Clean up

[kdy1]

• Sort arguments of assert_eq call.
• Replace uses of self.input.xx() to xx!() (in lexer).
• Document should be consistent.
• Lexer should use Unicode ID instead of Unicode XID.

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.