[async-iteration] add support for for-await-of loops in Async Functions

src/parsing/parser.cc

 // 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.
 
 #include "src/parsing/parser.h"
 
 #include <memory>
 
 #include "src/api.h"
 #include "src/ast/ast-expression-rewriter.h"
@@ skipping 535 matching lines @@
                 info->extension() == nullptr && can_compile_lazily;
   set_allow_natives(FLAG_allow_natives_syntax || info->is_native());
   set_allow_tailcalls(FLAG_harmony_tailcalls && !info->is_native() &&
                       info->isolate()->is_tail_call_elimination_enabled());
   set_allow_harmony_do_expressions(FLAG_harmony_do_expressions);
   set_allow_harmony_function_sent(FLAG_harmony_function_sent);
   set_allow_harmony_restrictive_generators(FLAG_harmony_restrictive_generators);
   set_allow_harmony_trailing_commas(FLAG_harmony_trailing_commas);
   set_allow_harmony_class_fields(FLAG_harmony_class_fields);
   set_allow_harmony_object_rest_spread(FLAG_harmony_object_rest_spread);
+  set_allow_harmony_async_iteration(FLAG_harmony_async_iteration);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
     use_counts_[feature] = 0;
   }
   if (info->ast_value_factory() == NULL) {
     // info takes ownership of AstValueFactory.
     info->set_ast_value_factory(new AstValueFactory(
         zone(), info->isolate()->ast_string_constants(), info->hash_seed()));
     info->set_ast_value_factory_owned();
     ast_value_factory_ = info->ast_value_factory();
@@ skipping 1182 matching lines @@
     DCHECK_NOT_NULL(catch_info.variable);
     return factory()->NewTryCatchStatement(
         try_block, catch_info.scope, catch_info.variable, catch_block, pos);
   } else {
     DCHECK_NOT_NULL(finally_block);
     return factory()->NewTryFinallyStatement(try_block, finally_block, pos);
   }
 }
 
 // !%_IsJSReceiver(result = iterator.next()) &&
 //     %ThrowIteratorResultNotAnObject(result)

[neis, 2017/01/20 14:38:15]

Comment needs an update.

 Expression* Parser::BuildIteratorNextResult(Expression* iterator,
-                                            Variable* result, int pos) {
+                                            Variable* result, IteratorType type,
+                                            int pos) {
   Expression* next_literal = factory()->NewStringLiteral(
       ast_value_factory()->next_string(), kNoSourcePosition);
   Expression* next_property =
       factory()->NewProperty(iterator, next_literal, kNoSourcePosition);
   ZoneList<Expression*>* next_arguments =
       new (zone()) ZoneList<Expression*>(0, zone());
   Expression* next_call =
       factory()->NewCall(next_property, next_arguments, pos);
+  if (type == IteratorType::kAsync) {
+    next_call = RewriteAwaitExpression(next_call, pos);
+  }
   Expression* result_proxy = factory()->NewVariableProxy(result);
   Expression* left =
       factory()->NewAssignment(Token::ASSIGN, result_proxy, next_call, pos);
 
   // %_IsJSReceiver(...)
   ZoneList<Expression*>* is_spec_object_args =
       new (zone()) ZoneList<Expression*>(1, zone());
   is_spec_object_args->Add(left, zone());
   Expression* is_spec_object_call = factory()->NewCallRuntime(
       Runtime::kInlineIsJSReceiver, is_spec_object_args, pos);
@@ skipping 185 matching lines @@
   // If finalize is true, also instrument the loop with code that performs the
   // proper ES6 iterator finalization.  In that case, the result is not
   // immediately a ForOfStatement.
 
   const int nopos = kNoSourcePosition;
   auto avfactory = ast_value_factory();
 
   Variable* iterator = NewTemporary(avfactory->dot_iterator_string());
   Variable* result = NewTemporary(avfactory->dot_result_string());
   Variable* completion = NewTemporary(avfactory->empty_string());
 

[neis, 2017/01/20 14:38:15]

Comment needs an update.

