1 files changed, 41 insertions, 0 deletions
diff --git a/third_party/rust/yoke/src/erased.rs b/third_party/rust/yoke/src/erased.rs
new file mode 100644
index 0000000000..4395404a66
--- /dev/null
+++ b/third_party/rust/yoke/src/erased.rs
@@ -0,0 +1,41 @@
+// 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 ).
+
+//! This module contains helper types for erasing Cart types.
+//!
+//! 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.
+//!
+//! ✨ *Enabled with the `alloc` Cargo feature.*
+
+use alloc::boxed::Box;
+use alloc::rc::Rc;
+use alloc::sync::Arc;
+
+/// Dummy trait that lets us `dyn Drop`
+///
+/// `dyn Drop` isn't legal (and doesn't make sense since `Drop` is not
+/// implement on all destructible types). However, all trait objects come with
+/// a destructor, so we can just use an empty trait to get a destructor object.
+pub trait ErasedDestructor: 'static {}
+impl<T: 'static> ErasedDestructor for T {}
+
+/// A type-erased Cart that has `Arc` semantics
+///
+/// See the docs of [`Yoke::erase_arc_cart()`](crate::Yoke::erase_rc_cart) for more info.
+///
+/// ✨ *Enabled with the `alloc` Cargo feature.*
+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.
+///
+/// ✨ *Enabled with the `alloc` Cargo feature.*
+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.
+///
+/// ✨ *Enabled with the `alloc` Cargo feature.*
+pub type ErasedBoxCart = Box<dyn ErasedDestructor>;