Out var scope vs extension methods

1. Case: user-defined literals requested. Answer: use extension methods #4971.
2. Case: inconsistent scoping suggested for if-else #12597, #12939. Answer: why not extension methods?

public void Before(string arg)
{
    if (!int.TryParse(arg, out int number))
        throw new ArgumentException();

    Console.WriteLine($"It's a number: {number}");
}

public void After(string arg)
{
    Guard.IsNumber(arg, out int number);

    Console.WriteLine($"It's a number: {number}");
}

public static class Guard
{
    public static void IsNumber(string arg, out int parsed)
    {
        if (!int.TryParse(arg, out int secondParsed))
            throw new ArgumentException();

        parsed = secondParsed;//Otherwise: "error CS0136: A local or parameter named 'parsed' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter."
    }
}

[svick]

BTW, you can simplify Guard.IsNumber to:

public static void IsNumber(string arg, out int parsed)
{
    if (!int.TryParse(arg, out parsed)) // not "out int parsed"
        throw new ArgumentException();
}

[CyrusNajmabadi]

Closing this out. We’re doing all language design now at dotnet/csharplang. If you’re still interested in this idea let us know and we can migrate this over to a discussion in that repo. Thanks!