Implement proper scoping for "this" in arrow functions

src/mips64/lithium-codegen-mips64.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/v8.h"
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/hydrogen-osr.h"
 #include "src/ic/ic.h"
@@ skipping 101 matching lines @@
     // a1: Callee's JS function.
     // cp: Callee's context.
     // fp: Caller's frame pointer.
     // lr: Caller's pc.
 
     // Sloppy mode functions and builtins need to replace the receiver with the
     // global proxy when called as functions (without an explicit receiver
     // object).
     if (info_->this_has_uses() &&
         info_->strict_mode() == SLOPPY &&
-        !info_->is_native()) {
+        !info_->is_native() &&
+        info_->scope()->has_this_declaration()) {
       Label ok;
       int receiver_offset = info_->scope()->num_parameters() * kPointerSize;
       __ LoadRoot(at, Heap::kUndefinedValueRootIndex);
       __ ld(a2, MemOperand(sp, receiver_offset));
       __ Branch(&ok, ne, a2, Operand(at));
 
       __ ld(a2, GlobalObjectOperand());
       __ ld(a2, FieldMemOperand(a2, GlobalObject::kGlobalProxyOffset));
 
       __ sd(a2, MemOperand(sp, receiver_offset));
@@ skipping 51 matching lines @@
       __ push(a1);
       __ CallRuntime(Runtime::kNewFunctionContext, 1);
     }
     RecordSafepoint(Safepoint::kNoLazyDeopt);
     // Context is returned in both v0. It replaces the context passed to us.
     // It's saved in the stack and kept live in cp.
     __ mov(cp, v0);
     __ sd(v0, MemOperand(fp, StandardFrameConstants::kContextOffset));
     // 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.
         __ ld(a0, MemOperand(fp, parameter_offset));
         // Store it in the context.
         MemOperand target = ContextOperand(cp, var->index());
         __ sd(a0, target);
         // Update the write barrier. This clobbers a3 and a0.
         if (need_write_barrier) {
@@ skipping 5778 matching lines @@
   __ li(at, scope_info);
   __ Push(at, ToRegister(instr->function()));
   CallRuntime(Runtime::kPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal