diff --git a/colorless.cabal b/colorless.cabal
--- a/colorless.cabal
+++ b/colorless.cabal
@@ -3,7 +3,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           colorless
-version:        2.2.2
+version:        2.2.3
 synopsis:       Colorless
 description:    Colorless
 category:       Web
diff --git a/library/Colorless/Ast.hs b/library/Colorless/Ast.hs
--- a/library/Colorless/Ast.hs
+++ b/library/Colorless/Ast.hs
@@ -102,6 +102,17 @@
   Number a -> Ast'Const (Const'Number a)
   _ -> error "should never reach here"
 
+instance ToAst a => ToAst [a] where
+  toAst xs = Ast'List $ List $ map toAst xs
+
+instance ToAst a => ToAst (Maybe a) where
+  toAst Nothing = Ast'Const Const'Null
+  toAst (Just x) = toAst x
+
+instance (ToAst a, ToAst b) => ToAst (Either a b) where
+  toAst (Left a) = Ast'Enumeral $ Enumeral "Left" $ Just $ Map.fromList [("left", toAst a)]
+  toAst (Right a) = Ast'Enumeral $ Enumeral "Right" $ Just $ Map.fromList [("right", toAst a)]
+
 --
 
 instance (ToAst t1, ToAst t2) => ToAst (t1, t2) where
diff --git a/library/Colorless/Types.hs b/library/Colorless/Types.hs
--- a/library/Colorless/Types.hs
+++ b/library/Colorless/Types.hs
@@ -3,6 +3,7 @@
   ( Version(..)
   , Major(..)
   , Minor(..)
+  , Pull(..)
   , Request(..)
   , Response(..)
   , ResponseError(..)
@@ -42,6 +43,13 @@
 
 instance FromJSON Minor
 instance ToJSON Minor
+
+data Pull = Pull
+  { protocol :: Text
+  , address :: Text
+  , path :: Text
+  , port :: Int
+  } deriving (Show, Eq)
 
 data Version = Version
   { major :: Major
diff --git a/package.yaml b/package.yaml
--- a/package.yaml
+++ b/package.yaml
@@ -1,5 +1,5 @@
 name: colorless
-version: '2.2.2'
+version: '2.2.3'
 category: Web
 synopsis: Colorless
 description: Colorless