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Rollup merge of rust-lang#65144 - clarfon:moo, r=sfackler
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Add Cow::is_borrowed and Cow::is_owned

Implements rust-lang#65143.
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Centril authored Oct 23, 2019
2 parents f466f52 + eeb549b commit 360cdf4
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41 changes: 41 additions & 0 deletions src/liballoc/borrow.rs
Original file line number Diff line number Diff line change
Expand Up @@ -207,6 +207,47 @@ impl<B: ?Sized + ToOwned> Clone for Cow<'_, B> {
}

impl<B: ?Sized + ToOwned> Cow<'_, B> {
/// Returns true if the data is borrowed, i.e. if `to_mut` would require additional work.
///
/// # Examples
///
/// ```
/// #![feature(cow_is_borrowed)]
/// use std::borrow::Cow;
///
/// let cow = Cow::Borrowed("moo");
/// assert!(cow.is_borrowed());
///
/// let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
/// assert!(!bull.is_borrowed());
/// ```
#[unstable(feature = "cow_is_borrowed", issue = "65143")]
pub fn is_borrowed(&self) -> bool {
match *self {
Borrowed(_) => true,
Owned(_) => false,
}
}

/// Returns true if the data is owned, i.e. if `to_mut` would be a no-op.
///
/// # Examples
///
/// ```
/// #![feature(cow_is_borrowed)]
/// use std::borrow::Cow;
///
/// let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
/// assert!(cow.is_owned());
///
/// let bull = Cow::Borrowed("...moo?");
/// assert!(!bull.is_owned());
/// ```
#[unstable(feature = "cow_is_borrowed", issue = "65143")]
pub fn is_owned(&self) -> bool {
!self.is_borrowed()
}

/// Acquires a mutable reference to the owned form of the data.
///
/// Clones the data if it is not already owned.
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1 change: 1 addition & 0 deletions src/liballoc/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,7 @@
#![feature(const_generic_impls_guard)]
#![feature(const_generics)]
#![feature(const_in_array_repeat_expressions)]
#![feature(cow_is_borrowed)]
#![feature(dispatch_from_dyn)]
#![feature(core_intrinsics)]
#![feature(container_error_extra)]
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