Can we make a &mut str?

1

Seems impossible by specifying the type directly:

fn main() {
    let a:&mut str = "".into();
}
2

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.)

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3

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");

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4

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

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5

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.)

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