From d2290c425314a391d4b8eef846d0d0633d6b296d Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 28 Dec 2025 16:24:55 +0100
Subject: [PATCH] fix ManuallyDrop::into_inner aliasing (Miri) issues

---
 library/core/src/mem/manually_drop.rs               | 4 +++-
 src/tools/miri/tests/pass/issues/issue-miri-4793.rs | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 src/tools/miri/tests/pass/issues/issue-miri-4793.rs

diff --git a/library/core/src/mem/manually_drop.rs b/library/core/src/mem/manually_drop.rs
index 74f917bcf1cc..ca008a82ee6f 100644
--- a/library/core/src/mem/manually_drop.rs
+++ b/library/core/src/mem/manually_drop.rs
@@ -200,7 +200,9 @@ pub const fn new(value: T) -> ManuallyDrop<T> {
     #[rustc_const_stable(feature = "const_manually_drop", since = "1.32.0")]
     #[inline(always)]
     pub const fn into_inner(slot: ManuallyDrop<T>) -> T {
-        slot.value.into_inner()
+        // Cannot use `MaybeDangling::into_inner` as that does not yet have the desired semantics.
+        // SAFETY: We know this is a valid `T`. `slot` will not be dropped.
+        unsafe { (&raw const slot).cast::<T>().read() }
     }
 
     /// Takes the value from the `ManuallyDrop<T>` container out.
diff --git a/src/tools/miri/tests/pass/issues/issue-miri-4793.rs b/src/tools/miri/tests/pass/issues/issue-miri-4793.rs
new file mode 100644
index 000000000000..ccbff462f995
--- /dev/null
+++ b/src/tools/miri/tests/pass/issues/issue-miri-4793.rs
@@ -0,0 +1,3 @@
+fn main() {
+    let _ = std::panic::catch_unwind(|| Box::<str>::from("..."));
+}