Function validate_spec_interfaces 

pub fn validate_spec_interfaces(
    referenced_rules: &HashMap<Vec<String>, HashSet<String>>,
    spec_ref_facts: &[(FactPath, Arc<LemmaSpec>, Source)],
    rule_entries: &IndexMap<RulePath, RuleEntryForBindingCheck>,
    main_spec: &Arc<LemmaSpec>,
) -> Result<(), Vec<Error>>

Validate that every spec-ref fact path’s referenced spec has the required rules and that each such rule’s result type satisfies what the referencing rules expect.