syntax_data: {"ast_node_type":"other","tokens":[{"end":79,"kind":"keyword","start":0,"text":"Ok(ImplSource::Builtin(BuiltinImplSource::TraitUpcasting(idx),"}]}
source_snippet:         Ok(ImplSource::Builtin(BuiltinImplSource::TraitUpcasting(idx), nested))
context_after:     }