From: Joshua Simmons <josh@nega.tv>
Date: Sat, 19 Nov 2022 23:20:39 +0000 (+0100)
Subject: Add `Upcast` trait for casting to super-trait
X-Git-Url: https://git.nega.tv//gitweb.cgi?a=commitdiff_plain;h=a0ed99e2f0a37fb04f0a1c728e0bc81ba1e7f482;p=josh%2Fnarcissus

Add `Upcast` trait for casting to super-trait
---

diff --git a/narcissus-core/src/lib.rs b/narcissus-core/src/lib.rs
index 2c09509..cb63fdd 100644
--- a/narcissus-core/src/lib.rs
+++ b/narcissus-core/src/lib.rs
@@ -264,6 +264,10 @@ pub fn zeroed_box<T>() -> Box<MaybeUninit<T>> {
 /// Negative traits aren't stable yet, so use a dummy PhantomData marker to implement !Send
 pub type PhantomUnsend = std::marker::PhantomData<*mut ()>;
 
+pub trait Upcast<T: ?Sized> {
+    fn upcast(&self) -> &T;
+}
+
 #[must_use]
 pub fn align_offset(x: usize, align: usize) -> usize {
     debug_assert!(align.is_power_of_two());