Lines beginning with //! result in an error

[Yarn]

Describe the bug
lines beginning with //! result in

  |
6 | #[derive(pest_derive::Parser)]
  |          ^^^^^^^^^^^^^^^^^^^
  |
  = help: message: error parsing
            --> 16:1
             |
          16 | //!
             | ^---
             |
             = expected EOI or rule

To Reproduce
load a .pest file with a line starting with //!

Expected behavior
The line is ignored

Additional context
I'm using pest 2.5.7
The issue was not present in pest 2.1.3

this looks potentially similar to #818.

[tomtau]

CC @huacnlee

[huacnlee]

@tomtau Get it.

[huacnlee]

That now is a grammar_doc issue, it by design.

Because Pest required at latest have one grammar_rule:

grammar_rules = _{ SOI ~ grammar_doc* ~ (grammar_rule)+ ~ EOI }

@tomtau Should I change grammar_rule+ into grammar_rule*, to let allow zero rules in a pest file.

[Yarn]

I did have grammar rules, they were all before the comment in case that matters.