The recent fixes ensured that the on_assign_error callback was issued, but MRI fails the whole parse in this case.

I'm not sure why this was introduced, as I don't think this was ever a thing for anything beyond w/W/i/I, and those have explicit whitespace removal in their respective cases.

So that Ripper can also benefit from it.

The parser correctly identified that no interpolation should happen, but failed to include the hash symbol in the result.

For both the main Ruby parser and Ripper

The logic makes more sense to me, and seems to work better with the cryptic test cases this introduces.

Miscellaneous parsing fixes