[Bug] Can't call an extension method for an Object

I have these extensions:
```VB.NET
Imports System.Runtime.CompilerServices

Module Extensions

Public Sub Print(ByVal aString As String)
Console.WriteLine(aString)
End Sub

Public Function IsSomething(ByVal o As String) As Boolean
Return o IsNot Nothing
End Function

Public Function IsSomething(ByVal o As Object) As Boolean
Return o IsNot Nothing
End Function
End Module
```

now, I have this code:
```VB.NET
Dim o As Object = ""
If o.IsSomething Then

End If
```

It gives me the runtime exception:
> Public member 'IsSomething' on type 'String' not found

Why can't vb use the extension Object.IsSomething or String.IsSomething?

Note that this code works:

```VB.NET
Dim o As String = ""
If o.IsSomething Then

End If
```

The only code that works with Object is this:
```VB.NET
Dim o As Object = Nothing
If o?.IsSomething Then

End If
```

I can accept that extension methods don't work with boxed values because of late binding, but why doesn't VB use the extension for the object and compile `O.IsSomething`: to `IsSomething(O)`?
I think this is a bug that needs to be fixed.