message: embrace find_map and some whitespace changes
diff: @@ -263,14 +263,13 @@ impl<'tcx> Stack {
  .rev() // search top-to-bottom
  // Return permission of first item that grants access.
  // We require a permission with the right tag, ensuring U3 and F3.
  - .filter_map(|(idx, item)|
  + .find_map(|(idx, item)|
  if item.perm.grants(access) && tag == item.tag {
  Some((idx, item.perm))
  } else {
  None
  }
  )
  - .next()
  }
  /// Test if a memory `access` using pointer tagged `tag` is granted.
  