From: "Dan0042 (Daniel DeLorme) via ruby-core" <ruby-core@...>
Date: 2023-12-18T17:03:01+00:00
Subject: [ruby-core:115774] [Ruby master Feature#20070] commas in pattern match

Issue #20070 has been updated by Dan0042 (Daniel DeLorme).


I understand what you mean but this is not about keeping strict consistency per se. It's a specific case that I find confusing because it does something different from what it looks like to me, based on my personal experience.

> ```ruby
> case params
> in name:, role: # that's not alternatives, right?
> ```
It's not alternatives? I guess so, but what it does is not intuitively obvious to me. I would write that code as `in {name:, role:}` to avoid confusion. But you make a good point; there's no equivalent `when` clause so interpreting it as alternatives might be just as confusing.

My confusion has to do when commas are used at the "top level" of `case..in`, not so much with `=>` and right-hand assignment. Note that if you put `[1, 2] => a, b` inside a `case..in` it has a considerably different meaning:
```ruby
v = [[1,2],3]
case v 
in [1, 2] => a, b
  p a=>b
end #=> {[1, 2]=>3}
```
The above behavior become clearer (imho) when you write the brackets:
```ruby
v = [[1,2],3]
case v 
in [[1, 2] => a, b]
  p a=>b
end #=> {[1, 2]=>3}
```


----------------------------------------
Feature #20070: commas in pattern match
https://bugs.ruby-lang.org/issues/20070#change-105711

* Author: Dan0042 (Daniel DeLorme)
* Status: Open
* Priority: Normal
----------------------------------------
In pattern matching, `case v; in 1,2,3` is a synonym for `case v; in [1,2,3]`

This is the one thing that keeps confusing me, that I haven't been able to get used to. Because I'm used to `case v; when 1,2,3` it feels like `case v; in 1,2,3` should have a similar meaning. So it's possible to omit the square brackets but honestly I don't see much point for that, it just makes it look to me like something it is not.

In other words, I feel it would be far more intuitive (at least to me) if
```ruby
case v
in 1,2,3
```
was a synonym for
```ruby
case v
in 1
in 2
in 3
```
or possibly a synonym for
```ruby
case v
in (1|2|3)
```
which would make it similar to the syntax in `rescue A, B, C => err`

Is it too late to change this?



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