Re-use struct fields on drop; was: Drop(&mut self) vs. drop(self)

[literda]

@CAD97

but a #[derive(AfterDrop)] could be set up for this

Right, a derive covers almost everything except manually spelling out ManuallyDrop in the struct declaration. I did a first quick implementation and it works fine for me.

@scottmcm

Imagine, say, that you could do something like this:

impl DropPrime for Guard {
  fn drop_prime(Guard { resource }: Self) {
    do_something_more_with_precious_resource(resource);
  }
}

That’s already legal syntax. It correctly drops all the fields if you don’t put anything in the body, but it gives you ownership of them to move or forget as you wish. It wouldn’t even need the “you can’t call Drop::drop manually” restriction. (Just a separate ad-hoc restriction of “you must destructure in the parameter-pattern”.)

Thanks, I like that idea very much, I'll look into this.