Substitution failure is not an error: Difference between revisions

Revision as of 15:27, 21 September 2010

Revision as of 00:26, 25 November 2010

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Here, attempting to use a non-class type in a qualified name (<code>T::Typetype</code>) results in a deduction failure for <code>f<int></code> because <code>int</code> has no nested type named <code>Typetype</code>, but the program is well-formed because a valid function remains in the set of candidate functions.

Although SFINAE was introduced to avoid creating ill-formed programs when unrelated template declarations were visible (e.g., through the inclusion of a header file), many developers found the behavior useful for compile-time introspection. Specifically, it allows a template to determine certain properties of its template arguments at instantiation time.