Doug Gregor wrote:
> Now, we're saying that any expressions are valid in
> sizeof, decltype, and constant expressions. If those
> expressions fail to type-check during substitution, it
> will be a SFINAE case.
Just to be sure we're not talking at cross purposes, can I
check that the current thinking on DR 339 is that type
traits such as the following should be legal (and do the
obvious thing):
template <class T>
class is_default_constructible {
template <int> struct helper {};
typedef char no; typedef char yes[2];
static no fn(...);
static yes fn( helper<sizeof(new T)>* );
public:
static const bool value = sizeof(fn(0)) == sizeof(yes);
};
If so, that's excellent news.
Richard Smith
