New lint to minimize the unsafe block scope.

What it does

Checks for unsafe blocks that contain safe code, which can be extracted to the outside safe code.

Categories (optional)

• Kind: pedantic

Rust doesn't enforce memory safety guarantees in unsafe blocks. Having more code inside the unsafe block than necessary, might result in bugs which could be avoided by having the code in the save-code-scope. It also clearly indicates which part of an operation is unsafe.

Drawbacks

Using the smallest unsafe code block possible might be less readable.

Example

unsafe {
    let mut vec: Vec<u8> = Vec::with_capacity(128);
    vec.set_len(100);
    println!("{:#?}", vec);
}

Could be written as:

let mut vec: Vec<u8> = Vec::with_capacity(128);
unsafe {
     vec.set_len(100);
}
println!("{:#?}", vec);

No implementation files, tests, or entry points are named. Start from the unsafe-block examples and define which safe statements may move outside the block, including the readability drawback. Done means the proposed lint consistently identifies unnecessary safe code inside unsafe blocks without flagging the intentionally grouped case.