[parser] removed undefined check of for-of iterator

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 5413 matching lines @@
   //
   //   completion = kNormalCompletion;
   //   try {
   //     try {
   //       #loop;
   //     } catch(e) {
   //       if (completion === kAbruptCompletion) completion = kThrowCompletion;
   //       %ReThrow(e);
   //     }
   //   } finally {
-  //     if (!(completion === kNormalCompletion || IS_UNDEFINED(#iterator))) {
+  //     if (!(completion === kNormalCompletion)) {

[neis, 2016/11/28 14:52:51]

See below.

   //       #BuildIteratorCloseForCompletion(#iterator, completion)
   //     }
   //   }
   //
   // Note that the loop's body and its assign_each already contain appropriate
   // assignments to completion (see InitializeForOfStatement).
   //
 
   const int nopos = kNoSourcePosition;
 
-  // !(completion === kNormalCompletion || IS_UNDEFINED(#iterator))
+  // !(completion === kNormalCompletion)
   Expression* closing_condition;
   {
-    Expression* lhs = factory()->NewCompareOperation(
+    Expression* cmp = factory()->NewCompareOperation(
         Token::EQ_STRICT, factory()->NewVariableProxy(var_completion),
         factory()->NewSmiLiteral(Parser::kNormalCompletion, nopos), nopos);
-    Expression* rhs = factory()->NewCompareOperation(
-        Token::EQ_STRICT, factory()->NewVariableProxy(loop->iterator()),
-        factory()->NewUndefinedLiteral(nopos), nopos);
-    closing_condition = factory()->NewUnaryOperation(
-        Token::NOT, factory()->NewBinaryOperation(Token::OR, lhs, rhs, nopos),
-        nopos);
+    closing_condition = factory()->NewUnaryOperation(Token::NOT, cmp, nopos);

[neis, 2016/11/28 14:52:51]

You can use NE_STRICT (!==) instead of negating EQ_STRICT.

   }
 
   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);
   }
 
   return final_loop;
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_VOID
 #undef CHECK_FAILED
 
 }  // namespace internal
 }  // namespace v8