Adding upstream version 1.69.0+dfsg1.upstream/1.69.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 209 insertions, 179 deletions

diff --git a/vendor/yoke/src/erased.rs b/vendor/yoke/src/erased.rs
index c314d5186..bc4de9791 100644
--- a/vendor/yoke/src/erased.rs
+++ b/vendor/yoke/src/erased.rs
@@ -7,7 +7,7 @@
 //! See the docs of [`Yoke::erase_rc_cart()`](crate::Yoke::erase_rc_cart)
 //! and [`Yoke::erase_box_cart()`](crate::Yoke::erase_box_cart) for more info.
 //!
-//! Available with the `"alloc"` feature enabled.
+//! Available with the `"alloc"` Cargo feature enabled.
 
 use alloc::boxed::Box;
 use alloc::rc::Rc;
@@ -25,17 +25,17 @@ impl<T: 'static> ErasedDestructor for T {}
 ///
 /// See the docs of [`Yoke::erase_arc_cart()`](crate::Yoke::erase_rc_cart) for more info.
 ///
-/// Available with the `"alloc"` feature enabled.
+/// Available with the `"alloc"` Cargo feature enabled.
 pub type ErasedArcCart = Arc<dyn ErasedDestructor + Send + Sync>;
 /// A type-erased Cart that has `Rc` semantics
 ///
 /// See the docs of [`Yoke::erase_rc_cart()`](crate::Yoke::erase_rc_cart) for more info.
 ///
-/// Available with the `"alloc"` feature enabled.
+/// Available with the `"alloc"` Cargo feature enabled.
 pub type ErasedRcCart = Rc<dyn ErasedDestructor>;
 /// A type-erased Cart that has `Box` semantics
 ///
 /// See the docs of [`Yoke::erase_box_cart()`](crate::Yoke::erase_box_cart) for more info.
 ///
-/// Available with the `"alloc"` feature enabled.
+/// Available with the `"alloc"` Cargo feature enabled.
 pub type ErasedBoxCart = Box<dyn ErasedDestructor>;
diff --git a/vendor/yoke/src/is_covariant.rs b/vendor/yoke/src/is_covariant.rs
deleted file mode 100644
index 75d123c84..000000000
--- a/vendor/yoke/src/is_covariant.rs
+++ /dev/null
@@ -1,142 +0,0 @@
-// 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 ).
-
-#[cfg(feature = "alloc")]
-use alloc::{
-    borrow::{Cow, ToOwned},
-    boxed::Box,
-    rc::Rc,
-    string::String,
-};
-
-/// A type implementing `IsCovariant<'a>` is covariant with respect to lifetime `'a`.
-///
-/// Lifetime parameters that are safely cast in [`Yokeable`] are also valid for `IsCovariant`.
-///
-/// `IsCovariant` exists primarily to serve in trait bounds. The primary use case is to safely
-/// perform lifetime casting on trait objects (`dyn Trait`). This enables a type-erased [`Yoke`]
-/// consisting of only trait objects. See the examples.
-///
-/// `IsCovariant` is auto-implemented in [`#[derive(Yokeable)]`](macro@crate::Yokeable).
-///
-/// # Safety
-///
-/// This trait is safe to implement on types with a _covariant_ lifetime parameter. This will
-/// occur when the lifetime parameter is used within references, but not in the arguments of
-/// function pointers or in mutable positions (either in `&mut` or via interior mutability).
-///
-/// If a struct has multiple lifetime parameters, only the one used in `IsCovariant<'a>` needs to
-/// be covariant.
