Backwards compatibility and U+2E2F in `Identifier`s

Anne van Kesteren annevk at
Wed Sep 18 12:05:23 PDT 2013

On Mon, Aug 19, 2013 at 5:25 AM, Mathias Bynens <mathias at> wrote:
> After comparing the output, I noticed that both regular expressions are identical except for the following: ECMAScript 5 allows U+2E2F VERTICAL TILDE in `IdentifierStart` and `IdentifierPart`, but ECMAScript 6 / Unicode TR31 doesn’t.

Per ES6 identifiers start with code points whose category is ID_Start
which per includes Lm which per is true for
U+2E2F. So why exactly is it disallowed?

Unless I'm missing something, the discussion we had in TC39 yesterday
was moot, and these bugs are invalid:

And IE10 and maybe IE11 have a bug in not allowing it.


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