Build against the latest dhall (#61)

This is to prepare ahead for an upcoming new release of `dhall`

nix/dhall.nix

@@ -1,7 +1,7 @@
 { mkDerivation, ansi-terminal, base, bytestring, case-insensitive
 , cborg, containers, contravariant, criterion, cryptonite, deepseq
-, Diff, directory, doctest, exceptions, filepath, hashable
-, haskeline, http-client, http-client-tls
+, Diff, directory, doctest, exceptions, fetchgit, filepath
+, hashable, haskeline, http-client, http-client-tls
 , insert-ordered-containers, lens-family-core, megaparsec, memory
 , mockery, mtl, optparse-applicative, parsers, prettyprinter
 , prettyprinter-ansi-terminal, QuickCheck, quickcheck-instances
@@ -12,7 +12,11 @@
 mkDerivation {
   pname = "dhall";
   version = "1.17.0";
-  sha256 = "a029fea856224a79f0b7cc56fbb5c566d0dfd1d915d214f682006cabf1274791";
+  src = fetchgit {
+    url = "https://github.com/dhall-lang/dhall-haskell.git";
+    sha256 = "0fj61llfr2sz8lh2xpryzp7q0ahgqbzgf72ppw34w5ibq5a6gd9l";
+    rev = "fedfa8e41ea8da32c2ee779ce65982544ed4800f";
+  };
   isLibrary = true;
   isExecutable = true;
   libraryHaskellDepends = [

nix/megaparsec.nix

@@ -0,0 +1,25 @@
+{ mkDerivation, base, bytestring, case-insensitive, containers
+, criterion, deepseq, hspec, hspec-expectations, mtl
+, parser-combinators, QuickCheck, scientific, stdenv, text
+, transformers, weigh
+}:
+mkDerivation {
+  pname = "megaparsec";
+  version = "7.0.1";
+  sha256 = "6bbb385ea8bfb5b112dca234257bed36c061c56fbb576edda1b858549a7fc02c";
+  libraryHaskellDepends = [
+    base bytestring case-insensitive containers deepseq mtl
+    parser-combinators scientific text transformers
+  ];
+  testHaskellDepends = [
+    base bytestring case-insensitive containers hspec
+    hspec-expectations mtl parser-combinators QuickCheck scientific
+    text transformers
+  ];
+  benchmarkHaskellDepends = [
+    base containers criterion deepseq text weigh
+  ];
+  homepage = "https://github.com/mrkkrp/megaparsec";
+  description = "Monadic parser combinators";
+  license = stdenv.lib.licenses.bsd2;
+}

nix/repline.nix

@@ -0,0 +1,11 @@
+{ mkDerivation, base, containers, haskeline, mtl, process, stdenv
+}:
+mkDerivation {
+  pname = "repline";
+  version = "0.2.0.0";
+  sha256 = "ecc72092d0340b896ee6bf96bf6645694dbcd33361725a2cd28c5ab5d60c02de";
+  libraryHaskellDepends = [ base containers haskeline mtl process ];
+  homepage = "https://github.com/sdiehl/repline";
+  description = "Haskeline wrapper for GHCi-like REPL interfaces";
+  license = stdenv.lib.licenses.mit;
+}

src/Dhall/JSON.hs

@@ -249,6 +249,11 @@ dhallToJSON e0 = loop (Dhall.Core.normalize e0)
         Dhall.Core.OptionalLit _ a -> do
             a' <- traverse loop a
             return (Data.Aeson.toJSON a')
+        Dhall.Core.Some a -> do
+            a' <- loop a
+            return (Data.Aeson.toJSON a')
+        Dhall.Core.App Dhall.Core.None _ -> do
+            return Data.Aeson.Null
         Dhall.Core.RecordLit a ->
             case toOrderedList a of
                 [   (   "contents"
@@ -594,6 +599,14 @@ convertToHomogeneousMaps (Conversion {..}) e0 = loop (Dhall.Core.normalize e0)
             a' =      loop a
             b' = fmap loop b
 
+        Dhall.Core.Some a ->
+            Dhall.Core.Some a'
+          where
+            a' = loop a
+
+        Dhall.Core.None ->
+            Dhall.Core.None
+
         Dhall.Core.OptionalFold ->
             Dhall.Core.OptionalFold