-///
-/// # Examples
-///
-/// Implementing on a simple struct with a single covariant lifetime:
-///
-/// ```
-/// # use yoke::*;
-/// struct MyStruct<'a>(&'a str);
-///
-/// // This is safe because 'a is covariant
-/// unsafe impl<'a> IsCovariant<'a> for MyStruct<'a> {}
-/// ```
-///
-/// By constraining the trait `ExampleTrait<'a>` on `IsCovariant<'a>`, we can safely implement
-/// [`Yokeable`] and [`ZeroFrom`] on its trait object:
-///
-/// ```
-/// # use yoke::*;
-/// # use zerofrom::*;
-/// # use core::mem;
-/// trait ExampleTrait<'a>: IsCovariant<'a> {
-///     fn get_message(&self) -> &'a str;
-/// }
-///
-/// // This wrapper is required because of the blanket Yokeable impl on &'static T
-/// pub struct ExampleTraitDynRef<'a>(pub &'a dyn ExampleTrait<'a>);
-///
-/// // The following impl is safe because the trait object requires IsCovariant.
-/// unsafe impl<'a> Yokeable<'a> for ExampleTraitDynRef<'static> {
-///     type Output = ExampleTraitDynRef<'a>;
-///     fn transform(&'a self) -> &'a Self::Output {
-///         unsafe { mem::transmute(self) }
-///     }
-///
-///     fn transform_owned(self) -> Self::Output {
-///         unsafe { mem::transmute(self) }
-///     }
-///
-///     unsafe fn make(from: Self::Output) -> Self {
-///         unsafe { mem::transmute(from) }
-///     }
-///
-///     fn transform_mut<F>(&'a mut self, f: F)
-///     where
-///         F: 'static + FnOnce(&'a mut Self::Output),
-///     {
-///         unsafe { f(mem::transmute::<&mut Self, &mut Self::Output>(self)) }
-///     }
-/// }
-///
-/// impl<'zf, 'a> ZeroFrom<'zf, dyn ExampleTrait<'a> + 'a> for ExampleTraitDynRef<'zf> {
-///     fn zero_from(this: &'zf (dyn ExampleTrait<'a> + 'a)) -> ExampleTraitDynRef<'zf> {
-///         // This is safe because the trait object requires IsCovariant.
-///         ExampleTraitDynRef(unsafe { core::mem::transmute(this) })
-///     }
-/// }
-///
-/// // Implement ExampleTrait on the struct from the previous example
-/// # struct MyStruct<'a>(&'a str);
-/// # unsafe impl<'a> IsCovariant<'a> for MyStruct<'a> {}
-/// impl<'a> ExampleTrait<'a> for MyStruct<'a> {
-///     fn get_message(&self) -> &'a str {
-///         self.0
-///     }
-/// }
-///
-/// // Example usage: a Yoke of a trait object
-/// let s = "Hello World".to_string();
-/// let yoke: Yoke<ExampleTraitDynRef<'static>, Box<dyn ExampleTrait>> =
-///     Yoke::attach_to_zero_copy_cart(Box::new(MyStruct(&s)));
-///
-/// assert_eq!(yoke.get().0.get_message(), "Hello World");
-/// ```
-///
-/// [`Yoke`]: crate::Yoke
-/// [`Yokeable`]: crate::Yokeable
-/// [`ZeroFrom`]: crate::ZeroFrom
-pub unsafe trait IsCovariant<'a>: 'a {}
-
-// IsCovariant is implemented on the standard library Copy types in macro_impls.rs
-
-// The following impls are safe because there is only one lifetime, 'a, and 'a is covariant
-
-unsafe impl<'a> IsCovariant<'a> for () {}
-
-unsafe impl<'a> IsCovariant<'a> for str {}
-#[cfg(feature = "alloc")]
-unsafe impl<'a> IsCovariant<'a> for String {}
-
-unsafe impl<'a, T: IsCovariant<'a>> IsCovariant<'a> for Option<T> {}
-
-unsafe impl<'a, T1: IsCovariant<'a>, T2: IsCovariant<'a>> IsCovariant<'a> for (T1, T2) {}
-
-unsafe impl<'a, T: IsCovariant<'a>> IsCovariant<'a> for [T] {}
