Sanity check look ahead contexts
Sanity check look ahead contexts

If we don't actually switch here it's possible to get stuck in an
infinite loop.

janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting,janusw/syntax-highlighting