Add a test for misaligned pointer derefs inside addr_of!

Author: saethlin

tests/ui/mir/addrof_alignment.rs

@@ -0,0 +1,15 @@
+// run-pass
+// ignore-wasm32-bare: No panic messages
+// compile-flags: -C debug-assertions
+
+struct Misalignment {
+    a: u32,
+}
+
+fn main() {
+    let items: [Misalignment; 2] = [Misalignment { a: 0 }, Misalignment { a: 1 }];
+    unsafe {
+        let ptr: *const Misalignment = items.as_ptr().cast::<u8>().add(1).cast::<Misalignment>();
+        let _ptr = core::ptr::addr_of!((*ptr).a);
+    }
+}