646807 - Remove extra RHS checking in CheckDestructuring

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jason Orendorff [:jorendorff]]

In jsparse.cpp, CheckDestructuring raises an error if the destructuring shorthand {p1, p2} appears to the right of =.

That check is insufficient, since there are all sorts of other places where it might erroneously occur-- basically anywhere an expression is used as an rvalue. So js_EmitTree also checks, in the TOK_RC case.

The latter check seems to cover all the cases. CheckDestructuring doesn't need to check, and the code is shorter without it.

Comment 1

[Jason Orendorff [:jorendorff]]

Attachment: v1

Also updated to idiomatic C++.

-25 lines net.

(More where this came from, if I can ever get my def-use chains straight.)

Comment 2

[Jason Orendorff [:jorendorff]]

Attachment: v2

v1 left the declaration of fpvd even though it was unused. Deleting that leads to more simplifications, so it's a total of -40 lines.

Comment 3

[Brendan Eich [:brendan]]

Comment on attachment 523296 [details] [diff] [review]
v2

Nice.

FYI, there is a Harmony proposal to support {p1, p2} for constructing an object with properties of those names, whose initial values come from the result of evaluating those lexical refs.

/be

Comment 4

[Jason Orendorff [:jorendorff]]

http://hg.mozilla.org/tracemonkey/rev/87fc73e2264f

Comment 5

[Chris Leary [:cdleary] (not checking bugmail)]

http://hg.mozilla.org/mozilla-central/rev/87fc73e2264f