[es7] implement |do| expressions proposal

src/preparser.cc

 // Copyright 2011 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.
 
 #include <cmath>
 
 #include "src/allocation.h"
 #include "src/base/logging.h"
 #include "src/conversions-inl.h"
 #include "src/conversions.h"
@@ skipping 1221 matching lines @@
   Scanner::Location spread_pos;
   ExpressionClassifier classifier;
   ParseArguments(&spread_pos, &classifier, ok);
   ValidateExpression(&classifier, CHECK_OK);
 
   DCHECK(!spread_pos.IsValid());
 
   return Expression::Default();
 }
 
+
+PreParserExpression PreParser::ParseDoExpression(bool* ok) {
+  // AssignmentExpression ::
+  //     do '{' StatementList '}'
+  Expect(Token::DO, CHECK_OK);
+  Expect(Token::LBRACE, CHECK_OK);
+  Scope* block_scope = NewScope(scope_, BLOCK_SCOPE);
+  {
+    BlockState block_state(&scope_, block_scope);
+    while (peek() != Token::RBRACE) {
+      ParseStatementListItem(CHECK_OK);
+    }
+    Expect(Token::RBRACE, CHECK_OK);
+    return PreParserExpression::Default();
+  }
+}
+
 #undef CHECK_OK
 
 
 }  // namespace internal
 }  // namespace v8