Implement proper scoping for "this" in arrow functions

src/x64/lithium-codegen-x64.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_X64
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 112 matching lines @@
 #ifdef DEBUG
     if (strlen(FLAG_stop_at) > 0 &&
         info_->function()->name()->IsUtf8EqualTo(CStrVector(FLAG_stop_at))) {
       __ int3();
     }
 #endif
 
     // Sloppy mode functions need to replace the receiver with the global proxy
     // when called as functions (without an explicit receiver object).
     if (info_->this_has_uses() && is_sloppy(info_->language_mode()) &&
-        !info_->is_native()) {
+        !info_->is_native() && info_->scope()->has_this_declaration()) {
       Label ok;
       StackArgumentsAccessor args(rsp, scope()->num_parameters());
       __ movp(rcx, args.GetReceiverOperand());
 
       __ CompareRoot(rcx, Heap::kUndefinedValueRootIndex);
       __ j(not_equal, &ok, Label::kNear);
 
       __ movp(rcx, GlobalObjectOperand());
       __ movp(rcx, FieldOperand(rcx, GlobalObject::kGlobalProxyOffset));
 
@@ skipping 61 matching lines @@
       __ CallRuntime(Runtime::kNewFunctionContext, 1);
     }
     RecordSafepoint(Safepoint::kNoLazyDeopt);
     // Context is returned in rax.  It replaces the context passed to us.
     // It's saved in the stack and kept live in rsi.
     __ movp(rsi, rax);
     __ movp(Operand(rbp, StandardFrameConstants::kContextOffset), rax);
 
     // Copy any necessary parameters into the context.
     int num_parameters = scope()->num_parameters();
-    for (int i = 0; i < num_parameters; i++) {
-      Variable* var = scope()->parameter(i);
+    int first_parameter = scope()->has_this_declaration() ? -1 : 0;
+    for (int i = first_parameter; i < num_parameters; i++) {
+      Variable* var = (i == -1) ? scope()->receiver() : scope()->parameter(i);
       if (var->IsContextSlot()) {
         int parameter_offset = StandardFrameConstants::kCallerSPOffset +
             (num_parameters - 1 - i) * kPointerSize;
         // Load parameter from stack.
         __ movp(rax, Operand(rbp, parameter_offset));
         // Store it in the context.
         int context_offset = Context::SlotOffset(var->index());
         __ movp(Operand(rsi, context_offset), rax);
         // Update the write barrier. This clobbers rax and rbx.
         if (need_write_barrier) {
@@ skipping 5709 matching lines @@
   CallRuntime(Runtime::kPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64