fixed empty sets/relations not working if they dont have a type

btypes_primitives/src/main/rust/btypes/src/bobject.rs

 use std::hash::Hash;
 use std::clone::Clone;
-use std::fmt::Display;
+use std::fmt;
 use crate::bboolean::{BBoolean, BBooleanT};
 
-pub trait BObject: Eq + Hash + Ord + Clone + Display {
+pub trait BObject: Eq + Hash + Ord + Clone + fmt::Display {
     fn is_struct(&self) -> BBoolean { BBoolean::new(false) }
 }
+
+#[derive(Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct Dummy {}
+impl fmt::Display for Dummy {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "None") }
+}
+
+impl BObject for Dummy {}

src/main/resources/de/hhu/stups/codegenerator/RustTemplate.stg

@@ -19,6 +19,7 @@ use std::time::{Duration};
 use std::fmt;
 use rand::{thread_rng, Rng};
 use btypes::butils;
+use btypes::bobject;
 use btypes::bboolean::{IntoBool, BBooleanT};
 <imports; separator="\n">
 <includedMachines; separator="\n">
@@ -406,7 +407,7 @@ if_expression_predicate(predicate, ifThen, ifElse) ::= <<
 >>
 
 set_enumeration(leftType, type, rightType, enums, isRelation) ::= <<
-<if(isRelation)>BRelation::new<else>BSet::new<endif>(vec![<enums; separator=", ">])
+<if(isRelation)>BRelation<if(!type)>::\<bobject::Dummy, bobject::Dummy><endif><else>BSet<if(!type)>::\<bobject::Dummy><endif><endif>::new(vec![<enums; separator=", ">])
 >>
 
 seq_enumeration(type, elements) ::= <<