Bug: filterset binary operators are parsed as function applications

Description of the issue

Description: When running the Jujutsu test suite, I'm seeing a flaky test I would like to skip. I tried using the following command after skimming the filterset documentation:

austin@GANON:~/src/jj$ cargo nextest run --workspace -j 6 -E 'not(test(test_shallow_commits_lack_parents))'

However, this fails with a rather confusing error, because the not operator is (I am assuming completely based on no reading of the code) parsed as a function not() which doesn't exist.

Simply adding a space not (...) in the predicate does what I expect and succeeds.

Expected outcome

I expect the test suite to run, and skip the singular test named test_shallow_commits_lack_parents

Actual result

  error: expected expression
   ╭────
 1 │ not(test(test_shallow_commits_lack_parents))
   · ──────────────────────┬─────────────────────
   ·                       ╰── missing expression
   ╰────

  error: expected end of expression
   ╭────
 1 │ not(test(test_shallow_commits_lack_parents))
   · ──────────────────────┬─────────────────────
   ·                       ╰── unparsed input
   ╰────

error: failed to parse filterset

Nextest version

austin@GANON:~/src/jj$ cargo nextest --version
cargo-nextest 0.9.79
release: 0.9.79
host: x86_64-unknown-linux-gnu

Additional context

I assume this is some kind of grammar nit, though I'm no expert in parsing, but ideally there should be:

Some fix to the grammar to allow this (i.e. parsing binary operators as a separate term). Maybe you could hack it by also defining every binary operator as a 1-arity function :)
At least some documentation on this, if nothing else.
A better error message? I puzzled on this for a solid 5 minutes. Not sure what can be done here.

Also, I note that nextest 0.9.80 added (back) support for --skip, presumably in terms of a filterset-under-the-hood. That would have let me work around this, but this still remains.

nextest-rs / nextest