"async" keyword in arrow notation is incorrect

[sumanthratna]

Suppose I have the function:

void fetchActive() async =>
      _myPrivateVar = await API.fetchPrivateVar();

The async keyword is highlighted in blue as if it is a function name. However, when using:

void fetchActive() async {
      _myPrivateVar = await API.fetchPrivateVar();
}

The async keyword is highlighted correctly in purple. Interestingly, the same issue occurs in GitHub's markdown, so perhaps I'm missing something?

Note: I am using Flutter, but I don't think it should make a difference.

EDIT: making a change to this regex might fix things.