[bugfix][staggered] true_type/false_type have to be instantiated (with {})...

[bugfix][staggered] true_type/false_type have to be instantiated (with {}) before calling the ()-operator

(cherry picked from commit 86501364)

dumux/discretization/staggered/freeflow/elementvolumevariables.hh

@@ -85,7 +85,7 @@ public:
 
     //! Binding of an element, prepares the volume variables within the element stencil
     //! called by the local jacobian to prepare element assembly. Specialization callable with MultiTypeBlockVector.
-    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<isMultiTypeBlockVector<SolutionVector>::value, int> = 0>
+    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<isMultiTypeBlockVector<SolutionVector>{}(), int> = 0>
     void bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
               const FVElementGeometry& fvGeometry,
               const SolutionVector& sol)
@@ -96,7 +96,7 @@ public:
 
     //! Binding of an element, prepares the volume variables within the element stencil
     //! called by the local jacobian to prepare element assembly
-    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<!isMultiTypeBlockVector<SolutionVector>::value, int> = 0>
+    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<!isMultiTypeBlockVector<SolutionVector>{}(), int> = 0>
     void bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
               const FVElementGeometry& fvGeometry,
               const SolutionVector& sol)
@@ -190,7 +190,7 @@ public:
 
     //! Binding of an element, prepares the volume variables within the element stencil
     //! called by the local jacobian to prepare element assembly. Specialization callable with MultiTypeBlockVector.
-    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<isMultiTypeBlockVector<SolutionVector>::value, int> = 0>
+    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<isMultiTypeBlockVector<SolutionVector>{}(), int> = 0>
     void bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
               const FVElementGeometry& fvGeometry,
               const SolutionVector& sol)
@@ -201,7 +201,7 @@ public:
 
     //! Binding of an element, prepares the volume variables within the element stencil
     //! called by the local jacobian to prepare element assembly
-    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<!isMultiTypeBlockVector<SolutionVector>::value, int> = 0>
+    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<!isMultiTypeBlockVector<SolutionVector>{}(), int> = 0>
     void bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
               const FVElementGeometry& fvGeometry,
               const SolutionVector& sol)
@@ -270,7 +270,7 @@ public:
 
     //! Binding of an element, prepares the volume variables within the element stencil
     //! called by the local jacobian to prepare element assembly. Specialization callable with MultiTypeBlockVector.
-    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<isMultiTypeBlockVector<SolutionVector>::value, int> = 0>
+    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<isMultiTypeBlockVector<SolutionVector>{}(), int> = 0>
     void bindElement(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                      const FVElementGeometry& fvGeometry,
                      const SolutionVector& sol)
@@ -281,7 +281,7 @@ public:
 
     //! Binding of an element, prepares only the volume variables of the element.
     //! Specialization for Staggered models
-    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<!isMultiTypeBlockVector<SolutionVector>::value, int> = 0>
+    template<class FVElementGeometry, class SolutionVector, typename std::enable_if_t<!isMultiTypeBlockVector<SolutionVector>{}(), int> = 0>
     void bindElement(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                      const FVElementGeometry& fvGeometry,
                      const SolutionVector& sol)