ProposalProvider fails due to FollowElementComputer.computeFollowElements misbehaviour

In some very specific and strange circumstances (see tests below), the content assist does not work anymore.
While debugging, I found that in the method ContentAssistContextFactory.doCreateContexts( INode, INode, String, EObject, Collection), the call to FollowElementComputer.computeFollowElements 'returns' an empty list of AbstractElement, preventing any possible proposal provider context to be created.

In attachment, a complete example to reproduce the problem, with ui.tests for the identified proposal provider fail case.

Example of working and not working case:
`package my.package

class Test {

// Does not work
for (var i = 1; i < 10; i++) { 
	A intProperty:10 {	}
	B enumProperty: // <-- content assist (fails) here
	literal1 {}
}
			
// Works !!!
for (var i = 1; i < 10; i++) { 
	//A intProperty:10 {	}
	B enumProperty: // <-- content assist (works) here
	literal1 {}
}

}`
demo.zip

Start with the demo.zip reproduction and its ui.tests for the failing proposal-provider case. Trace ContentAssistContextFactory.doCreateContexts(...) and the call to FollowElementComputer.computeFollowElements, comparing the cases where content assist fails and works. Done means the failing case creates proposal-provider context and content assist works without regressing the working case.