   // iterator = GetIterator(iterable)
   Expression* assign_iterator;
   {
     assign_iterator = factory()->NewAssignment(
         Token::ASSIGN, factory()->NewVariableProxy(iterator),
-        factory()->NewGetIterator(iterable, iterable->position()),
+        factory()->NewGetIterator(iterable, GetIterator::kNormal,
+                                  iterable->position()),
         iterable->position());
   }
 
   // !%_IsJSReceiver(result = iterator.next()) &&
   //     %ThrowIteratorResultNotAnObject(result)
   Expression* next_result;
   {
     Expression* iterator_proxy = factory()->NewVariableProxy(iterator);
-    next_result =
-        BuildIteratorNextResult(iterator_proxy, result, next_result_pos);
+    next_result = BuildIteratorNextResult(
+        iterator_proxy, result, IteratorType::kNormal, next_result_pos);
   }
 
   // result.done
   Expression* result_done;
   {
     Expression* done_literal = factory()->NewStringLiteral(
         ast_value_factory()->done_string(), kNoSourcePosition);
     Expression* result_proxy = factory()->NewVariableProxy(result);
     result_done =
         factory()->NewProperty(result_proxy, done_literal, kNoSourcePosition);
@@ skipping 67 matching lines @@
   // Statement* body (gets overwritten)
   if (finalize) {
     Block* block = factory()->NewBlock(nullptr, 2, false, nopos);
     block->statements()->Add(body, zone());
     block->statements()->Add(set_completion_normal, zone());
     body = block;
   }
 
   for_of->Initialize(body, iterator, assign_iterator, next_result, result_done,
                      assign_each);
-  return finalize ? FinalizeForOfStatement(for_of, completion, nopos) : for_of;
+  return finalize ? FinalizeForOfStatement(for_of, completion,
+                                           IteratorType::kNormal, nopos)
+                  : for_of;
+}
+
+Statement* Parser::InitializeForAwaitOfStatement(ForEachStatement* for_each,

[neis, 2017/01/20 14:38:15]

Can't you just parameterize the existing InitializeForOfStatement over
IteratorType?

[caitp, 2017/01/20 17:05:34]

It's doable, but harder to read IMO
. Whatever people want here i guess 

[caitp, 2017/01/20 20:17:19]

Eh, it actually gets pretty ugly to try to do it this way. The preparser doesn't
know about ForOfStatements, so the patch would have to teach it about them to do
that. Otherwise, InitializeForOfStatement would need to be changed to accept a
ForEachStatement as its parameter.

Either way, those changes are unrelated, and reduce type safety a bit. Far as I
can see, the only real alternative is to alter the ForEachStatement ast node to
include the VisitMode in the ForEachStatement node itself, so that it knows
which initialize method to invoke from InitializeForEachStatement.

I'll include the simplest change I guess.

+                                                 Expression* each,
+                                                 Expression* iterable,
+                                                 Statement* body, bool finalize,
+                                                 int next_result_pos) {
+  // Create the auxiliary expressions needed for iterating over the iterable,
+  // and initialize the given ForOfStatement with them.
+  // If finalize is true, also instrument the loop with code that performs the
+  // proper ES6 iterator finalization.  In that case, the result is not
+  // immediately a ForOfStatement.
+
+  ForOfStatement* for_of = for_each->AsForOfStatement();
+  DCHECK_NOT_NULL(for_of);
+
+  const int nopos = kNoSourcePosition;
+  auto avfactory = ast_value_factory();
+
+  Variable* iterator = NewTemporary(avfactory->dot_iterator_string());
+  Variable* result = NewTemporary(avfactory->dot_result_string());
+  Variable* completion = NewTemporary(avfactory->empty_string());
+
+  // iterator = GetIterator(iterable)

[neis, 2017/01/20 14:38:16]

Comment needs an update.

+  Expression* assign_iterator;
+  {
+    assign_iterator = factory()->NewAssignment(
+        Token::ASSIGN, factory()->NewVariableProxy(iterator),
+        factory()->NewGetIterator(iterable, GetIterator::kAsync,
+                                  iterable->position()),
+        iterable->position());
+  }
+
+  // !%_IsJSReceiver(result = iterator.next()) &&
+  //     %ThrowIteratorResultNotAnObject(result)

[neis, 2017/01/20 14:38:15]

Comment needs an update.

