src/vs/editor/common/services/unicodeTextModelHighlighter.ts/buildRegExpCharClassExpr
function buildRegExpCharClassExpr(codePoints: number[], flags?: string): string {
	const src = `[${strings.escapeRegExpCharacters(
		codePoints.map((i) => String.fromCodePoint(i)).join('')
	)}]`;
	return src;
}