ripper: dispatch new parser event 'kwrest_param' on f_kwresttopic/ripper-unnamed-kwrest

Ripper has an issue in handling bare kwrest:

  $ ruby -rpp -rripper -e'pp Ripper.sexp("def a(**) end")'
  [:program,
   [[:def,
     [:@ident, "a", [1, 4]],
     [:paren, [:params, nil, nil, nil, nil, nil, 183, nil]],
     [:bodystmt, [[:void_stmt]], nil, nil, nil]]]]

The mysterious 183 is the problem: this is an ID generated by
internal_id(). This patch introduces a new 'kwrest_param' parser event
that works just like 'rest_param' event that corresponds to rest params
(def a(*rest) end). After applying this, the result will be:

  $ ruby -rpp -rripper -e'pp Ripper.sexp("def a(**name) end")'
  [:program,
   [[:def,
     [:@ident, "a", [1, 4]],
     [:paren,
      [:params,
       nil,
       nil,
       nil,
       nil,
       nil,
       [:kwrest_param, [:@ident, "name", [1, 8]]],
       nil]],
     [:bodystmt, [[:void_stmt]], nil, nil, nil]]]]

  $ ruby -rpp -rripper -e'pp Ripper.sexp("def a(**) end")'
  [:program,
   [[:def,
     [:@ident, "a", [1, 4]],
     [:paren, [:params, nil, nil, nil, nil, nil, [:kwrest_param, nil], nil]],
     [:bodystmt, [[:void_stmt]], nil, nil, nil]]]]

* parse.y (f_kwrest): dispatch kwrest_param event, just like rest_param.
* test/ripper/dummyparser.rb (on_kwrest_param): add kwrest_param parser
  event handler.
* test/ripper/test_parser_events.rb (test_params): adjust.
* test/ripper/test_parser_events.rb (test_kwrest_param): test that
  kwrest_param event handler is properly called.

1 files changed, 10 insertions, 1 deletions

diff --git a/test/ripper/test_parser_events.rb b/test/ripper/test_parser_events.rb
index 540d36e4d9..070f4d7614 100644
--- a/test/ripper/test_parser_events.rb
+++ b/test/ripper/test_parser_events.rb
@@ -863,7 +863,7 @@ class TestRipper::ParserEvents < Test::Unit::TestCase
     thru_params = false
     parse('a {|**x|}', :on_params) {|_, *v| thru_params = true; arg = v}
     assert_equal true, thru_params
-    assert_equal [nil, nil, nil, nil, nil, "x", nil], arg
+    assert_equal [nil, nil, nil, nil, nil, "**x", nil], arg
   end
 
   def test_paren
@@ -971,6 +971,15 @@ class TestRipper::ParserEvents < Test::Unit::TestCase
     assert_equal true, thru_rest_param
   end
 
+  def test_kwrest_param
+    thru_kwrest = false
+    parse('def a(**) end', :on_kwrest_param) {|n, val| thru_kwrest = val}
+    assert_equal nil, thru_kwrest
+    thru_kwrest = false
+    parse('def a(**x) end', :on_kwrest_param) {|n, val| thru_kwrest = val}
+    assert_equal "x", thru_kwrest
+  end
+
   def test_retry
     thru_retry = false
     parse('retry', :on_retry) {thru_retry = true}