[async-iteration] implement Async-from-Sync Iterator

src/objects.h

 // Copyright 2015 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 #include <memory>
 
@@ skipping 380 matching lines @@
   V(JS_SET_TYPE)                                                \
   V(JS_MAP_TYPE)                                                \
   V(JS_SET_ITERATOR_TYPE)                                       \
   V(JS_MAP_ITERATOR_TYPE)                                       \
   V(JS_WEAK_MAP_TYPE)                                           \
   V(JS_WEAK_SET_TYPE)                                           \
   V(JS_PROMISE_CAPABILITY_TYPE)                                 \
   V(JS_PROMISE_TYPE)                                            \
   V(JS_REGEXP_TYPE)                                             \
   V(JS_ERROR_TYPE)                                              \
+  V(JS_ASYNC_FROM_SYNC_ITERATOR_TYPE)                           \
   V(JS_STRING_ITERATOR_TYPE)                                    \
                                                                 \
   V(JS_TYPED_ARRAY_KEY_ITERATOR_TYPE)                           \
   V(JS_FAST_ARRAY_KEY_ITERATOR_TYPE)                            \
   V(JS_GENERIC_ARRAY_KEY_ITERATOR_TYPE)                         \
                                                                 \
   V(JS_UINT8_ARRAY_KEY_VALUE_ITERATOR_TYPE)                     \
   V(JS_INT8_ARRAY_KEY_VALUE_ITERATOR_TYPE)                      \
   V(JS_UINT16_ARRAY_KEY_VALUE_ITERATOR_TYPE)                    \
   V(JS_INT16_ARRAY_KEY_VALUE_ITERATOR_TYPE)                     \
@@ skipping 325 matching lines @@
   JS_SET_TYPE,
   JS_MAP_TYPE,
   JS_SET_ITERATOR_TYPE,
   JS_MAP_ITERATOR_TYPE,
   JS_WEAK_MAP_TYPE,
   JS_WEAK_SET_TYPE,
   JS_PROMISE_CAPABILITY_TYPE,
   JS_PROMISE_TYPE,
   JS_REGEXP_TYPE,
   JS_ERROR_TYPE,
+  JS_ASYNC_FROM_SYNC_ITERATOR_TYPE,
   JS_STRING_ITERATOR_TYPE,
 
   JS_TYPED_ARRAY_KEY_ITERATOR_TYPE,
   JS_FAST_ARRAY_KEY_ITERATOR_TYPE,
   JS_GENERIC_ARRAY_KEY_ITERATOR_TYPE,
 
   JS_UINT8_ARRAY_KEY_VALUE_ITERATOR_TYPE,
   JS_INT8_ARRAY_KEY_VALUE_ITERATOR_TYPE,
   JS_UINT16_ARRAY_KEY_VALUE_ITERATOR_TYPE,
   JS_INT16_ARRAY_KEY_VALUE_ITERATOR_TYPE,
@@ skipping 276 matching lines @@
   V(SharedFunctionInfo)          \
   V(JSValue)                     \
   V(JSDate)                      \
   V(JSMessageObject)             \
   V(StringWrapper)               \
   V(Foreign)                     \
   V(Boolean)                     \
   V(JSArray)                     \
   V(JSArrayBuffer)               \
   V(JSArrayBufferView)           \
+  V(JSAsyncFromSyncIterator)     \
   V(JSCollection)                \
   V(JSTypedArray)                \
   V(JSArrayIterator)             \
   V(JSDataView)                  \
   V(JSProxy)                     \
   V(JSError)                     \
   V(JSPromiseCapability)         \
   V(JSPromise)                   \
   V(JSStringIterator)            \
   V(JSSet)                       \
@@ skipping 9367 matching lines @@
 
   static const int kIteratedObjectOffset = JSObject::kHeaderSize;
   static const int kNextIndexOffset = kIteratedObjectOffset + kPointerSize;
   static const int kIteratedObjectMapOffset = kNextIndexOffset + kPointerSize;
   static const int kSize = kIteratedObjectMapOffset + kPointerSize;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSArrayIterator);
 };
 
+// The [Async-from-Sync Iterator] object
+// (proposal-async-iteration/#sec-async-from-sync-iterator-objects)
+// An object which wraps an ordinary Iterator and converts it to behave
+// according to the Async Iterator protocol.
+// (See https://tc39.github.io/proposal-async-iteration/#sec-iteration)
+class JSAsyncFromSyncIterator : public JSObject {
+ public:
+  DECLARE_CAST(JSAsyncFromSyncIterator)
+  DECLARE_PRINTER(JSAsyncFromSyncIterator)
+  DECLARE_VERIFIER(JSAsyncFromSyncIterator)
+
+  // Async-from-Sync Iterator instances are ordinary objects that inherit
+  // properties from the %AsyncFromSyncIteratorPrototype% intrinsic object.
+  // Async-from-Sync Iterator instances are initially created with the internal
+  // slots listed in Table 4.
+  // (proposal-async-iteration/#table-async-from-sync-iterator-internal-slots)
+  DECL_ACCESSORS(sync_iterator, JSReceiver)
+
+  // Offsets of object fields.
+  static const int kSyncIteratorOffset = JSObject::kHeaderSize;
+  static const int kSize = kSyncIteratorOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(JSAsyncFromSyncIterator);
+};
+
 class JSStringIterator : public JSObject {
  public:
   // Dispatched behavior.
   DECLARE_PRINTER(JSStringIterator)
   DECLARE_VERIFIER(JSStringIterator)
 
   DECLARE_CAST(JSStringIterator)
 
   // [string]: the [[IteratedString]] internal field.
   DECL_ACCESSORS(string, String)
@@ skipping 1079 matching lines @@
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #include "src/objects/object-macros-undef.h"
 
 #endif  // V8_OBJECTS_H_