{-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE QuantifiedConstraints #-}
+{-# LANGUAGE TypeInType #-}
+{-# LANGUAGE UndecidableSuperClasses #-}
+{-# LANGUAGE UnicodeSyntax #-}
+{-# OPTIONS_GHC -Wextra -Wno-unused-imports -Wno-unticked-promoted-constructors -Wno-type-defaults -Wno-missing-signatures #-}
+
+module Main where
+
+import           Control.Monad.IO.Class
+import qualified GHC.Generics as GHC
+import           Generics.SOP
+import qualified Generics.SOP as SOP
+
+
+class    ( GHC.Generic a, SOP.Generic a, HasDatatypeInfo a
+         , forall xs. Code a ~ '[xs]) => Foo m a where
+
+instance ( GHC.Generic a, SOP.Generic a, HasDatatypeInfo a
+         , forall xs. Code a ~ '[xs]
+         , Monad m)                  => Foo m a where
+
+-- error:
+--     • Could not deduce: Code a ~ '[xs]
+--         arising from the superclasses of an instance declaration
+--       from the context: (GHC.Generic a, HasDatatypeInfo a,
+--                          forall (xs :: [*]). Code a ~ '[xs], Monad m)
+--         bound by the instance declaration
+--         at /run/user/1000/danteazsW1Q.hs:(22,10)-(24,47)
+--     • In the instance declaration for ‘Foo m a’
+
+
+main ∷ IO ()
+main = do
+
+  putStrLn "You are standing at the end of a road before a small brick building."
+  putStrLn "Around you is a forest.  A small stream flows out of the building and"
+  putStrLn "down a gully."

experiments/ghc/default.nix

@@ -0,0 +1,17 @@
+{ mkDerivation, stdenv, base, cabal-install, generics-sop
+}:
+mkDerivation {
+  pname                 = "holotype";
+  version               = "0.0.1";
+  src                   = ./.;
+  isLibrary             = true;
+  isExecutable          = true;
+  libraryHaskellDepends = [
+    base
+    cabal-install
+    generics-sop
+  ];
+  description           = "Graph-backed visual mind assistant";
+  license               = stdenv.lib.licenses.agpl3;
+  doHaddock             = false;
+}

experiments/ghc/shell.nix

@@ -0,0 +1,19 @@
+{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc861", doBenchmark ? false }:
+
+let
+
+  inherit (nixpkgs) pkgs;
+
+  f = import ./default.nix;
+
+  haskellPackages = if compiler == "default"
+                       then pkgs.haskellPackages
+                       else pkgs.haskell.packages.${compiler};
+
+  variant = if doBenchmark then pkgs.haskell.lib.doBenchmark else pkgs.lib.id;
+
+  drv = variant (haskellPackages.callPackage f {});
+
+in
+
+  if pkgs.lib.inNixShell then drv.env else drv

holotype.cabal

@@ -309,3 +309,9 @@ executable lifted-record-holotree
   main-is:             Main.hs
   default-language:    Haskell2010
   build-depends:       base, base-unicode-symbols, containers, lens, TypeCompose
+
+executable ghc
+  hs-source-dirs:      experiments/ghc
+  main-is:             Main.hs
+  default-language:    Haskell2010
+  build-depends:       base, base-unicode-symbols, containers, generics-sop, lens, TypeCompose