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Describe the issue

I have the trailing_commas option set to preserve, so I expect any commas I add to remain intact. However, when I try to add a comma to a typedef, regardless of its length, the comma is removed.

To Reproduce

For example, I have the following typedef: when I add a comma after url, it gets removed.

typedef RawPhoto = ({DateTime addedAt, String name, String url});

Expected behavior

I expect that when using the trailing_commas option set to preserve, no commas should be removed.