syntax_data: {"ast_node_type":"other","tokens":[{"end":90,"kind":"keyword","start":0,"text":"&mut"}]}
source_snippet:             &mut |candidate: Candidate<'_>, parent_data: &mut Vec<PatternExtraData<'_>>| {
context_before:             &mut Vec::new(),
context_after:                 sub_branches.push(MatchTreeSubBranch::from_sub_candidate(candidate, parent_data));