[feature] Mandatory end designator

[joaopsazevedo]

Summary

This RFC proposes to standardize and mandate the use of the designator name in the end statement for all block-like constructs.

Motivation

The primary motivation for this change is to improve language consistency and code readability in long or nested code blocks, by explicitly linking the end of a block to its beginning.

Caveats and alternatives

Backwards incompatible. Alternatively, only deprecate end record; in favor of an optional end <record_name>;.

[clairedross]

I think that, if we want to introduce a backward-incompatible change, we need a very good motivation for it. Here it looks a bit cosmetic to me...

[sttaft]

This would make for an excellent "Restriction" which projects could impose on themselves. E.g.:

pragma Restrictions (Mandatory_End_Designators);

As a language change, it seems very incompatible for what is essentially a style restriction. Remember there are more than a billion lines of Ada code that periodically will want to be recompiled with an up-to-date compiler.

Note that Ada 2022 includes the permission to add an end designator after "end record":

https://ada-rapporteur-group.github.io/ARM/Ada_202Y/AA-3-8.html#p3

We explicitly considered making the word "record" optional, with appropriate rationale provided in the AI that introduced this new syntax:

http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai12s/ai12-0213-1.txt?rev=Top1.7

We concluded that having that sort of option is not a feature, as then a project would just want to mandate a particular choice. End designators were already optional in most cases, so it made sense to follow that model here as well. Including the nature of the construct as part of the "end" matches the choice for "end loop ", and so there was precedent to include the kind of construct in the ending pattern, and it would mean existing Ada code with records would not suddenly appear inconsistent.