Fix the error token on "invalid hex escape"

* parse.y (tok_hex): flush token after dispatching the "invalid
  hex escape" parse error.

parse.y

@@ -6133,8 +6133,8 @@ tok_hex(struct parser_params *p, size_t *numlen)
 
     c = scan_hex(p->lex.pcur, 2, numlen);
     if (!*numlen) {
-	p->lex.ptok = p->lex.pcur;
 	yyerror0("invalid hex escape");
+	token_flush(p);
 	return 0;
     }
     p->lex.pcur += *numlen;

test/ripper/test_scanner_events.rb

@@ -976,4 +976,14 @@ class TestRipper::ScannerEvents < Test::Unit::TestCase
     assert_match /Invalid char/, err[1]
     assert_equal "\e", err[2]
   end
+
+  def test_invalid_hex_escape
+    err = nil
+    assert_equal ['U'], scan('tstring_content', '"\\xU"') {|*e| err = e}
+    assert_equal [:on_parse_error, "invalid hex escape", "\\x"], err
+
+    err = nil
+    assert_equal ['U'], scan('tstring_content', '/\\xU/') {|*e| err = e}
+    assert_equal [:on_parse_error, "invalid hex escape", "\\x"], err
+  end
 end if ripper_test

test/ruby/test_parse.rb

@@ -513,7 +513,7 @@ class TestParse < Test::Unit::TestCase
     mesg = 'from the backslash through the invalid char'
 
     e = assert_syntax_error('"\xg1"', /hex escape/)
-    assert_equal('   ^', e.message.lines.last, mesg)
+    assert_equal(' ^~', e.message.lines.last, mesg)
 
     e = assert_syntax_error('"\u{1234"', 'unterminated Unicode escape')
     assert_equal('        ^', e.message.lines.last, mesg)