syntax_data: {"ast_node_type":"other","tokens":[{"end":31,"kind":"keyword","start":0,"text":"match_start_span:"}]}
source_snippet:         match_start_span: Span,
context_before:         scrutinee_place_builder: &PlaceBuilder<'tcx>,
context_after:         patterns: Vec<(&Pat<'tcx>, HasMatchGuard)>,