[Webkit-unassigned] [Bug 34019] custom-written parser

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=34019





--- Comment #4 from Zoltan Herczeg <zherczeg at webkit.org>  2010-01-22 14:57:39 PST ---
(In reply to comment #3)
> I'm unsure why the syntax checker is separate from the parser.  Syntax checking
> is basically answering the question "can i parse this".

The grammar do both syntax checking and generating nodes. Syntax checker only
checks syntax, and used only for skipping nested function bodies. That is what
I tried to explain. They have lot in common, but they have differences as well.

> There are semantic checks that we will want to do while parsing:
>    the various "features" we track
>    variable and function accumulation
>    partial AST generation

That is what my grammar do :) It is "binary compatible" with the bison parser.
The only thing which is not tracked is the "arguments feature" because I don't
really understand its purpose yet :(

> New things we _must_ be able to do in the new parser:
>    strict mode identification needs to be done during the parse stage and
> alters the state of the parser to reject constructs that lax mode would allow,
> and produces parse time errors instead).  For efficiency reasons this basically
> forces us into a recursive-descent parser :-/

I saw the new ECMA standard, and I think I can hanle the strict mode
restrictions, at least those which I saw (local identifiers cannot be used
before a var declaration seems a more complex one, since you have to store all
the primary identifiers during parsing). I checked wikipedia, and turned out my
parser is a predictive parser (uses a stack, but never backtracks). The
predictive parser belongs to the family of recursive descent parsers.

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