[sklogic]

> because PEG parsers don't really support that kind of consistency-checking

Not true at all. You can easily check if a new parser is breaking anything in the old one.

And in practice you never mix languages at the same level. A more typical example of such a mixing would be, say, regexp syntax in javascript.

EDIT: if you want more details on a theory of this static PEG verification, they will be available some time later when I polish my next bunch of commits.