-
-unsafe impl<'a, T: IsCovariant<'a>, const N: usize> IsCovariant<'a> for [T; N] {}
-
-#[cfg(feature = "alloc")]
-unsafe impl<'a, T: IsCovariant<'a> + ?Sized> IsCovariant<'a> for Box<T> {}
-
-#[cfg(feature = "alloc")]
-unsafe impl<'a, T: IsCovariant<'a> + ?Sized> IsCovariant<'a> for Rc<T> {}
-
-// This is safe because T has a covariant lifetime, and Cow's lifetime is also covariant
-#[cfg(feature = "alloc")]
-unsafe impl<'a, T: IsCovariant<'a> + ToOwned + ?Sized> IsCovariant<'a> for Cow<'a, T> where
-    <T as ToOwned>::Owned: Sized
-{
-}
-
-// This is safe because T has a covariant lifetime, and the reference lifetime is also covariant
-unsafe impl<'a, T: IsCovariant<'a> + ?Sized> IsCovariant<'a> for &'a T {}
diff --git a/vendor/yoke/src/lib.rs b/vendor/yoke/src/lib.rs
index 666e179e9..1524c067c 100644
--- a/vendor/yoke/src/lib.rs
+++ b/vendor/yoke/src/lib.rs
@@ -48,7 +48,6 @@ extern crate alloc;
 pub mod either;
 #[cfg(feature = "alloc")]
 pub mod erased;
-mod is_covariant;
 mod macro_impls;
 pub mod trait_hack;
 mod yoke;
@@ -59,7 +58,6 @@ mod zero_from;
 #[cfg(feature = "derive")]
 pub use yoke_derive::Yokeable;
 
-pub use crate::is_covariant::IsCovariant;
 pub use crate::yoke::{CloneableCart, Yoke};
 pub use crate::yokeable::Yokeable;
 
diff --git a/vendor/yoke/src/macro_impls.rs b/vendor/yoke/src/macro_impls.rs
index 664816818..060061b20 100644
--- a/vendor/yoke/src/macro_impls.rs
+++ b/vendor/yoke/src/macro_impls.rs
@@ -6,7 +6,7 @@
 // than using pointer casts
 #![allow(clippy::transmute_ptr_to_ptr)]
 
-use crate::{IsCovariant, Yokeable};
+use crate::Yokeable;
 use core::{mem, ptr};
 
 macro_rules! copy_yoke_impl {
@@ -38,7 +38,6 @@ macro_rules! impl_copy_type {
             type Output = Self;
             copy_yoke_impl!();
         }
-        unsafe impl<'a> IsCovariant<'a> for $ty {}
     };
 }
 
diff --git a/vendor/yoke/src/yoke.rs b/vendor/yoke/src/yoke.rs
index c3d8c37d9..7468b4d99 100644
--- a/vendor/yoke/src/yoke.rs
+++ b/vendor/yoke/src/yoke.rs
@@ -6,7 +6,6 @@ use crate::either::EitherCart;
 #[cfg(feature = "alloc")]
 use crate::erased::{ErasedArcCart, ErasedBoxCart, ErasedRcCart};
 use crate::trait_hack::YokeTraitHack;
-use crate::IsCovariant;
 use crate::Yokeable;
 use core::marker::PhantomData;
 use core::ops::Deref;
@@ -48,8 +47,7 @@ use alloc::sync::Arc;
 /// into another `Yoke` containing a different type that may contain elements of the original yoked
 /// value. See the [`Yoke::map_project()`] docs for more details.
 ///
-/// In general, `C` is a concrete type, but it is also possible for it to be a trait object;
-/// for more information, see [`IsCovariant`].
+/// In general, `C` is a concrete type, but it is also possible for it to be a trait object.
 ///
 /// # Example
 ///
@@ -83,7 +81,10 @@ pub struct Yoke<Y: for<'a> Yokeable<'a>, C> {
     cart: C,
 }
 
-impl<Y: for<'a> Yokeable<'a>, C: StableDeref> Yoke<Y, C> {
+impl<Y: for<'a> Yokeable<'a>, C: StableDeref> Yoke<Y, C>
+where
+    <C as Deref>::Target: 'static,
+{
     /// Construct a [`Yoke`] by yokeing an object to a cart in a closure.
     ///
     /// See also [`Yoke::try_attach_to_cart()`] to return a `Result` from the closure.
