Should we allow to open enumerations?

[echebbi]

Context

Currently ALE doesn't support to open enumerations. More specifically, it assumes that only EClass are open and doesn't consider the case where one attempts to open an EEnum:

ale-lang/plugins/org.eclipse.emf.ecoretools.ale.core/src/org/eclipse/emf/ecoretools/ale/core/parser/internal/AntlrAstToAleBehaviorsFactory.java

Lines 410 to 413 in 1d62a14

	ExtendedClass cls = implemFactory.createExtendedClass();
	EClassifier resolvedType = resolve(baseCls);
	if(resolvedType instanceof EClass)
	cls.setBaseClass((EClass)resolvedType);

This leads to multiple errors in validators and in the interpreters when we access extendedClass.getBaseClass() without checking whether the base class actually exists.

Workaround

For now I'm going to add guards to prevent being bloated by this kind of error but we need to think about it.