Closed generator returns a completed object instead of throwing a error

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 04a0f7fe75790bb931a649d15ff95f6083c6fde9..feec8f6e8b42f5ed55d9b1825f77adc66c55fd68 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -2074,19 +2074,21 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
     Expression *value,
     JSGeneratorObject::ResumeMode resume_mode) {
   // The value stays in eax, and is ultimately read by the resumed generator, as
-  // if the CallRuntime(Runtime::kSuspendJSGeneratorObject) returned it.  ebx
-  // will hold the generator object until the activation has been resumed.
+  // if the CallRuntime(Runtime::kSuspendJSGeneratorObject) returned it. Or used
+  // to throw the value when the resumed generator is already closed. ebx will

[wingo, 2014/01/13 13:44:49]

It's probably best to use a full sentence in the comment.  Code looks fine to me
though; nice catch. Let's cross fingers that the spec doesn't change yet again
:)

[yusukesuzuki, 2014/01/13 14:27:51]

Thanks for your review. Done. Is it OK? 

+  // hold the generator object until the activation has been resumed.
   VisitForStackValue(generator);
   VisitForAccumulatorValue(value);
   __ pop(ebx);
 
   // Check generator state.
-  Label wrong_state, done;
-  STATIC_ASSERT(JSGeneratorObject::kGeneratorExecuting <= 0);
-  STATIC_ASSERT(JSGeneratorObject::kGeneratorClosed <= 0);
+  Label wrong_state, closed_state, done;
+  STATIC_ASSERT(JSGeneratorObject::kGeneratorExecuting < 0);
+  STATIC_ASSERT(JSGeneratorObject::kGeneratorClosed == 0);
   __ cmp(FieldOperand(ebx, JSGeneratorObject::kContinuationOffset),
          Immediate(Smi::FromInt(0)));
-  __ j(less_equal, &wrong_state);
+  __ j(equal, &closed_state);
+  __ j(less, &wrong_state);
 
   // Load suspended function and context.
   __ mov(esi, FieldOperand(ebx, JSGeneratorObject::kContextOffset));
@@ -2156,6 +2158,20 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
   // Not reached: the runtime call returns elsewhere.
   __ Abort(kGeneratorFailedToResume);
 
+  // Reach here when generator is closed.
+  __ bind(&closed_state);
+  if (resume_mode == JSGeneratorObject::NEXT) {
+    // Return completed iterator result when generator is closed.
+    __ push(Immediate(isolate()->factory()->undefined_value()));
+    // Pop value from top-of-stack slot; box result into result register.
+    EmitCreateIteratorResult(true);
+  } else {
+    // Throw the provided value.
+    __ push(eax);
+    __ CallRuntime(Runtime::kThrow, 1);
+  }
+  __ jmp(&done);
+
   // Throw error if we attempt to operate on a running generator.
   __ bind(&wrong_state);
   __ push(ebx);