I presume this is an oversight from the CodeMirror developer, or the unicode property escapes don't break anything in older browsers. I suspect the latter, as I see a try/catch in the code.

CodeMirror is advertised as being distributed in purely ES2015 syntax.

I'm not sure anything needs to be done here, unless we are aware of breakage in browsers we are meant to support.

In T382350#10411205, @MusikAnimal wrote:

I suspect the latter, as I see a try/catch in the code.

Thanks for pointing this out! I test some malformed RegExp constructor calls in different modern browsers, and the try-catch block works well to prevent syntax errors.

Em, it should not be a problem as long as the linter, validator and minifier does not do wrong. All of these currently does not touch inside dynamically created regex at all.