anchor.diff:          | CliPrefix.DoubleDash -> "--" 
           | CliPrefix.Dash -> "-" 
           | CliPrefix.Empty -> "" 
  -        | p -> invalidArg "CliPrefix" "unsupported CLI prefix '%A'." p
  +        | p -> invalidArg "CliPrefix" <| sprintf "unsupported CLI prefix '%s'." (string p)
   
       prefixString + uci.Name.ToLower().Replace('_','-')
   
  
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:     let isEqualsAssignment = 
          if uci.ContainsAttr<EqualsAssignmentAttribute> (true) then
              if types.Length <> 1 then
                  failwithf "Argu: Parameter '%s' has EqualsAssignment attribute but has arity <> 1." uci.Name
              elif isRest then
                  failwithf "Argu: Parameter '%s' contains incompatible attributes 'EqualsAssignment' and 'Rest'." uci.Name
              true
          else
              false
  