From 464a0e8dadd58764d42a9c5436607aa2a0daf707 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Sat, 15 Mar 2014 15:15:59 -0700
Subject: [PATCH] Clean up parser header further

---
 include/tree_sitter/parser.h  | 23 +++++++++++++----------
 include/tree_sitter/runtime.h |  2 +-
 spec/runtime/parser_spec.cc   |  2 +-
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/include/tree_sitter/parser.h b/include/tree_sitter/parser.h
index b979e2ee..b9d13915 100644
--- a/include/tree_sitter/parser.h
+++ b/include/tree_sitter/parser.h
@@ -254,7 +254,7 @@ typedef struct {
     ts_lexer lexer;
     ts_stack stack;
     ts_tree *lookahead;
-    ts_tree *previous_lookahead;
+    ts_tree *next_lookahead;
 } ts_lr_parser;
 
 static ts_lr_parser * ts_lr_parser_make() {
@@ -267,7 +267,7 @@ static ts_lr_parser * ts_lr_parser_make() {
 static void ts_lr_parser_reset(ts_lr_parser *parser) {
     ts_stack_shrink(&parser->stack, 0);
     parser->lookahead = NULL;
-    parser->previous_lookahead = NULL;
+    parser->next_lookahead = NULL;
     parser->lexer = ts_lexer_make();
 }
 
@@ -278,13 +278,13 @@ static ts_symbol ts_lr_parser_lookahead_sym(const ts_lr_parser *parser) {
 
 static void ts_lr_parser_shift(ts_lr_parser *parser, state_id parse_state) {
     ts_stack_push(&parser->stack, parse_state, parser->lookahead);
-    parser->lookahead = parser->previous_lookahead;
-    parser->previous_lookahead = NULL;
+    parser->lookahead = parser->next_lookahead;
+    parser->next_lookahead = NULL;
 }
 
 static void ts_lr_parser_reduce(ts_lr_parser *parser, ts_symbol symbol, int immediate_child_count, const int *collapse_flags) {
     ts_tree *lookahead = ts_stack_reduce(&parser->stack, symbol, immediate_child_count, collapse_flags);
-    parser->previous_lookahead = parser->lookahead;
+    parser->next_lookahead = parser->lookahead;
     parser->lookahead = lookahead;
 }
 
@@ -294,7 +294,15 @@ static int ts_lr_parser_handle_error(ts_lr_parser *parser, size_t count, const t
     for (;;) {
         ts_tree_release(parser->lookahead);
         parser->lookahead = ts_lex(&parser->lexer, ts_lex_state_error);
+        if (parser->lookahead->symbol == ts_builtin_sym_end) {
+            parser->stack.entries[0].node = error;
+            return 0;
+        }
 
+        /*
+         *  Unwind the stack, looking for a state in which this token
+         *  may appear after an error.
+         */
         for (long i = parser->stack.size - 1; i >= 0; i--) {
             size_t count;
             state_id to_state;
@@ -307,11 +315,6 @@ static int ts_lr_parser_handle_error(ts_lr_parser *parser, size_t count, const t
                 }
             }
         }
-
-        if (!ts_lexer_lookahead_char(&parser->lexer)) {
-            parser->stack.entries[0].node = error;
-            return 0;
-        }
     }
 }
 
diff --git a/include/tree_sitter/runtime.h b/include/tree_sitter/runtime.h
index c81dc9a0..21492e52 100644
--- a/include/tree_sitter/runtime.h
+++ b/include/tree_sitter/runtime.h
@@ -53,7 +53,7 @@ typedef struct {
         const char **symbol_names;
         void *data;
     } ts_parser;
-    
+
     const ts_tree * ts_parser_parse(ts_parser *, ts_input);
     void ts_parser_free(ts_parser *);
 
diff --git a/spec/runtime/parser_spec.cc b/spec/runtime/parser_spec.cc
index 32f2b09a..3b48bf11 100644
--- a/spec/runtime/parser_spec.cc
+++ b/spec/runtime/parser_spec.cc
@@ -2,7 +2,7 @@
 #include "helpers/spy_reader.h"
 
 extern "C" ts_parser ts_parser_json();
-    
+
 START_TEST
 
 describe("parsing", [&]() {