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

src/ia32/full-codegen-ia32.cc

Index: src/ia32/full-codegen-ia32.cc
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index b4195350cbb4641f21c07225681efab25d5e89d9..5e8e310ef96789148e31508ef76c0b5ec7eb75a8 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -1460,6 +1460,9 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy) {
         bool skip_init_check;
         if (var->scope()->DeclarationScope() != scope()->DeclarationScope()) {
           skip_init_check = false;
+        } else if (var->is_this()) {

[rossberg, 2015/02/02 16:32:37]

Does this now affect every use of 'this'? Can we limit the check to actual
constructors?

[Dmitry Lomov (no reviews), 2015/02/03 15:47:04]

No, this only happens if var->binding_needs_init() and `this` does not need
intitalization outside of subclass constructors. Added an assert.

+          // 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);
@@ -3139,6 +3142,15 @@ void FullCodeGenerator::EmitSuperConstructorCall(Call* expr) {
   EmitLoadSuperConstructor(super_ref);
   __ push(result_register());
 
+  Variable* this_var = super_ref->this_var()->var();
+  GetVar(eax, this_var);
+  __ cmp(eax, isolate()->factory()->the_hole_value());
+  Label uninitialized_this;
+  __ j(equal, &uninitialized_this);
+  __ push(Immediate(this_var->name()));
+  __ CallRuntime(Runtime::kThrowReferenceError, 1);
+  __ bind(&uninitialized_this);
+
   // Push the arguments ("left-to-right") on the stack.
   ZoneList<Expression*>* args = expr->arguments();
   int arg_count = args->length();
@@ -3173,8 +3185,7 @@ void FullCodeGenerator::EmitSuperConstructorCall(Call* expr) {
 
   RecordJSReturnSite(expr);
 
-  // TODO(dslomov): implement TDZ for `this`.
-  EmitVariableAssignment(super_ref->this_var()->var(), Token::ASSIGN);
+  EmitVariableAssignment(this_var, Token::INIT_CONST);
   context()->Plug(eax);
 }