+  Expression* next_result;
+  {
+    Expression* iterator_proxy = factory()->NewVariableProxy(iterator);
+    next_result = BuildIteratorNextResult(
+        iterator_proxy, result, IteratorType::kAsync, next_result_pos);
+  }
+
+  // result.done
+  Expression* result_done;
+  {
+    Expression* done_literal = factory()->NewStringLiteral(
+        ast_value_factory()->done_string(), kNoSourcePosition);
+    Expression* result_proxy = factory()->NewVariableProxy(result);
+    result_done =
+        factory()->NewProperty(result_proxy, done_literal, kNoSourcePosition);
+  }
+
+  // result.value
+  Expression* result_value;
+  {
+    Expression* value_literal =
+        factory()->NewStringLiteral(avfactory->value_string(), nopos);
+    Expression* result_proxy = factory()->NewVariableProxy(result);
+    result_value = factory()->NewProperty(result_proxy, value_literal, nopos);
+  }
+
+  // {{completion = kAbruptCompletion;}}
+  Statement* set_completion_abrupt;
+  if (finalize) {
+    Expression* proxy = factory()->NewVariableProxy(completion);
+    Expression* assignment = factory()->NewAssignment(
+        Token::ASSIGN, proxy,
+        factory()->NewSmiLiteral(Parser::kAbruptCompletion, nopos), nopos);
+
+    Block* block = factory()->NewBlock(nullptr, 1, true, nopos);
+    block->statements()->Add(
+        factory()->NewExpressionStatement(assignment, nopos), zone());
+    set_completion_abrupt = block;
+  }
+
+  // do { let tmp = #result_value; #set_completion_abrupt; tmp }
+  // Expression* result_value (gets overwritten)
+  if (finalize) {
+    Variable* var_tmp = NewTemporary(avfactory->empty_string());
+    Expression* tmp = factory()->NewVariableProxy(var_tmp);
+    Expression* assignment =
+        factory()->NewAssignment(Token::ASSIGN, tmp, result_value, nopos);
+
+    Block* block = factory()->NewBlock(nullptr, 2, false, nopos);
+    block->statements()->Add(
+        factory()->NewExpressionStatement(assignment, nopos), zone());
+    block->statements()->Add(set_completion_abrupt, zone());
+
+    result_value = factory()->NewDoExpression(block, var_tmp, nopos);
+  }
+
+  // each = #result_value;
+  Expression* assign_each;
+  {
+    assign_each =
+        factory()->NewAssignment(Token::ASSIGN, each, result_value, nopos);
+    if (each->IsArrayLiteral() || each->IsObjectLiteral()) {
+      assign_each = PatternRewriter::RewriteDestructuringAssignment(
+          this, assign_each->AsAssignment(), scope());
+    }
+  }
+
+  // {{completion = kNormalCompletion;}}
+  Statement* set_completion_normal;
+  if (finalize) {
+    Expression* proxy = factory()->NewVariableProxy(completion);
+    Expression* assignment = factory()->NewAssignment(
+        Token::ASSIGN, proxy,
+        factory()->NewSmiLiteral(Parser::kNormalCompletion, nopos), nopos);
+
+    Block* block = factory()->NewBlock(nullptr, 1, true, nopos);
+    block->statements()->Add(
+        factory()->NewExpressionStatement(assignment, nopos), zone());
+    set_completion_normal = block;
+  }
+
+  // { #loop-body; #set_completion_normal }
+  // Statement* body (gets overwritten)
+  if (finalize) {
+    Block* block = factory()->NewBlock(nullptr, 2, false, nopos);
+    block->statements()->Add(body, zone());
+    block->statements()->Add(set_completion_normal, zone());
+    body = block;
+  }
+
+  for_of->Initialize(body, iterator, assign_iterator, next_result, result_done,
+                     assign_each);
+  return finalize ? FinalizeForOfStatement(for_of, completion,
+                                           IteratorType::kAsync, nopos)
+                  : for_of;
 }
 
