syntax_data: {"ast_node_type":"variable","tokens":[{"end":97,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let Some((tail_field, prefix_fields)) = def.non_enum_variant().fields.raw.split_last() else {
context_before:     // The last field of the structure has to exist and contain type/const parameters.
context_after:         return DenseBitSet::new_empty(num_params);