`drop` without `Drop`

[AiyionPrime]

Hey @einarmo? What is the drop statement in line 73 supposed to do there? Doesn't that only work on types implementing Drop?

The type of activate_fut is std::pin::Pin<&mut impl futures::Future<Output = std::result::Result<client::session::connect::SessionConnectMode, types::status_codes::StatusCode>>>,

which is not Drop; does this do something I just don't get?

https://github.com/locka99/opcua/blob/8cc43e51fe2d14a965d271059aa031c89440fc30/lib/src/client/session/connect.rs#L44-L73

[einarmo]

I think I did this because it didn't compile at some point, but it seems fine now, I can't remember why I did it now. You sometimes get this kind of error, where the default drop-order of values in a method causes a compiler error. The compiler is almost always smart enough to realize that it can drop values early, but you occasionally get an error which requires you to manually drop a value before the end of the function. That might have happened here.

As for your question, std::mem::drop works fine on types that don't explicitly implement Drop. Every type has a destructor, which recursively calls drop on all its members, drop ends up invoking that.

Drop isn't the destructor, it's more like a callback that runs before the destructor runs. Confusingly we just call destroying a value for "dropping" in rust.

[einarmo]

This specific instance of drop can be removed, unless it causes issues.