[ruby-core:113184] [Ruby master Feature#19588] Allow Comparable#clamp(min, max) to accept nil as a specification

Issue #19588 has been updated by sawa (Tsuyoshi Sawada).


Currently, `clamp` accepts `min` and `max` simultaneously being `nil`. I think it should be synchronized with whether `(nil..nil).include?(foo)`is accepted or not. Cf. #19533.

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Feature #19588: Allow Comparable#clamp(min, max) to accept nil as a specification
https://bugs.ruby-lang.org/issues/19588#change-102722

* Author: kyanagi (Kouhei Yanagita)
* Status: Open
* Priority: Normal
----------------------------------------
`Comparable#clamp(min, max)` (with two arguments) accepts `nil`. This behaves the same as beginless/endless Range.

~~~ruby
5.clamp(nil, 0)   # => 0
5.clamp(10, nil)  # => 10
5.clamp(..0)      # => 0
5.clamp(10..)     # => 10
~~~

This behavior is not documented. Presumably, this was not introduced intentionally.

The old Rubies did not accept accept a `Range` argument.

In Ruby 2.7, accepting `Range` as an argument was introduced.
At that time, the approach of passing `nil` as a two-argument method was also discussed but not adopted,
and using Range was chosen instead. https://bugs.ruby-lang.org/issues/14784

However, in Ruby 3.0, the behavior of `clamp` has changed to accept `nil`.
This change is not documented in the NEWS or the documentation for `clamp`,
and I believe that it was not an intentional change.

~~~
% docker run -it --rm rubylang/all-ruby env ALL_RUBY_SINCE=ruby-2.4.0 ./all-ruby -e "p 5.clamp(0, nil)"
ruby-2.4.0          -e:1:in `clamp': comparison of Integer with nil failed (ArgumentError)
                        from -e:1:in `<main>'
                exit 1
...
ruby-2.7.8          -e:1:in `clamp': comparison of Integer with nil failed (ArgumentError)
                        from -e:1:in `<main>'
                exit 1
ruby-3.0.0-preview1 5
...
ruby-3.2.2          5
~~~

It seems that https://github.com/ruby/ruby/commit/a93da4970be44a473b7b42e7516eb2663dece2c3 brought about this change.

How about making the current behavior a specification?
It has been three years since the behavior changed, and I don't see much point in prohibiting `nil` now.




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