Static rustc_lint_defs::builtin::DEPRECATED_SAFE_2024

pub static DEPRECATED_SAFE_2024: &Lint

The deprecated_safe_2024 lint detects unsafe functions being used as safe functions.

Example

#![deny(deprecated_safe)]
// edition 2021
use std::env;
fn enable_backtrace() {
    env::set_var("RUST_BACKTRACE", "1");
}

{{produces}}

Explanation

Rust editions allow the language to evolve without breaking backward compatibility. This lint catches code that uses unsafe functions that were declared as safe (non-unsafe) in editions prior to Rust 2024. If you switch the compiler to Rust 2024 without updating the code, then it will fail to compile if you are using a function previously marked as safe.

You can audit the code to see if it suffices the preconditions of the unsafe code, and if it does, you can wrap it in an unsafe block. If you can’t fulfill the preconditions, you probably need to switch to a different way of doing what you want to achieve.

This lint can automatically wrap the calls in unsafe blocks, but this obviously cannot verify that the preconditions of the unsafe functions are fulfilled, so that is still up to the user.

The lint is currently “allow” by default, but that might change in the future.