syntax_data: {"ast_node_type":"other","tokens":[{"end":49,"kind":"keyword","start":0,"text":"span:"}]}
source_snippet:         span: <Self::Interner as Interner>::Span,
context_before:         hidden_ty: <Self::Interner as Interner>::Ty,
context_after:     ) -> Option<<Self::Interner as Interner>::Ty>;