gn: Don't do an out-of-bound access if a file ends after 'else'

tools/gn/parser.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef TOOLS_GN_PARSER_H_
 #define TOOLS_GN_PARSER_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 93 matching lines @@
   bool IsStatementBreak(Token::Type token_type) const;
 
   bool LookAhead(Token::Type type);
   bool Match(Token::Type type);
   Token Consume(Token::Type type, const char* error_message);
   Token Consume(Token::Type* types,
                 size_t num_types,
                 const char* error_message);
   Token Consume();
 
+  // Call this only if !at_end().
   const Token& cur_token() const { return tokens_[cur_]; }
 
+  const Token& cur_or_last_token() const {
+    return at_end() ? tokens_[tokens_.size() - 1] : cur_token();
+  }
+
   bool done() const { return at_end() || has_error(); }
   bool at_end() const { return cur_ >= tokens_.size(); }
   bool has_error() const { return err_->has_error(); }
 
   std::vector<Token> tokens_;
   std::vector<Token> line_comment_tokens_;
   std::vector<Token> suffix_comment_tokens_;
 
   static ParserHelper expressions_[Token::NUM_TYPES];
 
   Err* err_;
 
   // Current index into the tokens.
   size_t cur_;
 
   FRIEND_TEST_ALL_PREFIXES(Parser, BinaryOp);
   FRIEND_TEST_ALL_PREFIXES(Parser, Block);
   FRIEND_TEST_ALL_PREFIXES(Parser, Condition);
   FRIEND_TEST_ALL_PREFIXES(Parser, Expression);
   FRIEND_TEST_ALL_PREFIXES(Parser, FunctionCall);
   FRIEND_TEST_ALL_PREFIXES(Parser, List);
   FRIEND_TEST_ALL_PREFIXES(Parser, ParenExpression);
   FRIEND_TEST_ALL_PREFIXES(Parser, UnaryOp);
 
   DISALLOW_COPY_AND_ASSIGN(Parser);
 };
 
 #endif  // TOOLS_GN_PARSER_H_