message: explain a test
diff: fn main() {
  let x = 2usize as *const u32;
  + // this is not aligned, but we immediately cast it to a raw ptr so that must be okay
  let _y = unsafe { &*x as *const u32 };
  let x = 0usize as *const u32;
  + // this is NULL, but we immediately cast it to a raw ptr so that must be okay
  let _y = unsafe { &*x as *const u32 };
  }
  