Using IEnumerable for Option is always 'Required'

[sunssd]

[Option('a', "aa", Required = false, Separator = ',')]
public IEnumerable A { get; set; }
[Option('b', "bb", Required = false)]
public string B { get; set; }
[Value(0, Required = true)]
public string C { get; set; }

For some reasons, if I only specify Option A and C, I will get the following error:

ERROR(S):
A required value not bound to option name is missing.
Error setting value to option 'a, aa': Check if Option or Value attribute values are set properly for the given type.

[moh-hassan]

This issue is similar to the bug #454.
Named Sequence option followed by a value option causes an error.

   myapp     vv -a xyz    //working: option value before named sequence option.
  myapp     -a xyz   vv // raise Exception:  named sequence option followed by a value option.

Have a look to this demo

[rmunn]

This will be fixed by #684 once it's merged in.