[ruby-core:120736] [Ruby master Feature#21047] Change `*nil` to not call `nil.to_a`, for consistency with `**nil`

[ruby-core:120736] [Ruby master Feature#21047] Change `*nil` to not call `nil.to_a`, for consistency with `**nil`

[jeremyevans0 (Jeremy Evans) via ruby-core]

Issue #21047 has been reported by jeremyevans0 (Jeremy Evans).

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Feature #21047: Change `*nil` to not call `nil.to_a`, for consistency with `**nil`
https://bugs.ruby-lang.org/issues/21047

* Author: jeremyevans0 (Jeremy Evans)
* Status: Open
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In Ruby 3.3, we started accepting `**nil` for keyword splats. This does not call `nil.to_hash`, unlike other uses of `**` for splatting.  This made `**nil` handling inconsistent with `*nil` handling, as `*nil` historically has called `nil.to_a`.  I propose we make them consistent, by having `*nil` not call `nil.to_a`.

Advantage: In addition to more consistent behavior with `**nil`, making `*nil` not call `nil.to_a` opens up new a optimization opportunity, since it allows `*nil` to be optimized to not allocate an array, similar to how `**nil` is already optimized to not allocate a hash.

Disadvantage: Minor backwards compatibility breakage, though it is very unlikely any code other than test code will break, because overriding `nil.to_a` to return anything other than the empty array would likely break any large Ruby application.

I've submitted a pull request to implement this: https://github.com/ruby/ruby/pull/12597



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[ruby-core:120739] [Ruby master Feature#21047] Change `*nil` to not call `nil.to_a`, for consistency with `**nil`

[matz (Yukihiro Matsumoto) via ruby-core]

Issue #21047 has been updated by matz (Yukihiro Matsumoto).


Accepted.

Matz.


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Feature #21047: Change `*nil` to not call `nil.to_a`, for consistency with `**nil`
https://bugs.ruby-lang.org/issues/21047#change-111570

* Author: jeremyevans0 (Jeremy Evans)
* Status: Open
----------------------------------------
In Ruby 3.3, we started accepting `**nil` for keyword splats. This does not call `nil.to_hash`, unlike other uses of `**` for splatting.  This made `**nil` handling inconsistent with `*nil` handling, as `*nil` historically has called `nil.to_a`.  I propose we make them consistent, by having `*nil` not call `nil.to_a`.

Advantage: In addition to more consistent behavior with `**nil`, making `*nil` not call `nil.to_a` opens up new a optimization opportunity, since it allows `*nil` to be optimized to not allocate an array, similar to how `**nil` is already optimized to not allocate a hash.

Disadvantage: Minor backwards compatibility breakage, though it is very unlikely any code other than test code will break, because overriding `nil.to_a` to return anything other than the empty array would likely break any large Ruby application.

I've submitted a pull request to implement this: https://github.com/ruby/ruby/pull/12597



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