Add regression test for #21562

Closes #21562.

Author: jooert

src/test/run-pass/issue-21562.rs

@@ -0,0 +1,27 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(core)]
+
+extern crate core;
+use core::marker::Sync;
+
+static SARRAY: [i32; 1] = [11];
+
+struct MyStruct {
+    pub arr: *const [i32],
+}
+unsafe impl Sync for MyStruct {}
+
+static mystruct: MyStruct = MyStruct {
+    arr: &SARRAY
+};
+
+fn main() {}