Add test cases for args forwarding after rest argument

Author: yui-knk

test/ruby/test_syntax.rb

@@ -1709,6 +1709,8 @@ def test_argument_forwarding
     assert_syntax_error('def foo(...) foo[...] = x; end', /unexpected/)
     assert_syntax_error('def foo(...) foo(...) { }; end', /both block arg and actual block given/)
     assert_syntax_error('def foo(...) defined?(...); end', /unexpected/)
+    assert_syntax_error('def foo(*rest, ...) end', '... after rest argument')
+    assert_syntax_error('def foo(*, ...) end', '... after rest argument')
 
     obj1 = Object.new
     def obj1.bar(*args, **kws, &block)