Implement the function.sent proposal.

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/hashmap.h"
@@ skipping 2568 matching lines @@
   // caller.
 
   // Parse the initial primary or function expression.
   ExpressionT result = this->EmptyExpression();
   if (peek() == Token::FUNCTION) {
     BindingPatternUnexpectedToken(classifier);
     ArrowFormalParametersUnexpectedToken(classifier);
 
     Consume(Token::FUNCTION);
     int function_token_position = position();
+
+    if (FLAG_harmony_function_sent && Check(Token::PERIOD)) {
+      // function.sent
+
+      int pos = position();
+      ExpectContextualKeyword(CStrVector("sent"), CHECK_OK);
+
+      if (!is_generator()) {

[rossberg, 2016/01/22 14:13:06]

This may not be good enough. Like other magic constants, function.sent is
probably intended to be accessible in nested arrow functions, e.g.

  function *g() { yield; return (() => function.sent))() }

I think it's fine to leave it like that for now, until there is a more detailed
spec, but at least add a TODO.

[neis, 2016/01/27 16:49:40]

Done.

+        ReportMessageAt(scanner()->location(),
+                        MessageTemplate::kUnexpectedFunctionSent);
+        *ok = false;
+        return this->EmptyExpression();
+      }
+
+      return this->FunctionSentExpression(scope_, factory(), pos);
+    }
+
     bool is_generator = Check(Token::MUL);
     IdentifierT name = this->EmptyIdentifier();
     bool is_strict_reserved_name = false;
     Scanner::Location function_name_location = Scanner::Location::invalid();
     FunctionLiteral::FunctionType function_type =
         FunctionLiteral::kAnonymousExpression;
     if (peek_any_identifier()) {
       name = ParseIdentifierOrStrictReservedWord(
           is_generator, &is_strict_reserved_name, CHECK_OK);
       function_name_location = scanner()->location();
@@ skipping 775 matching lines @@
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H