So the latest change involves recording in ExpressionClassifier whether a
CoverInitializedName occurs, which makes the ExpressionClassifier at least 8
bytes bigger, and likely slows down parsing a tiny bit.
The reason for this, compared to the strategy in ObjectLiteralChecker, is so
that the parser can handle expressions like `({ bar: this.y, z: { foo } } =
someObject)` --- previously it was only treated as a pattern if followed by
Token::ASSIGN, which would break nested Object* patterns. So, it's now
possible
to use the classifier to store the CoverInitializedName state from nested
properties.
It might be an expensive approach for the corner case, but I don't have a
better
idea right now.
---
There are also some slightly messy things tracking whether or not you are
potentially parsing arrow function formal parameters (which is used to defer
reporting of expression errors if Token::ARROW shows up), and tracking if
parsing a property or element or not, so that it's possible to distinguish
whether parsing the top-level literal / pattern or not. This enables
deferring
reporting the CoverInitializedName error for expressions until it's known
for
sure that an expression is being parsed or not.
These flags are small bits of parser state, but the RAII-style trackers for
them
add a bit of code (and, these things could be refactored to share as much as
possible via macros or templates, so that the diff is a bit tinier, not
sure if
it's preferred or if it would be better to just manually track these, or if
people think tracking these is pointless)
---
Finally, figuring out the error story seems pretty important, I'm not sure
it's
possible to merge both pattern errors, but it would be nice to make the
classifier smaller.
If anyone has some ideas on how to clean this up, so that less stack space
is
used, that would be awesome.
https://codereview.chromium.org/1309813007/
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