syntax_data: {"ast_node_type":"function","tokens":[{"end":57,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn next_discr(&mut self, value: u128) -> VariantIdx {
context_before:     // corresponding variant in linear time.
context_after:         // An out-of-bounds abort will occur if the discriminant ordering isn't as described above.