Fix return type value checking for BuiltinFunctionEmbedder

Actually, in the case of single returned value (non-tuple), the constness of data type in shared_ptr's was not checked at compile time.

src/language/modules/SchemeModule.cpp

@@ -33,7 +33,6 @@
 #include <scheme/FourierBoundaryConditionDescriptor.hpp>
 #include <scheme/FreeBoundaryConditionDescriptor.hpp>
 #include <scheme/IBoundaryConditionDescriptor.hpp>
-#include <scheme/IDiscreteFunction.hpp>
 #include <scheme/IDiscreteFunctionDescriptor.hpp>
 #include <scheme/NeumannBoundaryConditionDescriptor.hpp>
 #include <scheme/SymmetryBoundaryConditionDescriptor.hpp>
@@ -44,8 +43,6 @@
 SchemeModule::SchemeModule()
 {
   this->_addTypeDescriptor(ast_node_data_type_from<std::shared_ptr<const DiscreteFunctionVariant>>);
-#warning remove after reworked
-  this->_addTypeDescriptor(ast_node_data_type_from<std::shared_ptr<const IDiscreteFunction>>);
   this->_addTypeDescriptor(ast_node_data_type_from<std::shared_ptr<const IDiscreteFunctionDescriptor>>);
   this->_addTypeDescriptor(ast_node_data_type_from<std::shared_ptr<const IQuadratureDescriptor>>);