In the DSL, the == operation currently does not work for references to dataclasses. This is a non-trivial problem, because dataclasses are entities, which behave very differently in the DSL from primitives: "equal" instances are contracted by index (dataclasses currently do not support indexes), but two references with different parameters might still result in the same dataclass. So equality can be proven, but not disproven, which may lead to unknown relation sizes / arity.