 Statement* Parser::DesugarLexicalBindingsInForStatement(
     ForStatement* loop, Statement* init, Expression* cond, Statement* next,
     Statement* body, Scope* inner_scope, const ForInfo& for_info, bool* ok) {
   // ES6 13.7.4.8 specifies that on each loop iteration the let variables are
   // copied into a new environment.  Moreover, the "next" statement must be
   // evaluated not in the environment of the just completed iteration but in
   // that of the upcoming one.  We achieve this with the following desugaring.
   // Extra care is needed to preserve the completion value of the original loop.
@@ skipping 644 matching lines @@
     reusable_preparser_ = new PreParser(
         zone(), &scanner_, stack_limit_, ast_value_factory(),
         &pending_error_handler_, runtime_call_stats_, parsing_on_main_thread_);
 #define SET_ALLOW(name) reusable_preparser_->set_allow_##name(allow_##name());
     SET_ALLOW(natives);
     SET_ALLOW(harmony_do_expressions);
     SET_ALLOW(harmony_function_sent);
     SET_ALLOW(harmony_trailing_commas);
     SET_ALLOW(harmony_class_fields);
     SET_ALLOW(harmony_object_rest_spread);
+    SET_ALLOW(harmony_async_iteration);
 #undef SET_ALLOW
   }
   // Aborting inner function preparsing would leave scopes in an inconsistent
   // state; we don't parse inner functions in the abortable mode anyway.
   DCHECK(!is_inner_function || !may_abort);
 
   PreParser::PreParseResult result = reusable_preparser_->PreParseFunction(
       kind, function_scope, parsing_module_, is_inner_function, may_abort,
       use_counts_);
 
@@ skipping 1585 matching lines @@
     Expression* assignment =
         factory()->NewAssignment(Token::ASSIGN, output_proxy,
                                  factory()->NewUndefinedLiteral(nopos), nopos);
     initialize_output = factory()->NewExpressionStatement(assignment, nopos);
   }
 
   // let iterator = GetIterator(iterable);
   Variable* var_iterator = NewTemporary(ast_value_factory()->empty_string());
   Statement* get_iterator;
   {
-    Expression* iterator = factory()->NewGetIterator(iterable, nopos);
+    Expression* iterator =
+        factory()->NewGetIterator(iterable, GetIterator::kNormal, nopos);
     Expression* iterator_proxy = factory()->NewVariableProxy(var_iterator);
     Expression* assignment = factory()->NewAssignment(
         Token::ASSIGN, iterator_proxy, iterator, nopos);
     get_iterator = factory()->NewExpressionStatement(assignment, nopos);
   }
 
   // output = iterator.next(input);
   Statement* call_next;
   {
     Expression* iterator_proxy = factory()->NewVariableProxy(var_iterator);
@@ skipping 61 matching lines @@
         Token::EQ, factory()->NewVariableProxy(var_throw),
         factory()->NewNullLiteral(nopos), nopos);
     Expression* call =
         NewThrowTypeError(MessageTemplate::kThrowMethodMissing,
                           ast_value_factory()->empty_string(), nopos);
     Statement* throw_call = factory()->NewExpressionStatement(call, nopos);
 
     Block* then = factory()->NewBlock(nullptr, 4 + 1, false, nopos);
     BuildIteratorCloseForCompletion(
         scope(), then->statements(), var_iterator,
-        factory()->NewSmiLiteral(Parser::kNormalCompletion, nopos));
+        factory()->NewSmiLiteral(Parser::kNormalCompletion, nopos),
+        IteratorType::kNormal);
     then->statements()->Add(throw_call, zone());
     check_throw = factory()->NewIfStatement(
         condition, then, factory()->NewEmptyStatement(nopos), nopos);
   }
 
   // output = %_Call(iteratorThrow, iterator, input);
   Statement* call_throw;
   {
     auto args = new (zone()) ZoneList<Expression*>(3, zone());
     args->Add(factory()->NewVariableProxy(var_throw), zone());
@@ skipping 165 matching lines @@
 
