diff --git a/dune/matrix-vector/genericvectortools.hh b/dune/matrix-vector/genericvectortools.hh index 9c15e8a4aa5664085ecf37c5180da3f42716334a..ed8ac89dc1ad3a52f2859f866dae02637aa08506 100644 --- a/dune/matrix-vector/genericvectortools.hh +++ b/dune/matrix-vector/genericvectortools.hh @@ -183,18 +183,20 @@ protected: /// Note: We use PriorityTags to enforce trial order w.r.t. failure fallback. /// Additionally we use it to circumvent ambiguous overloading. /// Call subSizeProvider without PriorityTag via the priority tag forward helper for standard behaviour. + /// We use AlwaysTrue to silence errors about enable_if not providing a type when it does not depend + /// on the function template parameter. // ... from a sparse/dynamic matrix - template <class SizeProviderRow, typename = std::enable_if_t<isMatrix<Vector>() and not isTupleOrDerived<Vector>()>> + template <class SizeProviderRow, typename = std::enable_if_t<isMatrix<Vector>() and not isTupleOrDerived<Vector>() and AlwaysTrue<SizeProviderRow>::value>> static decltype(auto) subSizeProvider(SizeProviderRow&& row, PriorityTag<21>) { return *row.begin(); } // .. from a tuple like/static matrix - template <class SizeProviderRow, typename = std::enable_if_t<isMatrix<Vector>() and isTupleOrDerived<Vector>()>> + template <class SizeProviderRow, typename = std::enable_if_t<isMatrix<Vector>() and isTupleOrDerived<Vector>() and AlwaysTrue<SizeProviderRow>::value>> static decltype(auto) subSizeProvider(SizeProviderRow&& row, PriorityTag<20>) { return row[Indices::_0]; } // ... from a vector - template <class SizeProviderRow, typename = std::enable_if_t<isVector<Vector>()>> + template <class SizeProviderRow, typename = std::enable_if_t<isVector<Vector>() and AlwaysTrue<SizeProviderRow>::value>> static decltype(auto) subSizeProvider(SizeProviderRow&& row, PriorityTag<10>) { return row; }