Starting to hack with boost libraries I found myself more and more stumbling across a big brick of C++ language, i.e. SFINAE works on types only, not on expressions. If an expression is ill formed there's no SFINAE around that will avoid you a barfing compiler. Looking at C++0x I failed to see a future improvement in that direction, also 'concepts' that will be quite new, apart from helping in decoding error messages (and this is a BIG help I would add), does not immediately seem to extend the language in that direction. For what I have understood 'refinements' are more or less similar to tag dispatching so does not seem to open completely new gates (of course this is just a first look opinion, it means that is not immediately visible to me how to use concepts to add to what you already can do using a more verbose approach, not that for sure it does not exist a way). I would like to ask you if someone has never dreamed of something like try well_formed { .... your code here... } catch { .... fall back code in case former is not compilable... }; I would think this would be an extension that greatly will open new gates to C++. Just to be clear, I'm not advocating to introduce something like the above, just to ask if a discussion around the above lines have never occurred in the C++ community. Thanks Marco