351336 - Loss of parens in "for" initial-expression using "in" operator causes syntax error

Status: VERIFIED FIXED

(Core :: JavaScript Engine, defect, P2)

Description

[Jesse Ruderman]

> function () { for (("p" in a); 0;) { } }
function () { for ("p" in a; 0;) { } }

> function () { for ("p" in a; 0;) { } }
SyntaxError on line 1: invalid for/in left-hand side

This could be fixed by:

(1) Keeping the parens intact during decompilation (see also bug 351104, a round-trip change that involves loss of parens in a "for" initial-expression)

(2) Allowing the second line to compile, by not treating the "in" as an attempt to create a for-in loop if there's a semicolon present.

Comment 1

[Brendan Eich [:brendan]]

(In reply to comment #0)
> > function () { for (("p" in a); 0;) { } }
> function () { for ("p" in a; 0;) { } }
> 
> > function () { for ("p" in a; 0;) { } }
> SyntaxError on line 1: invalid for/in left-hand side
> 
> This could be fixed by:
> 
> (1) Keeping the parens intact during decompilation (see also bug 351104, a
> round-trip change that involves loss of parens in a "for" initial-expression)
> 
> (2) Allowing the second line to compile, by not treating the "in" as an attempt
> to create a for-in loop if there's a semicolon present.

(1) is the only way, as (2) requires either unbounded lookahead for a top-down parser, or a bottom-up parser, and requiring either of those implementations is neither desirable nor conformant with ECMA-262.

/be

Comment 2

[Brendan Eich [:brendan]]

Attachment: fix

Simple patch (this is against the 1.8 branch; trunk patch is the same unless the patch for bug 350531 gets review soon -- hint hint ;-).

/be

Comment 3

[Brendan Eich [:brendan]]

Fixed on trunk.

/be

Comment 4

[Mike Schroepfer]

Comment on attachment 236739 [details] [diff] [review]
fix

a=schrep for drivers.

Comment 5

[Brendan Eich [:brendan]]

Fixed on the 1.8 branch.

/be

Comment 6

[Bob Clary [:bc] (inactive)]

Checking in regress-351336.js;
/cvsroot/mozilla/js/tests/js1_5/Regress/regress-351336.js,v  <--  regress-351336.js
initial revision: 1.1

Comment 7

[Bob Clary [:bc] (inactive)]

verified fixed 1.8, 1.9 20060906 windows/mac*/linux