Remove an uneeded 'static lifetime

[steveklabnik]

Fixes #1744

[carols10cents]

@steveklabnik see this comment, in chapter 13 when we change this function to not take a reference anymore, we have to put the 'static in at that point and explain it there instead (and explain why the change makes us add it). is it literally just eliding the lifetimes and when we have an input lifetime, saying "oh static outlives that, so this is fine"? did this behavior change recently? i can't find a release notes entry that looks relevant... or have we not needed to specify 'static here for a long time?

[carols10cents]

needs more changes that i'm not sure how to make halp

[steveklabnik]

did this behavior change recently? i can't find a release notes entry that looks relevant... or have we not needed to specify 'static here for a long time?

I am not 100% sure, @Centril knows maybe?

[carols10cents]

Triage: this is still waiting on additional input/knowledge from somewhere/someone and then appropriate changes :-/

[Centril]

is it literally just eliding the lifetimes and when we have an input lifetime, saying "oh static outlives that, so this is fine"?

@carols10cents

Yes. After inference, the signature of the function is:

    fn new<'a, 'b>(args: &'a [String]) -> Result<Config, &'b str>;

When type checking "not enough arguments" we assign it the type &'static str; and for<'b> 'static: 'b holds so it conforms with the return type.

@steveklabnik

I am not 100% sure, @Centril knows maybe?

Using:

#![allow(dead_code)]

struct Config {
    query: String,
    filename: String,
}

impl Config {
    fn new(args: &[String]) -> Result<Config, &str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }

        let query = args[1].clone();
        let filename = args[2].clone();

        Ok(Config { query: query, filename: filename })
    }
}

I checked this with godbolt back to 1.0 and it has worked since then.

[steveklabnik]

Okay! I've rebased this.

[steveklabnik]

I don't know if we want to keep this sentence but remove the static lifetime bits. thoughts?

[stappersg]

For what it's worth:

• previous update was from 2020-04-02
• pre previous update was from 2019-04-22

What can / should be done to prevent that is pull request drags for another twelve months?

[carols10cents]

If you could stop the global pandemic, pay Steve or I to work on the book, provide childcare, or make more hours in the day, that would help.

Please be patient, your pings are not helpful.

[carols10cents]

@steveklabnik ok I think I've made the rest of the changes that need to be made for this PR; can you review what I've added? Also note I rebased and force pushed...

i fixed it

[steveklabnik]

Looks great! Since I opened the PR I can't approve it, haha.