Reuse _parsed

[kurkle]

The "what if" part from #6750 (review)

[benmccann]

I'm okay with leaving _parsed under meta.data, but think it would be clearer if we initialized _parsed to undefined and the parsing functions returned new objects instead of setting values in previously created objects

[kurkle]

@benmccann you're right, it is better to have it undefined to start with, so premature access shows up more easily.

[kurkle]

Closed in favor of #6758