Arrow function single argument without parenthesis

[KSXGitHub]

    var arrow = args => 1234; // not works
    var arrow = (args) => 1234; // works

I wish that, in the first line, arrow is marked as a function and args is marked as a parameter.

[MaximSokolov]

Duplicate of #193

[winstliu]

Thanks @MaximSokolov!