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

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

Model:
	entities+=Entity*;
	
Entity:
	abstract?='abstract'? name=ID 
		('extends' parent=EntityRef)? 
		('owner' owner=EntityRef)? '{'
		/* attributes, etc. */
	'}';
	
EntityRef:
	target=[Entity] (alias=ID)?;

class MyDslScopeProvider extends AbstractMyDslScopeProvider {

	@Inject extension ResourceExtension

	override getScope(EObject context, EReference reference) {
		if (reference == MyDslPackage.Literals.ENTITY_REF__TARGET) {
			if (true) /* FIXME isScopeFor"Parent"()? */ {
				context.eContainer.scopeAbstractEntities(reference)
			} else if (true) /* FIXME isScopeFor"Owner"()? */ {
				context.eContainer.scopeNonAbstractEntities(reference)
			}
		} else {
			super.getScope(context, reference)
		}
	}

	def dispatch scopeAbstractEntities(EObject it, EReference ref) {
		println('''[ERR] not supported''')
		super.getScope(it, ref)
	}

	def dispatch scopeAbstractEntities(Entity it, EReference ref) {
		Scopes.scopeFor(eResource.findAllEntities.filter[isAbstract])
	}

	def dispatch scopeNonAbstractEntities(EObject it, EReference ref) {
		println('''[ERR] not supported''')
		super.getScope(it, ref)
	}

	def dispatch scopeNonAbstractEntities(Entity it, EReference ref) {
		Scopes.scopeFor(eResource.findAllEntities.filter[!isAbstract])
	}
}

Entity:
	abstract?='abstract'? name=ID
	(parent=EntityRefParent)?
	(owner=EntityRefOwer)? '{'
	/* attributes, etc. */
	'}';

EntityRefParent:
	{EntityRef} 'extends' target=[Entity] (alias=ID)?;

EntityRefOwer:
	{EntityRef} 'owner' target=[Entity] (alias=ID)?;	

Model:
	entities+=Entity*;

Entity:
	abstract?='abstract'? name=ID
		parent=ParentEntityRef?
		owner=OwnerEntityRef?
	'{'
		/* attributes, etc. */
	'}';

ParentEntityRef:
	{EntityRef} 'extends' target=[Entity] (alias=ID)?;

OwnerEntityRef:
	{EntityRef} 'owner' target=[Entity] (alias=ID)?;

package org.xtext.example.mydsl.scoping

import org.eclipse.emf.ecore.EObject
import org.eclipse.emf.ecore.EReference

import static org.xtext.example.mydsl.myDsl.MyDslPackage.Literals.*

class MyDslScopeProvider extends AbstractMyDslScopeProvider {
	override getScope(EObject it, EReference ref) {
		switch (ref) {
			case ENTITY_REF__TARGET: {
				switch (eContainingFeature) {
					case ENTITY__OWNER: {
						// ... works fine
					}
					case ENTITY__PARENT: {
						// ... works fine
					}
					default: {
						// not supported
					}
				}
			}
			default: {
				super.getScope(it, ref)
			}
		}
	}
}