[ruby-core:97349] [Ruby master Feature#16670] Reverse order of `expression` in `pattern` for 1-line pattern matching while it's still experimental

Issue #16670 has been updated by zverok (Victor Shepelev).


....and also, one more example, now just in Ruby:

```ruby
# that's what we always had:
a, b = [1, 2, 3]
# could be pretty complicated:
a, (b, c), *d = [1, [2, 3], 4, 5]

# ...but now let's imagine we need to unpack a simple Hash...
# ...that's how it will look:
{a: 1, b: 2, c: 3} in {a:, **rest}
# ...while "intutively" I always want it look as close array examples above as possible:
{a:, **rest} in {a: 1, b: 2, c: 3}
```

I believe it should've been discussed on "standalone `in`" introduction ticket (and probably it was found that the "natural" order will be impossible to parse?), but I don't see detailed discussion here: #15865

----------------------------------------
Feature #16670: Reverse order of `expression` in `pattern` for 1-line pattern matching while it's still experimental
https://bugs.ruby-lang.org/issues/16670#change-84469

* Author: ttilberg (Tim Tilberg)
* Status: Open
* Priority: Normal
----------------------------------------
Currently the 1-line syntax for pattern matching is:

```
# Usage: <expression> in <pattern>

expression = {
  pattern: "Example"
}

expression in {pattern: something}
# something => "Example"
```

Is it technically possible, and desirable to switch the order of this syntax to:

```
# Usage: <pattern> in <expression>

expression = {
  pattern: "Example"
}

{pattern: something} in expression
# something => "Example"

```
?

Here are my reasons:

- It is more intuitive in English -- we are "finding a pattern in something". Finding "something in a pattern" doesn't seem to make sense.
- Assignment is happening, and this keeps assignment on the left side of the operator which feels more natural.
- It matches existing behavior with the workings of the case statement:

Understanding that a `case` block evaluates each `when` expression using `when_expression === case_expression` makes more consistency with `when_pattern in case_pattern` using the new operator.

```
case something
when /pattern/
end

# is equivalent to

/pattern/ === something

# This creates more parity with

case something
in {pattern: x}

# would be equivalent to

{pattern: x} in something
```


Please see the following discussion on Reddit: https://www.reddit.com/r/ruby/comments/favshb/27s_pattern_matching_official_docs_recently_merged/fj2c7ng/



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