error[E0506]: cannot assign to `self.input.cached_token` because it is borrowed
   --> /build/firefox-68.1.0/third_party/rust/cssparser/src/parser.rs:584:17
    |
559 |     pub fn next_including_whitespace_and_comments(&mut self) -> Result<&Token<'i>, BasicParseError<'i>> {
    |                                                   - let's call the lifetime of this reference `'1`
...
572 |             Some(ref cached_token)
    |                  ---------------- borrow of `self.input.cached_token` occurs here
...
584 |                 self.input.cached_token = Some(CachedToken {
    |                 ^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed `self.input.cached_token` occurs here
...
596 |         Ok(token)
    |         --------- returning this value requires that `self.input.cached_token.0` is borrowed for `'1`