[staggered] Use tag dispatch instead of Dune::Hybrid::ifElse

Unfortunately clang seems to compile the else branch even if the compile time
condition is true. From the Dune documentation it didn't come clear to me how to
fix this for more elaborate functions.

dumux/freeflow/navierstokes/staggered/localresidual.hh

@@ -111,27 +111,8 @@ public:
         CellCenterPrimaryVariables flux = fluxVars.computeFluxForCellCenter(problem, element, fvGeometry, elemVolVars,
                                                  elemFaceVars, scvf, elemFluxVarsCache[scvf]);
 
-        // add energy fluxes for non-isothermal models
-        Dune::Hybrid::ifElse(std::integral_constant<bool, GET_PROP_VALUE(TypeTag, EnableEnergyBalance) >(),
-        [&](auto IF)
-        {
-            // if we are on an inflow/outflow boundary, use the volVars of the element itself
-            // TODO: catch neumann and outflow in localResidual's evalBoundary_()
-            bool isOutflow = false;
-            if(scvf.boundary())
-            {
-                const auto bcTypes = problem.boundaryTypesAtPos(scvf.center());
-                    if(bcTypes.isOutflow(Indices::energyBalanceIdx))
-                        isOutflow = true;
-            }
-
-            auto upwindTerm = [](const auto& volVars) { return volVars.density() * volVars.enthalpy(); };
-            using HeatConductionType = typename GET_PROP_TYPE(TypeTag, HeatConductionType);
-
-            flux[Indices::energyBalanceIdx] = FluxVariables::advectiveFluxForCellCenter(elemVolVars, elemFaceVars, scvf, upwindTerm, isOutflow);
-            flux[Indices::energyBalanceIdx] += HeatConductionType::diffusiveFluxForCellCenter(problem, element, fvGeometry, elemVolVars, scvf);
-
-        });
+        computeFluxForCellCenterNonIsothermal_(std::integral_constant<bool, GET_PROP_VALUE(TypeTag, EnableEnergyBalance)>(),
+                                               problem, element, fvGeometry, elemVolVars, elemFaceVars, scvf, elemFluxVarsCache, flux);
 
         return flux;
     }
@@ -165,12 +146,8 @@ public:
         CellCenterPrimaryVariables storage;
         storage[Indices::massBalanceIdx] = volVars.density();
 
-        // add energy storage for non-isothermal models
-        Dune::Hybrid::ifElse(std::integral_constant<bool, GET_PROP_VALUE(TypeTag, EnableEnergyBalance) >(),
-        [&](auto IF)
-        {
-            storage[Indices::energyBalanceIdx] = volVars.density() * volVars.internalEnergy();
-        });
+        computeStorageForCellCenterNonIsothermal_(std::integral_constant<bool, GET_PROP_VALUE(TypeTag, EnableEnergyBalance) >(),
+                                                  problem, scv, volVars, storage);
 
         return storage;
     }
@@ -344,6 +321,51 @@ protected:
         }
     }
 
+    //! Evaluate energy fluxes entering or leaving the cell center control volume for non isothermal models
+    void computeFluxForCellCenterNonIsothermal_(std::true_type,
+                                                const Problem& problem,
+                                                const Element &element,
+                                                const FVElementGeometry& fvGeometry,
+                                                const ElementVolumeVariables& elemVolVars,
+                                                const ElementFaceVariables& elemFaceVars,
+                                                const SubControlVolumeFace &scvf,
+                                                const ElementFluxVariablesCache& elemFluxVarsCache,
+                                                CellCenterPrimaryVariables& flux) const
+    {
+        // if we are on an inflow/outflow boundary, use the volVars of the element itself
+        // TODO: catch neumann and outflow in localResidual's evalBoundary_()
+        bool isOutflow = false;
+        if(scvf.boundary())
+        {
+            const auto bcTypes = problem.boundaryTypesAtPos(scvf.center());
+                if(bcTypes.isOutflow(Indices::energyBalanceIdx))
+                    isOutflow = true;
+        }
+
+        auto upwindTerm = [](const auto& volVars) { return volVars.density() * volVars.enthalpy(); };
+        using HeatConductionType = typename GET_PROP_TYPE(TypeTag, HeatConductionType);
+
+        flux[Indices::energyBalanceIdx] = FluxVariables::advectiveFluxForCellCenter(elemVolVars, elemFaceVars, scvf, upwindTerm, isOutflow);
+        flux[Indices::energyBalanceIdx] += HeatConductionType::diffusiveFluxForCellCenter(problem, element, fvGeometry, elemVolVars, scvf);
+    }
+
+    //! Evaluate energy fluxes entering or leaving the cell center control volume for non isothermal models
+    template <typename... Args>
+    void computeFluxForCellCenterNonIsothermal_(std::false_type, Args&&... args) const {}
+
+    //! Evaluate energy storage for non isothermal models
+    void computeStorageForCellCenterNonIsothermal_(std::true_type,
+                                                   const Problem& problem,
+                                                   const SubControlVolume& scv,
+                                                   const VolumeVariables& volVars,
+                                                   CellCenterPrimaryVariables& storage) const
+    {
+        storage[Indices::energyBalanceIdx] = volVars.density() * volVars.internalEnergy();
+    }
+
+    //! Evaluate energy storage for isothermal models
+    template <typename... Args>
+    void computeStorageForCellCenterNonIsothermal_(std::false_type, Args&&... args) const {}
 
 private:
 

dumux/freeflow/navierstokesnc/staggered/localresidual.hh

@@ -102,12 +102,8 @@ public:
         if(replaceCompEqIdx < numComponents)
             storage[replaceCompEqIdx] = density;
 
-        // add energy storage for non-isothermal models
-        Dune::Hybrid::ifElse(std::integral_constant<bool, GET_PROP_VALUE(TypeTag, EnableEnergyBalance) >(),
-        [&](auto IF)
-        {
-            storage[Indices::energyBalanceIdx] = volVars.density() * volVars.internalEnergy();
-        });
+        this->computeStorageForCellCenterNonIsothermal_(std::integral_constant<bool, GET_PROP_VALUE(TypeTag, EnableEnergyBalance) >(),
+                                                        problem, scv, volVars, storage);
 
         return storage;
     }