   // switch (mode) { ... }
   SwitchStatement* switch_mode = factory()->NewSwitchStatement(nullptr, nopos);
   {
     auto case_next = new (zone()) ZoneList<Statement*>(3, zone());
     case_next->Add(call_next, zone());
     case_next->Add(validate_next_output, zone());
     case_next->Add(factory()->NewBreakStatement(switch_mode, nopos), zone());
 
     auto case_return = new (zone()) ZoneList<Statement*>(5, zone());
-    BuildIteratorClose(case_return, var_iterator, var_input, var_output);
+    BuildIteratorClose(case_return, var_iterator, var_input, var_output,
+                       IteratorType::kNormal);
     case_return->Add(factory()->NewBreakStatement(switch_mode, nopos), zone());
 
     auto case_throw = new (zone()) ZoneList<Statement*>(5, zone());
     case_throw->Add(get_throw, zone());
     case_throw->Add(check_throw, zone());
     case_throw->Add(call_throw, zone());
     case_throw->Add(validate_throw_output, zone());
     case_throw->Add(factory()->NewBreakStatement(switch_mode, nopos), zone());
 
     auto cases = new (zone()) ZoneList<CaseClause*>(3, zone());
@@ skipping 63 matching lines @@
     Statement* throw_call = factory()->NewExpressionStatement(error, pos);
 
     validate_var = factory()->NewIfStatement(
         condition, factory()->NewEmptyStatement(nopos), throw_call, nopos);
   }
   return validate_var;
 }
 
 void Parser::BuildIteratorClose(ZoneList<Statement*>* statements,
                                 Variable* iterator, Variable* input,
-                                Variable* var_output) {
+                                Variable* var_output, IteratorType type) {
   //

[neis, 2017/01/20 14:38:15]

This function is only used in RewriteYieldStar and doesn't need to be touched in
this CL.

[caitp, 2017/01/20 17:05:34]

That may be a bug then. You're supposed to IteratorClose on break, based on my
read of the spec

"If LoopContinues(result, labelSet) is false, return ? IteratorClose(iterator,
UpdateEmpty(result, V))."

LoopContinues looks like it will return false on break continuations, thus
performing IteratorClose

   // This function adds four statements to [statements], corresponding to the
   // following code:
   //
   //   let iteratorReturn = iterator.return;
   //   if (IS_NULL_OR_UNDEFINED(iteratorReturn) {
   //     return {value: input, done: true};
   //   }
-  //   output = %_Call(iteratorReturn, iterator, input);
+  //
+  //   [if (IteratorType == kAsync)]
+  //     output = Await(%_Call(iteratorReturn, iterator, input));
+  //   [else]
+  //     output = %_Call(iteratorReturn, iterator, input);
+  //   [endif]
+  //
   //   if (!IS_RECEIVER(output)) %ThrowIterResultNotAnObject(output);
   //
 
   const int nopos = kNoSourcePosition;
 
   // let iteratorReturn = iterator.return;
   Variable* var_return = var_output;  // Reusing the output variable.
   Statement* get_return;
   {
     Expression* iterator_proxy = factory()->NewVariableProxy(iterator);
@@ skipping 28 matching lines @@
   // output = %_Call(iteratorReturn, iterator, input);
   Statement* call_return;
   {
     auto args = new (zone()) ZoneList<Expression*>(3, zone());
     args->Add(factory()->NewVariableProxy(var_return), zone());
     args->Add(factory()->NewVariableProxy(iterator), zone());
     args->Add(factory()->NewVariableProxy(input), zone());
 
     Expression* call =
         factory()->NewCallRuntime(Runtime::kInlineCall, args, nopos);
+    if (type == IteratorType::kAsync) {
+      call = RewriteAwaitExpression(call, nopos);
+    }
+
     Expression* output_proxy = factory()->NewVariableProxy(var_output);
     Expression* assignment =
         factory()->NewAssignment(Token::ASSIGN, output_proxy, call, nopos);
     call_return = factory()->NewExpressionStatement(assignment, nopos);
   }
 
   // if (!IS_RECEIVER(output)) %ThrowIteratorResultNotAnObject(output);
   Statement* validate_output;
   {
     Expression* is_receiver_call;
@@ skipping 19 matching lines @@
   }
 
   statements->Add(get_return, zone());
   statements->Add(check_return, zone());
   statements->Add(call_return, zone());
   statements->Add(validate_output, zone());
 }
 
 void Parser::FinalizeIteratorUse(Scope* use_scope, Variable* completion,
                                  Expression* condition, Variable* iter,
-                                 Block* iterator_use, Block* target) {
+                                 Block* iterator_use, Block* target,
+                                 IteratorType type) {
   //
   // This function adds two statements to [target], corresponding to the
   // following code:
   //
   //   completion = kNormalCompletion;
   //   try {
   //     try {
   //       iterator_use
   //     } catch(e) {
   //       if (completion === kAbruptCompletion) completion = kThrowCompletion;
@@ skipping 35 matching lines @@
         condition, statement, factory()->NewEmptyStatement(nopos), nopos);
   }
 
