Invalid DataTypes for Default values may cause fatal error that can't be discovered or traced.

The following class have option with default value false :

public class Options
{
[Option('r', "read", MetaValue = "FILE", Required = false, HelpText = "Input file with data to process.")]
public string InputFile { get; set; }

[Option('w', "write", MetaValue = "FILE", HelpText = "Output FILE with processed data (otherwise standard output).")]
public string OutputFile { get; set; }

[Option('c', "calculate", HelpText = "calculate")]
public bool Calculate { get; set; }

//@@@@@ error here, Default = false for IEnumerable
//sure Default is wrong in that place, but discovered with code review after hours :)
[Option('g', "generators", Default = false, HelpText = "generator")]
public IEnumerable Generators { get; set; }



[Option('n', MetaValue = "INT", HelpText = "navigate.")]
public bool navigation { get; set; }
}

- No compilation error
- No error if commandline contain values for the option g like: `-r xyz.txt -c -g gen1`
- Exception for this commandline (the option g has no values) : `-r xyz.txt -c `

>Exception: Object of type 'System.Boolean' cannot be converted to type 'System.Collections.Generic.IEnumerable`1[System.String]'

The strange is that the exception can't help to determine where the source of error
It's discovered by accident when i don't pass values for the option g

[Complete TestCase](https://dotnetfiddle.net/h1e5S6)
Sure, i removed the Default from the option and the exception disappeared.

**Suggested Solution**

- Validate the match of the Datatype of the default values before setting it.
- Raise an exception ,e.g, "Parser Error: Invalid Default values for the option `"`.

Reproduce the failure using the linked Complete TestCase, especially the option with Default = false and no supplied values. Trace how default values are assigned to option properties; done should include datatype validation and an exception that identifies the affected option instead of an untraceable conversion error.

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