Bonsai: refuse class-mismatched type assignment

Schema-illegal IfcDoor->IfcWallType pairings parse cleanly but propagate
into operators that fan out by type and eventually crash the wrapper.
Block the pairing at its source: API guard in ifcopenshell.api.type.
assign_type, per-object partition in BIM_OT_assign_type + DuplicateType,
new tool.Type.is_relating_type_compatible helper, AST forward-compat
guard. Files in the wild are still loaded unchanged.

Generated with the assistance of an AI coding tool.

src/ifcopenshell-python/ifcopenshell/api/type/assign_type.py

@@ -24,6 +24,7 @@ import ifcopenshell.api.owner
 import ifcopenshell.api.type
 import ifcopenshell.guid
 import ifcopenshell.util.element
+import ifcopenshell.util.type
 
 
 def assign_type(
@@ -189,6 +190,20 @@ class Usecase:
         if not related_objects:
             return
 
+        # The EXPRESS schema has no WHERE rule pairing RelatingType /
+        # RelatedObjects classes; the canonical class pairing per schema
+        # is a buildingSMART implementer agreement, enforced here.
+        allowed_occurrences = ifcopenshell.util.type.get_applicable_entities(
+            relating_type.is_a(), schema=self.file.schema
+        )
+        mismatched_classes = sorted({o.is_a() for o in related_objects if o.is_a() not in allowed_occurrences})
+        if mismatched_classes:
+            raise TypeError(
+                f"{relating_type.is_a()} cannot type {', '.join(mismatched_classes)} "
+                f"in schema {self.file.schema} (allowed occurrence classes: "
+                f"{allowed_occurrences or '<none>'})"
+            )
+
         ifc2x3 = self.file.schema == "IFC2X3"
         related_objects_set = set(related_objects)
         if ifc2x3: