CS0704 with generics - update to auto interpret?

[UniqeId6542]

I cannot use an extension method on an open generic, but I can use that same method if I call it from the declaring class type.

public class NumbersTest<TValue>
    where TValue : INumberBase<TValue>
{
    public static void Test()
    {
        TValue a1 = TValue.Two_A(); // CS0704 - Could this be auto-interpreted?
        TValue a2 = Numbers.Two_A<TValue>(); // no error
        TValue b1 = TValue.Two_B; // CS0704 - Could this be auto-interpreted?
        TValue b2 = Numbers.get_Two_B<TValue>(); // no error

        int three = int.Three; // CS9339 - expected ambiguity between Numbers and MoreNumbers.
        TValue threeA = TValue.Three; // CS0704 - Could this be auto-interpreted & turned into CS9339?
    }
}

public static class Numbers
{
    public static TValue Two_A<TValue>()
        where TValue : INumberBase<TValue>
    {
        return TValue.One + TValue.One;
    }

    extension<TValue>(TValue)
        where TValue : INumberBase<TValue>
    {
        public static TValue Two_B => TValue.One + TValue.One;
        public static TValue Three => TValue.One + TValue.One + TValue.One;
    }
}

public static class MoreNumbers
{
    extension<TValue>(TValue)
        where TValue : INumberBase<TValue>
    {
        public static TValue Three => TValue.One + TValue.One + TValue.One;
    }
}

Is anything preventing the compiler from auto-interpreting an extension method call into the normal static call?
What extra knowledge would be needed to do this 'conversion' behind the scenes?

Could Roslyn be updated to support the open-generic use case for this type of extension method?

[CyrusNajmabadi]

To make Roslyn behave differently, you'd need the language to change here. That starts with a discussion you would need to open first at dotnet/csharplang.

Be clear in what you're asking for.

[UniqeId6542]

I thought about submitting this to csharplang, but it didn't seem like a language change to me. Static calls on open generic types already exist. Extension calls on types exist. Extensions for generics exist. Is there some rule that says calling methods on open generics using the extension format is illegal?
That's why I thought the compiler should be updated to support something that probably already could be legal C#.
I can duplicate the question over to csharplang if that's needed though.

[CyrusNajmabadi]

Is there some rule that says calling methods on open generics using the extension format is illegal?

you'd have to reverse it. if it's not legal, then it's illegal.

That said, what you'd need to do here is not just presume it is not illegal. If you think this is a compiler bug, then it requires going to all the spec language as to how these features work and tracing through a path that indicates that it shoudl be allowed, and thus the compiler is out of spec.

[ZzZombo]

I don't even understand how this is supposed to work? You can't call extension methods on open generic because there is no valid receiver at all to call it upon. You can't even replace it with the static method call syntax for these reasons, what would the this parameter look like?

[UniqeId6542]

what would the this parameter look like?

It's a static method, there is no 'this'.

You can't even replace it with the static method call syntax

I don't understand. The static call syntax already works. Numbers.Two_A<TValue>() compiles and produces a valid result. (And new C# allows for extension methods on types, not just objects.)