syntax_data: {"ast_node_type":"other","tokens":[{"end":71,"kind":"keyword","start":0,"text":"Some(&mut"}]}
source_snippet:                     Some(&mut (ref mut last_range, ref mut last_state))
context_before:                     // Merge contiguous runs with a common destination.
context_after:                         if last_range.end == range.start && *last_state == state =>