[ignition] desugar GetIterator() via bytecode rather than via AST

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 486 matching lines @@
       bool has_dot = scanner()->ContainsDot();
       double value = scanner()->DoubleValue();
       return factory()->NewNumberLiteral(value, pos, has_dot);
     }
     default:
       DCHECK(false);
   }
   return NULL;
 }
 
-Expression* Parser::GetIterator(Expression* iterable, int pos) {
-  Expression* iterator_symbol_literal =
-      factory()->NewSymbolLiteral("iterator_symbol", kNoSourcePosition);
-  Expression* prop =
-      factory()->NewProperty(iterable, iterator_symbol_literal, pos);
-  ZoneList<Expression*>* args = new (zone()) ZoneList<Expression*>(0, zone());
-  return factory()->NewCall(prop, args, pos);
-}
-
 void Parser::MarkTailPosition(Expression* expression) {
   expression->MarkTail();
 }
 
 Expression* Parser::NewV8Intrinsic(const AstRawString* name,
                                    ZoneList<Expression*>* args, int pos,
                                    bool* ok) {
   if (extension_ != nullptr) {
     // The extension structures are only accessible while parsing the
     // very first time, not when reparsing because of lazy compilation.
@@ skipping 1545 matching lines @@
 
   Variable* iterator = NewTemporary(ast_value_factory()->dot_iterator_string());
   Variable* result = NewTemporary(ast_value_factory()->dot_result_string());
   Variable* completion = NewTemporary(avfactory->empty_string());
 
   // iterator = iterable[Symbol.iterator]()
   Expression* assign_iterator;
   {
     assign_iterator = factory()->NewAssignment(
         Token::ASSIGN, factory()->NewVariableProxy(iterator),
-        GetIterator(iterable, iterable->position()), iterable->position());
+        factory()->NewGetIterator(iterable, 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);
   }
@@ skipping 2470 matching lines @@
 //
 //   do {
 //     const kNext = 0;
 //     const kReturn = 1;
 //     const kThrow = 2;
 //
 //     let input = function.sent;
 //     let mode = kNext;
 //     let output = undefined;
 //
-//     let iterator = iterable[Symbol.iterator]();
-//     if (!IS_RECEIVER(iterator)) throw MakeTypeError(kSymbolIteratorInvalid);
+//     let iterator = GetIterator(iterable);
 //
 //     while (true) {
 //       // From the generator to the iterator:
 //       // Forward input according to resume mode and obtain output.
 //       switch (mode) {
 //         case kNext:
 //           output = iterator.next(input);
 //           if (!IS_RECEIVER(output)) %ThrowIterResultNotAnObject(output);
 //           break;
 //         case kReturn:
@@ skipping 82 matching lines @@
   Variable* var_output = NewTemporary(ast_value_factory()->empty_string());
   Statement* initialize_output;
   {
     Expression* output_proxy = factory()->NewVariableProxy(var_output);
     Expression* assignment =
         factory()->NewAssignment(Token::ASSIGN, output_proxy,
                                  factory()->NewUndefinedLiteral(nopos), nopos);
     initialize_output = factory()->NewExpressionStatement(assignment, nopos);
   }
 
   // let iterator = iterable[Symbol.iterator];

[adamk, 2016/12/06 18:49:05]

Please update this comment to to match the full desugaring above.

[caitp, 2016/12/06 19:00:44]

Acknowledged.

   Variable* var_iterator = NewTemporary(ast_value_factory()->empty_string());
   Statement* get_iterator;
   {
-    Expression* iterator = GetIterator(iterable, nopos);
+    Expression* iterator = factory()->NewGetIterator(iterable, nopos);
     Expression* iterator_proxy = factory()->NewVariableProxy(var_iterator);
     Expression* assignment = factory()->NewAssignment(
         Token::ASSIGN, iterator_proxy, iterator, nopos);
     get_iterator = factory()->NewExpressionStatement(assignment, nopos);
   }
 
-  // if (!IS_RECEIVER(iterator)) throw MakeTypeError(kSymbolIteratorInvalid);
-  Statement* validate_iterator;
-  {
-    Expression* is_receiver_call;
-    {
-      auto args = new (zone()) ZoneList<Expression*>(1, zone());
-      args->Add(factory()->NewVariableProxy(var_iterator), zone());
-      is_receiver_call =
-          factory()->NewCallRuntime(Runtime::kInlineIsJSReceiver, args, nopos);
-    }
-
-    Statement* throw_call;
-    {
-      Expression* call =
-          NewThrowTypeError(MessageTemplate::kSymbolIteratorInvalid,
-                            ast_value_factory()->empty_string(), nopos);
-      throw_call = factory()->NewExpressionStatement(call, nopos);
-    }
-
-    validate_iterator = factory()->NewIfStatement(
-        is_receiver_call, factory()->NewEmptyStatement(nopos), throw_call,
-        nopos);
-  }
-
   // output = iterator.next(input);
   Statement* call_next;
   {
     Expression* iterator_proxy = factory()->NewVariableProxy(var_iterator);
     Expression* literal =
         factory()->NewStringLiteral(ast_value_factory()->next_string(), nopos);
     Expression* next_property =
         factory()->NewProperty(iterator_proxy, literal, nopos);
     Expression* input_proxy = factory()->NewVariableProxy(var_input);
     auto args = new (zone()) ZoneList<Expression*>(1, zone());
@@ skipping 284 matching lines @@
 
     loop->Initialize(factory()->NewBooleanLiteral(true, nopos), loop_body);
   }
 
   // do { ... }
   DoExpression* yield_star;
   {
     // The rewriter needs to process the get_value statement only, hence we
     // put the preceding statements into an init block.
 
-    Block* do_block_ = factory()->NewBlock(nullptr, 7, true, nopos);
+    Block* do_block_ = factory()->NewBlock(nullptr, 6, true, nopos);
     do_block_->statements()->Add(initialize_input, zone());
     do_block_->statements()->Add(initialize_mode, zone());
     do_block_->statements()->Add(initialize_output, zone());
     do_block_->statements()->Add(get_iterator, zone());
-    do_block_->statements()->Add(validate_iterator, zone());
     do_block_->statements()->Add(loop, zone());
     do_block_->statements()->Add(maybe_return_value, zone());
 
     Block* do_block = factory()->NewBlock(nullptr, 2, false, nopos);
     do_block->statements()->Add(do_block_, zone());
     do_block->statements()->Add(get_value, zone());
 
     Variable* dot_result =
         NewTemporary(ast_value_factory()->dot_result_string());
     yield_star = factory()->NewDoExpression(do_block, dot_result, nopos);
@@ skipping 445 matching lines @@
 
   return final_loop;
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_VOID
 #undef CHECK_FAILED
 
 }  // namespace internal
 }  // namespace v8