TestRegexSourceGenerator.cs

    public static partial class TestRegexSourceGenerator
    {
        // The Source Generator generates the code of the method at compile time
        [RegexGenerator(@"\d+", RegexOptions.Compiled, 50)]
        private static partial Regex IsDigitRegex();

        public static bool IsDigit(string value)
        {
            return IsDigitRegex().IsMatch(value);
        }
    }