Parenthesized destructuring assignment should error

Was working with @hzoo on trying to get babel-eslint’s tests running with the ESLint test suite and came across this in our test suite. This passes in ESLint using Espree, but Babylon (babel-eslint’s parser) throws with the following error:

You’re trying to assign to a parenthesized expression, eg. instead of ({a}) = 0 use ({a} = 0)

I did a little digging, and it does seem like this shouldn’t be parsed by Espree. Some findings that back this up:

• https://github.com/babel/babel/pull/3260
• http://whereswalden.com/2015/06/20/new-changes-to-make-spidermonkeys-and-firefoxs-parsing-of-destructuring-patterns-more-spec-compliant/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1146136

I also tested in Chrome:

and Firefox:

If this is accepted I’ll also file an issue for Espree (and probably ultimately Acorn as well), but I wanted to have an issue open here so we could discuss and track this issue as well as fix the tests if and when this gets fixed in the parser.

[kaicataldo]

Issue filed with Acorn: https://github.com/ternjs/acorn/issues/429

[not-an-aardvark]

Closing because this was fixed in acorn@4.0.5.