error[E0106]: missing lifetime specifier (despite it being set) [duplicate]

问题

This question already has answers here:

Contradictory “missing lifetime specifier” error on owned value [duplicate] (1 answer)

Getting 'Missing Lifetime specifier' error (1 answer)

Why do I get “missing lifetime specifier” or “wrong number of type arguments” when implementing a trait for a struct? (1 answer)

Closed 2 years ago.

Consider the following code:

extern crate clap;
use clap::{App};

use std::io;

fn parse_argv() -> &'static clap::ArgMatches {
    return App::new("example")
    .get_matches()
}

fn main() -> io::Result<()> {

    let matches = parse_argv();

    Ok(())
}

This is the error:

error[E0106]: missing lifetime specifier                                                                                                                                                                                                                                                                                                                                   
 --> src/main.rs:6:29                                                                                                                                                                                                                                                                                                                                                      
  |                                                                                                                                                                                                                                                                                                                                                                        
6 | fn parse_argv() -> &'static clap::ArgMatches {                                                                                                                                                                                                                                                                                                                         
  |                             ^^^^^^^^^^^^^^^^ help: consider giving it a 'static lifetime: `clap::ArgMatches + 'static`                                                                                                                                                                                                                                                 
  |                                                                                                                                                                                                                                                                                                                                                                        
  = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from

What is the problem here and how do I solve it? I think I did what compiler asked for, but the error won't disappear.

回答1:

I got an answer on #rust-beginners IRC channel:

13:10:17 drager | d33tah: I suspect that ArgMatches actually wants the lifetime, so ArgMatches<'static> in this case

So, the solution was to change the function signature to:

fn parse_argv() -> clap::ArgMatches<'static> {

来源：https://stackoverflow.com/questions/54217705/errore0106-missing-lifetime-specifier-despite-it-being-set