@@ -116,7 +117,14 @@ impl<Y: for<'a> Yokeable<'a>, C: StableDeref> Yoke<Y, C> {
     /// ```
     pub fn attach_to_cart<F>(cart: C, f: F) -> Self
     where
+        // safety note: This works by enforcing that the *only* place the return value of F
+        // can borrow from is the cart, since `F` must be valid for all lifetimes `'de`
+        //
+        // The <C as Deref>::Target: 'static on the impl is crucial for safety as well
+        //
+        // See safety docs at the bottom of this file for more information
         F: for<'de> FnOnce(&'de <C as Deref>::Target) -> <Y as Yokeable<'de>>::Output,
+        <C as Deref>::Target: 'static,
     {
         let deserialized = f(cart.deref());
         Self {
@@ -220,8 +228,10 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     /// ```
     /// use yoke::Yoke;
     ///
-    /// let local_data = "foo".to_string();
-    /// let yoke = Yoke::<&'static str, Box<String>>::attach_to_zero_copy_cart(Box::new(local_data));
+    /// let local_data = "foo".to_owned();
+    /// let yoke = Yoke::<&'static str, Box<String>>::attach_to_zero_copy_cart(
+    ///     Box::new(local_data),
+    /// );
     /// assert_eq!(*yoke.get(), "foo");
     ///
     /// // Get back the cart
@@ -235,9 +245,11 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     /// use std::borrow::Cow;
     /// use yoke::Yoke;
     ///
-    /// let local_data = "foo".to_string();
+    /// let local_data = "foo".to_owned();
     /// let mut yoke =
-    ///     Yoke::<Cow<'static, str>, Box<String>>::attach_to_zero_copy_cart(Box::new(local_data));
+    ///     Yoke::<Cow<'static, str>, Box<String>>::attach_to_zero_copy_cart(
+    ///         Box::new(local_data),
+    ///     );
     /// assert_eq!(yoke.get(), "foo");
     ///
     /// // Override data in the cart
@@ -265,6 +277,9 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     /// - `f()` must not panic
     /// - References from the yokeable `Y` should still be valid for the lifetime of the
     ///   returned cart type `C`.
+    /// - Lifetimes inside C must not be lengthened, even if they are themselves contravariant.
+    ///   I.e., if C contains an `fn(&'a u8)`, it cannot be replaced with `fn(&'static u8),
+    ///   even though that is typically safe.
     ///
     /// Typically, this means implementing `f` as something which _wraps_ the inner cart type `C`.
     /// `Yoke` only really cares about destructors for its carts so it's fine to erase other
@@ -506,12 +521,9 @@ where
     }
 }
 
-// This is safe because Y is 'static and C has a covariant lifetime
-unsafe impl<'b, Y: for<'a> Yokeable<'a>, C: IsCovariant<'b>> IsCovariant<'b> for Yoke<Y, C> {}
-
 #[test]
 fn test_clone() {
-    let local_data = "foo".to_string();
+    let local_data = "foo".to_owned();
     let y1 = Yoke::<alloc::borrow::Cow<'static, str>, Rc<String>>::attach_to_zero_copy_cart(
         Rc::new(local_data),
     );
@@ -575,7 +587,9 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     ///     string_2: &'a str,
     /// }
     ///
-    /// fn map_project_string_1(bar: Yoke<Bar<'static>, Rc<[u8]>>) -> Yoke<&'static str, Rc<[u8]>> {
+    /// fn map_project_string_1(
+    ///     bar: Yoke<Bar<'static>, Rc<[u8]>>,
