ripper: add kwrest_param parser event

* parse.y (f_kwrest): Dispatch kwrest_param event. This is especially
  useful for unnamed kwrest parameter for which we expose the internal
  ID currently.  [ruby-core:75528] [Feature #12387]

* test/ripper/dummyparser.rb (on_kwrest_param): Add handler for
  kwrest_param parser event.

* test/ripper/test_parser_events.rb (test_params): Adapt to the change
  in DummyParser.
  (test_kwrest_param): Test that kwrest_param event handler is called.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59382 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

parse.y

@@ -4492,12 +4492,20 @@ kwrest_mark	: tPOW
 f_kwrest	: kwrest_mark tIDENTIFIER
 		    {
 			shadowing_lvar(get_id($2));
+		    /*%%%*/
 			$$ = $2;
+		    /*%
+			$$ = dispatch1(kwrest_param, $2);
+		    %*/
 		    }
 		| kwrest_mark
 		    {
+		    /*%%%*/
 			$$ = internal_id();
 			arg_var($$);
+		    /*%
+			$$ = dispatch1(kwrest_param, Qnil);
+		    %*/
 		    }
 		;
 

test/ripper/dummyparser.rb

@@ -153,6 +153,10 @@ class DummyParser < Ripper
     "*#{var}"
   end
 
+  def on_kwrest_param(var)
+    "**#{var}"
+  end
+
   def on_blockarg(var)
     "&#{var}"
   end

test/ripper/test_parser_events.rb

@@ -893,7 +893,7 @@ 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_params_mlhs
@@ -1079,6 +1079,15 @@ 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}