syntax_data: {"ast_node_type":"other","tokens":[{"end":112,"kind":"keyword","start":0,"text":"Box::new(AggregateKind::Adt(adt_def.did(),"}]}
source_snippet:                     Box::new(AggregateKind::Adt(adt_def.did(), *variant_index, args, None, active_field_index)),
context_before:                 Ok(Rvalue::Aggregate(
context_after:                     fields.iter().map(|f| self.parse_operand(f.expr)).collect::<Result<_, _>>()?