Xtext: Wildcard generic types via JvmModelInferrer

Question

I have to implement an external interface with a class generated from my DSL. One of the methods to implement has the following signature:

public void execute(SomeType<? extends OtherType> param1, ...) {...}

In the JvmModelInferrer, I mapped the appropriate elements of the DSL onto a method and added the parameters like this:

parameters += appRule.toParameter("param1", appRule.newTypeRef(SomeType, it.newTypeRef("? extends OtherType")))

It almost works, but generates a very strange output:

public void execute(final /*SomeType<? extends OtherType> */Object param1, ...) {...}

I suppose there could be additional settings to force the generator use the generic parameter I provided, but can't really find it.

Answer 1

Basically, you should set up the type parameters in the model instead of creating it in a string. For that, we use the following construct in EMF-IncQuery:

it.parameters += pattern.toParameter("processor", 
      pattern.newTypeRef(typeof (IMatchProcessor),
                         cloneWithProxies(matchClassReference).wildCardSuper))

Here, cloneWithProxies is provided by the JvmTypesBuilder (can be injected), while wildCardSuper is a helper method written by us:

public JvmWildcardTypeReference wildCardSuper(JvmTypeReference clone) {
        JvmWildcardTypeReference result = factory.createJvmWildcardTypeReference();
        JvmLowerBound lowerBound = factory.createJvmLowerBound();
        lowerBound.setTypeReference(clone);
        result.getConstraints().add(lowerBound);
        return result;
}