+    /// ) -> Yoke<&'static str, Rc<[u8]>> {
     ///     bar.map_project(|bar, _| bar.string_1)
     /// }
     ///
@@ -651,7 +665,9 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     /// # use yoke::Yoke;
     /// # use std::str::{self, Utf8Error};
     /// #
-    /// fn slice(y: Yoke<&'static [u8], Rc<[u8]>>) -> Result<Yoke<&'static str, Rc<[u8]>>, Utf8Error> {
+    /// fn slice(
+    ///     y: Yoke<&'static [u8], Rc<[u8]>>,
+    /// ) -> Result<Yoke<&'static str, Rc<[u8]>>, Utf8Error> {
     ///     y.try_map_project(move |bytes, _| str::from_utf8(bytes))
     /// }
     /// ```
@@ -671,7 +687,9 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     ///     string_2: &'a str,
     /// }
     ///
-    /// fn map_project_string_1(bar: Yoke<Bar<'static>, Rc<[u8]>>) -> Result<Yoke<&'static str, Rc<[u8]>>, Utf8Error> {
+    /// fn map_project_string_1(
+    ///     bar: Yoke<Bar<'static>, Rc<[u8]>>,
+    /// ) -> Result<Yoke<&'static str, Rc<[u8]>>, Utf8Error> {
     ///     bar.try_map_project(|bar, _| str::from_utf8(bar.bytes_1))
     /// }
     ///
@@ -861,17 +879,19 @@ impl<Y: for<'a> Yokeable<'a>, C: 'static + Sized> Yoke<Y, Rc<C>> {
     /// let buffer1: Rc<String> = Rc::new("   foo bar baz  ".into());
     /// let buffer2: Box<String> = Box::new("  baz quux  ".into());
     ///
-    /// let yoke1 = Yoke::<&'static str, _>::attach_to_cart(buffer1, |rc| rc.trim());
+    /// let yoke1 =
+    ///     Yoke::<&'static str, _>::attach_to_cart(buffer1, |rc| rc.trim());
     /// let yoke2 = Yoke::<&'static str, _>::attach_to_cart(buffer2, |b| b.trim());
     ///
     /// let erased1: Yoke<_, ErasedRcCart> = yoke1.erase_rc_cart();
     /// // Wrap the Box in an Rc to make it compatible
-    /// let erased2: Yoke<_, ErasedRcCart> = yoke2.wrap_cart_in_rc().erase_rc_cart();
+    /// let erased2: Yoke<_, ErasedRcCart> =
+    ///     yoke2.wrap_cart_in_rc().erase_rc_cart();
     ///
     /// // Now erased1 and erased2 have the same type!
     /// ```
     ///
-    /// Available with the `"alloc"` feature enabled.
+    /// Available with the `"alloc"` Cargo feature enabled.
     pub fn erase_rc_cart(self) -> Yoke<Y, ErasedRcCart> {
         unsafe {
             // safe because the cart is preserved, just
@@ -905,17 +925,19 @@ impl<Y: for<'a> Yokeable<'a>, C: 'static + Sized + Send + Sync> Yoke<Y, Arc<C>>
     /// let buffer1: Arc<String> = Arc::new("   foo bar baz  ".into());
     /// let buffer2: Box<String> = Box::new("  baz quux  ".into());
     ///
-    /// let yoke1 = Yoke::<&'static str, _>::attach_to_cart(buffer1, |arc| arc.trim());
+    /// let yoke1 =
+    ///     Yoke::<&'static str, _>::attach_to_cart(buffer1, |arc| arc.trim());
     /// let yoke2 = Yoke::<&'static str, _>::attach_to_cart(buffer2, |b| b.trim());
     ///
     /// let erased1: Yoke<_, ErasedArcCart> = yoke1.erase_arc_cart();
     /// // Wrap the Box in an Rc to make it compatible
-    /// let erased2: Yoke<_, ErasedArcCart> = yoke2.wrap_cart_in_arc().erase_arc_cart();
+    /// let erased2: Yoke<_, ErasedArcCart> =
+    ///     yoke2.wrap_cart_in_arc().erase_arc_cart();
     ///
     /// // Now erased1 and erased2 have the same type!
     /// ```
     ///
-    /// Available with the `"alloc"` feature enabled.
