相关疑难解决方法(0)

我想在Rust中为一个闭包声明一个生命周期,但我找不到添加生命周期声明的方法.

use std::str::SplitWhitespace;

pub struct ParserError {
    pub message: String,
}

fn missing_token(line_no: usize) -> ParserError {
    ParserError {
        message: format!("Missing token on line {}", line_no),
    }
}

fn process_string(line: &str, line_number: usize) -> Result<(), ParserError> {
    let mut tokens = line.split_whitespace();

    match try!(tokens.next().ok_or(missing_token(line_number))) {
        "hi" => println!("hi"),
        _ => println!("Something else"),
    }

    // The following code gives "cannot infer appropriate lifetime.....
    // let nt = |t: &mut SplitWhitespace| t.next().ok_or(missing_token(line_number));
    // match try!(nt(&mut tokens)) {
    //     "there" => println!("there"),
    // …

我对下面的生命周期发生了什么感到困惑：

struct Foo{}
impl Foo {
    fn foo(&self, _s: &str) {}
}

fn main() {
    let foo = &Foo{};
    let closure = |s| foo.foo(s);

    // Part 1: error message about wrong lifetime in FnOnce
    take_closure(closure); 

    // Part 2: no error when inlined
    take_closure(|s| foo.foo(s));

    // Part 3: no error when `dyn`d and given explicit signature
    let closure: &dyn Fn(&str) -> _ = &|s| foo.foo(s);
    take_closure(closure);
}

fn take_closure(f: impl Fn(&str) -> ()) {
    let s = get_string();
    f(&s)
}

fn …

虽然下面的代码是一个早期的原型,并且不要过于认真地考虑我在这个阶段如何实现协议缓冲区,但我无法理解生锈编译器带来的错误信息.

src\main.rs:89:9:89:36错误:类型不匹配解析for<'r> <[closure src\ma in.rs:75:33: 88:10] as core::ops::FnOnce<(u32, gpb::definitions::WireType, &'r collections::vec::Vec<u8>, usize)>>::Output == usize:期望绑定生存期参数,找到具体生存期[E0271] src\main.rs:89 gpb :: decoding :: read_message(source,field_handler);

即使在阅读了有关lifetimes等的3篇文章章节之后.人.我没有遇到"具体的生命周期"这个术语,因此无法弄清楚这个错误与哪些代码有关.闭包本身,一个或多个参数,返回码？关闭的通过 read_message()？...

main.rs片段

fn from_gpb( source : &Vec<u8>) -> TimeMessage {
    fn init_vec_u64( count : usize, init_value : u64) -> Vec<u64> {
        let mut result = Vec::<u64>::with_capacity(count);
        for i in 0..count {
            result.push(init_value);
        }
        result
    }
    let mut message_id : u32 = 0;
    let mut times_sec  = init_vec_u64(4,0u64);
    let mut times_usec = init_vec_u64(4,0u64);
    let mut max_time_index = …