1 files changed, 34 insertions, 0 deletions
diff --git a/tests/ui/consts/issue-69488.rs b/tests/ui/consts/issue-69488.rs
new file mode 100644
index 000000000..46546eada
--- /dev/null
+++ b/tests/ui/consts/issue-69488.rs
@@ -0,0 +1,34 @@
+// run-pass
+
+#![feature(const_ptr_write)]
+#![feature(const_mut_refs)]
+
+// Or, equivalently: `MaybeUninit`.
+pub union BagOfBits<T: Copy> {
+    uninit: (),
+    _storage: T,
+}
+
+pub const fn make_1u8_bag<T: Copy>() -> BagOfBits<T> {
+    assert!(core::mem::size_of::<T>() >= 1);
+    let mut bag = BagOfBits { uninit: () };
+    unsafe { (&mut bag as *mut _ as *mut u8).write(1); };
+    bag
+}
+
+pub fn check_bag<T: Copy>(bag: &BagOfBits<T>) {
+    let val = unsafe { (bag as *const _ as *const u8).read() };
+    assert_eq!(val, 1);
+}
+
+fn main() {
+    check_bag(&make_1u8_bag::<[usize; 1]>()); // Fine
+    check_bag(&make_1u8_bag::<usize>()); // Fine
+
+    const CONST_ARRAY_BAG: BagOfBits<[usize; 1]> = make_1u8_bag();
+    check_bag(&CONST_ARRAY_BAG); // Fine.
+    const CONST_USIZE_BAG: BagOfBits<usize> = make_1u8_bag();
+
+    // Used to panic since CTFE would make the entire `BagOfBits<usize>` uninit
+    check_bag(&CONST_USIZE_BAG);
+}