From aa38b7fcacbc5443a3bc6b205cd9ef50feabc932 Mon Sep 17 00:00:00 2001
From: Folkert de Vries <folkert@folkertdev.nl>
Date: Wed, 8 Oct 2025 15:29:24 +0200
Subject: [PATCH] add `MaybeUninit` to `minicore`

---
 tests/auxiliary/minicore.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/auxiliary/minicore.rs b/tests/auxiliary/minicore.rs
index 24da2c4a1c4e..4830253e89d4 100644
--- a/tests/auxiliary/minicore.rs
+++ b/tests/auxiliary/minicore.rs
@@ -27,6 +27,7 @@
     decl_macro,
     f16,
     f128,
+    transparent_unions,
     asm_experimental_arch,
     unboxed_closures
 )]
@@ -127,6 +128,25 @@ pub struct ManuallyDrop<T: PointeeSized> {
 }
 impl<T: Copy + PointeeSized> Copy for ManuallyDrop<T> {}
 
+#[lang = "maybe_uninit"]
+#[repr(transparent)]
+pub union MaybeUninit<T> {
+    uninit: (),
+    value: ManuallyDrop<T>,
+}
+
+impl<T: Copy + PointeeSized> Copy for MaybeUninit<T> {}
+
+impl<T> MaybeUninit<T> {
+    pub const fn uninit() -> Self {
+        Self { uninit: () }
+    }
+
+    pub const fn new(value: T) -> Self {
+        Self { value: ManuallyDrop { value } }
+    }
+}
+
 #[repr(transparent)]
 #[rustc_nonnull_optimization_guaranteed]
 pub struct NonNull<T: ?Sized> {