From: "matz (Yukihiro Matsumoto) via ruby-core" <ruby-core@...>
Date: 2023-04-13T07:26:41+00:00
Subject: [ruby-core:113214] [Ruby master Bug#19533] Behavior of ===/include? on a beginless/endless range (nil..nil) changed in ruby 3.2

Issue #19533 has been updated by matz (Yukihiro Matsumoto).


It is an unintentional behavior. I agree to fix `nil .. nil` case.

Matz.


----------------------------------------
Bug #19533: Behavior of ===/include? on a beginless/endless range (nil..nil) changed in ruby 3.2
https://bugs.ruby-lang.org/issues/19533#change-102757

* Author: knu (Akinori MUSHA)
* Status: Open
* Priority: Normal
* Target version: 3.2
* ruby -v: ruby 3.2.1 (2023-02-08 revision 31819e82c8) [x86_64-darwin22]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
Starting from Ruby 2.7.0 a range `nil..nil` used to match any value until 3.2.0-preview3, but 3.2.0-rc1 started to reject it.

```
% docker run -it --rm rubylang/all-ruby ./all-ruby -e 'p( (nil..nil) === 1 )'
(snip)
ruby-2.6.10           false
ruby-2.7.0-preview1   true
...
ruby-3.2.0-preview3   true
ruby-3.2.0-rc1        -e:1:in `===': cannot determine inclusion in beginless/endless ranges (TypeError)

                      p( (nil..nil) === 1 )
                                        ^
                        from -e:1:in `<main>'
                  exit 1
...
ruby-3.2.1            -e:1:in `===': cannot determine inclusion in beginless/endless ranges (TypeError)

                      p( (nil..nil) === 1 )
                                        ^
                        from -e:1:in `<main>'
```

The previous behavior was so useful because when you have optional lower and upper bounds `lbound..rbound` would always work regardless of each end being nil or not.

There is no mention of this in doc/NEWS/NEWS-3.2.0.md, so I'm afraid it was caused unintentionally while fixing other problems.

```
% docker run -it --rm rubylang/all-ruby ./all-ruby -e 'p( (nil..nil).cover?(1) )'
(snip)
ruby-2.6.10           false
ruby-2.7.0-preview1   true
...
ruby-3.2.1            true
```

This was pointed out by the following blog article (written in Japanese) as a "pitfall" that you need to work around when upgrading Ruby from 3.0/3.1 to 3.2.
https://blog.studysapuri.jp/entry/2023/03/16/ujihisa-ruby32#endless-range%E3%81%AE%E6%8C%99%E5%8B%95%E3%81%AE%E5%A4%89%E6%9B%B4



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