unblock voxel schema loading, add test for express

src/ifcopenshell-python/ifcopenshell/express/schema_class.py

@@ -420,7 +420,13 @@ class SchemaClass(codegen.Base):
 
             if isinstance(type, nodes.AggregationType):
                 aggr_type = type.aggregate_type
-                make_bound = lambda b: -1 if b == "?" else int(b)
+                def make_bound(b):
+                    # `?` and non-literal bounds (attribute references, arithmetic expressions) collapse to -1.
+                    # 
+                    try:
+                        return int(b)
+                    except (TypeError, ValueError):
+                        return -1
                 bound1, bound2 = map(make_bound, (type.bounds.lower, type.bounds.upper))
                 decl_type = get_declared_type(type.type, emitted_names)
                 return x.aggregation_type(aggr_type, bound1, bound2, decl_type)
@@ -547,7 +553,14 @@ class SchemaClass(codegen.Base):
                 inv_attrs = []
                 for attr in type.inverse:
                     if attr.bounds:
-                        make_bound = lambda b: -1 if b == "?" else int(b)
+                        def make_bound(b):
+                            # `?` and non-literal bounds (attribute references, arithmetic
+                            # expressions) collapse to -1 (unbounded) — the C++ runtime has
+                            # no third state for "dynamic cardinality".
+                            try:
+                                return int(b)
+                            except (TypeError, ValueError):
+                                return -1
                         bound1, bound2 = map(make_bound, (attr.bounds.lower, attr.bounds.upper))
                     else:
                         bound1, bound2 = -1, -1