[Webkit-unassigned] [Bug 174212] [JSC] Add support for class fields to the parser

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Jul 6 14:18:13 PDT 2017


--- Comment #3 from Saam Barati <sbarati at apple.com> ---
(In reply to Xan Lopez from comment #0)
> Created attachment 314736 [details]
> WIP data field parsing
> Ok, a really simple/rough WIP, but I think enough to ask a couple questions.
> I had a larger patch with a new parseDataField() method (lots of copy/paste)
> that I'd run in a loop at the begining of parseClass() until it stopped
> parsing fields, but then realized data fields can be mixed with methods in
> any order, so had to scrap that. Now I just branch after parsing an
> identifier to check if it's a method or a field. Issues:
> 1) ASI is not done. Actually not quite sure how to do that, probably I'm
> missing something trivial.
What's ASI? Do you mean AST? If so, you'll need to hook into SyntaxChecker and ASTBuilder. The SyntaxChecker is used when JSC does a quick pass over the source code to ensure no syntax errors. ASTBuilder is used to actually build and AST. We templatize the parser over the type of TreeBuilder. This means that SyntaxChecker and ASTBuilder need to provide the same API. This often means just filling in empty stubs inside SyntaxChecker. To add AST nodes, you'll need to modify parser/Nodes.h. You'll need to add a constructor, methods that you need, etc. Then, you can hook up the ASTBuilder to call into the API you define as needed. You should be able to find other examples of this by reading code inside ASTBuilder and Parser.cpp. You'll probably need to modify class declaration/expr nodes to know about their properties. Then, when generating code for these, you'll need to hook into the byte code generator, inside bytecompiler/BytecodeGenerator.* and bytecompiler/NodesCodeGen.cpp

> 2) I'm just using as-is the code to parse assignments. Probably needs
> tweaking.
It depends what the grammar is. What does the grammar say here?

> 3) I'm not generating any code.
See above.

> My idea for the first patch would be to figure out 1) and 2) and to pass the
> stuff in https://github.com/tc39/test262/pull/1064
> I tried a bunch of examples and they all work, including new ones like class
> { field; method; field; etc }
We'll need 1, 2, and 3 to land this. We need to actually generate and execute code correctly.

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