syntax_data: {"ast_node_type":"other","tokens":[{"end":45,"kind":"keyword","start":0,"text":"Ok(None)"}]}
source_snippet:             Ok(None) => Ok(EvaluatedToAmbig),
context_before:             Ok(Some(c)) => self.evaluate_candidate(stack, &c),
context_after:             Err(SelectionError::Overflow(OverflowError::Canonical)) => {