ref_option_ref should not trigger for mutable references

[michalburger1]

Summary

The lint tells you to use Option<&T> instead of &Option<&T> because the former is Copy so there's no point in passing around references. However, the lint seems to also triggers for &Option<&mut T> and tells you to use Option<&mut T> instead, which is not Copy.

Lint Name

ref_option_ref

Reproducer

I tried this code:

fn foo(arg: &Option<&mut String>) {
    println!("{:?}", arg);
}

I saw this happen:

since `&` implements the `Copy` trait, `&Option<&T>` can be simplified to `Option<&T>`

I expected to see this happen:

No lint warnings.

Version

rustc 1.64.0 (a55dd71d5 2022-09-19)
binary: rustc
commit-hash: a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52
commit-date: 2022-09-19
host: x86_64-pc-windows-msvc
release: 1.64.0
LLVM version: 14.0.6

Additional Labels

@rustbot label +l-suggestion-causes-error

[rustbot]

Error: Label l-suggestion-causes-error can only be set by Rust team members

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[michalburger1]

Applying the suggestion would cause an error if you're also trying to use the value in other places (it can't be copied so it will be moved).

[kraktus]

Can't reproduce on nightly so I assume it's been fixed

[Alexendoo]

It's a pedantic lint so you'll need to enable it

[kraktus]

right my bad!

@rustbot claim