| // Copyright 2015 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| // RFC 736 (and Issue 21407): functional struct update should respect privacy. |
| |
| #![feature(const_fn)] |
| |
| // 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}; |
| |
| static mut count : UnsafeCell<u64> = UnsafeCell::new(1); |
| |
| pub struct S { pub a: u8, pub b: String, secret_uid: u64 } |
| |
| pub fn make_secrets(a: u8, b: String) -> S { |
| let val = unsafe { let p = count.get(); let val = *p; *p = val + 1; val }; |
| 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 ... |
| //~^ ERROR field `secret_uid` of struct `foo::S` is private |
| println!("main forged an S named: {}", s_2.b); |
| // at end of scope, ... both s_1 *and* s_2 get dropped. Boom! |
| } |