[parser] Refactor parser and preparser traits

src/parsing/parser-base.h

 // Copyright 2012 the V8 project 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 V8_PARSING_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/base/hashmap.h"
@@ skipping 108 matching lines @@
 
 
 // ----------------------------------------------------------------------------
 // The CHECK_OK macro is a convenient macro to enforce error
 // handling for functions that may fail (by returning !*ok).
 //
 // CAUTION: This macro appends extra statements after a call,
 // thus it must never be used where only a single statement
 // is correct (e.g. an if statement branch w/o braces)!
 
-#define CHECK_OK  ok);                      \
-  if (!*ok) return this->EmptyExpression(); \
-  ((void)0
-#define DUMMY )  // to make indentation work
-#undef DUMMY
-
-// Used in functions where the return type is not ExpressionT.
 #define CHECK_OK_CUSTOM(x) ok); \
   if (!*ok) return this->x();   \
   ((void)0
 #define DUMMY )  // to make indentation work
 #undef DUMMY
 
+// Used in functions where the return type is ExpressionT.
+#define CHECK_OK CHECK_OK_CUSTOM(EmptyExpression)
+
 
 // Common base class shared between parser and pre-parser. Traits encapsulate
 // the differences between Parser and PreParser:
 
 // - Return types: For example, Parser functions return Expression* and
 // PreParser functions return PreParserExpression.
 
 // - Creating parse tree nodes: Parser generates an AST during the recursive
 // descent. PreParser doesn't create a tree. Instead, it passes around minimal
 // data objects (PreParserExpression, PreParserIdentifier etc.) which contain
@@ skipping 3596 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H