A-lintL-restrictiongood first issue
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Description
What it does
Lints on any use of deref coercions - for example, accessing a field or method through a Deref impl
Categories (optional)
- Kind: Restriction lint
What is the advantage of the recommended code over the original code
Normally, deref coercions are a very useful part of rust, making smart points like Box, Rc, Ref, and RefMut much easier to use. However, this can be undesirable when writing unsafe code, since a non-trivial function call could be completely hidden from view. For example:
- Unsafe code can temporarily put data structures in an unusual state, which will lead to undefined behavior if dropped (e.g.
Vec::set_len). A deref coercion might cause a panic at an unexpected point (due to a panicking user-suppliedDerefimpl), leading to undefined behavior. - When mixing raw pointers and references, it's important to pay attention to the provenance of pointers. A deref coercion can hide the creation of an
&selfreference behind what looks like a normal field access, leading to a very subtle form of undefined behavior.
Drawbacks
This would be a fairly niche lint - unless you're writing unsafe code, there's little need to use it.
Example
fn main() {
let a = Box::new(true);
let b: &bool = &a;
}
Could be written as:
use std::ops::Deref;
fn main() {
let a = Box::new(true);
let b: &bool = (&a).deref();
}