{"ast_node_type":"other","tokens":[{"end":93,"kind":"keyword","start":0,"text":"assert_eq!(v.layout().fields.count(),"}]}
                assert_eq!(v.layout().fields.count(), 2, "`Box` must have exactly 2 fields");
                // `Box` has two fields: the pointer we care about, and the allocator.
                let [unique_ptr, alloc] =