Arrow functions with a single param as default arguments to functions

[ghost]

// incorrect highlighting - arrow isn't highlighted
function f (a = _ => _) { }
function f (a = arg => arg) { }
function f (a = ret => ret) { }
function f (a = pchaigno => pchaigno) { }

// correct highlighting - arrow is highlighted
function f (a = (_) => _) { }
function f (a = (arg) => arg) { }
function f (a = (ret) => ret) { }
function f (a = (pchaigno) => pchaigno) { }

[pchaigno]

@bucaran Is it only _ that is authorized here or could it be function f (a = arg1 => _) { }? Do you know where I could find specifications on this?

[ghost]

It could be anything, it's just the argument name. I updated the example. @pchaigno

[winstliu]

I looked into this a while ago and found that it was because the arrow regex matcher currently mandates an opening and closing parentheses before it'll match =>. I couldn't get it to work properly without parentheses, but I can try again :).

[pchaigno]

Is this valid too?

function f(a = x, y => x + y) {}

[ghost]

It's not.

The following is:

function f(a = x, y = () => {}) {

}

[pchaigno]

Ouch! That's going to be a tricky one...