+    /// Available with the `"alloc"` Cargo feature enabled.
     pub fn erase_arc_cart(self) -> Yoke<Y, ErasedArcCart> {
         unsafe {
             // safe because the cart is preserved, just
@@ -949,17 +971,19 @@ impl<Y: for<'a> Yokeable<'a>, C: 'static + Sized> Yoke<Y, Box<C>> {
     /// let buffer1: Rc<String> = Rc::new("   foo bar baz  ".into());
     /// let buffer2: Box<String> = Box::new("  baz quux  ".into());
     ///
-    /// let yoke1 = Yoke::<&'static str, _>::attach_to_cart(buffer1, |rc| rc.trim());
+    /// let yoke1 =
+    ///     Yoke::<&'static str, _>::attach_to_cart(buffer1, |rc| rc.trim());
     /// let yoke2 = Yoke::<&'static str, _>::attach_to_cart(buffer2, |b| b.trim());
     ///
     /// // Wrap the Rc in an Box to make it compatible
-    /// let erased1: Yoke<_, ErasedBoxCart> = yoke1.wrap_cart_in_box().erase_box_cart();
+    /// let erased1: Yoke<_, ErasedBoxCart> =
+    ///     yoke1.wrap_cart_in_box().erase_box_cart();
     /// let erased2: Yoke<_, ErasedBoxCart> = yoke2.erase_box_cart();
     ///
     /// // Now erased1 and erased2 have the same type!
     /// ```
     ///
-    /// Available with the `"alloc"` feature enabled.
+    /// Available with the `"alloc"` Cargo feature enabled.
     pub fn erase_box_cart(self) -> Yoke<Y, ErasedBoxCart> {
         unsafe {
             // safe because the cart is preserved, just
@@ -974,7 +998,7 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     /// Helper function allowing one to wrap the cart type `C` in a `Box<T>`.
     /// Can be paired with [`Yoke::erase_box_cart()`]
     ///
-    /// Available with the `"alloc"` feature enabled.
+    /// Available with the `"alloc"` Cargo feature enabled.
     #[inline]
     pub fn wrap_cart_in_box(self) -> Yoke<Y, Box<C>> {
         unsafe {
@@ -986,7 +1010,7 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     /// Can be paired with [`Yoke::erase_rc_cart()`], or generally used
     /// to make the [`Yoke`] cloneable.
     ///
-    /// Available with the `"alloc"` feature enabled.
+    /// Available with the `"alloc"` Cargo feature enabled.
     #[inline]
     pub fn wrap_cart_in_rc(self) -> Yoke<Y, Rc<C>> {
         unsafe {
@@ -998,7 +1022,7 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     /// Can be paired with [`Yoke::erase_arc_cart()`], or generally used
     /// to make the [`Yoke`] cloneable.
     ///
-    /// Available with the `"alloc"` feature enabled.
+    /// Available with the `"alloc"` Cargo feature enabled.
     #[inline]
     pub fn wrap_cart_in_arc(self) -> Yoke<Y, Arc<C>> {
         unsafe {
@@ -1037,7 +1061,7 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
     }
 }
 
-/// Safety docs for project()
+/// # Safety docs for project()
 ///
 /// (Docs are on a private const to allow the use of compile_fail doctests)
 ///
@@ -1140,3 +1164,151 @@ impl<Y: for<'a> Yokeable<'a>, C> Yoke<Y, C> {
 /// the output yokeable can _only_ have borrowed data flow in to it from the input. All paths of unsoundness require the
 /// unification of an existential and universal lifetime, which isn't possible.
 const _: () = ();
+
+/// # Safety docs for attach_to_cart()'s signature
+///
+/// The `attach_to_cart()` family of methods get by by using the following bound:
+///
+/// ```rust,ignore
+/// F: for<'de> FnOnce(&'de <C as Deref>::Target) -> <Y as Yokeable<'de>>::Output,
+/// C::Target: 'static
+/// ```
+///
+/// to enforce that the yoking closure produces a yokeable that is *only* allowed to borrow from the cart.
+/// A way to be sure of this is as follows: imagine if `F` *did* borrow data of lifetime `'a` and stuff it in
+/// its output. Then that lifetime `'a` would have to live at least as long as `'de` *for all `'de`*.
+/// The only lifetime that satisfies that is `'static` (since at least one of the potential `'de`s is `'static`),
+/// and we're fine with that.
