Cannot use enum from base model for property of external model element

Consider the following three grammars that generate ecore models:

• MyDsl - the base grammar, containing the enum definition
• MyDsl2 - a grammar inheriting from the base, containing a ParentModel with a property using the enum from the base grammar
• MyDsl3 - a grammar inheriting from the base, containing a ChildModel that is a subclass of ParentModel

An error Cannot find compatible feature property in sealed EClass ParentModel from imported package http://www.xtext.org/example/mydsl2/MyDsl2: The existing attribute 'property' has an incompatible type 'Property'. The expected type is 'Property'. prevents using the property from ParentModel in the ChildModel rule.

grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals

generate myDsl "http://www.xtext.org/example/mydsl/MyDsl"

Model:
  greetings+=Greeting*;
	
Greeting:
  'Hello' name=ID '!';

enum Property:
  'ONE;

grammar org.xtext.example.mydsl2.MyDsl2 with org.xtext.example.mydsl.MyDsl

generate myDsl2 "http://www.xtext.org/example/mydsl2/MyDsl2"

ParentModel:
  property=Property;

grammar org.xtext.example.mydsl3.MyDsl3 with org.xtext.example.mydsl.MyDsl

generate myDsl3 "http://www.xtext.org/example/mydsl3/MyDsl3"
import "http://www.xtext.org/example/mydsl2/MyDsl2" as parent

ChildModel:
  ParentProperty;

fragment ParentProperty returns parent::ParentModel:
  property=Property; // Error here.

Note that the fragment rule was used to avoid the Generated package 'myDsl3' may not be empty error and is not necessary to trigger the issue:

ChildModel returns parent::ParentModel:
  property=Property; // Error here as well.

In this case there is no subclass at all, yet the error persists, even if the generate directive was removed from the grammar entirely.

Attached gradle setup reproducing the issue: org.xtext.example.mydsl.parent.zip

Start with the attached Gradle setup and reproduce the error using the MyDsl, MyDsl2, and MyDsl3 grammar examples. Trace grammar inheritance, imported packages, and enum property resolution around the fragment or ChildModel rule. Done means a property using the base grammar's enum is accepted in the external ParentModel scenario without the incompatible-type error.