recordsv3+builders+public.cs

public class Person
{
    public Person(int age, string name);

    public int Age { get; }
    public string Name { get; }

    public virtual Person With(in Builder builder);

    public ref struct Builder
    {
        public int Age { get; set; }
        public string Name { get; set; }
        public bool HasAge { get; }
        public bool HasName { get; }
    }
}

public class Student : Person
{
    public Student(int age, string name, double gpa);

    public double Gpa { get; }

    public override Person With(in Person.Builder builder);
    public virtual Student With(in Builder builder);

    public ref struct Builder
    {
        public Person.Builder Parent;

        public int Age { get; set; }
        public string Name { get; set; }
        public double Gpa { get; set; }
        public bool HasAge { get; }
        public bool HasName { get; }
        public bool HasGpa { get; }
    }
}