From 4daab99a09e33e9924c61322f7f6d742e18f5450 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 16 Aug 2017 12:48:39 -0400
Subject: [PATCH] Revert "Define eof in terms of state."

This reverts commit b71a285f23f1a7112173f03a2041bebaae637940.
---
 src/Data/Syntax/Assignment.hs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/Data/Syntax/Assignment.hs b/src/Data/Syntax/Assignment.hs
index 6c4a250ee..ba1e63bb5 100644
--- a/src/Data/Syntax/Assignment.hs
+++ b/src/Data/Syntax/Assignment.hs
@@ -131,6 +131,7 @@ type Assignment ast grammar = Freer (AssignmentF ast grammar)
 data AssignmentF ast grammar a where
   Get :: AssignmentF ast grammar (State ast grammar)
   Put :: State ast grammar -> AssignmentF ast grammar ()
+  End :: HasCallStack => AssignmentF ast grammar ()
   Source :: HasCallStack => AssignmentF ast grammar ByteString
   Children :: HasCallStack => Assignment ast grammar a -> AssignmentF ast grammar a
   Choose :: HasCallStack => [grammar] -> IntMap.IntMap a -> AssignmentF ast grammar a
@@ -264,6 +265,7 @@ runAssignment source = \ assignment state -> go assignment state >>= requireExha
                 anywhere node = case assignment of
                   Get -> yield state state
                   Put s -> yield () s
+                  End -> requireExhaustive ((), state) >>= uncurry yield
                   Many rule -> fix (\ recur state -> (go rule state >>= \ (a, state') -> first (a:) <$> if state == state' then pure ([], state') else recur state') `catchError` const (pure ([], state))) state >>= uncurry yield
                   Alt as -> sconcat (flip yield state <$> as)
                   Throw e -> Left (fromMaybe (makeError node) e)
@@ -350,7 +352,7 @@ instance (Eq grammar, Eq (ast (AST ast grammar))) => Alternative (Assignment ast
   many :: HasCallStack => Assignment ast grammar a -> Assignment ast grammar [a]
   many a = Many a `Then` return
 
-instance (Eq grammar, Symbol grammar, Eq (ast (AST ast grammar)), Show grammar, Show (ast (AST ast grammar))) => Parsing (Assignment ast grammar) where
+instance (Eq grammar, Eq (ast (AST ast grammar)), Show grammar, Show (ast (AST ast grammar))) => Parsing (Assignment ast grammar) where
   try :: HasCallStack => Assignment ast grammar a -> Assignment ast grammar a
   try = id
 
@@ -361,9 +363,7 @@ instance (Eq grammar, Symbol grammar, Eq (ast (AST ast grammar)), Show grammar,
   unexpected s = location >>= \ loc -> throwError (Error (Info.sourceSpan loc) [] (Just (Left s)))
 
   eof :: HasCallStack => Assignment ast grammar ()
-  eof = do
-    state <- get
-    guard (not (null (stateNodes (skipTokens state))))
+  eof = withFrozenCallStack $ End `Then` return
 
   notFollowedBy :: (HasCallStack, Show a) => Assignment ast grammar a -> Assignment ast grammar ()
   notFollowedBy a = a *> unexpected (show a) <|> pure ()
@@ -383,6 +383,7 @@ instance (Show grammar, Show (ast (AST ast grammar))) => Show1 (AssignmentF ast
   liftShowsPrec sp sl d a = case a of
     Get -> showString "Get"
     Put s -> showsUnaryWith showsPrec "Put" d s
+    End -> showString "End" . showChar ' ' . sp d ()
     Source -> showString "Source" . showChar ' ' . sp d ""
     Children a -> showsUnaryWith (liftShowsPrec sp sl) "Children" d a
     Choose symbols choices -> showsBinaryWith showsPrec (const (liftShowList sp sl)) "Choose" d symbols (IntMap.toList choices)