1 files changed, 54 insertions, 0 deletions
diff --git a/vendor/yoke/src/zero_from.rs b/vendor/yoke/src/zero_from.rs
new file mode 100644
index 000000000..679a28d59
--- /dev/null
+++ b/vendor/yoke/src/zero_from.rs
@@ -0,0 +1,54 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+use crate::trait_hack::YokeTraitHack;
+use crate::Yoke;
+use crate::Yokeable;
+
+use core::ops::Deref;
+use stable_deref_trait::StableDeref;
+
+use crate::ZeroFrom;
+
+impl<'zf, C: ?Sized, T> ZeroFrom<'zf, C> for YokeTraitHack<T>
+where
+    T: ZeroFrom<'zf, C>,
+{
+    #[inline]
+    fn zero_from(cart: &'zf C) -> Self {
+        YokeTraitHack(T::zero_from(cart))
+    }
+}
+
+impl<Y, C> Yoke<Y, C>
+where
+    Y: for<'a> Yokeable<'a>,
+    for<'a> YokeTraitHack<<Y as Yokeable<'a>>::Output>: ZeroFrom<'a, <C as Deref>::Target>,
+    C: StableDeref + Deref,
+{
+    /// Construct a [`Yoke`]`<Y, C>` from a cart implementing `StableDeref` by zero-copy cloning
+    /// the cart to `Y` and then yokeing that object to the cart.
+    ///
+    /// The type `Y` must implement [`ZeroFrom`]`<C::Target>`. This trait is auto-implemented
+    /// on many common types and can be custom implemented or derived in order to make it easier
+    /// to construct a `Yoke`.
+    ///
+    /// # Example
+    ///
+    /// Attach to a cart:
+    ///
+    /// ```
+    /// use std::borrow::Cow;
+    /// use yoke::Yoke;
+    ///
+    /// let yoke = Yoke::<Cow<'static, str>, String>::attach_to_zero_copy_cart("demo".to_string());
+    ///
+    /// assert_eq!("demo", yoke.get());
+    /// ```
+    pub fn attach_to_zero_copy_cart(cart: C) -> Self {
+        Yoke::<Y, C>::attach_to_cart(cart, |c| {
+            YokeTraitHack::<<Y as Yokeable>::Output>::zero_from(c).0
+        })
+    }
+}