1157419 - Elision following AssignmentRestElement should not be permitted

Status: RESOLVED DUPLICATE of bug 1041341

(Core :: JavaScript Engine, defect)

Description

[Mike Pennisi [:jugglinmike]]

$ js -e "[...x , ] = [1, 2, 3];"

Expected: SyntaxError
Actual: successful execution (an new array, `[1, 2, 3]` is assigned to `x`)

Additional elisions are incorrectly rejected, i.e.

    $ js -e "[...x , , ] = [1,2,3]; print(x);"
    -e:1:8 SyntaxError: parameter after rest parameter:
    -e:1:8 [...x , , ] = [1,2,3]; print(x);
    -e:1:8 ........^

Relevant grammar (ES6 12.14.5 Destructuring Assignment):

> ArrayAssignmentPattern[Yield] :
>   [ Elisionopt AssignmentRestElement[?Yield]opt ]
>   [ AssignmentElementList[?Yield] ]
>   [ AssignmentElementList[?Yield] , Elisionopt AssignmentRestElement[?Yield]opt ]
> 
> AssignmentRestElement[Yield] :
>   ... DestructuringAssignmentTarget[?Yield]
> 
> DestructuringAssignmentTarget[Yield] :
>   LeftHandSideExpression[?Yield]

Source: https://people.mozilla.org/~jorendorff/es6-draft.html#sec-destructuring-assignment

Build details:

commit 07bb578e6a93d11a3e1365e2b0d9296a755543ee
Date:   Fri Apr 17 13:52:50 2015 -0700

Comment 1

[Mike Pennisi [:jugglinmike]]

Updating to confirm that this is still an issue with the latest build:

    $ js -e "[...x , ] = [1]; print(x);"
    1
    $ js -e "[...x , , ] = [1]; print(x);"
    -e:1:8 SyntaxError: parameter after rest parameter:
    -e:1:8 [...x , , ] = [1]; print(x);
    -e:1:8 ........^

commit 09631fba2e955162f3ffbbdc4f4a5c8b9c926ead
Date   Mon May 18 13:43:01 2015 +0200

Comment 2

[Arpad Borsos [:Swatinem]]

This is basically a dupe of bug 1041341.