预期类型 `Method` 找到枚举 `Result<_, MethodError>`

Question

我正在尝试将 &str 转换为 enum，但在 Err(e) => Err(e) 这行出现错误 Expected type Method found enum Result<_, MethodError>。在这种情况下如何正确 return 出错？

use std::str::FromStr;

fn main() {

#[derive(Debug)]
pub enum Method {
    GET,
    DELETE,
    POST,
    PUT,
    HEAD,
    CONNECT,
    OPTIONS,
    TRACE,
    PATCH,
}

impl FromStr for Method {
    type Err = MethodError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "GET" => Ok(Self::GET),
            "DELETE" => Ok(Self::DELETE),
            "POST" => Ok(Self::POST),
            "PUT" => Ok(Self::PUT),
            "HEAD" => Ok(Self::HEAD),
            "CONNECT" => Ok(Self::CONNECT),
            "OPTIONS" => Ok(Self::OPTIONS),
            "TRACE" => Ok(Self::TRACE),
            "PATCH" => Ok(Self::PATCH),
            _ => Err(MethodError),
        }
    }
}

pub struct MethodError;

let method:&str = "GET";

let methodE =  match method.parse::<Method>() {
    Ok(method) => method,
    Err(e) => Err(e),
};
}

Answer 1

感谢大家的意见，我想通了：

main 需要 return Result<(), MethodError>
return 匹配臂中需要关键字 Err(e) => return Err(e)

use std::str::FromStr;

#[derive(Debug)]
pub enum Method {
    GET,
    DELETE,
    POST,
    PUT,
    HEAD,
    CONNECT,
    OPTIONS,
    TRACE,
    PATCH,
}

impl FromStr for Method {
    type Err = MethodError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "GET" => Ok(Self::GET),
            "DELETE" => Ok(Self::DELETE),
            "POST" => Ok(Self::POST),
            "PUT" => Ok(Self::PUT),
            "HEAD" => Ok(Self::HEAD),
            "CONNECT" => Ok(Self::CONNECT),
            "OPTIONS" => Ok(Self::OPTIONS),
            "TRACE" => Ok(Self::TRACE),
            "PATCH" => Ok(Self::PATCH),
            _ => Err(MethodError),
        }
    }
}

#[derive(Debug)]
pub struct MethodError;

fn main() -> Result<(), MethodError> {
  let method:&str = "GET";
  
  let methodE =  match method.parse::<Method>() {
      Ok(method) => method,
      Err(e) => return Err(e),
  };
  
  // this works too: let methodE: Method =  method.parse()?;
  
  Ok(())
}

预期类型 `Method` 找到枚举 `Result<_, MethodError>`

Expected type `Method` found enum `Result<_, MethodError>`

rust

main