Error for unexpected `const`

[trelau]

Get a parsing error for:

template<class T, int N>
T BVH_Tree<T, N, BVH_BinaryTree>::EstimateSAH() const
{
  T aSAH = static_cast<T> (0.0);
  BVH::EstimateSAH<T, N> (this, 0, static_cast<T> (1.0), aSAH);
  return aSAH;
}