Created attachment 8
patch for this issue
According to section 22.214.171.124
let P be the empty String if pattern is undefined
then, P is empty String "".
If P is the empty String, this specification can be met by letting S be "(?:)".
then, S is string "(?:)".
The source property of the newly constructed object is set to S.
So, new RegExp().source is "(:?)".
Exceptional spot Yusuke, and all browsers I tried this on get it wrong. I've added a regression to ensure RegExp().source!==="" and this will be a part of Microsoft's next contribution to test262.
While 126.96.36.199 recommends empty RegExp's source properties be "(?:)", the wordage doesn't actually require this. Consequently, I've simply removed the checks for '*.source === ""' in the Sputnik tests.