Comment by steveklabnik

Not your parent, but there are two ways:

1. If you use a custom deleter, then there's extra stuff to store that. this isn't common, and this API isn't available in Rust, so... not the best argument here.

2. There's ABI requirements that cause it to be passed in memory, see here for details: https://stackoverflow.com/questions/58339165/why-can-a-t-be-...