Extension Methods on Static Interfaces

[TonyValenti]

I'd like to request the ability to create extension methods for static intefaces. For example:

    public static class StaticExtensions {
        public static bool ParseCustom<T>(static this T, string Input) where T : IParsable<T> {
            //
        }
    }

[svick]

Even though the motivation is a bit different, this is a duplicate of #2505 and more generally part of #192.

[TahirAhmadov]

Isn't it superseded by #5497 ?