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

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


On Mon, Aug 19, 2013 at 5:25 AM, Mathias Bynens <mathias at qiwi.be> 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 http://www.unicode.org/reports/tr31/ includes Lm which per
http://www.unicode.org/Public/UNIDATA/UnicodeData.txt 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:

https://bugs.ecmascript.org/show_bug.cgi?id=1802
https://bugzilla.mozilla.org/show_bug.cgi?id=917436
https://bugs.webkit.org/show_bug.cgi?id=121541
https://code.google.com/p/v8/issues/detail?id=2892

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


-- 
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