Issue #14183 has been updated by Eregon (Benoit Daloze).


I agree with Jeremy here, the current idea seems too incompatible and will require too many changes (no matter the gain).
And those changes cannot easily be automated either, they need careful considerations.

I think we need to compromise here, to avoid too many incompatible changes, especially on methods which have no keyword arguments and where the intention is clear.
I would think the number of methods like debug() is a tiny fraction of the number of places we'd need to change if hash-without-braces is no longer supported.

IMHO such a method with rest + kwargs seems a bad design in the first place as the arguments are too complex. That debug method could only accept one argument for instance.

Also, how should `foo(1, "foo" => "bar")` behave?
Should it be like `foo(1, {"foo" => "bar"})`? In this case the syntax is inconsistent with `foo(1, foo: "bar")` where having or leaving out the braces matter.
Or does the `=>` imply the braces?
I believe all Rubyists are used to `foo(1, :foo => "bar")` and  `foo(1, foo: "bar")` being identical.

BTW, `p foo: 1` will no longer work then, and `p({foo: 1})` would be required, which feels very *unlike* Ruby, and is just impractical when debugging.

----------------------------------------
Feature #14183: "Real" keyword argument
https://bugs.ruby-lang.org/issues/14183#change-73881

* Author: mame (Yusuke Endoh)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: Next Major
----------------------------------------
In RubyWorld Conference 2017 and RubyConf 2017, Matz officially said that Ruby 3.0 will have "real" keyword arguments.  AFAIK there is no ticket about it, so I'm creating this (based on my understanding).

In Ruby 2, the keyword argument is a normal argument that is a Hash object (whose keys are all symbols) and is passed as the last argument.  This design is chosen because of compatibility, but it is fairly complex, and has been a source of many corner cases where the behavior is not intuitive.  (Some related tickets: #8040, #8316, #9898, #10856, #11236, #11967, #12104, #12717, #12821, #13336, #13647, #14130)

In Ruby 3, a keyword argument will be completely separated from normal arguments.  (Like a block parameter that is also completely separated from normal arguments.)
This change will break compatibility; if you want to pass or accept keyword argument, you always need to use bare `sym: val` or double-splat `**` syntax:

```
# The following calls pass keyword arguments
foo(..., key: val)
foo(..., **hsh)
foo(..., key: val, **hsh)

# The following calls pass **normal** arguments
foo(..., {key: val})
foo(..., hsh)
foo(..., {key: val, **hsh})

# The following method definitions accept keyword argument
def foo(..., key: val)
end
def foo(..., **hsh)
end

# The following method definitions accept **normal** argument
def foo(..., hsh)
end
```

In other words, the following programs WILL NOT work:

```
# This will cause an ArgumentError because the method foo does not accept keyword argument
def foo(a, b, c, hsh)
  p hsh[:key]
end
foo(1, 2, 3, key: 42)

# The following will work; you need to use keyword rest operator explicitly
def foo(a, b, c, **hsh)
  p hsh[:key]
end
foo(1, 2, 3, key: 42)

# This will cause an ArgumentError because the method call does not pass keyword argument
def foo(a, b, c, key: 1)
end
h = {key: 42}
foo(1, 2, 3, h)

# The following will work; you need to use keyword rest operator explicitly
def foo(a, b, c, key: 1)
end
h = {key: 42}
foo(1, 2, 3, **h)
```

I think here is a transition path:

* Ruby 2.6 (or 2.7?) will output a warning when a normal argument is interpreted as keyword argument, or vice versa.
* Ruby 3.0 will use the new semantics.



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