Calling a generator function returns a generator object

src/objects-debug.cc

Index: src/objects-debug.cc
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index 44cab53cc7ae90696e7c34929084e0e6e1e318bd..77c8075fe71eb6094743703d08981d3d0ffc6979 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -139,6 +139,9 @@ void HeapObject::HeapObjectVerify() {
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
       JSObject::cast(this)->JSObjectVerify();
       break;
+    case JS_GENERATOR_OBJECT_TYPE:
+      JSGeneratorObject::cast(this)->JSGeneratorObjectVerify();
+      break;
     case JS_MODULE_TYPE:
       JSModule::cast(this)->JSModuleVerify();
       break;
@@ -404,6 +407,24 @@ void FixedDoubleArray::FixedDoubleArrayVerify() {
 }
 
 
+void JSGeneratorObject::JSGeneratorObjectVerify() {
+  VerifyObjectField(kFunctionOffset);
+  VerifyObjectField(kContextOffset);
+  VerifyObjectField(kOperandStackOffset);
+  if (function()->IsUndefined()) {

[Michael Starzinger, 2013/04/14 21:32:50]

Just out of curiosity, is there a particular reason we are using Smi(0) as a
sentinel value instead of undefined? I would be fine with switching to undefined
as well. I'll leave that up to you.

[wingo, 2013/04/15 09:24:57]

Changed to use undefined.  I also relaxed these checks, as it's inconvenient to
type accessors while still allowing for that strange "might-be-undefined" moment
for the Smi and FixedArray fields.

+    // Uninitialized object from constructor.
+    CHECK(context()->IsUndefined());
+    CHECK(operand_stack()->IsUndefined());
+  } else {
+    CHECK(context() == Smi::FromInt(0) || context()->IsContext());
+    VerifySmiField(kContinuationOffset);
+    CHECK_GE(continuation(), 0);
+    CHECK(operand_stack() == Smi::FromInt(0) ||
+          operand_stack()->IsFixedArray());
+  }
+}
+
+
 void JSModule::JSModuleVerify() {
   VerifyObjectField(kContextOffset);
   VerifyObjectField(kScopeInfoOffset);