[Bug #19291] Rewind to the previous line

When rewinding looking ahead after newline token, also reset the last
line string, the pointers to it, and the location, not only the line
number.

parse.y

@@ -7028,6 +7028,14 @@ add_delayed_token(struct parser_params *p, const char *tok, const char *end, int
     }
 }
 
+static void
+set_lastline(struct parser_params *p, VALUE v)
+{
+    p->lex.pbeg = p->lex.pcur = RSTRING_PTR(v);
+    p->lex.pend = p->lex.pcur + RSTRING_LEN(v);
+    p->lex.lastline = v;
+}
+
 static int
 nextline(struct parser_params *p, int set_encoding)
 {
@@ -7065,10 +7073,8 @@ nextline(struct parser_params *p, int set_encoding)
 	p->heredoc_end = 0;
     }
     p->ruby_sourceline++;
-    p->lex.pbeg = p->lex.pcur = RSTRING_PTR(v);
-    p->lex.pend = p->lex.pcur + RSTRING_LEN(v);
+    set_lastline(p, v);
     token_flush(p);
-    p->lex.lastline = v;
     return 0;
 }
 
@@ -9850,6 +9856,7 @@ parser_yylex(struct parser_params *p)
 	/* fall through */
       case '\n':
 	p->token_seen = token_seen;
+	VALUE prevline = p->lex.lastline;
 	c = (IS_lex_state(EXPR_BEG|EXPR_CLASS|EXPR_FNAME|EXPR_DOT) &&
 	     !IS_lex_state(EXPR_LABELED));
 	if (c || IS_lex_state_all(EXPR_ARG|EXPR_LABELED)) {
@@ -9887,10 +9894,12 @@ parser_yylex(struct parser_params *p)
 	      default:
 		p->ruby_sourceline--;
 		p->lex.nextline = p->lex.lastline;
+		set_lastline(p, prevline);
 	      case -1:		/* EOF no decrement*/
 		lex_goto_eol(p);
 		if (c != -1) {
-		    p->lex.ptok = p->lex.pcur;
+		    token_flush(p);
+		    RUBY_SET_YYLLOC(*p->yylloc);
 		}
 		goto normal_newline;
 	    }

test/ripper/test_scanner_events.rb

@@ -995,4 +995,10 @@ class TestRipper::ScannerEvents < Test::Unit::TestCase
     assert_equal ['U'], scan('tstring_content', '/\\xU/') {|*e| err = e}
     assert_equal [:on_parse_error, "invalid hex escape", "\\x"], err
   end
+
+  def test_error_token
+    src = "{a:,aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n""hello}"
+    err = scan('parse_error', src) {|*e| break e}
+    assert_equal "", err[2]
+  end
 end if ripper_test

test/ruby/test_parse.rb

@@ -14,6 +14,7 @@ class TestParse < Test::Unit::TestCase
 
   def test_error_line
     assert_syntax_error('------,,', /\n\z/, 'Message to pipe should end with a newline')
+    assert_syntax_error("{hello\n  world}", /hello/)
   end
 
   def test_else_without_rescue