Showing squiggles at the end of a line?

If you forget to type a semicolon at the end of a statement in Visual Studio, the squiggle will be placed at the end of the line, after the last visible character.

How do you get a similar result with SyntaxEditor (using a custom parser)? My expectation would be to create a ParseError with a PositionRange that somewhow includes the newline, but I can't figure out how to get it to work.

See also the C# editor demo in the sample browser that shows the same problem - the syntax editor on line 22 is invisible in the editor.