Can we make a &mut str?

Seems impossible by specifying the type directly:

fn main() {
    let a:&mut str = "".into();

Why would you expect a string literal to be mutable?

You can make a &mut str by mutably borrowing a String. However, due to the requirement of strings being valid UTF-8, a mutable str is basically useless (you can't push onto its end, so all you can do with it is unsafely manipulating its bytes, which you shouldn't do.)

1 Like

I'm afraid you must use something like let a: &mut str = String::from("hello").as_mut_str(); or let a: &mut str = &mut String::from("hello");

1 Like

There are some safe operations you can make on a &mut str, for example:


For the empty string specifically, you can

let _: &'static mut str = std::str::from_utf8_mut(<_>::default()).unwrap();

(As a special case, an empty &mut [] of any type and lifetime can be conjured, as it points to no memory.)


This topic was automatically closed 90 days after the last reply. We invite you to open a new topic if you have further questions or comments.