error[E0537]: invalid predicate `unknown`
  --> src/test/compile-fail/E0537.rs:11:7
   |
11 | #[cfg(unknown())] //~ ERROR E0537
   |       ^^^^^^^^^^
Currently, we underline a little too much of the predicate.  Notice that we underline two ) instead of just the matching )
I noticed that E0535 and E0536 also have the same problem