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Show impl for Weak #14759

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18 changes: 18 additions & 0 deletions src/liballoc/rc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -232,6 +232,15 @@ impl<T> Clone for Weak<T> {
}
}

impl<T: fmt::Show> fmt::Show for Weak<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.upgrade() {
Some(rc) => rc.fmt(f),
_ => "<stale weak pointer>".fmt(f)
}
}
}

#[doc(hidden)]
trait RcBoxPtr<T> {
fn inner<'a>(&'a self) -> &'a RcBox<T>;
Expand Down Expand Up @@ -399,4 +408,13 @@ mod tests {
assert!(cow1_weak.upgrade().is_none());
}

#[test]
fn test_stale_weak_pointer() {
let strong = Rc::new(75u);
let weak = strong.downgrade();
assert_eq!(format!("{}", weak), format!("75"));
drop(strong);
assert_eq!(format!("{}", weak), format!("<stale weak pointer>"));
}

}