1

14:13.07 error[E0506]: cannot assign to self.input.cached_token because it is borrowed

14:13.07 --> /builddir/build/BUILD/thunderbird-68.1.1/third_party/rust/cssparser/src/parser.rs:584:17

14:13.07 |

14:13.07 559 | pub fn next_including_whitespace_and_comments(&mut self) -> Result<&Token<'i>, BasicParseError<'i>> {

14:13.07 | - let's call the lifetime of this reference '1

14:13.07 ...

14:13.07 572 | Some(ref cached_token)

14:13.07 | ---------------- borrow of self.input.cached_token occurs here

14:13.07 ...

14:13.07 584 | self.input.cached_token = Some(CachedToken {

14:13.07 | ^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed self.input.cached_token occurs here

14:13.07 ...

14:13.07 596 | Ok(token)

14:13.07 | --------- returning this value requires that self.input.cached_token.0 is borrowed for '1

14:13.80 error: aborting due to previous error

14:13.80 For more information about this error, try rustc --explain E0506.

14:13.83 error: Could not compile cssparser.

14:13.83 warning: build failed, waiting for other jobs to finish...

2

With Rust 1.37, that same code gave a compatibility warning:

warning[E0506]: cannot assign to `self.input.cached_token` because it is borrowed
   --> 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`
    |
    = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
    = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future
    = note: for more information, try `rustc --explain E0729`

It looks like this was fixed in cssparser here:
https://github.com/servo/rust-cssparser/pull/245

1 Like
3

Thanks

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