+///
+/// ## Implied bounds and variance
+///
+/// The `C::Target: 'static` bound is tricky, however. Let's imagine a situation where we *didn't* have that bound.
+///
+/// One thing to remember is that we are okay with the cart itself borrowing from places,
+/// e.g. `&[u8]` is a valid cart, as is `Box<&[u8]>`. `C` is not `'static`.
+///
+/// (I'm going to use `CT` in prose to refer to `C::Target` here, since almost everything here has to do
+/// with C::Target and not C itself.)
+///
+/// Unfortunately, there's a sneaky additional bound inside `F`. The signature of `F` is *actually*
+///
+/// ```rust,ignore
+/// F: for<'de> where<C::Target: 'de> FnOnce(&'de C::Target) -> <Y as Yokeable<'de>>::Output
+/// ```
+///
+/// using made-up "where clause inside HRTB" syntax to represent a type that can be represented inside the compiler
+/// and type system but not in Rust code. The `CT: 'de` bond comes from the `&'de C::Target`: any time you
+/// write `&'a T`, an implied bound of `T: 'a` materializes and is stored alongside it, since references cannot refer
+/// to data that itself refers to data of shorter lifetimes. If a reference is valid, its referent must be valid for
+/// the duration of the reference's lifetime, so every reference *inside* its referent must also be valid, giving us `T: 'a`.
+/// This kind of constraint is often called a "well formedness" constraint: `&'a T` is not "well formed" without that
+/// bound, and rustc is being helpful by giving it to us for free.
+///
+/// Unfortunately, this messes with our universal quantification. The `for<'de>` is no longer "For all lifetimes `'de`",
+/// it is "for all lifetimes `'de` *where `CT: 'de`*". And if `CT` borrows from somewhere (with lifetime `'ct`), then we get a
+/// `'ct: 'de` bound, and `'de` candidates that live longer than `'ct` won't actually be considered.
+/// The neat little logic at the beginning stops working.
+///
+/// `attach_to_cart()` will instead enforce that the produced yokeable *either* borrows from the cart (fine), or from
+/// data that has a lifetime that is at least `'ct`. Which means that `attach_to_cart()` will allow us to borrow locals
+/// provided they live at least as long as `'ct`.
+///
+/// Is this a problem?
+///
+/// This is totally fine if CT's lifetime is covariant: if C is something like `Box<&'ct [u8]>`, even if our
+/// yoked object borrows from locals outliving `'ct`, our Yoke can't outlive that
+/// lifetime `'ct` anyway (since it's a part of the cart type), so we're fine.
+///
+/// However it's completely broken for contravariant carts (e.g. `Box<fn(&'ct u8)>`). In that case
+/// we still get `'ct: 'de`, and we still end up being able to
+/// borrow from locals that outlive `'ct`. However, our Yoke _can_ outlive
+/// that lifetime, because Yoke shares its variance over `'ct`
+/// with the cart type, and the cart type is contravariant over `'ct`.
+/// So the Yoke can be upcast to having a longer lifetime than `'ct`, and *that* Yoke
+/// can outlive `'ct`.
+///
+/// We fix this by forcing `C::Target: 'static` in `attach_to_cart()`, which would make it work
+/// for fewer types, but would also allow Yoke to continue to be covariant over cart lifetimes if necessary.
+///
+/// An alternate fix would be to not allowing yoke to ever be upcast over lifetimes contained in the cart
+/// by forcing them to be invariant. This is a bit more restrictive and affects *all* `Yoke` users, not just
+/// those using `attach_to_cart()`.
+///
+/// See https://github.com/unicode-org/icu4x/issues/2926
+/// See also https://github.com/rust-lang/rust/issues/106431 for potentially fixing this upstream by
+/// changing how the bound works.
+///
+/// # Tests
+///
+/// Here's a broken `attach_to_cart()` that attempts to borrow from a local:
+///
+/// ```rust,compile_fail
+/// use yoke::{Yoke, Yokeable};
+///
+/// let cart = vec![1, 2, 3, 4].into_boxed_slice();
+/// let local = vec![4, 5, 6, 7];
+/// let yoke: Yoke<&[u8], Box<[u8]>> = Yoke::attach_to_cart(cart, |_| &*local);
+/// ```
+///
+/// Fails as expected.
