syntax_data: {"ast_node_type":"other","tokens":[{"end":84,"kind":"keyword","start":0,"text":"match_pairs:"}]}
source_snippet:         match_pairs: &mut Vec<Self>, // Newly-created nodes are added to this vector
context_before:         cx: &mut Builder<'_, 'tcx>,
context_after:         extra_data: &mut PatternExtraData<'tcx>, // Bindings/ascriptions are added here