у использоватьwrite_fmt метод для двух разных типов объектов:

use std::fmt::Write;
use std::io::Write;

fn main() {
    let mut a = String::new();
    let mut b = std::fs::File::create("test").unwrap();

    a.write_fmt(format_args!("hello"));
    b.write_fmt(format_args!("hello"));
}

Я получаю ошибку при использованииWrite потому что они оба названы одинаково:

error[E0252]: a trait named `Write` has already been imported in this module
 --> src/main.rs:8:5
  |
7 | use std::fmt::Write;
  |     --------------- previous import of `Write` here
8 | use std::io::Write;
  |     ^^^^^^^^^^^^^^ `Write` already imported
      a.write_fmt(format_args!("hello"));
      b.write_fmt(format_args!("hello"));

Или я получаю сообщение о том, что черта недоступна:

error[E0599]: no method named `write_fmt` found for type `std::fs::File` in the current scope
  --> src/main.rs:76:4
   |
76 |    b.write_fmt(format_args!("hello"));
   |      ^^^^^^^^^
   |
   = help: items from traits can only be used if the trait is in scope; the following trait is implemented but not in scope, perhaps add a `use` for it:
   = help: candidate #1: `use std::io::Write;`