+///
+/// And here's a working one with a local borrowed cart that does not do any sneaky borrows whilst attaching.
+///
+/// ```rust
+/// use yoke::{Yoke, Yokeable};
+///
+/// let cart = vec![1, 2, 3, 4].into_boxed_slice();
+/// let local = vec![4, 5, 6, 7];
+/// let yoke: Yoke<&[u8], &[u8]> = Yoke::attach_to_cart(&cart, |c| &*c);
+/// ```
+///
+/// Here's an `attach_to_cart()` that attempts to borrow from a longer-lived local due to
+/// the cart being covariant. It fails, but would not if the alternate fix of forcing Yoke to be invariant
+/// were implemented. It is technically a safe operation:
+///
+/// ```rust,compile_fail
+/// use yoke::{Yoke, Yokeable};
+/// // longer lived
+/// let local = vec![4, 5, 6, 7];
+///
+/// let backing = vec![1, 2, 3, 4];
+/// let cart = Box::new(&*backing);
+///
+/// let yoke: Yoke<&[u8], Box<&[u8]>> = Yoke::attach_to_cart(cart, |_| &*local);
+/// println!("{:?}", yoke.get());
+/// ```
+///
+/// Finally, here's an `attach_to_cart()` that attempts to borrow from a longer lived local
+/// in the case of a contravariant lifetime. It does not compile, but in and of itself is not dangerous:
+///
+/// ```rust,compile_fail
+/// use yoke::Yoke;
+///
+/// type Contra<'a> = fn(&'a ());
+///
+/// let local = String::from("Hello World!");
+/// let yoke: Yoke<&'static str, Box<Contra<'_>>> = Yoke::attach_to_cart(Box::new((|_| {}) as _), |_| &local[..]);
+/// println!("{:?}", yoke.get());
+/// ```
+///
+/// It is dangerous if allowed to transform (testcase from #2926)
+///
+/// ```rust,compile_fail
+/// use yoke::Yoke;
+///
+/// type Contra<'a> = fn(&'a ());
+///
+///
+/// let local = String::from("Hello World!");
+/// let yoke: Yoke<&'static str, Box<Contra<'_>>> = Yoke::attach_to_cart(Box::new((|_| {}) as _), |_| &local[..]);
+/// println!("{:?}", yoke.get());
+/// let yoke_longer: Yoke<&'static str, Box<Contra<'static>>> = yoke;
+/// let leaked: &'static Yoke<&'static str, Box<Contra<'static>>> = Box::leak(Box::new(yoke_longer));
+/// let reference: &'static str = leaked.get();
+///
+/// println!("pre-drop: {reference}");
+/// drop(local);
+/// println!("post-drop: {reference}");
+///
+/// ```
+const _: () = ();
diff --git a/vendor/yoke/src/zero_from.rs b/vendor/yoke/src/zero_from.rs
index 679a28d59..d876d9c06 100644
--- a/vendor/yoke/src/zero_from.rs
+++ b/vendor/yoke/src/zero_from.rs
@@ -26,6 +26,7 @@ where
     Y: for<'a> Yokeable<'a>,
     for<'a> YokeTraitHack<<Y as Yokeable<'a>>::Output>: ZeroFrom<'a, <C as Deref>::Target>,
     C: StableDeref + Deref,
+    <C as Deref>::Target: 'static,
 {
     /// 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.
@@ -42,7 +43,9 @@ where
     /// use std::borrow::Cow;
     /// use yoke::Yoke;
     ///
-    /// let yoke = Yoke::<Cow<'static, str>, String>::attach_to_zero_copy_cart("demo".to_string());
+    /// let yoke = Yoke::<Cow<'static, str>, String>::attach_to_zero_copy_cart(
+    ///     "demo".to_owned(),
+    /// );
     ///
     /// assert_eq!("demo", yoke.get());
     /// ```