   // if (condition) {
   //   #BuildIteratorCloseForCompletion(iter, completion)
   // }
   Block* maybe_close;
   {
     Block* block = factory()->NewBlock(nullptr, 2, true, nopos);
     Expression* proxy = factory()->NewVariableProxy(completion);
-    BuildIteratorCloseForCompletion(use_scope, block->statements(), iter,
-                                    proxy);
+    BuildIteratorCloseForCompletion(use_scope, block->statements(), iter, proxy,
+                                    type);
     DCHECK(block->statements()->length() == 2);
 
     maybe_close = factory()->NewBlock(nullptr, 1, true, nopos);
     maybe_close->statements()->Add(
         factory()->NewIfStatement(condition, block,
                                   factory()->NewEmptyStatement(nopos), nopos),
         zone());
   }
 
   // try { #try_block }
@@ skipping 38 matching lines @@
         factory()->NewTryFinallyStatement(try_block, maybe_close, nopos);
   }
 
   target->statements()->Add(initialize_completion, zone());
   target->statements()->Add(try_finally, zone());
 }
 
 void Parser::BuildIteratorCloseForCompletion(Scope* scope,
                                              ZoneList<Statement*>* statements,
                                              Variable* iterator,
-                                             Expression* completion) {
+                                             Expression* completion,
+                                             IteratorType type) {
   //
   // This function adds two statements to [statements], corresponding to the
   // following code:
   //
   //   let iteratorReturn = iterator.return;
   //   if (!IS_NULL_OR_UNDEFINED(iteratorReturn)) {
   //     if (completion === kThrowCompletion) {
   //       if (!IS_CALLABLE(iteratorReturn)) {
   //         throw MakeTypeError(kReturnMethodNotCallable);
   //       }
   //       try { %_Call(iteratorReturn, iterator) } catch (_) { }
   //     } else {
   //       let output = %_Call(iteratorReturn, iterator);
   //       if (!IS_RECEIVER(output)) {
   //         %ThrowIterResultNotAnObject(output);
   //       }
   //     }
   //   }
   //

[neis, 2017/01/20 14:38:15]

Comment needs an update.

 
   const int nopos = kNoSourcePosition;
   // let iteratorReturn = iterator.return;
   Variable* var_return = NewTemporary(ast_value_factory()->empty_string());
   Statement* get_return;
   {
     Expression* iterator_proxy = factory()->NewVariableProxy(iterator);
     Expression* literal = factory()->NewStringLiteral(
         ast_value_factory()->return_string(), nopos);
     Expression* property =
         factory()->NewProperty(iterator_proxy, literal, nopos);
     Expression* return_proxy = factory()->NewVariableProxy(var_return);
     Expression* assignment =
         factory()->NewAssignment(Token::ASSIGN, return_proxy, property, nopos);
     get_return = factory()->NewExpressionStatement(assignment, nopos);
   }
 
   // if (!IS_CALLABLE(iteratorReturn)) {
   //   throw MakeTypeError(kReturnMethodNotCallable);
   // }
   Statement* check_return_callable;
   {
     Expression* throw_expr =
         NewThrowTypeError(MessageTemplate::kReturnMethodNotCallable,
                           ast_value_factory()->empty_string(), nopos);
     check_return_callable = CheckCallable(var_return, throw_expr, nopos);
   }
 
   // try { %_Call(iteratorReturn, iterator) } catch (_) { }

[neis, 2017/01/20 14:38:15]

Comment needs an update.

