I noticed the rust book recommends to use Rc::clone(&rc) over rc.clone() as follows:
use std::rc::Rc;
let five = Rc::new(5);
// recommended
let _ = Rc::clone(&five);
// not recommended
let _ = five.clone();
Why?
Is there any difference between Rc::clone(&rc) and rc.clone() in Rust? Is there any compilation optimizations happen based on that?
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1 Answers
The function syntax (Rc::clone(&rc)) makes it clear you're only making a new shared reference (cheap), rather than cloning the underlying object being referenced (maybe expensive). For arbitrary reference counted types, it may not be clear if a shallow or deep copy is occurring.
This issue with readability/clarity has led to proposals for a separate interface for cloning reference counted pointer types, with linters now warning when a reference counted type is cloned via a method.
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