Doesn't play nice with for...of

[ben-eb]

Hello,

I have a bit of a problem using UglifyJS2 with for...of statements; I'm using the new Web MIDI APIs which currently only work with this type of iterator. The relevant code is this:

navigator.requestMIDIAccess().then(function(midiAccess) {
    for (var input of midiAccess.inputs.values()) {
        console.log(input.name);
    }
}, function() { console.log('MIDI unavailable') });

To recreate the problem, just put that in a file and try to parse:

var uglify = require('uglify-js');

var mangled = uglify.minify('problem.js');
console.log('mangled', mangled);

Yields:

/Users/bbriggs/projects/UglifyJS2/lib/parse.js:197
    throw new JS_Parse_Error(message, line, col, pos);
          ^
Error
    at new JS_Parse_Error (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:189:18)
    at js_error (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:197:11)
    at croak (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:657:9)
    at token_error (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:665:9)
    at expect_token (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:678:9)
    at expect (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:681:36)
    at regular_for (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:905:9)
    at for_ (/Users/bbriggs/projects/UglifyJS2/lib/parse.js:901:16)
    at /Users/bbriggs/projects/UglifyJS2/lib/parse.js:783:24
    at /Users/bbriggs/projects/UglifyJS2/lib/parse.js:704:24

API docs: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/for...of
Somewhat related to: browserify/browserify#1008

Thanks. 😃

[rvanvelzen]

See #448 for Harmony/ES6 support.