rust-clippy | catch common mistakes and improve your Rust code | Code Analyzer library

You can wrap a trait object in a Rc as well, since Rc is also a pointer.

Therefore if you have Rc>, you have two allocations: One for the T and one for the Box (another pointer, that now is on the heap). Instead, use Rc to only have one allocation.

Use rustup default to change the default toolchain. You can use the full name (e.g. rustup default stable-x86_64-unknown-linux-gnu) or a short alias (e.g. rustup default stable).

rustup also has methods to override the default in a more scoped manner. See Override precedence in rustup's README.

Calling arc_taker(arc.clone()) increments the reference count, and returning from arc_taker decrements it again. This is useless in this case, since the arc variable of main already keeps the Arc alive during the entire call. A reference to it would already suffice. No need to bump the reference count up and down.

In your specific example, arc_taker doesn't even care that it is managed by an Arc. All it cares about is that there is a Mutex to lock, so to make your function less restrictive, just take a &Mutex instead.

If you wanted to do any Arc-specific things to it, like getting the weak_count or something, taking a &Arc<..> would make sense. If your function would keep a clone of the Arc around, only then it would make sense to take an Arc by value, because then the caller can decide to give you an additional reference to it by calling .clone() (thus bumping the reference count), or to give you ownership of its own Arc (and thus not bumping the reference count).

The docs state you can allow or deny lints.

Yes, these are the same to the compiler. In this case, there's not much benefit. The real benefit comes from the match equivalent:

You can pass a reference to an Arc's content instead.

Use clone_from_slice

There are two ways to use Clippy: the cargo clippy command and the clippy compiler plugin. cargo clippy detects the build script as a dependency of the main project, so it doesn't load the compiler plugin.

Therefore, the other option is to use the compiler plugin directly. The instructions for doing this are in clippy's README. We need to make a few adaptations for using it on the build script, though.

First, we need to add clippy as a build dependency: