Parser logic updated now. At first I thought going with this approach had broken the tests but turned out the tests were wrong, and this new approach leads to the correct result.

When I wrote the tests for this back in Febuary there were not implementations to try, and babel did not get the parsing right (they have now addressed these issues). So I unfortunately developed the wrong intuition for how this syntax should parse when nested within other expressions.

Did spot an issue in V8 when trying to compare to what they do: [URL]