1// This file is part of ICU4X. For terms of use, please see the file
2// called LICENSE at the top level of the ICU4X source tree
3// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
4
5use crate::trait_hack::YokeTraitHack;
6use crate::Yoke;
7use crate::Yokeable;
8
9use core::ops::Deref;
10use stable_deref_trait::StableDeref;
11
12use crate::ZeroFrom;
13
14impl<'zf, C: ?Sized, T> ZeroFrom<'zf, C> for YokeTraitHack<T>
15where
16 T: ZeroFrom<'zf, C>,
17{
18 #[inline]
19 fn zero_from(cart: &'zf C) -> Self {
20 YokeTraitHack(T::zero_from(cart))
21 }
22}
23
24impl<Y, C> Yoke<Y, C>
25where
26 Y: for<'a> dynYokeable<'a>,
27 for<'a> YokeTraitHack<<Y as Yokeable<'a>>::Output>: ZeroFrom<'a, <C as Deref>::Target>,
28 C: StableDeref + Deref,
29 <C as Deref>::Target: 'static,
30{
31 /// Construct a [`Yoke`]`<Y, C>` from a cart implementing `StableDeref` by zero-copy cloning
32 /// the cart to `Y` and then yokeing that object to the cart.
33 ///
34 /// The type `Y` must implement [`ZeroFrom`]`<C::Target>`. This trait is auto-implemented
35 /// on many common types and can be custom implemented or derived in order to make it easier
36 /// to construct a `Yoke`.
37 ///
38 /// # Example
39 ///
40 /// Attach to a cart:
41 ///
42 /// ```
43 /// use std::borrow::Cow;
44 /// use yoke::Yoke;
45 ///
46 /// let yoke = Yoke::<Cow<'static, str>, String>::attach_to_zero_copy_cart(
47 /// "demo".to_owned(),
48 /// );
49 ///
50 /// assert_eq!("demo", yoke.get());
51 /// ```
52 pub fn attach_to_zero_copy_cart(cart: C) -> Self {
53 Yoke::<Y, C>::attach_to_cart(cart, |c| {
54 YokeTraitHack::<<Y as Yokeable>::Output>::zero_from(c).0
55 })
56 }
57}
58