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diff --git a/src/bun.js/bindings/webcore/JSValueInWrappedObject.h b/src/bun.js/bindings/webcore/JSValueInWrappedObject.h
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+++ b/src/bun.js/bindings/webcore/JSValueInWrappedObject.h
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2018-2021 Apple Inc. All rights reserved.
+
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "DOMWrapperWorld.h"
+#include "JSDOMWrapper.h"
+#include "JavaScriptCore/JSCJSValue.h"
+#include "JavaScriptCore/SlotVisitor.h"
+#include "JavaScriptCore/Weak.h"
+#include <variant>
+
+namespace WebCore {
+
+// This class includes a lot of GC related subtle things, and changing this class easily causes GC crashes.
+// Any changes on this class must be reviewed by JavaScriptCore reviewers too.
+class JSValueInWrappedObject {
+    // It must be neither copyable nor movable. Changing this will break concurrent GC.
+    WTF_MAKE_NONCOPYABLE(JSValueInWrappedObject);
+    WTF_MAKE_NONMOVABLE(JSValueInWrappedObject);
+
+public:
+    JSValueInWrappedObject(JSC::JSValue = {});
+
+    explicit operator bool() const;
+    template<typename Visitor> void visit(Visitor&) const;
+    void clear();
+
+    void set(JSC::VM&, const JSC::JSCell* owner, JSC::JSValue);
+    void setWeakly(JSC::JSValue);
+    JSC::JSValue getValue(JSC::JSValue nullValue = JSC::jsUndefined()) const;
+
+    // FIXME: Remove this once IDBRequest semantic bug is fixed.
+    // https://bugs.webkit.org/show_bug.cgi?id=236278
+    void setWithoutBarrier(JSValueInWrappedObject&);
+
+private:
+    // Keep in mind that all of these fields are accessed concurrently without lock from concurrent GC thread.
+    JSC::JSValue m_nonCell {};
+    JSC::Weak<JSC::JSCell> m_cell {};
+};
+
+JSC::JSValue cachedPropertyValue(JSC::JSGlobalObject&, const JSDOMObject& owner, JSValueInWrappedObject& cacheSlot, const Function<JSC::JSValue()>&);
+
+inline JSValueInWrappedObject::JSValueInWrappedObject(JSC::JSValue value)
+{
+    setWeakly(value);
+}
+
+inline JSC::JSValue JSValueInWrappedObject::getValue(JSC::JSValue nullValue) const
+{
+    if (m_nonCell)
+        return m_nonCell;
+    return m_cell ? m_cell.get() : nullValue;
+}
+
+inline JSValueInWrappedObject::operator bool() const
+{
+    return m_nonCell || m_cell;
+}
+
+template<typename Visitor>
+inline void JSValueInWrappedObject::visit(Visitor& visitor) const
+{
+    visitor.append(m_cell);
+}
+
+template void JSValueInWrappedObject::visit(JSC::AbstractSlotVisitor&) const;
+template void JSValueInWrappedObject::visit(JSC::SlotVisitor&) const;
+
+inline void JSValueInWrappedObject::setWeakly(JSC::JSValue value)
+{
+    if (!value.isCell()) {
+        m_nonCell = value;
+        m_cell.clear();
+        return;
+    }
+    m_nonCell = {};
+    JSC::Weak weak { value.asCell() };
+    WTF::storeStoreFence();
+    m_cell = WTFMove(weak);
+}
+
+inline void JSValueInWrappedObject::set(JSC::VM& vm, const JSC::JSCell* owner, JSC::JSValue value)
+{
+    setWeakly(value);
+    vm.writeBarrier(owner, value);
+}
+
+inline void JSValueInWrappedObject::clear()
+{
+    m_nonCell = {};
+    m_cell.clear();
+}
+
+inline void JSValueInWrappedObject::setWithoutBarrier(JSValueInWrappedObject& other)
+{
+    JSC::Weak weak { other.m_cell.get() };
+    WTF::storeStoreFence(); // Ensure Weak is fully initialized for concurrent access.
+    m_nonCell = other.m_nonCell;
+    m_cell = WTFMove(weak);
+}
+
+inline JSC::JSValue cachedPropertyValue(JSC::JSGlobalObject& lexicalGlobalObject, const JSDOMObject& owner, JSValueInWrappedObject& cachedValue, const Function<JSC::JSValue()>& function)
+{
+    if (cachedValue && isWorldCompatible(lexicalGlobalObject, cachedValue.getValue()))
+        return cachedValue.getValue();
+    auto value = function();
+    cachedValue.set(lexicalGlobalObject.vm(), &owner, cloneAcrossWorlds(lexicalGlobalObject, owner, value));
+    ASSERT(isWorldCompatible(lexicalGlobalObject, cachedValue.getValue()));
+    return cachedValue.getValue();
+}
+
+} // namespace WebCore