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Date: Wed, 30 May 2018 10:11:28 -0700 (PDT)
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Subject: Re: Strings with discriminated records
From: Shark8 <onewingedshark@gmail.com>
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Xref: reader02.eternal-september.org comp.lang.ada:52784
Date: 2018-05-30T10:11:28-07:00
List-Id: <comp.lang.ada>

On Monday, May 28, 2018 at 6:41:41 PM UTC-6, Dan'l Miller wrote:
> On Monday, May 28, 2018 at 1:38:27 PM UTC-5, Shark8 wrote:
>> have bug-boxed on several rename features. (Really frustrating, as I tend to favor RENAME over CONSTANT when possible.)
> 
> What are the precise bugs that you have observed with RENAMES?  Crash of GNAT at compile-time or wrong behavior at runtime?

"Bug-Box" refers to a compile-time crash that prints out an error-message with a surrounding "ASCII-art", really quite annoying when talking about such a basic feature as renaming attributes.

I first encountered it in Byron, where I was renaming attributes that I was using. IIRC, something along the lines of:
DECLARE
  First : Positive renames Input_Vector'First;
  Last  : Natural  renames Input_Vector'Last;
BEGIN
  For Index in First..Last-1 loop
   DECLARE
    Item : Element renames Input_Vector( Index );
    Next : Element renames Input_Vector( Index+1 );
   BEGIN
     -- Do stuff on one item possibly depending on lookahead "Next"...
   END;
  End loop;
END;

If you look in the history of Byron there's one commit where a huge chunk of RENAMES are replaced with the equivalent CONSTANT :=, which is this bug.