syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"span_interner:"}]}
source_snippet:             span_interner: Lock::new(span_encoding::SpanInterner::default()),
context_before:             symbol_interner: symbol::Interner::with_extra_symbols(extra_symbols),
context_after:             metavar_spans: Default::default(),