From e214e6db98badf837e95db89d7a9905294569cd6 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Wed, 20 Apr 2022 10:47:22 -0400
Subject: [PATCH] add mut_below_shr test

---
 tests/run-pass/stacked-borrows/stacked-borrows.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tests/run-pass/stacked-borrows/stacked-borrows.rs b/tests/run-pass/stacked-borrows/stacked-borrows.rs
index 8aea945f9093..b63f9addb0f6 100644
--- a/tests/run-pass/stacked-borrows/stacked-borrows.rs
+++ b/tests/run-pass/stacked-borrows/stacked-borrows.rs
@@ -16,6 +16,7 @@ fn main() {
     disjoint_mutable_subborrows();
     raw_ref_to_part();
     array_casts();
+    mut_below_shr();
 }
 
 // Make sure that reading from an `&mut` does, like reborrowing to `&`,
@@ -186,3 +187,12 @@ fn array_casts() {
     let p = &x as *const usize;
     assert_eq!(unsafe { *p.add(1) }, 1);
 }
+
+/// Transmuting &&i32 to &&mut i32 is fine.
+fn mut_below_shr() {
+    let x = 0;
+    let y = &x;
+    let p = unsafe { core::mem::transmute::<&&i32,&&mut i32>(&y) };
+    let r = &**p;
+    let _val = *r;
+}