Incorrect function resolution when calling overloads from python with keyword args #1097

Environment

• Pythonnet version: 2.4.0
• Python version: 3.6.5
• Operating System: Centos

Details

• Describe what you were trying to get done.

  When calling .NET functions with overloads from python with keyword args, the MethodBinder.Bind method will return the first method it finds which might not be the actual method the user is trying to call. Take the following simple C# code:

public static string OptionalArgumentsMethod(int arg1, int arg2)
{ 
    return $"{arg1}{arg2}XX";
}

public static string OptionalArgumentsMethod(int arg1, int arg2, int arg3 = 3)
{
    return $"{arg1}{arg2}{arg3}X";
}

public static string OptionalArgumentsMethod(int arg1, int arg2, int arg3 = 4, int arg4 = 5)
{
    return $"{arg1}{arg2}{arg3}{arg4}";
}

Calling, for example, OptionalArgumentsMethod(1, 2, arg3=5) we expect to get back 125X but instead we see:

>>> OptionalArgumentsMethod(1, 2)
'12XX'
>>> OptionalArgumentsMethod(1, 2, 3)
'123X'
>>> OptionalArgumentsMethod(1, 2, arg3=5)
'12XX'
>>> OptionalArgumentsMethod(1, 2, 3, 5)
'1235'
>>> OptionalArgumentsMethod(1, 2, 3, arg4=5)
'123X'
>>> OptionalArgumentsMethod(1, 2, arg4=0)
'12XX'