Re: Weird error with Dynamic_Predicate

[Adam Beneschan <adambeneschan@gmail.com>]

For what it's worth, here's the smallest reduced example I can come up with that gives the same error message:

package Prova is
   type Identifier_Name is new String with Dynamic_Predicate => true;
   function Extract_Namespace (Nome : Identifier_Name)
                               return Identifier_Name;
end Prova;

package body Prova is
   function Extract_Namespace (Nome : Identifier_Name)
                               return Identifier_Name
   is
      Idx : Natural := Ada.Strings.Fixed.Index (String (Nome), ".");
   begin
      return "ns";
   end Extract_Namespace;
end Prova;

This is with GCC 4.5.4 (20120510).

                            -- Adam


On Monday, May 12, 2014 12:47:41 PM UTC-7, mockturtle wrote:
> Dear all,
> 
> I am experiencing an error that is making me crazy and I was wondering if someone can help.
> 
> 
> 
> Some background: I want to define a type that represents an "identifier."  The identifier can assume two forms: 
> 
>  - qualified (es. namespace.foo)
> 
>  - not qualified (es. foo)
> 
> 
> 
> The two components (namespace and name) have the usual syntax (letters, digits and underscore).  Note that there are at most two components.  I want to use the aspect Dynamic_Predicate to enforce (and document) the right syntax.
> 
> 
> 
> You can find prova.ads and prova.adb at the end of this message.  I am using GPS 5.2.1 (20130102) and when I try to compile I get the obscure message
> 
> 
> 
>   29:32 error: conversion to incomplete type
> 
>   29:32 confused by earlier errors, bailing out
> 
> 
> 
> on >> prova.ads <<.  If I try to do "check semantic" on prova.ads and prova.adb, everything is fine.  
> 
> 
> 
> 
> 
> Any ideas?  Is it a compiler bug or am I doing something wrong?  Updating the compiler in this moment it would be a little pain for me (for several reasons), so I would like to be sure that I am not doing some subtle error before trying the update path.
> 
> 
> 
> Thank you in advance 
> 
> 
> 
> Riccardo
> 
> 
> 
> 
> 
> 
> 
> --- prova.ads ---
> 
> with Ada.Characters.Handling;     use Ada.Characters.Handling;
> 
> with Ada.Strings.Fixed;
> 
> 
> 
> package Prova is
> 
>    type Identifier_Name is new
> 
>      String
> 
>        with Dynamic_Predicate =>
> 
>          ((for all I in Identifier_Name'Range =>
> 
>              Is_Alphanumeric (Identifier_Name (I))
> 
>            or Identifier_Name (I) = '_'
> 
>            or Identifier_Name (I) = '.')
> 
>           and
> 
>             (not (Identifier_Name (Identifier_Name'First) in '0' .. '9'))
> 
>           and
> 
>             (Identifier_Name (Identifier_Name'First) /= '.')
> 
>           and
> 
>             Ada.Strings.Fixed.Count (String (Identifier_Name), ".") <= 1);
> 
> 
> 
>    function Is_Qualified (Item : Identifier_Name) return Boolean
> 
>      is (Ada.Strings.Fixed.Count (String (Item), ".") = 1);
> 
> 
> 
>    subtype Namespace_Identifier is Identifier_Name
> 
>    with Dynamic_Predicate => not Is_Qualified (Namespace_Identifier);
> 
> 
> 
>    subtype Full_Identifier is Identifier_Name
> 
>    with Dynamic_Predicate => Is_Qualified (Full_Identifier);
> 
> 
> 
> 
> 
>    function Extract_Namespace (Nome : Full_Identifier)
> 
>                                return Namespace_Identifier;
> 
> 
> 
> end Prova;
> 
> 
> 
> --- prova.adb --- 
> 
> 
> 
> package body Prova is
> 
> 
> 
> 
> 
>    -----------------------
> 
>    -- Extract_Namespace --
> 
>    -----------------------
> 
> 
> 
>    function Extract_Namespace (Nome : Full_Identifier)
> 
>                                return Namespace_Identifier
> 
>    is
> 
>       Idx : Natural := Ada.Strings.Fixed.Index (String (Nome), ".");
> 
>    begin
> 
>       return Namespace_Identifier (Nome (Nome'First .. Idx - 1));
> 
>    end Extract_Namespace;
> 
> 
> 
> end Prova;
> 
> ----