src/test/ui/functional-struct-update/functional-struct-update-respects-privacy.rs

   1 // RFC 736 (and Issue 21407): functional struct update should respect privacy.
   2
   3 // The `foo` module attempts to maintains an invariant that each `S`
   4 // has a unique `u64` id.
   5 use self::foo::S;
   6 mod foo {
   7     use std::cell::{UnsafeCell};
   8
   9     static mut COUNT : UnsafeCell<u64> = UnsafeCell::new(1);
  10
  11     pub struct S { pub a: u8, pub b: String, secret_uid: u64 }
  12
  13     pub fn make_secrets(a: u8, b: String) -> S {
  14         let val = unsafe { let p = COUNT.get(); let val = *p; *p = val + 1; val };
  15         println!("creating {}, uid {}", b, val);
  16         S { a: a, b: b, secret_uid: val }
  17     }
  18
  19     impl Drop for S {
  20         fn drop(&mut self) {
  21             println!("dropping {}, uid {}", self.b, self.secret_uid);
  22         }
  23     }
  24 }
  25
  26 fn main() {
  27     let s_1 = foo::make_secrets(3, format!("ess one"));
  28     let s_2 = foo::S { b: format!("ess two"), ..s_1 }; // FRU ...
  29     //~^ ERROR field `secret_uid` of struct `S` is private
  30     println!("main forged an S named: {}", s_2.b);
  31     // at end of scope, ... both s_1 *and* s_2 get dropped.  Boom!
  32 }