syntax_data: {"ast_node_type":"function","tokens":[{"end":48,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn eval_unevaluated_mir_constant_to_valtree(
context_before:     /// Based on `FunctionCx::eval_unevaluated_mir_constant_to_valtree`.
context_after:         &self,