SFINAE up ProviderBindings with NewBindings.
SFINAE up ProviderBindings with NewBindings.

The type condition for detecting providers is sub-par: we look for the Iface typedef.  Ideally we would look for the single get method.  While I'm at it, however, Provider should be a concept and not a base class at all.

phs/sauce,phs/sauce,phs/sauce,phs/sauce