   Statement* try_call_return;
   {
     auto args = new (zone()) ZoneList<Expression*>(2, zone());
     args->Add(factory()->NewVariableProxy(var_return), zone());
     args->Add(factory()->NewVariableProxy(iterator), zone());
 
     Expression* call =
         factory()->NewCallRuntime(Runtime::kInlineCall, args, nopos);
 
+    if (type == IteratorType::kAsync) {
+      call = RewriteAwaitExpression(call, nopos);
+    }
+
     Block* try_block = factory()->NewBlock(nullptr, 1, false, nopos);
     try_block->statements()->Add(factory()->NewExpressionStatement(call, nopos),
                                  zone());
 
     Block* catch_block = factory()->NewBlock(nullptr, 0, false, nopos);
 
     Scope* catch_scope = NewScopeWithParent(scope, CATCH_SCOPE);
     Variable* catch_variable =
         catch_scope->DeclareLocal(ast_value_factory()->dot_catch_string(), VAR);
     catch_scope->set_is_hidden();
@@ skipping 14 matching lines @@
       auto args = new (zone()) ZoneList<Expression*>(2, zone());
       args->Add(factory()->NewVariableProxy(var_return), zone());
       args->Add(factory()->NewVariableProxy(iterator), zone());
       Expression* call =
           factory()->NewCallRuntime(Runtime::kInlineCall, args, nopos);
 
       Expression* output_proxy = factory()->NewVariableProxy(var_output);
       Expression* assignment =
           factory()->NewAssignment(Token::ASSIGN, output_proxy, call, nopos);
       call_return = factory()->NewExpressionStatement(assignment, nopos);
     }

[neis, 2017/01/20 14:38:15]

We must also do await on the result of this call.

[caitp, 2017/01/23 14:18:15]

Done.

 
     Expression* is_receiver_call;
     {
       auto args = new (zone()) ZoneList<Expression*>(1, zone());
       args->Add(factory()->NewVariableProxy(var_output), zone());
       is_receiver_call =
           factory()->NewCallRuntime(Runtime::kInlineIsJSReceiver, args, nopos);
     }
 
     Statement* throw_call;
@@ skipping 44 matching lines @@
     maybe_call_return = factory()->NewIfStatement(
         condition, factory()->NewEmptyStatement(nopos), call_return_carefully,
         nopos);
   }
 
   statements->Add(get_return, zone());
   statements->Add(maybe_call_return, zone());
 }
 
 Statement* Parser::FinalizeForOfStatement(ForOfStatement* loop,
-                                          Variable* var_completion, int pos) {
+                                          Variable* var_completion,
+                                          IteratorType type, int pos) {
   //
   // This function replaces the loop with the following wrapping:
   //
   //   completion = kNormalCompletion;
   //   try {
   //     try {
   //       #loop;
   //     } catch(e) {
   //       if (completion === kAbruptCompletion) completion = kThrowCompletion;
   //       %ReThrow(e);
   //     }
   //   } finally {
   //     if (!(completion === kNormalCompletion)) {
   //       #BuildIteratorCloseForCompletion(#iterator, completion)

[neis, 2017/01/20 14:38:15]

Comment needs an update.

   //     }
   //   }
   //
   // Note that the loop's body and its assign_each already contain appropriate
   // assignments to completion (see InitializeForOfStatement).
   //
 
   const int nopos = kNoSourcePosition;
 
   // !(completion === kNormalCompletion)
   Expression* closing_condition;
   {
     Expression* cmp = factory()->NewCompareOperation(
         Token::EQ_STRICT, factory()->NewVariableProxy(var_completion),
         factory()->NewSmiLiteral(Parser::kNormalCompletion, nopos), nopos);
     closing_condition = factory()->NewUnaryOperation(Token::NOT, cmp, nopos);
   }
 
   Block* final_loop = factory()->NewBlock(nullptr, 2, false, nopos);
   {
     Block* try_block = factory()->NewBlock(nullptr, 1, false, nopos);
     try_block->statements()->Add(loop, zone());
 
     // The scope in which the parser creates this loop.
     Scope* loop_scope = scope()->outer_scope();
     DCHECK_EQ(loop_scope->scope_type(), BLOCK_SCOPE);
     DCHECK_EQ(scope()->scope_type(), BLOCK_SCOPE);
 
     FinalizeIteratorUse(loop_scope, var_completion, closing_condition,
-                        loop->iterator(), try_block, final_loop);
+                        loop->iterator(), try_block, final_loop, type);
   }
 
   return final_loop;
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_VOID
 #undef CHECK_FAILED
 
 }  // namespace internal
 }  // namespace v8