From 4aeb7b1483f18c86c4c938edc3fd332d2ccaad42 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 19 Apr 2017 13:49:36 -0400
Subject: [PATCH] Represent the absence of optional syntax with the Empty
 constructor.

---
 src/Language/Ruby/Syntax.hs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Language/Ruby/Syntax.hs b/src/Language/Ruby/Syntax.hs
index 62fdaa1a6..ed7f65d08 100644
--- a/src/Language/Ruby/Syntax.hs
+++ b/src/Language/Ruby/Syntax.hs
@@ -29,6 +29,7 @@ type Syntax' =
   , Statement.If
   , Statement.Return
   , Statement.Yield
+  , Syntax.Empty
   , Syntax.Identifier
   , []
   ]
@@ -84,4 +85,4 @@ literal  =  term () Literal.true <$ symbol Language.Ruby.Syntax.True <* content
         <|> term () . Literal.Integer <$ symbol Language.Ruby.Syntax.Integer <*> content
 
 optional :: Assignment Grammar (Term Syntax ()) -> Assignment Grammar (Term Syntax ())
-optional a = a <|> pure (() `term` [])
+optional a = a <|> pure (() `term` Syntax.Empty)