One yet has to check the pure ES6+ grammar to be LR(1) compatible (the Cover grammar with nodes reinterpretations makes it harder), but for a very practical use-case, e.g. combined with Flow, it'll not be easy to have an automated parser (since Flow's parser uses backtracking for some edge cases which is already not LR-parser).
I have some subset of ES6 working as an example language for Syntax tool[1] (since I just took a bunch of productions from JS), but I haven't tried the full ES6 grammar (not having time to work on this project, since it'll be not a straightforward process of just matching the grammar 1:1 to the parser generator -- based on the above reasons). Long time ago I also had a brief discussion with authors of another popular parser generators for JS. Both didn't try it as well, but mentioned that even for ES5 it was hard to parse e.g. regexp, etc. Someone (with enough time for the project) should just sit, and spend some time actually porting the grammar from the spec on some powerful parsers generator. [1] Syntax: https://github.com/DmitrySoshnikov/syntax [2] https://twitter.com/DmitrySoshnikov/status/666327209959751680 On Wed, Jan 11, 2017 at 10:28 AM, Michael Dyck <[email protected]> wrote: > In the past, it has been said (usually by Brendan Eich) that TC39 intends > that the ECMAScript grammar be LR(1). Is that still the case? (I'm not so > much asking about the "1", but more about the "LR".) > > If so, I'm wondering how lookahead-restrictions (e.g., [lookahead <! > terminals]) fit into the LR approach. It seems like there are three > possibilities: > - modify the grammar (before the parser is constructed), > - modify the construction of the parser, and/or > - modify the operation of the parser. > It's not clear to me that any of these (or any combination of these) will > work. > > Has anyone algorithmically generated an LR parser from the spec grammar? > If so, how did you you handle lookahead-restrictions? > > -Michael > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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