Delegate as first param to an Extension Method

Ladies and Gents,

I recently tried this experiment:

static class TryParseExtensions
{
    public delegate bool TryParseMethod<T>(string s, out T maybeValue);
    public static T? OrNull<T>(this TryParseMethod<T> tryParser, string s) where T:struct 
    {
        T result;
        return tryParser(s, out result) ? (T?)result : null;
    }
}

// compiler error "'int.TryParse(string, out int)' is a 'method', which is not valid in the given context"
var result = int.TryParse.OrNull("1");  // int.TryParse.OrNull<int>("1"); doesnt work either

// compiler error: type cannot be infered....why?
var result2 = TryParseExtensions.OrNull(int.TryParse, "2"); 

// works as expected
var result3 = TryParseExtensions.OrNull<int>(int.TryParse, "3");
      var result4 = ((TryParseExtensions.TryParseMethod<int>)int.TryParse).OrNull("4");

I am wondering two things:

• Why can the compiler not infer the "int" type parameter?

• Do I understand correctly that extensions methods do not get discovered on Delegate types, as I guess they arent really of that type (but are a "Method") that only happen to match the delegates signature? As such a cast solves this. Would it be infeasable to enable scenario 1 to work (not this one specifically of course, but in general)? I guess from a language/compiler perspective and would it actually be useful, or am I just (attempting to) wildly abusing things here?

Looking forward to some insights. Thnx