Why does the Rust Language Server not warn about expected &str, found struct std::string::String?

Question

The following code raises an error in all channels. The Rust Language Server does not detect this error and says the types are correct. What did I get wrong?

use std::fs::File;
use std::io::Read;
use std::io::Write;
use std::env;
use std::string::String;
use std::str;

fn main() {
    if let Some(file_name) = env::args().nth(2) {
        let mut file_handle = File::open(file_name)
            .expect(format!("Your File is invaild {}", &file_name as &str));
        let mut text = String::new();
        file_handle
            .read_to_string(&mut text)
            .expect("unable to read file");
        text.replace("test", &env::args().nth(2).unwrap() as &str);
        // file_handle.set_len(text.len() as u64).expect("could not resize file");
        file_handle
            .write(&text.as_bytes())
            .expect("could not write to file");
    } else {
        println!("you did not give me a file")
    }
}

error[E0308]: mismatched types
  --> src/main.rs:11:21
   |
11 |             .expect(format!("Your File is invaild {}", &file_name as &str));
   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected &str, found struct `std::string::String`
   |
   = note: expected type `&str`
              found type `std::string::String`