345736 - "for each" and "let[x,y]" in array comprehensions

Status: VERIFIED FIXED

(Core :: JavaScript Engine, enhancement)

Description

[David Finch]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1b1) Gecko/20060724 BonEcho/2.0b1
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1b1) Gecko/20060724 BonEcho/2.0b1

Suppose you execute the following in Firefox 2.0:
arr=[x+x for (x in ["a","b","c"])];

Now arr contains ["00","11","22"]

Wanting to get a result like ["aa","bb","cc"], I try both of the following:
arr=[x+x for each (x in ["a","b","c"])];
arr=[x+x for (let [,x] in ["a","b","c"])];

But neither syntax is valid in array comprehensions, even though both are supported in for() loops. Supporting either of those would make JS 1.7's array comprehension support more python-like.

Reproducible: Always

Comment 1

[Brendan Eich [:brendan]]

The destructuring assignment in comprehensions work is being tracked in bug 336379, but I'll take this one and make it depend on the js1.7 metabug.

/be

Comment 2

[Brendan Eich [:brendan]]

Small patch (diff -w coming), needed for js1.7.

/be

Comment 3

[Brendan Eich [:brendan]]

Attachment: fix

diff -w version next.

/be

Comment 4

[Brendan Eich [:brendan]]

Attachment: diff -w version of last attachment

Comment 5

[Brendan Eich [:brendan]]

Fixed on trunk.

/be

Comment 6

[Mike Schroepfer]

Comment on attachment 232025 [details] [diff] [review]
fix

a=schrep for drivers.

Comment 7

[Brendan Eich [:brendan]]

Fixed on the 1.8 branch too.

/be

Comment 8

[Bob Clary [:bc] (inactive)]

Checking in regress-345736.js;
/cvsroot/mozilla/js/tests/js1_7/geniter/regress-345736.js,v  <--  regress-345736.js
initial revision: 1.1

tests for 
[x+x for (x in ["a","b","c"])];
[x+x for each (x in ["a","b","c"])];

Comment 9

[Bob Clary [:bc] (inactive)]

verified fixed 1.8, 1.9 win/mac(ppc|tel)/linux 20060808

Comment 10

[Jesse Ruderman]

There should be regression tests for the destructuring-like form, too.

js> arr=[x+x for ([,x] in ["a","b","c"])];
aa,bb,cc

js> arr=[x+y for ([x,y] in ["a","b","c"])]; 
0a,1b,2c

Comment 11

[Bob Clary [:bc] (inactive)]

/cvsroot/mozilla/js/tests/js1_7/geniter/regress-345736.js,v  <--  regress-345736.js
new revision: 1.2; previous revision: 1.1
done