{"ast_node_type":"other","tokens":[{"end":74,"kind":"keyword","start":0,"text":"ty::Ref(..)"}]}
                ty::Ref(..) => Some("references must be non-null".into()),
                // Primitive types that don't like 0 as a value.
                ty::Adt(..) if ty.is_box() => Some("`Box` must be non-null".into()),