code: protected FunctionTypeReference getAsProcedureOrNull(ParameterizedTypeReference typeReference) {
  		ITypeReferenceOwner owner = typeReference.getOwner();
  		JvmType type = typeReference.getType();
  		FunctionTypeReference functionType = new FunctionTypeReference(owner, type);
  		if (!tryAssignTypeArguments(typeReference.getTypeArguments(), functionType))
  			return null;
  		JvmType voidType = (JvmType) owner.getContextResourceSet().getEObject(URIHelperConstants.PRIMITIVES_URI.appendFragment("void"), true);
  		functionType.setReturnType(owner.newParameterizedTypeReference(voidType));
  		return functionType;
  	}
docs: /* @Nullable