syntax_data: {"ast_node_type":"other","tokens":[{"end":48,"kind":"keyword","start":0,"text":"r:"}]}
source_snippet:         r: <Self::Interner as Interner>::Region,
context_before:         ty: <Self::Interner as Interner>::Ty,
context_after:         span: <Self::Interner as Interner>::Span,