Re: Quick question regarding limited type return syntax

[Adam Beneschan <adambeneschan@gmail.com>]

On Wednesday, July 30, 2014 4:51:10 PM UTC-7, NiGHTS wrote:
> I am designing a package which features a "Create" function that returns a newly instantiated "Object" which is a discriminated limited type. The code compiles and operates correctly but gives me a warning that "New_Object" is not used. See below (ellipses represent omitted code):

> package Test is
>    type Object (Parameters : access String) is tagged limited private;
>    function Create (...) return Object;
>    ...
> private
>    type Object (Parameters : access String) is tagged limited
>    record
>       Database : PQ.Database (Parameters);
>       ...
>    end record;
>    ...
> end Test;
> 
> package body Test is
>    function Create(...) return Object is
>       ...
>    begin
>       return New_Object : Object (Connection_String'Access) do 
>          null;
>       end return;
>    end;
>    ...
> end Test;

> To remove this warning I've tried this:
> 
>    return  Object (Connection_String'Access) do null; end return;
> 
> and it gives an error about expecting a ';'. I've also tried this:
> 
> 
> 
>    return  Object (Connection_String'Access);
> 
> Compiler tells me "argument of conversion cannot be access". 
> 
> I have tried other syntax variants but all produce errors. My goal here is to avoid using "new" which is why I am trying to return the instance in this way.
> 
> How can I rewrite this code so that I won't get any errors or warnings?

What is a PQ.Database?  

I've tried this with various dummy types for the Database, and when I get a warning it's that the object is "read but never assigned".  Is that the warning you're getting?  That's different from a warning that says it's never used.

It appears to me that if this field were assigned in New_Object, or if Database had an initial value in the record or if all components of Database had initial values, you wouldn't get the warning.

                              -- Adam