Re: Does SFINAE apply to non-template functions?

=?iso-8859-1?q?Daniel_Kr=FCgler?= <>
Sun, 16 Sep 2007 16:25:23 CST
On 13 Sep., 18:49, Marian Ciobanu <> wrote:

Until recently I was convinced that SFINAE only applies to template
functions, to remove template functions that have an error in their
signature from a list of possible candidates for a call. The errors
considered are limited to "missing type", "nonsensical type" and
perhaps others, but don't include things like "negative-size arrays".

I had some posts in another thread, where I've constantly been told
that SFINAE also applies to non-template functions that are member
of a template class.

The standard does not use the notion of SFINAE, but what
"function-SFINAE"[1] takes advantage of is limited to function
templates and one requirement for a working SFINAE-based overload
selection is that at least one member exists in the viable set.
The mainly relevant section is [temp.deduct]/2 and this always
talks about function templates. I'm not aware of other (non-
template-) related parts of the standard which could be interpreted
as SFINAE-capable.

To increase the chances of my question being understood: to me the
member function "f" below is "non-template", while "g" is a "template

template <typename T>
struct A
     int f();
     template <typename U> int g(U);


f is a member function of the class template A, g is a member
function template of the class template A.

Unfortunately the standard itself is somewhat inprecise here.
Both the official standard 14882:2003(E) as well as the most
recent draft N2369 provide the following example in

"template<class T> class Array {
  T* v;
  int sz;
  explicit Array(int);
  T& operator[](int);
  T& elem(int i) { return v[i]; }
  // ...

declares three function templates.[..]"

This is an obvious editorial issue.

Greetings from Bremen,

Daniel Kr?gler

[1]: SFINAE can also occur during selection of class template

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