Don't emit prefer-w when both `i` and `u` flags are set

[tats-u]

Information:

• ESLint version: 9.21.0
• eslint-plugin-regexp version: 2.7.0

See https://github.com/fabian-hiller/valibot/blob/main/library/package.json and https://github.com/fabian-hiller/valibot/blob/main/pnpm-lock.yaml

Description

When both i and u flags are set, \w matches U+017F & U+212A, too. This plugin must not emit prefer-w on just [0-9a-z_] under that condition.

eslint/eslint#19474 (comment)

const ex1 = /^[0-9A-Z_]+$/iu;
const ex2 = /^\w+$/iu;

const str = "\u017f\u212a";

// ESLint expected: true / actual: false
console.log(ex1.test(str) === ex2.test(str));

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_class_escape#w

If the regex is Unicode-aware and the i flag is set, it also matches other Unicode characters that get canonicalized to one of the characters above through case folding.

↑This makes U+017F and U+212A matches \w in iu flag.