Editor smears annotations when scrolled horizontally, annotations not in scroll area

When an annotation, such as those produced by the clang analyzer, extends off the right edge of the text editor, and the editor is scrolled horizontally to the right, the annotation is "smeared" – that is, it's not repainted, the old bit just stays there:

Additionally, and presumably related, annotations do not contributed to the calculated horizontal scroll area of the editor, and thus the scrollbar does not appear if all code is in view even if annotations extend off the right side.

As a consequence, the only way to read annotations, really, is to adjust the editor pane width so that they come into view (redraw is OK in this case afaict).

See attached screengrab video (I could not get a gif to be < 25MB or so and didn't want to be rude). It is also watchable here.