Add support for anonymous rest and keyword rest argument forwarding

This allows for the following syntax:

```ruby
def foo(*)
  bar(*)
end
def baz(**)
  quux(**)
end
```

This is a natural addition after the introduction of anonymous
block forwarding.  Anonymous rest and keyword rest arguments were
already supported in method parameters, this just allows them to
be used as arguments to other methods.  The same advantages of
anonymous block forwarding apply to rest and keyword rest argument
forwarding.

This has some minor changes to #parameters output.  Now, instead
of `[:rest], [:keyrest]`, you get `[:rest, :*], [:keyrest, :**]`.
These were already used for `...` forwarding, so I think it makes
it more consistent to include them in other cases.  If we want to
use `[:rest], [:keyrest]` in both cases, that is also possible.

I don't think the previous behavior of `[:rest], [:keyrest]` in
the non-... case and `[:rest, :*], [:keyrest, :**]` in the ...
case makes sense, but if we did want that behavior, we'll have to
make more substantial changes, such as using a different ID in the
... forwarding case.

Implements [Feature #18351]

1 files changed, 28 insertions, 0 deletions

diff --git a/test/ruby/test_syntax.rb b/test/ruby/test_syntax.rb
index b71f492f9c..622527dafe 100644
--- a/test/ruby/test_syntax.rb
+++ b/test/ruby/test_syntax.rb
@@ -78,6 +78,34 @@ class TestSyntax < Test::Unit::TestCase
     end;
   end
 
+  def test_anonymous_rest_forwarding
+    assert_syntax_error("def b; c(*); end", /no anonymous rest parameter/)
+    assert_syntax_error("def b; c(1, *); end", /no anonymous rest parameter/)
+    assert_separately([], "#{<<-"begin;"}\n#{<<-'end;'}")
+    begin;
+        def b(*); c(*) end
+        def c(*a); a end
+        def d(*); b(*, *) end
+        assert_equal([1, 2], b(1, 2))
+        assert_equal([1, 2, 1, 2], d(1, 2))
+    end;
+  end
+
+  def test_anonymous_keyword_rest_forwarding
+    assert_syntax_error("def b; c(**); end", /no anonymous keyword rest parameter/)
+    assert_syntax_error("def b; c(k: 1, **); end", /no anonymous keyword rest parameter/)
+    assert_separately([], "#{<<-"begin;"}\n#{<<-'end;'}")
+    begin;
+        def b(**); c(**) end
+        def c(**kw); kw end
+        def d(**); b(k: 1, **) end
+        def e(**); b(**, k: 1) end
+        assert_equal({a: 1, k: 3}, b(a: 1, k: 3))
+        assert_equal({a: 1, k: 3}, d(a: 1, k: 3))
+        assert_equal({a: 1, k: 1}, e(a: 1, k: 3))
+    end;
+  end
+
   def test_newline_in_block_parameters
     bug = '[ruby-dev:45292]'
     ["", "a", "a, b"].product(["", ";x", [";", "x"]]) do |params|