TUX004 - Missing failure message for refinement

The Refinement attribute must have a FailureMessage property set to a non-empty string or the method it's applied to must return a string? which when non-empty is used as the failure message.

The FailureMessage property can be set either via the constructor or via the property setter.

using Tuxedo;

public class Test
{
    // the following are invalid
    [Refinement]
    public static bool IsPositive(int value) => value > 0;
    
    // missing the nullable attribute on string
    [Refinement]
    public static string IsPositive(int value) => 
        value > 0 ? null : "Value must be positive"; 
    
    // the following are valid
    [Refinement("Value must be positive")]
    public static bool IsPositive(int value) => value > 0;
    
    [Refinement(FailureMessage = "Value must be positive")]
    public static bool IsPositive(int value) => value > 0;
    
    [Refinement]
    public static string? IsPositive(int value) => 
        value > 0 ? null : "Value must be positive";
}