[ruby-dev:52105] [Ruby master Bug#20675] Parse error with required kwargs and omitted parens

["jeremyevans0 (Jeremy Evans) via ruby-dev" <ruby-dev@ml.ruby-lang.org>]

Issue #20675 has been updated by jeremyevans0 (Jeremy Evans).


The reason for this inconsistency is backwards compatibility, so as not to break existing code when omitted hash value support was added in Ruby 3.1.

There is historical precedence for breaking backwards compatibility for a very similar case.  In this example:

```ruby
def foo arg:
  123
  arg
end
foo
# Ruby < 2.0: SyntaxError
# Ruby 2.0: 123
# Ruby >= 2.1: ArgumentError, missing keyword: arg 
```

There was no deprecation warning for the change in 2.1.  I think if we want to change behavior for `foo arg:<newline>value` from `foo(arg: value)` to `foo(arg:); value`, we should add a deprecation warning in 3.4, and then change the behavior in 3.5.

----------------------------------------
Bug #20675: Parse error with required kwargs and omitted parens
https://bugs.ruby-lang.org/issues/20675#change-109432

* Author: matz (Yukihiro Matsumoto)
* Status: Open
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
As pointed out in https://github.com/mruby/mruby/issues/6268, keyword arguments without surrounding parens are a bit confusing, e.g.

```ruby
def foo arg:
  123
end
```

is parsed as

```ruby
def foo(arg:)
  123
end
```

where

```ruby
k=25
f k:
    10
```

is parserd as

```ruby
k=25
f(k: 10)
```

In summary, should we ignore newlines after keyword labels? Should we make them behave consistent?

Matz.




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