http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51424
--- Comment #1 from Andrew Schepler <aschepler at gmail dot com> 2013-04-09 19:38:15 UTC --- The diagnostic is easy in the direct case of delegating to the same constructor, but difficult in the indirect case of multiple delegating constructors. (The condition might still be detectable if enough constructors can be inlined.) This difficulty is presumably why the Standard specifies "no diagnostic required". But yes, it seems like a good idea to support a warning for the easy case.
