weird edge case for arrow functions

[asafigan]

I get this error even on the website for babel. (https://babeljs.io/repl/)

these pieces of code work:
const works = ({async}) => {return true}
const alsoWorks = (async=true) => {return true}
const worksAsWell = ([async=true]) => {return true}

but this code doesn't work:
const fails = ({async=true}) => {return true}

even though it works with a function:
const workingFunction = function ({async=true}) {return true}

and any other argument name works:
const differentArgumentName = ({different=true}) => {return true}

So it looks like the error is coming from using the name async with a default value on a deconstructed object in an arrow function's arguments.

Here is a link to an example

[Nolski]

Isn't async a reserved keyword? I don't think this should be expected to work.

[asafigan]

but it works on all the snippets but one. If it shouldn't be used, than none of them should work not just one. Also you can declare variable with the name async.

[danez]

Async is not a reserved word it seems at least I can't see it in the spec, seems our parser is misbehaving here.
http://www.ecma-international.org/ecma-262/6.0/#sec-keywords

[danharper]

Closing in favour of this in Babylon: babel/babylon#118.