new classes: special construct stub for derived classs and TDZ for `this`.

src/arm64/full-codegen-arm64.cc

 // Copyright 2013 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/v8.h"
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 1499 matching lines @@
         //   if (false) { const x; }; var y = x;
         //
         // The condition on the declaration scopes is a conservative check for
         // nested functions that access a binding and are called before the
         // binding is initialized:
         //   function() { f(); let x = 1; function f() { x = 2; } }
         //
         bool skip_init_check;
         if (var->scope()->DeclarationScope() != scope()->DeclarationScope()) {
           skip_init_check = false;
+        } else if (var->is_this()) {
+          // TODO(dslomov): implement 'this' hole check elimination.
+          skip_init_check = false;
         } else {
           // Check that we always have valid source position.
           DCHECK(var->initializer_position() != RelocInfo::kNoPosition);
           DCHECK(proxy->position() != RelocInfo::kNoPosition);
           skip_init_check = var->mode() != CONST_LEGACY &&
               var->initializer_position() < proxy->position();
         }
 
         if (!skip_init_check) {
           // Let and const need a read barrier.
@@ skipping 1440 matching lines @@
 
   __ LoadObject(x2, FeedbackVector());
   __ Mov(x3, SmiFromSlot(expr->CallFeedbackSlot()));
 
   // TODO(dslomov): use a different stub and propagate new.target.
   CallConstructStub stub(isolate(), RECORD_CONSTRUCTOR_TARGET);
   __ Call(stub.GetCode(), RelocInfo::CONSTRUCT_CALL);
 
   RecordJSReturnSite(expr);
 
-  // TODO(dslomov): implement TDZ for `this`.
-  EmitVariableAssignment(super_ref->this_var()->var(), Token::ASSIGN);
+  EmitVariableAssignment(super_ref->this_var()->var(), Token::INIT_CONST);
   context()->Plug(x0);
 }
 
 
 void FullCodeGenerator::EmitIsSmi(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   DCHECK(args->length() == 1);
 
   VisitForAccumulatorValue(args->at(0));
 
@@ skipping 2398 matching lines @@
   return previous_;
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64