function _attachContext(proxy, context, subProxy, descriptorDefaults) {
    const cache = {
        _cacheable: false,
        _proxy: proxy,
        _context: context,
        _subProxy: subProxy,
        _stack: new Set(),
        _descriptors: _descriptors(proxy, descriptorDefaults),
        setContext: (ctx)=>_attachContext(proxy, ctx, subProxy, descriptorDefaults),
        override: (scope)=>_attachContext(proxy.override(scope), context, subProxy, descriptorDefaults)
    };
    return new Proxy(cache, {
        /**
     * A trap for the delete operator.
     */ deleteProperty (target, prop) {
            delete target[prop]; // remove from cache
            delete proxy[prop]; // remove from proxy
            return true;
        },
        /**
     * A trap for getting property values.
     */ get (target, prop, receiver) {
            return _cached(target, prop, ()=>_resolveWithContext(target, prop, receiver));
        },
        /**
     * A trap for Object.getOwnPropertyDescriptor.
     * Also used by Object.hasOwnProperty.
     */ getOwnPropertyDescriptor (target, prop) {
            return target._descriptors.allKeys ? Reflect.has(proxy, prop) ? {
                enumerable: true,
                configurable: true
            } : undefined : Reflect.getOwnPropertyDescriptor(proxy, prop);
        },
        /**
     * A trap for Object.getPrototypeOf.
     */ getPrototypeOf () {
            return Reflect.getPrototypeOf(proxy);
        },
        /**
     * A trap for the in operator.
     */ has (target, prop) {
            return Reflect.has(proxy, prop);
        },
        /**
     * A trap for Object.getOwnPropertyNames and Object.getOwnPropertySymbols.
     */ ownKeys () {
            return Reflect.ownKeys(proxy);
        },
        /**
     * A trap for setting property values.
     */ set (target, prop, value) {
            proxy[prop] = value; // set to proxy
            delete target[prop]; // remove from cache
            return true;
        }
    });
}
Returns an Proxy for resolving option values with context.
@param proxy - The Proxy returned by `_createResolver`
@param context - Context object for scriptable/indexable options
@param subProxy - The proxy provided for scriptable options
@param descriptorDefaults - Defaults for descriptors
@private