2015-01-26 13:27:22 +00:00
|
|
|
// RFC 736 (and Issue 21407): functional struct update should respect privacy.
|
|
|
|
|
|
|
|
// The `foo` module attempts to maintains an invariant that each `S`
|
|
|
|
// has a unique `u64` id.
|
|
|
|
use self::foo::S;
|
|
|
|
mod foo {
|
|
|
|
use std::cell::{UnsafeCell};
|
|
|
|
|
2019-01-29 15:47:30 +00:00
|
|
|
static mut COUNT : UnsafeCell<u64> = UnsafeCell::new(1);
|
2015-01-26 13:27:22 +00:00
|
|
|
|
|
|
|
pub struct S { pub a: u8, pub b: String, secret_uid: u64 }
|
|
|
|
|
|
|
|
pub fn make_secrets(a: u8, b: String) -> S {
|
2019-01-29 15:47:30 +00:00
|
|
|
let val = unsafe { let p = COUNT.get(); let val = *p; *p = val + 1; val };
|
2015-01-26 13:27:22 +00:00
|
|
|
println!("creating {}, uid {}", b, val);
|
|
|
|
S { a: a, b: b, secret_uid: val }
|
|
|
|
}
|
|
|
|
|
|
|
|
impl Drop for S {
|
|
|
|
fn drop(&mut self) {
|
|
|
|
println!("dropping {}, uid {}", self.b, self.secret_uid);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
fn main() {
|
|
|
|
let s_1 = foo::make_secrets(3, format!("ess one"));
|
|
|
|
let s_2 = foo::S { b: format!("ess two"), ..s_1 }; // FRU ...
|
2020-09-02 07:40:56 +00:00
|
|
|
//~^ ERROR field `secret_uid` of struct `S` is private
|
2015-01-26 13:27:22 +00:00
|
|
|
println!("main forged an S named: {}", s_2.b);
|
|
|
|
// at end of scope, ... both s_1 *and* s_2 get dropped. Boom!
|
|
|
|
}
|