C# compiler should report why a delegate conversion failed

[gafter]

I was recently implementing support for dotnet/csharplang#98 and discovered a regression in the quality of diagnostic for the following situation

delegate void D();
class Program
{
    static void Main()
    {
        D d = new D(Program.Method);
    }
    void Method() {}
}

We used to report

error CS0120: An object reference is required for the non-static field, method, or property 'Program.Method()'

It used to be that Program.Method was a perfectly good method group that converts to the delegate type D with an error. However, under the new proposed rules for dotnet/csharplang#98 it remains a perfectly good method group that no longer converts to the delegate type D, as no method in the group survives the new overload resolution rules. The compiler, under the new rules, reports

error CS0123: No overload for 'Method' matches delegate 'D'

The compiler has enough information internally to know why overload resolution failed here (it is because "An object reference is required for the non-static field, method, or property 'Program.Method()'"). However, the C# compiler currently never reports the underlying reason for a method group conversion failure.

I propose that some or all causes of a method group conversion failure should be reported. That would restore the quality of diagnostic for this particular case.