added type promotions for sum combinations of DiagonalMatrix<K,n> and FieldMatrix<K,n,n>

[[Imported from SVN: r5475]]

dune/solvers/common/staticmatrixtools.hh

@@ -24,6 +24,18 @@ class StaticMatrix
             typedef Matrix Type;
         };
 
+        template<typename FieldType, int n>
+        struct Promote<Dune::FieldMatrix<FieldType,n,n>, Dune::DiagonalMatrix<FieldType,n> >
+        {
+            typedef Dune::FieldMatrix<FieldType,n,n> Type;
+        };
+
+        template<typename FieldType, int n>
+        struct Promote<Dune::DiagonalMatrix<FieldType,n>, Dune::FieldMatrix<FieldType,n,n> >
+        {
+            typedef Dune::FieldMatrix<FieldType,n,n> Type;
+        };
+
         template<typename FieldType, int n>
         struct Promote<Dune::DiagonalMatrix<FieldType,n>, Dune::ScaledIdentityMatrix<FieldType,n> >
         {