37 lines
1.1 KiB
Rust
37 lines
1.1 KiB
Rust
// RFC 736 (and Issue 21407): functional struct update should respect privacy.
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// The `foo` module attempts to maintains an invariant that each `S`
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// has a unique `u64` id.
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// FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
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#![allow(static_mut_refs)]
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use self::foo::S;
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mod foo {
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use std::cell::{UnsafeCell};
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static mut COUNT : UnsafeCell<u64> = UnsafeCell::new(1);
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pub struct S { pub a: u8, pub b: String, secret_uid: u64 }
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pub fn make_secrets(a: u8, b: String) -> S {
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let val = unsafe { let p = COUNT.get(); let val = *p; *p = val + 1; val };
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println!("creating {}, uid {}", b, val);
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S { a: a, b: b, secret_uid: val }
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}
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impl Drop for S {
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fn drop(&mut self) {
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println!("dropping {}, uid {}", self.b, self.secret_uid);
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}
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}
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}
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fn main() {
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let s_1 = foo::make_secrets(3, format!("ess one"));
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let s_2 = foo::S { b: format!("ess two"), ..s_1 }; // FRU ...
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//~^ ERROR field `secret_uid` of struct `S` is private
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println!("main forged an S named: {}", s_2.b);
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// at end of scope, ... both s_1 *and* s_2 get dropped. Boom!
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}
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