Move generator-close on exception from the generator function to the GeneratorResume builtin.

src/builtins/builtins-generator-gen.cc

Index: src/builtins/builtins-generator-gen.cc
diff --git a/src/builtins/builtins-generator-gen.cc b/src/builtins/builtins-generator-gen.cc
index b011f1e5cd724725dd034968fdcfd5d2b1be48b7..49bb5d5f0a1749eb0b8d9f3d26a26994cdfdde88 100644
--- a/src/builtins/builtins-generator-gen.cc
+++ b/src/builtins/builtins-generator-gen.cc
@@ -47,12 +47,32 @@ void GeneratorBuiltinsAssembler::GeneratorPrototypeResume(
   GotoIf(SmiLessThan(receiver_continuation, closed), &if_receiverisrunning);
 
   // Resume the {receiver} using our trampoline.
+  VARIABLE(var_exception, MachineRepresentation::kTagged, UndefinedConstant());
+  Label if_exception(this, Label::kDeferred), if_final_return(this);
   Node* result =
       CallStub(CodeFactory::ResumeGenerator(isolate()), context, value,
                receiver, SmiConstant(resume_mode),
                SmiConstant(static_cast<int>(SuspendFlags::kGeneratorYield)));
+  // Make sure we close the generator if there was an exception.
+  GotoIfException(result, &if_exception, &var_exception);
+
+  // If the generator is not suspended (i.e., it's state is 'closed'),
+  // wrap the return value in IteratorResult.
+  Node* result_continuation =
+      LoadObjectField(receiver, JSGeneratorObject::kContinuationOffset);
+  GotoIf(SmiEqual(result_continuation, closed), &if_final_return);
   Return(result);
 
+  Callable create_iter_result_object =
+      CodeFactory::CreateIterResultObject(isolate());
+
+  BIND(&if_final_return);
+  {
+    // Return the wrapped result.
+    Return(
+        CallStub(create_iter_result_object, context, result, TrueConstant()));
+  }
+
   BIND(&if_receiverisincompatible);
   {
     // The {receiver} is not a valid JSGeneratorObject.
@@ -65,9 +85,6 @@ void GeneratorBuiltinsAssembler::GeneratorPrototypeResume(
 
   BIND(&if_receiverisclosed);
   {
-    Callable create_iter_result_object =
-        CodeFactory::CreateIterResultObject(isolate());
-
     // The {receiver} is closed already.
     Node* result = nullptr;
     switch (resume_mode) {
@@ -91,6 +108,14 @@ void GeneratorBuiltinsAssembler::GeneratorPrototypeResume(
     CallRuntime(Runtime::kThrowGeneratorRunning, context);
     Unreachable();
   }
+
+  BIND(&if_exception);
+  {
+    StoreObjectFieldNoWriteBarrier(
+        receiver, JSGeneratorObject::kContinuationOffset, closed);
+    CallRuntime(Runtime::kReThrow, context, var_exception.value());
+    Unreachable();
+  }
 }
 
 // ES6 #sec-generator.prototype.next