Function define_property 

pub(crate) unsafe extern "C" fn define_property(
    cx: *mut JSContext,
    proxy: HandleObject,
    id: HandleId,
    desc: Handle<PropertyDescriptor>,
    result: *mut ObjectOpResult,
) -> bool

Defines an expando on the given proxy.

Safety

cx must point to a valid, non-null JSContext. result must point to a valid, non-null ObjectOpResult.