Fix missing inner comments in function expressions

[overlookmotel]

Same as #13824 but for function expressions.

Q	A
Fixed Issues?	n/a
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR Link	n/a
Any Dependency Changes?	No
License	MIT

Similar to #13819, function expressions with inner comments do not have the comments output by generate(). This PR fixes that.

For async functions, there's some ambiguity as to where the comment should be output i.e.:

x = async /*foo*/ function () {};

or:

x = async function /*foo*/ () {};

I have gone for the latter as for single line comments, putting the comment after async is invalid JS. This is not valid:

x = async // foo
function() {};

whereas this is:

x = async function // foo
() {};

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[JLHwung]

Can you add a new test case?

const j = function (/*foo*/) {};

it will be printed as

const j = function /*foo*/ () {};

I think we don't have to fix that. It is the nature of using AST for comment attachment targets.

[overlookmotel]

Have pushed another commit adding this case.

I also added cases for other positions of comments in async + generator functions.

const x = async /*foo*/ function () {};
const y = function/*foo*/* () {};

Similarly, these don't come out quite the same as the input, but at least the comment isn't omitted entirely now.

[nicolo-ribaudo]

The CI failures seem to be caused by the npm outage.

[overlookmotel]

Thanks all!