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add from_send to Rc, since #9509 is fixed #10322

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Nov 7, 2013
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45 changes: 24 additions & 21 deletions src/libstd/rc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -48,12 +48,21 @@ impl<T: Freeze> Rc<T> {
}
}

impl<T: Send> Rc<T> {
/// Construct a new reference-counted box from a `Send` value
#[inline]
pub fn from_send(value: T) -> Rc<T> {
unsafe {
Rc::new_unchecked(value)
}
}
}

impl<T> Rc<T> {
/// Unsafety construct a new reference-counted box from any value.
///
/// If the type is not `Freeze`, the `Rc` box will incorrectly still be considered as a `Freeze`
/// type. It is also possible to create cycles, which will leak, and may interact poorly with
/// managed pointers.
/// It is possible to create cycles, which will leak, and may interact
/// poorly with managed pointers.
#[inline]
pub unsafe fn new_unchecked(value: T) -> Rc<T> {
Rc{ptr: transmute(~RcBox{value: value, count: 1})}
Expand Down Expand Up @@ -104,26 +113,22 @@ mod test_rc {

#[test]
fn test_clone() {
unsafe {
let x = Rc::new_unchecked(Cell::new(5));
let y = x.clone();
do x.borrow().with_mut_ref |inner| {
*inner = 20;
}
assert_eq!(y.borrow().take(), 20);
let x = Rc::from_send(Cell::new(5));
let y = x.clone();
do x.borrow().with_mut_ref |inner| {
*inner = 20;
}
assert_eq!(y.borrow().take(), 20);
}

#[test]
fn test_deep_clone() {
unsafe {
let x = Rc::new_unchecked(Cell::new(5));
let y = x.deep_clone();
do x.borrow().with_mut_ref |inner| {
*inner = 20;
}
assert_eq!(y.borrow().take(), 5);
let x = Rc::from_send(Cell::new(5));
let y = x.deep_clone();
do x.borrow().with_mut_ref |inner| {
*inner = 20;
}
assert_eq!(y.borrow().take(), 5);
}

#[test]
Expand All @@ -142,10 +147,8 @@ mod test_rc {

#[test]
fn test_destructor() {
unsafe {
let x = Rc::new_unchecked(~5);
assert_eq!(**x.borrow(), 5);
}
let x = Rc::from_send(~5);
assert_eq!(**x.borrow(), 5);
}
}

Expand Down
19 changes: 19 additions & 0 deletions src/test/compile-fail/no_freeze-rc.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
// Copyright 2013 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.

use std::rc::Rc;
use std::cell::Cell;

fn bar<T: Freeze>(_: T) {}

fn main() {
let x = Rc::from_send(Cell::new(5));
bar(x); //~ ERROR instantiating a type parameter with an incompatible type `std::rc::Rc<std::cell::Cell<int>>`, which does not fulfill `Freeze`
}