Add error message for VariableBlockVector<bool>

dune/istl/vbvector.hh

@@ -54,6 +54,9 @@ namespace Dune {
     // data-structure holding the windows (but not the actual data)
     using VectorWindows = std::vector<window_type, typename std::allocator_traits<A>::template rebind_alloc<window_type>>;
 
+    // block type bool is not supported since std::vector<bool> is used for storage
+    static_assert(not std::is_same_v<B,bool>, "Block type 'bool' not supported by VariableBlockVector.");
+
   public:
 
     //===== type definitions and constants