using System;

public class Program

{

    public static void a(FormattableString str)

    {

        Console.WriteLine("Called formattable string - can deduce template/variables");

    }

​

    public static void b(string str)

    {

        Console.WriteLine("Called plain string instead");

    }

    public static void b(FormattableString str)

    {

        Console.WriteLine("Called formattable string - can deduce template/variables");

    }

    public static FormattableString ToFormattable(string str) 

    {

        return $"{str}";

    }

    public static void Main()

    {

        string name = "there";

        a($"hallo {name}");

        b($"hallo {name}");     

        // a("Will not compile with string literals");

        a($"Forcing interpolated string even when it's not needed would work, but it's againts our analysers");

        a(ToFormattable("Some Wrapper could work"));

    }

}