anchor.diff:      let isEqualsAssignment = 
           if uci.ContainsAttr<EqualsAssignmentAttribute> (true) then
               if types.Length <> 1 then
  -                failwith "Argu: Parameter '%s' has EqualsAssignment attribute but has arity <> 1." uci.Name
  +                failwithf "Argu: Parameter '%s' has EqualsAssignment attribute but has arity <> 1." uci.Name
               elif isRest then
  -                failwith "Argu: Parameter '%s' contains incompatible attributes 'EqualsAssignment' and 'Rest'." uci.Name
  +                failwithf "Argu: Parameter '%s' contains incompatible attributes 'EqualsAssignment' and 'Rest'." uci.Name
               true
           else
               false
  
positive.code:             | Some attr -> Some attr.Name
  
      if AppSettingsName.IsNone && commandLineArgs.IsEmpty then 
          failwith "Argu: parameter '%s' needs to have at least one parse source." uci.Name
  
      let printLabels = uci.ContainsAttr<PrintLabelsAttribute> (true)
  
  
negative.code:         | CliPrefix.DoubleDash -> "--" 
          | CliPrefix.Dash -> "-" 
          | CliPrefix.Empty -> "" 
          | p -> invalidArg "CliPrefix" <| sprintf "unsupported CLI prefix '%s'." (string p)
  
      prefixString + uci.Name.ToLower().Replace('_','-')
  
  