function that returns `()` | = help: the trait `std::ops::Try` is not implemented for `()` = note: required by `std::ops::Try::from_error` 错误指出只能在返回Result或者其它实现了std::ops::Try的类型的函数中使用?运算符。当你期望在不返回Result的函数中调用其他返回Result的函数时使用?的...
match result { Ok(v) => v, Err(e) => return Err(e.into()) } 使用方式如下 use std::fs::File; use std::io::Read; fn read_file(name: &str) -> Result<String, std::io::Error> { let mut f = File::open(name)?; // 这里加了 ? 符号,如果发生错误会进行错误传播 let mut...
` operator in a function that returns `()` | = help: the trait `std::ops::Try` is not implemented for `()` = note: required by `std::ops::Try::from_error` 错误指出只能在返回 Result 或者其它实现了 std::ops::Try 的类型的函数中使用 ? 运算符。当你期望在不返回 Result 的函数中...
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`) --> src/main.rs:4:13 | 4 | let f = File::open("hello.txt")?; | ^^^ cannot use the `?` operator in a function that retu...
因此一个Go程序代码中会有大量的iferr!= nil {returnerr;}。 Rust中没有异常,对于可恢复错误使用了类型Result,即函数返回的错误信息通过类型系统描述。对于在程序遇到不可恢复的错误时panic!时停止执行 1. Result和可恢复错误 Result是一个枚举类型,其定义如下: ...
` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)--> src/main.rs:4:48|3 | fn main() {| --- this function should return `Result` or `Option` to accept `?`4 | let greeting_file = File::open("hello....
` operator can only be used in a function that returns `Result` (or another type that implements `std::ops::Try`) | in this macro invocation | = help: the trait `std::ops::Try` is not implemented for `()` = note: required by `std::ops::Try::from_error`...
enumApiError{BadRequest,Forbidden,Unauthorised,InternalServerError}// ... 省略ApiResponse的代码asyncfnmy_function()->Result<ApiResponse,ApiError>{//} 这样我们的路由就可以区分错误和成功的请求了。 3. 在 Axum 中添加数据库 在Rust中使用数据库,那么sqlx[7]肯定是绕不过的。
error[E0308]:mismatched types-->src/main.rs:7:18|7|modify_value(&value);// 将不可变引用传递给函数|---^^^types differinmutability|||arguments tothisfunctionare incorrect|=note:expected mutable reference`&mut i32`found reference`&{integer}`note:functiondefined here-->src/main.rs:1:4|1|...
如何从Rust中的函数返回值推断Return〈T，E>值的类型？可以使用_placeholder来推断Result的Err变体的类型...