What you say makes sense... but I struggle to reconcile it with reality.
If "the left part of this bound can live up to the end of the application" then why is &a not 'a where 'a: 'static? a can live up to the end of the application. &a can live up to the end of the application.
Why is the result "argument requires that `a` is borrowed for `'static`"
fn foo<'a: 'static>(a: &'a str) { println!("{}", a) }
pub fn main() {
let a = "hello world".to_string();
foo(&a);
}
So I guess I'm going to have to just agree to disagree on this one and bow out of this conversation thread I'm afraid.
If you do 'a: 'static, then you just said 'a is at least as long as 'static.
When you borrow the String, you just created a lifetime that is not as long as 'static. Variables are dropped (and hence unborrowed) in reverse order. So 'a will necessarily be dropped before its owner, hence it's shorter than 'static.
As you can see it complains that it's dropped at the end of main() even though it should be borrowed for 'static. If this was an owned value it would NOT be dropped at main() since it would be moved into the function on call.
Nothing surprising here.
> &a can live up to the end of the application
Nope. Imagine spawning a thread and passing &a but keeping 'a' in your main thread.
> a can live up to the end of the application. &a can live up to the end of the application.
Nope, a reference to a stack frame can't live up to the end of the application. The stack frame gets deallocated and the referent ceases to exist; therefore the reference you're creating in your linked example doesn't outlive 'static. `main` is not an exception to this in Rust.
If "the left part of this bound can live up to the end of the application" then why is &a not 'a where 'a: 'static? a can live up to the end of the application. &a can live up to the end of the application.
Why is the result "argument requires that `a` is borrowed for `'static`"
So I guess I'm going to have to just agree to disagree on this one and bow out of this conversation thread I'm afraid.[1] -- https://play.rust-lang.org/?version=stable&mode=debug&editio...