syntax_data: {"ast_node_type":"other","tokens":[{"end":86,"kind":"keyword","start":0,"text":"Err(NotConstEvaluatable::MentionsParam)"}]}
source_snippet:                         Err(NotConstEvaluatable::MentionsParam) => Ok(EvaluatedToErr),
context_before:                         Err(NotConstEvaluatable::MentionsInfer) => Ok(EvaluatedToAmbig),
context_after:                         Err(_) => Ok(EvaluatedToErr),