syntax_data: {"ast_node_type":"other","tokens":[{"end":44,"kind":"keyword","start":0,"text":"assert_eq!(variant.fields.len(),"}]}
source_snippet:         assert_eq!(variant.fields.len(), 1);
context_before:         let variant = def.non_enum_variant();
context_after:         let field_ty = variant.fields[FieldIdx::ZERO].ty(tcx, args);