Y U GIVE ME AN ABSOLUTE PATH :(

failed_attempt.cs

[System.AttributeUsage(System.AttributeTargets.Class)]
public class ScriptClass : System.Attribute
{
	public string filePath;

	public ScriptClass ([System.Runtime.CompilerServices.CallerFilePath] string path = "")
	{
		filePath = path;
	}
}

[ScriptClass]
class MainClass
{
	public static void Main (string[] args)
	{
		new MainClass();
	}

	public MainClass()
	{
		ScriptClass MyAttribute = (ScriptClass)Attribute.GetCustomAttribute(this.GetType(), typeof(ScriptClass));

		if (MyAttribute == null)
		{
			Console.WriteLine("The attribute was not found.");
		}
		else
		{
			Console.WriteLine("The Class Path is: {0}." , MyAttribute.filePath);
		}
	}
}