相关疑难解决方法(0)

该程序因无限递归而死亡:

use std::any::Any;

trait Foo {
    fn get(&self, index: usize) -> Option<&Any>;
}

impl Foo for Vec<i32> {
    fn get(&self, index: usize) -> Option<&Any> {
        Vec::get(self, index).map(|v| v as &Any)
    }
}

fn main() {
    let v: Vec<i32> = vec![1, 2, 4];
    println!("Results: {:?}", v.get(0))
}

编译器本身警告:

warning: function cannot return without recurring
  --> src/main.rs:8:5
   |
8  |       fn get(&self, index: usize) -> Option<&Any> {
   |  _____^ starting here...
9  | |         Vec::get(self, index).map(|v| v as &Any)
10 | | …

我想write_fmt在两种不同类型的对象上使用该方法:

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"));
}

我在使用时遇到错误,Write因为它们的名称相同:

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"));

或者我得到一个错误,说该特征不可用:

error[E0599]: no method named `write_fmt` found for type `std::fs::File` in the current scope
  --> src/main.rs:76:4
   | …